Optimum-Iris-Set Concept for Waveguide Polarizers

• Published in: IEEE microwave and wireless components letters 2007-03, Vol.17 (3), p.202-204
• Main Authors: Virone, G., Tascone, R., Peverini, O.A., Orta, R.
• Format: Article
• Language: English
• Subjects: Antenna feed systems; Apertures; Applied sciences; Bandwidth; Circuit properties; Circular waveguides; Deviation; dual polarization; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Feeds; Frequency; Geometry; Iris; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Optimization; Phase error; Phase shift; Polarization; Polarizers; Waveguide components; Waveguide discontinuities; waveguide polarizers; Waveguide transitions; Waveguides
• ISSN: 1531-1309; 2771-957X; 1558-1764; 2771-9588
• DOI: 10.1109/LMWC.2006.890474

Novel profiled irises for the design of waveguide polarizers are presented. The two degrees of freedom of their piecewise-circular profile allow one to better control the frequency behavior of the differential phase shift. Thanks to this feature, an optimum iris set can be found by selecting the discontinuities for which the differential-phase-shift deviation from the average value is minimum in the operative bandwidth. This optimum iris set can be identified for several values of the ratio r/lambda 0 , where r is the waveguide radius and lambda 0 is the free-space wavelength at the central frequency. Hence, even if both the waveguide size and central frequency are assigned in the specifications, polarizers with a very low deviation from 90deg of the total differential phase shift can be designed. In this way, the number of waveguide transitions in the antenna feed system can be reduced and the effect of spurious higher-order-mode coupling can be minimized. A Ka-band polarizer in circular waveguide with piecewise-circular-profile irises is described, showing a return loss better than 55 dB and a phase error of about 0.9deg in a 10% bandwidth