Abstract: Based on the wideband high stability and low phase noise direct frequency synthesizer for a system,the phase noise of direct analog frequency synthesizer,agility time and relevant electromagnetic compatibility technologies are studied and analyzed in this paper.The method and conclusion of this paper was used to develop and implement the compact,modular S band frequency synthesizer,and its specifications,such as phase noise,Spurious signal suppression,agility time,can meet the demand of the system.