Abstract: In this paper, a method of 5MHz~1GHz low phase noise frequency synthesizer is given. Under considering the phase noise of output signal, and using the technology of direct, indirect and direct digital synthesis frequency synthesis, the paper provides a reasonable design of phase lock loop, frequency division, frequency multiplication, attenuator, amplifier, filter, power division. The frequency synthesizer can achieve a relatively high level of phase noise based on the current hardware.

Key words: Frequency synthesizer, Low phase noise, Frequency spreading