9 July 2008 L-band orthomode transducer for the Sardinia Radio Telescope
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Abstract
We describe the design, construction, and characterization results of a compact L-band (1.3-1.8 GHz) Orthomode Transducer (OMT) for the Sardinia Radio Telescope (SRT), a 64 m diameter telescope which is being built in the Sardinia island, Italy. The OMT consists of three distinct mechanical parts connected through ultra low loss coaxial cables: a turnstile junction and two identical 180° hybrid power combiners. The turnstile junction is based on a circular waveguide input (diameter of 190 mm,) and on four WR650 rectangular waveguide cavities from which the RF signals are extracted using coaxial probes. The OMT was optimized using a commercial 3D electromagnetic simulator. The main mechanical part of the turnstile junction was machined out of an Aluminum block whose final external shape is a cylinder with diameter 450 mm and height 98 mm. From 1.3 to 1.8 GHz the measured reflection coefficient was less than -22 dB, the isolation between the outputs was less than -45 dB, and the cross polarization was less than -50 dB for both polarization channels.
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Alessandro Navarrini, Tonino Pisanu, "L-band orthomode transducer for the Sardinia Radio Telescope", Proc. SPIE 7014, Ground-based and Airborne Instrumentation for Astronomy II, 70147N (9 July 2008); doi: 10.1117/12.790557; https://doi.org/10.1117/12.790557
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