Ka波段0/Π MEMS移相器

报道了一种Ka波段实时延MEMS移相器芯片。该移相器基于开关线式移相器设计原理,集成了4个MEMS三端口直接接触式毫米波开关单元,使用共面波导(CPW)传输线,利用阶梯阻抗的方式实现传输线拐角和CPW空气桥结构的传输线阻抗匹配。芯片采用RF MEMS表面牺牲层工艺制作在400μm厚的高阻硅衬底上,面积为1.4 mm×2.8 mm。测试显示,在34~36 GHz频率范围内,相移误差3.2°,插入损耗2 dB,反射损耗小于-15 dB。     

开关线型四位数字MEMS移相器

介绍了一种基于射频微机械串联开关设计的开关线型四位数字微机电系统(M icro-e lectrom echan ica lSystem s以下简称M EM S)移相器。该移相器集成了16个RF M EM S开关,使用了13组四分之一波长传输线和M IM接地耦合电容,有效地使开关的驱动信号和微波信号隔离,串联容性开关设计有效地降低了开关的启动电压。使用低温表面微机械工艺在360μm厚的高阻硅衬底上制作移相器,芯片尺寸4.8 mm×7.8 mm。移相器样品在片测试结果表明,频点10.1 GH z,22.5°相移位的相移误差为±0.4,°插损2.8 dB;45°位的相移误差为±1.1,°插损2.0 dB;在X波段,对16个相移态的测试结果表明,移相器的插入损耗小于4.0 dB,驻波比小于2.4,开关驱动电压为17~20 V。     

A compact low-loss reconfigurable monolithic low-pass filter using multiple-contact MEMS switches

A high-performance reconfigurable low-pass filter based on the quasifractal self-similar structures has been developed at millimeter-waves using multiple-contact MEMS switches. Three-cell cascaded low-pass structure was reconfigured to one-cell low-pass counterpart by activating the micromachined switches to achieve 3:1 frequency scaling. Two types of special multiple-contact MEMS switches were developed to reduce the number of switching elements as well as to reduce the insertion loss and, thus, extend the operating frequencies to mm-waves. In addition, bias-decoupling circuits were eliminated, resulting in a small chip size of 1.2 mm /spl times/ 1.5 mm. The measured 3-dB cut-off frequency of the reconfigurable low-pass filter changed from 67 GHz to 28 GHz with minor change in the insertion loss from 0.32 dB to 0.27 dB. This work demonstrates the possibility of high-performance compact-size reconfigurable filters at mm-waves using multiple-contact micromachined switches.     

A low-loss single-pole six-throw switch based on compact RF MEMS switches

A low-loss single-pole six-throw (SP6T) switch using very compact metal-contact RF microelectromechanical system (MEMS) series switches is presented. The metal-contact MEMS switch has an extremely compact active area of 0.4 mm /spl times/ 0.3 mm, thus permitting the formation of an SP6T MEMS switch into the RF switch with a total area of 1 mm/sup 2/. The MEMS switch shows an effective spring constant of 746 N/m and an actuation time of 8.0 /spl mu/s. It has an isolation loss from -64.4 to -30.6dB and an insertion loss of 0.08-0.19 dB at 0.5-20 GHz. Furthermore, in order to evaluate RF performances of the SP6T MEMS switch, as well as those of the single-pole single-throw RF MEMS series switch, we have performed small-signal modeling based on a parameter-extraction method. Accurate agreement between the measured and modeled RF performances demonstrates the validity of the small-signal model. The SP6T switch performed well with an isolation loss from -62.4 to -39.1dB and an insertion loss of 0.19-0.70 dB from dc to 6 GHz between the input port and each output port.     

Compact single-pole six-throw switch using centre-anchor MEMS switches

A single-pole six-throw switch based on centre-anchor MEMS switches is presented. It has a chip size of 1 mm/sup 2/ and shows isolation of -48 dB and insertion loss of -0.5 dB between P1 and P4 at 6 GHz. Also, to evaluate the RF performance, the SP6T switch has been modelled using a structure-based /spl pi/ small-signal model.     

