Patent ID: 7483498

Claim:
Apparatus for frequency content separating an input signal, said apparatus comprising: a series of frequency separating stages with said input signal connected to an input of a first stage and an output of each of said stages, except for the last of said stages, connected to an input of a following stage and the output of the final stage providing said frequency content separated input signal, each frequency separating stage including at least one complex frequency shifting converter operable to receive a complex input signal representing an input bandwidth extending from −Fs/2 to +Fs/2 and to output a first frequency shifted complex output signal representing an upper portion of said input bandwidth and a second frequency shifted complex output signal representing a lower portion of said input bandwidth, wherein at least one complex frequency shifting converter, in at least one of said plurality of frequency separating stages, is configured to act as a tuneable complex frequency shifting converter having a frequency shifting characteristic for outputting a frequency shifted complex output signal representing a portion of said input bandwidth centred other than at −Fs/4 or +Fs/4.