基于RF MEMS开关的新型双频带功率放大器

RF MEMS开关具有低损耗、低功耗、尺寸小和易于集成等优点而被广泛应用于各种可重构射频电路及系统中。通过分析比较电容并联式和串联式RF MEMS开关两种电路结构的射频性能,设计了一种基于RF MEMS开关的新型功率放大器,使用RF MEMS开关控制匹配网络来实现双工作频带的转换。结果表明,设计的功率放大器在2.35GHz和1.25GHz两个工作频带下,功率附加效率(PAE)和输出功率(Pout)可分别达到72%、67%及40.8、42.7dBm。该功率放大器具有较高的功率附加效率和输出功率,适用于多频带的射频系统,对RF MEMS器件在可重构系统中的应用具有一定参考价值。     

Fabrication of γ-In2Se3/α-In2Se3/rGO homo-heterojunction for efficient photocatalytic hydrogen evolution

In this work, unique γ-In₂Se₃ nanoparticles/α-In₂Se₃ nanosheets (In₂Se₃ NPS) homojunction was prepared to facilitate the transfer and separation of internal carriers, and then reduced graphene oxide (rGO) was introduced to enhance the photocatalytic activity of In₂Se₃ NPS by in-situ solvothermal method. The obtained In₂Se₃ NPS/rGO homo-heterojunctions exhibited 3.25 times higher H₂ evolution rate (4497.24 μmol g⁻¹ h⁻¹) and good stability compared with pristine In₂Se₃ NPS, which was ascribed to efficient separation and migration of photogenerated electron-hole pairs, abundant active sites and reduced overpotential of H₂ evolution over the above homo-heterojunction structure with strong interaction between rGO and In₂Se₃ NPS. This work provides a promising approach and new insight to fabricate homo-heterojunction photocatalyst with an excellent electronic structure toward photocatalytic water splitting.     

High-performing MoS2-embedded Si photodetector

Transition metal dichalcogenides (TMDs) are a new class of materials that replace advanced functional materials like graphene, CNT etc., in photovoltaics and sensors. In the present work, the 2-dimensional tri-layer MoS₂ is applied for high-performing photodetector. Here, the conventional n-doped p-type Si (n-Si/p-Si) was coated with tri-layer MoS₂ film using CVD method. HRTEM reveals the presence of tri-layer with highly ordered lattice planes. Characteristic peaks of Mo and S are obtained in XPS profile. Due to spin-orbit coupling, the 3d band of Mo and 2p band of S are split into two states. Raman spectrum of MoS₂ film shows two peaks, corresponding to its in-plane and out-of-plane vibrational modes. The wave number difference between these modes is measured as 22.97 cm⁻¹, which ensures that there are three layers in MoS₂ film. The splitting of valence band generates multiple excitons which are marked as A and B in the absorption profile. The excitonic transition corresponds to the direct band gap of MoS₂ (ie., 1.9 eV). The prepared MoS₂/n-Si/p-Si photodetector includes two rectifying junctions with considerable built-in potentials. A high rectification ratio was measured as 51.37 to ensure the quality junction formation. The photoresponse ratio of the MoS₂/n-Si/p-Si photodetector was obtained as 58.74 to confirm the quality junction formation between MoS₂ and Si with high detectivity of 5.42 × 10¹⁴ Jones. Moreover, the extremely fast rise and fall times of 33 µs and 30 µs were achieved without any external bias application. The functional use of MoS₂ window design would provide the high potential for the enhanced photoelectric devices, such as photodetectors and solar cells.     

用于激光雷达的双层梳齿驱动MEMS扫描镜

提出了一种新型双层梳齿驱动的大尺寸、大偏转角度、低驱动电压微机电系统(MEMS)扫描镜的设计方法。该扫描镜设计嵌套式内外双层垂直梳齿结构,梳齿间采用静电排斥力驱动,改进后的S型扭转梁有效地降低敏感轴刚度。基于垂直梳齿驱动理论分析,建立了该扫描镜的理论模型,并利用MAXWELL和ANSYS仿真软件进行了其静态、动态分析与验证,研究了该扫描镜的体硅制备工艺。仿真实验结果表明,在110 V的驱动电压扫描下,该双层梳齿驱动下的MEMS扫描镜可以实现最大偏转角±13.46°;此外,结构的谐振频率为1.79 kHz,远低于其他高阶模态,有效地抑制了其他非工作模态的交叉干扰运动,获得良好的工作带宽。     

纳米压电梁谐振式加速度计

在现有的谐振式加速度计中,因具有较小的谐振频率和较低的灵敏度而无法应用于高精度制导和空中姿态微调等方 面。 为此,设计出了一种基于纳米压电梁的谐振式加速度计,采用上下双端音叉谐振器(谐振梁采用直径为 500 nm 的氧化锌) 与中心质量块、左右支撑梁对称分布,实现了低交叉耦合和高灵敏度输出。 分析并建立该加速度计结构的数学模型,在 ANSYS WORKBENCH 仿真平台下对其进行分析,上下谐振器的谐振频率分别为 2. 987 93 和 2. 987 29 MHz,在该谐振频率下,X 方向的 位移要比另外 Y、Z 两个方向高两个数量级以上;在 2 000g 加速度载荷作用下,该加速度计最大应力为 241. 46 MPa;在±10g 的设计 量程内,该结构的灵敏度为 1. 133 11 kHz/ g。 基于 SOI 技术,设计纳米压电梁谐振式加速度计的工艺流程以验证其正确性。     

