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15 July 2010 The dual-band LP feed system for the Sardinia Radio Telescope prime focus
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We present the design of the passive feed system of the dual-band receiver for the prime focus of the Sardinia Radio Telescope (SRT), a new 64 m diameter radio telescope which is being built in Sardinia, Italy. The feed system operates simultaneously in P-band (305-410 MHz) and L-band (1300-1800 MHz). The room temperature illuminators are arranged in coaxial configuration with an inner circular waveguide for L-band (diameter of 19 cm) and an outer coaxial waveguide for P-band (diameter of 65 cm). Choke flanges are used outside the coaxial section to improve the crosspolarization performance and the back scattering of the P-band feed. The geometry was optimized for compactness and high antenna efficiency in both bands using commercial electromagnetic simulators. Four probes arranged in symmetrical configuration are used in both the P and the L-band feeds to extract dual-linearly polarized signals and to combine them, through phased-matched coaxial cables, into 180 deg hybrid couplers. A vacuum vessel encloses the two P-band hybrids and the two L-band hybrids which are cooled, respectively at 15 K and 77 K. For the P-Band, four low loss coaxial feedthroughs are used to cross the vacuum vessel, while for the L-Band a very low loss large window is employed. The P-band hybrids are based on a microstrip rat-race design with fractal geometry. The L-band hybrids are based on an innovative double-ridged waveguide design that also integrates a band-pass filter for Radio Frequency Interference (RFI) mitigation.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
G. Valente, T. Pisanu, P. Bolli, S. Mariotti, P. Marongiu, A. Navarrini, R. Nesti, A. Orfei, and J. Roda "The dual-band LP feed system for the Sardinia Radio Telescope prime focus", Proc. SPIE 7741, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy V, 774126 (15 July 2010);


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