Novel Highly Tunable MEMS Capacitors With Flexible Structure and Linear C-V Response

2007 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Seyed Mohammad Hashemi ◽  
Amir Khajepour
Keyword(s):  
Vertical Movement ◽  
Moving Plate ◽  
Rf Systems ◽  
Tunable Capacitors ◽  
High Tunability ◽  
Highly Sensitive ◽  
Capacitance Voltage ◽  
Middle Node ◽  
Low Sensitivity ◽  
Q Factors

MEMS parallel-plate tunable capacitors are widely used in different areas such as tunable filters, resonators and communications (RF) systems for their simple structures, high Q-factors and small sizes. However, these capacitors have relatively low tuning range (50%) and are subjected to highly sensitive and nonlinear capacitance-voltage (C-V) responses. In this paper novel designs are developed which have C-V responses with high linearity and tunability and low sensitivity. The designs use the flexibility of the moving plates. The plate is segmented to provide a controllable flexibility. Segments are connected together at end nodes by torsional springs. Under each node there is a step which limits the vertical movement of that node. An optimization program finds the best set of step heights that provides the highest linearity. Two numerical examples of three-segmented- and six-segmented-plate capacitors verify that the segmentation of moving plate can considerably improve the linearity without decreasing the conventional tunability. A two-segmented-plate capacitor is then designed for standard processes which cannot fabricate steps of different heights. The new design uses a flexible step (spring) under middle node. The simulation of a capacitor with flexible middle step, designed for PolyMUMPs process, demonstrates a C-V response with high tunability and linearity and low sensitivity.

A Novel Highly Tunable Butterfly-Type MEMS Capacitor

2007 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Amir Khajepour ◽  
Seyed Mohammad Hashemi
Keyword(s):  
Electrostatic Force ◽  
Actuation Voltage ◽  
Tunable Capacitor ◽  
Tunable Capacitors ◽  
High Tunability ◽  
Structural Rigidity ◽  
Highly Sensitive ◽  
Capacitance Voltage ◽  
Nodal Displacements ◽  
Q Factors

MEMS parallel-plate tunable capacitors are widely used in different devices such as tunable filters and resonators because of their simple structures, high Q-factors and small sizes. However, these capacitors have low tuning range with nonlinear and highly sensitive capacitance-voltage (C-V) responses. In this paper the development of novel tunable capacitor designs exhibiting highly linear C-V responses, is presented. The designs use segmentation technique to produce lumped flexibility in capacitor’s structure. A numerical model is developed to simulate the behavior of the capacitor. When a actuation voltage is applied, the structural rigidity of the plate produces resistive force which balances the electrostatic force, causes nodal displacements and changes the capacitance. It is shown that by optimizing the shape of segments (from rectangular to trapezoidal) and adding flexible steps located under the segments, a low sensitive linear C-V response could be achieved, while maintaining high tunability. The results of numerical simulation for the capacitors designed for PolyMUMPs process demonstrate that by optimization of the segments shape and structural stiffness a combination of high tunability over 100% and highly linear C-V response is achievable.

Design and Modelling of Novel Linearly Tunable Capacitors

2006 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Amir Khajepour ◽  
Seyed Mohammad Hashemi
Keyword(s):  
High Sensitivity ◽  
Variable Stiffness ◽  
Lower Sensitivity ◽  
High Q ◽  
Tunable Capacitors ◽  
High Tunability ◽  
Capacitance Voltage ◽  
Low Sensitivity ◽  
Q Factors ◽  
Very High

MEMS-based tunable capacitors with electrostatic actuation are well-known for their wide tuning ranges, high Q-factors, fast responses, and small sizes. However, tunable capacitors exhibit very high sensitivity near pull-in voltage which counters the concept of tunability. In this research, two novel designs are presented that improve the high sensitivity in capacitance-voltage (C-V) curve. In the first design, the nonlinear deformation of supporting beams is studied to develop a new nonlinear spring. The variable stiffness coefficients of such springs improve the linearity of the C-V curve, and by delaying the pull-in, the maximum tunability is also increased without using complex geometries. In the second design, an asymmetric non-parallel-plate capacitor is introduced, in which the C-V response has lower sensitivity at high voltages. The design concept can be applied to highly tunable capacitors to improve the sensitivity and maintain high tunability. The numerical results demonstrate low sensitivity and high linearity and tunability for the new designs.

