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Journal ArticleDOI

Analytical evaluation of the interdigital electrodes capacitance for a multi-layered structure

01 May 2004-Sensors and Actuators A-physical (Elsevier)-Vol. 112, Iss: 2, pp 291-301
TL;DR: In this article, the capacitance between the two comb electrodes of a periodic interdigital capacitive sensor, based on conformal mapping techniques, is analyzed for any space and finger width as well as for any number of layers with different thickness and permittivity.
Abstract: The widespread use of interdigital electrodes in such applications as microwave filters, surface acoustic wave devices, electro-optic shutters as well as on chemical and biological sensing and even on the electrical and dielectric characterization of materials requires that we improve our description of their electrical performance. In this paper, we present new analytical expressions for the capacitance between the two comb electrodes of a periodic interdigital capacitive sensor, based on conformal mapping techniques. This proposed model is general and quite independent of the particular application and can be applied for any space and finger width as well as for any number of layers with different thickness and permittivity. The capacitance for a particular sensor configuration is a function of the dielectric permittivity of the materials, the fingers length and of two geometric non-dimensional parameters: (i) the ratio between the space and finger widths; (ii) the ratio between the thickness of the sensitive layer and the spatial sensor wavelength. Comparisons with previously published models as well as with experimental data and finite element analysis were made.
Citations
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Patent
Zoran Radivojevic1, Paul Beecher1, Chris Bower1, Piers Andrew1, Darryl Cotton1, Samiul Haque1 
16 Aug 2012
TL;DR: In this paper, an apparatus including a plurality of adjacent repeated base units, each base unit formed from an active electrode of first, second, third and third touch sensor arrays, each including an active electrodes connected to a respective common terminal of the touch sensor array, where a swipe touch gesture applied to two or more adjacent active electrodes of the apparatus generates signalling at the respective common terminals of the corresponding touch sensors.
Abstract: An apparatus including a plurality of adjacent repeated base units, each base unit formed from an active electrode of first, second and third touch sensor arrays, the first, second and third touch sensor arrays each including a plurality of active electrodes connected to a respective common terminal of the touch sensor array, wherein each base unit includes an active electrode of the second touch sensor array interlaced between an active electrode of the first touch sensor array and an active electrode of the third touch sensor array such that a swipe touch gesture applied to two or more adjacent active electrodes of the apparatus generates signalling at the respective common terminals of the corresponding touch sensor arrays which allows the direction of the swipe touch gesture to be determined.

383 citations

Journal ArticleDOI
TL;DR: An overview of the status and challenges in the LC passive wireless sensor toward a wireless sensing platform is provided and recent efforts to increase the interrogation distance and to extend the measurement of single parameter to multiple parameters are finally outlined.
Abstract: Inductor–capacitor ( $LC$ ) passive wireless sensors use a transformer with loose coupling between an external readout coil and an inductor that receives power through this inductive coupling. Changes in the sensor are wirelessly and remotely detected by the readout coil, which makes them highly useful in applications that require the sensor to be powered remotely and to occupy a small volume, such as harsh and sealed environments, where physical access to the sensor is difficult. Although the sensor to accomplish this function dates from the 1960’s, its rapid extension over the past decades has benefited from microelectromechanical systems. This paper provides an overview of the status and challenges in the $LC$ passive wireless sensor toward a wireless sensing platform. The basic sensing principles are first categorized into detecting changes of the sensor in response to the capacitance, resistance, inductance, or coupling distance due to the parameter of interest through monitoring the impedance magnitude and phase spectrum. The present state of the art in sensor applications for pressure, strain, temperature, humidity, biochemical, gas, and so on is then reviewed and compared. For emerging applications from many Internet of Things scenarios, geometrical constraints, such as small and non-invasive coils, reduce the magnetic coupling between the sensor and the readout coil, resulting in a limited interrogation distance. Furthermore, an increasing number of applications also require the simultaneous measurement of multiple parameters. Recent efforts to increase the interrogation distance and to extend the measurement of single parameter to multiple parameters are finally outlined. [2016-0093]

176 citations


Cites background from "Analytical evaluation of the interd..."

  • ...2 (b), the total capacitance is written as [15]...

