Signal filter.

摘要

An analog baseband signal (32) modulates a reference frequency carrier signal (38) to provide a double sideband, suppressed-carrier DSB-SC signal. The DSC-SC signal is converted in a voltage-to-frequency converter (54) to a series of pulses, the repetition rate of which is proportional to the level of the DSB-SC signal. The output signal of the voltage-to-frequency converter is demodulated to produce a digitally formatted version (62) of the baseband signal. A notch filter to reflect an undesired signal is provided as a feedback path from the output voltage-to-frequency converter (54) to a negative input of a summer (48) in the input line of the DSB-SC signal. The feedback path converts the frequency signal from converter (54) to a cancellation signal having the format of the undesired signal.