A 225 GHz Circular Polarization Waveguide Duplexer Based on a Septum Orthomode Transducer Polarizer
Carlos A. Leal-Sevillano, Ken B. Cooper, Jorge A. Ruiz-Cruz, José R. Montejo-Garai, Jesús M. Rebollar
IEEE Transactions on Terahertz Science and Technology
Volume: 3, Issue: 5, September 2013
574 - 583
Circular polarization, duplexer, orthomode transducer, terahertz
In this paper, we present the modeling and experimental validation of an efficient, compact, and high-isolation waveguide duplexer operating at 225 GHz. While duplexers based on ferrite circulators are key components of many monostatic radar systems, at W-band frequencies and above the performance of waveguide circulators rapidly deteriorates. The design presented here uses a ferrite-free duplexing concept based on transmitting and receiving in orthogonal circular polarizations. The circular polarization is efficiently generated in waveguide using a septum orthomode transducer polarizer, leading to a compact device with a single horn antenna. The complete duplexer is designed using efficient numerical algorithms, resulting in a fabricated device with a measured 10% fractional bandwidth, a return loss better than 20 dB, isolation of 30 dB, and insertion loss below 1 dB.
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