A Novel Linear MEMS Capacitor With Triangular Electrodes and Nonlinear Structural Stiffness

2008 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Seyed Mohammad Hashemi ◽  
Amir Khajepour
Keyword(s):  
Parallel Plate ◽  
Structural Stiffness ◽  
Tunable Capacitors ◽  
Structural Rigidity ◽  
Novel Structure ◽  
Simple Geometry ◽  
Voltage Change ◽  
Highly Sensitive ◽  
Q Factors ◽  
Structural Layer

MEMS parallel-plate tunable capacitors have high Q-factors and fast responses to the actuation and therefore are desired for RF applications. However, conventional designs have low tuning ratios and nonlinear capacitance-voltage (C-V) responses which are highly sensitive to the voltage change near pull-in. In this research, a novel structure for parallel-plate-based capacitors is introduced. The capacitor has electrodes with triangular shape and uneven supporting beams and is equipped with a set of middle beams which increases the structural stiffness of the capacitor as bias voltage increases. Because the asymmetric design alters the parallelness of the plates, the stiffness of each middle beam is added to the system at a different voltage causing a smooth increment in structural stiffness. To analyze the capacitor and optimize the design, an analytical model is developed to solve the coupled electrostatic-structural physics. The results of numerical simulations reveal that if the stiffness coefficients of supporting and middle beams are optimized, a highly linear C-V response is obtained. Moreover, since the structural rigidity is gradually increased with voltage, the sensitivity of the response to the voltage change is also improved and a higher tunability over 150% is achieved. The proposed design has a simple geometry and can be fabricated by a three-structural-layer process such as PolyMUMPs.

scholarly journals Terahertz characterization of two-dimensional low-conductive layers enabled by metal gratings

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Prashanth Gopalan ◽  
Yunshan Wang ◽  
Berardi Sensale-Rodriguez
Keyword(s):  
Optical Transmission ◽  
Terahertz Spectroscopy ◽  
Design Guidelines ◽  
Two Dimensional ◽  
Highly Sensitive ◽  
Transmission Measurements ◽  
Metal Gratings ◽  
Low Sensitivity ◽  
Non Destructive

AbstractWhile terahertz spectroscopy can provide valuable information regarding the charge transport properties in semiconductors, its application for the characterization of low-conductive two-dimensional layers, i.e., σs <  < 1 mS, remains elusive. This is primarily due to the low sensitivity of direct transmission measurements to such small sheet conductivity levels. In this work, we discuss harnessing the extraordinary optical transmission through gratings consisting of metallic stripes to characterize such low-conductive two-dimensional layers. We analyze the geometric tradeoffs in these structures and provide physical insights, ultimately leading to general design guidelines for experiments enabling non-contact, non-destructive, highly sensitive characterization of such layers.

Novel Linearly Tunable MEMS Capacitors With Flexible Moving Electrodes

2008 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Seyed Mohammad Hashemi ◽  
Amir Khajepour
Keyword(s):  
Parallel Plate ◽  
Design Methodology ◽  
Fem Simulation ◽  
Voltage Response ◽  
Parallel Plate Capacitor ◽  
Linear Region ◽  
High Tunability ◽  
Flexible Plates ◽  
Tuning Ratio ◽  
Capacitance Voltage

In conventional MEMS parallel-plate capacitor designs, the moving electrode is commonly modeled as a rigid plate with flexible boundary conditions provided by a set of supporting beams. Such a capacitor generates limited tuning ratio up to 1.5 and its capacitance-voltage response is nonlinear. This paper presents novel designs where the moving electrodes are fixed-edge flexible plates. The plate displacement is selectively limited by a set of rigid steps, located between two electrodes, to generate a smooth and linear response and high tunability. Three different step heights are considered in the design and the linearity of the C-V curve is maximized by modifying the geometry of the plate, and changing the location and order of steps. Since the analytical solution for coupled electrostatic-structural physics in this case does not exist, ANSYS® FEM simulation is performed to obtain the C-V curves and optimize the design. Two designs with different electrode shapes, rectangular and circular, are developed. For rectangular-plate capacitors, tunabilities ranging from 120% to 140% and high linearity are achieved. Circular-plate designs, on the other hand, generate lower tunabilities and an extremely linear region in C-V curves. Design methodology introduced in this research is not limited to proposed geometries and can be extended to different topologies to obtain a combination of high tunability and linearity.

scholarly journals Extraction of Bridge Fundamental Frequencies Utilizing a Smartphone MEMS Accelerometer

Sensors ◽  
2019 ◽  
Vol 19 (14) ◽  
pp. 3143 ◽  
Author(s):  
Ahmed Elhattab ◽  
Nasim Uddin ◽  
Eugene OBrien
Keyword(s):  
Stochastic Resonance ◽  
Wireless Sensing ◽  
Mems Accelerometer ◽  
Fundamental Frequencies ◽  
Acceleration Data ◽  
Highly Sensitive ◽  
Output Noise ◽  
Frequency Independent ◽  
Low Sensitivity ◽  
Traffic Operation

