Radio sensor for detecting wireless microphone signals and a method thereof

• US 8,233,862 B2
• Filed: 02/16/2009
• Issued: 07/31/2012
• Est. Priority Date: 02/15/2008
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Gaddam, Vasanth R., Ghosh, Monisha
• Primary Examiner(s): Dao, Minh D
• Application Number:
  US12/865,478
• Publication Number:
  US 20100311341A1
• Time in Patent Office: 1,261 Days
• Field of Search: 455/150.1, 455/161.1, 455/197.1, 455/62, 455/68, 455/71, 455/84, 455/63.3, 381/104, 381/92, 381/321, 704/205
• US Class Current: 455/150.1
• CPC Class Codes: H04L 27/00 Modulated-carrier systems

Abstract

Wireless microphone signals are detected by processing an input signal to determine a number of frequency bins within a channel frequency band having an energy level above a first predefined threshold (S510); identifying locations of the frequency bins having an energy level above the first predefined threshold, when the number of bins is greater than zero (S520, S530); for each frequency bin having an energy level above the first predefined threshold, processing signals within a narrow frequency band of the frequency bin (S570); determining a number of signal peaks within the narrow frequency band that are above a second predefined threshold (S575); and generating a message indicating a presence or an absence of a microphone signal based on the number of signal peaks (S590, S595).

Claims

1. A radio sensor (100) for detecting wireless microphone signals, comprising:

a fast Fourier transform (FFT) module (130) for transforming an input signal into a frequency domain signal;

an accumulator (140) for accumulating the output signals of the FFT module (130); and

a decision unit (150) for comparing an output signal of the accumulator (140) to a predefined threshold and generating a message indicating a presence or an absence of a microphone signal based on the comparing result.

2. The radio sensor of claim 1, further comprising:

a radio frequency (RF) front end (110) for selecting a channel frequency band of only one channel; and

an analog-to-digital converter (ADC) (120) for digitizing the input signal.

3. The radio sensor of claim 2, wherein the FFT module is further capable of pre-FFT processing the input signal, the pre-FFT processing comprising:

downshifting the input signal to a direct current (DC) signal;

applying a low pass filter with a bandwidth of the frequency band; and

down sampling the filtered signal.

4. The radio sensor of claim 1, wherein a signal present message is generated if at least one frequency bin within the output signal of the accumulator is above the predefined threshold.

5. A radio sensor (300) for detecting microphone wireless signals, comprising:

a fast Fourier transform (FFT) module (330) for transforming an input signal into a frequency domain signal;

a frequency domain filter (340) for filtering an output signal of the FFT module (330);

an accumulator (350) for accumulating the output signals of the frequency domain filter (340); and

a decision unit (360) for comparing an output signal of the accumulator (340) to a predefined threshold and generating a message indicating a presence or an absence of a microphone signal based on the comparing result.

6. The radio sensor of claim 5, further comprising:

a radio frequency (RF) front end (310) for selecting a channel frequency band of only one channel; and

an analog-to-digital converter (ADC) (320) for digitizing the input signal.

7. The radio sensor of claim 6, wherein the FFT module is further capable of pre-FFT processing the input signal, the pre-FFT processing comprising:

downshifting the input signal to a direct current (DC) signal;

applying a low pass filter with a bandwidth of the channel frequency band; and

down sampling the filtered signal.

8. The radio sensor of claim 5, wherein filtering the output signal of the FFT module comprises, for each frequency bin within the output signal, calculating a weighted sum of a current frequency bin, M bins immediately preceding the current frequency bin, and M bins immediately following the current frequency bin, wherein M is determined based on a size of the FFT module and a bandwidth of a signal being detected.

9. The radio sensor of claim 5, wherein a signal present message is generated if at least one frequency bin within the output signal of the accumulator is above the predefined threshold.

10. A method (500) for detecting wireless microphone signals, comprising:

processing an input signal to determine a number of frequency bins within a channel frequency band having an energy level above a first predefined threshold (S510);

identifying locations of the frequency bins having an energy level above the first predefined threshold, when the number of bins is greater than zero (S520, S530);

for each frequency bin having an energy level above the first predefined threshold, processing signals within a narrow frequency band of the frequency bin (S570);

determining a number of signal peaks within the narrow frequency band that are above a second predefined threshold (S575); and

generating a message indicating a presence or an absence of a microphone signal based on the number of signal peaks (S590, S595).

11. The method of claim 10, wherein processing the input signal further comprising:

transforming the input signal into a frequency domain signal using a FFT operation;

accumulating the output signals of the FFT operation; and

comparing the accumulating results to the first predefined threshold.

12. The method of claim 10, wherein processing the signals within the narrow frequency band of the frequency bin further comprising:

setting a band pass filter across a center frequency of the frequency bin, wherein the frequency band of the band pass filter is as the microphone-signal frequency band (S560);

converting an output signal of the band pass filter to a direct current (DC) signal;

down sampling the signal

transforming the down-sampled signal to a frequency domain signal using a FFT operation; and

accumulating the output signals of the FFT operation.

13. The method of claim of claim 10, wherein a signal present message is generated when the number of signal peaks is above a predefined number of maximum peaks.

14. The method of claim 10, wherein the channel frequency band is 6 MHz and wherein the narrow frequency band is 200 kHz.

15. A computer readable medium having stored thereof computer executable code for detecting wireless microphone signals, comprising:

processing an input signal to determine a number of frequency bins within a channel frequency band having an energy level above a first predefined threshold (S510);

identifying locations of the frequency bins having an energy level above the first predefined threshold, when the number of bins is greater than zero (S520, S530);

for each frequency bin having an energy level above the first predefined threshold, processing signals within a microphone-signal frequency band of the frequency bin (S570);

determining a number of signal peaks within the microphone-signal frequency band that are above a second predefined threshold (S575); and

generating a message indicating a presence or an absence of a microphone signal based on the number of signal peaks (S590, S595).