Active high-power bandpass filter

摘要

An active power-line filter which provides bandpass filtering and transient suppression. The high-power signal to be filtered is modulated to form a chopped waveform within an envelope defined by the input waveform and the modulation is removed by passing the chopped signal through a low-pass filter. The output of the low-pass filter is then compared in a differential amplifier with a low-power reference signal which is phase-locked to the primary component of the high-power signal. The output of the differential amplifier is phase-compensated for the effects of the low-pass filter and is compared to the reference in a phase-detection multiplier to produce an error signal to adjust the duty cycle of the chopped waveform so that the waveform at the output of the low-pass filter is identical to the reference waveform. For periods when the high-power signal is out of phase with its primary component, the polarity of the high-powered signal is reversed at the input of the active filter to allow the filter to compensate for this situation.