基于SP4T开关的4位MEMS开关线式移相器设计

设计了一款4位MEMS开关线式移相器,由SP4TMEMS开关和微带传输线构成,工作于X波段。单刀四掷(single pole 4throw,SP4T)开关用于切换两条不同电长度的信号通道,即参考相位通道和延迟相位通道。每个SP4T开关包含4个悬臂梁接触式RF MEMS串联开关。介绍了4位MEMS开关线式移相器的总体设计,并给出了其关键部件SP4T开关和相位延迟线的设计细节。采用ADS软件仿真分析了器件的电气性能。仿真分析得到:SP4T开关在中心频率10GHz处的回波损耗为-36dB,插入损耗约为0.18dB;移相器各相位的回波损耗均低于-15dB,插入损耗为-0.8～-0.4dB。这种射频MEMS移相器具有小型化、低功耗和高隔离度的优点。     

W-band CPW RF MEMS circuits on quartz substrates

This paper presents W-band coplanar waveguide RF microelectromechanical system (MEMS) capacitive shunt switches with very low insertion loss (-0.2 to -0.5 dB) and high-isolation (/spl les/ -30 dB) over the entire W-band frequency range. It is shown that full-wave electromagnetic modeling using Sonnet can predict the performance of RF MEMS switches up to 120 GHz. Also presented are W-band 0/spl deg//90/spl deg/ and 0/spl deg//180/spl deg/ switched-line phase shifters with very good insertion loss (1.75 dB/bit at 90 GHz) and a wide bandwidth of operation (75-100 GHz). These circuits are the first demonstration of RF MEMS digital-type phase shifters at W-band frequencies and they outperform their solid-state counterparts by a large margin.     

Design and performance of a Ka-band monolithic phase shifterutilizing nonresonant FET switches

This paper describes design consideration and performance of a Ka-band monolithic phase shifter utilizing nonresonant FET switches. The switches show broad-band on/off characteristics up to 60 GHz without using inductors; thus, robust circuit design is possible for a switched-line phase shifter. To determine circuit topology, we introduce a schematic design approach. As a result, desired phase shift as well as good matching characteristics can be realized. The developed 4-bit monolithic phase shifter demonstrates an overall phase deviation less than 5° rms and an insertion loss variation less than 0.65 dB rms from 33 to 35 GHz. For all 16 states, the insertion loss is measured to be 13.1±1.1 dB and the VSWR is less than 1.6. The chip size of the monolithic phase shifter is 2.5 mm×2.2 mm     

A 25–75-MHz RF MEMS Tunable Filter

This paper presents a state-of-the-art discrete RF microelectromechanical systems (MEMS) tunable filter designed for 25-75-MHz operation. This paper also presents an enhanced model of the RF MEMS switch, which is used for accurate prediction of the tunable filter response. The two-pole lumped-element filter is based on digital capacitor banks with on-chip metal-contact RF MEMS switches and lumped inductors, and results in a tuning range of 3:1 with fine frequency resolution, and a return loss better than 13 dB for the entire tuning range. The relative bandwidth of the filter is 4 plusmn 1% over the tuning range and the insertion loss is 3-5 dB, limited mostly by the inductor Q and the switch loss. The IIP₃ measurements prove that tunable filters with metal-contact series RF MEMS switches show extremely linear behavior (IIP₃ > 68 dBm).     

Phase-noise analysis of MEMS-based circuits and phase shifters

The effect of Brownian, acceleration, acoustic, and power-supply noise on MEMS based circuits has been calculated for MEMS.-based circuits (phase shifters, delay circuits). The calculations are done for capacitive shunt MEMS switches and metal-to-metal contact series MEMS switches. It is found that these effects result in both an amplitude and phase noise, with the phase noise being around 100× larger than the amplitude noise. The phase noise due to Brownian motion is negligible for MEMS switches with k ≃ 1.0 N/m, g₀ > 2 μm, Q > 0.5, and f₀ ≃ 50 kHz. The effect of acceleration and acoustic noise is negligible for a total acceleration noise of 10 g or less and a total acoustic noise of 74-dB sound pressure level. The power-supply noise depends on the bias conditions of the MEMS element, but is negligible for MEMS switches with a bias voltage of 0 V and a total noise voltage of 0.1 V or less. It is also found that metal-to-metal contact series switches result in much less phase noise than standard capacitive shunt switches. The phase noise increases rapidly for low spring-constant bridges (k = 0.24 N/m), low-height bridges, and bridges with a large mechanical damping (Q < 0.3). Also, varactor-based designs result in 30-40 dB more phase noise than switch-based circuits. This paper proves that microwave passive circuits built using MEMS switches (with a proper mechanical design) can be used in most commercial and military applications without any phase-noise penalty     

