| 摘要 |
A frequency synthesizer using two phase locked loops is provided to obtain a low phase noise characteristic with a narrow channel space by using an integer-N phase locked loop and a fractional-N phase locked loop. A frequency synthesizer using two phase locked loops includes a reference frequency oscillator(20), an integer-N phase locked loop(30), a fractional-N phase locked loop(40), and a frequency adder(50). A signal having a reference frequency is outputted from the reference frequency oscillator, and is inputted to the integer-N phase locked loop for outputting a signal having a first output frequency and the fractional-N phase locked loop for outputting a signal having a second output frequency. The signal having the first output frequency and the signal having the second output frequency are inputted to the frequency adder, and the frequency adder outputs a signal having a frequency corresponding to a sum of the first output frequency and the second output frequency.
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