Patent ID: 6091704
Filing Date: 2000-07-18
Classification: H03H,H04J,H04L

Abstract:
A system that demultiplexes an RF signal comprised of N frequency division multiplexed channels extending over a bandwidth B, the system comprising:a baseband convertor that converts said RF signal to a baseband signal whose center frequency is offset from DC by an amount equal to three quarters of the bandwidth B;an analog to digital converter, coupled to said baseband convertor, that converts said baseband signal to a digital signal at a sampling rate three times the bandwidth B;a complex baseband digital signal generator, coupled to said analog to digital converter, that generates a complex baseband digital signal by a quarterband complex bandshift of said digital signal and that filters said quarterband complex bandshifted signal with a two to one decimating, symmetric, half-band finite impulse response filter;a k stage filter tree, coupled to said complex baseband digital signal generator, that divides said complex baseband digital signal into 2.sup.k sub-bands by sub-band definition filtering, wherein said k stage filter tree comprises one third band bandshifters and two to one decimating, symmetric, half-band finite impulse response filters; anda demultiplexer, coupled to the 2.sup.k outputs of the final stage of said k stage filter tree, that demultiplexes each of the 2.sup.k outputs with an N' channel polyphase-fast Fourier transform (FFT) filter bank, where N'=3N/2.sup.k+1.