Optimization of the quad-ridged horn for the geodetic VGOS station of the Yebes observatory

The next generation Very Long Baseline Interferometry (VLBI) radio telescope sited at the Yebes Observatory is a fully operative 13.2 m ring-focus reflector covering the frequency range from 2 to 14 GHz. A quad-ridged flared horn (QRFH) feed is one of the key components of the receiver system. Calibration methods using well-known celestial sources allow determining the aperture efficiency of the parabola, which in turn can be used as figure of merit for the design of the feed. Currently, the system provides efficiencies slightly above 50 %. With the aim of further improving its performance, a genetic algorithm, combining both physical optics and electromagnetic simulations, has been developed for the optimization of the QRFH feed. Preliminary results demonstrate the validity of the method.