Receiver including synch pulse detection and associated method

• US 7,415,082 B2
• Filed: 05/31/2005
• Issued: 08/19/2008
• Est. Priority Date: 05/31/2005
• Status: Expired due to Fees

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Beadle, Edward R., Dishman, John F.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US11/141,441
• Publication Number:
  US 20060269027A1
• Time in Patent Office: 1,176 Days
• Field of Search: 375/130, 375/136, 375132-134, 375/146, 375/143, 375/145, 375/150, 375/343, 375/152, 375/340, 375/354, 375362-368, 370/504, 370509-515
• US Class Current: 375/343
• 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

Abstract

A receiver includes a matched filter matched to a synch pulse and generates a matched filter output signal having peaks and valleys with one of the peaks corresponding to the synch pulse. An orthogonal filter is inversely matched to the synch pulse and generates an orthogonal filter output signal having peaks and valleys with one of the valleys corresponding to the synch pulse. A detector determines the synch pulse based upon a largest difference between the matched filter output signal and the orthogonal filter output signal.

Claims

1. A receiver comprising:

a matched filter being matched to a synch pulse and generating a matched filter output signal comprising a plurality of peaks and valleys with one of the peaks corresponding to the synch pulse;

an orthogonal filter being inversely matched to the synch pulse and generating an orthogonal filter output signal comprising a plurality of peaks and valleys with one of the valleys corresponding to the synch pulse; and

a detector for determining the synch pulse based upon the matched filter output signal and the orthogonal filter output signal.

2. A receiver according to claim 1 wherein said detector detects the synch pulse based upon a largest difference between the matched filter output signal and the orthogonal filter output signal.

3. A receiver according to claim 1 wherein the synch pulse comprises a frequency hopped synch pulse.

4. A receiver according to claim 1 wherein said matched filter and said orthogonal filter have inputs coupled in parallel for receiving an input signal comprising a plurality of data pulses and a plurality of synch pulses.

5. A receiver according to claim 4 wherein the input signal comprises N_p observation intervals, with N_p being equal to or greater than 1, and further comprising:

a first non-coherent integrator coupled to an output of said matched filter for non-coherently integrating samples accumulated by said matched filter over the N_p observation intervals; and

a second non-coherent integrator coupled to an output of said orthogonal filter for non-coherently integrating samples accumulated by said orthogonal filter over the N_p observation intervals.

6. A receiver according to claim 5 further comprising a constant false alarm rate (CFAR) detector coupled to an output of said first non-coherent integrator for comparing the non-coherently integrated samples accumulated by said matched filter over the N_p observation intervals to a noise threshold.

7. A receiver according to claim 6 further comprising a noise estimator coupled to said CFAR detector for setting the noise threshold based upon the input signal.

8. A receiver according to claim 7 wherein said noise estimator comprises an ordered-statistic CFAR detector and sets the noise threshold for the N_p observation intervals by

determining a first variance of the plurality of synch and data pulses within the N_p data frames, and removing pulses exceeding a first variance threshold;

and

determining a second variance on the plurality of synch and data pulses not exceeding the first variance threshold, and removing pulses exceeding a second variance threshold;

the noise threshold being set based upon a remaining input signal for the N_p observation intervals after removal of pulses exceeding the first and second variance thresholds.

9. A receiver according to claim 1 wherein the receiver comprises an asynchronous receiver.

10. A receiver comprising:

an input for receiving an input signal comprising a plurality of data pulses and a plurality of synch pulses;

a matched filter coupled to the input and being matched to the plurality of synch pulses and generating a plurality of matched filter output signals, at least one of the matched filter output signals comprising a plurality of peaks and valleys with one of the peaks corresponding to one of the synch pulses;

a constant false alarm rate (CFAR) detector coupled to an output of said matched filter for comparing each matched filter output signal to a noise threshold so that data pulses exceeding the noise threshold are removed;

an orthogonal filter coupled to the input and being inversely matched to the plurality of synch pulses and generating a plurality of orthogonal filter output signals, at least one of the orthogonal filter output signals comprising a plurality of peaks and valleys with one of the valleys corresponding to one of the synch pulses; and

a detector coupled to an output of said CFAR detector and to an output of said orthogonal filter for determining the plurality of synch pulses based upon the respective matched and orthogonal filter output signals.

