Implementation of frequency synthesizer with ultra wide-band and low phase noise

A new method of the implementation of frequency synthesizer is introduced, of which the frequency scope is from 4 to 16 GHz and the step is 1 MHz, with ultra wide-band, small step and low phase noise. Adopting frequency-mixed PLL scheme, the frequency dividend ratio in loop is greatly reduced; choosing components with low phase noise, and using comb spectrum generator instead of traditional big step loop, low phase noise index is achieved in output. In 16 GHz output, phase noise is less than -90 dBc/Hz . By analyzing the synthesizer index, some questions are discussed, of which should be careful in the process of designing frequency mixing loops.