FREQUENCY SYNTHESIZER AND RADIO COMMUNICATION DEVICE

摘要

Loop filters (108-1 to 108-N) respectively have noise peak frequencies omegan set so as to correspond to the CN ratio requested by a plurality of radio communication methods. A control section (102) switches to a loop filter corresponding to the radio communication method analyzed to be currently in communication by a mode analysis section (101). The loop filters are used to filter the control voltage in accordance with a phase difference between a reference signal output from a reference signal generator (103) and a signal output from a voltage control oscillator (109). The control voltage after subjected to the filtering controls the oscillation condition of the voltage control oscillator (109). Thus, when a different CN ratio is requested for each of the reception signals, it is possible to provide a small-size frequency synthesizer and a radio communication device corresponding to each of the reception signals.