CA1322786C - Mobile communications antenna - Google Patents
Mobile communications antennaInfo
- Publication number
- CA1322786C CA1322786C CA000601606A CA601606A CA1322786C CA 1322786 C CA1322786 C CA 1322786C CA 000601606 A CA000601606 A CA 000601606A CA 601606 A CA601606 A CA 601606A CA 1322786 C CA1322786 C CA 1322786C
- Authority
- CA
- Canada
- Prior art keywords
- radiating
- sections
- section
- impedance
- antenna assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/27—Adaptation for use in or on movable bodies
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
- H01Q21/08—Arrays of individually energised antenna units similarly polarised and spaced apart the units being spaced along or adjacent to a rectilinear path
- H01Q21/10—Collinear arrangements of substantially straight elongated conductive units
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
- H01Q1/1271—Supports; Mounting means for mounting on windscreens
- H01Q1/1285—Supports; Mounting means for mounting on windscreens with capacitive feeding through the windscreen
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/27—Adaptation for use in or on movable bodies
- H01Q1/32—Adaptation for use in or on road or rail vehicles
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q11/00—Electrically-long antennas having dimensions more than twice the shortest operating wavelength and consisting of conductive active radiating elements
- H01Q11/12—Resonant antennas
- H01Q11/14—Resonant antennas with parts bent, folded, shaped or screened or with phasing impedances, to obtain desired phase relation of radiation from selected sections of the antenna or to obtain desired polarisation effect
- H01Q11/16—Resonant antennas with parts bent, folded, shaped or screened or with phasing impedances, to obtain desired phase relation of radiation from selected sections of the antenna or to obtain desired polarisation effect in which the selected sections are collinear
Abstract
ABSTRACT OF THE DISCLOSURE
A mobile communications antenna assembly for use over a selected band of frequencies in the VHF and UHF ranges, has, a radiating element with first, second and third, collinear radiating sections. The first and second sections each have an electrical length substantially equal to five-eighths wavelength over the selected band, while the third section has an electrical length substantially equal to one-quarter wavelength. Phase inductor elements connect the sections for maintaining a predetermined phase relationship between electrical signals radiating from the sections. The third section further has a radiating surface area that is substantially greater than the radiating surface areas of the first and second sections. The base end of the third section is mounted to be elevated above the surface. The transmission line is connected to impedance matching means at a point where impedance of the two is substantially equal.
A mobile communications antenna assembly for use over a selected band of frequencies in the VHF and UHF ranges, has, a radiating element with first, second and third, collinear radiating sections. The first and second sections each have an electrical length substantially equal to five-eighths wavelength over the selected band, while the third section has an electrical length substantially equal to one-quarter wavelength. Phase inductor elements connect the sections for maintaining a predetermined phase relationship between electrical signals radiating from the sections. The third section further has a radiating surface area that is substantially greater than the radiating surface areas of the first and second sections. The base end of the third section is mounted to be elevated above the surface. The transmission line is connected to impedance matching means at a point where impedance of the two is substantially equal.
Description
~OE~II~ CO~INICATIONS ANT~N~ 13 ~ ~ 7 $ ~3 BACRGRO~ O~ ~rION
1. Field o~ the Inv~ntion This invention relates in general to communications antennas, and, ~ore particularly, to a ~obile communi~ations antenna for use over a selected band of frequencies in the VHF and UHF frequency bands.
1. Field o~ the Inv~ntion This invention relates in general to communications antennas, and, ~ore particularly, to a ~obile communi~ations antenna for use over a selected band of frequencies in the VHF and UHF frequency bands.
2. Description of ~he Related ~rt It has long been known that an antenna ~an be mounted on a pane of glass and that the dielectric properties of the glass can be advantageously used to capacitively couple the antenna to radio apparatus when the~y are on opposite sides of the glass.
The first teachings of mounting such an antenna on a non conductive surface of a vehicl~! can be found in such patents as U.S. Patent No. 1,715,952 to J.A. Rostron.
Ros~ron taught a window mounted antenna that was capacitively coupled, through the window, to a transmitting or rsceiving apparatus.
With the popularity of radios in automobiles, several early inventors patented antennas which were mounted on vehicular windows or windshiel~s. While most of these early referances were directed towards antennas suitable for ~ ~ ~ f~ ~ J
receiving signals, it was the recent popularity of first the Citizen's Band radios and, more recen-tly, the cellular telephone, as a car accessory, that caused the prior art to expand in the area of mobile communications antennas suitable ~or mounting on non~conductive areas of a vehicle that could both transmit as well as receive signals.
The cellular telephone system generally employs for each subscriber to the system, a transceiver operating in the VHF or UHF frequency bands, eOg., for the UHF bands approximately 820 to 895 MHz.
At these frequencies, one wavelength can be approximately one foot, thereby allowing great latitude in the design of the antenna system.
Until recently, however, there have been generally only two basic designs of mobile communica~ions antennas for mounting on a non-conductive surface of a vehicle being used.
The most popular of these two designs is a two element antenna having its radiating elements essentially collinear and separated by an open air helical inductor coil. An example of such an antenna is disclosed in United States Patent No. 4,794,319.
This prior art design yields about 3 dB gain for the signal.
The second major design in current use has two radiating elements with an electrical length equal to substantially one-quarter wavelength and electrically connected into a vertical dipole configuration.
Since any antenna system that involved transmission of its signal through a non-conducting surface involves loss of signal strength and an increase in the standing wave ratio on the transmission line, a design was sought that would yi~ld a ~ 3 ~
higher signal gain over existing designs, while s~ill minimizing both the signal loss and the standing wave ratio on the transmission line.
The present invention meets these requirements for a higher signal gain over existing design~ while still minimizing both the signal loss due to the transmission of the signal through the non-conductive mounting surface and lessening the standing wave ratio, generally ~ound for such designs, on the transmission line.
SUMMARY OF 5~E INV%~TION
Due to the high ~requencies and consequently short wavelengths of the band allotted the cellular telephone system, the present invention can be used as a cellular telephone communications antenna in an antenna assembly having a vertical radiating element that would have made the invention impractical for use at lower ~re~uencies. This is because lower operating ~re~uencies would have required a total mast length of the verti~al radiating element to be so great as to be impracti~-~al to withstand the wind loading and other stressing forces exerted upon a glasæ-~ounted vehical antenna.
The design of the present invention presents an antenna assembly having generally an omni-directional radiation pattern and a gain of about 4.2 dB (under ideal conditions), but, taking into account losses encountered due to the ~3-~ 3 ~
impedance of the glass through which the signal passes whenthe assembly is moun~ed on a vehicle's window, the transmission line loss, and standing waves caused by improper installation, ~he practical gain oP the assembly is in the order of 3.5 dB.
For comparison, curr~nt prior axt antennas si~ilarly mounted on a vehicle have a practical gain of about 2.0 to 2.2 dB based upon actual measurements.
one of the inherent problems o~ multi-sectional, radiating vertical array antennas, is the narrow bandwidth, and low Q-~actor, of the assembly. Since the bandwidth of ` `
the cellular telephone band over which the present invention would find its greatest use is about 40 MHz, a method of increasing the bandwidth o~ the antenna had to be devised.
Accordingly, to increase the bandwidth of an antenna embodying the invention, the radiating surface area of the lower radiating section of the antenna array was increased.
This improvement is noticeable at high frequencies such as VHF and UHF freguencies, where the radiating current tends to flow on the surface of the radiating element. Increasiny the radiating surface area of the lower radiating section also improves the Q-factor of the antenna ass2mb1y and increases the bandwidth of ~he overall radiating asse~bly. ~y proper sel~ction of the radiating sur~ace area of ~he low~r radiating section, the bandwidth of the entire assembly can be extended to accommodate the entire 40 MHz of the cellular telephone band whil~ still maintaining a fairly short overall length for the radiating element of thQ antenna assembly.
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. . ~ ' .
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Another advantage of th~ present invention is that anantenna embodying the present invention would prefsrably use a power feed connection to the transmission line, that is, a combination of both current and voltage. As such, it becomes necessary that at least a portion of the radiating element of the antenna assembly rises above its surroundings to provide an unobstructed radiation path ~or the radiated electrical signal. In a vehicle mounting situation, this would r~guire that a portion of the radiating element rise above the vehicla's highest body portion, which is normally the roof.
