Signal pulse detection scheme for use in real-time spectrum analysis

• US 20050002473A1
• Filed: 08/02/2004
• Published: 01/06/2005
• Est. Priority Date: 04/22/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Kane, Brian F., Sugar, Cary L., Kloper, David S.
• Granted Patent: US 7,292,656 B2
• Time in Patent Office: Days
• US Class Current: 375/316
• CPC Class Codes: G01R 23/16 Spectrum analysis; Fourier analysis
• CPC Class Codes: H04L 1/1664 the supervisory signal being transmitted together with payload signals; piggybacking
• CPC Class Codes: H04L 1/1867 Arrangements specially adapted for the transmitter end
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements

Abstract

A spectrum analysis engine (SAGE) that comprises a spectrum analyzer component, a signal detector component, a universal signal synchronizer component and a snapshot buffer component. The spectrum analyzer component generates data representing a real-time spectrogram of a bandwidth of radio frequency (RF) spectrum. The signal detector detects signal pulses in the frequency band and outputs pulse event information entries output, which include the start time, duration, power, center frequency and bandwidth of each detected pulse. The signal detector also provides pulse trigger outputs which may be used to enable/disable the collection of information by the spectrum analyzer and the snapshot buffer components. An alternative pulse detection module is provided that tracks signal pulses by comparing peak data from successive FFT cycles with existing signal pulse data that is derived from comparing peak data for prior FFT cycles. Peaks for new FFT cycles are matched to data associated with signal pulses determined to be occurring over many FFT intervals.

Claims

1. A method for detecting signal pulses from received radio frequency (RF) energy, comprising steps of:

a. storing peak data describing at least one of frequency, bandwidth and power for each of one or more peaks of RF energy;

b. comparing the peak data for one or more peaks detected for a current sampling cycle with the peak data for one or more peaks detected during a previous sampling cycle; and

c. based on the step of comparing, storing a list of signal pulses representing the occurrence of peaks having similar peak data over multiple sampling cycles.

2. The method of claim 1, and further comprising the step of comparing the bandwidth of each of the peaks with a minimum bandwidth threshold and discarding data for peaks that do not exceed the minimum bandwidth threshold.

3. The method of claim 1, and further comprising a step of detecting peaks of RF energy as power values above a power threshold at a set of frequencies.

4. The method of claim 3, wherein the step of detecting peaks comprises detecting peaks of RF energy as power values above the power threshold at a set of contiguous frequencies.

5. The method of claim 3, wherein the step of detecting peaks comprises comparing power values at a plurality of frequencies with the power threshold, wherein the power threshold for the comparison at a particular frequency may vary with a power level at a frequency near the particular frequency.

6. The method of claim 1, wherein the step of detecting a peak comprises detecting power values that exceed the power threshold at Fast Fourier Transform (FFT) frequency bins.

7. The method of claim 1, wherein the step of storing peak data comprises storing data describing a lefthand frequency of each of the one or more peaks.

8. The method of claim 1, wherein the step of storing peak data comprises storing data describing a center frequency of each of the one or more peaks.

9. The method of claim 1, wherein the step of storing peak data comprises storing data describing a righthand frequency of each of the one or more peaks.

10. The method of claim 1, wherein the step of storing peak data comprises storing an incoming peak list comprising the peak data for one or more peaks detected for a current sampling cycle.

11. The method of claim 10, wherein the step of storing a list of signal pulses comprises storing an existing pulse list containing pulse data for one or more signal pulses that have resulted over one or more sampling cycles, wherein the pulse data describes at least one of frequency, bandwidth and power for each signal pulse.

12. The method of claim 11, wherein the step of comparing comprises comparing peak data in the incoming peak list with pulse data in the existing pulse list, and depending on the comparison of the peak data for peaks in the incoming peak list with the pulse data of signal pulses in the existing pulse list (a) storing an updated pulse list by adding to the existing pulse list data for a new signal pulse;

(b) modifying data in the existing pulse list to extend a time duration of a signal pulse in the existing pulse list with data for a peak in the incoming pulse list;

or (b) removing data in the existing pulse list for a signal pulse that is no longer occurring.

13. The method of claim 12, and further comprising the step of storing the contents of the updated pulse list into the existing pulse list for comparison against peak data in the incoming pulse list for a new sampling cycle.

