Abstract: 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 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.

Abstract: An amplifying arrangement includes a klystron in which an electron beam interacts with a high frequency signal to produce a modulated amplified signal. The high frequency signal is maintained at a substantially constant amplitude and modulation of the amplified signal is provided by controlling the electron beam current.

Abstract: Klystrons are inherently non-linear and have an amplification characteristic which is frequency dependent on both signal amplitude and beam current. This may be compensated for by applying suitable correcting signals to a beam controlling electrode of the klystron thereby changing its electron beam current over the whole excursion of a modulating signal. A klystron arrangement in accordance with the invention is particularly suitable for use in a television transmitter, enabling full time modulation to be carried out with a significant improvement in the operating efficiency of the klystron.