A Compact L-Band Orthomode Transducer for Radio Astronomical Receivers at Cryogenic Temperature

Abstract

We describe the design, construction and\ud performance of a compact orthomode transducer (OMT) for the\ud L-band receiver (1.3 GHz - 1.8 GHz) of the Sardinia Radio\ud Telescope (SRT). The complete OMT consists of a cylindrical\ud orthomode junction (OMJ), which is presented in this paper, and\ud two identical 180° hybrid power combiners in double ridged\ud waveguide, which have been proposed in a previous work. The\ud OMT operates at the cryogenic temperature of 20 K to reduce its\ud thermal noise contribution to the noise of the receiving chain.\ud Therefore, particular care has been taken in the design of the\ud OMJ to minimize its dimension and insure a good thermalization.\ud The proposed OMT has been designed and optimized by using\ud CST Microwave studio, and then manufactured, tested at room\ud temperature, and installed on the L-band receiver of SRT. The\ud measured results fully comply with the design specifications. In\ud particular, the isolation between the OMT output ports is more\ud than 40 dB, and the cross polarization is less than -35 dB for both\ud polarization channels

Recent Advances of the BIRALET System about Space Debris Detection

“…The receiver of the BIRALET system is the SRT, a 64 m fully steerable wheel-and-track parabolic antenna ( Figure 1) devoted mainly to radio astronomical observations, located in Pranu Sanguini (Northeast from Cagliari), operating in the frequency range from 0.3 to 116 GHz. In addition to the 64 m primary parabolic mirror, the antenna is equipped with a 7.9 m secondary mirror and the beam waveguide system (BWG), which includes two 2.9 m mirrors and one 3.9 m mirror, for a total of four focal positions [16][17][18][19][20]. To better clarify the mirrors and foci configuration of the SRT, a sketch of the antenna is reported in Figure 2, whereas Table 1 summarizes the key features of the radio telescope.…”

Space Debris Detection in Low Earth Orbit with the Sardinia Radio Telescope

“…In full operational mode, the SRT is able to host up to 20 remotely controllable receivers and to observe the sky with high efficiency in the frequency range between 0.3-116 GHz [13]. In order to observe the signal sent from FTS and scattered by the debris, the coaxial dual-feed L-P band (0.305-0.410 GHz, 1.3-1.8 GHz) cryogenic receiver of SRT has been used ( Figure 1) [14][15][16][17]. The features of the transmitter and receiver antennas at 410 MHz are reported in Table 1.…”

A Compact In-Line Waveguide-to-Microstrip Transition in the Q-Band for Radio Astronomy Applications

“…It converts the RF input into an infrared frequency (IF) input at a lower frequency and keeps the same information [1]. Since the signals caught from the antenna are very low in power, the components of the receiver chain must have low losses and noise [2,3]. Moreover, the high frequencies of certain signals processed in radioastronomy require very small devices, whose constructive tolerances play a critical role in the design.…”