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Abstract

In a signal analysing and synthesizing filter bank system, the analysing bank receives a signal sampled at the rate f.sub.e and produces N contiguous subbank signals sampled at the rate f.sub.e /N. From the subband signals the synthesizing bank must recover the incoming signal. These filter banks are formed by modulation of a prototype filter by sinusoidal signals which, for subband k (O.ltoreq.k.ltoreq.N=1), have a frequency (2k30 1)f.sub.e /(4N) and respective phases +(2k+1).pi./4 and -(2k+1).pi./4 for the analysing and synthesizing banks. These signals are furthermore delayed by a time delay (N.sub.c -1)/2f.sub.e), where N.sub.c is the number of coefficients of the prototype filter. Preferably, the analysing bank is realized by the cascade arrangement of an N-branch polyphase network (12) and a double-odd discrete cosine transform calculating arrangement (14) and the synthesizing bank is realized by the cascade arrangement of a double-odd discrete cosine transform calculating arrangement (15) and an N-branch polyphase network (17).

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