| 摘要 |
PURPOSE:To delete a phase changing part of a four-phase DPSK wave and to generate always a satisfactory demodulating signal by providing plural double balance type detecting devices, a subtraction circuit, a loop filter, etc., and four-multiplying the signal of the base band. CONSTITUTION:A four-phase DPSK wave supplied to an input terminal 1 is supplied through phase detecting devices 2 and 3 for synchronizing and detecting, low-pass filters 4 and 5, etc., to an exclusive OR circuit, and outputted to output terminals 19 and 20 as a demodulating signal. The output signal of the detecting devices 2 and 3 is inputted to double balance type detecting devices 11, 12 15 and 16, subtraction circuits 13, 14, 17, etc., and a phase detecting characteristic is four-multiplied and converted. Thus, the changing part of the phase in the four phase DPSK wave is vanished, only an error component in the making- a-round loop is supplied through a loop filter 18 to a voltage control oscillator 7 and the carrier equal to the carrier before modulating from the oscillator 7 is outputted from the oscillator 7. Consequently, the correct synchronizing and detecting are executed at the detecting devices 2 and 3 and the satisfactory demodulating signal can be always generated. |
