| 摘要 |
A frequency synthesizer includes a modulator (141), a voltage controlled oscillator (VCO) (108), a bandpass filter (BPF) (109), a reference oscillator (104), and a control circuit (142). The modulator (141) outputs a modulated signal on the basis of a modulation signal and a local-oscillation frequency signal. The VCO (108) outputs a local-oscillation frequency signal having a variable frequency to the modulator (141) in accordance with an internal control signal. The BPF (109) filters a predetermined harmonic wave of the frequency of the local-oscillation frequency signal output from the VCO (108). The reference oscillator (104) outputs a reference frequency signal (132). The control circuit (142) detects the phase difference between a signal based on the output from the BPF (109) and a signal based on the reference frequency signal (132) from the reference oscillator (104) and outputs an internal control signal (135) to the modulator in accordance with the detected phase difference. <IMAGE> |
