Dual polarized ultra wideband feed system for VLBI global observation system applications

Abstract

A new topology covering the new VGOS (VLBI Global Observation System) configuration is presented. The VGOS's requirement is a feed system covering from 2 GHz to 14 GHz. The new receiver topology is based on a log-spiral antenna printed on a conical surface. To achieve the dual circular polarization, an array of four elements is proposed. A proper balun for feeding the antenna and covering the whole band is also presented. The simulated results of radiation patterns show a pretty high symmetry in the radiation patterns at all frequencies with a maximum CP-XP level greater than 15 dB with a 10 dB gain.