| 摘要 |
<p>PURPOSE:To simplify the circuit constitution to miniaturize an IC by forming a phase lock loop circuit of a voltage controlled oscillator, a phase comparator, and a low-pass filter and providing a voltage source for the voltage controlled oscillator to demodulate a multimode signal. CONSTITUTION:The phase lock loop circuit is formed with a voltage controlled oscillator 18 whose oscillation frequency is controlled by a voltage control signal, a phase comparator 17 which compares phases of output and input signals of this oscillator 18 with each other, and a low pass filter 19 to which the output of this comparator 17 is inputted. A voltage source 20 is provided which supplies a prescribed voltage to the voltage controlled oscillator 18, and an FM signal is demodulated by the phase locked loop circuit, and switching control is so performed that the phase locked loop is released and a fixed voltage is given to the voltage controlled oscillator 18 by the voltage source 20, and an AM signal is demodulated. Thus, the circuit constitution for multimode demodulation is simplified to miniaturize the IC.</p> |
