Research On Different Cross-section Shapes Of Millimeter Wave Helix Slow-wave Structures

Traveling-wave tube(TWT)is the most widely used microwave tube in both military and civilian areas currently. Due to its wide bandwidth, it has become the most important microwave tube in modern electronic warfare. However, the fabrication technique is not totally automatic. At the same time, the consistency and reliability of TWT are also bad. Coupled with the increasing frequency, the manufacture of TWT becomes more difficult because of the much smaller size. Due to the low space-charge effect, large current and high output power, sheet electron beam is an ideal radiation source for the design of millimeter-wave devices. Therefore, one important direction for TWT in the future is developing the new effective interaction slow-wave circuits with sheet electron beam based on MEMS technology.Several important and valuable results are achieved and listed as the following:1. This paper explores the high-frequency characteristics(dispersion characteristic and coupling impedance) of the helix slow-wave structures with different cross-section shapes: the flabellate, rectangular, square and the traditional circular. As the rectangular helix slow-wave structure is more suitable for compact TWT, the rectangular helix is chosen for the further research.2. This paper also focuses on parameters which impact the high-frequency characteristics of the rectangular helix slow-wave structure. By studying on the transmission characteristic in the band of 130-148 GHz, 11 S is less than-20 dB, 21 S is greater than-0.1dB.3. In the beam-wave interaction simulation of the rectangular helix slow-wave structure with sheet electron beam, a design project is introduced, which can produces 48 W output power and achieves 12% electron efficiency at the center frequency of 140 GHz. Meanwhile, the 3-dB bandwidth of the project reaches 6GHz. It has great significance for the fabrication of millimeter wave rectangular helix TWT.