US2758300A - Radio antenna - Google Patents

Description

Aug. 7, 1956 T. J. DYLl-:wsKl

RADIO ANTENNA Filed Aug. 25, 1951 RADIO ANTENNA Thaddeus J. Dylewski, Chicago, Ill., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Air Force Application August 25, 1951, Serial No. 243,629

Claims. (Ci. 343-845) The present invention relates to radio antennas and more particularly to antennas adapted to be operated at a number of different frequencies over a wide band of frequencies.

When the frequency `of operation of a radio antenna is varied, the e'ective series resistance and reactance at the terminals of the antenna vary cyclically, having alternate high and low values. In arrangements heretofore used and known in the art, this variation in antenna resistance and reactance with change in frequency makes it necessary to provide tuning, loading, or matching apparatus between the radio receiver or transmitter and the antenna to effect an eicient interchange of energy between the antenna and the radio receiver or transmitterfor all frequencies at which it is desired to operate the system.

An object of the present invention is to decrease resonant effects in antennas used with radio receivers or transmitters operated at a number of different frequencies which are not necesarily harmonically related.

Still another object of the present invention is to decrease the variation with frequency of the effective impedance at the terminals of an antenna operating over a wide band of frequencies.

Still another object of the present invention is the elimination of antenna tuning, loading, or matching apparatus such as ordinarily used between the radio receiver or transmitter and the antenna.

In order to overcome the necessity for the use of such additional tuning, loading, or matching apparatus, in accordance with one aspect of the present invention, I provide an antenna comprising a relatively long wire having a comparatively large spacing at one end from the ground over which it is arranged and an increasingly smaller spacing as the yother end is approached. The extremity of the wire which is widely spaced from ground is insulated from its surroundings, while the other eX- tremity of the antenna which gradually approaches the surface of the ground is electrically connected thereto. The terminals to which the associated radio transmitter or receiver (that is, the transducer apparatus) are connected are located intermediate between the widely and closely spaced portions of the antenna.

In a second arrangement, a re-entrant configuration is used wherein the extremity of the wire which is Widely spaced from ground is folded back over the other extremity which is electrically connected to ground. The feedpoint yor terminal of the antenna is then at the intersection of the widely spaced end of the wire with the grounded portion.

The present invention will be fully explained by the following detailed description with reference to the accompanying drawing in which:

Fig. l illustrates in diagramatic form an embodiment of the present invention, and

Fig. 2 shows a modification of the structure of Figure l in which the antenna has a re-entrant arrangement nited States Patent O whereby less space over the surface of the ground is occupied.

In Fig. l, the antenna conductor is indicated generally by reference numeral 10. At one end the antenna conductor 10 is supported by a tall post or mast 12. If the mast 12 is of conductive material, an insulator 14 should be interposed between the mast and the antenna conductor 10. At the other end of the conductor 10 the spacing between it and the surface of the ground indicated by ground plane GP gradually becomes less and less until at the extreme end it is conductively connected to ground as indicated at point 15. At a point near the center of the antenna conductor 10 there is connected one conductor I6 of a transmission line Which is in turn connected to the radio receiver or transmitter equipment 2t). The ground indicated by ground plane GP may be the surface of the earth, a counterpoise, an electrically conductive structure of an aircraft, ship or other vehicle, or it may be electrically conductive surfaces, frameworks or bodies in the near zone of the antenna which either jointly or severally complete the conduction circuit of the antenna.

In considering the operation of the antenna of Fig. l, it is convenient to divide it effectively into two loading portions, portion 11 being that part of conductor It) which has an increasing spacing from ground with increasing distance from the point of connection of conductor 1d and portion 13 which more closely approaches the surface of the ground plane GP w-ith increasing distance from conductor 16 until at the extreme end it is conductively connected to ground at 15. These two portions are effectively connected in parallel to the transmission line 16, but their actions will at first be considered as though each acted independently of the other. The terminal resistance and reactance of each of the parts 11 and I3 varies cyclically, having alternate high and low values as the frequency applied to the antenna is varied, but for any frequency at which part 11 has a high resistance and reactance, part 13 has a low resistance and reactance. Conversely, at any frequency where portion 1l presents a low resistance and reactance to the conductor 16, portion 13 presents high values of resistance and reactance to conductor 16. Furthermore, at most of the frequencies at which the reactance of portion 11 of the antenna is inductive, the reactance of portion 13 is capacitive, while the converse is also true.

As a consequence of this behavior of the two separate parts of 11 and 13 of the antenna conductor 10, connecting them in a parallel arrangement to conductor 16 results in an antenna having a smaller variation of terminal resistance and reactance than either of the constituent parts would have separately.

In the modification of the present invention shown in Fig. 2 the same reference numerals are applied to the corresponding individual parts as in Fig. 1. However, in this form the conductor portion 13 instead of extending along in the same direction as conductor portion ji, is folded back under conductor portion 11 at the point of connection of the transmission line 16 to the radio receiver or transmitter 20. Due to this folding back of the antenna conductor and strain insulator 24, a second antenna supporting mast 22 is required at the location of the connection `of the transmission line 16 to the antenna conductor 10. The antenna conductor 10 may be described as being in the form of a V with legs 11 and 13 converging to an intermediate junction which is connected by conductor 16 to the radio equipment 2t). Except for the economy of ground space in Fig. 2 over that of the modification of Fig. l, the operation of the antenna of Figure 2 is the same as that of Fig. l.

The antenna of this invention finds special usefulness for radio communications in the 2 to 30 megacycle frequency range. `Practical dimensions for an antenna operable in that` range are yasv follows: The length -of the antenna conductor 10 may be from 25 to 70 feet and the height of the mast 12 from 5 to 30 feet above the level of the ground plane. For installation on an aircraft, the antenna structure of Fig. 2 is preferred. The total overall length of the `antennaconductor it) wouldfremain the same, and separate arms 11 fand 13 lare nearly the same length. ln one ysuch type of installation, the antenna is mounted above the fuselage wh-ich acts asthe ground plane between 4the cabin and the rudder or vertical stabilizer assembly. The heightof the mast 12 will then be determined-by the vrudder assembly or vertical stabilizer of the aircraft, and-'the ground point 1-5 wi-llfbe at-the base of such assembly. The radio-transmitter andreceiver apparatus-can then 4lbe located in the forward part of the cabi-n of the aircraft in ythe mos-t convenient place for such installations, asdetermined by the `structure of the aircraft in which the antenna is-to beV installed.

What is claimed is:

1. A broadband antennacomprisinga conductive surface, an elongated folded conductor generally in the form of a V having -tirst and second ends andan intermediate junction, means for directlyvconnecting said first -end electrically to said conductive surface, a rst support maintaining said intermediate junction insulated from said conductive surface at a first distance therefrom, a second support maintaining said second end insulated from said conduct-ive surface at a distance from said conductive surface greater than said first distance, and a conductor from said junction for connection to a radio equipment.

2. A broadband antenna as dened in claim 1 wherein said first-end -ofrsaid-vfolded Yconductor is adjacent to -said References Cited in the le of this patent UNITED STATES PATENTS 2,027,020 Carter Jan. 7, 1936 2,207,504 Bohm,. July- 9, 1940 2,267,945 Peters Dec.30, 1941 2,275,626 Harrison Mar.r10, 1942l 2,562,296 Christensenv et al. July 31, 195 i FOREIGN PATENTS 468,001 France Apr. 10, 1914 537,312 Germany Nov. 2,1931

OTHER REFERENCES Radio Engineering, F; E. Termin, 3rd edition, 1947; McGraw-Hill Book Co., Inc., page 668.

Images