Because SAW filters are small, high reliability, and it cannot be easily integrated with silicon substrate, they have become one of the most popular communication passive components recently. As the working frequency becomes higher, SAW filters are more sensitive to electromagnetic interference introduced by the package. Discrepancy in performance between design and measurement can be large if the packing effects are not considered. In this thesis, we make use of Finite Difference Time Domain method (FDTD) and develop a procedure combining High Frequency Structure Simulator (HFSS) with ADS software to simulate electromagnetic effect of a packaged SAW Filter. This is a full-wave method that integrates electromagnetic wave and acoustic wave. Measurement is also carried out to verify the simulated results. Preliminary results show that this method that we provide can predict frequency response in package effectively. Our Prediction can save factory design time and production cost.

Gallium arsenide is piezoelectric, so it is possible to generate coupled mechanical and electrical surface acoustic waves (SAWs) by applying a high-frequency voltage to a transducer on the surface of GaAs. By combining SAWs with existing low-dimensional nanostructures one can create a series of dynamic quantum dots corresponding to the minima of the travelling electric wave, and each dot carries a single electron at the SAW velocity (~ 2800 m/s). These devices may be of use in developing future quantum information processors, and also offer an ideal environment for probing the quantum mechanical behaviour of single electrons. This thesis describes a numerical and theoretical study of the dynamics ofan electron in a range of geometries. The numerical techniques for solving thetime-dependent Schrödinger equation with an arbitrary time-dependent potential will be described in Chapter 2, and then applied in Chapter 3 to calculate the transmission of an electron through an Aharonov-Bohm (AB) ring. It will be seen that an important property of the techniques used in this thesis is that they can be easily adapted to study realistic geometries, and we will see features in the AB oscillations which do not arise in simplified analytic descriptions. In Chapter 4, we will then study a device consisting of two parallel SAW channels separated by a controllable tunnelling barrier. We will use numerical simulations to investigate the effect of electric and magnetic fields upon the electron dynamics, and develop an analytic model to explain the simulation results. From the model, it will be apparent that it is possible to use this device to rotatethe state of the electron to an arbitrary superposition of the first two eigenstates. We then introduce coherent and squeezed states in Chapter 5, which are ex-cited states of the quantum harmonic oscillator. Coherent and squeezed electronicstates may be of use in quantum information processing, and could also arise dueto unwanted perturbations in a SAW device. We will discuss how these statescan be controllably generated in a SAW device, and also discuss how they couldthen be detected. In Chapter 6 we describe how to use the motion of a SAW to create a rapidly-changing potential in the frame of the electron, leading to a nonadiabatic excita-tion. The nonadiabatically-excited state oscillates from side to side within a 1Dchannel on a few-picosecond timescale, and this motion can be probed by placing a tunnelling barrier at one side of the channel. Numerical simulations will beperformed to show how this motion can be controlled, and the simulation resultswill be seen to be in good agreement with recent experimental work performed by colleagues. Finally, we will show that this device can be used to measure the initial state of an electron which is an arbitrary superposition of the first twoeigenstates.

No description available.

A multifunctional strain sensor based on Surface Acoustic Wave (SAW) Orthogonal Frequency Coding (OFC) technology on a Langasite substrate has been investigated. Second order transmission matrix models have been developed and verified. A new parameterizable library of SAW components was created to automate the layout process. Using these new tools, a SAW strain sensor with OFC reflectors was designed, fabricated and tested. The Langasite coefficients of velocity for strain (γS = 1.699) and Temperature (γT = 2.562) were experimentally determined. The strain and temperature characterization of this strain sensor, along with the coefficients of velocity, have been used to demonstrate both the ability to sense strain and the capability for temperature compensation. The temperature-compensated SAW OFC strain sensor has been used to detect anomalous strain conditions that are indicators of fastener failures during structural health monitoring of aircraft panels with and without noise on a NASA fastener failure test stand. The changes in strain that are associated with single fastener failures were measured up to a distance of 80 cm between the sensor and the removed fastener. The SAW OFC strain sensor was demonstrated to act as an impact sensor with and without noise on the fastener failure test stand. The average measured signal to noise ratio (SNR) of 50, is comparable to the 29.1 SNR of an acoustic emission sensor. The simultaneous use of a high pass filter for impact detection, while a low pass filter is used for strain or fastener failure, demonstrates the multifunctional capabilities of the SAW OFC sensor to act as both as a fastener failure detector and as an impact detector.

