US2636122A - Antenna system - Google Patents

Description

April 1, 1953 A. c. HAYES 2,636,122

ANTENNA SYSTEM Filed April 28, 1949 v nmmm M jw w 62 azg ga Patented Apr. 21, 1953 UNITED STATES PATENT OFFICE ANTENNA SYSTEM Austin 0. Hayes, Melcher, Iowa Application April 28, 1949, Serial No. 90,083

7 Claims. (Cl. 250-33) The invention relates generally to antenna systems and, more particularly, to such a system adapted for either transmitting or receiving of relatively high frequency.

The invention has among its objects the production of :a very compact, highly efficient antenna system in which the antenna element or radiator may be considerably less than a quarter wave length of the operating frequency, whereby the same may be used in locations and under conditions which preclude the use of longer antennas.

Another object of the invention is the production of such an antenna system for use in a transmitting circuit which is capable of radiating an extremely strong and effective signal.

A further object of'the invention is the production of an antenna system which is capable of effectively receiving radio frequency signals with a reduction in undesired interference, particularly man-made electrical interference, whereby a high signal to noise ratio is achieved.

Many other objects and advantages of the construction herein shown and described will be apparent to those skilled in the art from the disclosure herein given.

The present invention is directed to an antenna construction which is particularly efficient as a transmitting antenna, in which case high voltages may be produced on the radiating element, and very efficient transmission achieved, employing a radiator of very small length. For example, in actual tests an antenna constructed in accordance with the present invention, utilizing a radiator length of from seven to twentytwo inches on a mobile transmitter operating at a frequency of approximately twenty-seven megacycles, and approximately nine watts input produced a signal which was well received in all U. S. districts, the mobile unit being in motion during the tests. Likewise, the antenna by actual test would appear to be almost as efficient when employed under ground as above ground.

In the drawings, wherein like reference characters represent like or corresponding parts:

Fig. 1 is an elevational view of an antenna structure embodying the present invention, with one side of the housing removed to disclose the details of construction;

Fig. 2 is a diagrammatic figure of the circuit embodied in the structure illustrated in Fig. 1;

Fig. 3 is an elevational view, in section, of the application of the present invention to a single antenna element; and

Fig. 4 is a diagrammatic figure of the circuit of the antenna illustrated in Fig. 3.

It is well known that the resonant frequency of an antenna may be increased by adding inductance in the antenna circuit, and may be decreased by adding capacity. However, in the past it has been considered inadvisable to load an antenna with inductance to radiate a wave more than four times the natural Wave length of the antenna, as the insertion of greater amounts of inductance would normally increase the reactance and reduce the current fiow. The present invention, however, is capable of radiating a strong wave of a length considerably in excess of four times the natural wave length of the radiator. i

Referring to the drawings, and particularly to Figs. 1 and 2, l indicates generally a housing constructed of suitable metal, as for example, aluminum, having a pair of insulators 2 and 2' mounted thereon which respectively carry an antenna element or member 3 and 3', only a portion of the latter being illustrated in Fig. l. Positioned in the housing I is a pair of inductances 4 and 4' which may be woundon suitable forms 5, one end of the inductance 4 being connected to the radiator 3, as indicated at B, and one end of the inductance 4' connected to the radiator 3, as indicated at 6'. Also positioned in the housing I is a small variable condenser, indicated generally by the numeral 1, having rotor plates 8 operatively connected to the free end of the inductance 4, as indicated at 9, with the stator plates ll of the condenser being operatively connected to the free end of the inductance 4', as indicated at H. Both the stator and rotor plates of the condenser 1 are suitably insulated from the housing I, and the effective capacity of the condenser may be varied by rotating the rotor shaft l3 by means of a suitable knob H, or the like. Inductively radiated to the respective inductances 4 and 4' is a pair of inductances l5 and [5, the latter being connected in series, as indicated at [6, with the inductances I5 and [5' in the construction illustrated encircling the respective ends of the inductances 4 and 4. The free end I! of the inductance I5 is operatively connected to a suitable terminal l8, and the free end I!) of the inductance I5 is connected to one end of an air core choke 2|, the inductance of which is such that it is resonant at approximately the resonant frequency of the antenna. The opposite end of the choke 2| in the construction illustrated is connected to the housing I, as indicated at 22.

Assuming the antenna is adapted to be connected into a transmitter circuit, a coupling loop 23, adapted to be operatively related to the output circuit of the transmitter, may be employed, one end 24 of the loop being connected to the terminal H] by a suitably shielded transmission line 25, the outer shield of which is grounded, as indicated at 25 in the transmitter circuit, with the other end 21 of the loop 23 being also connected to the shield, the latter, in turn, is grounded to the housing I of the antenna, as indicated at 28. Thus the high voltage side of the coupling loop 23 is operatively connected to the end H of the inductance [5, while the return path from the inductance I5 is through the choke 2|.

