System and method for efficiently characterizing the elements in an array antenna

• US 6,507,315 B2
• Filed: 05/03/2001
• Issued: 01/14/2003
• Est. Priority Date: 05/03/2001
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Lier, Erik, Ashe, Jeffrey M., Purdy, Daniel S.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Mull, Fred H
• Application Number:
  US09/848,063
• Publication Number:
  US 20020171583A1
• Time in Patent Office: 621 Days
• Field of Search: 342/165, 342/174, 342/372, 342/374, 342/373, 342/360
• US Class Current: 342/374
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

Abstract

A system and method to individually characterize all of the antenna elements or amplifiers in an array antenna system simultaneously, without the need to perform sequential measurements. A positioning device allows movement of the antenna with respect to a calibration probe or movement of the calibration probe with respect to the antenna. Multiple simultaneous control circuit encoding (CCE) measurements of each of the array elements in an array antenna are performed. A second aspect of the system and method involves changes in the level of signals transmitted by the amplifiers in the elements of an array antenna system in conjunction with the use of orthogonal coding measurements. Changes in the level of signals transmitted permits simultaneous measurement of the amplifier characteristics of each of the array elements in an array antenna.

Claims

1. A system for characterizing the patterns of a plurality of elements located in an array antenna, each of said plurality of elements including at least one of a (a) phase shifter and an (b) amplitude attenuator, in which said antenna includes a signal port for each individual beam which said array antenna generates, and a control signal input port to which control signals are applied for control of said phase shifters and amplitude attenuators, the plurality of elements therein comprising a beamformer, a plurality of said beamformers forming said array antenna, said system for characterizing the patterns of a plurality of elements located in said array antenna comprising:

a probe positioned within the field of said array antenna,

positioning means for changing the relative position between said probe and said antenna,

a calibration radio-frequency source, said calibration radio-frequency source being (a) coupled to at least one of the signal-ports of said array antenna when said array antenna is oriented as a transmit antenna, and (b) coupled to said probe when said array antenna is oriented as a receive antenna, said calibration radio-frequency source generating a calibration signal;

an orthogonal code generating means applied to a plurality of said antenna elements of said array antenna for sequentially setting at least one of said (a)phase shifters and (b)amplitude attenuators with a plurality of sets of values, each of the sets of values imposing a coding on said calibration signal to thereby sequentially generate calibration signals encoded with sets of values, each set of values so encoded onto said calibration signals being orthogonal to other sets of values with which said calibration signals are encoded, whereby, when said array antenna is oriented as a transmit antenna, said probe receives said calibration signals sequentially encoded with mutually orthogonal values, and when said array antenna is oriented as a receive antenna, said calibration signals sequentially encoded with mutually orthogonal values are generated at at least one of said signal ports of said array antenna;

a coherent radio-frequency receiver;

a decoder for decoding signals encoded with said mutually orthogonal values, for generating decoded signals therefrom;

encoded signal coupling means for coupling said encoded signals to said decoder as a result of which said decoder generates said decoded signals;

a processor coupled to said decoder, for processing said decoded signals for generating signals representing at least the values of one of phase shift and attenuation;

coupling means coupled to said processor and to at least one of said phase shifters and said amplitude attenuators, for coupling to said signals representing at least the values of one of phase shift and attenuation;

a recorder for recording said signals representing at least the values of one set of probe-element positions and element characterization patterns; and

an antenna controller for controlling the relative position between said probe and said antenna and for controlling said orthogonal code generating means.

2. The system of claim 1 wherein said probe is positioned at at least one of (a) a distance fixed relative to said array antenna and (b) an orientation fixed relative to said array antenna.

3. The system of claim 1 wherein said probe is at a position corresponding essentially to the boresight position of one of said plurality of antenna elements.

4. The system of claim 1 wherein said probe is at a position corresponding essentially to the front of one of said plurality of antenna elements.

5. The system of claim 1 wherein said probe is at a position in the far field of said array antenna.

6. The system of claim 1 wherein said

positioning means changes the position of said probe relative to said array antenna by rotation of said array antenna around a vertical axis which is one of (a) coincident with the centerline of said probe, and (b) parallel to,the centerline of said probe.