The feed point of an antenna assembly embodying the present invention would also preferably be elevated above ths vehicle's body upon which it is mo~nted so that ~ost o~ the energy of th,e antenna will be radiated above the vehicle's roofline.
In summary then, a preferred embodiment o the present invention in a mobile communications antenna assembly for use over a selected band of frequencies in the VHF and U~F
ranges, would include a radiating element having first, second and third, collinear radiating sections. The first and econd collinear radiating sections each have an electrical length substantially e~lal to ~ive-eighths~
wavelength, while the third radiating section has an electrical length subst~ntially equal to one-guarter wavelength. Each section is electrically connected to its adjacent section by phas~ inductor elements for maintaining a predetermined phase relationship between electrical signals radiating from the sections. The third collinear radiating $--~ 3 ~
section further has a radiating surface area that is substantially greater than the racliating surface areas of the first and second radiating sections. A base me~ber i5 electrically connected to and disposed adjacent a base end of the third radiating section of the radiating element for mounting the radiating element to a surface, so that the base end of the third radiating section is elevated above the surface. Impedance matching circuitry selectively tunable to the nominal resonant frequency of the radiatiny element is electrically connected thereto. A connector is provided for co~necting a transmission line to the impedance matching circuitry at a point where the impedance of the impedance matching circuitry is substantially equal to the impedance of the transmission line.
The novel ~eatures of construction and operation of the invention will ba more claarly apparent during the course of the ~ollowing description, referenc:e being had to the accompanying drawings wherein ha~ been illustrated a pre~erred ~orm of the d~vice of the invention and wherein like characters o~ reference designate like parts throughout the drawings.
BRIEF D~5CRIPTION OF T~E ~RA~NGS
.
FIG. 1 is a front view of a preferr@d embodiment of a glass mounted antenna ~or us~ on vehicles embodying the present invention;
~6-.' ' ~ ' ' , , ' ~ ~3 f;~
FIG. 2 is a side view of he antenna assembly of PIG. 1;
FIG. 3 is an idealized schematic diagram of the l~ircuit of the ant ~a assembly of FIG. 1;
FIG. 4 is an idealized schematic diagram of an alternative circuit ~or the antenna a~;sembly o~ FIG. 1:
FIG. 5 is an idealized sch~matic diagram of a circuit for the antenna assembly of the present inv~ntion similar to that: o~ FIG. 3 wherein the assembly does not pass its signal through an intervening glass medium; and, FIG. 6 is an idealized schematic diagram o~ a ~irsuit for ths ant~nna assembly o~ the present invent~ on similar to that of FIG. 4 wherein the as~;embly does not pass its signal through an intervening glass medium.
DESCRl:PTION OF TEg PR13E~RED l~DD~S
Turning ~irst to FIG5. 1 and 2, there is shown a glass mounted antenna assembly 10 that is constructed in accordance with the present invention and useful as a mobile communications antenna assembly capable of being mounted on a vehicle and adapted ~or use over a selected band o~
frequencies in the VHF and UHF ranges.
In assembly 10 a primary ante~na radiating element 12 is mounted on the exterior of a glass 14 and coupling and tuning circuit elements 16 are mounted on the interior sur~ace of the glass 14. It is understood that although the invention is shown as b~ing ~ount~d on opposite sides of a glass pane, $ $
the antenna would function equally well i~ the material separating the elements were any other ~ielectric such as a plastic panel. Likewise, a~ will be de~cri~ed below and shown in FIGS. 5 and 5, the invention ran be embod.ied in an antenna assembly that is capable of being mounted on a single side of a mounting surfaca that is either non-conductive or, with minor modi~ication, conductive so as to provide a ground plane for the radiating elements of the antenna system.
In this first preferred emhodiment, it is seen that the invention is ideally suited for use with motor vehicles and can be used on the windshield, the back window, any glass or plastic panel, or any location that provides optimum operation. In this ~irst preferred embodiment, only the primary radiating element 12 is on the exterior o~ the vehicle. The remainin~ elements of assembly 10 are in the interior of the vehicle, where they can be directly connected to a transceiver through conventional transmissicn line means such as coaxial cable.
A~ seen in FIG. 1, the primary radiating element 12 contains first, ~econd and third, c:ollinear radiating sec~ions, 1~, 20 and 22, respe~tively.
Fir~t and seccnd collinear radiating sections 18 and 20, each have an electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band. Sections 18 and 20 are separated and electrically connected to one another by a first phasing inductance coil 24. Coil 24 is adapted to maintain a predetarmined phase relationship between electrical siynals ~ 3,~
radiating from the first and second sections 1~, 20, and is preferably a helical open air coil formed from the primary radiating element 12 itself.
First and second collinear radiating sections 18 and 20 may also have differing electrical lengths, such as both, or even one of the radiating sections being substantially equal to one-half of the center wavelength o~ the selected frequency band.
These radiating sections may, with appropri~te modification of the first phasing coil 24 to maintain the desired pre~etermined phase relationship between electrical signals radiating from the two sections, take on any electrical length between one-half to five-eighths of the center wavelength of the selected frequency band.
The third collinear radiating section 22 has an electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band and is electrically connected at one end 2~ to second collinear radiating section 20 by a second phasing inductance coil 28. Coil 28 is also adapted to maintain a predetermined phase relationship between electrical signals radiating from the second and third sections, 20 and 22 respectively. Coil 2~ is also preferably protected by mounting and covering it with a portion 29 of the second radiating section 20. In this latter construction, third section 22 can be covered with a layer 31 of insulating material so as to prevent shorting of the electrical signal between the second and third sections, thus p~oviding for both a saEer and more aesthetically pleasing final product capable of withstanding both environmental forces and mechanical stresses of vehicle movement.
_g _ Third section 22 has a second opposite base end 30 that is adapted to mate with a mounting assembly better described belowO
Third collinear radiating section 22 further has a radiating surface 32 with an area that is substantially greater than the radiating surface areas of each of the first and second radiating sections 18 and 20.
As shown in the figures, one preferred way of providing -9a-third collinear radiating section with an enlarged radiating surface 32, is to construct section 22 with a diameter substantially greater than the diameter of each of the first and second radiating sections 18 and 20. In this manner the radiating surface ar a 32 of third collinear radiating section 22 will be greater in comparison to ~he radiating sur~ace areas of the first and second sections.
A base asse~bly 34, is connected to the base end 30 of the third radiating sectîon 22 to provide a mounting support for the radiating element 12. Base 34 preferably is user adjustable to permit radiating element 12 to be maintained generally vertical to the surface oYer which the ~ehicle is travelling. This user adjustment may be accomplished by having a th~ radiating element pivotally connected to base 34 and held in desired position by a set screw 48.
To permit some versatility and limited tuning adjustment by the user within the designed freguency band of the antenna assembly, the primary radiating element 12 can mo~e, at base end 30 of its third radiating section, with respect to its connection to base assembly 34 by means of a set screw 56 that can be used to vary the exposed leMgth of the radiating element 12 and o lock it at the optimum length.
Base 34 has an electrically conductive plate member 36 attached thereto having a fixed surface area. Ne~ber 36 is elec~rically connected to and disposed adjacent base end 30 of third radiating section 22, for mounting radiating element 12 to a first, exterior side 14 of a non-conducti~e body por~ion, here shown to be th~ exterior portion 14 of a glass window of a vehicle. ~3~ ~$~' In this manner, the base end 30 of third radiating section 22 is elevated above ~he surface of the glass window and, accordingly, of the surrounding body portion of the vehicle itself.
A second electrically conductive coupling member 38 is mounted on a second, opposite side 40 of the non-conductive body portion (glass window) in substantial juxtaposition with first electrically conductive member 36 and defines with non-conductive body portion (glass window) intermediAte these two members 36 and 38, a coupling capacitor having a fixed plate surface area at the base end 30 of the third radiating section and located adjacent a current node thereof.