It will be noted that, in the construction above described, the loading inductances 4 and 4 and condenser 7 form a series resonant circuit. Consequently, as the inductive and capacitive reactances are equal and opposite in polarity at the resonant frequency, they balance each other, and the actual total reactance is reduced to zero. It will, therefore, be apparent that a large current flow may be produced at resonance as the impedance is a minimum, the only opposition to the current flow being that of the resistance in the circuit. Likewise, since a large current flow isobtained at resonance, the actual voltages across the inductance and capacitor may be many times the voltage applied to the circuit. Also, for frequencies below resonance, the circuit acts like capacitor plus a resistor, and for frequencies above resonance, the circuit acts like an inductor plus a resistor, so that a high impedance is offered to the flow of current other than at theresonant frequency, while a low impedance is presented at the resonant frequency.

It will also be apparent that as the return path from the inductances l5 and i5 isthrough the choke, 2|, which is substantially resonant at the transmitting frequency, the return flow of current at the transmitting frequency is opposed by the choke and, in effect, forces the radio frequency alternations through the resonant antenna circuit to build up the high radio frequency voltage therein. In actual tests, antennas of this type, employing relatively very short radiators, are capable of transmitting a very strong wave.

The present invention is equally applicable to a singlepole antenna, and such a construction is illustrated in Figs. 3 and 4, of the drawings, whereinthe reference numeral 41 indicates generally a metallic housing having, in the present instance, a cylindrical tubular portion 52 extending therefrom, an insulator 43 being mounted on the outer end M of the portion 32. Positioned in the portion d2 of the housing is an inductance 45 which may be wound upon a suitable form 48, the upper end 41 of the inductance being operatively connected to a single antenna element or radiator 48 by means of the connecting member 49, the opposite end 5| of the inductance 45 being connected to the stator plates 53 of a variable condenser 52, the rotor plate 54 thereof being grounded to the housing 4! through the condenser frame 55, which is not insulated from the housing. The efiective capacity of the condenser 52 may be varied by rotating the shaft 56 of the condenser by means of a suitable knob 51, or the like, whereby the circuit may be tuned to resonance at the desired frequency. Inductively related to the inductance and, in the present instance, illustrated as being positioned within the latter is a second inductance 58,

the latter being suitably supported by a member 59 of suitable insulating material extending across the lower portion of the housing 4| and rigidly secured thereto by brackets BI, or other suitable means. The end 62 of the inductance 58 is operatively connected to a suitable terminal 63 by a conductor 64, while the other end 65 of the inductance is connected to ground through an air core choke E6, the free end of the latter being connected to. the housing 4!, as indicated at 51.

Assuming the antenna is to be used as a transmitting antenna which may be coupled to the transmitter by means of the transmission line 25 and coupling loop 23, heretofor described, whereby the side 25 of the loop 23 is connected to the inductance 58, and the other side 27 of the loop grounded to the housing ii. It will be noted that, as in the twin element construction, a series resonant antenna circuit is employed and, in like manner, a choke is inserted in the return path of the coupling inductance, so that, in operation, the same advantages are achieved with the main difference being that the first construction is, in effect, two single antenna elements operated out of phase.

The inductances and capacities employed in any particular instance will, of course, depend upon the desired frequency size of the shield housing, etc., and all conductors are insulated by suitable material, as required. While the length of the radiators is not critical, I have found-that excellent results may be obtained on the various frequencies with radiators of the length specified in the following table:

Frequency in Megacycles Radiator Length,

22" each (2) used. 17%. 36".

66"bach (2) used. 50".

Likewise, the size or shape of the radiator or antenna element may be considerably varied, and may be straight, circular, spherical, or bent, or may be in the form of a gaseous tube as may be desired for a, particular application. Similarly,

ter or receiver, in which case the housing may form a part of thehousing or cabinet of such transmitter or receiver.

The directional characteristics ofgthe antenna may be varied by the use, of director or reflector elements. and the antenna construction illus-- trated in Figs. 1 and 2 would appear to have marked directional characteristics. For example, if the radiators 3 and 3' are bent, as indicated in dotted lines in Fig. 2, av very directional signal may be obtained in the direction of the dotted arrows in Fig. 2, in which case. the radiators 3 and 3 would be bent at an angle of. approximately fifty degrees.

fhe system is also very effective for receiving signals, as Well as the transmission thereof, and

would appear to have a very marked action in the.

reduction of interference, particularly local electrical interference, and the like, with anincrease in the signal strength at the particular frequency at'which the antenna is resonant achieving a very high signal to noise ratio.

1 While the above description of the present invention, and the method of operation set forth may, in part, account for the high efficiency of 'such antenna, the phenomena responsible for the exceptional results obtained is not fully understood at the present time. It may be possible that the transmission of radio waves with the present antenna involves concepts heretofor not considered in connection with previous type of transmission of radio waves, whereby possibly a closer matching of atmospheric resistance, or the like, is achieved with the waves propagated possibly being of greater similarity to the natural waves always present between the earths field and outer space.

7 Having thus described my invention, it is obvious that various immaterial modifications may be made in the same without departing from the spirit of my invention; hence, I do not wish to be understood as limiting myself to the exact form, construction, arrangement, and combination of parts herein shown and described or uses mentioned.

