Radar detection circuit for a WLAN transceiver

• US 8,190,162 B2
• Filed: 05/02/2006
• Issued: 05/29/2012
• Est. Priority Date: 09/15/2003
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Hansen, Christopher J.
• Primary Examiner(s): Pan, Yuwen
• Assistant Examiner(s): Nguyen, Hai V
• Application Number:
  US11/415,841
• Publication Number:
  US 20060199587A1
• Time in Patent Office: 2,219 Days
• Field of Search: 455/442
• US Class Current: 455/442
• CPC Class Codes: H04B 15/02 Reducing interference from electric apparatus by means located at or near the interfering apparatus
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks

Abstract

A single chip radio transceiver includes circuitry that enables detection of radar signals to enable the radio transceiver to halt communications in overlapping communication bands to avoid interference with the radar transmitting the radar pulses. The radio transceiver is operable to evaluate a number of most and second most common pulse interval values to determine whether a traditional radar signal is present. The radio transceiver also is operable to FM demodulate and incoming signal to determine whether a non-traditional radar signal such as a bin-5 radar signal is present. After FM demodulation, the signal is averaged wherein a substantially large value is produced for non-traditional radar signals and a value approximately equal to zero is produced for a communication signal that is not FM modulated with a continuously increasing frequency signal. Gain control is used to limit incoming signal magnitude to a specified range of magnitudes.

Claims

1. A radio transceiver, comprising:

radio from end circuitry operable to produce an ingoing communication signal having in-phase and quadrature-phase components on one or more receive signal paths;

analog-to-digital converter (ADC) operatively coupled to receive the ingoing communication signal, the ADC producing an ingoing digital signal having digital in-phase and quadrature-phase signal components;

one or more processors for processing the ingoing digital signal, wherein the one or more processors inhibit transmission of outgoing digital signals over frequency bands overlapping with radar frequency bands in response to detection of a traditional radar signal or in response to detection of a non-traditional radar signal;

a radar detection block operably disposed within each of the one or more receive signal paths to receive the ingoing digital signal and operable to detect presence of the traditional radar signal and the non-traditional radar signal in the ingoing digital signal, wherein the radar detection block;

detects presence of the traditional radar signal in the ingoing digital signal by detecting pulses having a period that corresponds to traditional radar signals; and

detects presence of the non-traditional radar signal in the ingoing digital signal by detecting pulses having a period that is substantially greater than pulses for traditional radar signals and by determining that the detected pulses having a period that is substantially greater than pulses for traditional radar signals are frequency modulation (FM) modulated.

2. The radio transceiver of claim 1, wherein each radar detection block is operable to:

receive a series of incoming pulses;

produce pulse data to a FIFO;

generate a table of pulse data for a series of pulses;

evaluate the pulse data within the table to remove pulse data for pulses that do not satisfy specified traditional radar pulse characteristics;

group a plurality of pulse data within the table into groups of a specified size; and

perform radar detection processing.

3. The radio transceiver of claim 1 wherein the radio transceiver suspends radar detection processing whenever a total number of pulses within the table is less than a specified number.

4. The radio transceiver of claim 3 wherein the specified number is equal to six.

5. The radio transceiver of claim 3 wherein the radio transceiver resumes processing whenever the total number of pulses is greater than or equal to the specified number.

6. The radio transceiver of claim 1 wherein the radar detection block measures signal magnitude crossings of a plurality of thresholds and determines a rise time from a first to a second threshold, time above the second threshold, and a fall time from the second to the first threshold.

7. The radio transceiver of claim 6 wherein the radar detection block monitors at least one of a magnitude, a pulse width and timing and timing relationships of received pulses to determine whether a radar pulse has been received.

8. The radio transceiver of claim 7 wherein the radar detection block comprises a state machine for determining whether the received pulse has a specified characteristic of a radar pulse.

9. The radio transceiver of claim 7 wherein the radar detection block produces a control signal that is set to a specified logic state whenever the radar signal has been detected.

10. The radio transceiver of claim 1 further including an FM demodulator that is used to determine whether a radar signal is present.

11. The radio transceiver of claim 10 further including a gain adjustment circuit that adjusts a gain of the ingoing digital signal prior to demodulating the ingoing signal to determine if a non-traditional radar is present.

12. The radio transceiver of claim 11 further including circuitry to square and then sum the digital in-phase and quadrature phase signal components.

13. The radio transceiver of claim 12 further including gain control determination circuitry which further includes first moving average filter block for determining a moving average of the squared and summed digital in-phase and quadrature-phase signal components.

