NEIGHBORING-CHANNEL SUPPRESSING METHOD IN RECEPTION OF FREQUENCY-MODULATED SIGNAL

摘要

PURPOSE: To securely separate an effective signal and a fault signal from an adjacent channel without depending upon the state quantity of a demodulator. CONSTITUTION: The fault signal and effective signal are filtered by different ZF filters 28 and 26 which are tuned to respective frequency characteristics. The fault signal is led to a digital PLL switching circuit 30 and an estimated signal simulated to the fault signal on the effective signal path 22 is obtained from ZF characteristics filed in a table in a memory 32 wherein the momentary frequency of a demodulated signal is addressed. At a coupling place 34, this simulated fault signal is subtracted from the effective signal affected by the fault and the effective signal after the fault is removed is led to a digital PLL switching circuit 36.