Impedance matching circuitry ~2, whi~h may include a tuned circuit, s~ch as a s~ries tuned circuit, that is selectively tunable to the nominal re~onant frequency of the radiating element, is electrically connected to ~econd electrically conductive coupling member 38 in the immediate proximity thereof to resonate in conjunction with radiating element 12. Impedance matching circuitry 42 preferably has an impedance which varies between a first impedance, measured at the connection to the second electrically conductive coupling member 38, ~ubstantially eqyal to the impedance at the base end 30 of third radiating section 22, and a second impedance at least several orders of magnitude less than the first impedance.
In a preferred embodiment of the invention, impedance matching circuitry 42 would include a user adjustable ~3~.~7 l`3.i capacitance member (as shown in FI~S. 3 through 6), 50 that minor adjustments can be made in the ~ield to ac~o~modate the antenna assembly to changes in its operating environment.
Such changes can be occasioned by different ~hicknesse5 in the glass window through which the sign~l is transmitted or by a change in capacitance or impedance c used by a build up of pollutants on the antenna asse~bly itsel~.
~ coaxial fitting 44 connects a transmission line (not shown) to impedance matching circuitry 42 at a point where the impedance is substantially equal to the impedance of the transmission line.
The transmission line is preferably a coaxial cable that connects antenna assembly 10 and a radio communications unit (not shown). The transmission line should have an impedance that is orders of magnitude less than the impedance of the antenna assemkly 10 at base end 30 of the third radiating section thereof.
Extendin~ at right angles to a line parallel to the axis of the primary radiating element 12, are first and second stub antennas 50 and 52 respectively. Each preferably has an efective wavelength of one-quar~er of a wavelenyth. The stub antennas 50, 52, are mounted on an i~terior base mem~er 54 which is adapted to be adhered to the inner surface 40 of the glass window.
The interior and exterior mounted coupling members 36 and 38, are designed to be matched in alignment when mounted sinc~ each is intended to be one plate of a capacitor which uses the glass window itself ae the dielectric element.
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Turning next to FIG. 3, there is shown a praferredcircuit for use with the antenna of the present invention.
As shown, the primary antenna radiating element 12 is shown directly connected to one plate 100 of a capacitor 102, the other plate 104 of which is connected through a tuning circuit 106 to the ~ign~l lead 108 of a coaxial cable 110 that is coupled to a transceiver (not shown). ~he glass 112 to which the capacitor plates 100, 104 are adherad, is the diel2ctric for the capacitor 102. An adjustable tuning capacitor 1~4 is serially connected to the ~inside~ plate 104, and ~ay, for circuit purposes, be considered a ~lu~pedn capacitive element.
In the preferred embodiment, a first inductor 116 serially couples the capacitors 10~, 114 to the signal lead 108. A second inductor 118 couples the signal lead 108 to the ground or shield 120 of the coaxial cable 110~ The stub antennas 122, 12~ are connected to th~ grounded shield 120, as well.
In use, the circuit ~s connected to a transcaiver and a standing wave ratio m~ter is used in conjunc~ion wi~h the adjustabla tuning capacitor 114 to achieve peak p~rformance in the 820 to 895 ~z frequency band which has been alloted to cellular mobile telephone system use. The total capacitance (of the dielectric panel and the adjusta~le tuning capacitor 114) functions to ~cancel~ the inductive reactance of the antenna.
The inductor~ 116, 118 are selected tc match the impedance of the antenna circuit to the coaxial cable 110 ~ 3 ,J ~
Accordin~ly, energy can be transferred through the glass orother dielectric panel with a minimum of energy loss.
Because the antenna circuit is designed to operate in the power (current and voltage) feed mode, the grounded stub antennas 122, 124 act as a ~mirror image~ (ground plane) of the primary antenna radiating element 12. In the ~bsence of the grounded stub antennas, a reflection current would appear at the coaxial cable 110 and a good impedance match would be di~ficult, if not impossible to achieve.
FIG. 4 is an alternative circuit embodiment in which a second trimmer capacitor 126 is substituted for the second inductor 118 of FIG. 3. Other elements in FIG~ 4, similar to tho~e elements described above for FI~. 3, are shown as primed reference numerals corresponding to their unprimed counterparts in FIG. 3. With the circuit shown in FIG. 4, the optimum frequency range for which it is tuned tends to be quite sharp and narrow. Accordingly, it is not as satisfactory when dealin~ with a relatively broad frequency band such as the approximately 75 MHz bandwidth available in the cellular telephone band. ~owever, for those applications where the freguencies in use fall within a ~airly narrow band, the alternative embodiment should prove satisfactory.
T~rning next to FI~S. 5 and S, there is shown in schematic ~orm an alternative antenna system e~bodying the present invention generally employing stub antennas mounted on a single side of a non conductive body portion of a vehicle along with the principal antenna ~lement. In thi~
embodiment, only a single base element is employed which can be fastened to virtually any surface and does not require anext~rior and an interior mounted ant~nna ass~mbly.
In general, F~GS. 5 and ~ are similar tu FIGS. 3 and 4, respectively, and illustrate the ~eneral el~ctrical connections of an antenna assembly embodying the present invention adapted for mounting to a singl~ ~ide of a non-conductive body portisn of a vehicle. Similar parts retain the same reference numerals, the only difference being the absence of the capacitors 102, 102'.
Finally, it should be noted that if the antenna of the present invention is to be mounted on a body portion o~ a vehicle that i~ suitable as a reflective signal ground plane, then the stub antennas described above may be eliminated and the principal rad~ating element de~cribed above may be directly mounted to the desired location by any number of presently knawn mounting brackets.
The invention described above is, of course, susceptible to many variations, modifications and changes, all of which are within the skill of the art. It should be understood that all s~!ch variations, modi~ications and changes are within the spirik and scope of the invention and o~ the appended claims. SimilarlyO it will be understood that it is intended to cover all changes, modifications and variation~
of the example of the invention herein disclosed for the purpose of illustration which do not constitute departures from the ~pirit and scope of the invention~
The first teachings of mounting such an antenna on a non conductive surface of a vehicl~! can be found in such patents as U.S. Patent No. 1,715,952 to J.A. Rostron.
Ros~ron taught a window mounted antenna that was capacitively coupled, through the window, to a transmitting or rsceiving apparatus.
With the popularity of radios in automobiles, several early inventors patented antennas which were mounted on vehicular windows or windshiel~s. While most of these early referances were directed towards antennas suitable for ~ ~ ~ f~ ~ J
receiving signals, it was the recent popularity of first the Citizen's Band radios and, more recen-tly, the cellular telephone, as a car accessory, that caused the prior art to expand in the area of mobile communications antennas suitable ~or mounting on non~conductive areas of a vehicle that could both transmit as well as receive signals.
The cellular telephone system generally employs for each subscriber to the system, a transceiver operating in the VHF or UHF frequency bands, eOg., for the UHF bands approximately 820 to 895 MHz.
At these frequencies, one wavelength can be approximately one foot, thereby allowing great latitude in the design of the antenna system.
Until recently, however, there have been generally only two basic designs of mobile communica~ions antennas for mounting on a non-conductive surface of a vehicle being used.
The most popular of these two designs is a two element antenna having its radiating elements essentially collinear and separated by an open air helical inductor coil. An example of such an antenna is disclosed in United States Patent No. 4,794,319.
This prior art design yields about 3 dB gain for the signal.
The second major design in current use has two radiating elements with an electrical length equal to substantially one-quarter wavelength and electrically connected into a vertical dipole configuration.
Since any antenna system that involved transmission of its signal through a non-conducting surface involves loss of signal strength and an increase in the standing wave ratio on the transmission line, a design was sought that would yi~ld a ~ 3 ~
higher signal gain over existing designs, while s~ill minimizing both the signal loss and the standing wave ratio on the transmission line.
The present invention meets these requirements for a higher signal gain over existing design~ while still minimizing both the signal loss due to the transmission of the signal through the non-conductive mounting surface and lessening the standing wave ratio, generally ~ound for such designs, on the transmission line.
