一种X波段三叉H型低电压RF MEMS开关设计北大核心CSCD

针对射频电路系统所需要的低电压,高隔离度,低插入损耗的应用需求,通过对开关正对面积对驱动电压产生的影响进行探究,设计了一款应用于X波段三叉H型的RF MEMS开关。开关具有六条悬臂梁作为支撑,通过增大上极板面积来降低开关的开启电压。分别使用HFSS和COMSOL对开关的射频性能和机械性能进行仿真,开关最终优化后,在8-12 GHz内,插入损耗为0.26~0.57 dB,隔离度大于31.30 dB。在10.1 GHz达到最优值,插入损耗为0.40 dB,隔离度为50.25 dB。开关电压在11V时就能够实现状态转换,开关的响应时间为18μs。此开关可与射频可重构器件结合,应用于新一代射频微波领域。     

一种宽频带RF MEMS开关的设计研究

针对现阶段常用的射频微机电系统(RF MEMS)开关频带窄和稳定性差这个特点,本文提出了一种结型梁RF MEMS开关,该微结构采用了的共面波导线的传输线形式以便于与其他器件串并联,使用结型梁增强了开关的稳定性。首先就RF MEMS开关模型的设计及工作原理进行介绍,然后利用有限元分析软件ANSYS对其驱动电压进行分析,并进一步利用HFSS高频仿真软件,针对结型梁结构的RF MEMS开关进行射频性能的分析优化,得到了在频带宽为45 GHz,在15~60 GHz插入损耗小于0.15dB,隔离度高达52dB的RF MEMS开关,最后验证了其在较高加速度冲击条件下依然具有较高的稳定性,适用于恶劣环境。     

串联RF MEMS开关的结构仿真

RF微机电系统(MEMS)开关“断”状态时的隔离度依赖于其几何结构参数,因而需对其尺寸进行优化设计以获得高的隔离度。利用有限元软件HFSS对串联RFMEMS开关模型进行微波特性分析,系统研究了“断”状态下,MEMS开关的隔离度、回波损耗与其信号线宽度(w)、信号线间距(d)、气隙高度(g)、接触层面积(A)等结构参数的关系。结果表明,较小的w、较大的d、较高的g和较小的A可获得具有较小回波损耗和较大隔离度的MEMS开关。其中信号线间距对微波性能影响最大,是RFMEMS开关结构设计考虑的主要因素。设计了g=3μm,d=60μm,A=80×100μm2,w=100μm一个RFMEMS开关,在5GHz时其回波损耗小于0.2dB,隔离度大于35dB。     

单刀双掷开关在自动增益控制电路中的应用

自动增益控制电路(AGC)是微波接收机中常用的一种电路。为了提高器件使用效率,优化端口驻波匹配,可以使用单刀双掷开关来实现AGC电路。单刀双掷开关采用PIN二极管制作,其插入损耗小、隔离度较高、并且端口驻波较好。该开关采用串并联电路方式,并利用Ansoft公司的Serenade软件对其进行仿真优化,电路基板使用Rogers的RT5880板材。经过实际测试,该AGC电路的工作频率为9.5～10.5GHz,正常支路插损小于4dB,带内平坦度0.5dB,输入输出驻波比小于1.6。     

Wi-Fi/WiMAX双极化阵列天线研究

提出一种应用于Wi-Fi/WiMAX的宽带高增益双极化阵列天线.它由+45°和-45°正交极化的两个天线组成。当频率为2.38~2.72 GHz时,天线的回波损耗大于-10 dB;端口1与端口2之间隔离度大于20 dB;端口1在2.45 GHz时获得最大增益为17.14 dBi,端口2在2.483 GHz时获得最大增益为17.15 dBi.仿真和测试很好相吻合,该双极化天线能满足Wi-Fi/WiMAX通信网络要求.     

