| 摘要 |
A subsampling filter for subsampling a filter input sequence of oversampled data at a predetermined subsampling ratio into a filter output sequence of eventually subsampling data, has a data holding unit for producing three successive data of the oversampled data as each of output patterns of a first output sequence. An input-stage filter subsamples the first output sequence at a subsampling ratio of one by two into a second output sequence of intermediately subsampled data. An output-stage filter subsamples the second output sequence into the filter output sequence. Each of the intermediately subsampled data has one of five values 0, plus 1, minus 1, plus 2, and minus 2. The output-stage filter includes a memory for memorizing filter coefficients determined by a transfer function of this filter, a scaler for calculating products of the filter coefficients and the intermediately subsampled data, and an adder for calculating an algebraic sum of each product and an intermediate sum which is an accumulated sum fed back from a register device of the output-stage filter for memorizing the algebraic sum as such an accumulated sum.
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