Patent ID: 8451029

Claim:
A frequency synthesizer comprising: a reference signal generation circuit which generates a reference signal, the reference signal output from the reference signal generation circuit being compared with an output signal from a voltage controlled oscillator to perform control so that the output signal of the voltage controlled oscillator has a desirable frequency, wherein the reference signal generation circuit includes: a first oscillator having such characteristics that a frequency thereof stabilizes shortly after power activation; a second oscillator having such characteristics that a frequency thereof is more unstable than that of the first oscillator immediately after the power activation and that the stability of the frequency thereof is higher than that of the first oscillator after the elapse of a fixed time; a first weight converter which regulates the weight of an output from the first oscillator; a second weight converter which regulates the weight of an output from the second oscillator; an adder which adds up outputs from the first and second weight converters to output the added output as the reference signal; and a control unit which controls a first weight of the first weight converter and a second weight of the second weight converter to output the values of the weights to the first and second weight converters so that the first weight is set to be higher than the second weight and the second weight is set to be lower than the first weight immediately after the power activation, so that the first weight lowers and the second weight rises gradually with the elapse of time, and so that the first weight is set to be 0% and the second weight is set to be 100% after the elapse of a fixed time.