SUMMARY OF 5~E INV%~TION
Due to the high ~requencies and consequently short wavelengths of the band allotted the cellular telephone system, the present invention can be used as a cellular telephone communications antenna in an antenna assembly having a vertical radiating element that would have made the invention impractical for use at lower ~re~uencies. This is because lower operating ~re~uencies would have required a total mast length of the verti~al radiating element to be so great as to be impracti~-~al to withstand the wind loading and other stressing forces exerted upon a glasæ-~ounted vehical antenna.
The design of the present invention presents an antenna assembly having generally an omni-directional radiation pattern and a gain of about 4.2 dB (under ideal conditions), but, taking into account losses encountered due to the ~3-~ 3 ~
impedance of the glass through which the signal passes whenthe assembly is moun~ed on a vehicle's window, the transmission line loss, and standing waves caused by improper installation, ~he practical gain oP the assembly is in the order of 3.5 dB.
For comparison, curr~nt prior axt antennas si~ilarly mounted on a vehicle have a practical gain of about 2.0 to 2.2 dB based upon actual measurements.
one of the inherent problems o~ multi-sectional, radiating vertical array antennas, is the narrow bandwidth, and low Q-~actor, of the assembly. Since the bandwidth of ` `
the cellular telephone band over which the present invention would find its greatest use is about 40 MHz, a method of increasing the bandwidth o~ the antenna had to be devised.
Accordingly, to increase the bandwidth of an antenna embodying the invention, the radiating surface area of the lower radiating section of the antenna array was increased.
This improvement is noticeable at high frequencies such as VHF and UHF freguencies, where the radiating current tends to flow on the surface of the radiating element. Increasiny the radiating surface area of the lower radiating section also improves the Q-factor of the antenna ass2mb1y and increases the bandwidth of ~he overall radiating asse~bly. ~y proper sel~ction of the radiating sur~ace area of ~he low~r radiating section, the bandwidth of the entire assembly can be extended to accommodate the entire 40 MHz of the cellular telephone band whil~ still maintaining a fairly short overall length for the radiating element of thQ antenna assembly.
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~ , ' ' ' .
~ 3 ~
Another advantage of th~ present invention is that anantenna embodying the present invention would prefsrably use a power feed connection to the transmission line, that is, a combination of both current and voltage. As such, it becomes necessary that at least a portion of the radiating element of the antenna assembly rises above its surroundings to provide an unobstructed radiation path ~or the radiated electrical signal. In a vehicle mounting situation, this would r~guire that a portion of the radiating element rise above the vehicla's highest body portion, which is normally the roof.
The feed point of an antenna assembly embodying the present invention would also preferably be elevated above ths vehicle's body upon which it is mo~nted so that ~ost o~ the energy of th,e antenna will be radiated above the vehicle's roofline.
In summary then, a preferred embodiment o the present invention in a mobile communications antenna assembly for use over a selected band of frequencies in the VHF and U~F
ranges, would include a radiating element having first, second and third, collinear radiating sections. The first and econd collinear radiating sections each have an electrical length substantially e~lal to ~ive-eighths~
wavelength, while the third radiating section has an electrical length subst~ntially equal to one-guarter wavelength. Each section is electrically connected to its adjacent section by phas~ inductor elements for maintaining a predetermined phase relationship between electrical signals radiating from the sections. The third collinear radiating $--~ 3 ~
section further has a radiating surface area that is substantially greater than the racliating surface areas of the first and second radiating sections. A base me~ber i5 electrically connected to and disposed adjacent a base end of the third radiating section of the radiating element for mounting the radiating element to a surface, so that the base end of the third radiating section is elevated above the surface. Impedance matching circuitry selectively tunable to the nominal resonant frequency of the radiatiny element is electrically connected thereto. A connector is provided for co~necting a transmission line to the impedance matching circuitry at a point where the impedance of the impedance matching circuitry is substantially equal to the impedance of the transmission line.
The novel ~eatures of construction and operation of the invention will ba more claarly apparent during the course of the ~ollowing description, referenc:e being had to the accompanying drawings wherein ha~ been illustrated a pre~erred ~orm of the d~vice of the invention and wherein like characters o~ reference designate like parts throughout the drawings.
BRIEF D~5CRIPTION OF T~E ~RA~NGS
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FIG. 1 is a front view of a preferr@d embodiment of a glass mounted antenna ~or us~ on vehicles embodying the present invention;
~6-.' ' ~ ' ' , , ' ~ ~3 f;~
FIG. 2 is a side view of he antenna assembly of PIG. 1;
FIG. 3 is an idealized schematic diagram of the l~ircuit of the ant ~a assembly of FIG. 1;
FIG. 4 is an idealized schematic diagram of an alternative circuit ~or the antenna a~;sembly o~ FIG. 1:
FIG. 5 is an idealized sch~matic diagram of a circuit for the antenna assembly of the present inv~ntion similar to that: o~ FIG. 3 wherein the assembly does not pass its signal through an intervening glass medium; and, FIG. 6 is an idealized schematic diagram o~ a ~irsuit for ths ant~nna assembly o~ the present invent~ on similar to that of FIG. 4 wherein the as~;embly does not pass its signal through an intervening glass medium.
DESCRl:PTION OF TEg PR13E~RED l~DD~S
Turning ~irst to FIG5. 1 and 2, there is shown a glass mounted antenna assembly 10 that is constructed in accordance with the present invention and useful as a mobile communications antenna assembly capable of being mounted on a vehicle and adapted ~or use over a selected band o~
frequencies in the VHF and UHF ranges.
In assembly 10 a primary ante~na radiating element 12 is mounted on the exterior of a glass 14 and coupling and tuning circuit elements 16 are mounted on the interior sur~ace of the glass 14. It is understood that although the invention is shown as b~ing ~ount~d on opposite sides of a glass pane, $ $
the antenna would function equally well i~ the material separating the elements were any other ~ielectric such as a plastic panel. Likewise, a~ will be de~cri~ed below and shown in FIGS. 5 and 5, the invention ran be embod.ied in an antenna assembly that is capable of being mounted on a single side of a mounting surfaca that is either non-conductive or, with minor modi~ication, conductive so as to provide a ground plane for the radiating elements of the antenna system.
In this first preferred emhodiment, it is seen that the invention is ideally suited for use with motor vehicles and can be used on the windshield, the back window, any glass or plastic panel, or any location that provides optimum operation. In this ~irst preferred embodiment, only the primary radiating element 12 is on the exterior o~ the vehicle. The remainin~ elements of assembly 10 are in the interior of the vehicle, where they can be directly connected to a transceiver through conventional transmissicn line means such as coaxial cable.
A~ seen in FIG. 1, the primary radiating element 12 contains first, ~econd and third, c:ollinear radiating sec~ions, 1~, 20 and 22, respe~tively.
Fir~t and seccnd collinear radiating sections 18 and 20, each have an electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band. Sections 18 and 20 are separated and electrically connected to one another by a first phasing inductance coil 24. Coil 24 is adapted to maintain a predetarmined phase relationship between electrical siynals ~ 3,~
radiating from the first and second sections 1~, 20, and is preferably a helical open air coil formed from the primary radiating element 12 itself.
First and second collinear radiating sections 18 and 20 may also have differing electrical lengths, such as both, or even one of the radiating sections being substantially equal to one-half of the center wavelength o~ the selected frequency band.
These radiating sections may, with appropri~te modification of the first phasing coil 24 to maintain the desired pre~etermined phase relationship between electrical signals radiating from the two sections, take on any electrical length between one-half to five-eighths of the center wavelength of the selected frequency band.
The third collinear radiating section 22 has an electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band and is electrically connected at one end 2~ to second collinear radiating section 20 by a second phasing inductance coil 28. Coil 28 is also adapted to maintain a predetermined phase relationship between electrical signals radiating from the second and third sections, 20 and 22 respectively. Coil 2~ is also preferably protected by mounting and covering it with a portion 29 of the second radiating section 20. In this latter construction, third section 22 can be covered with a layer 31 of insulating material so as to prevent shorting of the electrical signal between the second and third sections, thus p~oviding for both a saEer and more aesthetically pleasing final product capable of withstanding both environmental forces and mechanical stresses of vehicle movement.
