Method and apparatus for simultaneous synthetic aperture radar and moving target indication

• US 20080129584A1
• Filed: 04/25/2007
• Published: 06/05/2008
• Est. Priority Date: 04/28/2006
• Status: Active Grant

• Current Assignee: United States Air Force
• Original Assignee: United States Air Force
• Inventors: Wicks, Michael C., Antonik, Paul
• Granted Patent: US 7,646,326 B2
• Time in Patent Office: Days
• US Class Current: 342/25B
• CPC Class Codes: G01S 13/28 with time compression of received pulses
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/9029 specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time
• CPC Class Codes: G01S 13/904 SAR modes
• CPC Class Codes: G01S 13/9052 Spotlight mode
• CPC Class Codes: G01S 13/9054 Stripmap mode

Abstract

Method and apparatus for simultaneous synthetic aperture radar and moving target detection. A plurality of independent radio frequency signals are generated and applied to separate radiating/receiving antenna elements. Signals are generated as basis functions, such that moving target detection and synthetic aperture radar signals are constructed from individual waveform components in space, time, frequency, and coding. Waveform components are sorted and combined at reception. Received data is simultaneously processed to extract synthetic aperture radar images and moving target indication detections.

Claims

1. An apparatus for producing simultaneous synthetic aperture radar and moving target indication, comprising:

a plurality of waveform generators each producing as an output an independent radio frequency signal so as to produce a plurality of independent radio frequency signals;

wherein each of said plurality of waveform generators being independently controllable in frequency and phase;

a transmit/receive module having

a plurality of inputs and outputs, and

a channel disposed between each corresponding pair of said plurality of inputs and outputs;

wherein each of said plurality of inputs of said transmit/receive module being connected to the corresponding output of each said plurality of waveform generators, and

wherein said transmit/receive module further comprises means for;

modulating the amplitude and phase characteristics of at least one of said plurality of radio frequency signals transiting in either direction therethrough;

modulating any of said characteristics independently of any of said other characteristics; and

modulating any of said characteristics of any of said plurality of radio frequency signals independently of any other of said plurality of radio frequency signals;

a waveform control subsystem having means for applying signals to;

any of said plurality of waveform generators so as to control the frequency and phase of said radio frequency signal output therefrom; and

any of said disposed channels of said transmit/receive module so as to control said means for modulating said amplitude and phase characteristics;

at least one radio frequency radiating/receiving element being connected to at least one of said transmit/receive module outputs for

radiating radio frequency signals into free space, and

receiving from free space radio frequency signals reflected from targets; and

a signal and data processor for extracting synthetic aperture image data and moving target indication data from received radio frequency signals.

2. Said channel of claim 1, wherein said means for modulating said amplitude and phase characteristics further comprises means for radio frequency signal amplifying and phase shifting.

3. Waveform control subsystem of claim 1, wherein said means for applying signals to any of said plurality of waveform generators, further comprises:

a frequency control signal channel; and

a first phase control signal channel

corresponding to each of said plurality of waveform generators; and

wherein said means for applying signals transmit/receive module further comprises;

an amplitude control signal channel; and

a second phase control signal channel

corresponding to each of said disposed channels of said transmit/receive module.

4. Means for applying signals of claim 3, further comprising a frequency characteristic that:

is independently scalable in frequency; and

that increases for each successive said waveform generator, from a minimum frequency value at the first said waveform generator and to a maximum frequency value at the Nth said waveform generator

for each of said frequency control signal channels.

5. Frequency characteristic of claim 4, wherein said frequency characteristic varies linearly with time.

6. Frequency characteristic of claim 4, wherein said frequency characteristic varies non-linearly with time.

7. Frequency characteristic of claim 4, wherein said frequency characteristic varies over time, during the time interval between successive pulses.

8. Means for applying signals of claim 3, further comprising:

an independently scalable amplitude characteristic for each of said amplitude control signal channels.

9. Means for applying signals of claim 3, further comprising:

an independently scalable phase characteristic for each of

said first phase control signal channels; and

said second phase control signal channels.

10. Means for applying signals of claim 9, wherein said phase characteristic of said first and said second phase control signal channels varies linearly with time.

11. Means for applying signals of claim 9, wherein said phase characteristic of said first and said second phase control signal channels varies non-linearly with time.

12. Means for applying signals of claim 9, wherein said phase characteristic of said first and said second phase control signal channels varies during the interval between one pulse to the next pulse, with time.

13. Said channel of claim 1, wherein

the input of said means for amplifying is connected to said input of said channel;

the output of said means for amplifying is connected to the input of said means for phase shifting; and

the output of said means for phase shifting is connected to said output of said channel.

14. Said plurality of inputs of said transmit/receive module of claim 1, being connected to any quantity of said outputs of said plurality of waveform generators, in any combination.

15. Said signal and data processor of claim 1, further comprising:

means for storing and sorting the following;

radio frequency signals created by said plurality of waveform generators, having transited said transmit/receive module, and having been emitted from said plurality of radiating/receiving elements as radio frequency pulses;

said emitted radio frequency pulses; and

received radio frequency pulses, being those said emitted radio frequency pulses reflected by the environment and received at said plurality of radiating/receiving elements;

a pulse compression unit for compressing said received radio frequency pulses;

a synthetic aperture radar processor for producing a synthetic radar image from data derived from said compressed pulses; and

a moving target indicator processor for producing moving target indications from data derived from said compressed pulses.

