WP-1310.3 – Feasibility Study For The Integration of a Directive Radiometer on the Sardinia Radio Telescope
Module 1310-3 consists of a K/Ka-band wide-band passive antenna-feed chain for the SRT Beam-WaveGuide (BWG) optics of the Sardinia Deep-Space Antenna (SDSA). The system is the result of a feasibility study aimed at integrating the Ka-band downlink deep-space frequency band and the K-band channels commonly used in atmospheric microwave radiometry into the same antenna-feed chain. Since the deep-space Rx signals and the water vapour measurements refer to the same pointing direction, this integration allows for an accurate characterization of the tropospheric radio path delay and, therefore, an accurate calibration of the Doppler residual data recorded during a SDSA tracking of a spacecraft signal.
The antenna-feed chain developed at CNR-IEIIT (https://www.ieiit.cnr.it/) is based on the electromagnetic layout of Figure 1, consisting of
• a feed-horn collecting the signal received by the BWG optics,
• a marker injector used to provide a reference signal for receiver calibration,
• a polarizer converting the two circular polarizations into linearly polarized signals, and
• an ortho-mode transducer that separates the two linear polarizations
The K/Ka-band antenna-feed assembly implementing the electromagnetic layout of Figure 1 is shown in Figure 2. It consists of different mechanical building blocks that were manufactured through lathe machining, CNC milling, and electrical discharge machining. The several assembly parts were, then, subjected to surface passivation or plating to improve electrical conductivity. The measured RF performances of the system are summarized in Table 1.
