US3480958A

US3480958A - Electronic scanning antenna

Info

Publication number: US3480958A
Application number: US597805A
Authority: US
Inventors: Pierre Tcheditch
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1965-11-29
Filing date: 1966-11-29
Publication date: 1969-11-25
Anticipated expiration: 1986-11-25
Also published as: NL6616784A; FR1570415A; DE1541469A1; DE1541469B2; GB1175365A

Description

1959 1 P. TCHEDITCH 3,480,958

ELECTRONIC SCANNING ANTENNA Filed Nov. 29. 1966 5 Sheets-Sheet 1 E. [D TPJMYM/ au uxm RECE/VER PR/O/Q ART Fig. 1

N 5. 1959 P. TC-HEDITCH ELECTRONIC SCANNING ANTENNA 5 Sheets-Sheet 5 Filed Nov. 29. 1966 Nov. 25, 1969 P. TCHEDITCH 354809958 ELECTRONIC SCANNING ANTENNA Filed Nov. 29. 1966 5 Sheets-Sheet 4 (N/71901150 7r P/llIf-JH/FTER P/Mif-JH/FT CONT POL I i I I I b b RECEIVER United States Patent 3,480,958 ELECTRONIC SCANNING ANTENNA Pierre Tcheditch, Paris, France, assignor to CSF- Compagnie Generale de Telegraphic Sans Fil, a corporation of France Filed Nov. 29, 1966, Ser. No. 597,805 Claims priority, application France, Nov. 29, 1965,

Int. Cl. (301s 9/02 U.S. Cl. 343-16 Claims ABSTRACT OF THE DISCLOSURE In a transmit receive system comprising an electronic scanning antenna formed by a network of elementary sources and associated phase-shifters, the conventional T-R switch is replaced by the combination of at least one four arm balanced junction and 1r phase-shifting means.

The present invention relates to electronic scanning antennae formed by a network, having one or two dimensions of sources or elementary antennae. These sources are, for example, supplied from a single transmitter through a power distribution system, The feeder of each source contains a device for electronically controlling its phase.

A phase gradient may be thus established along the network, for adjusting the direction of the main radiation lobe of the antenna.

The technique for connecting the antenna alternately to the transmitter and to the receiver generally consists in using a nonreciprocal device, generally called T-R switch which carries out a switching either on the receipt of an external order, or automatically if the non reciprocity is obtained by using a difference in the characteristics of the transmission and reception waves. Generally, gasfilled tubes or ferrite or semiconductor devices are used.

In all cases the T-R switch is subjected to the action of the whole of the transmitted power, and this requires a complicated bulky and costly device which is very difficultly built.

It is an object of this invention to provide a novel device for connecting the sources of an electronic scanning antenna and effecting the transmission-reception switching without using any T-R switch.

According to the invention, there is provided a transmit-receive system comprising: transmitting means having a sync output and a signal output, receiving means having a signal input; aerial means comprising a first plurality of radiating sources and controllable phase-shifters, said plurality having a first terminal and a second plurality of radiating sources and controllable phase-shifters, said second plurality having a second terminal; programming means for controlling said phase shifters, having a first plurality of outputs coupled to said phase-shifters of said first plurality, and a second plurality of outputs coupled to said phase-shifters of said second plurality; and a coupling circuit for alternately coupling said signal output and said signal input to both said terminals, said circuit comprising a balanced hybrid junction having a first, a second, a third and a fourth arms respectively coupled to said signal output, to said first terminal, to said second terminal, and to said signal input, said first and fourth arms being non coupled to each other, and control means having a control input coupled to said sync output for phase-shifting by in the signals received at one of said terminals, said control means being coupled to said phaseshifters of said second plurality.

For a better understanding of the invention and to 3,480,958 Patented Nov. 25, 1969 show how the same may be carried into effect reference will be made to the accompanying drawings, in which:

FIG. 1 shows diagrammatically an electronic scanning antenna supplied in a conventional manner.

FIG. 2 shows diagrammatically an embodiment of an electronic scanning antenna supplied according to the invention.

FIG. 3 shows the operation of a balanced hybrid junction with four branches; and

FIG. 4 shows diagrammatically a monopulse radar antenna improved according to the invention and FIG. 5 shows in detail a portion of a circuit according to the invention.

The conventional electronic scanning antenna arrangement shown in FIG. 1 comprises sixteen elements S to S and formed, for example, by dipoles having a length \/2, where is the wavelength of the operating wave. Only a few of the elements are shown in the drawing.