A semiconductor optical source monolithically integrated with a surface acoustic wave (SAW) Bragg-cell to operate as a functional device is proposed in this thesis. The practical structure of such an integrated device is demonstrated and design guidelines are presented. Compared with conventional optical beam processed devices, this functional integrated semiconductor optical source (FISOS) is revised to be compact in size, flexible in function and potentially robust in performance. <br /> The FISOS is analyzed as two sub-divisions, optical source and acoustic processor, which have the common substrate structure. The optical beams excited from the optical source part of the device undergoes a scattering in the Bragg grating formed by SAWs that are generated by an IDT positioned on top of the acoustic processing part of device. By altering the property (power, frequency, etc.) of the SAW, versatile functionalities such as modulation, filtering, beam steering and so on of the optical beams can be realized in this optical source device. <br /> A multilayer structure based on GaN/InGaN MQWs grown on sapphire is designed for the FISOS to be blue light emitting and efficiently launching SAWs. An etch-down technique employed in the SAW processing part is taken to improve the overlap between the optical and acoustic waves and then the interaction efficiency. Optimizations to the geometrical dimensions of the FISOS, such the width of the ridge waveguide, the position of the IDT and the etching depth, etc., are discussed in the given structure. <br /> Numerical models are investigated to access the operational characteristics and then to provide design guidelines for the proposed integrated device. The Bragg diffraction of optical waves occurring within the acoustic waves in the proposed structure are simulated as a two-dimensional interaction between two guided optical modes and an acoustic surface wave. <br /> The modal distributions and propagation velocities of SAWs in a multilayer system are calculated using Adler’s matrix method. The electrical characteristics of an IDT, such as impedance, insertion loss, electromechanical constant and so on are also discussed. <br /> Transverse and lateral optical modes in the given multilayer structure are analyzed by the transfer matrix method. The interaction of optical waves and acoustic waves are modeled using the rigorous grating diffraction theory. Starting from Floquet’s theory, the well-known coupled-wave method and modal method can both be derived from the rigorous grating diffraction theory. Discussions of some useful approximate methods are also presented. In this thesis, the simulations of the acoustooptic interaction are performed using the coupled-wave method. <br /> From the simulation results, the angular distribution profile and spatial profile of the output of the FISOS are evaluated. An improvement to the expression of the diffraction efficiency in such an integrated device is proposed. The so-called beam diffraction efficiency gives a more complete measure to the acoustooptic diffraction and is used to investigate the features of FISOS different from conventional acoustooptic devices. Contour plots of the beam efficiency varying with acoustic frequency and power in a FISOS is demonstrated to be a convenient and powerful approach in the device design. <br /> The operational performances of an integrated deflector and a modulator in FISOS are analyzed to investigate the feasibility of FISOS. The trade-off of the efficiency-resolution in an integrated deflector design is discussed. Short interaction length, high acoustic frequency and narrow ridge are proved to be helpful for a larger number of resolvable spots with a fairly high efficiency. In the case of the integrated modulator, given that the figure of merit Q is fixed, it is demonstrated that the smaller the Q, the longer the interaction length, larger ridge width and lower acoustic frequency will give rise to a larger bandwidth, though the highest efficiency might appear at a higher frequency. <br /> Some practical issues such as the misalignment of planar elements on the device and the incoherence of the integrated optical source are also discussed. A modified working frequency can be used to compensate the efficiency loss in the former case; in the latter case, it is demonstrated that a distortion of beam diffraction efficiency versus acoustic power with an incoherent optical source arises due to the wide spectrum of the incident optical waves.

