On acoustic-echo cancellation implementation with multiple cascadable adaptive FIR filter chips

The implementation of an acoustic-echo canceler for a speakerphone using multiple cascadable adaptive FIR (finite impulse response) filter ICs (the DSP 56200) is described. Ideally, canceling acoustic echoes requires a delay line that provides a delay equal to the impulse response time of the echo. It is shown that it is feasible to use the 24-bit-coefficient precision of the DSP56200 to reduce the length of the delay line. Simulation results show that with only 256 taps an echo return loss enhancement (ERLE) greater than 10 dB can be achieved on an echo 1000 samples in length