Compact, sensitive, low power device for broadband radar detection

• US 6,043,771 A
• Filed: 12/21/1998
• Issued: 03/28/2000
• Est. Priority Date: 12/21/1998
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Clark, Casey K., Creighton, Mark A.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US09/219,002
• Time in Patent Office: 463 Days
• Field of Search: 342/13, 342/16-20, 342/159-164, 342/175, 342/192-197, 342/89, 375/316
• US Class Current: 342/13
• CPC Class Codes: G01S 7/021 Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals

Abstract

A method and system is provided for real-time detection of important multiple pulsed or CW signals of varying amplitude and frequency, from a group of simultaneously intercepted wideband intermediate frequency (IF) channels. The method is implemented in a channelized receiver system with a parameter encoder which filters the IF signals in a time-shared mode by dividing the IF channel bandwidth into progressively decreasing sub-band levels, multiplexing the IF signals from each sub-band and analyzing the time multiplexed IF signals to obtain the IF signal parameters. The system is flexible with programmable parameters and has the ability to eliminate most of the spurious signals with high probability of interception of the real signals. Conventional pulse descriptor words, band limited pre-detection samples and time-frequency pulse images are output for subsequent analysis or tactical application.

Claims

1. A parameter encoder for receiving at least one wideband intermediate frequency (IF) channel of IF signals from a simultaneously intercepted plurality of IF channels each having a predetermined channel bandwidth, and for real-time detection of important IF signals of varying amplitude and frequency from said IF channel, comprising:

a cascade of bandpass filters having filters grouped in a plurality of filter levels, each said filter level filtering said IF signals by dividing each IF channel bandwidth into a plurality of sub-band levels, each said sub-band level having a progressively narrower bandwidth than preceding sub-band levels;

a pulse detection means for receiving said IF signals in a sub-band time multiplexed mode and for analyzing said IF signals to obtain IF signal parameters;

a control processor means for determining the important IF signals according to the IF signal parameters;

a channel arbitration means for selecting the IF channel corresponding to the important IF signal; and

a pulse descriptor word (PDW) assembler means connected to said control processor means and said channel arbitration means for producing a pulse descriptor word for each said important IF signal.

2. The encoder of claim 1 wherein:

said cascade of bandpass filters comprises

a first level filter/decimate means for filtering the IF signals in time-shared mode by dividing the IF channel bandwidth into a plurality of first level sub-bands of equal bandwidth and adjacent frequencies, according to a first level sub-band bandwidth filtering ratio,

a first level multiplexer for sub-band time multiplexing the IF signals from the first level filter/decimate means,

a second level filter/decimate means for filtering the IF signals in time-shared mode by dividing each said first level sub-band into a plurality of second level sub-bands of equal bandwidth and adjacent frequencies, according to a second level sub-band bandwidth filtering ratio, and

a second level multiplexer for sub-band time multiplexing the IF signals from the second level filter/decimate means, wherein

the first level multiplexer has a time multiplexed output in accordance with the first level sub-band bandwidth filtering ratio and the second level multiplexer has a time multiplexed output in accordance with the second level sub-band bandwidth filtering ratio, and

the first and second level multiplexers sum the time-shared IF signals from each said first and second level filter/decimate means, respectively, to obtain speed necessary for real time processing.

3. The encoder of claim 2 wherein the pulse detection means comprises

a first detection means for detecting the IF signals within the IF channel bandwidth, and

a second detection means for each of said sub-band levels,

one of said second detection means receiving the sub-band time multiplexed IF signals from the first level multiplexer, and another of said second detection means receiving the sub-band time multiplexed IF signals from the second level multiplexer.

4. The encoder of claim 3 wherein each of said first and second detection means includes:

a noise level estimator means for providing noise levels,

a frequency/phase measurement means for providing frequency and phase information for the IF signal, and

an amplitude averaging/stable level tracking means having a multiple threshold limit means for providing IF signal amplitude, arrival time, termination time, signal stability, and signal-to-noise ratio information to the channel arbitration means.

5. The encoder of claim 4 wherein the multiple threshold limit means includes programmable pulse detection means for detecting both short duration pulses and long duration pulses.

6. The encoder of claim 5 wherein the programmable pulse detection means includes a multi-level integrated pulse present means for determining two programmable thresholds (IPP) according to an M out of N voting scheme, to determine pulse presence, and for performing IF signal qualification and stability assessment one sub-band at the time.

7. The encoder of claim 6 wherein each said IF channel processed in the cascade of bandpass filters has a frequency bandwidth from 20 to 100 MHz.

8. The encoder of claim 7 further comprising means for determining presence and characteristics of carrier modulation within the important IF signal.

9. The encoder of claim 8 wherein the first and second level filter/decimate means comprises 4-way filter/decimate filters;

and

said cascade of bandpass filters comprises digital filters.

10. The encoder of claim 8 wherein the IF signals are represented as complex numbers;

and

further comprising a rectangular-to-polar converter and a phase vector integrator.

11. The encoder of claim 4 wherein said frequency/phase measurement means further comprises an intra-pulse modulation analyzer.

12. The encoder of claim 5 wherein said programmable pulse detection means comprises an output including a frequency and time pattern, and wherein said pulse detection means comprises a pulse image generation device.

13. The encoder of claim 1 further comprising means for transmitting said pulse descriptor word to a remote processing facility.