La génération d’impulsions courtes d’ondes acoustiques de surface est étudiée, en s’inspirant du principe de l’amplification des impulsions chirpées qui est utilisée pour la génération d’impulsions laser ultrabrèves. La compression temporelle des impulsions est généralement réalisée à l’aide d’éléments dispersifs. Dans ce travail, un transducteur à ondes acoustiques de surface pouvant émettre des impulsions brèves est utilisé comme élément dispersif. Une étude comparative des transducteurs à peignes interdigités chirpés est menée avec un modèle du premier ordre et un modèle dit de matrice mixte. Des dispositifs à ondes acoustiques de surface sont conçus et réalisés à partir des résultats de simulation numérique. La façon de distribuer la période dans le transducteur est étudiée. L’apparition de bandes interdites dues aux réflexions internes dans le transducteur chirpé et son effet sur l’émission directionnelle des ondes surface sont en particulier observées et étudiées.Un interféromètre optique différentiel dans le domaine temporel et stabilisé est ensuite proposé afin de caractériser les impulsions brèves. Le transducteur à ondes acoustiques de surface est placé à l’extérieur de l’interféromètre. Des expériences sont conduites avec un transducteur à peignes interdigités chirpé ayant une bande opérationnelle couvrant la gamme de fréquences 200 MHz – 400 MHz et produisant des impulsions de 10 ns avec un déplacement hors-plan maximal de 36 nm. La réponse interférométrique est comparée à une mesure électrique directe obtenue à l’aide d’un transducteur de réception large bande ; une bonne correspondance des deux mesures est observée. Les influences de la différence de chemin optique dans l’interféromètre et du choix du point d’observation sur la surface sont discutées. La compression de l’impulsion le long du transducteur chirpé est observée expérimentalement.Finalement, une étude comparative de différents filtres de compression temporelle est présentée, dans l’objectif d’obtenir des impulsions optimales à la fois courtes temporellement et de forte intensité, pour un élément dispersif donné. Le filtre inverse est identifié comme le plus efficace et nous permet de produire les impulsions de plus grande amplitude. Afin d’optimiser la compression de l’impulsion pour les dispositifs fabriqués, des expériences sont conduites pour trouver les courbes de compromis optimal dans chaque cas de modulation de la période du transducteur. / Generation of short pulses with surface acoustic waves (SAW) is studied, in analogy with the principle of chirped pulse amplification (CPA) used to produce ultrashort laser pulses. Temporal compression of pulses is generally achieved with dispersive elements. A SAW transducer emitting short SAW pulses is used as a dispersive element in this work. A comparative study of chirped inter digital transducers (CIDTs) using the first order model and the p-matrix model is presented. SAW devices are designed and fabricated using the simulation results and the effect of the varying pitch of the CIDts on the response is studied. Appearance of band gaps due to internal reflections within the CIDts and its effect on the directionality of the CIDTs are in particular found and studied.A stabilized time-domain differential optical interferometer is then proposed in order to characterize short pulses, with the surface acoustic wave (SAW) sample placed outside the interferometer. Experiments are conducted with surface acoustic waves excited by a chirped inter-digital transducer on a piezoelectric lithium niobate substrate having an operational bandwidth covering the 200 MHz – 400 MHz frequency range and producing 10 ns pulses with 36 nm maximum out-of-plane displacement. The interferometric response is compared with a direct electrical measurement obtained with a receiving wide bandwidth inter-digital transducer and good correspondence is observed. The effects of varying the path difference of the interferometer and the measurement position on the surface are discussed. Pulse compression along the chirped inter-digital transducer is observed experimentally.Finally, a comparative study of different filter designs for generating short pulses is presented with an objective to find a design to produce the optimal pulse which is short in width and high in amplitude, for a given dispersive element. The inverse filter is found to be the most efficient as it produces a short pulse with the highest amplitude. To optimize the pulse compression for the fabricated devices, experiments are conducted to find the optimal trade-off curve for each chirp case.

