A robust channel vocoder for adverse environments

A channel vocoder has been developed to operate in environments of high acoustic noise and high bit error rates. The 2400 b/s vocoder incorporates a robust pitch extractor and regenerator, automatic speech level control and forward error correction. It is implemented almost entirely digitally by using an lntel 8085 microprocessor system and a special purpose digital filter bank. The vocoder is currently packaged in a 1/4 ATR case (short) which occupies a volume of approximately 250 cubic ins, and it will meet full military environmental conditions. The first section of this paper deals with basic channel vocoder operation. The next section covers the implementation in the digital filter bank and microprocessor. The paper concludes with a brief description of the equipment and its performance in adverse conditions.