Mechanical-Resonance-Enhanced Thin-Film Magnetoelectric Heterostructures for Magnetometers, Mechanical Antennas, Tunable RF Inductors, and Filters

The strong strain-mediated magnetoelectric (ME) coupling found in thin-film ME heterostructures has attracted an ever-increasing interest and enables realization of a great number of integrated multiferroic devices, such as magnetometers, mechanical antennas, RF tunable inductors and filters. This paper first reviews the thin-film characterization techniques for both piezoelectric and magnetostrictive thin films, which are crucial in determining the strength of the ME coupling. After that, the most recent progress on various integrated multiferroic devices based on thin-film ME heterostructures are presented. In particular, rapid development of thin-film ME magnetometers has been seen over the past few years. These ultra-sensitive magnetometers exhibit extremely low limit of detection (sub-pT/Hz1/2) for low-frequency AC magnetic fields, making them potential candidates for applications of medical diagnostics. Other devices reviewed in this paper include acoustically actuated nanomechanical ME antennas with miniaturized size by 1-2 orders compared to the conventional antenna; integrated RF tunable inductors with a wide operation frequency range; integrated RF tunable bandpass filter with dual H- and E-field tunability. All these integrated multiferroic devices are compact, lightweight, power-efficient, and potentially integrable with current complementary metal oxide semiconductor (CMOS) technology, showing great promise for applications in future biomedical, wireless communication, and reconfigurable electronic systems

Microwave Magnetoelectric Devices

Tunable microwave magnetoelectric devices based on layered ferrite-ferroelectric structures are described. The theory and experiment for attenuator, band-pass filter and phase shifter are presented. Tunability of the ME devices characteristics can be executed by application of an electric field. This electric tuning is relatively fast and is not power-consuming. The attenuator insertion losses vary from 26 dB to 2 dB at frequency 7251 MHz. The tuning range of 25 MHz of band-pass filter at frequency 7360 MHz was obtained. A maximum phase shift of 30–40 degree at the frequency region 6–9 GHz was obtained

Recent Advances in the mm-Wave Array for Mobile Phones

With the development of communication system to the mm-wave band, the antenna design in the mm-wave band for mobile phones encounters new requirements and challenges. The mm-wave characteristics of short wavelength, high free-space path loss, and easy-to-be-blocking usually require mm-wave antennas with high gain and beam-scanning capability. Also, considering the very limited space occupied by antennas in mobile phones and the massive production of consumer electronics, small size, low cost, multiband, multi-polarization, and wide beam steering becomes the main key point of mm-wave array performance. In addition, as a special situation of the mobile antenna, the analysis of effect of the human tissue on the antenna performance is also important. So, in this chapter, a comprehensive summary on the recent advances in the mm-wave array for mobile phones including single-band, dual-band, and reconfigurable design of broadside array, horizontal polarized, vertical polarized, and dual-polarized design of endfire array, co-design of mm-wave array with lower band antenna, and user influence are summarized

ΔE-Effect Magnetic Field Sensors

Many conceivable biomedical and diagnostic applications require the detection of small-amplitude and low-frequency magnetic fields. Against this background, a magnetometer concept is investigated in this work based on the magnetoelastic ΔE effect. The ΔE effect causes the resonance frequency of a magnetoelastic resonator to detune in the presence of a magnetic field, which can be read-out electrically with an additional piezoelectric phase. Various microelectromechanical resonators are experimentally analyzed in terms of the ΔE effect and signal-and-noise response. This response is highly complex because of the anisotropic and nonlinear coupled magnetic, mechanical, and electrical properties. Models are developed and extended where necessary to gain insights into the potentials and limits accompanying sensor design and operating parameters. Beyond the material and geometry parameters, we analyze the effect of different resonance modes, spatial property variations, and operating frequencies on sensitivity. Although a large ΔE effect is confirmed in the shear modulus, the sensitivity of classical cantilever resonators does not benefit from this effect. An approach utilizing surface acoustic shear-waves provides a solution and can detect small signals over a large bandwidth. Comprehensive analyses of the quality factor and piezoelectric material parameters indicate methods to increase sensitivity and signal-to-noise ratio significantly. First exchange-biased ΔE-effect sensors pave the way for compact setups and arrays with a large number of sensor elements. With an extended signal-and-noise model, specific requirements are identified that could improve the signal-to-noise ratio. The insights gained lead to a new concept that can circumvent previous limitations. With the results and models, important contributions are made to the understanding and development of ΔE-effect sensors with prospects for improvements in the future

