| 摘要 |
PURPOSE:To obtain an AFC system requiring no special pilot signal, by converting the frequency of a PSK modulated wave with an output signal of a VCO, detecting a frequency error signal by a frequency discriminator after extracting the nonmodulated part of the frequency converted signal through a BPF, applying the extracted frequency error signal to a peak value holding integrator to hold the peak value and then applying the peak value to the frequency control terminal of the VCO to set the frequency of the output signal of a frequency converter at a fixed level. CONSTITUTION:A received PSK modulated wave is mixed with the output signal of a VCO12 by a frequency converter 8 to perform a frequency conversion. The frequency converted signal extracts the signal of a nonmodulated part of a figure A by a BPF9. When the signal of a nonmodulated part of a figure B is passed through a frequency discriminator 10, the voltage shown by (C) or (D) is delivered. The peak value of the voltage is held at a peak value holding integrator 11 to obtain the voltage shown by (E) or (E'). This voltage is applied to a frequency control terminal of the VCO12, and the frequency of the VCO12 is controlled to set the output voltage of the integrator 11 at 0. The error frequency component of a PSK modulated wave is corrected by the output frequency of the VCO12. Thus the frequency of the output signal of the converter 8 is set at a fixed level and undergoes AFC. |
