| 摘要 |
PURPOSE: To pull in a frequency in a short time without use of a sweeper with respect to the carrier recovery circuit used for a communication system where data transmission is conducted by demodulating a modulation wave subject to quadrature modulation. CONSTITUTION: An area discrimination device 50 discriminates whether or not a base band signal subjected to guadrature demodulation is in a specific area on a phase plane by a recovered carrier outputted from a voltage controlled oscillator 16. When the signal is present in the specific area, selectors 52, 54 are used to select an output of a phase comparator 26 and when the signal goes outside of the area, a preceding value is held. A direction of control indicated by the phase comparator 26 is set in a direction to suppress the rotation just before the base band signal rotated on a phase plane goes out of the area. |
