Study On Self-excited Frequency-tunable Oscillator

Folded waveguide is an all-metal slow-wave structure and has advantages of heat dissipation, high power, wide bandwidth, structural integrity, and easy processing, etc.Studies on folded waveguide slow-wave structure include folded waveguide TWT,backward wave oscillator and so on. With the development of the manufacture technology, microwave tubes based on folded waveguide extend to higher frequency.Various kinds of folded waveguide oscillators come out, with the efforts of researchers.With further studies on folded waveguide oscillators, its performance have been great improved. Now, the folded waveguide oscillators have wider bandwidth, larger gain, better interaction impedance. As folded waveguide has merits as mentioned above,this thesis designs a multi-band frequency-tunable oscillator.A multi-band frequency-tunable oscillator is designed. The cold structure is designed and the dispersion and interaction impedance curves are given by simulation.The folded waveguide slow-wave structure which is loaded by multilayered dielectric on both ends is simulated by PIC simulation. The influences on the radiation frequency of the oscillator, when the operating voltage or the dielectric loaded on both ends is moved inward or outward, are studied.The main content is listed as follows.1. Present status of microwave oscillators and concrete applications of folded waveguide slow-wave structure are studied.2. The dispersion and interaction impedance of folded waveguide slow-wave structure and the influence of structural parameters on it are analyzed. The optimal parameters and waveguide length are selected.3. The transmission characteristics of the folded waveguide slow-wave structure that was loaded by multilayered dielectric on both ends are studied. The two ways above to tune frequency are analyzed.4. The output properties of the oscillator, including voltage tuning, the average output power and efficiency of the oscillator are simulated. Under this conditions,voltage tuning is discrete. The average output power and efficiency increase with the voltage increasing. When the dielectric structure moves outward, the average output power and efficiency decrease. And the influence of different period number on theaverage output power and efficiency are analyzed.