7. The system of claim 1 wherein said

positioning means changes the position of said probe relative to said array antenna by translation of said array antenna to a position such that at least one of said beamformers remains parallel to the original position of said at least one beamformer.

8. The system of claim 1 wherein said

positioning means changes the position of said probe relative to said array antenna by movement of said probe along a track.

9. The system of claim 1 wherein said antenna controller controls the positioning means for changing the position of said probe relative to said array antenna.

10. The system of claim 1, further comprising:

display means for displaying said at least the values of one set of probe-element positions and element characterization patterns so determined by said processor.

11. A system for determining the characteristics of a plurality of amplifiers in an array antenna, each amplifier coupled to an element located in said array antenna therein forming a plurality of elements, each of said plurality of elements including at least one of a (a) phase shifter and an (b) amplitude attenuator, in which said array antenna includes a beam port for each individual beam which said antenna generates, and a control signal input port to which control signals are applied for control of said phase shifters and amplitude attenuators, said plurality of elements therein comprising a beamformer, a plurality of said beamformers forming said array antenna, said system for determining the characteristics of a plurality of amplifiers located in said array antenna comprising:

a probe positioned at a position fixed relative to said array antenna, said probe being within the field of said array antenna,

signal level changing means for changing the strength level of signals applied to a plurality of amplifiers located in any one of said beamformers of said array antenna;

a calibration radio-frequency source, said calibration radio-frequency source being (a) coupled to at least one of said signal ports of said array antenna when said array antenna is oriented as a transmit antenna, and (b) coupled to said probe when said array antenna is oriented as a receive antenna, said calibration radio-frequency source generating a calibration signal;

an orthogonal code generating means applied to a plurality of said antenna elements corresponding to any one of said beamformers for sequentially setting at least one of said (a)phase shifters and (b)amplitude attenuators with a plurality of sets of values, each of said sets of values imposing a coding on said calibration signal to thereby sequentially generate calibration signals encoded with sets of values, each set of values so encoded onto said calibration signals being orthogonal to other sets of values with which said calibration signals are encoded, whereby, when the array antenna is oriented as a transmit antenna, said probe receives said calibration signals sequentially encoded with mutually orthogonal values, and when said array antenna is oriented as a receive antenna, said calibration signals sequentially encoded with mutually orthogonal values are generated at at least one of said signal ports of said array antenna;

a coherent radio-frequency receiver;

a decoder for decoding signals encoded with said mutually orthogonal values, for generating decoded signals therefrom;

encoded signal coupling means for coupling said encoded signals to said decoder, as a result of which said decoder generates said decoded signals;

a processor coupled to said decoder, for processing said decoded signals for generating signals representing at least the values of one of phase shift and attenuation,

coupling means coupled to, said processor and to at least one of said phase shifters and said amplitude attenuators, for processing said decoded signals for generating signals representing at least the values of at least one set of signal levels and amplifier characteristics;

a recorder for recording said signals representing at least the values of one set of probe element positions and orientations and amplifier characteristics; and

an antenna controller for controlling said signal level changing means and said orthogonal code generating means.

12. The system of claim 11 wherein said probe is positioned at at least one of (a) a distance fixed relative to said array antenna and (b) an orientation fixed relative to said array antenna.

13. The system of claim 11 wherein said probe is at a position corresponding essentially to the boresight position of one of said plurality of antenna elements.

14. The system of claim 11 wherein said probe is at a position corresponding essentially to the front of one of said plurality of antenna elements.

15. The system of claim 11 wherein said probe is at a position in the far field of said array antenna.

16. The system of claim 11, further comprising display means for displaying at least the values of one set of signal levels and amplifier characteristics so determined by said processor.

17. The system of claim 11, wherein the property of an amplifier so determined is the output signal amplitude compared to the input signal amplitude.

18. The system of claim 11, wherein the property of an amplifier so determined is the relative phase between the output signal and the input signal.