14. The encoder of claim 1 further comprising:

means for digitally storing said important IF signals;

means for filtering said digitally stored important IF signals to a predetermined bandwidth in accordance with the energy detection of important signal information; and

means for transmitting said filtered important IF signals to a remote processing facility.

15. A channelized parameter measurement receiver system for real-time detection of important IF signals from a simultaneously intercepted plurality of wideband high frequency RF signals of varying amplitude and frequency, comprising:

an RF converter for converting the high frequency RF signals into wideband intermediate frequency (IF) signals;

a channelized receiver for dividing the wideband IF signals into a plurality of IF channels; and

a parameter encoder for receiving at least one IF channel of IF signals and detecting the IF signal characteristics in time-shared mode, comprising;

a cascade of bandpass filters having filters grouped in a plurality of filter levels, each said filter level filtering said IF signals by dividing the IF channel bandwidth into a sub-band level, each said sub-band level having a progressively narrower bandwidth than preceding sub-band levels,

a pulse detection means for receiving said IF signals in sub-band time multiplexed mode, and for analyzing said IF signals to obtain the IF signal parameters according to a predetermined sensitivity,

a control processor means for controlling the parameter encoder according to commands from an external source; and

a pulse descriptor word (PDW) assembler means connected to said control processor means for producing a pulse descriptor word for each said important IF signal.

16. The system of claim 15 wherein said cascade of bandpass filters comprises:

a first level filter/decimate means for filtering the IF signals in time-shared mode by dividing the IF channel bandwidth into a plurality of first level sub-bands of equal bandwidth and adjacent frequencies, according to a first level sub-band bandwidth filtering ratio,

a first level multiplexer for sub-band time multiplexing the IF signals from the first level filter/decimate means,

a second level filter/decimate means for filtering the IF signals in time-shared mode by dividing each said first level sub-band into a plurality of second level sub-bands of equal bandwidth and adjacent frequencies, according to a second level sub-band bandwidth filtering ratio, and

a second level multiplexer for sub-band time multiplexing the IF signals from the second level filter/decimate means; and

wherein

the first level multiplexer has a time multiplexed output in accordance with the first level sub-band bandwidth filtering ratio and the second level multiplexer has a time multiplexed output in accordance with the second level sub-band bandwidth filtering ratio, and

the first and second level multiplexers sum the time-shared IF signals from each said first and second level filter/decimate means, respectively.

17. The system of claim 16 wherein the pulse detection means comprises:

a first detection means for the IF signals within the IF channel bandwidth; and

a second detection means for each said sub-band level; and

wherein

one of said second detection means receives the sub-band time multiplexed IF signals from the first level multiplexer, and another of said second detection means receives the sub-band time multiplexed IF signals from the second level multiplexer.

18. The system of claim 17 wherein each of said first and second detection means includes:

a noise level estimator means for providing noise levels;

a frequency/phase measurement means for providing frequency and phase information concerning the IF signal; and

an amplitude averaging/stable level tracking means having a multiple threshold means for providing IF signal amplitude, arrival time, termination time, signal stability, and signal-to-noise ratio information to the channel arbitration means.

19. The system of claim 18 wherein the multiple threshold limit means includes programmable pulse detection means, to produce separate pulse presence signals for each said sub-band, for detecting both short duration pulses and long duration pulses.

20. The system of claim 19 wherein the programmable pulse detection means includes a multi-level integrated pulse present means for determining programmable thresholds according to an M out of N voting scheme, to determine pulse presence, and for performing IF signal qualification and stability assessment one sub-band at the time.

21. The system of claim 20 wherein each of said IF channels processed in the cascade of bandpass filters has a frequency bandwidth of from 40 to 100 MHz and the wideband IF signals have a frequency bandwidth of from 0.5 to 4.0 GHz.

22. The system of claim 21 further comprising means for determining presence and characteristics of carrier modulation within the important IF signal.

23. The system of claim 22 wherein:

the first and second level filter/decimate means comprises 4-way filter/decimate filters;

said cascade of bandpass filters comprises digital filters; and

said first and second detection means comprises analog detection means.

24. The system of claim 22 wherein the IF signals are represented as complex numbers, and the parameter encoder further comprises a rectangular-to-polar converter and a phase vector integrator.

25. The system of claim 22 wherein the control processor controls the system by interpreting external commands, selecting sub-band and threshold settings, maintaining system status, and determining noise levels of the IF channels, and

the parameter encoder further comprises a PDW processor means using the pulse descriptor words to generate tactical and analytical reports.

26. A method for receiving at least one wideband intermediate frequency (IF) of IF signals from a simultaneously intercepted plurality of narrower IF channels, and for real-time detection of important IF signals of varying amplitude and frequency from said IF channel, comprising the steps of:

(a) analyzing said IF signals to obtain IF signal parameters according to a predetermined sensitivity;

(b) filtering said IF signals in a time-shared mode by dividing the IF channel bandwidth into a sub-band level;

(c) multiplexing said IF signals from each said sub-band level;

(d) receiving said time multiplexed IF signals from each said sub-band and analyzing said IF signals to obtain the IF signal parameters according to a predetermined sensitivity;

(e) repeating the steps of filtering, multiplexing and analyzing said IF signals by progressively decreasing the sub-band level bandwidth until reaching the predetermined final bandwidth and sensitivity;

(f) determining the important IF signals according to the IF signal parameters; and

(g) producing a pulse descriptor word for each said important IF signal.