Coherent synchronization and processing of pulse groups

• US 5,818,371 A
• Filed: 12/12/1996
• Issued: 10/06/1998
• Est. Priority Date: 12/12/1996
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon TI Systems, Inc. (Rtx Corporation)
• Inventors: Lu, Chyi Haw, Scott, Hugh L., Holmes, Jerry D.
• Primary Examiner(s): Hoff, Marc S.
• Application Number:
  US08/764,828
• Time in Patent Office: 663 Days
• Field of Search: 341/122, 341/157, 342/192
• US Class Current: 341/122
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation
• CPC Class Codes: H04L 7/0054 Detection of the synchronisation error by features other than the received signal transition by means of signal transition H04L7/033
• CPC Class Codes: H04L 7/027 extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit
• CPC Class Codes: H04L 7/0334 Processing of samples having at least three levels, e.g. soft decisions
• CPC Class Codes: H04L 7/06 the synchronisation signals differing from the information signals in amplitude, polarity or frequency or length
• CPC Class Codes: H04L 7/08 the synchronisation signals recurring cyclically

Abstract

A method and system for synchronization of pulse groups without a synchronization signal which comprises selecting a plurality of equal time length coherent processing intervals from a stream of data in the time domain, generally analog data. The data in each of the coherent processing intervals is sampled during each of N equal pulse repetition intervals to provide samples of data, each sampling taking place for an equal portion of the pulse repetition interval. Each of the samples of data is identified according to the position thereof in the associated coherent processing interval. The time domain data is converted to frequency domain data on the basis of the position of the time domain data in the coherent processing interval, all of the samples with the same position in a different coherent processing interval being separately collectively converted. The frequency domain data is then compensated for phase rotation by determining the length of the coherent processing interval, the length of the pulse repetition interval and the duration of the sampling and altering the phase of the frequency domain data in response thereto. An FFT is provided of selected ones of the frequency domain data. The results of the FFT of the selected ones of the frequency domain data are then displayed.

Claims

1. A method of synchronization of pulse groups without a synchronization signal comprising the steps of:

(a) selecting a plurality of equal time length coherent processing intervals from a stream of data in the time domain;

(b) sampling the data in each of said coherent processing intervals during each of N equal pulse repetition intervals to provide samples of data, each sampling taking place for an equal portion of a said pulse repetition interval;

(c) identifying each of said samples of data according to the position thereof in the associated coherent processing interval;

(d) converting the time domain data to frequency domain data on the basis of said position, all of said samples with the same position in a different coherent processing interval being separately collectively converted;

(e) compensating said frequency domain data for phase rotation; and

(f) providing an FFT of selected ones of said frequency domain data.

2. The method of claim 1 wherein said stream of data in the time domain is analog data.

3. The method of claim 1 wherein said step of compensating comprises the steps of determining the length of said coherent processing interval, the length of said pulse repetition interval and the duration of said sampling and altering the phase of said frequency domain data in response thereto.

4. The method of claim 2 wherein said step of compensating comprises the steps of determining the length of said coherent processing interval, the length of said pulse repetition interval and the duration of said sampling and altering the phase of said frequency domain data in response thereto.

5. The method of claim 2 further including the step of providing an ADC, converting the bandwidth of said analog data to within the bandwidth of said ADC and converting the converted analog data to digital data with said ADC.

6. The method of claim 4 further including the step of providing an ADC, converting the bandwidth of said analog data to within the bandwidth of said ADC and converting the converted analog data to digital data with said ADC.

7. The method of claim 1 further including the step of displaying the results of the FFT of said selected ones of said frequency domain data.

8. The method of claim 2 further including the step of displaying the results of the FFT of said selected ones of said frequency domain data.

9. The method of claim 3 further including the step of displaying the results of the FFT of said selected ones of said frequency domain data.

10. The method of claim 4 further including the step of displaying the results of the FFT of said selected ones of said frequency domain data.

11. The method of claim 5 further including the step of displaying the results of the FFT of said selected ones of said frequency domain data.

12. The method of claim 6 further including the step of displaying the results of the FFT of said selected ones of said frequency domain data.

13. The method of claim 1 wherein said step of compensating comprises, assuming {X_n } is the FFT of the original (uncompensated) time domain pulse waveform, the multiplication:

space="preserve" listing-type="equation">Y.sub.n =X.sub.n *e.sup.j2φ

na/M

where;

n=1,2,3 . . . (M-1);

{Y_n } is now the FFT of the phase compensated data;

M is the FFT transform length; and

a is the misalignment time value from Table B that is appropriate for the particular pulse being compensated.

