| 摘要 |
PURPOSE:To stabilize the operation of the titled circuit by controlling a PLL circuit for dividing reference oscillation frequency, and 2nd local oscillation frequency and demodulating sounds by a CPU circuit. CONSTITUTION:The 1st local oscillation frequency to be injected to the 1st mixer is supplied from the PLL circuit 7 and the reference frequency of the circuit 7 is obtained by dividing oscillation frequency from a reference frequency oscillator 9 by a marker circuit 8. The circuit 8 is connected to an antenna through a switch 10 and a CPU11 opens/closes the switch 10 to actuate the circuit 8 during automatic adjustment. The 2nd local oscillation frequency to be applied to the 2nd mixer 3 is supplied to the 2nd local oscillator 12 consisting of a voltage control oscillator and finely adjusted by voltage from the CPU11 through a D/A circuit 13. Carrier oscillation frequency to a demodulator 6 is supplied from a carrier oscillator 14 and the output of the demodulator 6 is inputted to the CPU11 through a waveform shaping circuit 15.
|
