K-band Microwave Frequency Synthesizer Design

With the development of the microwave technology, the request for higher performance microwave frequency synthesizer ,which is regarded as one of the key components in microwave system ,is put forward. Microwave frequency synthesizer with high quality and stability is indispensable no matter in microwave communication or radar applications.In this paper,a K-band microwave frequency synthesizer is studied and designed on account of applications.According to the targets of the system, the design of two PLLs+mixing+direct doubling is confirmed in this paper after optimizing system schemes. That is to say, the first PLL is used to lock the signals from 1.875GHz to 2.375GHz, and the second PLL is used to lock the signals of 7.5GHz.Besides,the first PLL is regarded as the IF input of the mixer, and the second PLL is regarded as the LO input of the mixer. then the outputs of two PLLs are sent to the mixer for first-harmonic mixing. Finally, we double the output of the mixer to get the signal from 18.75GHz to 19.75GHz.In this paper, the technology of synthesizer is introduced first. Secondly, we review the fundamental concepts and basic parts of the PLL, as well as the phase noise and the loop bandwidth. Thirdly, the theory of oscillator and negative resistance are recommended. Finally, the whole design and the implementions are emphasized. Two PLLs are designed concretely, and the simulation results are proved to achieve the system requirements. In the end, the PCB picture of the system is presented.