| 摘要 |
PURPOSE:To need no special pilot signal when a phase shift keying modulated wave is received, by impressing the output of an integrator to a voltage control oscillator in the form of a frequency error signal to keep the frequency at a fixed level for the output signal of a frequency converter. CONSTITUTION:The signal of a non-modulated part is extracted through a narrow BPF9 which transmits the frequencies of the non-modulated part. The signal converted into the DC voltage after the wave detection carried out by a wave detector 10 is compared with the threshold value through a voltage comparator 11 to obtain a pulse signal having a certain time width of the non- modulated part. while this pulse signal exists, the frequency information showing a frequency error of the output of a frequency discriminator 12 is integrated by a sample holding type integrator 13 to obtain the DC voltage proportional to the frequency error. This voltage undergoes the sample holding through the integrator 13 and is applied to a voltage control oscillator VCO14. Thus the frequency of the VCO14 is controlled so that the output of the integrator 13 is set at 0 to obtain the output signal of a fixed frequency for a frequency converter 8. |
