Development Of X-Band Oscillator Based On High-Temperature Superconducting Resonator

The long-term stability of frequency and phase noise of microwave oscillator is very important as the critical component of microwave systems. Thus, in this paper, a X-band oscillator based on HTSC resonator is developed for the analysis of oscillator theory and the study of practice in engineering.A feedback oscillator model is employed to design the X-band oscillator, which consists of an amplifier and a feedback network. And the feedback network includes a phase shifter composition and a resonant network depended on HTSC resonator. The start-up condition of oscillator is analyzed theoretically. Meanwhile, the factors of the phase noise of oscillator are analyzed based on the Leeson phase noise model. It is found that the quality factor of the resonant network play an important role on the phase noise of oscillator. And the higher the quality factor, the better the phase noise of oscillator. Moreover, the theory of HTSC resonator as a resonant network is described, and several important factors that affect the quality factor of HTSC resonator are analyzed in this paper.Then, the overall design of the oscillator is analyzed and realized to put forward the basic scheme based on the theoretical analysis of oscillator. The HTSC resonator model is built using Electromagnetic simulation software HFSS to analyze the influence of the coupling structure on the quality factor and stability of the HTSC resonator. Accordingly, the appropriate coupling mode and structure is selected. What’s more, the loop amplifier is designed using two BJT in series to meet the set-up gain condition of oscillator. Meanwhile, the low noise model is used to ensure the output noise at a very low level, so as to improve the phase noise of the oscillator. The phase shifter which can be continuously adjusted in 360 degree range is implemented using analog phase shifter to meet the set-up phase condition of oscillator. And directional coupler is designed to complete the overall design of the oscillator.Finally, all the components and devices of the oscillator are debugged and tested to meet the corresponding index. In the present case, the loaded quality factor of the HTSC is up to 410000, which is beneficial to achieve a much better phase-noise performance. Eventually, the realization of X-band oscillator is completed based on HTSC resonator. Clutter suppression reach more than 70 d B,And the performances of the single-side band phase noise of the oscillator are:-86.05 d Bc/Hz@1k Hz,-109.17 d Bc/Hz@10KHz,-118.74 d Bc/Hz@100KHz,-140.95 d Bc/Hz@1MHz.