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Digital Filter

IP.com Disclosure Number: IPCOM000082816D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Related People

Tubiana, M: AUTHOR

Abstract

Shown is a digital filter, wherein the products of the coefficients of the filter with all potential values of the input samples are stored in different areas of a read-only memory. When compared to conventional designs, addressing of the memory is simplified as well as the summing of products to obtain the output filtered sample.

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Digital Filter

Shown is a digital filter, wherein the products of the coefficients of the filter with all potential values of the input samples are stored in different areas of a read-only memory. When compared to conventional designs, addressing of the memory is simplified as well as the summing of products to obtain the output filtered sample.

In a digital transversal filter, output samples y(i) are given by the expression;

(Image Omitted)

where x(i-k) is the sample value of the input signal at time (i-k).

The number of coefficients a is limited and is chosen equal to 5 in the practical implementation shown in the figure. Thus, the products which are required to obtain one output sample y are; a(o) x(i) , a(1) x(i-1) , a(2) x(i-2) , a(3) x(i-3) , a(4) x(i-4).

The represented filter allows these products to be generated and summed during a sampling period of the input signal by compressing the input samples applied to input X(in) of a conventional compression circuit that operates at a frequency Fc, which is six times the sampling frequency Fs when five coefficients are used.

A read-only memory, ROM, is arranged in five areas 1 to 5 containing the products of coefficients ao to a5 with all potential sample values, as indicated on the figure. This memory is addressed through a storage access register SAR which comprises two parts: one for addressing a specific area 1 to 5 and the other for addressing a selected position in the area.

Input samples X(in) are received at the input of the compression circuit which comprises a shift registe...