Automatic frequency control circuit.

摘要

An automatic frequency control circuit mounted on a mobile station in mobile communication. The automatic frequency control circuit performs feedback control of an oscillation frequency of a local oscillator used in conversion of a reception frequency to an intermediate frequency signal in response to the count result of the frequency of the intermediate frequency signal. If a receiver is not in the hand-off state, counting is performed for comparatively long time; if in the hand-off state, counting is performed for comparatively short time conforming to required stabilization performance at hand off. Occurrence of variations in count values caused by fading is detected, and only the count values worthy of trust are used as a base of control. A level drop caused by fading is compensated by self-oscillation.