US2615131A - Antenna and matching circuit - Google Patents

Description

1952 N. E. LINDENBLAD ANTENNA AND MATCHING CIRCUIT Filed Sept. 12, -1946 mad 71; BY

COIVOUCT/I E JHEET GP.

l GROUND FLA/V5 Patented Oct. 21, 1952- ANTENNAIYAND MATCHING CIRCUIT Nils E. Lindenblad, Port Jefferson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application September 12, 1946, Serial No. 696,556

Still a further object of the present invention is the provision of a simple means for matching'a transmission line to a broadband antenna.

Another object of the present invention is the provision of a matching system which will enablethe matching of a transmission" line to an antenna over a wide range of conditions by a simple adjustment of the proportions of parts of the matching circuit.

The foregoing objects and others which may appear from the following detaileddescri'ption are attained by providing anantenna in'the form of a hollow conductive member having transverse dimensions which are large in terms of the operating wavelength. Ordinarily the radiator will" beso'po'sitioned as to extend perpendicularly'away from a conductive sheet. A coaxial transmission line is arranged to pierce the ground sheet and extend into the hollow interior of the radiator. The inner conductor of the transmission line'is so arranged to extend further into the hollow interior of the radiator than the outer shell.-

By proportioning the relative extensions 'of the outer shell and inner conductor into hollow interior'of the radiator, the input impedance of the radiator may be easily matched to any convenient transmission line impedance. The pro-' trusion of the inner conductor beyond the outer conductor of the transmission line is smaller the higher the matching. impedance required. The outer conductor of the transmission line is at the same time longer.

Thepresentv invention will be more fully understood by reference to the following detailed de-; scription which is accompanied by a drawing in which; v

- Figure 1 illustrates in transverse cross section anxelementary type of vertical radiator known in; the art'which isutilized as a basis for the matching circuit ofthe present invention, while .Figure 2 illustrates in transverse section an embodiment of the present invention, and

-gures 3 and 4 illustrate modification'sthereof; A

Referring'now to Figure lth 'ereis shown 'a" conductive sheet GP which may-under some 13 Claims. (Cl. 250-33) 2 circumstances be the outer conductive skin of an airplane or it may be a flat metal roof on the top of a tall building. Beneath ground plane GP is a concentric transmission line having an outer shell i0 and an iner conductor I 2. The transmission line extends through the ground sheet GP at right angles to the plane of the sheet to form'a quarter wave antena. The outer shell I!) of the transmission line may extend approximately one third of the distance up from the ground sheet GP as a sleeve 28 while. the inner conductor extends a further distance as a radiator 22. The overall'length of the radiat-' ing fportion of the antenna 'is approximately one quarter wavelength at the operating frequency. I In Figure 2 the ground sheet and transmission line arrangement is the same, as described with reference to Figure 1. However, in this modification the radiator itself is in the form of a hollow conductive member [9 closed at the top and connectedto groundplane GP by connection It. a transverse dimensionwhich' is fairly large in terms of the operating wavelength; for example, somewhere between one eighth and three sixteenths of the operating wavelength. radiator I 9 thus possesses broad band characteristics. proximately a quarter wavelength. The transmission line is coupled to the interior of radiator Ill by the extension of sleeve 20 and extending conductor 22 within the hollow interior of radiator l9. Sleeve 28 is provided with an upper slidable sleeve 2| and member 22 is provided with a slidable outer sleeve 23 whereby the relative extensions of these members within the radiator I!) may readily be adjusted. By adjusting these extensions the 'efiective impedance of theantenna, as seen from the transmission line TL, may be adjusted to perfectly match 'the radiator l9 to the transmission line. The

30 around its lower edge. The flange 39 is electrically and mechanically connected to the. ground plane GP. The transmission line arrangement in Figure 3 is the same as in Figure 1.

