CA1201802A - Waveguide with dielectric loaded flange antenna feed - Google Patents
Waveguide with dielectric loaded flange antenna feedInfo
- Publication number
- CA1201802A CA1201802A CA000429126A CA429126A CA1201802A CA 1201802 A CA1201802 A CA 1201802A CA 000429126 A CA000429126 A CA 000429126A CA 429126 A CA429126 A CA 429126A CA 1201802 A CA1201802 A CA 1201802A
- Authority
- CA
- Canada
- Prior art keywords
- waveguide
- flange
- dielectric
- feed
- antenna feed
- 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
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
- H01Q13/06—Waveguide mouths
- H01Q13/065—Waveguide mouths provided with a flange or a choke
Landscapes
- Aerials With Secondary Devices (AREA)
- Waveguide Aerials (AREA)
Abstract
TITLE
WAVEGUIDE WITH DIELECTRIC LOADED
FLANGE ANTENNA FEED
INVENTORS
Apisak Ittipiboon Lotfollah Shafai Ernest Bridges ABSTRACT OF THE DISCLOSURE
The antenna feed includes a waveguide radiator with a conduc-tive flange positioned about the waveguide near its radiating end. A
dielectric element is positioned about the waveguide between the flange and the radiating end and establishes the dielectric surface impedance seen by the waveguide. The dielectric element may consist of one or more layers of dielectric material to form a composite dielectric. One of the layers may be an air gap adjacent to the flange. The size and position of the flange and dielectric element will control the radiation pattern of the beam from the feed.
WAVEGUIDE WITH DIELECTRIC LOADED
FLANGE ANTENNA FEED
INVENTORS
Apisak Ittipiboon Lotfollah Shafai Ernest Bridges ABSTRACT OF THE DISCLOSURE
The antenna feed includes a waveguide radiator with a conduc-tive flange positioned about the waveguide near its radiating end. A
dielectric element is positioned about the waveguide between the flange and the radiating end and establishes the dielectric surface impedance seen by the waveguide. The dielectric element may consist of one or more layers of dielectric material to form a composite dielectric. One of the layers may be an air gap adjacent to the flange. The size and position of the flange and dielectric element will control the radiation pattern of the beam from the feed.
Description
d~V~
Background of the Invention ~ lis inventlon is directed to paraboloid antennas, and in particular to a simple ~eed for these antennas.
The prlme focus fed paraboloid ls one of the most commonly used high gain antenna systems. It has been widely used in earth-station antenna6, microwave relay systems and radio~telescopes. It has a simple geometry and is generally inexpenslve to fabricate. It conslsts o a reflecting paraboloid surface with a feed system at its focus. Since the performance of this type of antenna relates closely to its f~ed~ the feed has to be designed for hlgh antenna efficiency and low cross-polariza-tion, which can be achieved with a feed having a symmetric E and H plane radlation patterns. A common feed, which has been used because of its simpllcity and low cost, is a waveguide radiator supporting the dominant mode. H~wever, this type of feed generally has asymmetric E and H plane radiation patterns, thus causing a loss in the efficiency of the reflec-tor and a high cross-pQlar radlation. ~ligh efEiciency feeds with symmet-ric ~ and 1I plane patterns are normally designed using corrugated or multi-mode horns. A common design conslsts of a circular waveguide Witi a 90 degree corrugated flange, such as the one described in Canadian patent no. ~73,547, which was issued to R.F.H. Yang et al on June 15, 1971, and whlch corresponds to United States Patent No. 3,553,707, which issued on January 5, 1971. It can be designed to have good circular patterns, to give hlgh efficiency with reflector antennas, but due to its corrugated surface, is costly to fabricate.
Summary of the Invention It is therefore an ob~ect of this invention to provide a feed wbich is capable of producing symmetric E and 1I plane patterns and which still is relatively simple to fabricate.
This and other ob~ects are achieved in the feed for a parabo-loid antenna which includes a waveguide with a first end havihg anelectrical coupler, and a second radiating end. A conductive 1ange is positioned about the waveguide at a predetermined distance from the radiatlng end. A dielectric element is positioned about the waveguide between the flange and the radiating end, this element establishes the surface impedance seen by the waveguide.
