A Dual-Band Coaxial Waveguide Mode Converter for High-Power Microwave Applications

A dual-band coaxial waveguide mode converter is investigated. In the converter, the TEM mode (Coa.TEM) and TM₀₁ circular waveguide (Cir.TM₀₁) mode are transformed simultaneously into TE₁₁ coaxial waveguide (Coa.TE₁₁) mode and TE₁₁ circular waveguide (Cir.TE₁₁) mode, respectively. The optimized geometrical dimensions are achieved by employing the mode coupling theory. A mode converter at 1.3 GHz and 5.0 GHz is designed, and conversion efficiencies of Coa.TEM−to-Coa.TE₁₁ and Cir.TM₀₁−to-Cir.TE₁₁ are 99.88% and 99.70% at central frequency, respectively. Over the frequency ranges 1.15–1.51 GHz and 4.87–5.19 GHz, the conversion efficiency exceeds 90%. A good agreement between theoretical calculations and computer simulations is observed, demonstrating the feasibility of the dual-band mode converter.