Miniature and tunable millimeter-wave lowpass filter with MEMS switch

In this paper, fully monolithic tunable millimeter-wave filters with tapped-line feedings are proposed using the CPW-based periodic structures with novel multiple-contact MEMS switches. Millimeter-wave low-pass filters were designed, fabricated, and tested. The cascaded CPW-based periodic structures, with low-pass intrinsic filtering characteristics, are reconfigured into a self-similar single unit cell by the operation of the novel multiple-contact MEMS switches with single actuation. The measured results of the reconfigurable low-pass filter show the 3-dB cutoff frequency change from 19 to 11 GHz with very small change in the average insertion loss from 1.3 to 1.9 dB. The chip size of the low-pass is 4.0 mm × 1.6 mm.     

Ka波段分布式MEMS移相器低驱动电平容性开关的机电设计

为降低Ka波段分布式MEMS移相器容性开关的驱动电压,提出不同形状新型低弹性系数铰链梁结构MEMS电容开关的机电设计概念.采用Intelli SuiteTM和ADS软件分析了三种梁结构MEMS电容开关的位移分布、驱动电压、机械振动模式和射频性能等参数,结果表明:所设计新型beam2结构MEMS电容开关具有优越的机电特性和射频特性,即开关的驱动电压为3V,机械振动模式固有频率都大于31kHz,在35GHz处插入损耗和回波损耗分别为0.082dB和18.6dB,而相移量可达到105.9o.     

X-波段MEMS单刀双掷开关的研究

利用X-波段MEMS单刀单掷膜开关和成熟的微带线技术设计了一种X-波段MEMS单刀双掷膜开关,其模拟结果为;阈值电压为19V左右,工作频率为8～12GHz,在中心频率（10GHz）处,导通开关的插入损耗为-0．2dB,截止开关的隔离度为-21dB,开关的回波损耗为-43dB。     

High-isolation CPW MEMS shunt switches. 1. Modeling

This paper, the first of two parts, presents an electromagnetic model for membrane microelectromechanical systems (MEMS) shunt switches for microwave/millimeter-wave applications. The up-state capacitance can be accurately modeled using three-dimensional static solvers, and full-wave solvers are used to predict the current distribution and inductance of the switch. The loss in the up-state position is equivalent to the coplanar waveguide line loss and is 0.01-0.02 dB at 10-30 GHz for a 2-μm-thick Au MEMS shunt switch. It is seen that the capacitance, inductance, and series resistance can be accurately extracted from DC-40 GHz S-parameter measurements. It is also shown that dramatic increase in the down-state isolation (20⁺ dB) can be achieved with the choice of the correct LC series resonant frequency of the switch. In part 2 of this paper, the equivalent capacitor-inductor-resistor model is used in the design of tuned high isolation switches at 10 and 30 GHz     

RF MEMS开关的设计分析

针对具有低损耗、高隔离度性能的微机电系统(Micro-Electro-Mechanical System,MEMS)开关,介绍了串联DC式和并联电容式的开关结构模型,并对并联电容式MEMS开关的工作原理、等效电路模型和制造工艺流程进行了描述,利用其模型研究了开关的微波传输性能,设计了一款电容耦合式开关并进行了仿真。由仿真结果可得,开关"开态"时的插入损耗在40 GHz以内优于-0.3 dB;开关"关态"时的隔离度在20～40 GHz相对较宽的频带内优于-20 dB。     

