| 摘要 |
PURPOSE: To eliminate the effect of frequency fluctuation in a received modulation wave by using a phase detection means to detect a phase difference between a modulation wave and a reference continuous wave and providing a variable frequency oscillator of a frequency converter controlled based on the phase difference to the detection circuit. CONSTITUTION: A received modulation wave S(t) is given to a frequency converter 1. A local oscillation signal L0 (t) generated by a local oscillator 2 is given to the converter 1, from which a modulation wave Sif(t) with an intermediate frequency being a difference frequency between the modulation wave S(t) and the signal L0 (t) is outputted. The modulation wave is given to an orthogonal dielectric detector 4 via a BPF 3. A reference continuous wave L1 (t) is given to the detector 4 as a reference signal from the local oscillator 5 and when the frequency and the phase of the modulation wave Sif(t) and the continuous wave L1 (t) are coincident, a correct modulation signal is outputted. The in-phase component I and the orthogonal component Q of the orthogonal synchronization detection output from the detector 4 are given to a costus loop 6 and a phase difference output is given to the local oscillator 2 via the loop filter 7 to form a negative feedback loop for automatic frequency tracking control. |