_g _ Third section 22 has a second opposite base end 30 that is adapted to mate with a mounting assembly better described belowO
Third collinear radiating section 22 further has a radiating surface 32 with an area that is substantially greater than the radiating surface areas of each of the first and second radiating sections 18 and 20.
As shown in the figures, one preferred way of providing -9a-third collinear radiating section with an enlarged radiating surface 32, is to construct section 22 with a diameter substantially greater than the diameter of each of the first and second radiating sections 18 and 20. In this manner the radiating surface ar a 32 of third collinear radiating section 22 will be greater in comparison to ~he radiating sur~ace areas of the first and second sections.
A base asse~bly 34, is connected to the base end 30 of the third radiating sectîon 22 to provide a mounting support for the radiating element 12. Base 34 preferably is user adjustable to permit radiating element 12 to be maintained generally vertical to the surface oYer which the ~ehicle is travelling. This user adjustment may be accomplished by having a th~ radiating element pivotally connected to base 34 and held in desired position by a set screw 48.
To permit some versatility and limited tuning adjustment by the user within the designed freguency band of the antenna assembly, the primary radiating element 12 can mo~e, at base end 30 of its third radiating section, with respect to its connection to base assembly 34 by means of a set screw 56 that can be used to vary the exposed leMgth of the radiating element 12 and o lock it at the optimum length.
Base 34 has an electrically conductive plate member 36 attached thereto having a fixed surface area. Ne~ber 36 is elec~rically connected to and disposed adjacent base end 30 of third radiating section 22, for mounting radiating element 12 to a first, exterior side 14 of a non-conducti~e body por~ion, here shown to be th~ exterior portion 14 of a glass window of a vehicle. ~3~ ~$~' In this manner, the base end 30 of third radiating section 22 is elevated above ~he surface of the glass window and, accordingly, of the surrounding body portion of the vehicle itself.
A second electrically conductive coupling member 38 is mounted on a second, opposite side 40 of the non-conductive body portion (glass window) in substantial juxtaposition with first electrically conductive member 36 and defines with non-conductive body portion (glass window) intermediAte these two members 36 and 38, a coupling capacitor having a fixed plate surface area at the base end 30 of the third radiating section and located adjacent a current node thereof.
Impedance matching circuitry ~2, whi~h may include a tuned circuit, s~ch as a s~ries tuned circuit, that is selectively tunable to the nominal re~onant frequency of the radiating element, is electrically connected to ~econd electrically conductive coupling member 38 in the immediate proximity thereof to resonate in conjunction with radiating element 12. Impedance matching circuitry 42 preferably has an impedance which varies between a first impedance, measured at the connection to the second electrically conductive coupling member 38, ~ubstantially eqyal to the impedance at the base end 30 of third radiating section 22, and a second impedance at least several orders of magnitude less than the first impedance.
In a preferred embodiment of the invention, impedance matching circuitry 42 would include a user adjustable ~3~.~7 l`3.i capacitance member (as shown in FI~S. 3 through 6), 50 that minor adjustments can be made in the ~ield to ac~o~modate the antenna assembly to changes in its operating environment.
Such changes can be occasioned by different ~hicknesse5 in the glass window through which the sign~l is transmitted or by a change in capacitance or impedance c used by a build up of pollutants on the antenna asse~bly itsel~.
~ coaxial fitting 44 connects a transmission line (not shown) to impedance matching circuitry 42 at a point where the impedance is substantially equal to the impedance of the transmission line.
The transmission line is preferably a coaxial cable that connects antenna assembly 10 and a radio communications unit (not shown). The transmission line should have an impedance that is orders of magnitude less than the impedance of the antenna assemkly 10 at base end 30 of the third radiating section thereof.
Extendin~ at right angles to a line parallel to the axis of the primary radiating element 12, are first and second stub antennas 50 and 52 respectively. Each preferably has an efective wavelength of one-quar~er of a wavelenyth. The stub antennas 50, 52, are mounted on an i~terior base mem~er 54 which is adapted to be adhered to the inner surface 40 of the glass window.
The interior and exterior mounted coupling members 36 and 38, are designed to be matched in alignment when mounted sinc~ each is intended to be one plate of a capacitor which uses the glass window itself ae the dielectric element.
~3~'J
Turning next to FIG. 3, there is shown a praferredcircuit for use with the antenna of the present invention.
As shown, the primary antenna radiating element 12 is shown directly connected to one plate 100 of a capacitor 102, the other plate 104 of which is connected through a tuning circuit 106 to the ~ign~l lead 108 of a coaxial cable 110 that is coupled to a transceiver (not shown). ~he glass 112 to which the capacitor plates 100, 104 are adherad, is the diel2ctric for the capacitor 102. An adjustable tuning capacitor 1~4 is serially connected to the ~inside~ plate 104, and ~ay, for circuit purposes, be considered a ~lu~pedn capacitive element.
In the preferred embodiment, a first inductor 116 serially couples the capacitors 10~, 114 to the signal lead 108. A second inductor 118 couples the signal lead 108 to the ground or shield 120 of the coaxial cable 110~ The stub antennas 122, 12~ are connected to th~ grounded shield 120, as well.
In use, the circuit ~s connected to a transcaiver and a standing wave ratio m~ter is used in conjunc~ion wi~h the adjustabla tuning capacitor 114 to achieve peak p~rformance in the 820 to 895 ~z frequency band which has been alloted to cellular mobile telephone system use. The total capacitance (of the dielectric panel and the adjusta~le tuning capacitor 114) functions to ~cancel~ the inductive reactance of the antenna.
The inductor~ 116, 118 are selected tc match the impedance of the antenna circuit to the coaxial cable 110 ~ 3 ,J ~
Accordin~ly, energy can be transferred through the glass orother dielectric panel with a minimum of energy loss.
Because the antenna circuit is designed to operate in the power (current and voltage) feed mode, the grounded stub antennas 122, 124 act as a ~mirror image~ (ground plane) of the primary antenna radiating element 12. In the ~bsence of the grounded stub antennas, a reflection current would appear at the coaxial cable 110 and a good impedance match would be di~ficult, if not impossible to achieve.
FIG. 4 is an alternative circuit embodiment in which a second trimmer capacitor 126 is substituted for the second inductor 118 of FIG. 3. Other elements in FIG~ 4, similar to tho~e elements described above for FI~. 3, are shown as primed reference numerals corresponding to their unprimed counterparts in FIG. 3. With the circuit shown in FIG. 4, the optimum frequency range for which it is tuned tends to be quite sharp and narrow. Accordingly, it is not as satisfactory when dealin~ with a relatively broad frequency band such as the approximately 75 MHz bandwidth available in the cellular telephone band. ~owever, for those applications where the freguencies in use fall within a ~airly narrow band, the alternative embodiment should prove satisfactory.
T~rning next to FI~S. 5 and S, there is shown in schematic ~orm an alternative antenna system e~bodying the present invention generally employing stub antennas mounted on a single side of a non conductive body portion of a vehicle along with the principal antenna ~lement. In thi~
embodiment, only a single base element is employed which can be fastened to virtually any surface and does not require anext~rior and an interior mounted ant~nna ass~mbly.
In general, F~GS. 5 and ~ are similar tu FIGS. 3 and 4, respectively, and illustrate the ~eneral el~ctrical connections of an antenna assembly embodying the present invention adapted for mounting to a singl~ ~ide of a non-conductive body portisn of a vehicle. Similar parts retain the same reference numerals, the only difference being the absence of the capacitors 102, 102'.
Finally, it should be noted that if the antenna of the present invention is to be mounted on a body portion o~ a vehicle that i~ suitable as a reflective signal ground plane, then the stub antennas described above may be eliminated and the principal rad~ating element de~cribed above may be directly mounted to the desired location by any number of presently knawn mounting brackets.