In accordance wlth one aspect o~ this invention, the dielectric : 1 ~ o~
elenent may consist of two or more layers of dielectric material. One of the dielectric layers may be an air gap ad~acent to the flange, In accordance with another aspect of this lnvention, the wave-guide and flange may both be circular, the flange may have a dia1neter of less than 5~ and be positioned at a tiistance of less than ~ from the ra-diating end of the waveguide, where ~ is the wsvelength of the operatlng frequency of the antenna.
Hany other ob~ects and aspects of the invention wlll be clear from the detailed description of the drawings.
Brief Description of the Drawings In the drawin~s Figure 1 illustrates, in cross-section, an antenna feed in accordance with the present invention, Figure 2 illustrates a second embodiment of the antenna feed;
and Figure 3 il]u~trates the R-11 radiation patCerns oE an antenna feed.
Detailed ~escription The antenna feed shown in figure 1 consists of a waveguide 2 which would normally be circular. One end of the wavegulde 2 is fitted with a coupler 3, in any conventional manner, such that it may be elec-trically coupled to act as a transmLtter or a receiver. For transmis-sion, purposes the dominant TEll mode would normally be excited in the waveguide 2. The other end 4 of the waveguide may be open-ended or may include a transparent window which would be mounted in any conven-tional manner. In accordance with the present invention, the antenna feed l further includes a conductive flange 5 mounted about the waveguide
Background of the Invention ~ lis inventlon is directed to paraboloid antennas, and in particular to a simple ~eed for these antennas.
The prlme focus fed paraboloid ls one of the most commonly used high gain antenna systems. It has been widely used in earth-station antenna6, microwave relay systems and radio~telescopes. It has a simple geometry and is generally inexpenslve to fabricate. It conslsts o a reflecting paraboloid surface with a feed system at its focus. Since the performance of this type of antenna relates closely to its f~ed~ the feed has to be designed for hlgh antenna efficiency and low cross-polariza-tion, which can be achieved with a feed having a symmetric E and H plane radlation patterns. A common feed, which has been used because of its simpllcity and low cost, is a waveguide radiator supporting the dominant mode. H~wever, this type of feed generally has asymmetric E and H plane radiation patterns, thus causing a loss in the efficiency of the reflec-tor and a high cross-pQlar radlation. ~ligh efEiciency feeds with symmet-ric ~ and 1I plane patterns are normally designed using corrugated or multi-mode horns. A common design conslsts of a circular waveguide Witi a 90 degree corrugated flange, such as the one described in Canadian patent no. ~73,547, which was issued to R.F.H. Yang et al on June 15, 1971, and whlch corresponds to United States Patent No. 3,553,707, which issued on January 5, 1971. It can be designed to have good circular patterns, to give hlgh efficiency with reflector antennas, but due to its corrugated surface, is costly to fabricate.
Summary of the Invention It is therefore an ob~ect of this invention to provide a feed wbich is capable of producing symmetric E and 1I plane patterns and which still is relatively simple to fabricate.
This and other ob~ects are achieved in the feed for a parabo-loid antenna which includes a waveguide with a first end havihg anelectrical coupler, and a second radiating end. A conductive 1ange is positioned about the waveguide at a predetermined distance from the radiatlng end. A dielectric element is positioned about the waveguide between the flange and the radiating end, this element establishes the surface impedance seen by the waveguide.
In accordance wlth one aspect o~ this invention, the dielectric : 1 ~ o~
elenent may consist of two or more layers of dielectric material. One of the dielectric layers may be an air gap ad~acent to the flange, In accordance with another aspect of this lnvention, the wave-guide and flange may both be circular, the flange may have a dia1neter of less than 5~ and be positioned at a tiistance of less than ~ from the ra-diating end of the waveguide, where ~ is the wsvelength of the operatlng frequency of the antenna.
Hany other ob~ects and aspects of the invention wlll be clear from the detailed description of the drawings.
Brief Description of the Drawings In the drawin~s Figure 1 illustrates, in cross-section, an antenna feed in accordance with the present invention, Figure 2 illustrates a second embodiment of the antenna feed;
and Figure 3 il]u~trates the R-11 radiation patCerns oE an antenna feed.
