Patent ID: 8855254

Claim:
A method for implementing a multirate digital decimating filter for filtering received symbol data comprising: sampling the received symbol data at a selected sample rate; pre-averaging the sampled received symbol data from three samples per symbol to two samples per symbol by passing one of the three samples to an output, and averaging the other two samples before sending them to the output, wherein the averaging comprises digitally adding the other two samples and bit shifting the result; convolving the pre-averaged samples with decimated finite impulse response (FIR) aperture impulse response coefficients; generating, based at least in part on convolving the pre-averaged samples, decimated in-phase (I) output samples and decimated quadrature-phase (Q) output samples; convolving the pre-averaged samples with shifted decimated FIR aperture impulse response coefficients to produce zero-crossing transition samples; and adjusting the sample rate based at least in part on averaging the zero-crossing transition samples.