System and method for estimation and compensation of radiated feedback coupling in a high gain repeater

1. A method for estimating a coupling between an input antenna and an output antenna of an on-frequency repeater, comprising:

measuring a signal in a signal path of the on-frequency repeater;

dithering a forward gain of the signal path; and

calculating iteratively the coupling based on the measured signal and the dithered forward gain;

wherein calculating iteratively the coupling comprises:

calculating a residual feedback coupling;

finding significant residual coefficients;

obtaining a list of dominant delay taps corresponding to the significant residual coefficients;

updating residual coefficients based on the list of dominant delay taps; and

repeating the above steps using updated residual coefficients until the list of dominant delay taps is empty.

2. A method as set out in claim 1 , wherein calculating the residual feedback coupling comprises:

measuring a first power spectrum value of the signal in the signal path;

varying a value of the forward gain;

measuring a second power spectrum value of the signal in the signal path;

calculating a first function using a difference between the first power spectrum value and the second power spectrum value;

calculating a second function using a sum of the first power spectrum value and the second power spectrum value; and

calculating the residual feedback using the first function and the second function.

3. A method as set out in claim 2 , wherein varying the value of the forward gain comprises varying the forward gain between an upper limit and a lower limit, and wherein an average value of the varied forward gain is a nominal forward gain.

4. A method as set out in claim 2 , further comprising removing an outlier in the measurement of the power spectrum.

5. A method as set out in claim 4 , wherein the minimum delay through the repeater is T min and wherein removing an outlier comprises:

calculating a differential auto-correlation of the measured first power spectrum and the measured second power spectrum of the signal in the signal path at varying time delays; and

if the differential auto-correlation is larger than a predetermined threshold for a delay less than T min , then removing the measured first power spectrum and the measured second power spectrum.

6. A method as set out in claim 1 , wherein obtaining the list of dominant delay taps comprises identifying the dominant delay taps by comparing a value of a delay tap with a predetermined threshold.

7. A method as set out in claim 6 , wherein the predetermined threshold is three times an average of the value of the delay tap.

8. A method as set out in claim 1 , further comprising compensating for the coupling based on the iteratively-calculated coupling to reduce the coupling between the input antenna and the output antenna.

9. A method as set out in claim 8 , further comprising increasing the forward gain of the repeater after the coupling is reduced.