Three-dimensional, ultra-wideband micromachined millimetre-wave hemispherical shell antenna: theoretical concept and calibration

This study presents a theoretical design study of a novel three-dimensional micromachined hemispherical shell antenna for ultra-wideband millimetre-wave imaging applications. The antenna is composed of a hemispherical metallic shell which is suspended on top of a high-resistivity silicon substrate using a thin silicon stem. The antenna exhibits two different operational modes and an exceptionally wide bandwidth of more than 80 GHz at the centre frequency of 120 GHz. Simulation results indicate that the antenna performance is highly sensitive to geometrical variations and hence to fabrication inaccuracies. Performing a complete sensitivity analysis using full-wave simulations requires numerous simulation steps and is therefore time-intensive and impractical. This study provides closed-form solutions for all performance metrics of the antenna, followed by a comprehensive theoretical-based sensitivity analysis for evaluating the effects of fabrication imperfections on its bandwidth. The antenna structure is then calibrated for ultra-wideband operations and low sensitivities to fabrication inaccuracies.