New Type Of Planar Microstrip Slow-wave Structure Research

Traveling-wave tube is widely used and highly relied upon as heart in a variety of microwave systems, such as communications, guidance, remote sense, radar and other fields. The great progress of modern electronic science and technology pushes the traveling wave tube into the position where broader bandwidth, higher efficiency, smaller size and lighter weight are needed. Meanwhile, in order to reduce the cost, traveling wave tube would be constituted by simple elements which are easy to build up. However traditional traveling-wave tube can no longer meet this trend, researchers are always exploring new types of slow-wave structure to satisfy the requirements of the traveling wave tube’s miniaturization. Composed of periodic metal conductor placing on dielectric substrate, the Planar microstrip slow-wave structure can easily achieve a high accuracy by using micro-fabrication technology. Using sheet electron beam, the entire tube except the electron gun can easily be printed on a dielectric substrate to gain low voltage and low cost.In this paper, the microstrip elliptic ring slow wave structure and the microstrip rectangular ring slow wave structure are examined after studying the traditional microstrip meander line slow wave structure. Microstrip ring structure can be regarded as the combination of two single microstrip structures. Microstrip rectangular ring can be seen as two microstrip meander line added together as well as microstrip elliptical ring which is formed by two microstrip elliptical meander line. The main contents of this paper are:1.Roughly analyzed the phase velocity of the microstrip slow wave structure and how it is affected by the structural parameters, the results fit the computer simulation and can be helpful in designing a new structure. Summarized the theories for the dispersion of traditional microstrip meander line slow-wave structure which are also applicable to analyze the microstrip rectangular ring slow wave structure.2. Presented and analyzed a novel microstrip ring slow-wave structure, examined each structural parameter’s impact on dispersion characteristics and coupling impedance by using the electromagnetic field simulation software HFSS. Changed the microstrip ring into microstrip elliptical ring to improve the high frequency characteristics. Results show that the microstrip elliptical ring structure can effectively reduce the phase velocity. Microstrip rectangular ring structure was analyzed too, and investigated the high-frequency characteristics on different structural parameters as well as different dielectric material.3. Analyzed the beam-wave interaction of the microstrip elliptical meander line slow wave structure using the electromagnetic simulation software CST. The results show that the elliptical meander line is a low-voltage, wide-bandwidth and high-efficiency slow wave structure.