| 摘要 |
PURPOSE:To improve the C/N by giving a forced change from outside to the oscillation frequency for the variable oscillator of the local oscillator and then carrying out the fine adjustment through detection of the unlocked state of the loop. CONSTITUTION:In the superheterodyne receiver adopting (PLL) for the local oscillation circuit, the variable capacitor to vary the oscillation frequency of the voltage control variable frequency oscillator 6 and the mu tuner are interlocked to the input antenna coil and others of high frequency amplification part 1. And clock oscillator 13 gives the code to decide the oscillation frequency to counter 12 which controls the division ratio of programable divider 11 controlling the oscillation frequency of oscillator 6. The presence or absence of the oscillation output of oscillator 13 is controlled by switching circuit 14. And circuit 14 is actuated by the unlock signal within the PLL. |
