Measurement of permeability for ferrous metallic plates using a novel lift-off compensation technique on phase signature

Lift-off of sensor affects the prediction of electromagnetic properties for both ferrous and non-ferrous steel plates. In this paper, we developed a strategy to address this issue for ferrous plates. With increased lift-off, the phase of the measured impedance for steel plates reduces. Meanwhile, the magnitude of the impedance signal decreases. Based on these facts, a phase compensation algorithm is developed which corrects the phase change due to lift-off considering the magnitude of the impedance signal. Further, a new magnetic permeability prediction technique is presented, which has been validated by analytical and measured results. With this new technique, the error in permeability prediction is less than 2% within the range of lift-offs tested

Thermal nonlinearity in radio frequency piezoelectric laterally vibrating resonators

In recent years, the demand for more wireless bandwidth (BW) has been soaring due to the booming of wireless applications in the marketplace and customers’ pursuit of higher data rates for communication. This need for more BW will continue to grow as the Internet of Things (IoT) foreshadows more applications requiring wireless connectivity and the use of radio spectrum. As a result, radio frequency (RF) front-end platforms capable of meeting the stringent requirements of higher performance and wider bandwidth are highly sought after and currently being heavily researched. These new platforms should be capable of dynamically operating in several dozens of frequency bands while maintaining high performance. RF piezoelectric laterally vibrating resonators (LVRs) have recently emerged as a promising candidate for front-end filtering and multiplexing in future radios. Compared with the incumbent filtering technology, such as thin-film bulk acoustic resonators (FBARs) and surface acoustic wave resonators (SAWs), this new class of microelectromechanical systems (MEMS) features an assortment of advantages, including integration capability with CMOS, frequency scalability towards higher frequencies, greater electromechanical coupling, and lower loss. Despite these promising features, LVRs still face the challenge of attaining linear response at high power levels and diminishing the intermodulation distortion. The moderate linearity and power handling, which are caused by the intrinsic thermal nonlinearity, produce an unacceptable amount of interference in front-ends. In this thesis, an analytical method has been developed to predict the thermal nonlinearity accurately. It is subsequently leveraged to reduce the nonlinear behavior of LVRs. The organization of the thesis is as follows. In Chapter 1, fundamentals of MEMS resonators are discussed. Chapter 2 explains the operating principles of piezoelectric LVRs in detail, describes the dominant nonlinearities in piezoelectric LVRs, and presents the prior studies on nonlinearities in piezoelectric LVRs. In Chapter 3, a quantitative approach is presented to precisely model the nonlinear dynamics and accurately predict the intermodulation distortions in LVRs. Chapter 4 focuses on the experimental validation of the theoretical analysis. The last chapter concludes with the impact of the method described herein on guiding future optimizations and enhancing the power handling of LVRs for real-world applications

A Radio Frequency Non-reciprocal Network Based on Switched Low-loss Acoustic Delay Lines

This work demonstrates the first non-reciprocal network based on switched low-loss acoustic delay lines. A 21 dB non-reciprocal contrast between insertion loss (IL=6.7 dB) and isolation (28.3 dB) has been achieved over a fractional bandwidth of 8.8% at a center frequency 155MHz, using a record low switching frequency of 877.22 kHz. The 4-port circulator is built upon a newly reported framework by the authors, but using two in-house fabricated low-loss, wide-band lithium niobate (LiNbO3) delay lines with single-phase unidirectional transducers (SPUDT) and commercial available switches. Such a system can potentially lead to future wide-band, low-loss chip-scale nonreciprocal RF systems with unprecedented programmability.Comment: 4 pages, 7 figure

Capstone Revival

The capstone project is a culminating experience whereby students choose to research a topic that is relevant in their field of study and have been highly regarded as important learning activities. The capstone allows students to use research, analytical, problem solving and evaluation skills they have learned in the course of the graduate program. McGill indicates the benefit of the completion of a capstone project not only in gaining knowledge in capstone but also in learning how to apply the knowledge gained in other courses in the major (McGill, 2012). Currently, COPACE (College of Professional and Continuing Education) has three separate capstone programs – one each for MPA, MSPC, and MSIT. The goal of this study is to evaluate our existing capstones at COPACE and identify the components of a quality capstone program to benefit future capstones. This study will also determine whether integrating these three separate capstones programs into a single standard capstone is more beneficial than the current model. We will also show how to improve the existing capstones programs. The methods used in this study are: survey, broad research on other universities and analysis of 44 COPACE capstones. The target populations of the survey are COPACE graduate students graduated from 2013 to 2014. An anonymous questionnaire was sent by email to approximately 120 Clark students. The survey results are interpreted with suggestions for achieving more consistency in capstones

