Patent ID: 6442216
Filing Date: 2002-08-27
Classification: H03D,H04L

Abstract:
A digital demodulator which receives an input signal transmitted at a plurality of modulation deviation frequencies, comprising:a digital differentiate and cross-multiply discriminator which receives the input signal and which produces a digitized signal digitized at a sampling frequency, the digitized signal representing the plurality of modulation deviation frequencies; and a post detection filter responsive to the digitized signal, the post detection filter including a boxcar filter for filtering the digitized signal and producing a filtered digitized signal, a down sampler coupled to the boxcar filter for decimating the filtered digitized signal to produce a decimated signal, and a fixed-length boxcar filter which suppresses frequencies at multiples of a sampling frequency used to generate the decimated signal and produces a filtered output signal when the sampling frequency used to generate the decimated signal is a multiple of the plurality of modulation deviation frequencies.