Method and apparatus for real-time adaptive interference cancellation in dynamic environments

An adaptive frequency domain filter adapted for responding to interference signals comprising:

• a fast Fourier transform (FFT) element for transforming digitized baseband signals from a time domain to a frequency domain and providing a plurality of frequency bins, each frequency bin corresponding to a specific frequency;
• a delay element for delaying said frequency bins by a predetermined amount and providing delayed frequency bins;
• a multiplier for either passing or notching each of said delayed frequency bins;
• an inverse FFT element for transforming said delayed frequency bins provided by said multiplier from said frequency domain to said time domain;
• and
• a bin weight calculator for providing a control signal that directs said multiplier to either notch or pass each of said frequency bins, said control signal being time coincident with each of said delayed frequency bins provided by said delay element, said bin weight calculator including:
• a noise estimator for estimating a noise level across frequency for each block of a plurality of blocks of said frequency bins;
• a processor for comparing an individual bin level to said noise level;
• and
• an output for providing said control signal to notch one of said frequency bins when said individual bin level exceeds said noise level by a short duration signal predetermined threshold, and
• wherein the processor includes means for comparing said individual bin level to said noise level to detect an interference signal present in only one of said frequency bins, said interference signal having a duration as small as a time duration of said one of said frequency bins, and wherein the output includes means for providing said control signal to notch said one of said frequency bins for said time duration of said one of said frequency bins.

An adaptive frequency domain filter that responds to interference signals comprising:

• a fast Fourier transform (FFT) element for transforming digitized baseband signals from a time domain to a frequency domain and providing a plurality of frequency bins, each frequency bin corresponding to a frequency range;
• a delay element for delaying said frequency bins by a predetermined amount and providing delayed frequency bins;
• a multiplier for notching said delayed frequency bins that contain said interference signals;
• an inverse FFT element for transforming said delayed frequency bins provided by said multiplier from said frequency domain to said time domain;
• and
• a bin weight calculator for sampling said plurality of frequency bins provided by said FFT element and providing a control signal that directs said multiplier to notch one of said delayed frequency bins containing said interference signals, said control signal being time coincident with each of said delayed frequency bins provided by said delay element, said bin weight calculator including:
• a noise estimator for estimating a noise level across frequency for each of a block of said frequency bins;
• a bin averager for averaging bins across time for each of a plurality of frequency bins of a same frequency and providing average bin levels across time for each frequency bin of said plurality;
• a processor for comparing said average bin levels across time with said noise level across frequency;
• and
• an output for providing said control signal to notch said one of said delayed frequency bins containing said interference signals when said average bin levels across time exceeds said noise level for a long duration signal predetermined threshold.

An adaptive frequency domain filter that responds to interference signals comprising:

• a fast Fourier transform (FFT) element for transforming digitized baseband signals from a time domain to a frequency domain and providing a plurality of frequency bins, each frequency bin corresponding to a specific frequency;
• a delay element for delaying said frequency bins by a predetermined amount and providing delayed frequency bins;
• a multiplier for either passing or notching each of said delayed frequency bins;
• an inverse FFT element for transforming said delayed frequency bins provided by said multiplier from said frequency domain to said time domain;
• and
• a bin weight calculator for providing a control signal that directs said multiplier to either notch or pass each of said frequency bins, said control signal being time coincident with each of said delayed frequency bins provided by said delay element,
• said bin weight calculator including a sampler for sampling blocks of bins of said plurality of frequency bins provided by said FFT element, and wherein said bin weight calculator provides said control signal to direct said multiplier to either notch or pass one of said frequency bins based on a detection of an interference signal of either a short duration or a long duration, wherein said short duration is as small as a time associated with said one of said frequency bins, and wherein said long duration is greater than a time associated with said blocks of bins sampled by said sampler.

An adaptive frequency domain filter that responds to interference signals comprising:

• a fast Fourier transform (FFT) element for transforming digitized baseband signals from a time domain to a frequency domain and providing a plurality of frequency bins, each frequency bin corresponding to a specific frequency;
• a delay element for delaying said frequency bins by a predetermined amount and providing delayed frequency bins;
• a multiplier for notching said delayed frequency bins that contain said interference signals;
• an inverse FFT element for transforming said delayed frequency bins provided by said multiplier from said frequency domain to said time domain;
• and
• a bin weight calculator for providing a control signal that directs said multiplier to notch said frequency bins that contain said interference signals, said control signal being time coincident with each of said delayed frequency bins provided by said delay element, wherein:
• said FFT element includes a first buffer for providing an overlap between windowed blocks of time samples of said frequency bins wherein each subsequent windowed block of frequency bins is time-delayed from a previous block and has said overlap with said previous block, and a Fourier transform processor which performs a Fourier transform on each of said windowed blocks of time samples;
• said bin weight calculator includes a sampler for sampling said windowed blocks provided by said FFT element;
• and
• said inverse FFT element includes an inverse Fourier transform processor for calculating an inverse Fourier transform on each of said windowed blocks of time samples, a second buffer for storing said windowed blocks of time samples that overlap, and a summer for adding said windowed blocks of time samples that overlap, wherein a scaled version of said digitized baseband signals results when said windowed blocks are repetitively added together delayed by multiples of said overlap.

A method for responding to a short duration interference signal comprising the steps of:

• transforming digitized baseband signals from a time domain to a frequency domain and providing blocks of frequency bins, each frequency bin corresponding to a specific frequency range;
• delaying said frequency bins by a predetermined amount and to provide delayed frequency bins;
• transforming said delayed frequency bins from said frequency domain to said time domain;
• estimating a noise level across frequency for each block of said frequency bins, each block of frequency bins being delayed in time from a previous block, and each block corresponding to a time sample;
• comparing an individual bin level to said noise level for each block of frequency bins;
• and
• providing a control signal to notch one of said delayed frequency bins containing said short duration interference signal when said individual bin level exceeds said noise level by a predetermined threshold.

