Companding Digital Signal Processors

We discuss a technique whereby internal signals in a DSP can be controlled externally without causing output disturbances. This is used to extend the technique of companding (compressing and expanding), widely used in transmission and sound recording, to digital signal processors. It is shown that this technique allows all signals involved, including those at the input of an analog-to-digital converter and those internal to a fixed-point DSP, to be close to full scale, thus spanning most of the available bits and making possible a large signal-to-noise-plus-distortion ratio over a large input range