A Wideband Circularly Polarized Antenna With a Nonuniform Metasurface Designed via Multiobjective Bayesian Optimization
Yunjia Zeng, Xianming Qing, M.Y.W. Chia
Abstract
A non-uniform metasurface circularly polarized patch antenna is designed using a genuine multi-objective Bayesian optimization (MOBO) method. Instead of aggregating the performance metrics into a single weighted sum, a genuine MOBO approach is adopted to explore the performance trade-offs, where three important antenna performance metrics, input impedance bandwidth, axial ratio (AR) bandwidth, and gain at boresight, are considered as the optimizing targets. Starting from a reference antenna with a uniform metasurface, the non-uniform metasurface antenna is designed by tuning ten physical design parameters automatically. The optimized antenna achieves an operating bandwidth of 25.6% (3.75 GHz–4.85 GHz) with |S11| < -10dB, axial ratio less than 3 dB, and a maximum realized gain of 7.15 dBic. Compared with the reference antenna, the optimized design realizes a 31% enhancement in operating bandwidth while keeping the identical size of 1.12λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.86λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.069λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free space wavelength at center frequency of 4.3 GHz). Good agreement between measurement and simulation results validates the optimization methodology.