US2761134A - Means for operating antennas - Google Patents

Description

1956 J. M. TEWKSBURY ET AL 2,761,134

MEANS FOR OPERATING ANTENNAS Filed Jan. 18, 1952 I 3 Sheets-Sheet 1 FIG. E

ll l3- '2 as 33 I9 I PULSE 4 RECVR 32 GEN 34 Q 3 humus cur v *ol=r 3o I? 29 2a EF 2 DEFLEC- l I TION AMPLR SAW I GEN M I I o DEFLEC- 1 I now Q AMPLR i L INVENTORS JOHN M.TEWKSBURY PPI S EE GEN ALFRED AHEMPHILL ATTORNEYS Aug. 28, 1956 J. M. TEWKSBURY ET AL 2,761,134

MEANS FOR OPERATING ANTENNAS Filed Jan. 18, 1952 3 Sheets-Sheet 2 FIG. 3

MAGNETIZATION CURVE CYCLE I INVENTORS JOHN M.TEWKSBURY ALFRED A. HEMPHILL haw/24%;

ATTORNEYS Aug. 28, 1956 J. M. TEWKSBURY ET 2,761,134

MEANS FOR OPERATING ANTENNAS Filed Jan. 18, 1952 3 Sheets-Sheet 3 FIG. 6

INVENTORS JOHN M. TEWKSBURY ALFRED A.HEMPH|LL f wwawmaluzif ATTORNEYS Unite States Patent L'IEANS FOR OPERATING ANTENNAS John M. Tewksbury and Alfred A. Hemphill, Baltimore,

Md., assignors to Bendix Aviation Corporation, Towson, Md., a corporation of Delaware Application January 18, 1952, Serial No. 267,093

4 Claims. (Cl. 343121) This invention relates generally to electric antennas and more particularly to a new method and means for operating such antenna elements in the neighborhood of resonance so as to produce in a simple and efficient manner results which have been heretofore unattainable.

It is well known that electric antennas have operational characteristics which are critically dependent upon the physical dimensions of the radiating elements and the circuit and space parameters associated therewith. Many prior art antenna systems have been devised which rely for their operation upon specific proportions and arrangements of radiating elements and upon the adjustment or variation of these and other circuit parameters for attaining the desired performance.

A Well known arrangement of this general type is the Yagi antenna array. In the Yagi array, a highly directive unidirectional radiating pattern is obtained by the use of parasitic radiating elements commonly referred to as directors and reflectors. By interchanging the directors and reflectors, a mirror image of the radiating pattern will be obtained.

Other antenna systems provide means for energizing all of the elements in the system. With the proper physical arrangement of elements and the proper phase relationship of the signals radiated therefrom, it is possible to provide a rotating radiating pattern.

The above described arrangements present certain limitations or inherent characteristics that are at times undesirable. The Yagi antenna system is limited to one of two possible positions of the radiating pattern, while if the latter systems are to provide rotating patterns, energy must be provided to all of the elements. Providing energy to all of the elements necessitates providing signal carrying leads thereto. These additional leads, because of the physical displacements of the elements with respect to each other, cannot at all times be arranged such that the field does not affect the signals contained therein.

The present invention provides an antenna system that does not have these limitations. In this system, a rotating radiating pattern is provided that has the highly directive characteristics and parasitic elements of a Yagi antenna array and the controllable rotational characteristics of an antenna system that has individually energized radiating elements. In effect, a rotating pattern is produced by electronic means that is equivalent to the rotating pattern that is obtained by physically rotating a Yagi antenna array.

The particular embodiment of the invention as depicted in the drawings provides, in the antenna elements, variable impedances which directly affect the performance thereof in the neighborhood of resonance. By the particular physical arrangement and control of the variable impedances to be explained in discussing the drawings, the parasitic elements have their electrical lengths sequentially varied to produce, in effect, a rotating Yagi antenna array.

It is accordingly an object of this invention to provide 2 an antenna system for producing a rotating radiating pattern.

A further object is to provide an antenna system for producing a rotating radiating pattern that is highly sensitive and directive in nature.

A still further object is to provide an antenna system for producing a rotating radiating pattern that does not necessitate providing energy to nor receiving energy from more than one element in the system.

These and other objects of the invention will be more clearly understood by reference to the following detailed description taken in conjunction with the following .drawings wherein:

Fig. 1 is a plan view of an electric dipole having a controlled reactance element;

Fig. 2 is a view representing a system in accordance with the invention;

Fig. 3 is a diagram showing magnetic properties;

Fig. 4 is a plan view of the antenna system of Fig. 2 showing the pattern;

Fig. 5 is a diagram of received signal voltages; and

Fig. 6 is a perspective view of the direction finder of Fig. 2.

