Compensation circuit for trailing edge distortion of pulse-width modulated signal

摘要

When a pulse-width series modulator is connected to the cathode of an RF radio transmitter tube for the purpose of series modulation, filtration of the PWM switching signal is required to eliminate the switching signal from the output modulating signal. Stray capacitive effects in this filtration generate undesirable distortion in the trailing edge of the signal appearing in the last stage of the PWM thereby producing non-linearity in the modulation of the RF output tube. The present disclosure illustrates circuitry for complimentarily modifying the leading edge of the pulses so as to maintain a linear relationship in the time integral of voltage in the output signal. This modification is accomplished through a plurality of capacitive units each having different time constants for charging and discharging.