14. The method of claim 3 wherein said step of compensating comprises, assuming {X_n } is the FFT of the original (uncompensated) time domain pulse waveform, the multiplication:

space="preserve" listing-type="equation">Y.sub.n =X.sub.n *e.sup.j2φ

na/M

where;

n=1,2,3 . . . (M-1);

{Y_n } is now the FFT of the phase compensated data;

M is the FFT transform length; and

a is the misalignment time value from Table B that is appropriate for the particular pulse being compensated.

15. The method of claim 7 wherein said step of compensating comprises, assuming {X_n } is the FFT of the original (uncompensated) time domain pulse waveform, the multiplication:

space="preserve" listing-type="equation">Y.sub.n =X.sub.n *e.sup.j2φ

na/M

where;

n=1,2,3 . . . (M-1);

{Y_n } is now the FFT of the phase compensated data;

M is the FFT transform length; and

a is the misalignment time value from Table B that is appropriate for the particular pulse being compensated.

16. The method of claim 9 wherein said step of compensating comprises, assuming {X_n } is the FFT of the original (uncompensated) time domain pulse waveform, the multiplication:

space="preserve" listing-type="equation">Y.sub.n =X.sub.n *e.sup.j2φ

na/M

where;

n=1,2,3 . . . (M-1);

{Y_n } is now the FFT of the phase compensated data;

M is the FFT transform length; and

a is the misalignment time value from Table B that is appropriate for the particular pulse being compensated.

17. A system for synchronization of pulse groups without a synchronization signal comprising:

(a) selecting means for selecting a plurality of equal time length coherent processing intervals from a stream of data in the time domain;

(b) sampling means for sampling the data in each of said coherent processing intervals during each of N equal pulse repetition intervals to provide samples of data, each sampling taking place for an equal portion of a said pulse repetition interval;

(c) identifying means for identifying each of said samples of data according to the position thereof in the associated coherent processing interval;

(d) a converter for converting the time domain data to frequency domain data on the basis of said position, all of said samples with the same position in a different coherent processing interval being separately collectively converted;

(e) compensating means for compensating said frequency domain data for phase rotation; and

(f) FFT means for providing an FFT of selected ones of said frequency domain data.

18. The system of claim 17 wherein said stream of data in the time domain is analog data.

19. The system of claim 17 wherein said compensating means comprises means to determine the length of said coherent processing interval, the length of said pulse repetition interval and the duration of said sampling and altering the phase of said frequency domain data in response thereto.

20. The system of claim 18 wherein said compensating means comprises means to determine the length of said coherent processing interval, the length of said pulse repetition interval and the duration of said sampling and altering the phase of said frequency domain data in response thereto.

21. The system of claim 18 further including an ADC, means to convert the bandwidth of said analog data to within the bandwidth of said ADC, said ADC converting the converted analog data to digital data.

22. The system of claim 20 further including an ADC, means to convert the bandwidth of said analog data to within the bandwidth of said ADC, said ADC converting the converted analog data to digital data.

23. A system for synchronization of pulse groups without a synchronization signal comprising:

(a) selecting circuitry for selecting a plurality of equal time length coherent processing intervals from a stream of data in the time domain;

(b) sampling circuitry for sampling the data in each of said coherent processing intervals during each of N equal pulse repetition intervals to provide samples of data, each sampling taking place for an equal portion of a said pulse repetition interval;

(c) identifying circuitry for identifying each of said samples of data according to the position thereof in the associated coherent processing interval;

(d) a converter for converting the time domain data to frequency domain data on the basis of said position, all of said samples with the same position in a different coherent processing interval being separately collectively converted;

(e) compensating circuitry for compensating said frequency domain data for phase rotation; and

(f) FFT circuitry for providing an FFT of selected ones of said frequency domain data.

24. The system of claim 23 wherein said stream of data in the time domain is analog data.

25. The system of claim 23 wherein said compensating circuitry comprises circuitry to determine the length of said coherent processing interval, the length of said pulse repetition interval and the duration of said sampling and altering the phase of said frequency domain data in response thereto.

26. The system of claim 24 wherein said compensating circuitry comprises circuitry to determine the length of said coherent processing interval, the length of said pulse repetition interval and the duration of said sampling and altering the phase of said frequency domain data in response thereto.

27. The system of claim 24 further including an ADC, circuitry to convert the bandwidth of said analog data to within the bandwidth of said ADC, said ADC converting the converted analog data to digital data.

28. The system of claim 26 further including an ADC, circuitry to convert the bandwidth of said analog data to within the bandwidth of said ADC, said ADC converting the converted analog data to digital data.