Smartphone MEMS (Micro Electrical Mechanical System) accelerometers have relatively low sensitivity and high output noise density. Therefore, it cannot be directly used to track feeble vibrations such as structural vibrations. This article proposes an effective increase in the sensitivity of the smartphone accelerometer utilizing the stochastic resonance (SR) phenomenon. SR is an approach where, counter-intuitively, feeble signals are amplified rather than overwhelmed by the addition of noise. This study introduces the 2D-frequency independent underdamped pinning stochastic resonance (2D-FI-UPSR) technique, which is a customized SR filter that enables identifying the frequencies of weak signals. To validate the feasibility of the proposed SR filter, an iPhone device is used to collect bridge acceleration data during normal traffic operation and the proposed 2D-FI-UPSR filter is used to process these data. The first four fundamental bridge frequencies are successfully identified from the iPhone data. In parallel to the iPhone, a highly sensitive wireless sensing network consists of 15 accelerometers (Silicon Designs accelerometers SDI-2012) is installed to validate the accuracy of the extracted frequencies. The measurement fidelity of the iPhone device is shown to be consistent with the wireless sensing network data with approximately 1% error in the first three bridge frequencies and 3% error in the fourth frequency.

scholarly journals Novel RF MEMS tunable capacitors

2021 ◽  
Author(s):  
Zewdu Hailu
Keyword(s):  
Residual Stress ◽  
Rf Mems ◽  
Stress Gradient ◽  
Repulsive Force ◽  
Quality Factors ◽  
Comb Drive ◽  
Moving Plate ◽  
Tunable Capacitor ◽  
Tunable Capacitors ◽  
Residual Stress Gradient

Current tunable devices such as filters, impedance matching networks and oscillators have problems that degrade their performance at high microwave frequencies. Tuning ratios and quality factors are the major problems associated with semiconductor based tuning components. This thesis presents the design, fabrication and testing of two novel RF MEMS tunable capacitors. The first tunable capacitor is designed using electrostatic repulsive-force actuators which produce an upward movement of the moving plate of a tunable capacitor. The repulsive-force actuator is free of pull-in effect and capable of reaching large displacement. Gap increasing tunable capacitors with areas of 162μm×220μm and 300μm×302μm are developed using electrostatic repulsive-force actuators. The capacitances are calculated using simulations and maximum tuning ratios of 438.5% and 230% are obtained for a parallel and inclined plate designs, respectively, with capacitance-voltage linearity of 96.28% and 95.14%, respectively, in the presence of RF voltage. The second tunable capacitor is developed using residual stress gradient based vertical comb-drive actuator. Conventional vertical comb-drive actuators need two vertical comb fingers, i.e., one for the fixed and one for the moving comb. MetalMUMPs process provides a 20μm thick nickel layer which is subject to residual stress gradient along its thickness. Using the residual stress gradient two curve-up beams are devised to bend out of plane and upward. A moving plate is connected between the middles of the curve-up beams through supporting springs and is raised above the substrate. The moving fingers are connected to opposite sides of the moving plate. The fixed comb-drive fingers are anchored to the substrate. When a voltage is applied, the moving fingers move down towards the fixed fingers. As a result, the capacitance between the moving fingers and the fixed fingers change. Prototypes are fabricated to verify the working principles of this novel actuator using the MetalMUMPs process. Tunable capacitors based on this actuator are experimentally analyzed. Quality factors of 106.9-162.7 at 0.8GHz and 42.4-51.9 at 1.24GHz are obtained over actuation voltage of 0-100V. An optimal design of the tunable capacitors achieved a tuning ratio of 194.4% at 162.5V with linearity of 97.84%

scholarly journals Xpert MTB/RIF Ultra is highly sensitive for the diagnosis of tuberculosis lymphadenitis in an HIV-endemic setting

2021 ◽  
Author(s):  
Stephanie Minnies ◽  
Byron W.P. Reeve ◽  
Loren Rockman ◽  
Georgina Nyawo ◽  
Charissa C. Naidoo ◽  
...  
Keyword(s):  
Clinical Investigation ◽  
False Negative ◽  
Needle Aspiration ◽  
World Health ◽  
Number Of Patients ◽  
Highly Sensitive ◽  
Specimen Processing ◽  
Increased Sensitivity ◽  
Health Organization ◽  
Low Sensitivity