Frequency Independent Framework for Synthesis of Programmable Non-reciprocal Networks

Passive and linear nonreciprocal networks at microwave frequencies hold great promises in enabling new front-end architectures for wireless communication systems. Their nonreciprocity has been achieved by disrupting the time-reversal symmetry using various forms of biasing schemes, but only over a limited frequency range. Here we demonstrate a framework for synthesizing theoretically frequency-independent multi-port nonreciprocal networks. The framework is highly expandable, and can have an arbitrary number of ports while simultaneously sustaining balanced performance and providing unprecedented programmability of non-reciprocity. A 4-port circulator based on such a framework is implemented and tested to produce broadband nonreciprocal performance from 10 MHz to 900 MHz with a temporal switching effort at 23.8 MHz. With the combination of broad bandwidth, low temporal effort, and high programmability, the framework could inspire new ways of implementing multiple input multiple output (MIMO) communication systems for 5G.Comment: 10 pages, 6 figure

Reduction of Coil-Crack Angle Sensitivity Effect Using a Novel Flux Feature of ACFM Technique

Alternating current field measurement (ACFM) testing is one of the promising techniques in the field of non-destructive testing with advantages of the non-contact capability and the reduction of lift-off effects. In this paper, a novel crack detection approach was proposed to reduce the effect of the angled crack (cack orientation) by using rotated ACFM techniques. The sensor probe is composed of an excitation coil and two receiving coils. Two receiving coils are orthogonally placed in the center of the excitation coil where the magnetic field is measured. It was found that the change of the x component and the peak value of the z component of the magnetic field when the sensor probe rotates around a crack followed a sine wave shape. A customized accelerated finite element method solver programmed in MATLAB was adopted to simulate the performance of the designed sensor probe which could significantly improve the computation efficiency due to the small crack perturbation. The experiments were also carried out to validate the simulations. It was found that the ratio between the z and x components of the magnetic field remained stable under various rotation angles. It showed the potential to estimate the depth of the crack from the ratio detected by combining the magnetic fields from both receiving coils (i.e., the x and z components of the magnetic field) using the rotated ACFM technique

Toward Ka Band Acoustics: Lithium Niobate Asymmetrical Mode Piezoelectric MEMS Resonators

This work presents a new class of micro-electro-mechanical system (MEMS) resonators toward Ka band (26.5-40GHz) for fifth-generation (5G) wireless communication. Resonant frequencies of 21.4 and 29.9 GHz have been achieved using the fifth and seventh order asymmetric (A5 and A7) Lamb-wave modes in a suspended Z-cut lithium niobate (LiNbO3) thin film. The fabricated device has demonstrated an electromechanical coupling (kt2) of 1.5% and 0.94% and extracted mechanical Qs of 406 and 474 for A5 and A7 respectively. The quality factors are the highest reported for piezoelectric MEMS resonators operating at this frequency range. The demonstrated performance has shown the strong potential of LiNbO3 asymmetric mode devices to meet the front-end filtering requirements of 5G.Comment: 5 pages, 7 figures, 2018 IEEE International Frequency Control Symposiu

An equivalent-effect phenomenon in eddy current non-destructive testing of thin structures

The inductance/impedance due to thin metallic structures in non-destructive testing (NDT) is difficult to evaluate. In particular, in Finite Element Method (FEM) eddy current simulation, an extremely fine mesh is required to accurately simulate skin effects especially at high frequencies, and this could cause an extremely large total mesh for the whole problem, i.e. including, for example, other surrounding structures and excitation sources like coils. Consequently, intensive computation requirements are needed. In this paper, an equivalent-effect phenomenon is found, which has revealed that alternative structures can produce the same effect on the sensor response, i.e. mutual impedance/inductance of coupled coils if a relationship (reciprocal relationship) between the electrical conductivity and the thickness of the structure is observed. By using this relationship, the mutual inductance/impedance can be calculated from the equivalent structures with much fewer mesh elements, which can significantly save the computation time. In eddy current NDT, coils inductance/impedance is normally used as a critical parameter for various industrial applications, such as flaw detection, coating and microstructure sensing. Theoretical derivation, measurements and simulations have been presented to verify the feasibility of the proposed phenomenon