Characteristic Mode-Guided Trust-Region-Based Optimization for Mode Manipulation in Dual-Band Metantenna Design

A characteristic mode (CM)-guided trust-region-based optimization technique for dual-band metantenna design is proposed. The technique automatically manipulates the CMs of a metantenna to achieve desired radiation patterns at desired frequency bands. Mode selection and tracking as the key steps of the technique are developed to track and detect desired, unwanted, and new unwanted modes. A trust-region optimization framework with sensitivities is exploited to manipulate the desired modes and adaptively remove unwanted modes. By optimizing the CMs of nonspecific-feeding-structure, the design achieves enhanced performance with a simplified structure. A dual-band metantenna for 5G applications, as an example, is optimized to obtain two CMs resonating at 28.4 and 38 GHz, respectively without any unwanted modes below 44 GHz. Then a feeding network is designed to excite the desired modes of metantenna. The design verifies the proposed method with the realized gain of 3.7-7.23 dBi and 5.7-10.1 dBi as well as desired consistent radiation patterns over the measured impedance bandwidths (for |S-11| < -10 dB) of 22.2-28.2 GHz and 34.3-41.6 GHz, respectively.