@article {13_IEEETHz_Leal-SevillanoCooperRuiz-CruzEtAl_225GHzCircularPolDuplexer, title = {A 225 GHz Circular Polarization Waveguide Duplexer Based on a Septum Orthomode Transducer Polarizer}, journal = {IEEE Transactions on Terahertz Science and Technology}, volume = {3}, number = {5}, year = {2013}, month = {Sep.}, pages = {574-583}, abstract = {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.}, keywords = {Circular polarization, duplexer, orthomode transducer, terahertz}, issn = {2156-342X}, doi = {10.1109/TTHZ.2013.2264317}, url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=\&arnumber=6525512}, author = {C A Leal-Sevillano and Cooper, K B and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} }