The invention described above is, of course, susceptible to many variations, modifications and changes, all of which are within the skill of the art. It should be understood that all s~!ch variations, modi~ications and changes are within the spirik and scope of the invention and o~ the appended claims. SimilarlyO it will be understood that it is intended to cover all changes, modifications and variation~
of the example of the invention herein disclosed for the purpose of illustration which do not constitute departures from the ~pirit and scope of the invention~
Claims (39)
1. A mobile communications antenna assembly for use over a selected band of frequencies in the VHF and UHF
ranges, comprising:
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an effective electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band and said third section having an effective electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band, said third section further adapted to have a radiating surface area substantially greater than the radiating surface areas of said first and second sections by having a diameter substantially greater than the diameter of each of said first and second sections, so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections;
first phase inductance means electrically connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections including an open air helical coil inductor formed from said radiating element;
second phase inductance means electrically connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections including a helical coil inductor formed from said radiating element;
a base member electrically connected adjacent to a base end of said third section for mounting said radiating element to a non-conducting surface of a vehicle, so that said third section base end is elevated above said surface;
a first plate member connected to said third section base end including user adjustment means for positioning said radiating element in a generally vertical configuration with regard to the earth's surface;
impedance matching means comprising a user adjustable capacitance member and a tuned circuit which is selectively tunable to the nominal resonant frequency of said radiating element and electrically connected thereto, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said radiating element, said first value being substantially equal to the impedance at said base end, and a second impedance value that is at least several orders of magnitude less than said first impedance value:
transmission line means for communicating between the antenna assembly and a radio communications unit, said transmission line means having an impedance that is orders of magnitude less than the impedance of the antenna assembly at said base end of said third section; and connecting means for coupling said transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
ranges, comprising:
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an effective electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band and said third section having an effective electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band, said third section further adapted to have a radiating surface area substantially greater than the radiating surface areas of said first and second sections by having a diameter substantially greater than the diameter of each of said first and second sections, so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections;
first phase inductance means electrically connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections including an open air helical coil inductor formed from said radiating element;
second phase inductance means electrically connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections including a helical coil inductor formed from said radiating element;
a base member electrically connected adjacent to a base end of said third section for mounting said radiating element to a non-conducting surface of a vehicle, so that said third section base end is elevated above said surface;
a first plate member connected to said third section base end including user adjustment means for positioning said radiating element in a generally vertical configuration with regard to the earth's surface;
impedance matching means comprising a user adjustable capacitance member and a tuned circuit which is selectively tunable to the nominal resonant frequency of said radiating element and electrically connected thereto, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said radiating element, said first value being substantially equal to the impedance at said base end, and a second impedance value that is at least several orders of magnitude less than said first impedance value:
transmission line means for communicating between the antenna assembly and a radio communications unit, said transmission line means having an impedance that is orders of magnitude less than the impedance of the antenna assembly at said base end of said third section; and connecting means for coupling said transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
2. A mobile communications antenna assembly for use over a selected band of frequencies in the VHF and UHF
ranges, comprising.
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an effective electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band and said third section having an effective electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band;
first phase inductance means electrically connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections;
second phase inductance means electrically connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections;
a base member electrically connected adjacent to a base end of said third section for mounting said radiating element to a surface so that said third section base end is elevated above said surface;
impedance matching means comprising a tuned circuit selectively tunable to the nominal resonant frequency of said radiating element and electrically connected thereto, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said radiating element, said first value being substantially equal to the impedance at said base end, and a second impedance value that is at least several orders of magnitude less than said first impedance value; and connecting means for coupling transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
ranges, comprising.
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an effective electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band and said third section having an effective electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band;
first phase inductance means electrically connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections;
second phase inductance means electrically connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections;
a base member electrically connected adjacent to a base end of said third section for mounting said radiating element to a surface so that said third section base end is elevated above said surface;
impedance matching means comprising a tuned circuit selectively tunable to the nominal resonant frequency of said radiating element and electrically connected thereto, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said radiating element, said first value being substantially equal to the impedance at said base end, and a second impedance value that is at least several orders of magnitude less than said first impedance value; and connecting means for coupling transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
3. A mobile communications antenna assembly in accordance with claim 2 wherein said third section further has a radiating surface area that is substantially greater than the radiating surface areas of said first and second sections.
4. A mobile communications antenna assembly in accordance with claim 2 wherein said impedance matching means includes a user adjustable capacitance member.
5. A mobile communications antenna assembly in accordance with claim 2, further including transmission line means coupled to said connection means for communicating between the antenna assembly and a radio communications unit, said transmission line means having an impedance that is orders of magnitude less than the impedance of the antenna assembly at said base end of said third section.
6. A mobile communications antenna assembly in accordance with claim 2, wherein said impedance matching means comprises a series tuned circuit tuned to the nominal resonant frequency of said radiating element of the antenna assembly.
7. A mobile communications antenna assembly in accordance with claim 2, including a first plate member connected to said third section base end including user adjustment means for positioning said radiating element in a generally vertical configuration with regard to the earth's surface.
8. A mobile communications antenna assembly in accordance with claim 2, wherein said first phase inductance means comprises a helical coil inductor formed from said radiating element.
9. A mobile communications antenna assembly in accordance with claim 8, wherein said helical coil inductor is an open air helical coil inductor.
10. A mobile communications antenna assembly in accordance with claim 2, wherein the surface to which said base member is mounted is a non-conductive body portion of a vehicle.
11. A mobile communications antenna assembly in accordance with claim 10, wherein said non-conductive body portion is a glass window.
12. A mobile communications antenna assembly in accordance with claim 2, wherein said non conductive body portion of said vehicle is a fiber-glass panel.
13. A mobile communications antenna assembly in accordance with claim 2, wherein said third section has a diameter substantially greater than the diameter of each of said first and second sections, so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections.
14. A mobile communications antenna assembly adapted for mounting on a vehicle and adapted for use over a selected band of frequencies in the VHF and UHF ranges, comprising:
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band, and said third section having an electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band, said third section further adapted to have a radiating surface area substantially greater than the radiating surface areas of said first and second sections by having a diameter substantially greater than the diameter of each of said first and second sections, so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections;
first phase inductance means connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections including an open air helical coil inductor formed from said radiating element;
second phase inductance means connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections, said third section having a base end;
a base member, having a first conductive coupling member electrically connected to and disposed adjacent said third section base end, for mounting said radiating element to a first side of a non-conductive body portion of the vehicle so that said third section base end is elevated above the surface of said body portion and including a first adjusting means connected between said third section base end and said first coupling member to permit user adjustment to align said radiating element to be generally vertical with regard to the earth's surface;
a second conductive coupling member mounted on a second, opposite side of said non-conductive body portion in substantial juxtaposition with said first conductive coupling member defining, with said non-conductive body portion, a coupling capacitor having a fixed plate surface area at the third section base and and located adjacent a current node thereof;
impedance matching means comprising a user adjustable capacitance member and a series tuned circuit selectively tunable to the nominal resonant frequency of said radiating element and electrically connected to said second electrically conductive coupling member in the immediate proximity thereof to resonate in conjunction with said radiating element, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said second conductive coupling member which is substantially equal to the impedance at said third section base end and a second impedance value that is at least several orders of magnitude less than said first impedance value;
transmission line means for connection between the antenna assembly and a radio communications unit, said transmission line means having an impedance that is orders of magnitude less than the impedance of the antenna assembly at said third section base end; and coupling means adapted to connect said transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of said transmission line means.
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band, and said third section having an electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band, said third section further adapted to have a radiating surface area substantially greater than the radiating surface areas of said first and second sections by having a diameter substantially greater than the diameter of each of said first and second sections, so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections;
first phase inductance means connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections including an open air helical coil inductor formed from said radiating element;
second phase inductance means connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections, said third section having a base end;
a base member, having a first conductive coupling member electrically connected to and disposed adjacent said third section base end, for mounting said radiating element to a first side of a non-conductive body portion of the vehicle so that said third section base end is elevated above the surface of said body portion and including a first adjusting means connected between said third section base end and said first coupling member to permit user adjustment to align said radiating element to be generally vertical with regard to the earth's surface;
a second conductive coupling member mounted on a second, opposite side of said non-conductive body portion in substantial juxtaposition with said first conductive coupling member defining, with said non-conductive body portion, a coupling capacitor having a fixed plate surface area at the third section base and and located adjacent a current node thereof;
impedance matching means comprising a user adjustable capacitance member and a series tuned circuit selectively tunable to the nominal resonant frequency of said radiating element and electrically connected to said second electrically conductive coupling member in the immediate proximity thereof to resonate in conjunction with said radiating element, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said second conductive coupling member which is substantially equal to the impedance at said third section base end and a second impedance value that is at least several orders of magnitude less than said first impedance value;
transmission line means for connection between the antenna assembly and a radio communications unit, said transmission line means having an impedance that is orders of magnitude less than the impedance of the antenna assembly at said third section base end; and coupling means adapted to connect said transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of said transmission line means.
