COMPENSATING FOR NON-LINEAR EFFECTS IN SIGNAL PROCESSING WITH ACTIVE DEVICES

摘要

In signal processing circuitry using active devices, non-linearity of the device causes distortion of pure tones and the generation of intermodulation products for more complex signals. The transfer characteristics of such active devices (10) may be considered as the accumulated characteristics of input and output filter stages (12, 16) separated by a non-linear region (14). To compensate for non-linearities and reduce intermodulation products, a drive circuit (18) comprises pre- and post-correction filters (26, 28) separated by a compensating amplifier (20). The frequency response of the pre-correction filter (26) corresponds to that of the input filter stage (12) but is reversed in the frequency spectrum; with conventional I.F. the transfer characteristic of the amplifier (20) and frequency response characteristic of the post-correction filter (28) are the respective complements of those of the non-linear region (14) and pre-correction filter (26). The circuitry may be extended to compensate for active devices having more than one non-linear region and has particular application to klystron amplifiers used in broadcast television transmitters.