16. Synthetic aperture radar processor of claim 15, further comprising:

a first corner turn memory for storing and retrieving said data according to the sequencing of said compressed pulses;

an accumulator for selectively summing only that said stored and retrieved data corresponding to selected said compressed pulses;

a receiver for selectively vector match filtering only that said summed data which corresponds to selected spatial channels; and

a registration unit for selectively summing only that said vector matched filtered data which corresponds to selected combinations of monostatically and bistatically received radio frequency pulses.

17. Moving target indicator processor of claim 15, further comprising:

a second corner turn memory for storing and retrieving said data according to the sequencing of said compressed pulses;

a differencing unit for performing pulse cancellation on said data;

a third corner turn memory for storing and retrieving said data corresponding to only those selected apertures and radiating/receiving elements on which said pulses were received;

a phase detector for generating a phase compensation signal for selectively correcting said data for phase variation;

a frequency compensation signal for selectively correcting said data for Doppler effects according to the apertures and radiating/receiving elements on which pulses corresponding to said data were received;

a multiplier for applying said phase compensation signal and said frequency compensation signal with said data output from said third corner turn memory;

an accumulator for integrating said data output from said multiplier over selected apertures and selected moving target indication filters;

a registration unit for combining data corresponding to selected combinations of monostatically and bistatically received radio frequency pulses; and

a detector for performing;

magnitude detection;

threshold setting; and

detection declaration.

18. First corner turn memory of claim 16 further comprising a data cube.

19. Second and third corner turn memories of claim 17 each further comprising a data cube.

20. Data cubes of claim 18 or claim 19, further comprising means for simultaneously storing and retrieving data sorted by

selected frequency versus selected radiating/receiving element;

selected radiating/receiving element versus selected time; and

selected frequency versus selected time.

21. Phase detector for generating a phase compensation signal of claim 17, further comprising means for producing a quantized phase vector V₁ by adding an incremental phase vector Δ

V₁ to a received phase vector V.

22. Method for producing simultaneous synthetic aperture radar and moving target indication, comprising the steps of:

generating a plurality of independent radio frequency signals, each of said plurality having

an independently variable frequency; and

an independently variable first phase characteristic;

applying frequency and first phase control signals so as to effectuate said variability;

a first step of channelizing each of said plurality of independent radio frequency signals, wherein each of said plurality of channels has a corresponding input and output;

applying amplitude and second phase control signals so as to vary the amplitude and second phase characteristics of at least one of said plurality of channels so as to modulate the amplitude and phase of said channelized radio frequency signals transiting in either direction therethrough, said step of applying further comprising;

varying any of said characteristics independently of any of said other characteristics; and

varying any of said characteristics of any of said plurality of channels independently of any other of said plurality of channels;

radiating into free space at least one of said plurality of modulated, channelized radio frequency signals through at least one radio frequency radiating/receiving element being connected to at least one of said outputs of said plurality of channels; and

receiving from free space radio frequency signals reflected from targets; and

extracting synthetic aperture image data and moving target indication data from said received radio frequency signals.

23. Method of claim 22, wherein said step of varying any of said characteristics further comprises the steps of radio frequency signal amplification and phase shifting.

24. Method of claim 22, further comprises:

a second step of channelizing frequency control signals so as to produce said independently variable frequency; and

a third step of channelizing first phase control signals so as to produce said independently variable first phase characteristic

corresponding to each of said plurality of independent radio frequency signals.

25. Step of applying amplitude and second phase control signals of claim 22, further comprising:

a fourth step of channelizing said amplitude control signals so as to vary the amplitude of said channelized radio frequency signals; and

a fifth step of channelizing said second phase control signals so as to vary said second phase characteristic of said channelized radio frequency signals.

26. Said second step of channelizing frequency control signals of claim 24, further comprising the step of independently scaling said frequency control signals such that:

said independently scaled frequency increases for each successive independent radio frequency signal of said plurality of independent radio frequency signals, from a minimum frequency value of the first said independent radio frequency signal to a maximum frequency value for the Nth said independent radio frequency signal, for each of said frequency control signal channels.

27. Said step of scaling frequency control signals of claim 26, wherein said scaling varies linearly with time.

28. Said step of scaling frequency control signals of claim 26, wherein said scaling varies non-linearly with time.

29. Said step of scaling frequency control signals of claim 26, wherein said scaling varies over time, during the time interval between successive pulses.

30. Said fourth step of channelizing said amplitude control signals of claim 25, further comprises the step of:

independently scaling the amplitude of each of said amplitude control signal channels.

31. Said third step of channelizing said first phase control signals of claim 24, further comprises the step of:

independently scaling the phase characteristic for each of said first phase control signal channels.

32. Said fifth step of channelizing said second phase control signals of claim 25, further comprises the step of:

independently scaling the phase characteristic for each of said second phase control signal channels.

