A Compact Dual-Band Mode Converter for High-Power Microwave Applications

To realize multiband mode conversion in the high-power microwave (HPM) application system, a novel compact dual-hand mode converter based on a universal method is proposed in this article. The proposed converter has a hybrid circular-embedded coaxial structure, and it integrates the conventional plate-inserted coaxial TEM-TE11 converter and serpentine circular TM01-TE11 converter simultaneously. Its outer and inner waveguides have the same curvature distributions along a longitudinal direction. Both the numerically calculated results and simulations exhibit that its maximum conversion efficiencies at two central frequencies are over 99% with a structure length of 240 mm. Simulated results indicate that the bandwidths reach 390 MHz (at X-band) and 4.2 GHz (at Ka-band), respectively, when the conversion efficiencies are over 95%. A prototype is fabricated and measured. The far-field results demonstrate that coaxial TE11 and circular TE11 modes with high purity are detected at the output port of converter, and the S-parameter measurements illustrate that high conversion efficiencies at 8.4 and 30.5 GHz are obtained. The measurement results have a good agreement with the theoretical predictions and simulations.