.As so 'far described the arrangement of Fig.3 permits the coupling of the transmission "line TL to the interior of radiatormember 2.! but in the absence of any communication between the interior and exterior of member 29110 radiation would be possible. Therefore, I have provided a t series of apertures or'circumferentially extending It is preferred that member [9 have The overall length of radiator I9 is -ap'-' slots 3| around the base of the radiator member 29 by means of which the interior thereof may be coupled to the exterior. The outside dimensions of radiator 29 and the extent of the coupling provided by slots 3| efiects to some extent the required extension of sleeve 20 and inner conductor 22 into the interior of radiator 29 to provide a match to any given transmission line. However, where a 50 ohm transmission line is used the outer sleeve 20 of the transmission line may extend over two thirds of the length of the inner conductor within radiator 29 and above ground plane GP while the inner conductor may extend nearly to the top of member 29. It will thus be seen that I have provided a radiator which issturdily constructed while still having a broad band characteristic. The excitation system permits a wide range of impedance transformation and reactance balancing.

Figure 4 shows a further modification of Figure 2. Here radiator 39 is similar to radiator l9, except that it is approximately a half wave in length. The transmission line arrangement within the radiator is the same as in previous figures except that due to the greater length of radiator 39, it terminates at somewhere near the center thereof. Ihe interior of radiator 39 is coupled to the exterior by apertures 4| at the midsection.

While I have illustrated a particular embodiment of the present invention, it should be clearly understood that it is not limited thereto since many modifications may be made in the several elements employed and in their arrangement without departing from the spirit and scope of the invention.

What is claimed is:

1. A broad band antenna system including a radiation transferring element comprising an elongated hollow conductive member closed at onev end and arranged substantially normal to one side of a conductive ground plane system, and means to transferenergy from said hollo-w member to a utilization device, said means comprising a length of coaxial transmission line of given characteristic impedance having sleeve and inner conductors extending into said hollow member, said sleeve conductor being connected to said ground plane system and said inner conductor extending into said hollow member to a greater distance than said sleeve conductor, the distances of the extension of said conductors into said hollow member having values at which the impedance of said hollow member at the operating wavelength is substantially matched to said given characteristic impedance plane system, said hollow conductive member having longitudinal and transverse dimensions large interms of the operating wavelength and having, the longitudinaldimensions extending in a direction substantially normal to said ground plane system, and means to transfer energy from said hollow member to a utilization device, said means comprising a length of coaxial transmis-' sion line of given characteristic impedance having sleeve and inner conductors extending into said hollow member. said sleeve conductor only being connected to said ground plane system and said inner conductor extending into said hollow member to a greater distance than said sleeve conductor, the sole coupling of said inner conductor to said hollow member being by radiation of energy therebetween, the distances of the extension of said conductors into said hollow member having values at which the impedance of said hollow member at the operating wavelength is substantially matched to said given characteristic impedance of said coaxial transmission line section.

3. An antenna system including a radiation transferring element comprising an elongated hollow conductivev member closed at one end and arranged to one side of a conductive ground plane system, said hollow conductive member having longitudinal dimensions of at least a quarter of the operating wavelength extending in a direction substantially normal to said ground plane system transverse dimensions of at least an eighth of the operating wavelength, and means to transfer energy from said hollow member to a utilization device, said means comprising a length of coaxial transmission line of given characteristic impedance having sleeve and inner conductors extending into said hollow member, said sleeve conductor only being connected to said ground plane system and said inner conductor extending into said hollow member to a greater distance than said sleeve conductor, the distances of the extension of said conductors into said hollow member having values at which the impedance of said hollow member at the operating wavelength is substantially matched to said given characteristic impedance of said coaxial transmission line section, said inner conductor being free of any direct current connection to said hollow member.

4. A broad band antenna system including a radiation transferring element comprising an elongated hollow conductive member closed atone end and arranged substantially normal to one side of a conductive ground plane system, the end of said hollow member remote from said one end being connected to said conductive ground plane system, there being apertures therein interconnecting the interior of said hollow member with ambient space, and means to transfer energy from said hollow member to a utilization device, said means comprising a length of coaxial transmission line of given characteristic impedance having sleeve and inner conductors extending into said-hollow member, said sleeve conductor only being connected to said ground plane system and said. inner conductor extending into said hollow member to a greater distance than said sleeve conductor, the distances of the extension of said i conductors into said hollow member having values at which the impedanc of said hollow member at the operatin wavelength is substantially matched to said given characteristic impedance of said coaxial transmission line section said inner conductor being free of any direct connection to said hollow member.

5. An antenna system for operation in conjunctionwith a-conductive ground sheet, including an elongated conductive dome having a flange than said sleeve conductor and being free of any direct current connection to said conductive dome.

