Receiver with improved digital intermediate to base band demodulator

摘要

A digital IF to base band demodulator (120) includes delta sigma samplers (202, 204) for sampling two channels of an IF signal at a sampling rate that is substantially higher than the Nyquist rate for the IF signal. A first pair of decimation filters (206, 208) decimates and filters the output of the delta sigma samplers (202, 204) but keeps the samples at a rate sufficient to perform digital mixing, cross adding, and pulse shape match filtering. A set of mixers (210, 212, 214, 216) mixers the output of the first pair of decimation filters with two phases of a digital representation of an local IF signal. A pair of summers (222, 224) sums, and subtracts outputs of the set of mixers (210, 212, 214, 216) in order to cancel undesired harmonics. A second set of decimation filters (226, 228) decimates and filters the output of the summers (222, 224) applying a filter function that is matched to a pulse shape of a base band signal present in the IF signal.