基于MEMS开关双频微带缝隙天线的设计

本文设计了一种基于MEMS开关的快速切换频率的双频微带缝隙天线.通过MEMS开关的通断来改变缝隙的尺寸,从而改变电流分布,实现天线谐振频率在2.4GHz和5.8GHz之间的快速切换.分析了MEMS开关状态与天线谐振频率之间的关系.仿真结果显示,当开关断开时,微带缝隙天线的频率为2.4GHz,回波损耗达到-27dB;当开关闭合时,微带天线工作频率切换到5.8 GHz,回波损耗达到-23dB,并通过实测数据验证了仿真结果.     

差分高隔离MIMO天线的设计

本文设计了一种具有差分馈电的高隔离度四端口多输入多输出(MIMO)天线.天线的辐射单元由一个十字型贴片和一个方形环贴片两部分嵌套而成.天线两个贴片分别采用不同的馈电方式,十字型贴片采用微带转探针馈电;方形环贴片采用T型功分器和微带线的差分馈电网络馈电.天线中心频率均为2.42 GHz,带宽均大于45 MHz.为了改善天线的隔离度,在天线的端口之间增加了中和线.仿真结果显示,采用本文的设计方法,天线单元间的隔离度改善了12.1 dB,天线单元间的互耦在天线工作频段内均低于-25.6 dB.     

应用于5G的高隔离双频MIMO天线设计

本文设计了一种适用于5G的n41(2.496 GHz～2.690 GHz), n78(3.300 GHz～3.800 GHz)频段的高隔离双频多输入多输出天线。通过在单极子天线单元上延伸出L型枝节产生新的谐振来实现双频,并将两个结构相同的双频天线单元以对称方式进行放置。通过在两个天线单元之间的接地板上刻蚀一个C型槽来提高天线两端口之间的隔离度,在接地板上加载一个接地枝节进一步改善天线在较高工作频段的隔离度。天线实测结果表明,工作频段分别为2.55 GHz～2.75 GHz(7.5%)和3.28 GHz～3.85 GHz(16.0%),端口之间的隔离度在工作频段内分别大于22 dB, 20 dB。     

基于中和线解耦的小型化MIMO天线设计

本文设计了一种利用中和线技术来提高隔离度的双频MIMO天线.天线单元采用印刷单极天线的形式,两个工作频段分别覆盖WLAN频率2.45 GHz/5.2 GHz/5.8 GHz.低频谐振单元为倒F天线,通过增加短截线,用以产生高频谐振,实现双频工作.在天线之间增加一个悬置的中和线来提高天线端口之间的隔离度.仿真结果表明,天线两个工作频带分别为2.39~2.53 GHz和4.57~6.09 GHz.天线两个端口之间的隔离度,在低频段内,S 21<-19.3 dB,在高频段内,S 21<-24.6 dB,满足移动通信WLAN频段天线的设计要求.     

一种新型腔体式共面波导型微机械射频开关

提出了一种新型的腔体式共面波导型微机械射频开关的结构,可动的金属/电介质的复合膜结构的共面波导既可作射频开关,同时也构成微波信号的传输路径。在普通电阻率(4-8Ω·cm)的硅片上,采用表面微机械加工技术制作出体积大小为:1000μm×600μm×300μm的射频开关,驱动电压为35V,在射频信号频率为50MHz到10GHz的范围内,该开关的插入损耗低于2dB,隔离度高于40dB。     

Design, fabrication, testing and packaging of a silicon micromachined radio frequency microelectromechanical series (RF MEMS) switch

RF characterization and packaging of a single pole single throw (SPST) direct contact microelectromechanical (MEMS) series radio frequency (RF) switch is reported. Precise thickness of the silicon MEMS structure is achieved using a specially developed silicon Deep Reactive Ion Etching (DRIE) thinning process. A stress free release process is employed which ensures a high yield of released microstructures. The design of the device is based on stiffness equations derived from first principles. Displacement of the actuator under applied field is measured to confirm electrostatic pull in, which occurs in the 30–50 V range. The variation of contact resistance with time has been measured and is found to have a power law decay, in agreement with theoretical models. At the bare die level the insertion loss, return loss and the isolation of the switch were measured to be ?0.43 dB, ?25 dB and ?21 dB, respectively at 10 GHz. The devices were packaged in commercially available RF packages and mounted in alumina boards for post package characterization. Due to the presence of bond wires in the signal path of the packaged devices, the RF performance was found to degrade at high frequencies. However, losses were measured to be at acceptable levels up to 2 GHz. Factors contributing to insertion loss at the die and package device levels are discussed in detail with possible solutions.     

应用于无线通信的小型化极化分集天线

给出一种应用于无线通信的极化分集天线.该天线结构简单紧凑,由两个方向垂直的T形天线单元实现线性极化分集.通过在接地板上开L形的槽,实现了天线的小型化,同时提高了两个端口的隔离度.仿真和测量结果表明,所实现的天线工作在2.4 GHz,在两个端口上,回波损耗小于-10 dB的带宽大于30%,两端口隔离度基本在-20 dB以下.测量结果与仿真结果基本吻合.     

一种基于SIFW的小型化宽带带通滤波器

为实现射频系统的小型化,本文设计出一种基于基片集成折叠波导( Substrate integrated folded waveguide,简称SIFW)的小型化宽带带通滤波器,并给出了仿真结果.为了改善带外抑制,滤波器通过交叉耦合,在通带低端引入两个传输零点.为改善通带高端滤波特性,在顶层和底层金属微带上刻蚀互补型开口谐振环(Complementary Split Ring Resonators,简称CSRR).仿真结果表明,所实现的滤波器中心频率在7.1 GHz,相对带宽约为47％,通带内回波损耗优于-15dB,插入损耗小于0.7dB.     

An X band RF MEMS switch based on silicon-on-glass architecture

Communication systems such as those used on satellite platforms demand high performance from individual components that make up the various systems and sub-systems. Switching and routing of RF signals between various modules is a routine and critical operation that determines the overall efficiency of the entire system. In this paper, we present the design and fabrication aspects of a direct contact RF MEMS switch designed to operate in the X band (8–12 GHz) with a target insertion of about 0·5 dB and isolation better than 30 dB. The actuation voltage is expected to be around 50 V. The die size is designed to be 3 mm (H) × 3 mm(W) × 2 mm(H). The switch is built from a low residual stress device layer of a highly conducting (0·005 Ohms-cm) silicon on insulator (SOI) wafer. After subsequent lithographic steps, the wafer is bonded to a Pyrex glass wafer which has been previously patterned with gold transmission lines and pull in electrodes. Being built from a single crystal silicon structure, the mechanical robustness of the actuator is much greater than the those in similar membrane-based devices. A 6 mask fabrication process utilizing Deep Reactive Ion Etching to achieve high aspect ratio stiction free structures was developed and implemented. Devices from the first fabrication run are being analysed in our laboratory.     

Study of scattering parameters of RFMEMS shunt switch with high-K dielectrics

This paper discussed about the effect of using high-k materials on scattering parameters of RFMEMS shunt switch. The effect of variation of dielectric constant (k: 3–70) of the dielectric layer of thickness 0.16 µm was studied first. In the upstate, no noticeable change is observed in insertion loss and return loss due to the variation of dielectric constants. In the down-state, both the isolation and return loss are found to be strongly dependent on the dielectric constants of the dielectric layer. Resonant frequency of the switch is decreasing exponentially with the increasing dielectric constant. In order to get resonant frequency of 35 GHz, optimum dielectric layer thicknesses for each dielectric constant are found by parametric analysis of the switch structure. With the optimum dielectric layer thicknesses, all the isolation and return loss behavior are found to be almost identical. However, now the up-state characteristics of the switch are found to be affected. Thus for Ka band applications, the insulating layer with dielectric constant 20–30, with corresponding layer thickness 0.4–0.6 μm, may be suitable for the RFMEMS switch applications. This will lead to return loss 相似文献   

Active quasi-circulator realisation with gain elements and slow-wave couplers

A microstrip active quasi-circulator is presented using two generic amplifier blocks and two power couplers. The power couplers are parallel-coupled lines with a slow-wave structure in order to improve the isolation between ports of the quasi-circulator. A detailed analytic design procedure is presented for the slow-wave couplers based on the capacitive coupling modelling approach for coupled transmission lines. Experimental results show that the quasi-circulator has an insertion loss between 1 and -2 dB, a return loss better than 11 dB at each of the ports and an isolation better than 20 dB from 1.0 to 3.0 GHz. The input 1 dB compression point is 14 dB m at 2.4 GHz.     

A fully integrated high IP1dB CMOS SPDT switch using stacked transistors for 2.4 GHz TDD transceiver applications

A transmit/receive (T/R) switch is an essential module of every modern time division duplex (TDD) transceiver circuit. A T/R switch with high power handling capacity in CMOS process is difficult to design due to capacitive coupling of radio frequency signals to the substrate. This paper proposes a single-pole-double-throw (SPDT) T/R switch designed in a standard Silterra 130 nm CMOS process for high-power applications like RFID readers. The results reveal that, in 2.4 GHz ISM band, the proposed switch exhibits a very high input P1dB of 39 dBm with insertion loss of only 0.34 dB and isolation of 40 dB in transmit mode but 1.08 dB insertion loss and 30 dB isolation in receive mode. Stacked thick-oxide triple-well transistors, resistive body floating and negative control voltages are used to achieve such lucrative performance. Moreover, the chip size of the designed switch is only 0.034 mm² as bulky inductors and capacitors are avoided. The Monte-Carlo and corner analyses confirm that the performance of the switch is also quite stable and reliable.     

碳纤维增强水泥基复合材料的吸波性能研究

利用弓形反射法(NRL)测试了碳纤维掺量分别为0.2%、0.4%、0.6%、0.8%和1.0%(质量分数)时碳纤维增强水泥基复合材料(CFRC)在低频段4～8GHz和高频段8～18GHz时的反射率,讨论了纤维掺量、频率、反射率之间的关系.结果发现,在纤维掺量相同条件下:低频段时,反射率＜-10dB,CFRC表现出吸波性;高频段且纤维掺量超过0.6%(质量分数)时,反射率＞-10dB,CFRC对电磁波表现出反射性.随着纤维掺量的增加,低频段时反射率先降低、后又有所回升,吸波性由弱变强、又变弱,纤维掺量为0.6%(质量分数)时出现最小反射率-15.0dB;高频段时反射率总体上呈上升趋势,材料对电磁波的反射性越来越强,纤维掺量为0.4%(质量分数)时出现最小反射率-19.4dB.     

Ka波段DMTL移相器用RFMEMS电容式并联开关研制(英文)

本文设计并制作了一种用于Ka波段分布式MEMS传输线(DMTL)移相器的MEMS电容式并联开关.通过理论计算和工程经验,大致定义了开关的结构尺寸.采用HFSS软件建立了开关的三维电磁场模型并优化了关键结构参数.仿真表明:开关在Ka波段插入损耗小于0.15 dB,回波损耗大于15 dB.采用CoventorWare软件进行了开关的机电耦合仿真,得出其驱动电压为2.1 V.为了满足流片单位表面微加工工艺的约束,对开关的设计版图和微加工工艺进行了多轮改进,得到初步的MEMS电容式并联开关工艺样品.单个MEMS开关的动态特性测试结果表明:施加36 V驱动电压时,微桥下拉的高度约为2μm.测得的36 V驱动电压与初始设计的2.1 V有较大的差异,原因在于限于流片单位的工艺约束,临时修改了结构设计,主要变化是增加了微桥的高度以及微桥(即上电极)与下电极之间的初始间距.