Quadrature mirror filters with staggered-phase subsampling

Claim 1

A quadrature mirror filter bank in combination with a source of sampled-data input signal for separating said sampled-data input signal into first and second subband signals each sampled half as densely as said input signal, staggered in phasing respective to each other, and time-interleaved sample-by-sample in a quadrature mirror filter bank output signal, said quadrature mirror filter bank comprising: a delay line having an odd numbered plurality of regularly spaced taps consecutively ordinally numbered from -n th to +n th , where n is an integer greater than or equal to one, proceeding from the input end of the tapped delay line to its output end; the -n th tap of said tapped delay line being receptive of sampled-data input signal; means for summing the signals from each pair of taps having the same ordinal number except for sign, to generate a set of partial sum signals correspondingly ordinally numbered; means for weighting the signal from the 0 th tap of said delay line and each of said even-numbered partial sum signals by respective weights to generate a first set of weighted partial sum signals; means for summing together said first set of weighted partial sum signals to generate a first component of the quadrature mirror filter bank output signal; means for weighting each of said odd-numbered partial sum signals by respective weights, to generate a second set of weighted partial sum signals; means for summing together said second set of weighted partial sum signals to generate a second component of the quadrature mirror filter bank output signal; and means for combining samples of said first and second components of the quadrature mirror filter bank output signal appearing parallel in time, alternately additively combining and subtractively combining each successive pair of parallel-in-time samples, to generate said first and second subband signals respectively in said quadrature mirror filter bank output signal.