6. An antenna system for operation in conjunction with a conductive ground plane system, including a hollow, substantially closed, elongated conductive member having a plurality of circumferentially arranged slots therein, a section of coaxial transmission line of given characteristic impedance and having sleeve and inner conductors extending into said hollow conductive member with the inner conductor extending therein a greater distance than the sleeve conductor, the sleeve conductor being connected to said conductive member at the point of entry therein, and said member being connected to said conductive ground plane system, the degree of extension of said conductors into said hollow member having a value at which the operating impedance of said hollow member is substantially matched to the characteristic impedance of said coaxial transmission line, the sole coupling between said inner conductor and said hollow member being by radiation therebetween.

'7. A broad band antenna system for operation in conjunction with a conductive ground sheet, including an elongated conductive dome having a flange at the base thereof and a plurality of slots therein near the base, a length of coaxial transmission line having sleeve and inner conductors extending into said dome, said sleeve conductor being electrically connected to said flange, said inner conductor extending into said dome to a greater distance than said sleeve conductor, the sole connection between said conductors and said dome being a connection of said sheath conductor to said ground slot substantially at said flange.

8. A broad band antenna system for operation in conjunction with a conductive ground plane system, including a hollow substantially closed, elongated. conductive member having a plurality of circumferentially arranged slots therein and being connected to said conductive ground plane system, a section of coaxial transmission line having sleeve and inner conductors extending through said ground sheet and into said hollow conductive member with the inner conductor extending therein a greater distance than the sleeve conductor, the sleeve conductor being connected to said conductive member at the point of entry therein to form the sole direct connection between said conductors and said conductive member.

9. A broad band antenna system for operation in coniunction with a conductive ground sheet, including an elongated hollow conductive member closed at one end and arranged substantially normal to the plane of said ground sheet, there being at least one aperture near the lower end of said hollow member and said ground sheet, a section of coaxial transmission line havin sleeve and inner conductors extending through said ground sheet into said hollow conductive member, said inner conductor extending into said hollow conductive member to a greater distance than said sleeve conductor, said inner conductor being free of connection with said conductive member, and the end of said conductive member adjacent said round sheet and said sleeve conductor being connected to said ground sheet.

10. An antenna system for operation in conjunction with a conductive ground sheet, including an elongated hollow conductive member closed at one end and. arranged substantially normal to the plane of said ground sheet, and a section of coaxial transmission line having sleeve and inner conductors extending into said hollow member, said sleeve conductor being connected to said ground sheet, said inner conductor extending into said hollow conductive member to a greater distance than said sleeve conductor, and said inner conductor being free of connection with said conductive member.

11. An antenna system for operation in conjunction with a conductive ground sheet, includ ing an elongated hollow conductive member ,closed at one end and arranged substantially normal to the plane of said ground sheet, a section of coaxial transmission line having sleeve and inner conductors extending into said hollow conductive member, said inner conductor extending into said hollow conductive member to a greater distance than said sleeve conductor, said inner conductor being free of connection with said conductive member, said conductive member having apertures therein, and the end of said conductive member adjacent said ground sheet and said sleeve conductor being connected to said ground sheet.

12. An antenna system for operation in conjunction with a conductive ground sheet, including an elongated hollow conductive member closed at one end and having the other end connected to said ground sheet, a section of coaxial transmission line having sleeve and inner conductors extending into said hollow conductive member, said inner conductor extending into said hollow conductive member to a greater distance than said sleeve conductor, said inner conductor being free of connection with said conductive member, said conductive member having apertures therein near the point of connection to said ground sheet and said sleeve conductor being connected to said ground sheet.

13. An antenna system for operation in conjunction with a conductive ground sheet, including an elongated hollow conductive member closed at both ends and arranged substantially normal to the plane of said ground sheet, a section of coaxial transmission line having sleeve and inner conductors extending into said hollow conductive member, said inner conductor extending into said hollow conductive member to a greater distance than said sleeve conductor, said inner conductor being free of connection with said conductive member, said conductive member having apertures therein substantially midway of the ends thereof, and the end of said conduc' tive member adiacent said ground sheet being connected to said ground sheet by said sleeve conductor.

N'ILS E. LINDENBLAD.

REFERENCES CITED The following references are of record in the file of this patent:

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