A method for responding to interference signals comprising the steps of:

• transforming digitized baseband signals from a time domain to a frequency domain and providing a plurality of frequency bins, each frequency bin corresponding to a specific frequency;
• delaying said frequency bins by a predetermined amount and to provide delayed frequency bins;
• transforming said delayed frequency bins from said frequency domain to said time domain;
• estimating a noise level across frequency for each of a block of said frequency bins;
• comparing an individual bin level to said noise level;
• and
• notching a frequency bin when said individual bin level exceeds said noise level by a short duration signal predetermined thresholds,
• wherein the comparing step compares said individual bin level to said noise level to detect an interference signal present in only one of said frequency bins, said interference signal having a duration as small as a time duration of said one of said frequency bins, and wherein the notching step includes the step of notching said one of said frequency bins for said time duration.

A method for canceling interference signals comprising the steps of:

• transforming digitized baseband signals from a time domain to a frequency domain and providing a plurality of frequency bins, each frequency bin corresponding to a specific frequency range;
• delaying said frequency bins by a predetermined amount and to provide delayed frequency bins;
• transforming said delayed frequency bins from said frequency domain to said time domain;
• estimating a noise level across frequency for each of a block of said frequency bins;
• comparing an individual bin level to said noise level;
• and
• notching a frequency bin containing said interference signals when said individual bin level exceeds said noise level by a short duration signal predetermined threshold,
• wherein the transforming digitized baseband signals step provides blocks of said frequency bins, each block being time delayed from other blocks and having a frequency overlap, said method further comprising the steps of:
• averaging bins across time for each of said plurality of frequency bins having a same frequency and providing average bin levels across time for each frequency bin said plurality;
• comparing said average bin levels across time with said noise level across frequency;
• and
• providing a control signal to notch one of said frequency bins that contain said interference signals when said average bin levels across time exceeds said noise level for a long duration signal predetermined threshold.

A method for canceling interference signals comprising the steps of:

• transforming digitized baseband signals from a time domain to a frequency domain and providing a plurality of frequency bins, each frequency bin corresponding to a specific frequency;
• sampling blocks of said frequency bins;
• delaying said frequency bins by a predetermined amount and to provide delayed frequency bins;
• transforming said delayed frequency bins from said frequency domain to said time domain;
• estimating a noise level across frequency for each of a block of said frequency bins;
• comparing an individual bin level to said noise level;
• notching a frequency bin when said individual bin level exceeds said noise level by a short duration signal predetermined threshold,
• wherein the notching step includes the step of providing a control signal to either notch or pass one of said frequency bins based on a detection of an interference signal of either a short duration or a long duration by the comparing step, and
• wherein said short duration is as small as a time associated with said one of said frequency bins, and wherein said long duration is greater than a time associated with said blocks of bins sampled in the sampling step.

A method for canceling interference signals comprising the steps of:

• transforming digitized baseband signals from a time domain to a frequency domain and providing a plurality of frequency bins, each frequency bin corresponding to a specific frequency range;
• delaying said frequency bins by a predetermined amount and to provide delayed frequency bins;
• transforming said delayed frequency bins from said frequency domain to said time domain;
• estimating a noise level across frequency for each of a block of said frequency bins;
• comparing an individual bin level to said noise level;
• and
• notching a frequency bin containing said interference signals when said individual bin level exceeds said noise level by a short duration signal predetermined threshold,
• wherein:
• the transforming digitized baseband signals step includes the step of providing an overlap between windowed blocks of time samples of said frequency bins wherein each subsequent windowed block of frequency bins is time-delayed from a previous block and has said overlap with said previous block, and
• wherein the method further comprises the step of performing a Fourier transform on each of said windowed blocks of time samples, and
• wherein the transforming said delayed frequency bins step includes the steps of performing an inverse Fourier transform on each of said windowed blocks of time samples;
• storing said windowed blocks of time samples that overlap;
• and adding said windowed blocks of time samples that overlap, and
• wherein a scaled version of said digitized baseband signals results when said windowed blocks are repetitively added together delayed by multiples of the overlap.

An adaptive frequency domain filter that responds to interference signals comprising:

• a fast Fourier transform (FFT) element for transforming digitized baseband signals from a time domain to a frequency domain and providing a plurality of frequency bins, each frequency bin corresponding to a specific frequency;
• a delay element for delaying said frequency bins by a predetermined amount and providing delayed frequency bins;
• a multiplier for either passing or notching each of said delayed frequency bins;
• an inverse FFT element for transforming said delayed frequency bins provided by said multiplier from said frequency domain to said time domain;
• and
• a bin weight calculator for providing a control signal that directs said multiplier to either notch or pass each of said frequency bins, said control signal being time coincident with each of said delayed frequency bins provided by said delay element,
• wherein said bin weight calculator includes:
• a noise estimator for estimating a noise level across frequency for each of a block of said frequency bins;
• a bin averager for averaging bins across time for each of a plurality of frequency bins of a same frequency and providing average bin levels across time for each frequency bin said plurality;
• a processor for comparing an individual bin level to said noise level, and for comparing said average bin levels across time with said noise level across frequency;
• and
• an output for providing said control signal to notch one of said frequency bins either when said individual bin level exceeds said noise level by a short duration signal predetermined threshold, or when said average bin levels across time exceeds said noise level for a long duration signal predetermined threshold.