The elements are generally associated with a re fiector P.

The feed branch of each element contains in series a variable phase-shifter. Only two phase-shifters Ph and Ph have thier references on the drawing, for the sake of clarity.

The term variable phase-shifter is used here in the widest sense, that is to say, it covers any device such that a signal traversing the same undergoes a change in the phase as a function of a control signal applied to the control input of the phase-shifter. The control of each phase-shifter is represented symbolically by an arrow. The signal terminals of the phase-shifters which are not connected to the elements are connected to a conventional duplexer D through a device for distributing the power, comp-rising fifteen dividers d to a 15, shown here in the form of Ts, each of them distributing, for example in an even manner, the power applied to its input branch amongst its output branches.

The sixteen phase-shifters are controlled electronically at any moment so as to impart to the elementary elements the phase law, giving to the diagram of the antenna the desired direction of radiation. The transmitter E and the receiver R are connected in a conventional manner to the duplexer D.

The antenna according to the invention is shown in FIG. 2, wherein the elements identical to those of the conventional antenna of FIG. 1 are marked with the same references. The drawing shows again the transmitter E, the receiver R, the reflector P, the element S to S the phase-shifters Ph to P11 and the dividers d to d Here, the transmitter and the receiver are connected to the

uncoupled arms

1 and 4 of a magic tee T Whose

arms

3 and 2 are connected to the inputs of the dividers d and d Moreover, the eight last outputs of the control device C of the phase-shifters (which has not been shown in FIG. 1 in order not to overload this drawing and which is of conventional construction), are here connected to the control inputs of the phase-shifters Phg to Ph no longer directly, but through a device I with eight inputs and eight outputs which, according to whether it is in the inoperative or in the working position, transmits to the phase-shifters the orders issued by the control device C or orders derived therefrom, and causing an additional variation of the phase-shift by the amount 1r. The device I, which acts, when it is in the operative position, in some way, in the same manner as phase-shifters by 1r placed in series with the phase-shifters Phg to Ph is controlled, by the system transmission synchronization block, represented symbolically by the output SE of the transmitter E, in such a way that it is in inoperative position during the transmission and in operative position shortly afterwards. If (i=1 to 16) is the phase-shift introduced by a phase-shifter P11, in the transmission and that introduced by the same phase-shifter in the reception, it follows that g' =(p for i555 and ga' q i'rr for 1'59.

The signals in the

arms

2 and 3 which were in phase during the transmission when the branch 1 was fed by the transmitter, are now in phase opposition. Under these conditions, the whole energy received passes into the branch 4 which is connected to the receiver. This results from the very principle of operation of balanced hybrid junctions, such as the magic tee T in FIG. 2, which is discussed hereinafter with reference to FIG. 3. In this drawing, the junction T only is shown and the drawing indi cates, without brackets, the values of the signals when the phases (p and e at 2 and 3 are equal, and inside of brackets, the values of these signals when these phases differ by r. By using the conventional notations of electromagnetism, e being the base of Neperian logarithms and j the conventional symbol of imaginaries, the signals at 2 and 3 are, respectively, a2=Ae and a3=Ae A being the amplitude of the signals. If rp2= pl, the signal a4 in the arm 4 is zero and the signal al in the arm 1 is proportional to the sum of the signals a2 and a3, i.e., a1=K2Ae =K2Ae where K is a constant coefiicient dependent on the type of junction used.

In 3 db hybrid junctions, which are the best known junctions,

and (ii :VZZ

If t02= pli1r, a1 is zero and a4= /Z During the transmission, only the branch 1 is fed, a1

is equal to Be and a2=a3=E/ /2e where E is the amplitude of the signal supplied by the transmitter.

During the reception, owing to the action of the device I, 2= 1i1r and the received energy is directed wholly to the arm 4 which is connected to the receiver.

Naturally, the same result may also be obtained by changing the phase-shift by 1r in the reception in the feed branches of the sources S to S and not changing the phases in the branches of the sources S to S In this way, the duplexer has been eliminated in a simple manner at the price of replacing a simple power divider d by a balanced divider T, for example by a magic tee; moreover, balanced dividers are often used in power distribution for other reasons.

Obviously, the invention is not limited to the embodiment hereinbefore described, relating to the case where the signals received by all sources are added, in which case only a single hybrid junction is required.

