A tri-polarized 12-antenna array working in the 3.5-GHz band (3.4-3.6 GHz) for future 5G (the fifth generation mobile communication) MIMO (Multiple-Input Multiple-Output) operations in the smartphone is presented. In order to reduce the mutual couplings and simplify the design process, orthogonal polarization technique is utilized. By combining a QMSIW (quarter mode substrate integrated wave-guide) antenna and two open-end slots, a compact 3-antenna tri-polarization block operating in the 3.5-GHz band is achieved within a small volume of 17 × 17 × 6 mm3. Thanks to the orthogonal polarization features, the three antennas within the block are able to have good impedance matchings and low mutual couplings between antennas. By integrating four such tri-polarization blocks, a 12-antenna MIMO array is then designed for smartphone applications. It is also due to the tri-polarization feature, the proposed array could attain acceptable isolations and low correlations between antennas with only two additional decoupling structures. The proposed array is fabricated and tested, good antenna performances such as return loss better than 10 dB, isolation higher than 12.5 dB and antenna efficiencies higher than 50% are obtained. The channel capacity of the 12-antenna array is calculated to be about 57 bps/Hz in a 12 × 12 MIMO system with 20-dB SNR (signal to noise ratio), which indicates the proposed array using tri-polarization technique is a good choice for future 5G terminals.

A hepta-band coupled-fed loop antenna for LTE/WWAN unbroken metal-rimmed smartphone applications is proposed. The unbroken metal rim is designed as a part of the loop antenna radiation structure, which is also composed of a system ground, a coupled-fed U-shaped microstrip line, and an L-shaped microstrip line. The feeding and L-shaped microstrip lines are located on an ungrounded area of 72 × 8 mm ² along the top short edge of the system ground plane on an FR4 substrate. The operating band of the antenna is widened by the matching circuit elements on the feeding line. Combining multiple resonant modes generated by the coupling loop, the proposed antenna can operate on two wide operating bands of 824-960 and 1710-2690 MHz. The detailed working principles of the proposed antenna are described. Good antenna radiation characteristics are obtained. Both experimental and simulation results are presented and discussed.

The poly (vinylidene fluoride) (PVDF)-based composite solid-state electrolyte (CSE) has garnered attention due to its excellent comprehensive performance. However, challenges persist in the structural design and preparation process of the ceramic-filled CSE, as the PVDF-based matrix is susceptible to alkaline conditions and dehydrofluorination, leading to its incompatibility with ceramic fillers and hindering the preparation of solid-state electrolytes. In this study, the mechanism of dehydrofluorination failure of a PVDF-based polymer in the presence of Li₂CO₃ on the surface of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) is analyzed, and an effective strategy is proposed to inhibit the dehydrofluorination failure on the basis of density functional theory (DFT). We introduce a molecule with a small LUMO–HOMO gap as a sacrificial agent, which is able to remove the Li₂CO₃ impurities. Therefore, the approach of polyacrylic acid (PAA) as a sacrificial agent reduces the degree of dehydrofluorination in the PVDF-based polymer and ensures slurry fluidity, promoting the homogeneous distribution of ceramic fillers in the electrolyte membrane and enhancing compatibility with the polymer. Consequently, the prepared electrolyte membranes exhibit good electrochemical and mechanical properties. The assembled Li-symmetric cell can cycle at 0.1 mA cm⁻² for 3500 h. The LiFePO₄‖Li cell maintains 91.45% of its initial capacity after 650 cycles at 1C, and the LiCoO₂‖Li cell maintains 84.9% of its initial capacity after 160 cycles, demonstrating promising high-voltage performance. This facile modification strategy can effectively improve compatibility issues between the polymer and fillers, which paves the way for the mass production of solid-state electrolytes.