14. The method of claim 12, wherein the step of storing an incoming peak list comprises storing the peak data for one or more peaks detected for a current sampling cycle in order of increasing frequency, and the step of storing an existing pulse list comprises storing pulse data for one or more pulses in order of increasing frequency.

15. The method of claim 1, and wherein the step of comparing comprises comparing peak data with pulse data in the list subject to configurable values for at least one of a bandwidth deviation, a frequency deviation and a power deviation.

16. The method of claim 1, wherein the step of comparing comprises matching peaks for the current sampling cycle with the data in the list of signal pulses, and further comprising updating the list of signal pulses with data for a peak that matches data for a signal pulse in the list to thereby (a) extend a duration the signal pulse for a period of time corresponding to the sampling cycle;

(b) add new signal pulse data the list for a peak associated with the current sampling cycle;

or (c) terminate a signal pulse in the list.

17. The method of claim 16, wherein the step of comparing further comprises comparing frequency, bandwidth and power of peak data for one or more peaks associated with the current sampling cycle with bandwidth and power of signal pulses in the list.

18. The method of claim 1, and further comprising the step of outputting signal pulse data describing characteristics of signal pulses detected over a period of time.

19. The method of claim 18, wherein the step of outputting signal pulse data comprises outputting data describing at least one of time of occurrence, power, frequency, bandwidth and duration for each signal pulse.

20. The method of claim 18, wherein the step of outputting signal pulse data comprises outputting ranges for at least one of power, frequency, bandwidth and duration for each signal pulse.

21. The method of claim 18, wherein the step of outputting signal pulse data comprises outputting averages for at least one of power, frequency, bandwidth and duration for signal pulses detected over time.

22. The method of claim 18, and further comprising the step of joining pulse data for similar pulses that may have been broken up due to signal fading and other conditions.

23. The method of claim 18, and further comprising the step of filtering out signal pulse data for pulses having a duration less than a minimum duration threshold.

24. The method of claim 1, and further comprising the step of storing digital signals representing samples of received RF energy when a signal pulse of a particular type is detected.

25. A signal pulse detector that detects signal pulses from received radio frequency (RF) energy, comprising:

a. a peak calculation module that computes peak data describing at least one of frequency, bandwidth and power for each of one or more peaks of RF energy that exceed a power threshold and a minimum bandwidth threshold during each of a plurality of sampling cycles;

b. a first memory that stores an incoming peak list comprising peak data for one or more peaks detected for a current sampling cycle; and

c. a pulse comparison module coupled to the first memory, and which compares the peak data in the incoming peak list with existing pulse data to determine whether to (i) extend an existing pulse;

(2) terminate an existing pulse;

or (3) add a new pulse to the existing pulse data.

26. The signal pulse detector of claim 25, and further comprising a second memory that stores the existing pulse data in an existing pulse list for signal pulses determined to occur based on peak data in the incoming peak list, and that stores an updated pulse list containing changes to the existing pulse list based on comparison of data in the incoming peak list for the current sampling cycle with the pulse data in the existing pulse list.

27. The signal pulse detector of claim 25, wherein the pulse comparison module (a) writes data to the updated pulse list to add data for a new signal pulse;

(b) extends a time duration of a signal pulse in the existing pulse list with data associated with a peak in the incoming peak list;

or (c) removes data for a signal pulse in the existing pulse list that has terminated.

28. The signal pulse detector of claim 25, wherein the peak calculation module and pulse comparison module are implemented by digital logic gates.

29. The signal pulse detector of claim 28, wherein the peak calculation module, pulse comparison module and first memory are implemented on an integrated circuit.

30. The signal pulse detector of claim 25, and further comprising a memory interface module coupled to the second memory and to the pulse comparison module, wherein the pulse comparison module triggers the memory interface module to read the contents of the second memory in order to output signal pulse data.

31. A system comprising the signal pulse detector of claim 25, and further comprising a Fast Fourier Transform (FFT) block that receives as input a digital signal representing received RF energy and computes FFT values for a plurality of frequency bins for a time interval;

and a power calculation block coupled to the FFT block that computes the power at each frequency bin at each time interval, wherein the power is supplied as input to the peak detector.