In certain cases, it is necessary to make the partial sums of signals received by certain groups of source. This is the case particularly with monopulse radar antennae.

FIG. 4 gives, by way of non limitative example, a diagram of an application of the antenna according to the invention to a monopulse antenna with electronic scanning in elevation and azimuth. In this case, nothing is changed during the transmission, but in the reception it is necessary to form partial sums of the signals received by each quarter of the element panel, that is to say, the sums of signals received by the sources S to S S to S S9 to 512, and S13 to $15.

The dividers d, to d will therefore be replaced by magic tees (or other hybrid junctions with balanced arms) T to T having, respectively arms i to i,, where i=1 to 4, wherein the arm i of a junction (m=1 to 4) has the same function as the arm m of the junction T in FIG. 2.

The junction T in FIG. 2 is therefore useless and a simple power divider, such as d (FIG. 1) can be used. The

arms

11 and 21 of T and T are connected to the divider (I and the arms 31 and 41 of T 3 and T to the divider d whilst the

arms

13, 1,2, 23, 22, 33, 32, 43 and 4 42 are connected, respectively, to the dividers d d d in 12s 14 and lii: 15-

A device I, identical to the device I is now placed at the control inputs of the phase-shifters Ph Ph Ph etc, i.e., at inputs of phase-shifters with even indices. In this manner, the summation of the signals coming from the elements is no longer made in the branch of the T connected to the transmission, but in the fourth arm, that is to say, in 14, 24, 34 and 44.

Thus, by designating as b the signal received by the source S, (i=1 to 16), it follows that there is:

The signals B to B, can be treated in sum and in difference as known per se in monopulse antennae.

To this end, the

branches

14, 24, 34, 44 are connected to the corresponding inputs of a monopulse receiver RM.

Various known means may be used in order to vary by in the relative phase-shift introduced by phase-shifters Phg to Ph (FIGURE 2) 0r Ph Ph, Ph (FIG- URE 4) between the transmission and the reception, the choice of said means depending mainly on the type of the phase-shifters used.

Figure 5 represents a non limitative example of carrying out said 1r phase-shift in the case of Latching type phaseshifters Ph For the sake of clarity and in order to avoid overloading the figure, only one phase-shifter Ph, and only the connections from devices C and I to the same are shown on FIGURE 5.

It is assumed here, by way of example, that phaseshifter Ph comprises four ferrite elements, which, when Ph comprises four input terminals bi; to hi four output terminals bi to b'i and a control terminal hi which is coupled to the control input of device I, i.e to the output SE.

Terminals bz' to hi are coupled to feeders fi to fi respectively and terminals bi to bi, to elements Fi to Fi Terminals b'z' to bz' are directly coupled to terminals bi to big which are shown only for consistency with b.;, while bi to b'i could be coupled directly to feeders fi to fig.

Terminal hi is coupled to one of the two inputs of an anticoincidence circuit 0 whose other input is coupled to SE, and whose output is coupled to terminal b'i Thus, the element FL, is excited with an electrical pulse when one of the inputs of circuit 0, is fed with a signal, and is not excited when the two inputs of the latter are simultaneously fed or unfed.

Two cases may happen: 1

(1) The phase-shift (p at the transmission time is smaller than 'n'Z both inputs of circuit 0 are unfed when transmission is effected. At the reception time, only that input of circuit 0, which is coupled to SE is excited, thus P'i=1+ (2) The phase-shift at the transmission is greater than 1r: only that input of circuit 0-,, which is coupled to terminal hi is excited when transmission is effected and circuit FL; is operated.

At the reception time, both inputs of circuit 0 are excited, which results in non-operation of circuit Fi thus p'- =(p -n',

The required condition i1r has thus been met in both cases.

Naturally, the invention is not limited to the embodiments hereinbefore described and given merely by way of example.

The invention has been heretofore described in the simplest case, where the utilized balanced hybrid junctions are of the type in which applying a signal to arm 1 results in two in-phase signals in

arms

2 and 3.

Of course, the invention may also be put into practice with junctions of a different type, where applying a signal to arm 1 results in two signals in

arms

2 and 3, the relative phase-shift of which has a constant value different of zero. In this latter case, it will be necessary to compensate, for the phase-shift go the phase-shift (,0; introduced by those among the phase-shifters P11 which are placed in circuits fed through arm 2.