Microgrid control based on a grid-forming inverter operating as virtual synchronous generator with enhanced dynamic response capability

This paper focuses on improving the dynamic response of autonomous microgrids (MGs) by proposing a grid-forming inverter controlled as a virtual synchronous generator (VSG), in combination with a supercapacitor (SC)-based energy storage system (ESS). By this arrangement, the MG-forming VSG is designed to react only in transitory regimes, the steady-state load being distributed to other MG-supporting inverters spread within the MG. In this way, the MG-forming VSG can maintain its full power reserve capacity for dynamic response. The paper details the control solution for the MG-forming inverter, including the VSG and SC-ESS control. The control method for the MG-supporting inverters that allow achieving the proposed control approach is also described. To prove the concept, the paper includes simulation results and experiments accomplished on a complex laboratory MG system based on three parallel inverters, one being controlled as MG-forming VSG, while the others operating as MG-supporting inverters.     

碳纳米管场效应晶体管设计与应用

碳纳米管具有一些独特的电学性质,在纳米电子学有很好的应用前景。随着纳米技术的发展,新的工艺技术也随之产生。纳米器件的＂由下至上＂制作工艺,是在纳米技术和纳米材料的基础之上发展起来的,在新工艺基础之上,可以利用纳米管、纳米线的性质制作成各种新的电子器件。由于碳纳米管可以和硅在电子电路中扮演同样的角色,随着基于碳纳米管的纳米电路研究的深入发展,电子学将在真正意义上从微电子时代进入纳电子时代。从分析碳纳米管分立场效应晶体管典型结构特点入手,分析阐述了碳纳米管构建的典型纳米逻辑电路结构特征及碳纳米管在柔性纳米集成电路方面的应用。     

多梁凹槽高 g 值加速度计的设计与分析

针对目前航空航天、车辆碰撞分析等领域对高 g 值加速度计的迫切需求,设计了一种新型多梁凹槽压阻式加速度计,该 加速度计利用变截面梁作为敏感梁来放大质量块的等效惯性力,并通过辅助梁与背面凹槽的组合有效提高结构刚度,实现了高 灵敏度输出和良好的频宽特性。 建立了加速度计的力学模型,并通过 ANSYS 有限元软件仿真分析,优化获得了加速度计的结 构和尺寸。 利用敏感梁表面路径,分析总结其应力分布规律,确定压敏电阻位置。 仿真实验结果表明,设计出的该加速度计量 程为 150 000 g,灵敏度为 1. 32 μV/ g,固有频率约为 268 kHz。 最后基于 SOI 技术设计了加速度计的工艺流程。     

Construction of Flexible Piezoceramic Array with Ultrahigh Piezoelectricity via a Hierarchical Design Strategy

The µW-level power density of flexible piezoelectric energy harvesters (FPEHs) restricts their potential in applications related to high-power multifunctional wearable devices. To overcome this challenge, a hierarchical design strategy is proposed by forming porous piezoceramics with an optimum microstructure into an ordered macroscopic array structure to enable the construction of high performance FPEHs. The porous piezoceramic elements allows optimization of the sensing and harvesting Figure of merit, and the array structure causes a high level of effective strain under a mechanical load. The introduction of a network of polymer channels between the piezoceramic array also provides increased device flexibility, thereby allowing the device to attach and conform to the curved contours of the human body. The unique hierarchical piezoceramic array architecture exhibits superior flexibility, a high open circuit voltage (618 V), high short circuit current (188 µA), and ultrahigh power density (19.1 mW cm⁻²). This energy density value surpasses previously reported high-performance FPEHs. The ultrahigh power flexible harvesting can charge a 0.1 F supercapacitor at 2.5 Hz to power high-power electronic devices. Finally, the FPEH is employed in two novel applications related to fracture healing monitoring and self-powered wireless position tracking in extreme environments.     

复杂应力条件下 MEMS 加速度传感器可靠性分析

针对 MEMS 加速度传感器在复杂应力条件下潜在的疲劳失效与断裂失效问题,提出了一种基于全概率公式的可靠性 评估模型,完成了器件在振动环境、冲击环境以及振动-冲击耦合环境下的可靠性建模。 模型包含 Wiener 过程和齐次泊松随机 过程,分别描述器件在振动环境中的疲劳损伤以及器件遭受的随机冲击,进一步考虑了随机冲击的幅值大小对器件退化率的影 响。 通过器件在冲击应力下产生的疲劳损伤突增量,反映多失效模式间的相关性。 对比分析了振动-冲击相互独立与相互耦合 作用的可靠性模型,结果表明,振动-冲击相互耦合作用的可靠性模型评估结果更具有指导意义。