GB2123214A - Aerial arrangement - Google Patents

Abstract

An aerial arrangement comprising four parallel elements 2,3,4,5, arranged to define two orthogonally disposed loops, with two of the elements being included in each loop and a phase shift network connected to the elements effective to combine signals from the loops to provide a monopole output mode signal and a cross loop mode output signal. If the four signals from the elements are A,B,C and D as shown, these are processed through a phase shift circuit comprising four hybrids 10, 13, 18 and 21, and a monopole mode signal A+B+C+D is obtained on line 19, whilst cross loop mode signals A-B-j(C-D) and C-D-j(A-B) are obtained on lines 22,23. The signals may be supplied to a direction finding arrangement as disclosed in G.B. Patent Specification 1541449. <IMAGE>

Description

SPECIFICATION Aerial arrangement This invention relates to aerial arrangements.

According to the present inventipn, an aerial arrangement comprises four parallel elements arranged to define two orthogonally disposed loops, with two of the elements being included in each loop and a phase shift network connected to the elements effective to combine signals from the loops to provide a monopole output mode signal and a cross loop mode output signal.

The phase shift network may comprise a first phase shifter device responsive to two signals A and B derived respectively from the elements of one-loop and providing two output signals corresponding to A + B and A - B, respectively, a second phase shifter device responsive to two signals C-and D derived respectively from the elements of the other loop and providing two output signals corresponding to C + D and C - D respectively, a third phase shifter device responsive to the signals (A + B) and (C + D) respectively for providing the monopole output mode signal which correspondsto (A + B) + (C + D) and a forth phase shift device responsive to thesignals A - B and C - D respectively for providing the cross loop output mode signal which corres pondseitherto (A - B) - j(C - D) orto (C - D) - j(A B).

The four parallel elements of the loops may comprise conductors supported on a rigid former so as to be parallel to the longitudinal axis of the former.

The former may be hollow and generally cylindrical and the loops may be arranged to cross over one end of the former so that the cross over point of the loops is coincident with the longitudinal axis of the former.

The end of the former at which the loops cross over may be closed whereby those parts of the loops at this end of the former are supported by the closed end.

The four parallel elements may be defined by metal strips supported on the surface of the former.

The strips may be made of copper.

The strips may be applied by a printed circuit technique.

The former may be of plastics material.

The former and the elements which define the loops may comprise an element assembly which in combination with the phase shift network may form a unitary aerial assembly, eminently suitable for attachment to a vehicle.

The monopole mode signal and the cross loop mode signal or signals, may be processed in various ways as will be appreciated by those skilled in the art to afford a signal direction finder function orto provide for a manual or an adaptive null steering function suitable for discriminating against directional interfering signals.

Signal processors for direction finding and for null steering are well known and will not be described herein but attention is directed to our U.K. Patent No.

1541449 which describes apparatus suitable for null steering.

One embodiment of the invention will now be described solely by way of example with reference to the accompanying drawings in which.

Figure",1 is a somewhat schematic block diagram showing a crossed loop antenna connected to a phase shift network; Figure2 is a somewhat schematic perspective view of the antenna of Figure 1 supported on a cylindrical plastics former and; Figure 3 is a phase shift diagram illustrating the relative phase-shifts of the output signals from the phase shift network shown in Figure 1-for various azimuth angles.

Referring now to Figure 1, a cross loop antenna 1 comprises four parallel aerial elements 2, 3,4 and 5 arranged to define two orthogonally disposed loops, one of which is defined by the elements 2 and 4 and the other of which is defined by the elements 3 and 5. The elements 2,3,4 and 5 are fabricated from conductive strip material which are supported on a hollow cylindrical plastics former 6 as shown in Figure 2. It can be seen from Figure 2 that the elements 2,3t 4 and 5 extend across the top of the former 6 and meet at a point 7 which corresponds to the longitudinal axis of the cylindrical former 6.

