Research Of Low Phase Noise Oscillator Based On High Q Dielectric Resonator

With the rapid development and extensive application of satellite communications, mobile communications, radar navigation and other modern wireless communication systems, the application research for high-precision frequency source signal has gained more and more attention by people and it has become a very interesting topic to explore technical approach to optimize the phase noise. With extensive application of new ultra low loss resonant material, a variety of high-Q resonators are widely used in the design and manufacturing of oscillators. Compared with the traditional oscillators, the ones based on high-Q resonator have lower phase noise and higher frequency stability.The main work of this paper can be summarized as follows:(1) Present a high Q tunable cylindrical cavity dielectric resonator structure based on new ultra low loss dielectric material. With open waveguide electromagnetic calculation method, the analytical formula of the resonant frequency and Q value of the TE011 main mode are obtained. The simulation changes of resonant frequency of the TE011 main mode and second HE111 mixed mode can be get by altering the resonator’s parameters in Ansoft HFSS software. Design and optimize the resonator’s exciting and coupling structure, then, a high Q tunable cylindrical cavity dielectric resonator is fabricated and measured. By adjusting the tuning metallic lead with threads at the top of the resonator, the resonant frequency of the TE011 main mode can be changed slightly and the space of the resonant frequency between the TE011 main mode and the second HE111 mixed mode can also be altered.(2) According to resonant frequency of the TE011 main mode of the proposed high Q dielectric resonator, one stage, two stage and three stage low noise amplifier is designed which operating frequency is near 3.9GHz and the performance of the amplifier meet the design requirement in practical measurement. In order to suppress the second HE111 mixed mode of the proposed high Q dielectric resonator, a fourth-order band-pass filter is designed and fabricated which center frequency is 3.85 GHz and measured 3dB bandwidth of is near 150 M. In measurement and tuning process, the interface between the TE011 main mode and second HE111 mixed mode is reduced to increase the stability of the system.(3) The built high Q tunable cylindrical cavity dielectric resonator oscillator(DRO) system is a serial positive feedback closed-loop system which is composed of 5 blocks, high Q tunable dielectric resonator, low noise active amplifier, band-pass filter, mechanically tunable phase shifter, 10 dB directional coupler. A relatively low phase noise level is achieved in practical measurement for this designed high Q tunable serial positive feedback dielectric resonator oscillator(DRO) system.