Background: Tuberculosis lymphadenitis (TBL) is the most common extrapulmonary TB (EPTB) manifestation. Xpert MTB/RIF Ultra (Ultra) is a World Health Organization-endorsed diagnostic test, but performance data for TBL, including on non-invasive specimens, are limited. Methods: Fine needle aspiration biopsies (FNABs) from outpatients (≥18 years) with presumptive TBL (n=135) underwent: 1) routine Xpert (later Ultra once programmatically available), 2) a MGIT 960 culture (if Xpert- or Ultra-negative, or rifampicin-resistant), and 3) study Ultra. Concentrated paired urine underwent Ultra. Primary analyses used a microbiological reference standard (MRS). Results: In a head-to-head comparison (n=92) of FNAB study Ultra and Xpert, Ultra had increased sensitivity [91% (95% confidence interval 79, 98) vs. 72% (57, 84); p=0.016] and decreased specificity [76% (61, 87) vs. 93% (82, 99); p=0.020], and detected patients not on treatment. HIV nor alternative reference standards affected sensitivity and specificity. In patients with both routine and study Ultras, the latter detected more cases [+20% (0, 42); p=0.034] and, further indicative of potential laboratory-based room-for-improvement (e.g., specimen processing optimisation), false-negative study Ultras were more inhibited than true-positives. Study Ultra false-positives had less mycobacterial DNA than true-positives [trace-positive proportions 59% (13/22) vs. 12% (5/51); p<0.001]. “Trace” exclusion or recategorization removed potential benefits offered over Xpert. Urine Ultra had low sensitivity [18% (7, 35)]. Conclusions: Ultra on FNABs is highly sensitive and detects more TBL than Xpert. Patients with FNAB Ultra-positive “trace” results, most of whom will be culture-negative, may require additional clinical investigation. Urine Ultra could reduce the number of patients needing invasive sampling.

Development of a Linearly Tunable Modified Butterfly-Shape MEMS Capacitor

2008 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Seyed Mohammad Hashemi ◽  
Amir Khajepour ◽  
Patricia Nieva
Keyword(s):  
Actuation Voltage ◽  
Insulator Layer ◽  
Plate Electrode ◽  
Electrostatically Actuated ◽  
Monolithically Integrated ◽  
Tunable Capacitors ◽  
Capacitance Voltage ◽  
Rf Devices ◽  
Fixed Electrode ◽  
Structural Layer

This paper presents a novel geometry and modified structural stiffness for electrostatically actuated MEMS tunable capacitors. The design is based on parallel-plate configuration and four triangular plates are put together to form a butterfly shape flexible moving electrode. Each triangle is suspended by three uneven supporting beams. The capacitor is also equipped with extra beams, called here the “middle beams”, located under the triangles’ corners (nodes). An analytical model is developed to solve the governing equations of a triangular-plate electrode with uneven sides and supporting beams, where the stiffness of the middle beams is gradually added to the system as actuation voltage increases. The numerical simulations reveal that each triangle can be individually tuned up to 150% and the capacitance-voltage (C-V) response is broken into small sections due to added middle beams. Using the model developed in this paper and by design optimization, a linear C-V response is obtained, where the tunability in linear region reaches 100%. The simplicity of the proposed design allows the device to be fabricated using a three-structural-layer process such as PolyMUMPs and could therefore be monolithically integrated with other RF devices and ICs. Moreover, adding additional insulator layer on top of the fixed electrode increases the tunability to over 200% displaying a smooth and low sensitive response.

Design and Optimization of a New Highly Linear Tunable MEMS Capacitor

2007 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Amir Khajepour ◽  
Seyed Mohammad Hashemi
Keyword(s):  
Voltage Response ◽  
Design And Optimization ◽  
Tunable Capacitor ◽  
Nonlinear Springs ◽  
High Tunability ◽  
Voltage Curve ◽  
Capacitance Voltage ◽  
Ideal Curve ◽  
Structural Layer ◽  
The Ideal

In this paper, a novel linearly tunable MEMS capacitor with high tunability is introduced. The characteristic air gap-voltage curve for an ideally linear tunable capacitor is studied. This curve is considered as a target for new designs. A three-structural layer process is used to develop the capacitor. The actuation and sense gaps in the three-plate capacitor are selected in such a way that for a voltage interval (between zero and pull-in), the gap-voltage response for sense electrodes becomes similar to the ideal curve. The resulting capacitance-voltage response of the new design demonstrates a combination of high linearity and tunability up to 250%. For processes which have fixed layer thickness and the sense and actuation gaps cannot be optimized, the design is modified by adding nonlinear springs and asymmetric geometry. The results of numerical simulation for a capacitor designed for PolyMUMPs process verify the improvement of linearity and tunability.

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