Signals from the elements 2 and 4 are fed via conductors 8 and 9 respectively to a hybrid phase shift device 10. Similarly, signals from the elements 3 and 5 are fed via conductors 11 and 12 respectively to a similar hybrid device 13. Signals fed from the elements 2 and 4 via lines 8 and 9 to the hybrid device 10 are designated B and A respectively and in the same way signals fed via lines 11 and 12 to the hybrid device 13 are designated D and C respectively. The hybrid device 10 operates to provide on an output line 14 a signal corresponding to A + B and on an output line 15 a signal corresponding to A - B.

Similarly hybrid device 13 operates to provide on an output line 16 a signal corresponding to D + C and on output line 17 a signal corresponding to C - D.

The lines 14 and 16 are fed to a further hybrid device 18 which provides on an output line 19 a monopole mode output signal corresponding to A + B + C + D.

The hybrid device 18 also includes a complementary output line 20 which is not used and which is therefore terminated The lines 15 and 17 are fed to a quadrature hybrid device 21 to provide two output signals-on lines 22 and 23 respectively which are mutually in phase quadrature. Thus the signal on the line 22 correspondsto (A - B) - j(C - D) and the signal on the line 23 corresponds to (C - D) - j(A B).

Thus it can be shown that as the bearing of a radio signal wave front as indicated by the arrow 24 varies in azimuth between 0 and 360 , the signal on the line 19 will vary correspondingly as shown by the line 25 and the phase of the signals on the lines 22 and 23, which respesent left and right hand crossed loop mode output signals, will vary as indicated by the lines 26 and 27 respectively in Figure 3. The hybrid devices 10, 13, and 18 are proprietary devices and may comprise ANZAC HH-105 devices. The quadrature hybrid device 21 is also readily available and may comprise an ANZACJH 132 device.

It will be appreciated that the output signals on the lines 19 and 22 or 23 may be processed in various ways in accordance with the application in view. It is contemplated howeverthatthe aerial arrangement described may be fitted to a vehicle to provide an adaptive or a manual steerable null function and serve to afford discrimination against directional interference. A circuit arrangement suitable for processing the received signals to afford such a function for direction finding purposes is fully described in our U.K.Patent No. 1541449 and this circuit may be arranged to receive at its input terminals P1, P2 two output signals from the line 19 and the line 22 or the line 23 respectively and to utilise these signals to afford a null in the polar diagram of the arrangement which may be steered for direction finding purposes orto correspond with the bearing of an interferring signal whereby the interferring signal is suppressed relative to a wanted signal arriving on a different bearing.

In an arrangement exclusively concerned with interference suppression, the input terminals P1 and P2 of the circuit described in U.K. Patent No. 1541449 may be fed from the lines 22 and 23 with the crossed loop mode signals. This arrangement may not be suitable for direction finding since bearing ambiguities may arise.

CLAIMS (Filed on 29/4/83) 1. An aerial arrangement comprising four parallel elements arranged to define two orthogonally disposed loops, with two of the elements being included in each loop and a phase shift network connected to the elements effective to combine signals from the loops to provide a monopole output mode signal and a cross loop mode output signal.

2. An aerial arrangement as claimed in Claim 1 wherein the phase shift network comprises a first phase shifter device responsive to two signals A and B derived respectively from the elements of one loop and providing two output signals corresponding to A + B and A - B, respectively, a second phase shifter device responsive to two signals C and D derived respectively from the elements of the other loop and providing two output signals corresponding to C + D and C - D respectively, a third phase shifter device responsive to the signals (A + B) and (C + D) respectively for providing the monopole output mode signal which corresponds to (A + B) + (C + D) and a fourth phase shift device responsive to the signals A - B and C - D respectively for providing the cross loop output mode signal which corresponds either to (A - B) - j(C - D) orto (C - D) - j(A B).

3. An aerial arrangement as claimed in Claim 2 wherein the four parallel elements of the loop comprise conductors supported on a rigid former so as to be parallel to the longitudinal axis of the former.

4. An aerial arrangement as claim in Claim 3 wherein the former is hollow and generally cylindrical and the loops are arranged to cross over one end of the former so that the cross over point of the loops is coincident with the longitudinal axis of the former.

5. An aerial arrangement as claimed in Claim 4 wherein the end of the former in which the loops cross over is closed whereby those parts of the loops at this end of the former are supported by the closed end.

