Indian Journal of Science and Technology

Abstract

Aim of Findings: A modified mirror shaped waveguide-type stepped septum polarizer is suggested and verified using Ansoft HFSS. Mirror profile performs better than the conventional varying thickness polarizer in terms of phase-angle, reflection loss and isolation. Methodology Employed: The 3D structure has been simulated using HFSS. The parameters are initially optimized using a WASPNET tool and later implemented in HFSS.WASPNET is a specially designed tool which automatically adjusts the dimensions according to the specifications thus reducing mathematical computations. By performing a number of simulations regarding the thickness and dimension profiles, it is concluded that the performance parameters are not degraded. Final Results: FEM based simulations on the device suggest that mirror shaped waveguidetype profile performs better than the varying thickness profile waveguide-type septum. Initially the thickness of the septum has to be decided to construct an effective septum according to its requirements. Thickness of 0.3 mm performs better than the profiles greater than 0.5 mm thickness. Similarly, the varying thickness profile was simulated and set to 0.2–0.6 mm as it gives better performance. The axial ratio is measured in terms of the angle between the TE10 and TE01 modes, is seen to be 89.75/90.44 between S31 and S32 respectively, ideal value being 90 degrees. The S11 of mirror shaped septum gives reflection coefficient which is found to be greater than -31dB for the entire band compared to that of varying profile. The performance is found to exist over the entire band and not restricted to the center frequency. The isolation characteristics is >25dB which is better than the conventional design. This shows that a good isolation is maintained between both the ports.
Keywords: Mirror Shaped Septum Waveguide Polarizer, Square Waveguide Polarizer, Stepped Septum Polarizer