Interference suppression using repeated reduced rank adaptive filtering in fractional fourier transform (FrFT) domains
AssigneeThe Aerospace Corporation
InventorSeema Sud
Life of this patent
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Abstract
A signal-of-interest (SOI) may be separated from interference and/or noise using repeated reduced rank minimum mean-square error Fractional Fourier Transform (MMSE-FrFT) filtering and a low rank adaptive multistage Wiener filter (MWF). A number of stages in the MWF, L, may be chosen such that at the Lth stage, the MSE between the SIM estimate and the true SW is less than or equal to an error threshold ∈ (e.g., ∈=0.001). By combining these filtering techniques, significant improvement in reducing the mean-square error (MSE) may be realized over single stage MMSE-FrFT, repeated MMSE-FrFT, and MMSE-FFT algorithms—indeed, by an order of magnitude or more.
Claims31
A computer-implemented method of performing repeated reduced rank MMSE-MWF-FrFT filtering, comprising:
- computing, by a computing system, minimum mean-square error (MMSE) filter coefficients over all a for a current optimum filter to be applied to a received signal, where a is a rotational parameter;
- computing, by the computing system, a best a for the current filter and a current smallest MMSE;
- updating the received signal, by the computing system, using the current smallest MMSE;
- when the current smallest MMSE is not less than or equal to an error threshold, repeating, by the computing system, the computation of the MMSE filter coefficients, the computation of the best a and the current smallest MMSE, and the updating of the received signal using the current smallest MMSE until the current smallest MMSE is less than or equal to the error threshold;
- and
- when the current smallest MMSE is less than or equal to the error threshold, extracting a signal-of-interest (SOI), by the computing system, from the updated received signal.
A computer program configured to perform repeated reduced rank MMSE-MWF-FrFT filtering embodied on a non-transitory computer-readable medium, the program configured to cause at least one processor to:
- (1) compute minimum mean-square error (MMSE) filter coefficients over all values of a rotational parameter a for a current optimum filter to be applied to a received signal;
- (2) compute a best value of a and compute a current smallest MMSE;
- (3) update the received signal using the current smallest received signal;
- and
- (4) while the current smallest MMSE is greater than an error threshold, repeat steps (1)-(3) until the current smallest MMSE is less than or equal to the error threshold, wherein
- when the error threshold is reached or exceeded, L sets of a values and filter weights are provided to be applied to data in the received signal following a training sequence.
A computing system, comprising:
- memory storing computer program instructions for performing repeated reduced rank MMSE-MWF-FrFT filtering;
- and
- at least one processor configured to execute the computer program instructions, wherein the instructions, together with the at least one processor, are configured to cause the apparatus to:
- apply reduced rank MMSE-MWF-FrFT filtering to a received signal for at least one stage L, obtaining a current smallest MMSE at each stage, and
- when the current smallest MMSE is less than or equal to an error threshold, extract a signal-of-interest (SOI) from the updated received signal, wherein
- when the error threshold is reached or exceeded, L sets of a values and filter weights are provided to be applied to data in the received signal following a training sequence to extract the SOI from the received signal.
Dependencies are inferred from the claim text.