| 摘要 |
PROBLEM TO BE SOLVED: To provide a PLL frequency synthesizer, from which spurious is removed. SOLUTION: This synthesizer is provided with a PLL circuit 4 for phase- comparing a reference signal obtained by frequency-dividing the frequency of a signal outputted from a DDS(digital direct synthesizer) 2 via a band-pass filter 3 by a first frequency dividing ratio and a comparing signal of a comparing frequency frequency-divided by a second frequency dividing ratio. The second frequency dividing ratio is set, so that the frequency of a spurious is equal to or higher than the cutoff frequency of a loop filter 5 in the circuit 4.
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