US 2002/0159515 A1 · Noncyclic digital filter and radio reception apparatus comprising the filter

Abstract

In a nonrecursive digital filter, the number of times each bit of input data passes through a shift register is reduced to save power. Despreading data is sent to a first shift register 21 and a second shift register 22 each having a number of stages obtained by dividing the usual number of stages by two, and both shift registers alternately perform a shift operation at both edges of a shift clock CK. Multiplexers MP11 to MP14 are provided for selecting the odd-numbered codes of reference codes stored in a reference-code register 23 when the shift clock CK is in an OFF state and for selecting the even-numbered codes when the shift clock CK is in an ON state, and multiplexers MP21 to MP24 are provided for performing the selections analogous to the above. The exclusive-OR output of the output of each stage of the first shift register 21 and the outputs of the multiplexers MP11 to MP14, and the exclusive-OR output of the output of each stage of the second shift register 22 and the outputs of the multiplexers MP21 to MP24 are added by the adder 25 to obtain a correlation-strength output.

Claims6

Dependent claims

A nonrecursive digital filter which has an n-stage shift register for sequentially shifting input data having a predetermined number n of bits and in which the output of each output stage of the shift register is multiplied by a filter coefficient and added, characterized in that the n-stage shift register is divided into a plurality of shift registers, and each divided shift register is time-divisionally driven in synchronization with the input data.

A nonrecursive digital filter which has an n-stage shift register for sequentially shifting input data having a predetermined number n of bits and in which the output of each output stage of the shift register is multiplied by a filter coefficient and added, characterized in that the n-stage shift register is divided into first and second shift registers each having n/2 stages, and one of the first and second shift registers performs a shift operation at a rising edge of a shift clock and the other performs a shift operation at a falling edge of the shift clock.

first and second shift registers to which a spreading-code sequence is input and a shift clock is inputted, each having n/2 stages obtained by dividing the n-stage shift register;
a reference-code register for storing n reference codes;
first and second selection means for selecting and outputting the odd-numbered stages and even-numbered stages of the reference-code register according to the shift clock;
first multiplication means for multiplying the output of each stage of the first shift register by the output of the first selection means;
second multiplication means for multiplying the output of each stage of the second shift register by the output of the second selection means;
and correlation-strength calculation means for adding the multiplication results of the first multiplication means and the second multiplication means to output a correlation strength;
and characterized in that the first and second shift registers are configured such that either one of them performs a shift operation at a rising edge of the shift clock and the other performs a shift operation at a falling edge of the shift clock;
and the first and second selection means is configured such that, when the shift clock is in an ON state, either one of them outputs the even-numbered stages of the reference-code register to the first multiplication means and the other outputs the odd-numbered stages to the second multiplication means, and when the shift clock is in an OFF state, the either one of them outputs the odd-numbered stages of the reference-code register to the first multiplication means and the other outputs the even-numbered stages to the second multiplication means

5 more elements

Dependencies are inferred from the claim text.

Noncyclic digital filter and radio reception apparatus comprising the filter

Life of this patent

Noncyclic digital filter and radio reception apparatus comprising the filter

Life of this patent

Abstract

Claims6