Patent ID: 6990060

Claim:
A system that demultiplexes an RF signal including at least two nested sets of frequency division multiplexed (FDM) channels extending over a bandwidth B, the system comprising: a baseband converter that converts the RF signal to a baseband signal wherein a center frequency of said baseband signal is offset from DC by an amount equal to an integer multiple of the channel spacing of a widest of the nested FDM channels; an analog to digital converter (ADC) that converts said baseband signal to a digital signal at a sampling rate equal to four times said offset; a complex baseband digital signal generator, coupled to said analog to digital converter, that performs a half-band complex bandshift of said digital signal and that filters said half-band complex bandshifted signal with a two to one decimating, symmetric, half-band finite impulse response (FIR) filter to generate a complex baseband digital signal; a k stage sub-band definition network, coupled to said complex baseband digital signal generator, that divides said complex baseband digital signal into k sets of sub-band output signals by sub-band definition filters, wherein each stage of said k stage sub-band definition network comprises a plurality of parallel polyphase-discrete Fourier transform (PPF-DFT) filter banks, wherein said PPF-DFT filter banks, where appropriate to align sub-band signals with filter pass-bands of said PPF-DFT filter banks, are preceded by at least one of: a quarter-band bandshift, and a sixth-band complex bandshift, and are followed by an eighth-band complex bandshift; and sub-band demultiplexers, coupled to said k sets of sub-band output signals of said k stage sub-band definition network, that demultiplex each of said sub-band output signals to obtain k sets of demultiplexed sub-band channel signals.