| 摘要 |
PURPOSE:To quicken the line restoration by extracting a prescribed frequency difference component from an orthogonal detection section in the entrance to the pseudo lead-in state, multiplying it and adding an identification signal being the result to a carrier regenerating section thereby allowing the normal lead-in state in a short time. CONSTITUTION:When a PLL is in the pseudo lead-in state, a fCK/4 component having a phase difference of 90 deg. is sent from an orthogonal detection section 1, it is squared by square circuits 41, 42, the polarity of Qch side is inverted by a polarity inversion circuit 51, then the DC voltage is made coincident with the Ich side by a DC voltage shift circuit 52 and multiplied to extract a repetitive signal of fCK/2. It is converted into a digital signal by an A/D converter 54, the repetitive signal inputted within a prescribed time is counted by a pulse counter 55, it is discriminated to the pseudo lead-in and a sweep oscillator 6 is driven, the output of the oscillator 6 is fed to a VCO 22 through an adder 7. Thus, the oscillation frequency of the VCO 22 is swept, and since the PLL escapes from the pseudo lead-in state and enters the normal state, then the fCK/4 component is lost and the sweep output of the oscillator 6 is lost. |