Next Generation Acoustic and Magnetic Devices for Radio Frequency Communication

This dissertation primarily focuses on utilizing low wave speed acoustic waves coupled with electromagnetics to increase performance of radio frequency front end architectures and reduce device dimensions. Chapter 1 begins with the history of communication technology beginning with Maxwell’s equations. Next brief introductions into the piezoelectricity, magnetism, and multiferroics are given to lay the groundwork for the following Chapters.Chapter 2 of this dissertation aims at improving the capability of communicating in lossy RF-denied media such as seawater. First, magnetic antennas are theoretically analyzed and compared to electric antennas showing that magnetic antennas perform better when surrounded by lossy conductive media. Next, a prototype multiferroic antenna is developed that uses piezoelectric PZT and magnetostrictive FeGa. The PZT applies a time varying stress to the FeGa causing the FeGa’s internal flux density to dynamically vary resulting in a time-varying magnetic near field. Magnetic near field measurements are compared to an analytical model showing good agreement.In Chapter 3 Lamb wave devices are investigated for filtering and frequency conversion applicationsin RF-front ends. Leveraging micro-fabrication techniques two Lamb wave delay lines are fabricated out of piezoelectric aluminum nitride (AlN). Interdigitated transducers (IDTs) are used to launch and receive Lamb waves as well as generate a time and space varying mechanical compliance. A circuit model is developed to compare to the experimental results and determine the magnitude of the compliance nonlinearity present in the AlN. Results show that acoustic devices can be developed that simultaneously filter and down-convert or up-convert a signal.Chapter 4 numerically analyzes strain tunable magnetic filters for applications in software defined radio and cognitive radio. For these applications filters with a tunable bandpass are necessary. The design relies on two CoFeB ellipses deposited on piezoelectric PMN-PT. An electric field is applied through the thickness of the PMN-PT resulting in a strain applied to the CoFeB ellipses. The electric field can be applied to either strain one ellipse or both ellipses. Straining both ellipses results in a tunable susceptibility from 6 GHz to 8 GHz, while straining only one ellipse results in a broadening of the bandpass response. These results show a potential solution for dynamic filters for next generation communication architectures

Огляд сучасних фільтруючих пристроїв НВЧ і їх методів побудови

It is well known that oscillatory systems play an extremely high role in radio engineering. The resonators are oscillatory systems for the ultrahigh frequency range that representing a large and significant class of superhigh frequency devices. The article provides an overview of modern superhigh frequency filtering devices, recent interpretations about their main properties and methods of construction. An important factor that defines an issue of filter composition is the transition to integrated circuits containing elements with distributed parameters which accompanied by a number of undesirable phenomena: Q-factor, parasitic bandwidth and wave types of oscillations. The research has shown that the optimization of the design factors of oscillatory systems in such a way that their frequency characteristics are changed, will reduce the losses of the resonators.Хорошо известно, какую важную роль играют в радиотехнике колебательной системы. Колебательными системами для диапазона сверхвысоких частот является резонаторы, представляющие большой и значительный класс устройств СВЧ. В статье проведен обзор современных фильтрующих устройств СВЧ, современные представления об их основных свойствах и методы построения. Существенным фактором, определяющим проблемы фильтростроения является то, что переход к интегральным схемам, содержащим элементы с распределенными параметрами, сопровождается рядом нежелательных явлений: добротность, паразитные полосы пропускания и волновые типы колебаний. Исследование показало, что оптимизация конструктивных параметров колебательных систем таким образом, чтобы менялись их частотные характеристики, приведет к уменьшению потерь резонаторов.Добре відомо, яку виключно важливу роль відіграють в радіотехніці коливальні системи. Коливальними системами для діапазону надвисоких частот є резонатори, що представляють великий і значний клас пристроїв НВЧ. У статті проведено огляд сучасних фільтруючих пристроїв НВЧ , сучасні уявлення про їх основні властивості та методи  побудови. Істотним чинником, що визначає проблеми фільтробудування є те, що перехід до інтегральних схем, що містять елементи з розподіленими параметрами, супроводжується рядом небажаних явищ: добротність, паразитні смуги пропускання і хвильові типи коливань. Дослідження показало,  що оптимізація конструктивних параметрів коливальних систем таким чином, щоб змінювались їх частотні характеристики, призведе до зменшення втрат резонаторів

Impedance Transformers

Non

Magnetoelectric Sensor Systems and Applications

In the field of magnetic sensing, a wide variety of different magnetometer and gradiometer sensor types, as well as the corresponding read-out concepts, are available. Well-established sensor concepts such as Hall sensors and magnetoresistive sensors based on giant magnetoresistances (and many more) have been researched for decades. The development of these types of sensors has reached maturity in many aspects (e.g., performance metrics, reliability, and physical understanding), and these types of sensors are established in a large variety of industrial applications. Magnetic sensors based on the magnetoelectric effect are a relatively new type of magnetic sensor. The potential of magnetoelectric sensors has not yet been fully investigated. Especially in biomedical applications, magnetoelectric sensors show several advantages compared to other concepts for their ability, for example, to operate in magnetically unshielded environments and the absence of required cooling or heating systems. In recent years, research has focused on understanding the different aspects influencing the performance of magnetoelectric sensors. At Kiel University, Germany, the Collaborative Research Center 1261 “Magnetoelectric Sensors: From Composite Materials to Biomagnetic Diagnostics”, funded by the German Research Foundation, has dedicated its work to establishing a fundamental understanding of magnetoelectric sensors and their performance parameters, pushing the performance of magnetoelectric sensors to the limits and establishing full magnetoelectric sensor systems in biological and clinical practice

Tunable ferroelectric thin film devices for microwave applications

Ph.DDOCTOR OF PHILOSOPH