The fast development of the fifth-generation (5G) wireless systems and substantial growth of data usage have imposed stringent requirements for high-frequency and wideband radio frequency devices. Here, it is reported on a longitudinal leaky surface acoustic wave (LLSAW) mode acoustic resonator with a large electromechanical coupling factor ($k_{\mathrm{t}}^2$ ), high operating frequency, and efficient spurious suppression. Through systematical finite element method simulations, available design spaces such as supporting substrate, propagation angle, and lithium niobate (LN) thickness have been fully investigated with the aim of stimulating the intended LLSAW and suppressing spurious modes concurrently. Optimization results reveal that the LLSAW mode wave propagating in X-35°Y LN/SiC piezoelectric-on-insulator (POI) bilayer structure possesses a large $k_{\mathrm{t}}^2$ without significant interference from other spurious modes. To verify the theoretical analyses, LLSAW resonators were fabricated and exhibited a near spurious-free response with the operating frequency over 6 GHz, and $k_{\mathrm{t}}^2$ as large as 22.7%. This work demonstrates a high-performance LLSAW resonator on the POI platform with a simple prototype as well as potentially providing a high-frequency filtering solution for 5G applications in the 6-GHz spectrum.

There is less “clearance” for the antenna for full-screen mobile phones, which is a higher challenge to antenna miniaturization in radio frequency. Magnetoelectric (ME) antenna stands out as a promising solution to the antenna miniaturization in the fifth generation (5G) wireless communication technology for its superior miniaturization capability compared with conventional electrical antennas. Although many structures of ME antennas have been proposed, their resonant frequency stay below 3 GHz, which cannot satisfy 5G communication. Here we report a magnetoelectric antenna with 445 nm AlN coupled with FeGaB/SiO ₂ multilayers based on the solidly mounted resonator (SMR) structure with Bragg reflectors of SiO ₂ /W/SiO ₂ /W/SiO ₂ , which resonates at 4.97 GHz consistent with theoretical analysis of the reflection performance of the ME antenna. The far-field radiation performance with different FeGaB thicknesses and near-field polarization of the ME antenna were tested. The experimental data demonstrate that the SMR-based ME antenna with 270 nm-thick FeGaB film displays the highest far-field performance with a gain of –25.1 dBi, quality factor of 1207, and radiation efficiency of 0.53% with a circular resonating disk of 300 μm in diameter. Such a compact and high-frequency ME antenna is potentially suitable for the 5G wireless communication systems.

Surface acoustic wave (SAW) devices based on multi-layer structures have been widely used in filters and sensors. The electromechanical coupling factor (K²), which reflects energy-conversion efficiency, directly determines the bandwidth of the filter and the sensitivity of sensor. In this work, a new configuration of dual-mode (quasi-Rayleigh and quasi-Sezawa) SAW devices on a ZnO/SiC layered structure exhibiting significantly enhanced K² was studied using the finite element method (FEM), which features in the partial etching of the piezoelectric film between the adjacent interdigitated electrodes (IDTs). The influences of piezoelectric film thickness, etching ratio, top electrodes, bottom electrodes, and the metallization ratio on the K² were systematically investigated. The optimum K² for the quasi-Rayleigh mode and quasi-Sezawa mode can exceed 12% and 8%, respectively, which increases by nearly 12 times and 2 times that of the conventional ZnO/SiC structure. Such significantly promoted K² is of great benefit for better comprehensive performance of SAW devices. More specifically, a quasi-Rayleigh mode with relatively low acoustic velocity (V_p) can be applied into the miniaturization of SAW devices, while a quasi-Sezawa mode exhibiting a V_p value higher than 5000 m/s is suitable for fabricating SAW devices requiring high frequency and large bandwidth. This novel structure has proposed a viable route for fabricating SAW devices with excellent overall performance.

Recently, surface acoustic wave (SAW) devices based on layered structures are a popular area of research. Multilayered structures, including ZnO and GaN, have shown great performance and can be applied in diverse fields. Meanwhile, thin films, such as AlGaN and n-ZnO, can be added to these structures to form a 2-D electron gas (2DEG) which makes the devices tunable. This work systematically studies the basic properties of SAW devices based on ZnO and GaN multilayers via COMSOL Multiphysics. The sorts of structures with different crystal orientations are simulated, and various acoustic modes are considered. Results show that a range of phase velocity from about 2700 m/s to 6500 m/s can be achieved, and devices based on ZnO and GaN multilayers can meet the requirements of the electromechanical coupling coefficient from about 0 to 7%. Every structure’s unique properties are valuable for diverse applications. For example, c-ZnO/c-GaN/c-sapphire structure can be used for high-frequency and large-bandwidth SAW devices, while SAW devices based on a-ZnO/a-GaN/r-sapphire and 2DEG are suitable for programmable SAW sensors. This work has great reference value for future research into SAW devices.

To meet the demands of highly integrated and miniaturized radio frequency front-end (RFFE) modules, multi-passband filters which support multi-channel compounding come to the foreground. In this work, we proposed a new design of a dual-passband surface acoustic wave (SAW) filter based on a 32°YX-LiNbO₃ (LN)/SiO₂/SiC multilayered structure. The filter is of a standalone ladder topology and comprises dual-mode resonators, in which the shear horizontal (SH) mode and high-order SH mode are simultaneously excited through electrode thickness modulation. The impact of electrode thickness on the performance of the dual-mode resonator was systematically investigated by the finite element method (FEM), and resonators were prepared and verified the simulation results. The electromechanical coupling coefficients (K²) of the SH modes are 15.1% and 17.0%, while the maximum Bode-Q (Q_max) values are 150 and 247, respectively, for the fabricated resonators with wavelengths of 1 μm and 1.1 μm. In terms of the high-order SH modes in these resonators, the K² values are 9.8% and 8.4%, and Q_max values are 190 and 262, respectively. The fabricated dual-band filter shows the center frequencies (f_c) of 3065 MHz and 4808 MHz as two bands, with 3-dB fractional bandwidths (FBW) of 5.1% and 5.9%, respectively. Such a dual-band SAW filter based on a conventional ladder topology is meaningful in terms of its compact layout and diminished area occupancy. This work provides a promising avenue to constitute a high-performance dual-passband SAW filter for sub-6 GHz RF application.