It will be also noted that the invention is still usable each time an aerial system having at least two terminals employed, no matter whether or not it is a scanning system. In the case where the aerial feed system does not include phase-shifters per se, a device for phase-shifting by 180 will be alternately placed in the connecting circuit of one of the terminals.

Nevertheless, the invention is of particular interest when electronic scanning antennae are involved because phase-shifters are existing per se in the circuits of said antenna, each of said phase-shifters being traversed by only a portion of the total power.

Of course, the number of the elements of the network forming the antenna, and their grouping may be different from those described, The invention may be for example used with advantage in electronic scanning antennae of reduced dimension as described in the copending patent application filed by Sorge Landesman and Jacques Salmon, for Steerable Antenna System, Ser. No. 598,146, filed November 28, 1966 and assigned to the same assignee.

What is claimed is:

1. A transmit-receive system comprising transmitting means having a sync output and a signal output, receiving means having a signal input; aerial means comprising a first plurality of radiating elements and controllable phase-shifters, said plurality having a first terminal and a second plurality of radiating elements and controllable phase-shifters, said second plurality having a second terminal; programming means for controlling said phase shifters having a first plurality of outputs coupled to said phase-shifters of said first plurality, and a second plurality of outputs coupled to said phase-shifters of said second plurality; and a coupling circuit for alternately coupling said signal output and said signal input to both said terminals, said circuit comprising a balanced hybrid junction having a first, a second, a third and a fourth arms respectively coupled to said signal output, to said first terminal, to said second terminal, and to said signal input, said first and fourth arms being noncoupled to each other, and control means having a control input coupled to said sync output for phase-shifting by i1r the signals received at one of said terminals, said control means having an output coupled to said phase-shifters of the corresponding plurality.

2. A transmit receive system according to claim 1, wherein said control means comprise n anticoincident circuits having respective first inputs coupled to said sync output and respective second inputs respectively coupled to said second plurality of outputs.

3. A transmit receive system according to claim 1 wherein said receiver comprises a second signal input, said aerial means comprises further third and fourth plurality of radiating elements and phase-shifters, having respective further third and fourth terminals, said programming means having further third and fourth plurality of outputs coupled respectively to said phaseshifters of said third and fourth plurality, and said coupling means further comprises: a second balanced hybrid junction having a fifth arm, a sixth arm coupled to said third terminal, a seventh arm coupled to said fourth terminal, an eighth arm coupled to said further input, and a first three terminal divider junction having an input coupled to said transmitting means signal output, and respective outputs respectively coupled to said first and fifth arms, said control means being further coupled to said phase-shifters of said fourth plurality.

4. A system according to claim 3, wherein said receiver comprises a third and a fourth signal inputs, said aerial means comprises further fifth, sixth, seventh and eighth pluralities of radiating elements and phase-shifters having respective terminals, said programming means having further fifth, sixth, seventh and eight pluralities of outputs coupled respectively to said phase-shifters of said fifth to eighth pluralities, and wherein said Coupling means further comprises: a third balanced hybrid junction having a ninth arm, a tenth arm coupled to said fifth terminal, an eleventh arm coupled to said sixth terminal and a twelfth arm coupled to said third signal input, a fourth balanced hybrid junction having a thirteenth arm, a fourteenth arm coupled to said seventh terminal, a fifteenth arm coupled to said eighth terminal, and a sixteenth arm coupled to said fourth signal input, a second three terminal divider junction having an input and respective outputs respectively coupled to said ninth and thirteenth arms, and a third three terminal divider junction having an input coupled to said transmitter and two outputs coupled to said inputs of said first and second divider junction, said control means being further coupled to said phase-shifters of said sixth and eighth pluralities.

5. In a transmit-receive system comprising transmitting means having a sync output and a signal output, receiving means having a signal input, and aerial means comprising at least a first and a second terminals, the level of the received energies at said terminals being equal: a coupling circuit for alternately coupling said signal output and said signal input to both said terminals, said circuit comprising at least one balanced hybrid junction having a first, a second, a third and a fourth arms respectively coupled to said signal output, to said first terminal, to said second terminal, and to said signal input, said first and fourth arms being non coupled to each other, and control means having a control input coupled to said sync output for phase-shifting by .ivr the signals received at one of said terminals.

References Cited UNITED STATES PATENTS 3,355,735 11/1967 Chait.

RODNEY D. BENNETT, JR., Primary Examiner T. H. TUBBESING, Assistant Examiner US. Cl. X.R. 343-100, 854