US2640192A - Shiftable directional antenna - Google Patents

Description

May 26, 1953 N. MARCHAND 2,640,192

- SHIFTABLE DIRECTIONAL ANTENNAS Filed sept. 11, 1944 A I @QQ-#f f2 2 Sheets-Sheet l @ECE/VER zag @www

N. MARCHAND SHIFTABLE DIRECTIONAL ANTENNAS May 26, 1953 2 Sheets-Sheet 2 Filed Sept. 11, 1944 Two PMSF GEM @ 9 Moro@ A/Fflf/C/HL L INE INVENTOR. ,vnr/1.4m Hamm/0 from? Patented May 26, 1953 UNITED STATE 'ENT OFFICE SHFTABLE DI RECTIONAL ANTENNA Application September 11, 1944, Serial'No. 553,562

claims. l

This invention relates to direction finders and more particularly to radio direction finders in which the directive action is shifted without rotation of the antennas.

In `directionallv shiftable radiant acting systems, used either as direction finders or as rotary beacons, systems have been proposed wherein rotation of the `directive action of the system is effected without rotation of the antennas by ro tatablc goniometer couplings.

It lis an object of my invention to provide a drectionally shiitable radiant acting system in which the directive pattern is shifted through a predetermined angular relationship by means of a phase lshifting network shifting the phase relationship of two or more antenna means with respect to a given receiver. y

`It is a further object of my invention to provide a phase shifting 'network in a line intern connecting `two radiant acting members, which produces a phase shift as a .substantially sine wave function, whereby uniform shifting of the resultant radiant action independent of frequency is obtained.

It is `a further object of my invention to provide a .directionally shiftable radiant acting systemV in which a null or a maximum directional indicating radiation maybe rotated through 360 or less by means of phase shifting :arrangements coupling theantennasto a translating apparatus with `variable phase relationship between the energy in `two or more spaced antennas.

"It `is a still further object of my .invention to provide a transmission line means interconnectn ing two antenna means together with an arrangey ment for continuously and cyclically shifting a coupling point along this transmission line means to couple the antenna means to ,a translator unit in variable phase relationship.

According to a feature of my invention, I interconnect two antenna units by meansiof a transmission line. Each of 'the antenna units or groups of units is coupled to the transmission line in impedance matching relation. In the coupling line .-is provided a phase shiftable coupler .for coupling the `antenna units to a translating apparatus in variable .phase relationship. `ln the output Vof the translator arrangement may be provided an indicator producing a trace line positioned `in accordance with the positioning of the variable phase coupler and means for applying energy `from Athe output of said translator to said indicator to produce .deflection of the trace in accordance with the strength of the signals.

`Preferably the phase shifting of the coupler is I sine Wave function, or with the scale calibrated in accordance with such `a function. The rst expedient however is preferred as it will provide uniform receptive sensitivity in the antenna structure.

A better understanding of my invention and the objects and features thereof may be had from the `particular description thereof made with reference to the accompanying drawingsy in which:

Fig. 1 is a block diagram of a simple receiver unit operating in accordance with the principles of my invention;

Fig. 2 is a set of polar diagrams used in explaining the operation of the circuit in Fig. 1;

Fig. 3 is a modified arrangement of the direction finder unit illustrated in Fig. 1;

Fig. 4 is a modified direction iinder system in accordance with my invention for producing a directional indication without ambiguities; and

Fig. 5 is a set of polar diagrams illustrating the operation of the circuit of Fig. 4.

Turning rst to Fig. 1, two antennas l and 2 are shown interconnected by a transmission line 3. Antennas l and 2 are spaced apart a given distance S, S preferably less than electrical degrees. Antennas l and 2 are coupled to line 3 over impedance matching networks and 5, respectively. Since the sharpest indication of direction may generally be produced by a null indication, I preferably provide a transposition 6 in line 3. Thus at the mid coupling point between antennas I and 2, there will normally be a zero or null providing the signal is approaching at right angles to the plane defined by antenna sys;

tems. If the signal comes at some other angle so that antennas l and 2 are not energized in phase, the null will occur at some other point along the line. Midway of line 3 intermediate the ends thereof I' provide a phase shifting net` work l' which may consist of an artificial line 8 together with movable Contact connections 9. Artificial line 8 is preferably made electrically equal to the spacing between antennas l and 2 so that a complete effective rotation of the directive action of the system may be obtained.

