Low Sidelobe Corrugated Horn Antennas for Radio Telescopes to Maximize ${\rm G/T}_{\rm s}$

Improving the G/T_s of radio telescopes and radiometers and their associated receive subsystems translates into increasing the ground received signal-to-noise ratios. Therefore, low noise amplification with cooling operation is required. However, the system designer must select an appropriate feedhorn antenna with low sidelobes and an adapted illumination at the edge of the reflector since the noise originated from the surroundings will be collected by the horn and added directly to the overall system temperature. Lower sidelobes help also to improve the spillover efficiency of the radio telescope which will lead at the same time to an increase of the gain. Three new corrugated horn antenna designs with Gaussian-shaped patterns in the main beam are presented in this paper. These designs were made for specific radio astronomy and radiometry applications. These designs are shorter than their similar performance conical corrugated counterparts. Two of the designs present sidelobe levels below -40 dB and as a consequence they improve the G/Ts relationship. Measured performance results are also presented. All of the designs have been included in latest generation radio telescope and radiometer systems.