| 摘要 |
PURPOSE:To realize the AFC circuit (automatic frequency control circuit) whose sweep speed is constant and implementing stable pull--in operation while the sweep frequency range is unchanged. CONSTITUTION:A frequency difference discrimination circuit 8 is provided in the AFC circuit provided with a mixer 1, a phase comparator 6, a sweep oscillator 2, a loop filter 3 and a voltage controlled oscillator 2, and the frequency difference discrimination circuit 8 discriminates a difference between the frequency of a reference signal outputted from the sweep oscillator 4 and an output frequency of the mixer, the sweep oscillator is connected to the loop filter 3 at the outside of the AFC loop lock range and the phase comparator 6 is connected to the loop filter in the AFC loop lock range. |
