G-Band High-Power and Ultrawide Band Staggered Double-Vane Slow-Wave Circuit With Double Beams

In this article, the design of a 220 GHz ultrawide band staggered double-vane slow-wave circuit, its fabrication, and cold tests’ results are discussed. The fundamental double modes, including odd and even modes, are adopted to match with the same electron beam to significantly increase the bandwidth. Multiple-beam slow-wave circuit could increase beam current with the enhancement of output power and gain compared with a single-beam structure. Linear taper couplers are designed as input/output structure, and the whole slow-wave circuit with couplers has been fabricated with high precision computer-numerical-control machine. Good agreements with simulation results are found at an ultrawide band about 70 GHz from 207 to 277 GHz with a return loss better than −10 dB and an insertion loss of about −7 dB. Particle-in-cell simulations with a double-mode multibeam two-stage slow-wave circuit within a total length of 45 mm show that it can get a nearly 310 W peak output power at 220 GHz with a 20.6 kV beam voltage and beam current of 2 × 0.08 A. The 3-dB bandwidth over 35 dB reaches about 70 GHz with a driven voltage of 20.6 kV. It agrees well with the cold test results. So, this design could promote the development of ultrawide band with high-power terahertz traveling-wave tubes.