Selftuning rejection filter for distorsion measurement
D. Costin, P. Opris · 2002
The paper presents a selftuning rejection filter working in a frequency range around 1 kHz. The circuit automatically rejects the fundamental frequency of the input signal and passes the remaining frequency components on to the metering circuit for measuring distorsion. The circuit described below was used as the main block in the design of a distorsion meter for radiotelephone's audio characteristics measurements.