32. The system of claim 31, and further comprising a memory that stores one or more of:

a. a running sum of the power at each frequency bin over time intervals;

b. a duty count comprising a running sum at each time interval of the number of times the power at each frequency bin exceeds the power threshold;

c. a maximum power for each frequency bin for the current and prior time intervals; and

d. a running count of the number of time intervals in which a certain number of peaks have been detected.

33. A system comprising the signal pulse detector of claim 25, and further comprising a memory controller coupled to the pulse comparison module, wherein the signal pulse detector outputs a trigger signal in response to detecting a certain type of pulse that causes the memory controller to store digital samples of received RF energy for a time interval in a memory.

34. The system of claim 33, wherein the memory controller writes a timestamp identifying a time associated with an occurrence of the trigger signal.

35. The system of claim 33, wherein the memory controller continuously stores the digital samples in the memory and stops storing in response to the trigger signal.

36. A system comprising the signal pulse detector of claim 25, and further comprising a memory controller coupled to the pulse comparison module, wherein the signal pulse detector outputs a trigger signal in response to detecting a certain type of pulse that causes the memory controller to write to a memory the output of the power calculation block for one or more time intervals.

37. The signal pulse detector of claim 25, and further comprising a configuration register that stores configuration data for the power threshold and the minimum bandwidth threshold.

38. The signal pulse detector of claim 37, wherein the configuration register further stores configuration data for a bandwidth deviation, a frequency deviation and a power deviation for use by the pulse comparison module when comparing peak data in the incoming peak list with existing pulse data for determining whether or not to extend an existing pulse.

39. The signal pulse detector of claim 25, and further comprising a memory interface circuit that outputs content of the existing pulse list to a memory.

40. A system comprising the signal pulse detector of claim 39, and further comprising a processor coupled to the memory that processes the signal pulse data stored in the memory.

41. The system of claim 40, wherein the processor joins pulse data for similar pulses that may have been broken up due to signal fading and other conditions.

42. A spectrum analysis system comprising:

a. a Fast Fourier Transform (FFT) block that receives as input a digital signal representing received RF energy and computes FFT values for a plurality of frequency bins for a time interval;

b. a power calculation block coupled to the FFT block that computes the power at each frequency bin at each time interval;

c. a peak detector that receives as input an output of the power calculation block for successive time intervals, detects one or more peaks in the output of the power calculation block and outputs data describing peaks of RF energy for each time interval;

d. a signal pulse detector coupled to receive as input the output of the peak detector;

i. a peak calculation module that computes peak data describing at least one of frequency, bandwidth and power for each of one or more peaks of RF energy that exceed a power threshold and a minimum bandwidth threshold during each of a plurality of time intervals;

ii. a first memory that stores an incoming peak list comprising peak data for one or more peaks detected for a current time interval; and

iii. a pulse comparison module coupled to the first memory, and which compares the peak data in the incoming peak list with existing pulse data to determine whether to extend or terminate an existing pulse, or to add a new pulse to the existing pulse data; and

e. a statistics computation module coupled to the power calculation module that computes one or more of a running sum of the power at each frequency bin over time intervals;

a duty count comprising a running sum at each time interval of the number of times the power at each frequency bin exceeds the power threshold;

a maximum power for each frequency bin for the current and prior time intervals; and

a running count of the number of time intervals in which a certain number of peaks have been detected.

43. The spectrum analysis system of claim 42, and further comprising a second memory that stores the existing pulse data in an existing pulse list for signal pulses determined to occur based on peak data in the incoming peak list, and that stores an updated pulse list containing changes to the existing pulse list based on comparison of data in the incoming peak list for the current time interval with the pulse data in the existing pulse list.

44. The spectrum analysis system of claim 42, wherein the pulse comparison module writes data to the updated pulse list to (a) add data for a new signal pulse, (b) extend a time duration of a signal pulse in the existing pulse list with data associated with a peak in the incoming peak list and (c) remove data for a signal pulse in the existing pulse list that has terminated.

45. The spectrum analysis system of claim 42, wherein the peak calculation module and pulse comparison module are implemented by digital logic gates.

46. The spectrum analysis system of claim 43, and further comprising a memory interface module coupled to the second memory and to the pulse comparison module, wherein the pulse comparison module triggers the memory interface module to read the contents of the second memory in order to output signal pulse data.