Design and Fabrication of Coaxial Airline Waveguide in High Frequency Bands for Microwave Applications

Coaxial airline waveguides are widely used for precise analysis of the electromagnetic properties of materials at specific frequencies. This paper explores the design, simulation, fabrication, and testing of a cost-effective, customizable coaxial airline waveguide operating over a wide high-frequency band, specifically targeting the X (8–12 GHz) and Ku (12–18 GHz) bands. It aims to characterize toroidal-shaped material samples, investigating their dielectric properties and potential EMI shielding applications for RF devices. The waveguide was designed and optimized using Ansys HFSS tool. Two configurations of the waveguide were designed and fabricated sequentially to facilitate ease of mechanical use and testing, one with soldered SMA connectors and the other with connectors screwed into the internal threading of the waveguide's outer conductor. S-parameters were measured for both models, with the soldered model achieving S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf>at -26.38 dB and S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf>at -4.36 dB at 18.187 GHz, and the screwed model achieving S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf>at -21.43 dB at 13.3 GHz and S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf>at -6.96 dB at 15.13 GHz, closely matching simulated results. Fabrication defects, such as imperfect threading, are suspected to cause sudden drops in the S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf>of the threaded model