Design of a 9.4 GHz overmoded smoothwall TE₁₁HE₁₁ converter

High power microwave(HPM) sources usually employ overmoded output waveguide to obtain higher power capacity. In designing feeder of beam waveguide and reflect antenna, TE11 mode needs to be convert to HE11 mode to radiate a quasiGaussian beam with quite low side lobe. RF breakdown will occur in corrugate gap when traditional corrugated TE11 HE11 mode converter is used in HPM field. In order to solve this problem, a method to design overmoded smoothwall TE11HE11 converter was investigated. Using an iterative synthesis method based on coupledmode theory, a 9.4 GHz, 70 mm overmoded smoothwall TE11 HE11 converter was designed, and contrast to electromagnetic simulation result, the scalar Gauss ratio of the output beam is higher than 99.5% from 9.1 GHz to 9.7 GHz, the power capacity is as high as 4.9 GW.