ANALOG MULTIPLIERLESS LMS ADAPTIVE FIR FILTER STRUCTURES

Two adaptive FIR filter configurations are proposed for implementing t he LMS algorithm with no along delay elements or multipliers. The firs t uses a linear feedback shift register (LFSR) to generate pseudorando m binary sequences for applications where white noise has been traditi onally used. The binary signals are delayed by a shift register and mu ltiplied by on/off switching so that the resulting structure is free o f analog delay lines and multipliers. For applications where inputs ar e colored, the second configuration uses a Sigma-Delta modulator as fr ont-end for converting the adaptive filter's input into a binary seque nce. Such a filter tends to adapt itself into a low-pass characteristi c to remove the high frequency noise due to the modulator.