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Journal ArticleDOI
TL;DR: In this article, the sensing mechanism, design issues, performance evaluation and applications for planar capacitive sensors are presented in the context of characterisation and imaging of a dielectric material under test (MUT), a systematic study of sensor modelling, features and design issues is needed.
Abstract: Purpose – The purpose of this paper is to present the sensing mechanism, design issues, performance evaluation and applications for planar capacitive sensors. In the context of characterisation and imaging of a dielectric material under test (MUT), a systematic study of sensor modelling, features and design issues is needed. In addition, the influencing factors on sensitivity distribution, and the effect of conductivity on sensor performance need to be further studied for planar capacitive sensors.Design/methodology/approach – While analytical methods can provide accurate solutions to sensors of simple geometries, numerical modelling is preferred to obtain sensor response to different design parameters and properties of MUT, and to derive the sensitivity distributions of various electrode designs. Several important parameters have been used to evaluate the response of the sensors in different sensing modes. The designs of different planar capacitive sensor arrays are presented and experimentally evaluated...

172 citations


Cites methods from "Analytical evaluation of the interd..."

  • ...For NDT and material characterisation, Igreja and Dias (2004) studied the design issues for an inter-digital sensor using an analytical method....

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Journal ArticleDOI
TL;DR: In this paper, a capacitive humidity sensor has been fabricated on polymeric foil PET using all additive processes, including inkjet printing and electrodeposition of interdigitated structures followed by the printing of a test humidity sensing layer.
Abstract: Functional humidity sensors have been fabricated on polymeric foil PET using all additive processes. The fabrication included inkjet printing and electrodeposition of interdigitated structures followed by the inkjet printing of a test humidity sensing layer. Quantitative and qualitative analysis of the sensor operation led to the understanding and subsequent improvement of the sensor performances by means of the differential measurements method. To the best of our knowledge, it is the first time that electrodeposition of a thicker metallic layer on inkjet printed patterns has shown advantages in the stability and sensitivity of a capacitive humidity sensor. The process exposed in this paper is proposed as a perfect candidate for the fabrication of sensors arrays or disposable sensing platforms where low-cost, light weight and mechanical flexibility are important issues.

149 citations

Journal ArticleDOI
TL;DR: The innovative wireless strain sensing technology described herein has demonstrated a great potential to extend its applications in structural health monitoring, damage detection, condition-based maintenance, failure prevention and non-destructive evaluation.
Abstract: A novel passive wireless-interrogation strain sensor is presented in this paper. The sensor employs a planar inductor with a series connected interdigital capacitor to eliminate the wire connection for power supply and data transmission. The sensor is activated by electromagnetic waves and the resonant frequency of the sensor is interrogated remotely with a single loop antenna by applying an oscillating signal to the antenna and monitoring the frequency response of the voltage across it. The prototype sensor and reader were designed and fabricated. The results of calibration on a constant-strain cantilever beam show great linearity and sensitivity. The innovative wireless strain sensing technology described herein has demonstrated a great potential to extend its applications in structural health monitoring, damage detection, condition-based maintenance, failure prevention and non-destructive evaluation.

141 citations

References
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Journal ArticleDOI
15 Nov 2001-Nature
TL;DR: This work combines several of these developments to fabricate a smart single-chip chemical microsensor system that incorporates three different transducers (mass-sensitive, capacitive and calorimetric), all of which rely on sensitive polymeric layers to detect airborne volatile organic compounds.
Abstract: Research activity in chemical gas sensing is currently directed towards the search for highly selective (bio)chemical layer materials, and to the design of arrays consisting of different partially selective sensors that permit subsequent pattern recognition and multi-component analysis. Simultaneous use of various transduction platforms has been demonstrated, and the rapid development of integrated-circuit technology has facilitated the fabrication of planar chemical sensors and sensors based on three-dimensional microelectromechanical systems. Complementary metal-oxide silicon processes have previously been used to develop gas sensors based on metal oxides and acoustic-wave-based sensor devices. Here we combine several of these developments to fabricate a smart single-chip chemical microsensor system that incorporates three different transducers (mass-sensitive, capacitive and calorimetric), all of which rely on sensitive polymeric layers to detect airborne volatile organic compounds. Full integration of the microelectronic and micromechanical components on one chip permits control and monitoring of the sensor functions, and enables on-chip signal amplification and conditioning that notably improves the overall sensor performance. The circuitry also includes analog-to-digital converters, and an on-chip interface to transmit the data to off-chip recording units. We expect that our approach will provide a basis for the further development and optimization of gas microsystems.