Contacts 9 'are connected over a coupling line I 9 to a receiver I I in the output of which is provided an indicator I2. Preferably indicator I2 is some form of visual indicator arrangement such as a cathode ray'tube I3 provided with deflecting means su-ch as coil M. Drive means I5, which may for example be a motor, is coupled over a shaft I5 to a driving wheel I1 and over a shaft I8 to a control means indicated by arrow I9 for rotating deection coil means I4 about the cathode ray tube I3. Mounted on wheel I1 is a crank which serves during rotation of wheel I1 to shift contacts 9 regularly backward and forward along artificial line 8. lf drive means I5 operates continuously at a given speed, contacts 9 will travel back and forth along artificial line 8 at a speed corresponding to a simple harmonic motion. Accordingly, the phase angle of the energy transferred from antennas I and 2 will continuously and cyclically be varied. This operation, because of a simple harmonic motion, will provide an output substantially in the form of la sine Wave so that effective regular rotation of the directive action of the pattern from antennas I and 2 will thus be effected. Since coil I4 rotates in synchronism with the movement of contacts 9, radial deflection of the cathode ray beam will be made in accordance with the incoming signal energy so a pattern dependent upon the direction of a transmission station will be traced on the screen of the cathode ray tube. Since the displacement is uniform about the screen la permanent calibration maybe provided. With the relationship outlined, the direction indications will be uniform for all frequencies received.

Turning now to Fig. 2, the pattern 2| correspends to the energy applied to receiver I I from a transmitting station located at rig-ht angles to the plane of the antennas I and 2 and on line with the center of radiant action of this system during one complete cycle of phase shift. It will be seen that in this arrangement a null is located at a position which may be considered zero direction indicating action. If the transmitting station is located at substantially a 45 angle to the line interconnecting antennas I and 2, a pattern such as shown at 22 of Fig. 2 will be traced. Here it will be seen there are produced two nulls at substantially 40 and 140 degrees from zero. If a transmitting station is located at a position in line with the two antennas I and 2 then pattern 23 of Fig. 2 having a single null at a 90 angle will be produced. Thus, as the contacts 9 move backward and forward along artificial line 8, an effective rotation of the null direction indication will be obtained. If then on the indicator I3 the trace line is at the greatest deflection in the absence of signal, a pattern such as shown at 25 of Fig. 1 may be traced by a station located 45 from the line connecting the two antennas. It will be noted that the directional indication for zero null has a 180 ambiguity while when the null is at 90 there is no ambiguity. Intermediate these patterns there will be an ambiguity in indication Varying between zero degrees and 180. The ambiguity may be avoided if desired by some form of sensing indication.

If it is desired to use the maximum indication instead of a minimum for the directional system, two spaced antenna means 29, 21 may be interconnected by a transmission line 3 and impedance matching networks 4 and 5 as shown in line 3 and an artificial line 8 together with the movable contacts 9. However, in this case no transposition is provided in transmission line 3 so that in the plane midway between antennas 26 and 21 the energy will arrive in phase at receiver II. Accordingly, a maximum indication rotatable similarly to the null of Fig. 1 will be obtained. Vertical dipoles have been shown instead of the horizontal dipoles of Fig. 1. It should be understood that any desired form of antenna may be used in either case.

As the contacts 9 are shifted forward and backward across articial line 8, the phase of the energy from the two antennas as applied to the receiver is varied. Unless the antenna units are impedance matched with respect to transmission line 3, standing wave reflection will be Set up on the line 'obscuring the null. Accordingly, im-

pedance matching networks preferably are pro- 1 vided in order that a correct indication may be obtained.

Since the ambiguity present in the systems illustrated in Figs. 1 and 3 may be undesirable, a preferred type of direction nder in which ambiguity is overcome as shown in Fig. 4V may be provided. According to Fig. 4, there is provided one pair of antennas I, 2 coupled over line 3, artificial line 8 and movable brushes 9 to receiver Il' At the same time, two other antenna units 28, 29 are coupled over line 30, artificial line 3l and movable brushes 32 through a phase shifter 33 to the output of receiver Il. Since brushes 9 and 32 are simultaneously moved by rotatable drive wheel I1 through the co-operation of crank 29, lines 8 and 3| are simultaneously scanned but in relatively opposite directions. Thus two patterns shifted with respect to one another are produced. The output energy from brush 32, however, is shifted a further 90o to bring it into phase opposition with energy from brush 9 at the input of receiver I I if a null indication is desired. In this case, when a' null is produced along the zero axis of antennas I, 2, a single null across the 90 axis will be produced in the line from antennas 28, 29. 'These nulls added together will produce resultant pattern 34 of Fig. 5 having a single or unidirectional null.

