An N.sup.th order infinite impulse response digital filter for long-delay filtering of signals representing a digital input sequence. The N.sup.th order infinite impulse response digital filter is synthesized by cascading in series N first order infinite impulse response filter stages. A filter stage...http://www.google.com.hk/patents/US5999955?utm_source=gb-gplus-share專利 US5999955 - Delay generation filter
