Abstract
The wideband gain and voltage standing wave ratio (VSWR) performance of quad-ridged horn antennas in general are restricted due to the excitation of higher order modes in the coaxial to quad-ridged waveguide transition. This results in large gain variations vs. frequency and break-up of the radiation patterns at higher frequencies. In this paper, a quad-ridged horn antenna is presented with optimized radiation characteristics and VSWR performance. The performance of the antenna was optimized by separating the antenna into two subsections, viz. a coaxial to quad-ridged waveguide transition section and a flared quad-ridged horn section. The performance of each section was optimized individually using a numerical solver – CST Microwave Studio. Three possible configuration of the coaxial to quad-ridged waveguide transition section were considered and optimized. Four configurations for the flared quad-ridged horn section were also investigated. The best performing configuration from each one of the two sections were combined to yield the final design of the optimized quad-ridged horn antenna. The numerical performance of the quad-ridged horn antenna was validated through measurements, performed in a compact antenna test range. The optimized antenna has a 12.5:1 frequency bandwidth from 0.8 to 10 GHz. Over this frequency range, the antenna has a VSWR performance typically better than 2.5:1, stable boresight gain and radiation patterns for both ports with more than 30 dB isolation between the two ports.
Acknowledgement
This research was supported by the National Research Foundation of South Africa.