| 摘要 |
PROBLEM TO BE SOLVED: To provide a demodulator circuit adapted to expand a frequency pull-in range and prevent degradation in reception characteristic at the same time, without enlarging the circuit scale.SOLUTION: According to an embodiment, a demodulator circuit is installed in a communication device provided with a preprocessing unit for preprocessing a digitally modulated received signal, an analog/digital converter for converting the preprocessed received signal into digital quantity to generate a digital signal, and a loop filter for generating a control voltage for an oscillator which generates a clock signal. The demodulator circuit is provided with a conversion unit for converting a digital signal into a baseband signal, a detection unit, and a pulse width variable unit. The detection unit detects sign inversion of the baseband signal, and outputs, to the loop filter, a phase error information pulse indicating a phase error between a clock component extracted from the baseband signal on the basis of sign inversion timing and the clock signal. When carrier synchronization is not established yet, the pulse width variable unit changes the pulse width of the phase error information pulse to make it wider than the pulse width of the phase error information pulse after carrier synchronization is established. |