What I claim as new and desire to secure by Letters Patent is:

1. In an antenna system, the combination of a pair of electrically conductive antenna members operating out of phase, a ground therefor, a pair of inductances, each arranged in series with a respective antenna member, a variable capacitor operatively positioned between said inductances and connecting said inductances in series and operative to tune the circuit so formed to the desired operating frequency forming a, series resonant circuit, a second pair of inductances each closely coupled inductively to a respective first mentioned inductance whereby a high voltage is produced on each of the antenna members, said second pair of inductances being connected in series and adapted to be operatively connected to a radio signal device, and a choke operatively connected through said shielded transmission line in series with one of said second inductances and said signal device, said choke being resonant to approximately the desired operating frequency, whereby effective transmission of radio frequency signals is obtained.

2. In an antenna system, the combination of a pair of electrically conductive radiating elements operating out of phase, each having a physical length substantially less than a quarter wave length of the desired operating frequency, a ground therefor, a pair of inductances, each arranged in series with a respective radiating element, a variable capacitor operatively positioned between said inductances and connecting said inductances in series forming a. series resonant circuit and operative to tune the circuit so formed to the desired operating frequency, a second pair of inductances each closely coupled to a respective first mentioned inductance whereby a high voltage is produced on the radiating elements, a shielded transmission line operatively connected to the ground, said second pair of inductances being connected in series and adapted to be operatively connected through said shielded transmission line to a radio signal device, and a choke operatively connected in series with one of said second inductances and such signal device, said choke being resonant to approximately the desired operating frequency, whereby efficient 6 transmission is obtained employing radiating elements substantially less than a quarter wave length.

3. In an antenna, system, the combination of an electrically conductive antenna member, a ground therefor, an inductance and a variable capacitor arranged in series with said antenna member and operatively connected to ground, operative to tune the circuit so formed to the desired operating frequency, a shielded transmission line, a second inductance inductively coupled to the first mentioned inductance, whereby a high voltage is produced on the antenna member, and adapted to be operatively connected to a radio signal device through said shielded transmission line, and a choke operatively connected in series with said second inductance and to ground, said choke being resonant to approximately the desired operating frequency, whereby efficient transmission is obtained.

4. In an antenna system, the combination of an electrically conductive antenna member, having a physical length substantially less than a quarter wave length of the desired operating frequency, an inductance and a variable capacitor arranged in series with said antenna member, operative to tune the circuit so formed to the desired operating frequency, a second inductance inductively coupled to the first mentioned inductance, whereby a high voltage is produced on the antenna member, and adapted to be operatively connected to a radio signal device, and a choke operatively connected in series with said second inductance, said choke being resonant to approximately the desired operating frequency, whereby efiicient transmission is obtained employing an antenna member substantially less than a quarter wave length.

5. An antenna structure comprising, in combination, a laterally spaced pair of electrically conductive antenna members, insulators for mounting th antenna members, a housing for mounting the insulators, a pair of inductances mounted within the housing, each inductance connected to its contiguous antenna member, a variable condenser mounted within the housing and connected in series between the inductances, and operative to tune the circuit so formed to the desired operating frequency forming a series resonant circuit, a second pair of inductances mounted within the housing and about the first pair of inductances, and closely coupled inductively to a respective first-mentioned inductance, said second pair of inductances being connected in series and adapted to be operatively connected to a radio signal device, and a choke positioned within the housing and operatively connected in series with one of said second inductances and said signal device, said choke being resonant to approximately the desired operating frequency.

6. A directional antenna structure comprising, in combination, a laterally spaced pair of angularly bent, electrically conductive members, each member comprising a, straight portion and a bight portion formed at an angle thereto, insulators for mounting the antenna members, a housing for mounting the insulators, a pair of inductances mounted within the housing, each inductance connected to its contiguous antenna member, a variable condenser mounted within the housing and connected in series between the inductances, and operative to tune the circuit so formed to the desired operating frequency forming a series resonant circuit, a second pair of inductances mounted within the housing and about the first pair of inductances, and closely coupled inductively to a respective first-mentioned inductance, said second pair of inductances being connected in series and adapted to be operatively connected to a radio signal device, and a choke positioned within the housing and operatively connected in series with one of said second inductances and said signal device, said choke being resonant to approximately the desired operating frequency, whereby a directive antenna structure is obtained having a straight portion and bight portions formed at an angle to the straight portion and lying in the same plane.

7. An antenna structure comprising, in combination, an electrically conductive antenna member, an insulator for mounting the antenna member, a housing having an elongated portion for mounting the insulator, an inductance mounted within the elongated portion of the housing and connected in series with the antenna member, a variable condenser mounted within the housing and connected in series with the inductance, operative to tune the circuit so formed References Cited in the file of this patent UNITED STATES PATENTS Name Date Bethenod Sept. 9, 1924 Batsel Feb. 17, 1925 Schafier Nov. 5, 1930- Van Arco Jan. 5, 1932. Newman Apr. 12, 1938 Landon Nov. 1, 1938 Crossley Nov. 19,1940 Roosenstein May 13, 1941. Lake et a1. July 15, 1947 Number

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