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

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.