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

• US 9,094,272 B2
• Filed: 08/30/2013
• Issued: 07/28/2015
• Est. Priority Date: 12/13/2006
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Inventors: Luthra, Ajay K.
• Primary Examiner(s): Singh, Hirdepal
• Application Number:
  US14/015,562
• Publication Number:
  US 20140003556A1
• Time in Patent Office: 697 Days
• Field of Search: 375/130, 375135-137, 375145-148, 375/150, 375/245, 375/260, 375/295, 375/316, 375/320, 375/322, 375338-340, 375/342, 375/343, 375/346, 375/350, 375/355
• US Class Current: 1/1
• 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:

receiving an analog input signal;

sampling the analog input signal at non-uniform time periods to produce discrete signal samples acquired at non-uniform time periods, wherein sampling includes detecting a slope of the analog input signal and changing a local sampling rate based on the slope of the analog input signal;

transforming the discrete signal samples to a frequency domain to produce an energy versus frequency spectrum of the discrete signal samples; and

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 the local sampling rate is increased if the slope is steeper.

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

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

5. The method according to claim 1, wherein the local sampling rate is decreased if the slope is flatter.

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

receiving an analog input signal;

sampling the analog input signal at non-uniform time periods to produce discrete signal samples acquired at non-uniform time periods, wherein the sampling comprises generating a pseudo random sequence that determines the non-uniform time periods;

transforming the discrete signal samples to a frequency domain to produce an energy versus frequency spectrum of the discrete signal samples; and

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.

7. The method of claim 6, 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 6, wherein determining comprises:

setting the energy setpoint.

10. 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.

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

empirically determining a value for the energy setpoint.

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

receiving an analog input signal;

taking discrete signal samples of the analog input signal, wherein the discrete signal samples are acquired at non-uniform time periods;

transforming the discrete signal samples to a frequency domain to produce an energy versus frequency spectrum of the discrete signal samples;

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

setting the energy setpoint; and

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.

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

receiving an analog input signal;

taking discrete signal samples of the analog input signal, wherein the discrete signal samples are acquired at non-uniform time periods, wherein more discrete signal samples are taken at the non-uniform time periods if a side lobe energy level is greater than expected;

transforming the discrete signal samples to a frequency domain to produce an energy versus frequency spectrum of the discrete signal samples; and

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.