Direction finding

• US 7,612,715 B2
• Filed: 07/05/2004
• Issued: 11/03/2009
• Est. Priority Date: 07/12/2003
• Status: Active Grant

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Inventors: Macleod, Malcolm Davd
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Nguyen; Nga X
• Application Number:
  US10/563,495
• Publication Number:
  US 20060158375A1
• Time in Patent Office: 1,947 Days
• Field of Search: 342/359, 342/360, 342368-465
• US Class Current: 342/432
• CPC Class Codes: G01S 3/043 Receivers
• CPC Class Codes: G01S 3/14 Systems for determining direction or deviation from predetermined direction aerial arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00; combinations of different interacting aerial units for giving a desired directional characteristic H01Q21/29; aerials or aerial systems providing at least two radiation patterns H01Q25/00
• CPC Class Codes: G01S 3/46 using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
• CPC Class Codes: G01S 3/74 Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals systems in which the directions of different signals are determined sequentially and displayed simultaneously G01S3/04, G01S3/14

Abstract

Direction findings by radio comprises arraigning an array of antennas, to receive signals from emitters, selecting individual antenna signals using a first multipole switch and determining, antenna signal strengths. Individual antenna signals are also selected by mutipole switch, which routes a selected signal to a third multipole switch. The third switch switches a phase shifter into and out of an antenna signal path. An adder is employed to add an antenna signal in a first signal path extending via the first multipole switch to a different antenna signal in a second signal path extending via the second and third switches. This determines combined signal strengths between pairs of antenna signals, one of which either has or has not been relatively phase shifted depending on the third switch position. Covariance matrix elements are determined from signal strengths enabling emitter bearings to be derived.

Claims

1. A direction finding system comprising:

a) a plurality of antennas;

b) means for determining individual signal strengths of signals received by each of the plurality of antennas;

c) combining means for deriving combined antenna signal strengths by forming combinations of first and second antenna signals derived from different antennas, wherein the second antenna signals are in two sets with signals in one set having a non-zero phase difference relative to signals in the other set; and

d) means for determining at least one emitter bearing from the individual and combined antenna signal strengths measured.

2. A direction finding system according to claim 1 wherein the means for determining emitter bearing is arranged to derive covariance matrix elements from antenna signal strengths and to determine emitter bearing therefrom.

3. A direction finding system according to claim 1 wherein the means for determining emitter bearing is arranged to derive a relationship between antenna signal strengths and emitter bearing and to determine emitter bearing therefrom.

4. A direction finding system according to claim 1 wherein the relative phase difference is in the range 30 to 120 degrees, and the means for determining individual antenna signal strengths and the combining means are arranged to enable successive signal strengths to be derived in successive steps.

5. A direction finding system according to claim 1 wherein the relative phase difference is substantially 90 degrees.

6. A direction finding system according to claim 5 wherein the combining means is arranged to combine antenna signals with equal gain magnitude and with equal and unequal phase.

7. A direction finding system according to claim 1 wherein the combining means incorporates phase shifting means switchable into and out of an antenna signal path.

8. A direction finding system according to claim 1 wherein the combining means incorporates an adder having two inputs both switchably connected to individual signal paths extending to respective antennas.

9. A direction finding system comprising:

a) a plurality of antennas;

b) means for determining individual antenna signal strengths, the means for determining individual antenna signal strengths comprising a first multipole switch having input poles connected to receive signals from respective antennas;

c) combining means for deriving combined antenna signal strengths by forming combinations of a first and second antenna signals derived from different antennas, wherein the second antenna signals are in two sets with signals in one set having a non-zero phase difference relative to signals in the other set, the combining means incorporating a second multipole switch having input poles connected to receive signals from respective antennas and a third multipole switch for switching phase shifting means into and out of an antenna signal path extending via the second multipole switch;

d) the combining means also incorporating adding means for combining signals, the adding means being arranged to add an antenna signal in a first signal path extending via the first multipole switch to another antenna signal in a second signal path extending via the second and third multipole switches; and

e) means for determining at least one emitter bearing from antenna signal strengths.

10. A method of direction finding using a plurality of antennas comprising the steps of determining:

a) individual signal strengths of signals received by each of the plurality of antennas;

b) combined antenna signal strengths by forming combinations of first and second antenna signals derived from different antennas, wherein the second antenna signals are in two sets with signals in one set having a non-zero phase difference relative to signals in the other set; and

c) at least one emitter bearing from the individual and combined antenna signal strengths measured.

11. A method according to claim 10 wherein the step of determining emitter bearing is implemented by deriving covariance matrix elements from antenna signal strengths and determining emitter bearing therefrom.

12. A method according to claim 10 wherein the step of determining emitter bearing is implemented by deriving a relationship between antenna signal strengths and emitter bearing and determining emitter bearing therefrom.

13. A method according to claim 10 wherein the relative phase difference is in the range 30 to 120 degrees and successive signal strengths are determined in successive steps.

14. A method according to claim 13 wherein the relative phase difference is substantially 90 degrees.

15. A method according to claim 10 wherein the step of forming combined antenna signal strengths combines antenna signals with equal gain magnitude and with equal and unequal phase.

16. A method according to claim 12 wherein the step of forming combined antenna signal strengths includes switching a phase shift into and out of an antenna signal path.

17. A method according to claim 12 wherein the step of forming combined antenna signal strengths includes adding signals in signal paths extending switchably to different antennas.

18. A method of direction finding using a plurality of antennas comprising the steps of determining:

a) individual antenna signal strengths;

b) combined antenna signal strengths by forming combinations of first and second antenna signals derived from different antennas, wherein the second antenna signals are in two sets with signals in one set having a non-zero phase difference relativerel-a-tiftg to signals in the other set; and

c) at least one emitter bearing from the antenna signal strengths, wherein step a) comprises switching signals from antennas via a first path; and

step b) incorporates;

i) switching signals from antennas via a first path for combining;

ii) switching signals from antennas via a switch selectable second path or a third path for combining, the third path being arranged to phase shift antenna signals therein relative to antenna signals in the second path; and

iii) adding a first path antenna signal to second and third path antenna signals individually.

19. A method of direction finding using a plurality of antennas comprising the steps of determining:

a) individual antenna signal strengths by switching signals from the antennas via a first path;

b) combined antenna signal strengths by forming combinations of first and second antenna signals derived from different antennas, wherein the second antenna signals are in two sets with signals in one set having a non-zero phase difference relative to signals in the other set; and

c) covariance matrix elements using the individual and combined antenna signal strengths measured, and determining at least one emitter bearing therefrom;

wherein the step of determining combined antenna signal strengths incorporates;

i) switching signals from antennas via a first path for combining;

ii) switching signals from antennas via a switch selectable second path or a third path for combining, the third path being arranged to phase shift antenna signals therein relative to antenna signals in the second path; and

iii) adding a first path antenna signal to second and third path antenna signals individually.

20. A direction finding system incorporating:

a) a plurality of antennas;

b) measuring apparatus for determining strengths of signals received by each of the plurality of antennas;

c) a combining circuit for deriving combined antenna signal strengths by forming combinations of first and second antenna signals derived from different antennas, wherein the second antenna signals are in two sets with signals in one set having a non-zero phase difference relative to signals in the other set; and

d) digital signal processing apparatus for determining at least one emitter bearing from the individual and combined antenna signal strengths measured.