The objective of this dissertation is to improve the performance of surface acoustic wave (SAW) biosensors for use in point-of-care-testing (POCT) applications. SAW biosensors have the ability to perform fast, accurate detection of an analyte in real time without the use of labels. However, the technology suffers from the inability to differentiate between specific and non-specific binding. Due to this limitation, direct testing of bodily fluids using SAW sensors to accurately determine an analyte's concentration is difficult. In addition, these sensors are challenged by the need to detect small concentrations of a biomarker that are typically required to give a clinical diagnosis. Sensitivity, selectivity and reliability are three critical aspects for any sensing platform. To improve sensitivity the delay path of a SAW sensor has been modified with microcavities filled with various materials. These filled cavities increased sensitivity by confining wave energy to the surface by way of constructive interference and waveguiding. Thus, the improved sensitivity will result in a lower limit of detection. In addition, insertion loss is decreased as a consequence of increased wave confinement to the surface. Sensor selectivity and reliability are adversely affected by non-specific binding of unwanted species present in a sample. To address this issue a multifunctional SAW sensor is presented. The sensor consists of two SAW delay lines oriented orthogonal to each on ST-quartz in order to generate two distinct wave modes. One wave mode is used for sensing while the other is used to remove loosely bound material. By using the same transduction mechanism for both removal and sensing, the sensor chip is simplified and complex electronics are avoided. The findings of this research involve the technological advances for SAW biosensors that make their use in POCT possible.

This thesis takes a fresh approach to cochlear mechanics. Over the last quarter of a century, we have learnt that the cochlea is active and highly tuned, observations suggesting that something may be resonating. Rather than accepting the standard traveling wave interpretation, here I investigate whether a resonance theory of some kind can be applied to this remarkable behaviour.¶ A historical survey of resonance theories is first conducted, and advantages and drawbacks examined. A corresponding look at the traveling wave theory includes a listing of its short-comings.¶ A new model of the cochlea is put forward that exhibits inherently high tuning. The surface acoustic wave (SAW) model suggests that the three rows of outer hair cells (OHCs) interact in a similar way to the interdigital transducers of an electronic SAW device. Analytic equations are developed to describe the conjectured interactions between rows of active OHCs in which each cell is treated as a point source of expanding wavefronts. Motion of a cell launches a wave that is sensed by the stereocilia of neighbouring cells, producing positive feedback. Numerical calculations confirm that this arrangement provides sharp tuning when the feedback gain is set just below oscillation threshold.¶ A major requirement of the SAW model is that the waves carrying the feedback have slow speed (5-200 mm/s) and high dispersion. A wave type with the required properties is identified - a symmetric Lloyd-Redwood wave (or squirting wave) - and the physical properties of the organ of Corti are shown to well match those required by theory.¶ The squirting wave mechanism may provide a second filter for a primary traveling wave stimulus, or stand-alone tuning in a pure resonance model. In both, cyclic activity of squirting waves leads to standing waves, and this provides a physical rendering of the cochlear amplifier. In keeping with pure resonance, this thesis proposes that OHCs react to the fast pressure wave rather than to bending of stereocilia induced by a traveling wave. Investigation of literature on OHC ultrastructure reveals anatomical features consistent with them being pressure detectors: they possess a cuticular pore (a small compliant spot in an otherwise rigid cell body) and a spherical body within (Hensens body) that could be compressible. I conclude that OHCs are dual detectors, sensing displacement at high intensities and pressure at low. Thus, the conventional traveling wave could operate at high levels and resonance at levels dominated by the cochlear amplifier. ¶ The latter picture accords with the description due to Gold (1987) that the cochlea is an ‘underwater piano’ - a bank of strings that are highly tuned despite immersion in liquid.¶ An autocorrelation analysis of the distinctive outer hair cell geometry shows trends that support the SAW model. In particular, it explains why maximum distortion occurs at a ratio of the two primaries of about 1.2. This ratio also produces near-integer ratios in certain hair-cell alignments, suggesting that music may have a cochlear basis.¶ The thesis concludes with an evaluation and proposals to experimentally test its validity.