Detailed ~escription The antenna feed shown in figure 1 consists of a waveguide 2 which would normally be circular. One end of the wavegulde 2 is fitted with a coupler 3, in any conventional manner, such that it may be elec-trically coupled to act as a transmLtter or a receiver. For transmis-sion, purposes the dominant TEll mode would normally be excited in the waveguide 2. The other end 4 of the waveguide may be open-ended or may include a transparent window which would be mounted in any conven-tional manner. In accordance with the present invention, the antenna feed l further includes a conductive flange 5 mounted about the waveguide
2 and electrically connected to lt at a distAnce Ll from the end 4 of the waveguide 2. For a circular waveguide 2, the flange may be circular with a diameter ~. A dlelectric element ~ is located about the waveguide 2 between the flange 5 and the radiating end 4 of the waveguide 2. The dielectric element 6 will preferably have at least the same dimensions as the flange 5 in the plane of the flange, i.e~ with a diameter ~D for a circular flange 5. The dielectric element 6 may consist of one or more uniform thicknessl or tapered layers 71, 7 ,.., of dielectric matetial fixed to the flan~e S with the dielectric layer surface at a distance of , lZ~8~12 L2 from the end 4 of the waveguide 2 as shown in figure 2. Ilowever, in order to provide an ad~ustable feed 1, the dielectric element 6 msy in-clude one or ~ore uniform thickness, or tapered layer~ 8'... mounted about the waveguide 2 so as to be moveable along the waveguide 2 in the axis of the waveguide 2. In this type of element 6, the airgap 9 of thickness 1.3 between the flange 5 and the layer 8' will constitute one of the dielectric layers of the element 6 to form the compvsite dielectric.
The size and the position of the flange 5 are selected to con-trol the backward radiation, tlle surface wave generation on the flange 5, as well as the deslred radiation pattern. For normal operation, the dia-meter D of the flange 5 would be set at less than 5~, where A is the wavelength of the operating frequency. This flange size keeps surface waves at a low lever minimizing the slde lobe level. The distance L1 of the flange 5 from the end 4 oE the waveguide 2 would normally not be greater than A. This distance controls the relative phase of the reflec ted field and, thus~ the radiation pattern of the feed 1.
The overall thickness and the composite dielectrlc constant E
of tlle dielectric element 6 determlnes the surface impedance seen by the waveguide from end 4. Though a Ruitable antenna feed 1 may be designed wlth a single dielectric layer 7', the use of number of layers 7', 7 ~O~
facilitates the optimum design of a feed 1 for a particular application slnce the various parameters may ~e more easily ad~ustad. In addition, the use of a movea~le dielectric layer 8' in the element 6 provides the flexibility of allowing the feed to be ad~usted in its particular appli-cation.
As an example, a primary feed 1 for a reflector antenna whichls to be excited by tne dominant TE1~ mode in the frequency range of 11.0-12.0 G~z, consists of a clrcular waveguide 2 having a flanga 5 of diameter D - 1.8A, positioned at a distance Ll ~ A from the radiating 0 end 4 of the waveguide 2. A single dielectric layer 8' of uniform thick-f~ Jer~)ar~
ness plexiglass' having a relative dielectric constant ~r = 2.5ll~ is positioned on the waveguide 2 at a distance L2 = 0.4A, from the end 4 such that the dielectric element 6 includes an airgap with a thlckness L3 = 0.25~ ese parameters of the flange 5 and the dlelectric ele-ment 6 assure that the flange 5 can support only a TMo surface wave mode which combines with the dominant TE11 mode to form the radiationpattern~
The E and H plane radiation patterns frQm this antenna feed are illustrated in figure 3, where lines 31, 33 and 35 represent the E-plane radiation pattern at l1.0, 11.5, and 12.Q ~1z excitation, and, ~ere lines 32, 34 and 36 represent the H-plane rfldiation pattern at 11.0, 11.5, and 12.n ~z excitation, the planes for the different frequencies being normalized at different levels.
From these results, it is found that the E and H plane radia-tion patterns are quite similar for ~ ~ 96, which is a wide enough anglefor most paraboloid reflectors. The patterns of both planes, E and H, have a dip along the antenna axis of about 3 dB and 2dB, respectively, which can be controlled by the thickness of airgap 9 between the clielec-tric layer 8' and the flange 5. Because of this dip in the radiation pattern, the aperture illumination of the reflector will be more uniform, thus providing a high gain factor. From the results shown in figure 3, it is also clear that the patterns are quite constant over the frequency range 11.0-12.0 CH7.. It was found that the ~-plane 10 dB half beamwidth at 11.0 and 11.5 ~Iz are approximatly 6~, while it is about 66 at 12.0 GHz.
