CCDs for Speech Bandwidth Reduction.
Final rept. 18 Apr 77-31 Jan 79,
TEXAS INSTRUMENTS INC DALLAS CENTRAL RESEARCH LABS
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The need for security in voice communication is met by converting voice to digital form so that sophisticated digital encryption is possible. It is desirable that the digital voice signal be compatible with conventional 3-kHz analog voice transmission bands hence, the vocoder that converts analog voice signals to digital form must employ some form of bandwidth compression to yield data rates down to 2.4 kilobitssecond. Linear prediction techniques are commonly used to implement vocoders in essentially all-digital systems, but with current technology such systems are expensive, fairly large, and consume large amounts of power. This report concerns the application of CCD technology to the vocoder problem using a second, much older approach, the channel vocoder. The objective is to demonstrate the potential of analog CCD technology to achieve a low-cost, low-power vocoder system. Two custom-designed CCDNMOS integrated circuits are the key to this approach, and the design of these circuits is detailed in this report. Author
- Electrical and Electronic Equipment
- Military Intelligence
- Voice Communications