14. The radio transceiver of claim 13 wherein the gain control determination circuitry further includes a logarithmic function block for applying a log function to the output of the first moving average filter.

15. The radio transceiver of claim 14 further including a summing circuit for summing the output of the logarithmic function block with a specified offset, wherein the output of the summing circuit operates to set a gain control signal for the gain adjustment circuit for producing a gain adjusted ingoing digital signal having digital in-phase and quadrature-phase signal components.

16. The radio transceiver of claim 15 wherein the FM demodulator FM demodulates the gain adjusted ingoing digital signal having digital in-phase and quadrature phase signal componems.

17. A multiple input multiple output (MIMO) radio transceiver, comprising:

a first receive path comprising radio from end circuitry operable to produce a first ingoing digital signal;

first radar detection block operably disposed to receive the first ingoing digital signal to detect presence of a radar signal and to inhibit transmission of outgoing digital signals over frequency bands overlapping with radar frequency bands in response to detection of the radar signal;

a second receive path comprising radio from end circuitry operable to produce a second ingoing digital signal;

second radar detection block operably disposed to receive the second ingoing digital signal to detect presence of the radar signal and to inhibit transmission of outgoing digital signals in response to detection of the radar signal; and

wherein the first and second radar detection blocks each comprise logic for detecting traditional radar signals and non-traditional radar signals, wherein the first and second radar detection blocks are operable to detect presence of the non-traditional radar signal by detecting a pulse with a pulse period that is substantially longer than a traditional radar signal and having FM modulation.

18. The MIMO radio transceiver of claim 17 wherein the first and second radar detection blocks each further comprise logic for detecting non-traditional radar signals wherein the logic includes an FM demodulator for determining whether a pulse has been frequency modulated.

19. The MIMO radio transceiver of claim 18 wherein the non-traditional radar signals are bin 5 radar signals.

20. The MIMO radio transceiver of claim 17 wherein the first and second radar detection blocks each further comprise logic that functionally are operable to FM demodulate the ingoing digital signals to detect non-traditional radar signals.

21. A radio transceiver, comprising:

a first receive signal path operable to produce an ingoing signal;

a baseband processor operably disposed to receive the ingoing signal to process the ingoing signal and to inhibit transmission of outgoing digital signals over frequency bands overlapping with radar frequency bands in response to detection of a non-traditional radar signal;

a first radar detection circuit operable to receive the ingoing signal and to determine whether a non-traditional radar signal is present by determining whether the ingoing signal has a period that corresponds to a non-traditional radar signal and is FM demodulated, wherein the first radar detection circuit further includes;

FM demodulation circuit operably disposed to receive the ingoing signal, to FM demodulate the ingoing signal and to determine whether the FM demodulated ingoing signal is characterized by a specified gain characteristic based on a continually increasing frequency of the non-traditional radar signal.

22. The radio transceiver of claim 21 wherein the specified gain characteristic includes a ramped response over time with an increasing gain level.

23. The radio transceiver of claim 21 further including a gain control block to set a digital gain of the FM demodulation circuit.

24. The radio transceiver of claim 21 further including a shift register for operatively implementing gain level settings as shifts.

25. The radio transceiver of claim 21 wherein the FM demodulator comprises delay elements and cross coupled multipliers and a summing node operatively coupled to sum outputs of the multipliers.

26. The radio transceiver of claim 25 further including a moving average block for producing a moving average of a specified length of the output of the summing node wherein characteristics of the output of the moving average block indicates the presence of the non-traditional radar signal.

27. A method of detecting a non-traditional radar signal, comprising:

producing I and Q digital waveform signals from a baseband filtering block;

producing a gain control signal;

FM demodulating the I and Q digital waveform signals based in part upon the gain control signal;

averaging the FM demodulated I and Q digital waveform signals; and

evaluating the averaged FM demodulated I and Q digital waveform signals to determine presence of a non-traditional radar signal; and

inhibiting transmission of outgoing digital signals over frequency bands overlapping with radar frequency bands in response to detection of the non-traditional radar signal.

28. The method of claim 27 wherein producing the gain control signal includes summing a square of the I and Q digital waveform signal and determining a moving average of the summed square of the I and Q digital waveform signals.

29. The method of claim 28 further including calculating a log of the moving average.

30. The method of claim 29 further including summing the log of the moving average with an offset to produce a gain control signal.

31. The method of claim 27 further comprising detecting a traditional radar signal when a traditional radar signal is present having traditional radar characteristics comprised of relatively short period pulses and detecting the non-traditional radar signal having a relatively long pulse period.

32. The method of claim 31 wherein the non-traditional radar signal is a bin-5 radar signal.