6.4 The FM input to a PLL demodulator has an unmodulated center frequency of 10.7MHz. (a) To what frequency must the VCO be set? (b) From which circuit is the recovered modulating signal taken?
a). PLL demodulator has a mixer, a VCO (voltage controlled oscillator) and a low pass filter as shown in the figure below.
VCO frequency should be same as input carrier frequency 10.7MHz
b). As shown in the figure above the output (demodulated FM signal) is taken from the filter circuit. Here the filter is a low pass filter that removes all the high frequency component from its input signal.
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