Referring to Fig. 1, there is shown a center fed dipole 11 having a centrally connected inductance coil 12. The inductance coil 12 has at least a portion thereof wound on a core 13, the permeability of which is a factor in determining the total value of inductance in the antenna. The antenna assembly 1112 is provided with suitable signal frequency energy coupling means, as for example a coil 14, coupled to a portion of the coil 12 which is not wound on the core 13, the coupling, therefore, being independent of the value of the permeability. Also wound on the core 13 is a permeability control coil 15 which is energized by a low frequency current from a suitable source 16. The value of the current may be controlled by means of a rheostat control 17.

The core 13 is composed of a suitable high frequency permeable material which provides a relatively high value of permeability, the value of which varies with the degree of saturation flux present in the core. Such characteristics are provided, for example, by dust iron core material or preferably from the class of materials known as ferrites, for example, as Stackpole Ceramag 4.

In the operation of the antenna of Fig. l, signals are coupled to or from the antenna coupling coil 14, respectively, as the device is used for transmission or reception. By the adjustment of the control 17 the value of inductance of the coil 12 may be selected within predetermined limits in response to the degree of saturation of the core 13 due to the saturating current in the coil 15. The antenna assembly 11-12 is thus brought into any desired degree of resonance by means of an electrical control condition. Obviously, the tuning control 17 could be ganged with tuning controls in other portions of the transmitter or receiver circuits in a manner to secure the desired correspondence between all of the tuned elements and circuits. In like manner the tuned antenna of the invention can be employed in automatic or in signalseeking tuner applications since tuning may be accomplished under the control of an electrical condition and without mechanical adjustment in the vicinity of the antenna structure.

Referring to Fig. 2, there is shown a ground-based direction finder system in accordance with the present invention. The vsystem comprises a center antenna system 19 similar to that of Fig. 1 and four radially disposed parasitic antenna elements 21, 22, 23, 24 having approximately A/S spacing from the center antenna 19. The parasitic elements .2l-.-24 are similar to the system 19, except that no signal coupling means are employed to derive energy by direct circuit therefrom. The saturation coils of the even and odd numbered parasitic element pairs are connected to different phases of a generator having sinusoidal output voltages which are in 90 phase relation. The connections to the coils of a pair are oppositely phased so that diametrically arranged elements are energized with 180 phae relation. Tuning adjustments 26-, 27 are provided for initially setting the saturation current for each pair of the elements 21-24, together with such trimming adjustments 28, 29 as are required to initially adjust the individual elements 21-24 to suitable operating points on the magnetization curves of the cores thereof. Adjustable resistors 28, 29 may be duplicated in opposite saturation circuits of each pair, if required.

The output voltages of the generator 25 are applied to a P. P. I. sweep generator 31, the outputof which is applied to control the sweep of a cathode ray indicator 32., This sweep provides a radial line presentation on the indicator which rotates at a frequency equal to that of the generator 25. The indicator 32 is normally biased to cutofi so that no indication appears except as hereinafter described.

The signal frequency energy received by the central antenna 19 is coupled to a receiver 33. The receiver 33 is provided with a tuning control 34 which may be ganged with a saturation tuning adjustment of the antenna 19, and if desired, by suitable linkage to the controls 26, 27. With this arrangement, tuning the receiver will adjust antenna 19 to resonance at the receiver frequency and also the elements 21-24 for the condition of zero saturation current from the generator 25. Signals from the receiver 33 are supplied to a pulse generator 35. The pulse generator 35 provides a pulse output which bears a predetermined phase relation to the amplitude variations of the output of receiver 33 which are due to the rotation of the antenna pattern, as will be more fully explained hereinafter.

The operation of the system. of Fig. 2 will be described with reference to Figs. 3 and 4. represents the incremental permeability of the core material employed, for various values of the magnetizing force H. An operating point P0 is established on the curve for each core in the antenna 19 and parasitic ele- In Fig. 3 the function p.

ments 21-24 by means of, the D. C. controls 26-29.

I, as a director or reflector and, since its diametrical opposite element is saturated with 180 phase relation, an aiding reflector and director condition obtains. For this condition a maximum reception direction exists along the diameter of the oppositely phased elements as shown in Fig. 4 by antenna pattern 36. As the current from generator 25 varies sinusoidally in the saturation coils of the parasitic elements, the directive pattern 36 rotates as indicated by the arrow. This rotation occurs due to the phase of the saturation currents in the parasitic elements 2124. From the condition depicted at 36 in Fig. 4 the. currents change in a manner to reduce the directivity of element22 and increase that of element 23. correspondingly the reflectivity of element 24 is reduced and that of element 21 increased. These actions combine to direct the radiation pattern in a position intermediate the elements 22, 23 as shown by pattern 36'. After a 90 time interval from the instant the pattern is directed as shown at 36 the radiation will be directed along the diameter through elements 21, 23 and in the direction of element 23. Thus, it can be seen that a progressive rotation of the antenna directivity occurs throughout 360 in space for-each cycle of the generator 25. Inasmuch as no mechanical motion is involved in the antenna structure, the speed of pattern rotation may be made quite high, thus giving substantially continuous information from relatively fixed sources, such as aircraft.