15. A mobile communications antenna assembly in accordance with claim 14, wherein said non-conductive body portion is a glass window.
16. A mobile communications antenna assembly in accordance with claim 14, wherein said non-conductive body portion of the vehicle is a fiber-glass panel.
17. A mobile communications antenna assembly adapted for mounting on a vehicle and adapted for use over a selected band of frequencies in the VHF and UHF ranges, comprising:
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band and said third section having an electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band;
first phase inductance means connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections;
second phase inductance means connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections, aid third section having a base end;
said third section further having a radiating surface area that is substantially greater than the radiating surface areas of each of said first and second radiating sections;
a base member, having a first conductive coupling member electrically connected to and disposed adjacent said third section base end, for mounting said radiating element to a first side of a non-conductive body portion of the vehicle so that said third section base end is elevated above the surface of said body portion;
a second conductive coupling member mounted on a second, opposite side of said non-conductive body portion in substantial juxtaposition with said first conductive coupling member defining, with said non-conductive body portion, a coupling capacitor having a fixed plate surface area at the third section base end and located adjacent a current node thereof;
impedance matching means comprising a tuned circuit selectively tunable to the nominal resonant frequency of said radiating element and electrically connected to said second electrically conductive coupling member in the immediate proximity thereof to resonate in conjunction with said radiating element, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said second conductive coupling member which is substantially equal to the impedance at said third section base end and a second impedance value that is at least several orders of magnitude less than said first impedance value; and coupling means adapted to connect transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an electrical length substantially equal to five-eighths of the center wavelength of the selected frequency band and said third section having an electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band;
first phase inductance means connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections;
second phase inductance means connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections, aid third section having a base end;
said third section further having a radiating surface area that is substantially greater than the radiating surface areas of each of said first and second radiating sections;
a base member, having a first conductive coupling member electrically connected to and disposed adjacent said third section base end, for mounting said radiating element to a first side of a non-conductive body portion of the vehicle so that said third section base end is elevated above the surface of said body portion;
a second conductive coupling member mounted on a second, opposite side of said non-conductive body portion in substantial juxtaposition with said first conductive coupling member defining, with said non-conductive body portion, a coupling capacitor having a fixed plate surface area at the third section base end and located adjacent a current node thereof;
impedance matching means comprising a tuned circuit selectively tunable to the nominal resonant frequency of said radiating element and electrically connected to said second electrically conductive coupling member in the immediate proximity thereof to resonate in conjunction with said radiating element, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said second conductive coupling member which is substantially equal to the impedance at said third section base end and a second impedance value that is at least several orders of magnitude less than said first impedance value; and coupling means adapted to connect transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
18. A mobile communications antenna assembly in accordance with claim 17 wherein said third section further has a radiating surface area that is substantially greater than the radiating surface areas of said first and second sections.
19. A mobile communications antenna assembly in accordance with claim 17, wherein said impedance matching means includes a user adjustable capacitance member.
20. A mobile communications antenna assembly in accordance with claim 17, further including transmission line means for connection between the antenna assembly and a radio communications unit, said transmission line means having an impedance that is orders of magnitude less than the impedance of the antenna assembly at said third section base end.
21. A mobile communications antenna assembly in accordance with claim 17, wherein said impedance matching means comprises a series tuned circuit that is tuned to the nominal resonant frequency of said radiating element of the antenna assembly.
22. A mobile communications antenna assembly in accordance with claim 17, including a first adjusting means connected between said third section base end and said first coupling member to permit user adjustment to align said radiating element to be generally vertical with regard to the earth's surface.
23. A mobile communications antenna assembly in accordance with claim 17, wherein said first and second inductance means each comprises a helical coil inductor formed from said radiating element.
24. A mobile communications antenna assembly in accordance with claim 23, wherein each said helical coil inductor is an open air helical coil inductor.
25. A mobile communications antenna assembly in accordance with claim 17, wherein said non-conductive body portion is a glass window.
26. A mobile communications antenna assembly in accordance with claim 17, wherein said non-conductive body portion of the vehicle is a fiber-glass panel.
27. A mobile communications antenna assembly in accordance with claim 17, wherein said third section has a diameter substantially greater than the diameter of each of said first and second sections, so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections.
28. A mobile communications antenna assembly for use over a selected band of frequencies in the VHF and UHF ranges, comprising:
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an effective electrical length substantially equal to at least one-half of the center wavelength of the selected frequency band and said third section having an effective electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band, said third section further adapted to have a radiating surface area substantially greater than the radiating surface areas of said first and second sections by having a diameter substantially greater than the diameter of each of said first and second sections, so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections;
first phase inductance means electrically connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections including an open air helical coil inductor formed from said radiating element;
second phase inductance means electrically connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections including a helical coil inductor formed from said radiating element;
a base member electrically connected adjacent to a base end of said third section for mounting said radiating element to a non-conducting surface of a vehicle, so that said third section base end is elevated above said surface;
a first plate member connected to said third section base end including user adjustment means for positioning said radiating element in a generally vertical configuration with regard to the earth's surface;
impedance matching means comprising a user adjustable capacitance member and a series tuned circuit which is selectively tunable to the nominal resonant frequency of said radiating element and electrically connected thereto, said impedance match-ing means displaying an impedance which varies between a first impedance value at said connection to said radiating element, said first value being substantially equal to the impedance at said base end, and a second impedance value that is at least several orders of magnitude less than said first impedance value;
transmission line means for communicating between the antenna assembly and a radio communications unit, said trans-mission line means-having an impedance that is orders of magnitude less than the impedance of the antenna assembly at said base end of said third section; and connecting means for coupling said transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an effective electrical length substantially equal to at least one-half of the center wavelength of the selected frequency band and said third section having an effective electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band, said third section further adapted to have a radiating surface area substantially greater than the radiating surface areas of said first and second sections by having a diameter substantially greater than the diameter of each of said first and second sections, so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections;
first phase inductance means electrically connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections including an open air helical coil inductor formed from said radiating element;
second phase inductance means electrically connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections including a helical coil inductor formed from said radiating element;
a base member electrically connected adjacent to a base end of said third section for mounting said radiating element to a non-conducting surface of a vehicle, so that said third section base end is elevated above said surface;
a first plate member connected to said third section base end including user adjustment means for positioning said radiating element in a generally vertical configuration with regard to the earth's surface;
impedance matching means comprising a user adjustable capacitance member and a series tuned circuit which is selectively tunable to the nominal resonant frequency of said radiating element and electrically connected thereto, said impedance match-ing means displaying an impedance which varies between a first impedance value at said connection to said radiating element, said first value being substantially equal to the impedance at said base end, and a second impedance value that is at least several orders of magnitude less than said first impedance value;
transmission line means for communicating between the antenna assembly and a radio communications unit, said trans-mission line means-having an impedance that is orders of magnitude less than the impedance of the antenna assembly at said base end of said third section; and connecting means for coupling said transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
29. A mobile communications antenna assembly for use over a selected band of frequencies in the VHF and UHF ranges, comprising:
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an effective electrical length substantially equal to one-half of the center wavelength of the selected frequency band and said third section having an effective electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band;
first phase inductance means electrically connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections;
second phase inductance means electrically connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections;
a base member electrically connected adjacent to a base end of said third section for mounting said radiating element to a surface so that said third section base end is elevated above said surface;
impedance matching means comprising a tuned circuit selectively tunable to the nominal resonant frequency of said radiating element and electrically connected thereto, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said radiating element, said first value being substantially equal to the impedance at said base end, and a second impedance value that is at least several orders of magnitude less than said first impedance value; and connecting means for coupling transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
a radiating element having first, second and third, collinear radiating sections, said first and second sections each having an effective electrical length substantially equal to one-half of the center wavelength of the selected frequency band and said third section having an effective electrical length substantially equal to one-quarter of the center wavelength of the selected frequency band;
first phase inductance means electrically connecting said first and second sections for maintaining a predetermined phase relationship between electrical signals radiating from said first and second sections;
second phase inductance means electrically connecting said second and third sections for maintaining a predetermined phase relationship between electrical signals radiating from said second and third sections;
a base member electrically connected adjacent to a base end of said third section for mounting said radiating element to a surface so that said third section base end is elevated above said surface;
impedance matching means comprising a tuned circuit selectively tunable to the nominal resonant frequency of said radiating element and electrically connected thereto, said impedance matching means displaying an impedance which varies between a first impedance value at said connection to said radiating element, said first value being substantially equal to the impedance at said base end, and a second impedance value that is at least several orders of magnitude less than said first impedance value; and connecting means for coupling transmission line means to said impedance matching means at a point where the impedance of said impedance matching means is substantially equal to the impedance of the transmission line means.
