C-band Low Phase Noise Frequency Synthesizer

Frequency synthesizer determines the performance of the electronic equipments, plays an important role in our lives. Along with the development of modern military, national defence and wireless communication, many electronic systems such as mobile communication, radars and guided weapons set increasingly higher requirements on the synthesizer. Modern communication system lays particular emphasis on low phase noise and low spur.This subject comes from the project:C band low phase noise frequency synthesizer in Chengdu SaiYing Science and Technology Co. Ltd. There are many difficulties in the module A, such as high working frequencies, very low phase noise , wide band and hopping. Accordingly to the basic theory of frequency synthesis, we can't get the performance with just a single PLL. Finally, the hybrid frequency sythesis technology: PLL+Mixer is adopted. We use two PLLs. One is a digital PLL which can achieve the mainly function of hopping. The other is to get a local oscillator with much lower phase noise.. Then we upconvent these two sigals in order to get high working frequencies we demanded. And both of these two PLLs have low multiples (N). So we get the low phase noise. Additionally, both of these two PLLs should hop synchronous to cover the wide band..In the module B ,we used the simple single one loop system , dued. to the purpose of costdown , and we used a wide band VCO and a Fractional-N PD in this system.It is also a wide band and low phase noise hopping frequency synthesizer system.Design and engineering realization of C-band wideband low phase noise radar frequency synthesizer is presented in this paper. At first,the important specifications and the basis theory of the frequency synthesis technology is reviewed . Then, Combining with practice ,the key problem occurred in engineering is described ,and a design procession, a sample manufactured and the results of the sample are given.