During cross-polarization measurements, it was found that the peak cross-polarization is approximately -20 dB at 11.0 GHz, -23 dB at 11.5 GHz, and -24 dB at 12.0 GHz. ~owever, it should be noted that these are the cross-polarization levels of the feed, not the secondary pattern.
25 The cross-polarization levels of the secondary pattern should be small -when the E and ~ plane feed radiation patterns are similar.
The antenna feed in accordance wlth this invention is thus 6een to have the advantages of having good transmission characteristics while at the sa~e time being relatively easy and inexpensive to fabricate on either a small or large scale.
Many modifications in the above described embodiments of the invention can be carried out without departing from the scope thereof and, therefore, the scope of tlle present inventlon is intended to be limlted only by the appended claims.
The size and the position of the flange 5 are selected to con-trol the backward radiation, tlle surface wave generation on the flange 5, as well as the deslred radiation pattern. For normal operation, the dia-meter D of the flange 5 would be set at less than 5~, where A is the wavelength of the operating frequency. This flange size keeps surface waves at a low lever minimizing the slde lobe level. The distance L1 of the flange 5 from the end 4 oE the waveguide 2 would normally not be greater than A. This distance controls the relative phase of the reflec ted field and, thus~ the radiation pattern of the feed 1.
The overall thickness and the composite dielectrlc constant E
of tlle dielectric element 6 determlnes the surface impedance seen by the waveguide from end 4. Though a Ruitable antenna feed 1 may be designed wlth a single dielectric layer 7', the use of number of layers 7', 7 ~O~
facilitates the optimum design of a feed 1 for a particular application slnce the various parameters may ~e more easily ad~ustad. In addition, the use of a movea~le dielectric layer 8' in the element 6 provides the flexibility of allowing the feed to be ad~usted in its particular appli-cation.
As an example, a primary feed 1 for a reflector antenna whichls to be excited by tne dominant TE1~ mode in the frequency range of 11.0-12.0 G~z, consists of a clrcular waveguide 2 having a flanga 5 of diameter D - 1.8A, positioned at a distance Ll ~ A from the radiating 0 end 4 of the waveguide 2. A single dielectric layer 8' of uniform thick-f~ Jer~)ar~
ness plexiglass' having a relative dielectric constant ~r = 2.5ll~ is positioned on the waveguide 2 at a distance L2 = 0.4A, from the end 4 such that the dielectric element 6 includes an airgap with a thlckness L3 = 0.25~ ese parameters of the flange 5 and the dlelectric ele-ment 6 assure that the flange 5 can support only a TMo surface wave mode which combines with the dominant TE11 mode to form the radiationpattern~
The E and H plane radiation patterns frQm this antenna feed are illustrated in figure 3, where lines 31, 33 and 35 represent the E-plane radiation pattern at l1.0, 11.5, and 12.Q ~1z excitation, and, ~ere lines 32, 34 and 36 represent the H-plane rfldiation pattern at 11.0, 11.5, and 12.n ~z excitation, the planes for the different frequencies being normalized at different levels.
From these results, it is found that the E and H plane radia-tion patterns are quite similar for ~ ~ 96, which is a wide enough anglefor most paraboloid reflectors. The patterns of both planes, E and H, have a dip along the antenna axis of about 3 dB and 2dB, respectively, which can be controlled by the thickness of airgap 9 between the clielec-tric layer 8' and the flange 5. Because of this dip in the radiation pattern, the aperture illumination of the reflector will be more uniform, thus providing a high gain factor. From the results shown in figure 3, it is also clear that the patterns are quite constant over the frequency range 11.0-12.0 CH7.. It was found that the ~-plane 10 dB half beamwidth at 11.0 and 11.5 ~Iz are approximatly 6~, while it is about 66 at 12.0 GHz.
During cross-polarization measurements, it was found that the peak cross-polarization is approximately -20 dB at 11.0 GHz, -23 dB at 11.5 GHz, and -24 dB at 12.0 GHz. ~owever, it should be noted that these are the cross-polarization levels of the feed, not the secondary pattern.
