| 摘要 |
PURPOSE:To shorten a pull-in time without deteriorating a stationary characteristic, by obtaining two outputs which cross orthogonally to each other by converting an input signal to another frequency by using the output of a voltage controlled oscillator, and performing the detection of a frequency error at either or both the leading edge and the trailing edge of the signals. CONSTITUTION:Two orthogonal output signals S and C can be obtained by frequency conversion circuits 41 and 44, the voltage controlled oscillator 42, and a fixed oscillator 43. The signals S and C are changed to the signals DS and DC via an LPF, and an A/D converter. An edge detection circuit 49 outputs detection signals RC and FC at the leading edge and the trailing edge of the signal DC. As for a frequency error detection circuit 410, for example, a D-FF is used as an identification device, and the DS is inputted to the D input of the D-FF, and the signal RC or the signal FC is inputted to the clock input. In such a way, it is possible to detect the polarity of the frequency error. In such a case, the amplitude of the DS before digital conversion at the leading and the trailing edges of the DC are equal, no deterioration in the error characteristic is generated in the detection of the frequency error. Also, it is possible to double an operating clock frequency for error detection in said circuit compared with the operating clock frequency in a conventional circuit. |