It is demonstrated that by using a miniature chemical reaction vessel under adaptive mechatronic control, it is possible to design and construct a low-cost carbon dioxide measurement system. With further development such a system would be potentially suitable for low-cost commercial application, in particular as sacrificial, single-mission instrumentation packages in horticultural cargo monitoring. Current instrumentation systems for carbon dioxide (CO2) gas measurement are reviewed and their limitations with respect to low cost commercial applications determined. These utilise technology intended for laboratory measurements. In particular the optical energy absorbance of CO2 in the infra-red electromagnetic spectrum. These systems require large optical paths (typically 10cm) in order to measure small CO2 concentrations. This in turn has a large impact on the physical size of the sensing system. Of the many applications requiring online CO2 sensing packages (such as medical, petroleum, environmental and water treatment)the horticultural industry is the primary focus for this research. CO2 sensing systems are primarily used in horticulture to monitor the produce environment and help extend storage time. For these applications CO2 concentrations are typically low (in the range 0 to 1%) and the paramount need is for low-cost (and possibly disposable) sensing packages. The basis of the measurement technique is the use of bulk (but small volume) aqueous chemical reaction under mechatronic control. Unlike thin film technologies where very thin membranes are passively exposed to the gaseous sample, here a small volume (approximately 2mL) of simple and very cheap liquid chemical indicator (calcium hydroxide solution) is used to produce an opaque precipitate. CO2 concentration is then assessed by low-cost optical attenuation measurements of the developing opacity of the solution. The instrumentation package comprises pumps, flowmeter, reaction cell and infra-red optics for the turbidity measurement, plus reagent and waste vessels, pipelines and electronics. During each measurement cycle, the reaction cell is flushed, with fresh chemical indicator and a sample of gas admitted. The indicator and the sample gas are then vigorously mixed and the change in the indicators optical properties measured at regular intervals. An embedded 8-bit microcontroller performs the necessary analysis to deduce the CO2 concentration (as percentage by volume) for the sample gas by reference to one or more of five ``Time-To-Threshold'' calibration models. These models evaluate the trend in turbidity development as precipitate is formed. First and second prototypes of the measurement system have been constructed and their (low-cost) components and overall performance evaluated, the first a `proof-of-concept' and the second to investigate methodology shortcomings. As a result the design of a third prototype is outlined. The measurement systems have been shown to work adequately well within expected limitations, resulting in a usable low-cost measurement technique. The current prototypes have a useful range of at least 5% to 100% CO2 with a discrimination of typically +-6%. Deficiencies, particularly performance at low concentrations, are identified and potential enhancements for future prototypes proposed.

In this thesis, the study focuses on the tunable frequency ratio of Sierpinski Gasket fractal antennas and we use the SAW substrate of piezoelectric material. By using the fractal structure and the substrate of piezoelectric material, the goal of the miniaturized antenna is achieved. The proposed antenna can be widely used in wireless communication products. Firstly, we design the Sierpinski Gasket fractal antenna on the FR4 substrate. The asymmetric geometry of Sierpinski Gasket fractal structure is proposed and we choose the proper discontinuity locations to design the three-band and tunable antenna for IEEE 802.11b/g/a wireless communication systems. The preliminary design of the Sierpinski Gasket fractal structure on the piezoelectric substrate allows us to compare simulated and measured results to improve the non-ideal processing factors. Finally, comparing with the existing products, we reduce the size of the miniaturized fractal antenna to 5x5mm^2 on the SAW substrate by coplanar waveguide, coupled-fed, shorting with conductive adhesive and high iteration stage of half-Sierpinski Gasket fractal structure for GPS band and IEEE 802.11b/g applications.