Adjustable Iris-Post Waveguide Polarizer for Ku-band Satellite Uplink Systems

This paper presents the results of numerical optimization of main operating parameters of an adjustable waveguide polarizer for satellite uplink systems. The developed polarization conversion device has a waveguide structure, inside which two metal pins are located in the center of a broad wall. Besides, two thin metal diaphragms are symmetrically located on both sides of the pins. Mechanical adjustment of the heights of pins provides the ability of fine tuning of operating electromagnetic parameters. This is necessary and important feature for a polarizer, since it allows to reduce the influence of inaccuracies of the manufactured device's structure. Developed polarization converter introduces additional phase difference close to 90 degrees for the input linearly polarized fundamental waves at the output and maintains good matching for both modes. The combination of these properties results into an efficient transformation of circularly polarized electromagnetic waves into linearly polarized waves. The operating electromagnetic parameters of the considered waveguide device are expressed through the elements of its scattering wave matrix. Numerical simulations in the frequency range 14.0-14.5 GHz were carried out using the finite elements method in the frequency domain. Main performance characteristics were optimized, including output differential phase difference, standing wave factor, reflection and transmission coefficients, ellipticity parameter, discrimination of the linear polarization. The designed guide polarization converter with two pins and diaphragms provides an output phase difference of 90° ± 3.25° in the operating frequency range of 14.0-14.5 GHz. Its peak value of the standing wave factor by voltage is 1.15 for both linear polarizations. In addition, the maximum level of discrimination of the linear polarizations is −31 dB. The maximum level of ellipticity parameter equals to 0.48 dB. Obtained numerical results can be used to develop and estimate the characteristics of new adjustable waveguide polarizers with diaphragms and pins.