663 citations

Book
01 Jan 1987
TL;DR: Hoffmann et al. as mentioned in this paper presented the Handbook of microwave integrated circuits (HOLA) for the purpose of measuring the pressure fields using covariance and spectral proper transformations.
Abstract: 157 References References (1) F. Gardiol, Microstrip Circuits. New York 164 References (69) R. K. Hoffmann, Handbook of Microwave Integrated Circuits. random pressure fields using covariance and spectral proper transformations " pdf. tivity of Printed Circuit Board (PCB) substrates is important in modern ipc.org/4.0 Knowledge/4.1 Standards/test/2.5.5.6.pdf. (5) D. L. Wynants, “Dk or (16) R. K. Hoffmann, Handbook of microwave integrated circuits. Norwood. ( pdf / doi: 10.7567/APEX.8.011101 / IF: 2.567 ) Times cited: 1. 628 Martin Heilmann, Björn Hoffmann, Carsten Ronning, Marius Grundmann, Silke Christiansen Handbook of Zinc Oxide and Related Materials, Vol. Metal-semiconductor field-effect transistors and integrated circuits based on ZnO and related oxides

487 citations

Journal ArticleDOI
TL;DR: In this article, conformal mapping-based models for interdigital capacitors on substrates with a thin superstrate and/or covering dielectric film are given for ICs with finger numbers n/spl ges/2.
Abstract: Conformal mapping-based models are given for interdigital capacitors on substrates with a thin superstrate and/or covering dielectric film. The models are useful for a wide range of dielectric constants and layer thicknesses. Capacitors with finger numbers n/spl ges/2 are discussed. The finger widths and spacing between them may be different. The results are compared with the available data and some examples are given to demonstrate the potential of the models.

400 citations

Journal ArticleDOI
TL;DR: In this article, anomalous effects occurring in actual realizations of coplanar waveguides for microwave integrated circuits on GaAs substrates, such as the influence of an upper shield, conductor backing, finite-extent ground planes, and line-to-line coupling, are discussed and evaluated.
Abstract: Parasitic effects occurring in actual realizations of coplanar waveguides (CPW) for microwave integrated circuits on GaAs substrates, such as the influence of an upper shield, conductor backing, finite-extent ground planes, and line-to-line coupling, are discussed and evaluated. CAD-oriented analytical expressions are obtained for the electrical quasi-TEM parameters of the relevant waveguiding structures by means of exact or approximate conformal mapping techniques. Differences in electrical behavior with respect to ideal CPW's are highlighted, and practical design criteria are obtained for keeping cover height, ground-plane width, and line-to-line spacing effects to a minimum.

365 citations

Journal ArticleDOI
G.D. Alley1
TL;DR: In this article, an analysis of the frequency response of interdigital capacitors, which leads to an optimal design, along with an expression for their static gap capacitance, is given in terms of its geometry which consists of a planar interdigital thin-filrn conductor deposited on the surface of a relatively high dielectric constant substrate.
Abstract: An analysis of the frequency response of interdigital capacitors, which leads to an optimal design, is given along with an expression for their static gap capacitance. The capacitor Q is given in terms of its geometry which consists of a planar interdigital thin-filrn conductor deposited on the surface of a relatively high dielectric constant substrate. Capacitance values ranging from 0.1 to 10 pF at L band with measured Q's in excess of 400 are realizable using 2-mil line and space widths on a 99.5-percent alumina substrate with a dielectric constant of 10.3. Experimental results obtained with a lumped-constant nine-section S-band Chebyscheff low-pass filter realized using spiral inductors and optimal designed interdigital capacitors are shown to be in excellent agreement with theory. The filter had less than 0.8-dB insertion loss and greater than 25dB return loss in the passband. The filter occupies an area 6.50 by 200 roils on a 24-mil-thick substrate.

293 citations