X-band Cnc Stabilized Gunn Oscillator Research

Microwave oscillators are core components for microwave systems of communications, radars, electronic countermeasures, instrumentations and others, and they determine the overall performance of these microwave systems. With the wide application and rapid development of microwave systems, more requirements are proposed to microwave oscillators, which promote the rapid development of microwave oscillator technology.This thesis studies a kind of X-band digitally controlled frequency Gunn oscillator. The electric tuning technology is combined with the digital control frequecy technology to make the working frequency of the Gunn oscillator be well controlled by the computer, and thus an intelligent digital control VCO system is formed. So this oscillator has much good performances such as high frequency stability, low phase noise, etc.The main content of this thesis:Firstly, an X-band double-tuned waveguide-type Gunn oscillator was designed according to the theory of negative resistance oscillator, in which the YIG(Yttrium Iron Garnet) broad tuning was combined with the varactor fast tuning. Moreover, the characteristics of frequency stability and phase noise were also analyzed and discussed. Then, the digital frequency-measurement circuit and the frequency-control circuit were designed, which were composed of several circuit modules, including microwave frequency divider circuit, microwave coupled power divider circuit and frequency control circuit. The detailed theory analysis and calculations were made for the circuit modules, and the suitable devices were selected. Thus, a complete closed-loop-controllable digital control frequency stabilized System was formed by combining the digital frequency control circuit and the Gunn oscillator. The system can output microwave signals at preset frequency, while higher frequency preset accuracy can be ensured.Finally, the engineering test was made. The results indicates that the stable frequency range of the digital controlled oscillator reached above 100MHz, and the controllable frequency points were 20. The phase noise in frequency band is superior to-95dBc/Hz@10kHz, and the precision of the frequency control in standard presetting frequecy is within±100kHz. So, the design requirements of the system have been achieved basically.