Similarly, if a null is produced at a direction of 40 to the plane of antennas I, 2, the two outputs from the antenna pairs added together will produce a pattern such as shown at 35, Fig. 5, having a single null in that direction.

Returning to Fig. 4, the indicator I2 is shown .as a cathode ray tube having plate deflecting electrodes 36 instead of the rotatable coil I4 shown in the arrangement of Fig. 1. Accordingly, the output of receiver Il is coupled through coupler arrangements 31, 38 lto the vertical and horizontal deflecting plates, respectively, ofthe indicato-r. A driving motor 39 serves simultaneously to drive disc I 1 and a two-phase generator 40. The output of two-phase generator 40 is applied across the vertical and horizontal electrodes of indicator I2 by means of lines 4I and 42. It should be apparent that any type of deection system may be used in any of the circuit arrangements illustrated. Likewise, any type of antenna units desired may be provided. Furthermore.' the rotation o-f a pattern from two antennas is not the only possibility since any one vor all of the antennas illustrated in the figures may be replaced by directional arrays if desired. It should further be understood that contact brushes 9 and 32 may be capacitively coupled to the receiving artificial lines if desired rather than being connected directly. Furthermore, it should be clear that the system illustrated, the contact resistance will not cause a shifting in the null even though they differ on the two pairs of and shift between energy lin said coupling means applied to said receiver means to produce a substantially unidirectional received radiation e'ect.

16. A direction nder system according to claim 15, wherein said antenna means are spaced apart a distance not greater than 180 electrical degrees, and wherein said artificial transmission line has an electrical length substantially equal to the spacing between said antenna means.

17. A directional shiftable radiant acting system, comprising two spaced radiant acting means, coupling means for coupling said radiant acting means together, a radiant energy translating means, phasing means for coupling said translating means to said coupling means in variable phase relation with respect to said two spaced radiant acting means for shifting the directive characteristic of said radiant acting system and means for cyclically controlling said phase shifter means in accordance with a sine wave function.

18. A radio finder system comprising two spaced antenna means, a transmission line means interconnecting said spaced antenna means, a radio receiver means, artificial transmission line means interposed in said transmission line means intermediate the ends thereof, means continuously variably coupling said receiver means to said articial transmission line along different points thereof to couple said receiver in variable phase with respect to said two antenna means, first driver means for cyclically adjusting said variable coupling means, indicator means coupled to the output Iof said receiver means, second driver means operating synchronously with said cyclically adjusting means for producing a trace indication on said indicator and means responsive to energy applied to said receiver for producing a deflection of said trace one of said driver means operating to produce a sine wave function.

' 19. A direction nnder system according to claim 18, wherein said antenna means are spaced apart a distance not greater than 180 electrical degrees, and wherein said articial transmission line has an electrical length substantially equal to the spacing between said antenna means.

20. A radio direction finder comprising' two pairs of spaced antenna means arranged mutually at right angles to one another, separate transmission lines interconnecting the antennas of each pair, artificial transmission lines, each having an electrical length substantially equal to the spacing between corresponding antenna means, interposed intermediate the ends of said antenna means, a receiver means, variable coupling means for variably coupling said receiver imeans to variable points along said articial transmission lines, means for adjusting said coupling means simultaneously in different senses to provide for energy transfer from said different antenna means pairs to said receiver means in different phase relationship, means for producing a further relative phase shift between energy in said coupling means applied to said receiver means to produce a substantially unidirectional received radiation effect and means for cyclically adjusting said variable coupling means according to a sine wave function.

NATHAN MARCHAND.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,667,792 Martin May 1, 1928 1,806,755 Hansell May 26, 1931 1,821,386 Lin-denblad Sept. 1, 1931 2,173,858 Pierce et al Sept. 26, 1939 2,263,377 Busignies et al Nov. 18. v194.1

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