Nonlinear mechanisms in passive microwave devices

Premi extraordinari doctorat curs 2010-2011, àmbit d’Enginyeria de les TICThe telecommunications industry follows a tendency towards smaller devices, higher power and higher frequency, which imply an increase on the complexity of the electronics involved. Moreover, there is a need for extended capabilities like frequency tunable devices, ultra-low losses or high power handling, which make use of advanced materials for these purposes. In addition, increasingly demanding communication standards and regulations push the limits of the acceptable performance degrading indicators. This is the case of nonlinearities, whose effects, like increased Adjacent Channel Power Ratio (ACPR), harmonics, or intermodulation distortion among others, are being included in the performance requirements, as maximum tolerable levels. In this context, proper modeling of the devices at the design stage is of crucial importance in predicting not only the device performance but also the global system indicators and to make sure that the requirements are fulfilled. In accordance with that, this work proposes the necessary steps for circuit models implementation of different passive microwave devices, from the linear and nonlinear measurements to the simulations to validate them. Bulk acoustic wave resonators and transmission lines made of high temperature superconductors, ferroelectrics or regular metals and dielectrics are the subject of this work. Both phenomenological and physical approaches are considered and circuit models are proposed and compared with measurements. The nonlinear observables, being harmonics, intermodulation distortion, and saturation or detuning, are properly related to the material properties that originate them. The obtained models can be used in circuit simulators to predict the performance of these microwave devices under complex modulated signals, or even be used to predict their performance when integrated into more complex systems. A key step to achieve this goal is an accurate characterization of materials and devices, which is faced by making use of advanced measurement techniques. Therefore, considerations on special measurement setups are being made along this thesis.Award-winningPostprint (published version

Design of a New Step-like Frame FBAR for Suppression of Spurious Resonances

Film bulk acoustic wave resonators (FBARs) are of great interest for wireless applications due to its inherent advantages at microwave frequencies. However, the presence of spurious modes near the main resonance degrades the performance of resonators and requires development of new methods to suppress such unwanted modes. Different techniques are used to suppress these spurious modes. In this paper, we present design of a new step-like frame structure film bulk acoustic wave resonator operating near 1.5 GHz. The simulated results are compared with simple frame-like structure. The spurious resonances are eliminated effectively and smooth pass band is obtained with effective coupling coefficient of 5.68% and quality factor of 1800. The equivalent electrical mBVD model of the FBAR based on impedance response is also presented. These highly smooth phase response and passband skirt steepness resonators are most demanding for the design of low cost, small size and high performance filters, duplexers and oscillators for wireless systems

Theoretical and experimental development of a ZnO-based laterally excited thickness shear mode acoustic wave immunosensor for cancer biomarker detection

The object of this thesis research was to develop and characterize a new type of acoustic biosensor - a ZnO-based laterally excited thickness shear mode (TSM) resonator in a solidly mounted configuration. The first specific aim of the research was to develop the theoretical underpinnings of the acoustic wave propagation in ZnO. Theoretical calculations were carried out by solving the piezoelectrically stiffened Christoffel equation to elucidate the acoustic modes that are excited through lateral excitation of a ZnO stack. A finite element model was developed to confirm the calculations and investigate the electric field orientation and density for various electrode configurations. A proof of concept study was also carried out using a Quartz Crystal Microbalance device to investigate the application of thickness shear mode resonators to cancer biomarker detection in complex media. The results helped to provide a firm foundation for the design of new gravimetric sensors with enhanced capabilities. The second specific aim was to design and fabricate arrays of multiple laterally excited TSM devices and fully characterize their electrical properties. The solidly mounted resonator configuration was developed for the ZnO-based devices through theoretical calculations and experimentation. A functional mirror comprised of W and SiO2 was implemented in development of the TSM resonators. The devices were fabricated and tested for values of interest such as Q, and electromechanical coupling (K2) as well as their ability to operate in liquids. The third specific aim was to investigate the optimal surface chemistry scheme for linking the antibody layer to the ZnO device surface. Crosslinking schemes involving organosilane molecules and a phosphonic acid were compared for immobilizing antibodies to the surface of the ZnO. Results indicate that the thiol-terminated organosilane provides high antibody surface coverage and uniformity and is an excellent candidate for planar ZnO functionalization. The fourth and final specific aim was to investigate the sensitivity of the acoustic immunosensors to potential diagnostic biomarkers. Initial tests were performed in buffer spiked with varying concentrations of the purified target antigen to develop a dose-response curve for the detection of mesothelin-rFc. Subsequent tests were carried out in prostate cancer cell line conditioned medium for the detection of PSA. The results of the experiments establish the operation of the devices in complex media, and indicate that the acoustic sensors are sensitive enough for the detection of biomolecular targets at clinically relevant concentrations.Ph.D.Committee Chair: William D Hunt; Committee Member: Bruno Frazier; Committee Member: Dale Edmondson; Committee Member: Marie Csete; Committee Member: Peter Edmonson; Committee Member: Ruth O'Rega

Design and Modeling of Ferroelectric BST FBARs for Switchable RF Bulk Acoustic Wave Filters.

