Circuits and methods for reducing an interference signal that spectrally overlaps a desired signal

1. A method for processing complex in-phase and quadrature samples of a received signal including a desired signal and an interference signal that spectrally overlaps the desired signal, the method comprising:

applying an I/Q domain adaptive filter, narrow-band excision processing, and/or spatial nulling algorithm to partially remove the interference signal from the received signal to obtain I/Q domain processed signal samples (I k ) and (Q k ) with reduced interference;

using an amplitude circuit to obtain amplitudes (A k ) of the complex in-phase and quadrature samples using A k =√{square root over (I k 2 +Q k 2 )}and to obtain phases of the samples;

using an interference suppression circuit to reduce the interference signal in the amplitudes A k from the amplitude circuit so as to obtain processed amplitudes of the samples with reduced interference;

receiving, by a signal construction circuit, the phases of the samples from the amplitude circuit;

receiving, by the signal construction circuit, the processed amplitudes of the samples from the interference suppression circuit;

using the signal construction circuit to generate an output signal with reduced interference based on the phases and the processed amplitudes; and

optimizing filter weights in the I/Q domain, amplitude domain, and/or spatial domain to further reduce the interference signal.

2. The method of claim 1 , wherein the I/Q domain adaptive filter comprises an adaptive linear time domain filter.

3. The method of claim 1 , further comprising adaptively adjusting one or more parameters of said interference suppression circuit as to optimize a signal quality metric.

4. The method of claim 3 , wherein the signal metric comprises an interference to noise ratio (INR), an interference to signal ratio (ISR), a carrier power to noise spectral density ratio (C/No), or a signal to noise ratio (SNR).

5. The method of claim 1 , wherein the interference suppression circuit:

obtains an average amplitude of the received signal based on at least one prior amplitude of the received signal;

subtracts the amplitude from the average amplitude to obtain an amplitude residual; and

based upon an absolute value of the amplitude residual being less than or equal to a threshold, inputs the received signal into an interference suppression algorithm.

6. The method of claim 5 , wherein the threshold is varied in response to a measured peak to average power ratio.

7. The method of claim 1 , wherein the interference suppression circuit comprises a linear time domain filter.

8. The method of claim 7 , wherein the linear time domain filter comprises a time domain notch filter.

9. The method of claim 8 , wherein the linear time domain filter comprises a time domain high pass filter.

10. The method of claim 1 , wherein the interference suppression circuit:

obtains a first non-unity power of the amplitude of the received signal; and

inputs the first non-unity power of the amplitude into an interference suppression algorithm.

11. The method of claim 10 , wherein the interference suppression algorithm comprises a time domain notch filter.

12. The method of claim 10 , wherein the interference suppression algorithm comprises a time domain high pass filter.

13. The method of claim 10 , wherein the interference suppression algorithm comprises a Fourier transform based frequency excision algorithm.

14. The method of claim 1 , wherein the interference suppression circuit:

defines a plurality of clusters, each cluster having a corresponding cluster amplitude;

assigns each sample of a subset of the samples to one of the clusters based on the amplitude of that sample and based on one or more of the cluster amplitudes; and

suppresses contribution of the interference signal to each sample of the subset based on the amplitude of that sample and based on the cluster amplitude of the cluster to which that sample is assigned.

15. A circuit for processing complex in-phase and quadrature samples of a received signal including a desired signal and an interference signal that spectrally overlaps the desired signal, the circuit comprising:

circuitry implementing an I/Q domain adaptive filter, narrow-band excision processing, and/or spatial nulling algorithm to partially remove the interference signal from the received signal to obtain I/Q domain processed signal samples (I k ) and (Q k ) with reduced interference;

an amplitude circuit configured to obtain amplitudes (A k ) of the complex in-phase and quadrature samples using A k =√{square root over (I k 2 +Q k 2 )}and to obtain phases of the samples;

an interference suppression circuit configured to reduce the interference signal in the amplitudes A k from the amplitude circuit so as to obtain processed amplitudes of the samples with reduced interference;

a signal construction circuit configured to receive the phases of the samples from the amplitude circuit, receive the processed amplitudes of the samples from the interference suppression circuit, and to generate an output signal with reduced interference based on the phases and the processed amplitudes; and

circuitry configured to optimize filter weights in the I/Q domain, amplitude domain, and/or spatial domain to further reduce the interference signal.

16. The circuit of claim 15 , wherein the I/Q domain adaptive filter comprises an adaptive linear time domain filter.

17. The circuit of claim 15 , further comprising circuitry configured to adaptively adjust one or more parameters of said interference suppression circuit as to optimize a signal quality metric.

18. The circuit of claim 17 , wherein the signal metric comprises an interference to noise ratio (INR), an interference to signal ratio (ISR), a carrier power to noise spectral density ratio (C/No), or a signal to noise ratio (SNR).

19. The circuit of claim 15 , wherein the interference suppression circuit is configured to:

obtain an average amplitude of the received signal based on at least one prior amplitude of the received signal;

subtract the amplitude from the average amplitude to obtain an amplitude residual; and

based upon an absolute value of the amplitude residual being less than or equal to a threshold, input the received signal into an interference suppression algorithm.

20. The circuit of claim 19 , wherein the threshold is varied in response to a measured peak to average power ratio.

21. The circuit of claim 15 , wherein the interference suppression circuit comprises a linear time domain filter.

22. The circuit of claim 21 , wherein the linear time domain filter comprises a time domain notch filter.

23. The circuit of claim 21 , wherein the linear time domain filter comprises a time domain high pass filter.

24. The circuit of claim 15 , wherein the interference suppression circuit is configured to:

obtain a first non-unity power of the amplitude of the received signal; and

input the first non-unity power of the amplitude into an interference suppression algorithm.

25. The circuit of claim 24 , wherein the interference suppression algorithm comprises a time domain notch filter.

26. The circuit of claim 24 , wherein the interference suppression algorithm comprises a time domain high pass filter.

27. The circuit of claim 24 , wherein the interference suppression algorithm comprises a Fourier transform based frequency excision algorithm.

28. The circuit of claim 15 , wherein the interference suppression circuit is configured to:

define a plurality of clusters, each cluster having a corresponding cluster amplitude;

assign each sample of a subset of the samples to one of the clusters based on the amplitude of that sample and based on one or more of the cluster amplitudes; and

suppress contribution of the interference signal to each sample of the subset based on the amplitude of that sample and based on the cluster amplitude of the cluster to which that sample is assigned.