10 GHz-100 GHz Compact Double-Ridge Horn Antenna for Ultra-Wideband Millimeter-Wave Biomedical Imaging Applications

This paper presents the design of a compact double-ridge horn antenna for radar-based ultra-wideband millimeter-wave (mm-wave) biomedical diagnostics. The proposed antenna is composed of a coaxial to double-ridge waveguide (DRW) transition and a free-space matching section. The antenna is designed such that it can be fed using a commercial 1.00 mm coaxial flange launcher. The effect of the ridge profile inside the back-cavity structure of the designed transition is investigated and optimized to achieve an ultrawideband single-mode bandwidth. Finally, to achieve a smooth transition and a good impedance match to the free-space, exponentially-tapered matching section is employed and optimized. The antenna has small aperture size of 20 mm×24 mm and demonstrates stable gain and symmetric radiation patterns across the bandwidth.