25 The cross-polarization levels of the secondary pattern should be small -when the E and ~ plane feed radiation patterns are similar.
The antenna feed in accordance wlth this invention is thus 6een to have the advantages of having good transmission characteristics while at the sa~e time being relatively easy and inexpensive to fabricate on either a small or large scale.
Many modifications in the above described embodiments of the invention can be carried out without departing from the scope thereof and, therefore, the scope of tlle present inventlon is intended to be limlted only by the appended claims.
Claims (5)
1. A feed for a paraboloid antenna comprising:
- a waveguide with a first end having an electrical coupler and a second radiating end;
- a conductive flange positioned about the waveguide at a distance L1 from the radiating end; and - a dielectric element positioned about the waveguide between the flange and the radiating end to establish a predetermined surface impedance seen by the waveguide.
- a waveguide with a first end having an electrical coupler and a second radiating end;
- a conductive flange positioned about the waveguide at a distance L1 from the radiating end; and - a dielectric element positioned about the waveguide between the flange and the radiating end to establish a predetermined surface impedance seen by the waveguide.
2. A feed as claimed in claim 1 wherein the dielectric element consists of two or more layers of dielectric material.
3. A feed as claimed in claim 2 wherein one of the dielectric layers is an air gap adjacent the flange.
4. A feed as claimed in claim 1, 2 or 3 wherein the distance L1? .lambda., where .lambda. is the wavelength of the operating frequency of theantenna.
5. A feed as claimed in claim 1, 2 or 3 wherein the waveguide and the flange are circular, and the flange has a diameter D ? 5.lambda..
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US385,251 | 1982-06-04 | ||
| US06/385,251 US4516129A (en) | 1982-06-04 | 1982-06-04 | Waveguide with dielectric coated flange antenna feed |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1201802A true CA1201802A (en) | 1986-03-11 |
Family
ID=23520642
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000429126A Expired CA1201802A (en) | 1982-06-04 | 1983-05-26 | Waveguide with dielectric loaded flange antenna feed |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4516129A (en) |
| CA (1) | CA1201802A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4651159A (en) * | 1984-02-13 | 1987-03-17 | University Of Queensland | Microstrip antenna |
| US6239761B1 (en) | 1996-08-29 | 2001-05-29 | Trw Inc. | Extended dielectric material tapered slot antenna |
| RU2696661C1 (en) * | 2018-09-17 | 2019-08-05 | Российская Федерация, от имени которой выступает Государственная корпорация по атомной энергии "Росатом" | Dielectric beam emitter |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2414376A (en) * | 1942-04-27 | 1947-01-14 | Rca Corp | Wave guide |
| US2556046A (en) * | 1946-03-28 | 1951-06-05 | Philco Corp | Directional antenna system |
| US2761138A (en) * | 1946-05-10 | 1956-08-28 | Dora F Sherman | Isotropic radiator |
| US2617029A (en) * | 1948-06-29 | 1952-11-04 | Kinsey L Plummer | Nutating antenna |
| GB693654A (en) * | 1951-03-21 | 1953-07-01 | Gen Electric Co Ltd | Improvements in or relating to aerial systems |
| US2921309A (en) * | 1954-10-08 | 1960-01-12 | Hughes Aircraft Co | Surface wave omnidirectional antenna |
| US2993205A (en) * | 1955-08-19 | 1961-07-18 | Litton Ind Of Maryland Inc | Surface wave antenna array with radiators for coupling surface wave to free space wave |
| US3434146A (en) * | 1966-08-03 | 1969-03-18 | Us Army | Low profile open-ended waveguide antenna with dielectric disc lens |
| US3553707A (en) * | 1967-05-25 | 1971-01-05 | Andrew Corp | Wide-beam horn feed for parabolic antennas |
| US3771161A (en) * | 1972-09-11 | 1973-11-06 | Andrew Corp | Printed-circuit feed for reflector antennas |
-
1982
- 1982-06-04 US US06/385,251 patent/US4516129A/en not_active Expired - Fee Related
-
1983
- 1983-05-26 CA CA000429126A patent/CA1201802A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4516129A (en) | 1985-05-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |