沉积条件对室温下磁控溅射AZO薄膜微结构与光电性能的影响

通过控制室温下射频磁控溅射过程中不同的氩气工作气压、溅射功率和沉积时间,在石英玻璃上沉积Al掺杂ZnO（AZO）薄膜,探究了三种工艺条件对制备的AZO薄膜的微结构及光电性能的影响。所制备的AZO薄膜经500℃退火后均为六方纤锌矿结构,具有优异的透明度,在可见光范围内的平均透过率均在86%以上。在气压0.25 Pa、功率200 W下,溅射时间为10 min时,薄膜的电阻率低至5.04×10^-3Ω·cm,而溅射时间为15 min时,Haacke性能指数最优,为0.314×10^-3Ω^-1。结果表明,磁控溅射制备的AZO薄膜的晶体结构、方阻和透过率等特性与制备过程中的气压、功率和时间密切相关,通过评价性能指数可指导优化AZO薄膜的制备工艺。     

基于GaAs HBT工艺的高增益宽带Doherty功率放大器设计

在传统Doherty功率放大器的基础上,采用砷化镓(GaAs)异质结双极晶体管(HBT)工艺,设计了一款可应用于5G通信N79频段(4.4~5 GHz)的高回退效率MMIC Doherty功率放大器(DPA)。通过在Doherty电路中采用共射-共基结构,并在共射-共基结构中加入共基极接地电容,大幅提升了DPA的增益和输出功率。使用集总元件参与匹配,减小了芯片的面积。仿真结果表明,在目标频段内,增益大于28 dB,饱和输出功率约为38 dBm,饱和附加效率(PAE)为63%,7 dB回退处的效率达到43%。     

基于MEC和K-means聚类的天馈智能优化系统及方法设计

当前宏站天馈调整问题较多。一是天馈方位角不合理,未能覆盖周边最有价值区域;二是用户分布存在潮汐效应,天馈未能与用户转移进行联动;三是天馈调整更多依赖于现场勘查和优化人员经验,方案不够精确;四是不合理天馈需人力调整,费时费力。本文设计了一种基于MEC和K-means聚类的天馈智能优化系统及方法,对站点周边用户分布通过大数据分析进行精准评估,结合天线自动调整组件在周期T内实现天馈自动调整,提升覆盖率的同时最大限度地激发流量。     

Influence of growth conditions of oxide on electrical properties of AlGaN/GaN metal–insulator–semiconductor transistors

AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors(MIS-HEMTs) on a silicon substrate were fabricated with silicon oxide as a gate dielectric by sputtering deposition and electron-beam(EB) evaporation. It was found that the oxide deposition method and conditions have great influences on the electrical properties of HEMTs. The low sputtering temperature or oxygen introduction at higher temperature results in a positive equivalent charge density at the oxide/AlGaN interface(Nequ), which induces a negative shift of threshold voltage and an increase in both sheet electron density(ns) and drain current density(ID). Contrarily, EB deposition makes a negative Nequ, resulting in reduced ns and ID. Besides, the maximum transconductance(gm-max) decreases and the off-state gate current density(I_G-off) increases for oxides at lower sputtering temperature compared with that at higher temperature, possibly due to a more serious sputter-induced damage and much larger Nequ at lower sputtering temperature. At high sputtering temperature, I_G-off decreases by two orders of magnitude compared to that without oxygen, which indicates that oxygen introduction and partial pressure depression of argon decreases the sputter-induced damage significantly. I_G-off for EB-evaporated samples is lower by orders of magnitude than that of sputtered ones, possibly attributed to the lower damage of EB evaporation to the barrier layer surface.     

Direct digital-to-RF converter employing semi-digital FIR voltage-mode RF DAC

A direct digital-to-RF converter (DRFC) is presented in this work. Due to its digital-in-nature design, the DRFC benefits from technology scaling and can be monolithically integrated into advance digital VLSI systems. A fourth-order single-bit quantizer bandpass digital ΣΔ modulator is used preceding the DRFC, resulting in a high in-band signal-to-noise ratio (SNR). The out-of-band spectrally-shaped quantization noise is attenuated by an embedded semi-digital FIR filter (SDFIR). The RF output frequencies are synthesized by a novel configurable voltage-mode RF DAC solution with a high linearity performance. The configurable RF DAC is directly synthesizing RF signals up to 10 GHz in first or second Nyquist zone. The proposed DRFC is designed in 22 nm FDSOI CMOS process and with the aid of Monte-Carlo simulation, shows 78.6 dBc and 63.2 dBc worse case third intermodulation distortion (IM3) under process mismatch in 2.5 GHz and 7.5 GHz output frequency respectively.     

射频溅射功率对非晶Zn-Sn-O薄膜性能的影响

使用射频磁控溅射法,基于不同溅射功率(58、79、116、148和171W)条件在玻璃基底上室温制备了Zn-Sn-O(ZTO)薄膜,并探讨了溅射功率对薄膜的结构、电学性能和光学性能的影响。结果表明,提高溅射功率有助于提升薄膜的沉积速率;XRD分析表明不同溅射功率条件下制备的ZTO薄膜均具备稳定的非晶结构;随着溅射功率的增加,薄膜的电阻率下降,光学吸收边“红移”(光学禁带宽度从3.77eV减小到3.62eV);整体来看,在58~148W溅射功率范围内制备的ZTO薄膜具备较好的可见光透明性,其在380~780nm可见光范围内的平均透过率均超过85%。     

射频/微波能量收集系统的整流电路研究进展

射频/微波能量收集系统以可持续、环保等优点在无线传感器网络、可穿戴设备等领域具有广泛应用前景。对近年来射频/微波能量收集系统的整流电路的研究进展进行了概述。分析并讨论了整流电路的技术指标和电路结构,分别从器件研究和电路设计两个方面对整流电路的研究进展进行分析、归纳。从原理、性能提升等方面分析具有低的零偏压电阻值的自旋二极管应用于微瓦量级信号整流电路的潜力;从微弱信号整流、宽输入功率范围信号整流、高功率转换效率整流、阻抗去敏感化4个方面分析了整流电路设计的关键问题,归纳出有效的解决途径并对整流电路的发展趋势进行了展望。     

蓝宝石衬底上槽栅型X波段增强型AlGaN/GaN HEMT

研制了一款X波段增强型AlGaN/GaN高电子迁移率晶体管(HEMT)。在3英寸(1英寸=2.54 cm)蓝宝石衬底上采用低损伤栅凹槽刻蚀技术制备了栅长为0.3μm的增强型AlGaN/GaN HEMT。所制备的增强型器件的阈值电压为0.42 V,最大跨导为401 mS/mm,导通电阻为2.7Ω·mm。器件的电流增益截止频率和最高振荡频率分别为36.1和65.2 GHz。在10 GHz下进行微波测试,增强型AlGaN/GaN HEMT的最大输出功率密度达到5.76 W/mm,最大功率附加效率为49.1%。在同一材料上制备的耗尽型器件最大输出功率密度和最大功率附加效率分别为6.16 W/mm和50.2%。增强型器件的射频特性可与在同一晶圆上制备的耗尽型器件相比拟。     

一种低关断功耗的地端关断整流器

基于TSMC 180 nm CMOS工艺,设计了一种采用负压关断的地端关断整流器。将关断时的控制电平从0降到负值,降低了使能管的亚阈值电流。将使能管的工作状态从亚阈值区变为截止区,进一步降低了关断功耗。仿真结果表明,当整流器使能时,该负压地端关断整流器的导通性能与传统地端关断整流器几乎相当。当整流器关断且输入电压幅值为1 V时,关断功耗为-24.0 dBm @953 MHz,与传统地端关断整流器相比,下降了7.5 dBm;与传统短路关断整流器相比,降低了23 dBm,功率转换效率提高了1.9 %。该地端关断整流器能满足射频能量收集系统中整流器低功耗待机的要求。     

舰载综合射频系统探测资源分配方法

从未来信息化海上联合作战对舰载综合射频系统需求出发,在分析系统探测资源分配问题特征的基础上,明确资源分配基本思路,提出资源分配基本规则。在建立任务目标威胁判定评估模型和多传感器协同探测效能指数方程的基础上,构建以系统探测效能指数最优化为目标的资源分配模型,解决在战场态势突变情况下的舰载综合射频系统探测资源分配决策问题。实例仿真表明:该方法能够应对复杂战场环境态势变化,在方案调整迅速、资源分配实时、探测目标连续 方面,满足实战需求。