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Reciprocal Digital Filter

IP.com Disclosure Number: IPCOM000091305D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 32K

IBM

Related People

Freeman, DG: AUTHOR [+2]

Abstract

A transfer function and its inverse can be implemented by time-sharing a digital filter by switch control. By way of example the recursive filter transfer function H(s) = (s/2/+As+C/2/)/(s/2/+Bs+C/2/) is illustrated.

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Reciprocal Digital Filter

A transfer function and its inverse can be implemented by time-sharing a digital filter by switch control. By way of example the recursive filter transfer function H(s) = (s/2/+As+C/2/)/(s/2/+Bs+C/2/) is illustrated.

For digital filter design and techniques, reference is made to an article in the February 1967, Proceedings of the IEEE, Vol. 55, No. 2, page 149, entitled "Digital Filter Design Techniques in the Frequency Domain" by Rader and Gold. As explained in such article, the above equation has the z transform of H(z/-1/) = (a+bz/-1/+cz/-2/)/(1+dz/-1/+ez/-2/) which is shown implemented when all switches are in the 1 position. The elements consist of multipliers with multiplicand values of a, b, c, d, and e, delay lines with delay times of unit time and twice unit time, and adders.

The z transform of the inverse of the first equation is given by H(z/-1/)/-1/ = (1+dz/-1/+ez/-2/)/(a+bz/-1/+cz/-2/). This function is shown implemented when all the switches are in position 2. Thus, by varying the position of all the switches in the digital filter shown, a transfer function or its inverse transfer function is realized.

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