33. Step of applying first phase control signals and second phase control signals of claim 22, such that said first phase characteristic said second phase characteristic vary linearly with time, independently of each other.

34. Step of applying first phase control signals and second phase control signals of claim 22, such that said first phase characteristic said second phase characteristic vary non-linearly with time, independently of each other.

35. Step of applying first phase control signals and second phase control signals of claim 22, such that said first phase characteristic said second phase characteristic vary during the interval between one pulse to the next pulse, with time, independently of each other.

36. Said step of applying amplitude and second phase control signals of claim 22, further comprises the steps of:

amplifying said radio frequency signals in any of said plurality of channels, wherein said amplification is controlled by the application of said amplitude control signals; and

phase shifting said amplified radio frequency signals, wherein said phase shifting is controlled by the application of said second phase control signals;

wherein neither the occurrence of said amplification nor said phase shifting is dependent upon the occurrence of the other.

44. Step of applying said frequency, first phase, amplitude and second phase control signals of claim 22 with particularity so as to permit simultaneous stripmap and spotlight synthetic aperture radar functionality through a common aperture of said radio frequency radiating/receiving elements.

45. Step of applying said frequency, first phase, amplitude and second phase control signals of claim 22 with particularity so as to permit simultaneous ground moving target indication and spotlight synthetic aperture radar functionality through a common aperture of said radio frequency radiating/receiving elements.

46. Step of applying said frequency, first phase, amplitude and second phase control signals of claim 22 with particularity so as to permit simultaneous communications and radar functionality through a common aperture of said radio frequency radiating/receiving elements.

47. Step of applying said frequency, first phase, amplitude and second phase control signals of claim 22 with particularity so as to provide adaptive processing by generating a steering vector.

37. Said step of extracting synthetic aperture image data and moving target indication data from said received radio frequency signals of clam 22, further comprising:

storing and sorting the following;

radio frequency signals created by said plurality of waveform generators, having transited said transmit/receive module, and having been emitted from said plurality of radiating/receiving elements into free space as radio frequency pulses;

said emitted radio frequency pulses; and

received radio frequency pulses from free space, being those said emitted radio frequency pulses reflected by the environment and received at said plurality of radiating/receiving elements;

compressing said received radio frequency pulses;

a first step of processing the data derived from said compressed pulses so as to produce a synthetic radar image therefrom; and

a second step of processing data derived from said compressed pulses so as to produce moving target indications therefrom.

38. Said first step of processing the data derived from said compressed pulses so as to produce a synthetic radar image of claim 37, further comprising the steps of:

a first step of storing and retrieving said data according to the sequencing of said compressed pulses;

a first step of selectively summing only that said stored and retrieved data corresponding to selected said compressed pulses;

selectively vector match filtering only that said summed data which corresponds to selected spatial channels; and

a second step of selectively summing only that said vector matched filtered data which corresponds to selected combinations of monostatically and bistatically received radio frequency pulses.

39. Said second step of processing data derived from said compressed pulses so as to produce moving target indications claim 37, further comprising the steps of:

a second step of storing and retrieving said data according to the sequencing of said compressed pulses;

performing pulse cancellation on said data;

a third step of storing and retrieving said data corresponding to only those selected apertures and radiating/receiving elements on which said pulses were received;

a first step of generating a phase compensation signal;

a second step of generating a frequency compensation signal;

a first step of selectively correcting said data for phase variation according to said phase compensation signal;

a second step of selectively correcting said data for Doppler effects according to the apertures and radiating/receiving elements on which pulses corresponding to said data were received, and further according to said frequency compensation signal;

integrating said phase and Doppler corrected data over selected apertures and selected moving target indication filters;

combining said corrected data corresponding to selected combinations of monostatically and bistatically received radio frequency pulses; and

performing a detection of the following;

magnitude detection; and

threshold setting;

declaring a moving target detection.

40. Said first step of storing and retrieving said data of claim 38, further comprises the steps of simultaneously storing and retrieving data sorted by

selected frequency versus selected radiating/receiving element;

selected radiating/receiving element versus selected time; and

selected frequency versus selected time.

41. Said second step of storing and retrieving said data of claim 39, further comprises the steps of simultaneously storing and retrieving data sorted by

selected frequency versus selected radiating/receiving element;

selected radiating/receiving element versus selected time; and

selected frequency versus selected time.

42. Any of said steps for simultaneously storing and retrieving data of claim 40 or claim 41, further comprising being sorted by coding.

43. Said step of generating a phase compensation signal of claim 39, further comprising computing a quantized phase vector V₁ by adding an incremental phase vector Δ

V₁ to a received phase vector V.

48. Step of performing pulse cancellation on said data in claim 39, further comprising the step of performing a plurality of two-pulse cancellation operations for each said selected aperture.

49. Said second step of processing in claim 39, further comprising the step of performing sequential phase detection.

50. Step of sequential phase detection of claim 49, further comprising the step of quantizing said received pulse phase into an arbitrary number of discrete phase steps.

51. Combining said corrected data corresponding to selected combinations of monostatically and bistatically received radio frequency pulses of claim 39, subsequent to said step of magnitude detection.