Magnetic sensors actuated by bulk acoustic wave (BAW) have attracted extensive attention due to the fact of their high sensitivity, GHz-level high frequency, and small size. Different from previous studies, suppression of energy loss and improvement in energy conversion efficiency of the BAW magnetoelectric (ME) sensor were systematically considered during the device design in this work. Finite element analysis models of material (magnetic composite), structure (ME heterostructure), and device (BAW ME magnetic sensor) were established and analyzed in COMSOL software. Additionally, the magnetic composite was prepared by radio frequency magnetron sputtering, and its soft magnetism was characterized by magnetic hysteresis loop and surface roughness. The research results demonstrate that after inserting four layers of 5 nm Al₂O₃ films, a performance of 86.7% eddy current loss suppression rate, a less than 1.1% magnetostriction degradation rate, and better soft magnetism were achieved in 600 nm FeGaB. Furthermore, compared with other structures, the two-layer piezomagnetic/piezoelectric heterostructure had a better ME coupling performance. Eventually, the design of the BAW ME magnetic sensor was optimized by the resonance-enhanced ME coupling to match the resonance frequency between the magnetic composite and the BAW resonator. When a 54,500 A/m direct current bias magnetic field was applied, the sensor worked at the first-order resonance frequency and showed good performance. Its linearity was better than 1.30%, the sensitivity was as high as 2.33 μmV/A, and the measurement range covered 0–5000 A/m.

Implantable medical devices have been facing the severe challenge of wireless communication for a long time. Acoustically actuated magnetoelectric (ME) transducer antennas have attracted lots of attention due to their miniaturization, high radiation efficiency and easy integration. Here, we fully demonstrate the possibility of using only one bulk acoustic wave (BAW) actuated ME transducer antenna (BAW ME antenna) for communication by describing the correspondence between the BAW ME antenna and components of the traditional transmitter in detail. Specifically, we first demonstrate that the signal could be modulated by applying a direct current (DC) magnetic bias and exciting different resonance modes of the BAW ME antenna with frequencies ranging from medium frequency (MF) (1.5 MHz) to medium frequency (UHF) (2 GHz). Then, two methods of adjusting the radiation power of the BAW ME antenna are proposed to realize signal amplification, including increasing the input voltage and using higher order resonance. Finally, a method based on electromagnetic (EM) perturbation is presented to simulate the transmission process of the BAW ME antenna via the finite element analysis (FEA) model. The simulation results match the radiation pattern of magnetic dipoles perfectly, which verifies both the model and our purpose.

The conductive magnetic film will produce eddy current loss when it works in a high-frequency band, which will reduce the performance of bulk acoustic wave magnetoelectric (BAW ME) devices. If the eddy current loss is not taken into account in the devices modeling, the models will be seriously distorted. Therefore, combining the Maxwell's equations with constitutive relations of ME material, we define the eddy current loss angle as a figure of merit to evaluate the eddy current loss. Then the models of eddy current loss rate of the potential energy and average radiated power are constructed, respectively. The finite element analysis is used to further validate the analytic model. In addition, the effect of isolation layers on eddy current suppression is studied by using the analytical model. The results show that the analytical solutions match with the numerical simulation results perfectly.

In this letter, a wideband self-decoupling scheme is proposed for MIMO antennas. Based on the mode orthogonal decoupling scheme, when the proposed differential mode antenna is integrated with a loop branch, it will be decoupled at one frequency f ₁ . Moreover, the parasitic branch in the proposed antenna naturally works as a parasitic decoupling element, so it will achieve decoupling at a second frequency f ₂ simultaneously. Two demonstrational examples working in the N79 band (4.4 – 5 GHz) are studied. The results show that the MIMO antennas using the proposed scheme can achieve a wideband isolation greater than 26.4 dB across the whole band with two transmission zeros. Taking into consideration the attractive integration free from differential feeding structures and wideband high isolation, the proposed integrating decoupling scheme may provide a new vision for the MIMO antenna designs.

It brings new design perspectives to study mechanical antenna in the view of circuit rather than the electromagnetic field. In this paper, an equivalent circuit of bulk acoustic wave (BAW) antenna is constructed by using constitutive relation of magnetoelectric composites and Newton’s governing equation. Based on this circuit, series and parallel resonant frequencies of two phases for BAW antenna are simulated in advanced design system (ADS) and magnetoelectric coupling coefficient is calculated. The results show that the electromechanical coupling coefficient is about 6%, the magnetomechanical coupling coefficient is about 86%, and the magnetoelectric coupling coefficient is about 5.2% under the existing material system (AlN and FeGaB). The magnetoelectric voltage gain is derived based on Kirchhoff’s Current Law, which contributes to studying the influence of the two phases thickness ratio on the performance of BAW antenna. The results show that BAW antenna has the optimal energy coupling and conversion when the thickness ratio of the two phases is 1:1. The input and the output impedances of BAW antenna are calculated by T-parameter matrix, which are perfectly matched with the results in ADS simulation. Relevant experiments have been carried out by preparing the magnetoelectric antenna based on PZT and Terfenol-D materials to verify the universality of the model.

A co-linearly polarized wideband microstrip antenna with a single shared patch feeding by two parallel L -probes is proposed in this letter. The shared patch introduces a new coupling path for the L-probes. The coupling coefficients of the two L-probes as well as the L-probe and the patch are quantitatively derived based on the coupled resonators theory. It is proved that by adjusting the geometries and dimensions of the two L-probes and the patch, a natural wideband high isolation can be obtained. A demonstration example is designed and measured to validate the feasibility of the proposed scheme. The results show that the proposed antenna can achieve impedance matching of -10 dB and high isolation of 20 dB in the frequency range from 3.2 to 4 GHz. Besides, the measured efficiency ranges from 91 to 99% with an average realized gain of 7.4 dB. Furthermore, another example with a lower height is also designed to justify the practical usefulness, showing 19.8% decoupling bandwidth.