| 摘要 |
PURPOSE:To use an AFC circuit for the mobile radio system repeating transmission/reception in a short time by correcting a frequency shift even in a bit synchronism period so as to active the AFC circuit without hindrance even in the bit synchronism period. CONSTITUTION:A signal having a phase angle rotated from the 1st expression to the 4th expression is inputted to a signal input terminal 1 of the AFC circuit, and a positive pulse is outputted from a multiplication circuit 12 when an output of exclusive circuits 9, 10 is logical 1 and a negative pulse is outputted when logical 0. The output side of positive/negative pulse detection circuits 15, 16 detecting the output of the circuit 12 is provided with time interval detection circuits 41, 42 and the detecting time of the circuits 41, 42 is set by a time setting circuit 44. The circuit 44 receives the information from a radio wave reception information input terminal 45, a time taup longer than the time tau corresponding to 1-bit for a prescribed time is set to the circuits 41, 42 and then the time tau is set. Then the circuits 15, 16 detects the synchronism shift even for the period of bit synchronism, a VCO13 is controlled and the AFC circuit is activated with high accuracy. |
