静电驱动可调微机械电容

利用简单MEMS技术制作了高品质因数的射频可调微机械电容.此电容由静电驱动,利用WYKO NT1100光学表面轮廓仪测量在不同外加直流电压下可变电容的表面轮廓和位移等信息.测试结果表明,电容的吸合电压为13.5V,电容可调比为1.31∶1,在1GHz下品质因数为51.6,电容值为0.79pF.     

一种新偏压结构的BST电容梳状滤波器设计

介绍了一种五阶可调抽头式梳状线滤波器,设计采用共面方式接地,使用Ba0.6Sr0.4TiO3 (BST)铁电薄膜平板电容作为可调部件,并分析了平板电容结构的影响.针对梳状电调滤波器需单阶加压和外接大电阻繁琐的情况,提出利用集成在衬底上的大容量BST电容作为隔离电容,将各阶谐振器的偏压线互连来简化加压过程.运用高频电磁仿真软件HFSS进行验证,设计出的滤波器中心频率可调范围为842～960 MHz(14％),3 dB带宽为9％～10％.     

程控滤波器的设计

以单片机和FPGA为控制核心,设计基于开关电容滤波器的程控滤波器.该滤波器具有高通、低通和带通功能.通带截止频率在1-30 kHz范围内步进可调.增益在0～60 dB范围内步进可调.     

一种宽范围高精度电容倍增器的设计

为了解决在集成电路中难以制作大容量电容器的问题,采用3个差分式数字控制线性可调跨导运算放大器(POTA)和1个接地电容,实现了一个浮地电容倍增器.通过调节POTA的控制字,可实现电容倍增器电容容量的线性调节,当调节范围为1～1 000倍时,误差小于1.4％.经过Cadence的Spectre仿真器仿真,验证了电路的性能.     

可调真空电容拉杆的维护创新

可调真空电容器的拉杆在长时间使用后容易出现上下活动不灵活,甚至卡死.本文研究了可调真空电容器的结构原理,分析了可调真空电容器卡死的原因,有针对性地提出了对可调真空电容器拉杆进行清洁、润滑维护的方法,并设计了专用维护工具.该方法操作简单、节省时间,维护后可使可调真空电容保持转动灵活,甚至挽救卡死的真空电容,延长其使用寿命.     

宽范围可调MEMS集成滤波器的设计与制作

基于MEMS平面螺旋电感和MEMS可调平行板电容设计并制作了一种宽可调范围的集成可调带通滤波器。理论分析并计算了可调滤波器电感和可调电容的取值范围,利用HFSS设计得到各元件结构参数,并使用AnsoftDesigner分析软件对可调滤波器电路进行了模拟仿真。设计得到的可调滤波器中心频率调节范围为400～700MHz,可调率达75%,实现了宽范围可调,3dB相对带宽范围为5%～10%,插入损耗小于5dB,芯片尺寸为20mm×6mm×0.4mm。给出了一套基于MEMS平面工艺的MEMS集成可调滤波器的制作流程,实现了MEMS集成可调滤波器的工艺制作及测试。测试结果表明,获得的可调滤波器实现了通带频率宽范围可调。     

基于Ba_xSr_(1-x)TiO_3薄膜电容的L波段可调滤波器

在蓝宝石基片上使用Ba_xSr_(1-x)TiO_3(BST)铁电薄膜电容作为可调元件制作出一种五阶梳状线可调带通滤波器。通过对BST平行板电容的材料特性(介电常数、损耗和可调率)的提取,其中40 V偏压下的可调率为43.1%,将这些特性运用于可调滤波器的制作。初步的实验结果分析表明,在20V直流偏置电压作用下,滤波器的中心频率从1.19GHz变化到1.31GHz(可调率为10.1%),带内插入损耗为13.5~13.7dB,回波损耗低于12dB。     

一种C波段压控超材料表面

提出了一种C波段透射率可调的压控超材料表面。该超材料表面由加载变容二极管的新型可调超材料单元构成,通过直流偏置电压控制变容二极管的电容值,调节超材料单元的电磁特性。通过仿真并计算超材料单元的散射系数、等效介电常数和等效磁导率,该单元的可调谐振频域为5.2~5.6 GHz。将压控超材料表面与微带天线相结合,超材料表面透射率可改变天线远场辐射方向图,通过其对远场辐射方向图的调节,验证了可调超材料表面的性能。对设计的压控超材料表面加0.5~10 V的直流偏置电压,该超材料表面工作频率为5.4 GHz,其透射率能有效调节20 dB。     