Multi-standard smartphones have become ubiquitous in everyday life. Such systems operate under different communication standards (2G, 3G, 4G-LTE, WLAN, GPS, Bluetooth, etc.) at different frequencies. Compact and high-performance filters are indispensable for RF front-ends in mobile phones, and RF bulk acoustic wave (BAW) filters, based on piezoelectric film bulk acoustic resonators (FBARs), have become prevalent. Moreover, due to the upcoming Internet of Things (IoT) and 5G, the demand for new technologies that can be employed to design switchable/tunable filters has increased. This dissertation presents one of the new promising technologies, known as intrinsically-switchable BAW filters employing newly-investigated electrostrictive effect in BST thin films. Successful implementation of switchable filters would eliminate/minimize external switches in the design of filter banks, thus leading to significant reduction in their size, cost, and complexity. Contributions of this work are categorized into three major parts. First, the nonlinear circuit modeling procedure for BST FBARs is presented. The nonlinear circuit model, essential for the material characterization and device characterization including linearity analysis, is developed based on the physics of electrostriction-based intrinsically switchable FBARs. Modeling results are in close agreement with dc-bias-voltage and RF-power-level dependent measurement results for BST FBARs. Second, the design methods for BST-on-Si composite FBARs are presented. The designed composite FBAR shows a record Q of 970 at 2.5 GHz among switchable BST resonators. Temperature-dependent characteristics of BST-on-Si composite FBAR devices are also presented with the measured TCF of -35 ppm/K. Furthermore, a raised-frame technique, which has been used to eliminate lateral-wave spurious-modes in piezoelectric BAW resonators, is first employed for switchable ferroelectric FBARs, demonstrating the effectiveness of the frame technique. Finally, the design method for intrinsically switchable BST FBAR filters is presented. The filter design method for ladder-type BAW filters is developed based on image parameters. Closed-form equations are derived for the first time enabling one to accurately design BAW filters. A systematically-designed pi-type BST FBAR filter is fabricated and measured, exhibiting a 1.22% bandwidth at 1.97 GHz with an isolation of greater than 22 dB, having a very small device size of 0.021 mm2.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133215/1/seungku_1.pd

RLC – модель акустического импеданса брэгговского отражателя

В роботі представлена розроблена авторами RLC модель бреггівського відбивача. Завдяки спрощеності структури дана модель може бути легко інтегрована в більшість сучасних САПР і дозволить з високою точністю визначати вихідні характеристики відбивача у відносно широкому близькорезонансному частотному діапазоні, що особливо важливо при моделюванні тонкоплівкових п'єзоелектричних резонаторів. Проведена верифікація моделі, що включила аналіз частотної залежності повного акустичного імпедансу у вузькому і широкому частотних діапазонах, дослідження узгодженості моделі при варіації кількості шарів бреггівського відбивача і при використанні різних матеріалів. Наведено розрахунок помилки узгодженості для різних частотних діапазонів, що дозволило визначити межі застосування моделі. Важливою перевагою запропонованої RLC моделі є збільшення ефективності розрахунку та оптимізації складних схем із застосуванням великої кількості резонаторів за рахунок скорочення часу розрахунку відбивача.The simplified RLC model of Bragg reflector impedance was developed and presented in this work. The model allows the straightforward integration of the reflector’s electrical behavior into the most of modern CAD systems as a part of complex devices and enables the precise evaluation of the output characteristics in a relatively wide near-resonant frequency range. This is especially important in the modelling of RF systems composed of thin film bulk acoustic resonators. The model verification was given including the analysis of the total impedance frequency dependence in wide and narrow frequency ranges, the model agreement examination for different number of layers and using various materials. The evaluation of agreement error for different frequency bands presented which allowed one to determine the limits of applicability of RLC model. An important advantage of proposed solution is the decreasing of calculation time and improving of optimization efficiency of complex RF circuits with a large number of resonators.работе представлена разработанная авторами RLC модель брэгговского отражателя. Благодаря упрощенности структуры данная модель может быть легко интегрирована в большинство современных САПР и позволит с высокой точностью определять выходные характеристики отражателя в относительно широком околорезонансном частотном диапазоне, что особенно важно при моделировании тонкопленочных пьезоэлектрических резонаторов. Проведена верификация модели, включающая анализ частотной зависимости полного акустического импеданса в узком и широком частотных диапазонах, исследование согласованности модели при вариации количества слоев брэгговского зеркала и при использовании различных материалов. Приведен расчет ошибки согласованности для различных частотных диапазонов, позволяющий определить границы применимости модели. Важным преимуществом предложенной RLC модели является увеличение эффективности расчета и оптимизации сложных схем с применением большого количества резонаторов за счет сокращения времени расчета отражателя

Thin-film piezoelectric-on-substrate resonators and narrowband filters

A new class of micromachined devices called thin-film piezoelectric-on-substrate (TPoS) resonators is introduced, and the performance of these devices in RF and sensor applications is studied. TPoS resonators benefit from high electromechanical coupling of piezoelectric transduction mechanism and superior acoustic properties of a substrate such as single crystal silicon. Therefore, the motional impedance of these resonators are significantly smaller compared to typical capacitively-transduced counterparts while they exhibit relatively high quality factor and power handling and can be operated in air. The combination of all these features suggests TPoS resonators as a viable alternative for current acoustic devices. In this thesis, design and fabrication methods to realize dispersed-frequency lateral-extensional TPoS resonators are discussed. TPoS devices are fabricated on both silicon-on-insulator and thin-film nanocrystalline diamond substrates. The performance of these resonators in simple and low-power oscillators is measured and compared. Furthermore, a unique coupling technique for implementation of high frequency filters is introduced in which dual resonance modes of a single resonant structure are coupled. The measured results of this work show that these filters are suitable candidates for single-chip implementation of multiple-frequency narrow-band filters with high out-of-band rejection in a small footprint.Ph.D.Committee Chair: Farrokh Ayazi; Committee Member: James D. Meindl; Committee Member: John D. Cressler; Committee Member: Nazanin Bassiri-Gharb; Committee Member: Oliver Bran