Estimation and mitigation of swept-tone interferers in frequency-hopped systems

An apparatus for estimating a swept-tone interferer in a frequency-hopping system, the frequency-hopping system comprising a plurality of hops, each of the plurality of hops comprising each of a plurality of hop bandwidths, the apparatus comprising:

• an analog-to-digital converter configured to sample a composite signal over each of the plurality of hop bandwidths to generate an initial set of samples for each of the plurality of hops, wherein the composite signal comprises a signal of interest and the swept-tone interferer, and wherein each of the initial set of samples comprises a first set of samples and a second set of samples;
• a delay estimation module configured to determine a number of the first set of samples for each of the plurality of hops;
• a signal conditioning module configured to truncate the first set of samples from the initial set of samples for each of the plurality of hops, and concatenate the truncated set of samples for each of the plurality of hops to generate a reconstructed composite signal, wherein the swept-tone interferer in the reconstructed composite signal is modeled as a magnitude-periodic signal, wherein the magnitude-periodic signal comprises a plurality of phase-rotated pulses, and wherein each of the plurality of phase-rotated pulses comprises a common pulse shape and a distinct phase rotation;
• a period estimation module configured to estimate a period of the magnitude-periodic signal;
• an initial pulse estimation module configured to generate an initial estimate of the common pulse shape based on at least the period, wherein a length of the initial estimate of the common pulse shape is equal to the period;
• a pulse and phase estimation module configured to:
• generate a plurality of phase estimates based on a plurality of epochs and the initial estimate of the common pulse shape, wherein the plurality of epochs corresponds to non-overlapping, contiguous segments of the reconstructed composite signal, wherein a length of each of the plurality of epochs is equal to the period, wherein each of the plurality of epochs comprises the common pulse shape, and wherein each of the plurality of phase estimates is generated for each of the plurality of epochs,
• generate a plurality of phase de-rotated pulse estimates, wherein each of the plurality of phase de-rotated pulse estimates is based on each of the plurality of epochs and each of the plurality of phase estimates, and
• compute a weighted average of the plurality of phase de-rotated pulse estimates to generate a final estimate of the common pulse shape;
• and
• an interference estimation module configured to generate an estimate of the swept-tone interferer based on the final estimate of the common pulse shape and the plurality of phase estimates.

A method for estimating a swept-tone interferer in a frequency-hopping system, the frequency-hopping system comprising a plurality of hops, each of the plurality of hops comprising a respective hop bandwidth, the method comprising:

• receiving a composite signal over each of the respective hop bandwidths, wherein the composite signal comprises a signal of interest and the swept-tone interferer;
• and
• for each of the plurality of frequency hops:
• modeling the swept-tone interferer over the respective hop bandwidth as a magnitude-periodic signal, wherein the magnitude-periodic signal comprises a plurality of phase-rotated pulses, and wherein each of the plurality of phase-rotated pulses comprises a common pulse shape and a distinct phase rotation;
• generating an energy signal based on the respective composite signal;
• estimating a period of the magnitude-periodic signal based on the energy signal;
• generating an initial estimate of the common pulse shape based on the period and energy detection of the energy signal, wherein a length of the initial estimate of the common pulse shape is equal to the period;
• generating a plurality of phase estimates based on a plurality of epochs and the initial estimate of the common pulse shape, wherein the plurality of epochs corresponds to non-overlapping, contiguous segments of the composite signal, wherein a length of each of the plurality of epochs is equal to the period, wherein each of the plurality of epochs comprises the common pulse shape, and wherein each of the plurality of phase estimates is generated for each of the plurality of epochs;
• generating a plurality of phase de-rotated pulse estimates, wherein each of the plurality of phase de-rotated pulse estimates is based on each of the plurality of epochs and each of the plurality of phase estimates;
• computing a weighted average of the plurality of phase de-rotated pulse estimates to generate a final estimate of the common pulse shape;
• and
• generating an estimate of the swept-tone interferer over the respective hop bandwidth based on the final estimate of the common pulse shape and the plurality of phase estimates.