电容加载对频率选择表面传输特性的影响

有源频率选择表面,是指在频率选择表面中加入变容二极管或PIN二极管等有源器件构成的FSS结构,通过有源器件的可调性来实现对FSS性能的控制。文中根据有源器件的电容等效原理,设计了一种方形缝隙FSS结构,研究了电容加载对FSS传输特性的影响。仿真结果表明,加载电容后其谐振频点向低频偏移,带宽减小,且加载电容对FSS传输特性有较好的可控性。     

低相位噪声、宽调谐范围LC压控振荡器设计

基于开关电容和MOS可变电容相结合的电路结构,设计了一种分段线性压控振荡器,很好地解决了相位噪声与调谐范围之间的矛盾.另外,在尾电流源处加入电感电容滤波,进一步降低相位噪声.采用TSMC 0.18(m CMOS工艺,利用Cadence中的SpectreRF对电路进行仿真,当电源电压VDD=1.8V时,其中心频率为1.8GHz,可调频率为1.430～2.134GHz,调谐范围达到37%,在偏离中心频率1MHz处,相位噪声为-131dBc/Hz,静态工作电流为5.2mA.     

Surface micromachined RF MEMS variable capacitor

We used simple microelectromechanical systems (MEMS) technology to fabricate low-voltage-controlled variable capacitors with high-quality factor. The surface profile of the variable capacitor at different values of applied voltage is measured using WYKO NT1100 optical surface profiler. The pull-in voltage of the variable capacitor was below 15 V. The capacitance and quality factor at 1 GHz are 0.792 and 51.6 pF. The pull-in voltage is 13.5 V, the tuning ratio of the capacitor is more than 1.31:1.     

射频MEMS压控电容器

研究了射频 MEMS压控电容器的设计和制造工艺。压控电容器的制作采用了 MEMS制造技术 ,其主要结构为硅衬底上制作金属传输线电极和介质层 ,然后制作金属膜桥作为电容器的另一个电极。通过改变加在金属膜桥与传输线间的电压达到改变电容值的目的。这种压控电容器可以工作于射频和微波波段 ,具有很高的Q值。测试结果如下 :在 1 GHz、0 V时 Q值达到 3 0 0 ,0偏压电容值为 0 .2 1 p F,当加上驱动电压后 Cmax/ Cmin的变比约为 4∶ 1     

Measured CMOS Switched High-Quality Capacitors in a Reconfigurable Matching Network

Switched capacitors are here investigated for use in reconfigurable matching networks, particularly for digital video broadcasting-handheld (DVB-H) frequencies. A 0.13-mum CMOS circuit is evaluated through both simulations and measurements. Source grounded nMOS transistors are used to switch high-quality metal capacitors located above metal layer 8. The quality factor and tuning range depend on frequency, switch voltage, capacitor size, and transistor width. There is a clear tradeoff between quality factor and tuning range, and measurements show quality factors above 50, 100, and 150 at tuning ranges of 3.9, 2.4, and 1.6, respectively. A reconfigurable matching network with the switched capacitors has been realized using external inductors and the measured matching domain for the DVB-H frequency band is shown. The total loss of the network is 1.0 dB, a result of the high-quality switched capacitors. [All rights reserved Elsevier].     

新颖的双间隔RF MEM可变电容的设计与模拟

设计了一种可用于射频(RF)通信系统中的MEM平行板可变电容,采用新颖的双间隔(two-gap)结构、金属铝极板、折叠“Y”形支撑和厚度不均的可动极板。用CoventorWare软件模拟了电容的C-V特性,当控制电压从0变化到10V时,RF信号电容相应从0.37pF增加到5.64pF,变容比约为15.24∶1;用HFSS软件模拟了电容的S11参数,电容的品质因数Q在1.8GHz下约为77.78。     

一种基于MEMS的射频低相位噪声压控振荡器的研制

利用微机械可变电容作为频率调节元件,制备了一种中心频率为2GHz的 LC VCO.微机械可变电容的控制极板与电容极板分离,并采用表面微机械工艺制造,在2GHz时的Q值最高约为38.462.MEMS VCO的测试结果表明,偏离2.007GHz的载波频率100kHz处的单边带相位噪声为-107.5dBc/Hz,输出功率为-13.67dBm.对微机械可变电容引起的机械热噪声以及减小空气压膜阻尼来降低相位噪声的方法进行了讨论,提出了一种优化阻尼孔数目的方法.     

An area-variable MOS varicap and its application in programmable TAP weighting of CCD transversal filters

A new three-terminal MOS varicap is proposed where the terminal capacitors are made voltage variable not by the modulation of depletion width but by changing the area of inversion under the gate. An MOS capacitor realized on silicon with an impurity gradient along the surface provides the control on the area of inversion because the gate threshold voltage is determined by the doping concentration at the surface. The inhomogeneous doping along the surface is implemented making use of the lateral diffusion from a doped oxide surface. Fabrication details of the capacitor compatible with n-channel silicon gate technology are presented. The C-V relationship for the terminal capacitors is simulated by a piecewise model and agreement with measured results is shown. The Area-Variable MOS Varicap (AVMOSV) is used in implementing an electrically programmable CCD filter with variable TAP weighting. Computer simulation shows considerable promise of area-variable capacitors in TAP weight control and transversal filter realization. Preliminary performance characteristics of a programmable CCD filter are presented.     

