W Band Microstrip Zigzag Line Traveling Wave Tube

The traveling wave tube has characteristics, as high power, high efficiency, high gain, wide band and long life. Slow-wave structure as the major part of amplifying the microwave energy, is the core of TWT, its performance directly determines the traveling wave tube’s technical level. With the development of the vacuum electronic technology, a lot of novel slow-wave structure appeared, many of their characteristics that the traditional slow-wave structure’s can not compare with. Microstrip meander-line slow wave structure can be manufactured simply and needs low cost, it is suitable for mass production, so it possesses a promising prospect. The slow-wave structure generally use the ribbon electron beam, the total current intensity can be increased without any increase in current density, as the same time, the processing of the structure can be employed the matural microfabrication technology, then it can meet the demand of slow-wave circuit miniaturization.This paper using the electromagnetic simulation software HFSS to analyze related characteristics of a microstrip meander-line TWT which work on W waveband, the results show that, both of the improved and the traditional meander-line slow-wave structure’s dispersion characteristic are not any obvious improvement, but the improved microstrip meander-line slow-wave structure’s normalized phase speed and coupling impedance obviously better than the traditional’s. To slow-wave structure, the medium loss is small; the conductor loss makes the normalized phase speed increased and the coupling impedance reduced. The improved meander-line slow-wave structure working at high frequency has a small reflection and good transmission characteristic compared with the traditional meander-line slow-wave structure. Dielectric loss and conductor loss has less effect on the reflection characteristics, while the impact of transmission characteristic is great.Using the electromagnetic simulation software HFSS to respectively analyze the improved microstrip meander-line slow-wave structure that supported by the horizontal medium rod with the medium plate and the longitudinal medium rod with the medium plate, the results show that, under the support of the medium rod, the coupling impedance raised, normalized phase ratio increased. Discussing the high frequency characteristic influence on the improved meander-line slow-wave structure that supported by the horizontal and longitudinal medium rod that caused by the medium rod’s width and gap, the results show that, the increased medium rod’s width can decrease the normalized phase speed and lessen the coupling impedance, while the changes of the medium rod’s gap do not have apparent effect.Using electromagnetic simulation software CST PIC solver particle studio to analyze note-wave interaction of a microstrip meander-line TWT that worked on W waveband. The results show that, beam voltage with8.9kV, beam current with100mA and the input power with40mW can make the output power and gain maximum at the central frequency96GHz, and the3dB bandwidth is over4GHz.