Abstract: Certain embodiments of the invention may include systems and methods for implementing a multirate digital decimating filter for filtering received symbol data. The method may include sampling the received symbol data at a selected sample rate, pre-averaging the sampled received data to provide two samples per symbol; convolving the pre-averaged samples with decimated finite impulse response (FIR) aperture impulse response coefficients to produce detected 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.

Abstract: Certain embodiments of the invention may include systems and methods for implementing a multirate digital interpolating filter. According to an example embodiment of the invention, the method includes sampling symbol data from one sample per symbol to N samples per symbol, wherein sampling includes: convolving the symbol data with a decimated finite impulse response (FIR) aperture impulse response coefficient set, convolving the symbol data with one or more shifted decimated FIR aperture impulse response coefficient sets, and summing the convolution results to produce interpolated bandlimited data.

Abstract: Certain embodiments of the invention may include systems and methods for implementing a multirate digital interpolating filter. According to an example embodiment of the invention, the method includes sampling symbol data from one sample per symbol to N samples per symbol, wherein sampling includes: convolving the symbol data with a decimated finite impulse response (FIR) aperture impulse response coefficient set, convolving the symbol data with one or more shifted decimated FIR aperture impulse response coefficient sets, and summing the convolution results to produce interpolated bandlimited data.

Abstract: Certain embodiments of the invention may include systems and methods for implementing a multirate digital decimating filter for filtering received symbol data. The method may include sampling the received symbol data at a selected sample rate, pre-averaging the sampled received data to provide two samples per symbol; convolving the pre-averaged samples with decimated finite impulse response (FIR) aperture impulse response coefficients to produce detected 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.

Abstract: A sampling method, denoted continuously variable IF sampling (CVIFS), implemented in digital transmission and reception components is characterized by sampling a bandpass signal which is centered at an intermediate frequency f.sub.IF that is related to both the data transmission symbol rate (R.sub.s) and sample rate (NR.sub.s) by integer ratios. Moreover, the CVIFS method is characterized in that the sample rate NR.sub.s is constrained to be four times the IF center frequency, and both the sample rate NR.sub.s and the IF center frequency are constrained to be within a range of a factor of 1.5 of their maximum values. To maintain this high sample rate as the data symbol rate is lowered, a "gear shifting" technique is utilized whereby the integer number of samples-per-symbol, N, is increased as the symbol rate decreases. Moreover, the sample rate NR.sub.s is always between 3.0 to 4.5 times the maximum data symbol rate (R.sub.smax), and the IF center frequency is always between 3/4 to 9/8 times (R.sub.