Compensating for non-linear effects in signal processing with active devices

摘要

PCT No. PCT/GB93/01106 Sec. 371 Date Dec. 16, 1994 Sec. 102(e) Date Dec. 16, 1994 PCT Filed May 27, 1993 PCT Pub. No. WO93/26086 PCT Pub. Date Dec. 23, 1993In 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 may be considered as the accumulated characteristics of input and output filter stages separated by a non-linear region. To compensate for non-linearities and reduce intermodulation products, a drive circuit comprises pre- and post-correction filters separated by a compensating amplifier. The frequency response of the pre-correction filter corresponds to that of the input filter stage but is reversed in the frequency spectrum; with conventional I.F. the transfer characteristic of the amplifier and frequency response characteristic of the post-correction filter are the respective complements, of those of the non-linear region and pre-correction filter. 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.