19. A method for characterizing the patterns of a plurality of elements located in an array antenna, each of said plurality of elements including at least one of a (a) phase shifter and an (b) amplitude attenuator, in which said array antenna includes a signal port for each individual beam which said array antenna generates, and a control signal input port to which control signals are applied for control of said phase shifters and amplitude attenuators, the plurality of elements therein comprising a beamformer, a plurality of said beamformers forming said array antenna, said method for characterizing the patterns of a plurality of elements located in said array antenna comprising the steps of:

positioning a probe within the field of said array antenna, said probe and said array antenna fixed in position relative to each other;

generating a calibration signal by means of a calibration radio-frequency source, said calibration radio-frequency source being (a) coupled to at least one of the signal-ports of said array antenna when said array antenna is oriented as a transmit antenna, and (b) coupled to said probe when said array antenna is oriented as a receive antenna;

applying an orthogonal code generating means to a plurality of said antenna elements of said array antenna for sequentially setting at least one of said (a)phase shifters and (b)amplitude attenuators with a plurality of sets of values, each of the sets of values imposing a coding on said calibration signal to thereby sequentially generate calibration signals encoded with sets of values, each set of values so encoded onto said calibration signals being orthogonal to other sets of values with which said calibration signals are encoded, whereby, when said array antenna is oriented as a transmit antenna, said probe receives said calibration signals sequentially encoded with mutually orthogonal values, and when said array antenna is oriented as a receive antenna, said calibration signals sequentially encoded with mutually orthogonal values are generated at at least one of said signal ports of said array antenna;

receiving said calibration signals sequentially encoded with mutually orthogonal values by means of a coherent radio-frequency receiver;

decoding signals encoded with said mutually orthogonal values by means of a decoder for generating decoded signals therefrom;

coupling said encoded signals to said decoder as a result of which said decoder generates said decoded signals;

processing by means of a processor coupled to said decoder said decoded signals for generating signals representing at least the values of one of phase shift and if, attenuation;

coupling to said signals representing at least the values of one of phase shift and attenuation by coupling means coupled to said processor and to at least one of said phase shifters and said amplitude attenuators;

recording said signals representing at least the values of one set of probe-element positions and element characterization patterns by means of a recorder;

controlling by means of an antenna controller the relative position between said probe and said antenna, and said orthogonal coding means;

using orthogonal coding to perform simultaneous measurements comprising at least one of (a) phase angles, and (b) amplitude levels of said phase shifters and attenuators of said plurality of elements corresponding to said array antenna;

changing the relative position between said probe and said array antenna to a plurality of positions;

using orthogonal coding to perform simultaneous recorded measurements comprising at least one of (a) phase angles and (b) amplitude levels of the plurality of elements at each of the plurality of positions in the array antenna;

scaling the measurements of the relative probe element-probe positions by compensating for the pattern inherent to said probe, and

recovering element patterns versus element-probe positions to characterize the patterns of elements of said array antenna.

20. The method of claim 19 further comprising the step of determining the pattern inherent to said probe with respect to said array antenna, therein yielding the inherent characteristic probe pattern.

21. The method of claim 19 wherein said probe is positioned at at least one of (a) a distance fixed relative to said array antenna and (b) an orientation fixed relative to said array antenna.

22. The method of claim 19 wherein said probe is at a position corresponding essentially to the boresight position of one of said plurality of antenna elements.

23. The method of claim 19 wherein said probe is at a position corresponding essentially to the front of one of said plurality of antenna elements.

24. The method of claim 19 wherein said probe is at a position in the far field of said array antenna.

25. The method of claim 19 wherein said positioning means changes the position of said probe relative to said array antenna by rotation of said array antenna around a vertical axis which is one of (a) coincident with the centerline of said probe, and (b) parallel to the centerline of said probe.

26. The method of claim 19 wherein said positioning means changes the position of said probe relative to said array antenna by translation of said array antenna to a position such that at least one of said beamformers remains parallel to the original position of said at least one beamformer.

27. The method of claim 19 wherein said positioning means changes the position of said probe relative to said array antenna by movement of said probe along a track.