The rotation of the antenna pattern as shown in Fig. 4 results, as shown in Fig. 5, man output signal 37 in the receiver 33 for a single fixed radio signal source. This signal 37 occurs as the antenna pattern 36 sweeps over a line joining the antenna 19 and the aircraft source. By suitably establishing a direction convention for the radial sweep of the indicator 32 an intensified radial sweep may be obtained to indicate the direction of the source. This result may be accomplished by pulses produced from the pulse generator 35 for each peak value of the signals 37 of predetermined amplitude to produce the desired indication on the indicator 32.

Referring now to Fig. 6, there is shown a mast 33 supporting a ground plane quarter-waverantenna 19 and the parasitic elements 21-44. The parasitic elements are mounted in housings 39 which contain the saturation cores 13 as shown in the cutaway view of element 22. Radio frequency energy is coupled to the antenna 19' by means of a suitable transmission line 41 and saturation currents to all control coils are supplied by means of multiconductor cable 42. It will be apparent that this arrangement provides an antenna system which is immune from difficulties due to a horizontal polarization component of the received wave, since no horizontal projections are coupled to the line 41 at radio frequencies.

Obviously, many modifications can be made in the light of the above teachings without departing from. the spirit and scope of the present, invention. These principles may be incorporated in other Well known parasitic or driven array configurations and are not limited to the present particular embodiment, here shown by way of example. Certain applications may require the use of a carrier wave of, say, 10,000 C. P. S. for the saturation signal in a manner which is well known as, for example, in the magnetic tape recording art.

What is claimed is:

1. A radiant energy transducer system for producing a rotating directive pattern, comprising: a central vertical antenna; an even number of identical parasitic antenna radiators; said number being at least four; means associated with each of the said radiators providing control of the electrical length thereof; said radiators being symmetrically disposed in a circle about the said antenna; a second means; said second means operating upon each of said control means in a manner such that the said electrical lengths of the said radiators that are diametrically disposed with respect to one another are varied in phase opposition; the phase displacements between the variations of the said radiators being equal to the angular physical displacement therebetween; a radio frequency signal means; and means for cotiplingradio frequency energy from the said antenna to the last said means.

2. A radiant energy transducer system for producing a rotating directive pattern, comprising: a central vertical antenna; an even number of identical parasitic antenna radiators; said number being at least four; means associated with each of the said radiators providing control of the electrical length thereof; said means comprising variable lumped reactors; said radiators being symmetrically disposed in a circle about the said .antenna; a second means; said second means operating upon each of said control means in a manner such that the saidelectrical lengths of the said radiators that are diametrically disposed with respect to one another are varied in phase opposition; the phase displacements between the variations of the said radiators being equal to the angular physical displacement therebetween; a radio frequency signal means; and means for coupling radio frequency energy from the said antenna to the last said means.

3. A radiant energy transducer system for producing a rotating directive pattern, comprising: a central vertical antenna; an even number of identical parasitic antenna radiators; said number being at least four; means associated with each of the said radiators providing control of the electrical length thereof; said means comprising inductance coils having variable permeable cores with saturating windings thereon; said radiators being symmetrically disposed in a circle about the said antenna; a second means; said second means operating upon each of said control means in a manner such that the said electrical lengths of the said radiators that are diametrically disposed with respect to one another are varied in phase opposition; the phase displacements between the variations of the said radiators being equal to the angular physical displacement therebetween; a radio frequency signal means; and means for coupling radio frequency energy from the said antenna to the last said means.

4. A radiant energy transducer system for producing a rotating directive pattern, comprising: a central vertical antenna; an even number of identical parasitic antenna radiators; said number being at least four; means associated with each of the said radiators providing control of the electrical length thereof; said means comprising inductance coils having variable permeable cores with saturating windings thereon; a signal generating means; means coupling the said generating means to the said References Cited in the file of this patent UNITED STATES PATENTS 2,072,267 Kramar Mar. 2, 1937 2,199,819 Galle May 7, 1940 2,212,245 Perroux Aug. 20, 1940 2,238,261 Hahnernann Apr. 15, 1941 2,254,943 Galle Sept. 2, 1941 2,419,987 Carlson May 6, 1947 2,581,348 Bailey Jan. 8, 1952 OTHER REFERENCES Radio Craft for July 1939, pages 13 and 51. Tuning with a Rheostat, by G. Leithauser and H. Boucke.

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