Method and apparatus for detecting the presence of a signal in a frequency band using non-uniform sampling

• US 8,553,808 B2
• Filed: 12/13/2006
• Issued: 10/08/2013
• Est. Priority Date: 12/13/2006
• Status: Expired due to Fees

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Inventors: Luthra, Ajay K.
• Primary Examiner(s): Singh, Hirdepal
• Application Number:
  US11/609,980
• Publication Number:
  US 20080143573A1
• Time in Patent Office: 2,491 Days
• Field of Search: 375/130, 375135-137, 375145-148, 375/150, 375/245, 375/260, 375/295, 375/316, 375/342, 375/343, 375/355, 375/242, 375/250, 375/254, 375/267, 375/359, 375/371, 375/340, 375/43
• US Class Current: 375/340
• CPC Class Codes: H03M 1/1265 Non-uniform sampling
• CPC Class Codes: H04L 27/265 Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators H04L27/26524 takes precedence

Abstract

A method and apparatus for detecting the presence of a signal in a frequency band using non-uniform sampling includes an analog to digital converter (ADC) (110) for sampling an analog input signal (105) to create discrete signal samples (115), an ADC exciter (120) for exciting the ADC to sample at non-uniform time periods, a digital filter (130) for converting the discrete signal samples into an energy versus frequency spectrum (300), and an energy comparator (140) coupled to an output of the digital filter. The energy comparator (140) detects the presence of any frequency bands exceeding an energy setpoint.

Claims

1. A method for detecting a presence of a signal comprising of:

generating a pseudo random sequence to determine non-uniform time periods;

sampling an analog input signal at the non-uniform time periods to produce discrete signal samples;

determining that a signal is present in a frequency band when an energy versus frequency spectrum of the discrete signal samples exceeds an energy setpoint at the frequency band.

2. The method according to claim 1, wherein sampling comprises:

detecting a slope of the analog input signal and changing a local sampling rate based on the slope of the analog input signal.

3. The method according to claim 2, wherein the local sampling rate is increased if the slope is steeper.

4. The method according to claim 3, wherein the local sampling rate is increased if the slope is steeper positively.

5. The method according to claim 3, wherein the local sampling rate is increased if the slope is steeper negatively.

6. The method according to claim 2, wherein the local sampling rate is decreased if the slope is flatter.

7. The method of claim 1, wherein the determining comprises:

converting the discrete signal samples into the energy versus frequency spectrum using digital spectral filtering.

8. The method of claim 7, wherein converting comprises:

taking Fourier transforms of the discrete signal samples.

9. The method of claim 1, wherein determining comprises:

setting the energy setpoint.

10. The method of claim 9, wherein setting comprises:

empirically determining a value for the energy setpoint.

11. The method of claim 9, wherein setting comprises:

selecting the energy setpoint that lies below a specified number of frequency bands of the energy versus frequency spectrum.

12. The method of claim 9, wherein setting comprises:

multiplying an average side lobe height by a factor greater than one, wherein the product of the multiplication provides the energy setpoint.

13. The method according to claim 1, further comprising:

taking more discrete signal samples at the non-uniform time periods if a side lobe energy level is greater than expected.

14. An apparatus for use in detecting a presence of a signal comprising:

an analog to digital converter (ADC) for sampling an analog input signal to create the discrete signal samples;

an ADC exciter, coupled to the ADC, for exciting the ADC to sample at non-uniform time periods;

a digital filter, coupled to an output of the ADC, for converting the discrete signal samples into an energy versus frequency spectrum; and

an energy comparator, coupled to an output of the digital filter, to detect a presence of a lobe in the energy versus frequency spectrum exceeding an energy setpoint.

15. The apparatus according to claim 14, wherein the ADC comprises:

a switch that closes at the non-uniform time periods and opens otherwise.

16. The apparatus according to claim 14, wherein the ADC exciter comprises:

a slope detector for detecting a slope of the analog input signal and adjusting a local sampling rate based on the slope of the analog input signal.

17. The apparatus according to claim 14, wherein the ADC exciter comprises:

a pseudo random generator for generating a pseudo random sequence that determines the non-uniform time periods.

18. The apparatus according to claim 14, further comprising:

a processor, coupled to the energy comparator, for determining the energy setpoint.