Optimal Predictive Control of Three-Phase NPC Multilevel Converter for Power Quality Applications

This paper presents the optimal control of the ac currents, the dc voltage regulation, and the dc capacitor voltage balancing in a three-level three-phase neutral point clamped multilevel converter for use in power quality applications as an active power filter. The ac output currents and the dc capacitor voltages are sampled and predicted for the next sampling time using linearized models and considering all the 27 output voltage vectors. A suitable quadratic weighed cost function is used to choose the voltage vector that minimizes the ac current tracking errors, the dc voltage steady-state error, and the input dc capacitor voltage unbalancing. The obtained experimental results show that the output ac currents track their references showing small ripple, a total harmonic distortion (THD) of less than 1%, harmonic contents that are 46 dB below the fundamental, and almost no steady-state error (0.3%). The capacitor voltages are balanced within 0.05%, and the balancing is assured even when redundant vectors are not chosen. Near-perfect capacitor dc voltage balancing is obtained while reducing current harmonic distortion. Some experimental evidence of robustness concerning a parameter variation was also found, with the optimum controller withstanding parameter deviations from $+$100% to $-$50%. Compared to a robust sliding mode controller, the optimal controller can reduce the THD of the ac currents or reduce the switching frequency at the same THD, being a suitable controller for power quality in medium-voltage applications.      

A novel control scheme for the multilevel rectifier/inverter

A novel three-level pulsewidth modulation (PWM) rectifier/inverter is proposed: this single-phase three-level rectifier with power factor correction and current harmonic reduction is proposed to improve power quality. A three-phase three-level neutral point clamped (NPC) inverter is adopted to reduce the harmonic content of the inverter output voltages and currents. In the adopted rectifier, a switching mode rectifier with two AC power switches is adopted to draw a sinusoidal line current in phase with mains voltage. The switching functions of the power switches are based on a look-up table. To achieve a balanced DC-link capacitor voltage, a capacitor voltage compensator is employed. In the NPC inverter, the three-level PWM techniques based on the sine-triangle PWM and space vector modulation are used to reduce the voltage harmonics and to drive an induction motor. The advantages of the adopted th-ree-level rectifier/inverter are (1) the blocking voltage of power devices (T1, T2, S_a1-S_c4) is clamped to half of the DC-link voltage, (2) low conduction loss with low conduction resistance due to low voltage stress, (3) low electromagnetic interference, and (4) low voltage harmonics in the inverter output. Based on the proposed control strategy, the rectifier can draw a high power factor line current and achieve two balance capacitor voltages. The current harmonics generated from the adopted rectifier can meet the international requirements. Finally, the proposed control algorithm is illustrated through experimental results based on the laboratory prototype.     

A novel power converter with voltage-boosting capacitors for afour-phase SRM drive

This paper presents a method of enhancing the performance of a four-phase switched reluctance motor by using capacitors to produce additional supply voltage during the rise and fall periods of motor phase current. The voltage rating of the inverter components increases and extra capacitor/diode combinations are needed. The operation and analysis of a series voltage boost circuit are detailed for different modes of operation with a study of the effect of the boost capacitor voltage on the current waveform. Different voltage boost circuit configurations are compared. The predicted and measured results show that the boost circuit increases both torque and output power and improves the efficiency of the machine, especially at high speeds     

Single-switch parallel power factor correction AC-DC converters with inherent load current feedback

Single-stage power factor correction (PFC) ac-dc converters usually suffer from high bulk capacitor voltage stress and extra switch current stress. Bulk capacitor voltage feedback with a coupled-winding structure can dramatically alleviate the stresses. However, this type of feedback is indirect because the feedback only occurs after the bulk capacitor voltage increases. This paper presents a family of single-switch single-stage parallel PFC ac-dc converters with inherent load current feedback. Unlike the bulk capacitor voltage feedback, which utilizes the decreased duty ratio and the increased bulk capacitor voltage to reduce the input power at light load, the load current feedback can reduce the input power automatically at light load while maintaining an unchanged duty ratio. The proposed converters combine the advantages of simple topology, low bulk capacitor voltage, and no extra current stress across the switch. The concept is verified using an ac-dc converter with universal-line input and 5-V, 60-W output power. The input current harmonics meet IEC1000-3-2 Class D requirements.