Microphone signal processor

EE 112 July/August 1986 192microphone-signal processor D1 In broadcasting systems, intercoms, and mobile radio telephones it is necessary to amplify the microphone signal over a restricted range only. This may be achieved with the aid of a compressor or a clipper. The for- mer provides low distortion, but its design is rather complex, whereas a clipper is of simple construction, but suffers from appreciable harmonic and intermodulation distortion. Of these two, intermodulation distortion is far and away the most troublesome; in fact, the acceptability of a clipper in an audio signal processor would be far greater if clipping would not cause such severe intermodulation distortion. In the accompanying diagram, inter- modulation distortion is reduced by signal-control of the cross-over point. The principle of operation is shown in Fig. 1. The amplifier has a very high impedance input (value of RI). When the signal level is so low that the diodes do not conduct, the cross- over point ...