Browse Prior Art Database

IIR/FIR Digital Filter Technique

IP.com Disclosure Number: IPCOM000038318D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Coker, JD: AUTHOR [+3]

Abstract

This invention provides significantly enhanced processing capability in a digital filter. The user may, via external control, select either infinite-impulse-response (IIR) or finite-impulse-response (FIR) processing. The invention requires a very small size increase over a normal FIR-only implementation.

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IIR/FIR Digital Filter Technique

This invention provides significantly enhanced processing capability in a digital filter. The user may, via external control, select either infinite-impulse- response (IIR) or finite-impulse-response (FIR) processing. The invention requires a very small size increase over a normal FIR-only implementation.

The invention is described in the figure. The numbers ak and bk are tap weights (multipliers) and the z-1 function blocks are unit delays.

This technique is to interrupt the delay path of a FIR filter with a multiplexer (mux). (If the mux is placed anywhere but in the middle of the delay path, the numerator and denominator of the resulting IIR filter transfer function will be of different order.) If the "switch" is at position 1 (per the figure), only the x values propagate along the delay path and the bk values become numerator coefficients of z-n . This is a normal FIR filter. If the "switch" is at position 2, output values are injected into the delay path and the bk values become denominator coefficients of z-n . This is an IIR filter in a non-canonic topology.

The filter gains its advantages with a single mux, which is normally quite small when compared to the size of the rest of the filter. Data rate performance is affected slightly because the mux is in the speed path of the filter.

Disclosed anonymously.

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