METHODS AND APPARATUS FOR IMPROVED SUB-BAND ADAPTIVE FILTERING IN ECHO CANCELLATION SYSTEMS

摘要

In methods and apparatus for echo cancellation using sub-band adaptive filtering, the bandwidth of each of a number of sub-band analysis filters, as well as the bandwidth of each of a number of synthesis filters, is increased as compared to a corresponding bandwidth in a conventional system. More specifically, the -3dB bandwidths of adjacent filters in an analysis or synthesis filter bank according to the invention are designed to overlap one another. For example, each of M (an integer) sub-band filters in an analysis or synthesis filter bank according to the invention can include a -3dB bandwidth somewhat greater than 1/M times a total bandwidth of interest. The increase in bandwidth tends to cancel aliasing effects resulting from sub-band down-sampling, and an echo cancelling device according to the invention can therefore provide superior output signal reconstruction as compared to conventional devices.