Digital filter bank
First Claim
1. A digital filter bank of the type including a discrete transform means connected to a polyphase network comprising at least one complementary pair of first and second digital filters, characterized in that each of said filters comprises:
- a single input which provides a filter input signal during the course of a present sampling period;
at least a first output which during the present sampling period gives a first output signal value independent of the present sampling period filter input singal and dependent on the filter input signal of a previous sample period;
a second output which during the present sampling period gives an output signal value dependent in general on the value of the present filter input signal anda shift register which for the present sampling period receives a register input signal dependent on the present filter input signal, said shift register including a first set of stages comprising a first stage and every other one of a plurality of successive stages and including a second set of stages comprising a second stage and every other one of said plurality of successive stages, said first filter output being accumulated from weighted values of said first set of stages and said second filter output being accumulated from the weighted value of said register input signal and weighted values of said second set of stages.
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Abstract
A digital filter bank (10) which has a discrete cosine transform section (12) and a polyphase network section (14) has the polyphase network section configured with a plurality of single input-double output digital filters (16). The filters have one of their outputs (36) independent of their present input signal. This permits a single multiplier-accumulator to use a "memory swapping" procedure to accumulate all the requisite information from a complementary pair of the filters and to perform the necessary operations on it to compute an output value, while clearing the accumulator only once each sampling period.
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Citations
5 Claims
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1. A digital filter bank of the type including a discrete transform means connected to a polyphase network comprising at least one complementary pair of first and second digital filters, characterized in that each of said filters comprises:
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a single input which provides a filter input signal during the course of a present sampling period; at least a first output which during the present sampling period gives a first output signal value independent of the present sampling period filter input singal and dependent on the filter input signal of a previous sample period; a second output which during the present sampling period gives an output signal value dependent in general on the value of the present filter input signal and a shift register which for the present sampling period receives a register input signal dependent on the present filter input signal, said shift register including a first set of stages comprising a first stage and every other one of a plurality of successive stages and including a second set of stages comprising a second stage and every other one of said plurality of successive stages, said first filter output being accumulated from weighted values of said first set of stages and said second filter output being accumulated from the weighted value of said register input signal and weighted values of said second set of stages. - View Dependent Claims (2, 3, 4, 5)
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Specification