The Research Of Ku-band Oscillator Based On High-Q Air Cavity

As we all know, microwave frequency source is the key component of electronic systems, such as radar, wireless communications, etc. With the development of electronic technology, the technical requirement of microwave frequency source in electronic system, especially for the phase noise, is getting higher and higher. Futhermore, no matter what kind of frequency synthesis technology is used to develop microwave frequency source, the phase noise performance is always closely related to the phase noise performance of its reference source. Therefore, the research of low phase noise oscillator is of great significance. In this paper, in order to implement a low phase-noise oscillator, the work has been completed as follows:1. Starting from the oscillation condition and the stable oscillation condition as well as basic concepts of phase noise, the Leeson model and equation of phase noise are introduced. Accordingly, some suggestions are given to improve the phase noise of the oscillator.2. The program of Ku-band oscillator based on high-Q air cavity is carried out through analyzing the fundamental principles and comparing the advantages and disadvantages of several common low phase-noise oscillators, such as oscillator with direct feedback, STALO, oscillator with improved direct feedback, oscillator with improved STALO-type and oscillator with interferometric processing. At the same time, the fundamental principle of frequency locked loop technology for improving phase noise is analysed in detail.3. A high-Q air cavity with tunable oscillation frequency at 12.8 GHz is designed and simulated based on the fundamental theory of cylindrical air cavity. Meanwhile, the cavity’s working mode is TE023 mode. And it has following properties: critical coupling input port and adjusted weak coupling output port.4. In accordance with the program of Ku-band oscillator based on high-Q air cavity, lots of components are designed and simulated to implement the overall design of this system, which consist of voltage controlled oscillator(VCO), power amplifier, directional coupler, 3d B bridge, low-noise amplifier, loop filter, adder, phase detector and so on.5. All the components and devices are test to meet the design requirements of the frequency source. Then the frequency source system is built and tested to complete the realization of Ku-band oscillator based on high-Q air cavity. The tested output signal frequency of the frequency source is 12.6618 GHz, the power is about +9d Bm and the phase noise performance is-64.44 d Bc/Hz@1k Hz,-93.50 d Bc/Hz@10k Hz,-97.10 d Bc/Hz@100k Hz,-126.33 d Bc/Hz@1MHz.