30. A mobile communications antenna assembly for use over a selected band of frequencies within the VHF and UHF ranges, comprising:
a radiating element having first, second and third collinear radiating sections, each of said sections having an effective electrical length substantially equal to at least one-quarter of the center wavelength of the selected frequency band;
first phase inductance means electrically connected to said first and second radiating sections, and second phase inductance means electrically connected to said second and third radiating sections respectively, for maintaining a predetermined phase relationship between electrical signals radiating from each of said paired radiating sections;
said second radiating section having a first portion and a second portion including a hollow, generally frusto-conically shaped radiating member attached proximate said second phase inductance means, and having an opening at its base end with sufficient diameter to receive and overlap, at least partially, a portion of said third radiating section, and electrically connected to said third radiating section only through said second phase inductance means; and, said third radiating section further adapted to have a radiating surface area substantially greater than the radiating surface areas of said first and second sections by having a diameter substantially greater than that of said first section and said second section first portion so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections.
a radiating element having first, second and third collinear radiating sections, each of said sections having an effective electrical length substantially equal to at least one-quarter of the center wavelength of the selected frequency band;
first phase inductance means electrically connected to said first and second radiating sections, and second phase inductance means electrically connected to said second and third radiating sections respectively, for maintaining a predetermined phase relationship between electrical signals radiating from each of said paired radiating sections;
said second radiating section having a first portion and a second portion including a hollow, generally frusto-conically shaped radiating member attached proximate said second phase inductance means, and having an opening at its base end with sufficient diameter to receive and overlap, at least partially, a portion of said third radiating section, and electrically connected to said third radiating section only through said second phase inductance means; and, said third radiating section further adapted to have a radiating surface area substantially greater than the radiating surface areas of said first and second sections by having a diameter substantially greater than that of said first section and said second section first portion so as to increase the radiating surface area of said third section in comparison to the radiating surface areas of said first and second sections.
31. A mobile communications antenna assembly in accordance with claim 30, further including, a layer of electrical insulating material interposed between said second radiating section frusto-conically shaped radiating member and said overlapped portion of said third radiating section so as to electrically isolate said second radiating section from said third radiating section and to form a seal therebetween.
32. A mobile communications antenna assembly in accordance with claim 31, wherein said third radiating section is a hollow tube member having sufficient diameter to receive and retain therein said second phase inductance means.
33. A mobile communications antenna assembly in accordance with claim 31, wherein said first and second phase inductance means comprise a first and second helical coil inductor, each formed from said first and second radiating elements, respectively.
34. A mobile communications antenna assembly in accordance with claim 31, wherein said first and second helical coil inductors are open air helical coil inductors.
35. A mobile communications antenna assembly for use over a selected band of frequencies in the VHF and UHF ranges, comprising:
a first hollow, tubular radiating member having an effective electrical length substantially equal to at least one-quarter of the center wavelength of the selected frequency band;
a first phase inductance means for maintaining a predetermined phase relationship of electrical signals in said first radiating member electrically connected to and received, at least partially, in the interior of said first hollow, tubular radiating member;
a second radiating section fabricated from a single wire conductor and having effective electrical length substantially equal to at least one-half of the center wavelength of the selected frequency band and electrically connected collinearly to said first phase inductance means;
a cap member attached to said second radiating section proximate said first phase inductance means and adapted to overlap, at least partially, a portion of said first radiating member for sealing said first phase inductance means within the interior of said first hollow tubular radiating member;
a second phase inductance means for maintaining a predetermined phase relationship of electrical signals in said second radiating member, electrically connected collinearly to said second radiating member; and a third radiating section fabricated from a single wire conductor and having effective electrical length substantially equal to at least one-half of the center wavelength of the selected frequency band and electrically connected collinearly to said second phase inductance means.
a first hollow, tubular radiating member having an effective electrical length substantially equal to at least one-quarter of the center wavelength of the selected frequency band;
a first phase inductance means for maintaining a predetermined phase relationship of electrical signals in said first radiating member electrically connected to and received, at least partially, in the interior of said first hollow, tubular radiating member;
a second radiating section fabricated from a single wire conductor and having effective electrical length substantially equal to at least one-half of the center wavelength of the selected frequency band and electrically connected collinearly to said first phase inductance means;
a cap member attached to said second radiating section proximate said first phase inductance means and adapted to overlap, at least partially, a portion of said first radiating member for sealing said first phase inductance means within the interior of said first hollow tubular radiating member;
a second phase inductance means for maintaining a predetermined phase relationship of electrical signals in said second radiating member, electrically connected collinearly to said second radiating member; and a third radiating section fabricated from a single wire conductor and having effective electrical length substantially equal to at least one-half of the center wavelength of the selected frequency band and electrically connected collinearly to said second phase inductance means.
36. A mobile communications antenna assembly in accordance with claim 35, further including, a layer of electrical insulating material interposed between said cap member of said second radiating section and said overlapped portion of said first radiating section so as to electrically isolate said cap member from direct connection with said overlapped portion of said first radiating section and to form a seal therebetween.
37. A mobile communications antenna assembly in accordance with claim 35, wherein said first and second phase inductance means comprise a first and second helical coil inductor each formed from said second and third radiating elements, respectively.
38. A mobile communications antenna assembly in accordance with claim 37, wherein said first and second helical coil inductors are open air helical coil inductors.
39. A mobile communications antenna assembly in accordance with claim 35, wherein said second and third radiating sections and said second phase inductance means are fabricated from the same single wire element.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/202,123 | 1988-06-03 | ||
| US07/202,123 US4857939A (en) | 1988-06-03 | 1988-06-03 | Mobile communications antenna |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1322786C true CA1322786C (en) | 1993-10-05 |
Family
ID=22748586
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000601606A Expired - Fee Related CA1322786C (en) | 1988-06-03 | 1989-06-02 | Mobile communications antenna |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4857939A (en) |
| EP (1) | EP0348054A3 (en) |
| JP (1) | JPH0236602A (en) |
| KR (1) | KR920002895B1 (en) |
| CA (1) | CA1322786C (en) |
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-
1988
- 1988-06-03 US US07/202,123 patent/US4857939A/en not_active Expired - Fee Related
-
1989
- 1989-06-02 CA CA000601606A patent/CA1322786C/en not_active Expired - Fee Related
- 1989-06-02 EP EP89305569A patent/EP0348054A3/en not_active Withdrawn
- 1989-06-03 JP JP1140267A patent/JPH0236602A/en active Pending
- 1989-06-03 KR KR1019890007643A patent/KR920002895B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| KR920002895B1 (en) | 1992-04-06 |
| US4857939A (en) | 1989-08-15 |
| EP0348054A2 (en) | 1989-12-27 |
| JPH0236602A (en) | 1990-02-06 |
| KR900001055A (en) | 1990-01-31 |
| EP0348054A3 (en) | 1990-08-08 |
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| Date | Code | Title | Description |
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| MKLA | Lapsed |