28. The method of claim 19 further comprising the step of displaying said recovered element patterns versus element-probe positions and orientations.

29. A method for determining the characteristics of a plurality of amplifiers in an array antenna, each amplifier coupled to an element located in said array antenna therein forming a plurality of elements, each of said plurality of elements including at least one of a (a) phase shifter and an (b) amplitude attenuator, in which said array antenna includes a beam port for each individual beam which said antenna generates, and a control signal input port to which control signals are applied for control of said phase shifters and amplitude attenuators, said plurality of elements therein comprising a beamformer, a plurality of said beamformers forming said array antenna, said method for determining the characteristics of a plurality of amplifiers located in said array antenna comprising the steps of:

positioning a probe at a position fixed relative to said array antenna, said probe being within the field of said array antenna,

applying signals of an initial strength level to a plurality of amplifiers located in any one of said beamformers of said array antenna;

generating a calibration signal by means of a calibration radio-frequency source, said calibration radio-frequency source being (a) coupled to at least one of said signal ports of said array antenna when said array antenna is oriented as a transmit antenna, and (b) coupled to said probe when said array antenna is oriented as a receive antenna;

applying an orthogonal code generating means to a plurality of said antenna elements corresponding to any one of said beamformers for sequentially setting at least one of said (a)phase shifters and (b)amplitude attenuators with a plurality of sets of values, each of said sets of values imposing a coding on said calibration signal to thereby sequentially generate calibration signals encoded with sets of values, each set of values so encoded onto said calibration signals being orthogonal to other sets of values with which said calibration signals are encoded, whereby, when the array antenna is oriented as a transmit antenna, said probe receives said calibration signals sequentially encoded with mutually orthogonal values, and when said array antenna is oriented as a receive antenna, said calibration signals sequentially encoded with mutually orthogonal values are generated at at least one of said signal ports of said array antenna;

receiving said calibration signals sequentially encoded with mutually orthogonal values by means of a coherent radio-frequency receiver;

decoding by means of a decoder signals encoded with said mutually orthogonal values, for generating decoded signals therefrom;

coupling by encoded signal coupling means said encoded signals to said decoder, as a result of which said decoder generates said decoded signals;

processing by means of a processor coupled to said decoder said decoded signals for generating signals representing at least the values of one of phase shift and attenuation,

coupling to said processor and to at least one of said phase shifters and said amplitude attenuators, for processing said decoded signals for generating signals representing at least the values of at least one set of signal levels and amplifier characteristics;

recording by means of a recorder said signals representing at least the values of one set of probe element positions and orientations and amplifier characteristics;

controlling by means of an antenna controller said signal level changing means and said orthogonal code generating means

in the case of a transmit antenna, setting the strength of the encoding signal to a plurality of signal input ports of said array antenna;

in the case of a receive antenna, setting the strength of said encoding signal to said probe;

using said orthogonal coding to perform simultaneous measurements comprising at least one of phase shift and attenuation of each amplifier corresponding to said plurality of elements in said array antenna;

changing the signal strength levels to a plurality of signal strength levels;

inserting recorded measurements of said input signal levels into said processor; and

recovering recorded output signal levels versus input signal levels from said processor to determine the characteristics of a plurality of amplifiers in said array antenna.

30. The method of claim 29 wherein said probe is positioned at at least one of (a) a distance fixed relative to said array antenna and (b) an orientation fixed relative to said array antenna.

31. The method of claim 29 wherein said probe is at a position corresponding essentially to the boresight position of one of said plurality of antenna elements.

32. The method of claim 29 wherein said probe is at a position corresponding essentially to the front of one of said plurality of antenna elements.

33. The method of claim 29 wherein said probe is at a position in the far field of said array antenna.

34. The method of claim 29, further comprising the step of

displaying at least the values of one set of signal levels and amplifier characteristics so determined by said processor.

35. The method of claim 29, wherein the property of an amplifier so determined is the output signal amplitude compared to the input signal amplitude.

36. The method of claim 29, wherein the property of an amplifier so determined is the relative phase between the output signal and the input signal.