| 摘要 |
PURPOSE:To improve the accuracy of synchronous detection by imposing FM modulation on a pilot signal simultaneously with a service channel signal, extracting a control voltage signal to the voltage-controlled oscillator of the PLL circuit on a reception side through a necessary filter, and detecting the synchronous state from the detection output. CONSTITUTION:The pilot signal is FM-modulated and sent out simultaneously with the service channel signal SC. Here, the control voltage signal (output of loop filter 18) to the voltage-controlled oscillator 19 of the PLL circuit on the reception side is led out through the band-pass filter 23 and further the synchronous state is detected from the detection output from a detector 24. Consequently, the influence of a noise is reduced, the possibility of malfunction in bit error measuring operation is eliminated, and the accuracy of the synchronous detection is improved. |