6. An aerial arrangement as claimed in any of Claims 3 to 5 wherein the four parallel elements are defined by metal strips supported on the surface of the former.

7. An aerial arrangement claimed in Claim 6 wherein the strips are made of copper.

8. An aerial arrangement as claimed in Claim 6 or Claim 7 wherein the strips are applied by a printed circuit technique.

9. An aerial arrangement as claimed in any of Claims 3 to 8 wherein the former is made of plastics material.

10. An aerial arrangement as claimed in any of Claims 3 to 9 wherein the former and the elements which define the loops comprise an element assemblywhich in combination with the phase shift network forms a unitary aerial assembly suitable for attachment to a vehicle.

11. An aerial arrangement substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. It will be appreciated that the output signals on the lines 19 and 22 or 23 may be processed in various ways in accordance with the application in view. It is contemplated howeverthatthe aerial arrangement described may be fitted to a vehicle to provide an adaptive or a manual steerable null function and serve to afford discrimination against directional interference. A circuit arrangement suitable for processing the received signals to afford such a function for direction finding purposes is fully described in our U.K.Patent No. 1541449 and this circuit may be arranged to receive at its input terminals P1, P2 two output signals from the line 19 and the line 22 or the line 23 respectively and to utilise these signals to afford a null in the polar diagram of the arrangement which may be steered for direction finding purposes orto correspond with the bearing of an interferring signal whereby the interferring signal is suppressed relative to a wanted signal arriving on a different bearing. In an arrangement exclusively concerned with interference suppression, the input terminals P1 and P2 of the circuit described in U.K. Patent No. 1541449 may be fed from the lines 22 and 23 with the crossed loop mode signals. This arrangement may not be suitable for direction finding since bearing ambiguities may arise. CLAIMS (Filed on 29/4/83)

1. An aerial arrangement comprising four parallel elements arranged to define two orthogonally disposed loops, with two of the elements being included in each loop and a phase shift network connected to the elements effective to combine signals from the loops to provide a monopole output mode signal and a cross loop mode output signal.

2. An aerial arrangement as claimed in Claim 1 wherein the phase shift network comprises a first phase shifter device responsive to two signals A and B derived respectively from the elements of one loop and providing two output signals corresponding to A + B and A - B, respectively, a second phase shifter device responsive to two signals C and D derived respectively from the elements of the other loop and providing two output signals corresponding to C + D and C - D respectively, a third phase shifter device responsive to the signals (A + B) and (C + D) respectively for providing the monopole output mode signal which corresponds to (A + B) + (C + D) and a fourth phase shift device responsive to the signals A - B and C - D respectively for providing the cross loop output mode signal which corresponds either to (A - B) - j(C - D) orto (C - D) - j(A B).

3. An aerial arrangement as claimed in Claim 2 wherein the four parallel elements of the loop comprise conductors supported on a rigid former so as to be parallel to the longitudinal axis of the former.

4. An aerial arrangement as claim in Claim 3 wherein the former is hollow and generally cylindrical and the loops are arranged to cross over one end of the former so that the cross over point of the loops is coincident with the longitudinal axis of the former.

5. An aerial arrangement as claimed in Claim 4 wherein the end of the former in which the loops cross over is closed whereby those parts of the loops at this end of the former are supported by the closed end.

6. An aerial arrangement as claimed in any of Claims 3 to 5 wherein the four parallel elements are defined by metal strips supported on the surface of the former.

7. An aerial arrangement claimed in Claim 6 wherein the strips are made of copper.

8. An aerial arrangement as claimed in Claim 6 or Claim 7 wherein the strips are applied by a printed circuit technique.

9. An aerial arrangement as claimed in any of Claims 3 to 8 wherein the former is made of plastics material.

10. An aerial arrangement as claimed in any of Claims 3 to 9 wherein the former and the elements which define the loops comprise an element assemblywhich in combination with the phase shift network forms a unitary aerial assembly suitable for attachment to a vehicle.

11. An aerial arrangement substantially as hereinbefore described with reference to the accompanying drawings.