Architecture of a single chip acoustic echo and noise canceller using cross spectral estimation

This paper describes the architecture of a single chip acoustic echo canceller and noise filter for full duplex hands free communications. To our knowledge the CENS90200 is the first ASIC to eliminate the acoustic echo by using cross spectral estimation. This approach is much more robust against the environmental noise typically found in a hands free (e.g. automotive) environment than the usually employed class of "normalized least mean square" (NLMS) algorithms. Additionally a noise filter reduces the background noise by using spectral minimal statistics and diffusive gain factors. These advanced algorithms have substantially greater computational performance requirements than their traditional counterparts. A highly portable architecture is presented that meets these requirements at low clock to sample frequency ratios. It combines directly hardware mapped algorithms and a purpose built processor optimized for spectral signal processing, thus making a low cost, single chip implementation possible.