Design and Optimization of a Coax to WR340 Waveguide Adapter for High Power Microwave Transmission*

Microwave transmission and coupling are fundamental in various high-frequency and high-power applications, with coaxial cables and waveguide systems playing pivotal roles. These systems often require adapters or converters to integrate coaxial and waveguide components, facilitating effective power transfer across a wide range of frequencies. However, the design and modeling of these adapters, particularly SMA coaxial connectors, within waveguide systems pose significant challenges. These challenges arise from factors such as intricate geometries, size constraints, and potential impedance mismatches, which can affect overall transmission performance. This study investigates the design and optimization of a coax-to-WR340 waveguide adapter, specifically engineered to enhance the transmission performance to an N-type bulkhead 180-degree solder-type connector with Teflon dielectric and 50-ohm impedance. The WR340 waveguide employs a meticulously designed stepped structure to ensure precise impedance matching between the waveguide and the coaxial connector. A strategically placed gap between the first step and the coaxial pin, bridged by a copper pin of the same diameter as the coaxial inner pin, is included to prevent undesirable contact between the copper steps and the waveguide wall. The TE₁₀ mode was initiated, and comprehensive frequency sweep analysis using finite element method (FEM) simulations revealed a bandwidth of 261 MHz at -20 dB, extending from 2.01 GHz to 2.62 GHz, with an impressive average transmission efficiency of 99%. At the operational frequency of 2.45 GHz, the adapter achieved a transmission rate of 99.79%, accompanied by a reflection coefficient of -26.84 dB. This modular design, featuring adjustable copper steps, allows for customization of the waveguide structure, enabling optimization for specific frequency ranges or application-specific requirements. The findings underscore the potential of the coax-to-WR340 waveguide adapter to significantly enhance microwave transmission efficiency in various industrial and research applications.