Development of Double-Ridged Wavegide Orthomode Transducer for the 2 MM Band
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This paper describes the design and development of the 2 mm band orthomode transducer (OMT) for the Band 4 cartridge receivers of the Atacama Large Millimeter/Submillimeter Array (ALMA). The OMT consists of a double-ridged waveguide followed by a Bϕifot type junction with a main arm and two side arms. The main arm output is a multi-section step transformer followed by an E-plane bend and an oval waveguide to be realized the OMT with a two-split block using conventional Computer Numerical Control (CNC) milling techniques. The prototype OMT shows return loss of better than 20 dB, cross polarization coupling of better than 30 dB and insertion loss of less than 0.4 dB across 125 – 163 GHz. Furthermore, production feasibility was demonstrated through the evaluation of seven OMTs with a production design. The design of the developed OMT is so simple that it is easily scaled to submillimeter frequencies.
KeywordsOrthomode Transducer (OMT) Double-ridged waveguide Radio Astronomy ALMA
The author would like to thank T. Wada and M. Inata for testing OMTs. I would also like to thank T. Noguchi and A. Endo for their invaluable comments. I am also grateful to the entire people of the Advanced Technology Center and ALMA-J project office for their useful discussions and support.
- 1.A. J. Beasley, R. Murowinski, and M. Tarenghi, The Atacama Large Millimeter/submillimeter Array: Overview & status. Proc. of SPIE 6267, 2 (2006).Google Scholar
- 2.S. Asayama, S. Kawashima, H. Iwashita, M. Inata, Y. Obuchi, T. Suzuki, and T. Wada, “Design and Development of ALMA Band 4 Cartridge Receiver,” Proc. of the 19th Int. Symp. on Space Terahertz Tech., 2008Google Scholar
- 3.E. J. Wollack, W. Grammer, and J. Kingsley, The Bϕifot Orthomode Junction, ALMA Memo 425, 2002.Google Scholar
- 4.G. Narayanan and N. Erickson, “Full-Waveguide Band Orthomode Transducer for the 3 mm and 1 mm Bands,” Proc. of the 14th Int. Symp. on Space Terahertz Tech., pp. 508–512, 2003.Google Scholar
- 6.G. Moorey, R. Bolton, A. Dunning, R. Gough, H. Kanoniuk, and L. Reilly, A 77–117 GHz Cryogenically Cooled Receiver for Radio Astronomy,” Proc. of the Workshop on the Applications of Radio Science, February 15−17, 2006.Google Scholar
- 7.A. Dunning, “Double Ridged Orthogonal Mode Transducer for the 16–26 GHz Microwave Band,” Proc. of the Workshop on the Applications of Radio Science, February 20−22, 2002.Google Scholar
- 8.A.R. Kerr, “Elements for E-Plane Split-Block Waveguide Circuits,” ALMA Memo 381, 2001.Google Scholar
- 10.M. Kamikura, M. Naruse, S. Asayama, N. Satou, W. Shan, and Y. Sekimoto, “Design and Evaluations of a 385–500 GHz Orthomode Transducer (OMT),” in preparation.Google Scholar