FM DEMODULATOR WITH THRESHOLD EXTENSION AND RECEIVER COMPRISING SUCH AN FM DEMODULATOR

摘要

An FM demodulator having two input terminals (11, 12), to which FM input signals having 90 DEG phase relation are applied, the said FM demodulator including a phase comparator (1) and a tunable, phase shifting circuit (2), the phase shifting circuit (2) being tuned by the FM demodulator output signal via a feedback path comprising a loop, filter. By adding a compensation filter (5) to the tuning control loop the phase shifting circuit is effectively cancelled from the tuning control loop, thereby making the tuning control loop independent of the bandwidth of the phase shifting circuit (2). Thus the bandwidth of the phase shifting circuit (2) can be reduced for threshold extension.