基于微机电系统开关的四位移相器设计

为了解决相控阵雷达小型化和低损耗的问题,设计了一个工作频率为2.2 GHz的射频微机电系统(MEMS)四位开关线型移相器。首先分析了直接接触式MEMS串联开关的插入损耗和隔离度,并得到仿真结果。在此基础上设计了基于该开关的移相范围为0~180o的四位移相器电路,相移量为12o每步。采用HFSS软件对其进行仿真,得到移相精确度、插入损耗和隔离度等关键结果,移相器工作在2.2 GHz时,隔离度大于20 dB,插入损耗小于1 dB。该设计与传统移相器相比体积更小,且具有更小的插入损耗和更大的隔离度。     

Distributed 2- and 3-bit W-band MEMS phase shifters on glass substrates

This paper presents state-of-the-art RF microelectromechanical (MEMS) phase shifters at 75-110 GHz based on the distributed microelectromechanical transmission-line (DMTL) concept. A 3-bit DMTL phase shifter, fabricated on a glass substrate using MEMS switches and coplanar-waveguide lines, results in an average loss of 2.7 dB at 78 GHz (0.9 dB/bit). The measured figure-of-merit performance is 93/spl deg//dB-100/spl deg//dB (equivalent to 0.9 dB/bit) of loss at 75-110 GHz. The associated phase error is /spl plusmn/3/spl deg/ (rms phase error is 1.56/spl deg/) and the reflection loss is below -10 dB over all eight states. A 2-bit phase shifter is also demonstrated with comparable performance to the 3-bit design. It is seen that the phase shifter can be accurately modeled using a combination of full-wave electromagnetic and microwave circuit analysis, thereby making the design quite easy up to 110 GHz. These results represent the best phase-shifter performance to date using any technology at W-band frequencies. Careful analysis indicates that the 75-110-GHz figure-of-merit performance becomes 150/spl deg//dB-200/spl deg//dB, and the 3-bit average insertion loss improves to 1.8-2.1 dB if the phase shifter is fabricated on quartz substrates.     

基于RF MEMS开关的交指型可切换带通滤波器设计

为了有效解决信号/频谱分析仪等微波测试仪器尺寸较大、信号损耗高、选通切换效率差等问题,将射频MEMS开关引入交指型可切换滤波器结构中。通过MEMS四掷开关选择具有不同中心频率的交指型谐振器,实现在6~14 GHz内四个频率的射频信号切换过滤。利用HFSS电磁波仿真软件对滤波结构的几何参数进行优化计算,得到四个可切换频率的插入损耗,分别为1.26 dB@6.86 GHz、1.03 dB@9.16 GHz、1.23dB@11.78 GHz、1.07 dB@12.26 GHz,整体面积约为7.95 mm³。与其他可切换滤波器相比,该可切换滤波器将MEMS四掷开关与交指型谐振器集成到一起,具有低插损、小尺寸、高集成度等优点。     

A 2-bit miniature X-band MEMS phase shifter

The design and performance of a compact low-loss X-band true-time-delay (TTD) MEMS phase shifter fabricated on 8-mil GaAs substrate is described. A semi-lumped approach using microstrip transmission lines and metal-insulator-metal (MIM) capacitors is employed for the delay lines in order to both reduce circuit size as well as avoid the high insertion loss found in typical miniaturized designs. The 2-bit phase shifter achieved an average insertion loss of -0.70 dB at 9.45 GHz, and an associated phase accuracy of /spl plusmn/1.3/spl deg/. It occupies an area of only 5 mm/sup 2/, which is 44% the area of the smallest known X-band MEMS phase shifter . The phase shifter operates over 6-14 GHz with a return loss of better than -14 dB.     

A DC to 10-GHz 6-b RF MEMS time delay circuit

A 6-b radio frequency (RF) microelectromechanical system (MEMS) time-delay circuit operating from dc to 10 GHz with 393.75-ps total time delay is presented. The circuit is fabricated on 250-/spl mu/m-thick alumina and uses metal contacting RF MEMS switches to realize series-shunt SP4T switching networks. The circuit demonstrates 1.8+/-0.6 dB of loss at 10 GHz and has linear phase response across the entire band with accuracy of better than a least significant bit for most states.