11. A receiver according to claim 10 wherein said detector detects the plurality of synch pulses based upon the matched filter output signals and the orthogonal filter output signals.

12. A receiver according to claim 10 wherein the input signal comprises a frequency hopped input signal.

13. A receiver according to claim 10 wherein the input signal is divided into N_p data frames, with N_p being equal to or greater than 1, and further comprising:

a first non-coherent integrator coupled between said matched filter and said CFAR detector for non-coherently integrating samples accumulated by said matched filter over the N_p observation intervals; and

a second non-coherent integrator coupled between said orthogonal filter and said detector for non-coherently integrating samples accumulated by said orthogonal filter over the N_p observation intervals.

14. A receiver according to claim 13 wherein said CFAR detector compares the non-coherently integrated samples accumulated by said matched filter over the N_p observation intervals to the noise threshold.

15. A receiver according to claim 10 further comprising a noise estimator coupled between the input and said CFAR detector for setting the noise threshold based upon the input signal.

16. A receiver according to claim 15 wherein the input signal is divided into N_p observation intervals, with N_p being equal to or greater than 1;

and wherein said noise estimator comprises an ordered-statistic CFAR detector and sets the noise threshold for the N_p observation intervals by

determining a first variance of the plurality of synch and data pulses within the N_p data frames, and removing any pulse exceeding a first variance threshold; and

determining a second variance on the plurality of synch and data pulses not exceeding the first variance threshold, and removing any pulse exceeding a second variance threshold;

the noise threshold being set based upon the remaining input signal for the N_p observation intervals after removal of pulses exceeding the first and second variance thresholds.

17. A receiver according to claim 10 wherein the receiver comprises an asynchronous receiver.

18. A method for detecting a synch pulse in a receiver comprising a matched filter matched to the synch pulse and an orthogonal filter inversely matched to the synch pulse, the method comprising:

generating a matched filter output signal comprising a plurality of peaks and valleys with one of the peaks corresponding to the synch pulse;

generating an orthogonal filter output signal comprising a plurality of peaks and valleys with one of the valleys corresponding to the synch pulse; and

determining the synch pulse based upon the matched filter output signal and the orthogonal filter output signal.

19. A method according to claim 18 wherein the detector detects the synch pulse based upon a largest difference between the matched filter output signal and the orthogonal filter output signal.

20. A method according to claim 18 wherein the input signal comprises N_p observation intervals, with N_p being equal to or greater than 1, and further comprising:

non-coherently integrating samples accumulated by the matched filter over the N_p observation intervals using a first non-coherent integrator coupled to an output of the matched filter; and

non-coherently integrating samples accumulated by the orthogonal filter over the N_p observation intervals using a second non-coherent integrator coupled to an output of the orthogonal filter.

21. A method according to claim 20 further comprising comparing the non-coherently integrated samples accumulated by the matched filter over the N_p data frames to a noise threshold using a constant false alarm rate (CFAR) detector coupled to an output of the first non-coherent integrator.

22. A method according to claim 21 further comprising setting the noise threshold based upon the input signal using a noise estimator coupled to the CFAR detector.

23. A method according to claim 22 wherein the noise estimator comprises an ordered-statistic CFAR detector and sets the noise threshold for the N_p observation intervals by

determining a first variance of the plurality of synch and data pulses within the N_p observation intervals, and removing any pulse exceeding a first variance threshold;

and

determining a second variance on the plurality of synch and data pulses not exceeding the first variance threshold, and removing any pulse exceeding a second variance threshold;

the noise threshold being set based upon a remaining input signal for the N_p observation intervals after removal of pulses exceeding the first and second variance thresholds.