| 摘要 |
PURPOSE:To always monitor a C/N(carrier-to-noise ratio) with simple constitution by measuring relation between the size of the phase difference of a PSK (phase shift keying) signal and its generating frequency, and deciding the C/N based on the relation. CONSTITUTION:A phase difference signal that is the phase difference between the phase of the PSK signal 1 and that of a VCO2 is detected at a phase comparing circuit 3, and a DC voltage equivalent to the long time means value of the phase difference signal is extracted by a loop filter 4, and the oscillation phase of the VCO2 is controlled by the DC voltage. And since the logic of a symbol is decided by the phase difference that is the output of the circuit 3, the detection of the C/N can be performed by inputting the output of the phase comparator 3 to a C/N detecting circuit 5. In such a way, it is possible to obtain a C/N detector to always detect the C/N of the PSK signal. |
