US 4,777,612 AGranted

Digital signal processing apparatus having a digital filter

AssigneeNEC Corporation

InventorYasuharu Tomimitsu

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Abstract

A digital signal processing apparatus with a rate-conversion function has at least two digital filters and a memory. A digital signal stored in the memory is selectively transferred to the at least two digital filters. These digital filters perform a filtering operation in parallel, and the results from each of the digital filters are alternately derived by a multiplexer. Thus, high-speed filtering can be executed. The memory temporarily stores a time-division-multiplexed signal which is sequentially read out of the memory and selectively transferred to the digital filters. Thus, a plurality of digital signals can be filtered by the same digital filters without an increase in hardware elements. Therefore, the digital filter section can be integrated in a single semiconductor chip. A shift register may be used as the memory, whereby a circuit arrangement of the digital filter section can be extremely simplified.

Claims8

Dependent claims

A digital signal processing apparatus processing a first digital signal of a first channel and a second digital signal of a second channel which are applied thereto in a time-division manner comprising:

an even-order digital filter;
an odd-order digital filer;
first means for receiving the first digital signal at a first timing;
second means for receiving the second digital signal at a second timing subsequent to said first timing;
third means coupled to said even-order digital filter and said first means for entering the first digital signal into said even-order digital signal at the second timing, said even-order digital filter performing a first filter operation on said first digital signal at the second timing;
fourth means coupled to said even-order digital filter and said second means for entering the second digital signal into said even-order digital filter at a third timing subsequent to said second timing, said even-order digital filter performing a second filter operation on said second digital signal at the third timing;
fifth means coupled to said odd-order digital filter and said first means for entering the first digital signal into said odd-order digital filter at said third timing, said odd-order digital filter performing a third filter operation on said first digital signal at the third timing;
and
output means coupled to said even-order digital filter and said odd-order digital filter for outputting a result of the first filter operation from said even-order digital filter at the third timing, outputting a result of the third filter operation from said odd-order digital filter in a first period of a fourth timing subsequent to said third timing, and outputting a result of the second filter operation from said even-order digital filter in a second period subsequent to said first period of said fourth timing.

6 more elements

Dependencies are inferred from the claim text.