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A wideband 5G millimeter-wave multiple-input multiple-output (MIMO) magnetoelectric (ME) dipole antenna integrated with partially reflective surfaces (PRSs) is proposed. Each ME dipole consists of a planar electric dipole and an equivalent magnetic dipole. Owing to dual radiation modes of the ME dipole antenna, the wide bandwidth can be obtained. To increase the radiation gain, a dielectric slab with planar PRSs is placed over the ME dipole antenna. The PRS and the metal ground plane form a Fabry–Perot cavity, which can increase the radiation gain. Meanwhile, four dielectric cylindrical rings with rotationally symmetric PRSs can construct multiple Fabry–Perot cavities, and a further increase of the radiation gain can be obtained. The metal sidewalls and the polarization diversity are applied to reduce mutual coupling. The measured impedance bandwidth at −10-dB reflection coefficient is 24–43.5 GHz (57.8%). The measured transmission coefficients $\vert {S}_{21} \vert $ , $\vert {S}_{31} \vert $ , and $\vert {S}_{32} \vert $ are less than −27, −37.9, and −46.4 dB, respectively. The simulated and measured maximum radiation gains are 17.3 and 16.1 dBi, respectively. Thus, the proposed 5G millimeter-wave MIMO ME dipole antenna integrated with PRSs features wide bandwidth, high isolation, and high radiation gain.

This focuses on developing a new platform for the thin-film bulk acoustic wave (BAW) resonator, which features predefined sealed cavities, self-formed acoustic boundaries, and compatibility with subsequent fabrication. Different from conventional BAW resonator fabrication methods, this work has simplified fabrication by using silicon migration technology: building freely predefined cavities with self-formed acoustic boundaries without patterning the piezoelectric layer in only two steps (etching and annealing). Additionally, the sealed cavity is sturdy enough to be compatible with subsequent hetero-integrating with other devices. For higher frequency and better electromechanical coupling ( $K^{2}$ ), the proposed platform can excite the second-order asymmetric Lamb wave mode (A2) in scandium-doped aluminum nitride (Al1–xScxN) film with an optimized stress field. The fabricated devices demonstrate S1 and A2 resonant modes at 1.58 GHz and 3.52 GHz with electromechanical coupling coefficients of 1.47% and 5.12%, respectively. [2023-0185]