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Author

K. A. Jose

Bio: K. A. Jose is an academic researcher from Pennsylvania State University. The author has contributed to research in topics: Surface acoustic wave & Gyroscope. The author has an hindex of 16, co-authored 65 publications receiving 1296 citations.

Papers published on a yearly basis

Papers
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MonographDOI
25 Oct 2002
TL;DR: In this article, the authors present an integration and packaging for RF MEMS devices, including inductors and capacitors, phase shifters, and relay switches. But they do not discuss how to construct them.
Abstract: Preface. Microelectromechanical Systems (MEMS) and Radio Frequency MEMS. MEMS Materials and Fabrication Techniques. RF MEMS Switches and Micro Relays. MEMS Inductors and Capacitors. Micromachined RF Filters. Micromachined Phase Shifters. Micromachined Transmission Lines and Components. Micromachined Antennae. Integration and Packaging for RF MEMS Devices. Index.

348 citations

Journal ArticleDOI
TL;DR: In this article, the usefulness of fractal Hilbert curves in antenna geometry is explored for the first time, and an antenna size smaller than λ/10 and still resonant, with performance comparable to a dipole whose resonant length is close to λ 2.
Abstract: The usefulness of fractal Hilbert curves in antenna geometry is explored here for the first time. Apart from being simple and self-similar, these curves have the additional property of approximately filling a plane. These properties are exploited in realizing a “small” resonant antenna. This approach has resulted in an antenna size smaller than λ/10 and still resonant, with performance comparable to a dipole whose resonant length is close to λ/2. Numerical predictions of the input impedance of the antenna have been compared with experiments. The effect of additional fractal iterations on the reduction of the resonant frequency has been studied. The radiation characteristics of the antenna at the resonant frequencies provided show that this is very similar to the dipole characteristics. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 215–219, 2001.

166 citations

Proceedings ArticleDOI
08 Jul 2001
TL;DR: In this paper, an approximate formulation for the resonant frequency of a dipole Hilbert curve fractal antenna (HCFA) is derived, which can be used as small resonant antennas useful in VHF/UHF communication.
Abstract: An approximate formulation for the resonant frequency of a dipole Hilbert curve fractal antenna (HCFA) is derived here. These can be used as small resonant antennas, useful in VHF/UHF communication. The formulas presented here can be appropriately inverted to obtain the design equations for the antenna, for a given resonant frequency.

75 citations

Journal ArticleDOI
TL;DR: In this article, a dielectric tunable microstrip antenna on a barium strontium titanate substrate is presented, where the resonant frequency of the antenna is found to change more than 3% by changing the applied bias voltage.
Abstract: The narrow bandwidth of conventional microstrip antennas has many restrictions in real-time applications. The tunable dielectric and magnetic materials offer solutions to this problem. This paper presents the design and experimental investigations on a dielectric tunable microstrip antenna on barium strontium titanate substrate. The resonant frequency of the antenna is found to change more than 3% by changing the applied bias voltage. It would be possible to achieve more tunability by using proper dc blocking circuits and higher bias voltages. It is already established that the changes in dielectric constant of these substrate materials are more than 50% depending on the BST composition on changing the bias voltage. It is also possible to control the dielectric constant during the processing of substrates in the range of 15 to 1500 with some trade-off in tunability. The tunability of the BST substrate is found to have advantages in development of wideband microstrip antenna arrays and phase shifters.

68 citations

Journal ArticleDOI
TL;DR: In this paper, a 1 cm×1 cm gyroscope based on a surface acoustic wave resonator (SAW) and a sensor is presented. But unlike other MEMS gyroscopes based on silicon vibratory structures that utilize the energy transfer between the two vibratory modes, which require small fabrication tolerances to minimize signal output when there is no rotation (i.e., zero rate output), the SAWR creates standing waves within the cavity space between the interdigital transducers (IDTs).
Abstract: The design, development and performance evaluation of a novel radio frequency microelectromechanical systems (MEMS) gyroscope, based on a surface acoustic wave resonator (SAWR) and a surface acoustic wave sensor is presented in this paper. Most of the MEMS gyroscopes based on silicon vibratory structures that utilize the energy transfer between the two vibratory modes demand small fabrication tolerances to minimize signal output when there is no rotation (i.e. zero rate output). This 1 cm×1 cm gyroscope operates based on the principle of a surface acoustic wave (SAW) on a piezoelectric substrate. The SAWR creates SAW standing waves within the cavity space between the interdigital transducers (IDTs). The particles at the anti-nodes of a standing wave experience large amplitudes of vibration perpendicular to the plane of the substrate, which serves as the reference vibrating motion for this gyroscope. A number of metallic dots (proof masses) are strategically positioned at the anti-node locations so that the effect of the Coriolis force due to rotation will amplify the magnitude of the SAW that is generated in the orthogonal direction. The performance of this 74.2 MHz MEMS-IDT gyroscope has been evaluated using rate table and geophone set-ups, indicating very high sensitivity and dynamic range, which is ideal for many of the commercial applications. Unlike other MEMS gyroscopes, this gyroscope has a planar configuration with no suspended resonating mechanical structures, thereby being inherently robust and shock resistant. In view of its one-layer planar configuration, this gyroscope can be implemented for applications requiring conformal mounting onto a surface of interest.

67 citations


Cited by
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Journal ArticleDOI
TL;DR: Fractal antenna engineering has been primarily focused in two areas: the first deals with the analysis and design of fractal antenna elements, and the second concerns the application of Fractal concepts to the design of antenna arrays as discussed by the authors.
Abstract: Recent efforts by several researchers around the world to combine fractal geometry with electromagnetic theory have led to a plethora of new and innovative antenna designs. In this report, we provide a comprehensive overview of recent developments in the rapidly growing field of fractal antenna engineering. Fractal antenna engineering research has been primarily focused in two areas: the first deals with the analysis and design of fractal antenna elements, and the second concerns the application of fractal concepts to the design of antenna arrays. Fractals have no characteristic size, and are generally composed of many copies of themselves at different scales. These unique properties of fractals have been exploited in order to develop a new class of antenna-element designs that are multi-band and/or compact in size. On the other hand, fractal arrays are a subset of thinned arrays, and have been shown to possess several highly desirable properties, including multi-band performance, low sidelobe levels, and the ability to develop rapid beamforming algorithms based on the recursive nature of fractals. Fractal elements and arrays are also ideal candidates for use in reconfigurable systems. Finally, we provide a brief summary of recent work in the related area of fractal frequency-selective surfaces.

1,055 citations

Journal ArticleDOI
TL;DR: The memory properties of various materials and systems which appear most strikingly in their non-trivial, time-dependent resistive, capacitative and inductive characteristics are described within the framework of memristors, memcapacitors and meminductors.
Abstract: Memory effects are ubiquitous in nature and are particularly relevant at the nanoscale where the dynamical properties of electrons and ions strongly depend on the history of the system, at least within certain time scales. We review here the memory properties of various materials and systems which appear most strikingly in their non-trivial, time-dependent resistive, capacitative and inductive characteristics. We describe these characteristics within the framework of memristors, memcapacitors and meminductors, namely memory-circuit elements with properties that depend on the history and state of the system. We examine basic issues related to such systems and critically report on both theoretical and experimental progress in understanding their functionalities. We also discuss possible applications of memory effects in various areas of science and technology ranging from digital to analog electronics, biologically inspired circuits and learning. We finally discuss future research opportunities in the field.

667 citations

Journal ArticleDOI
TL;DR: In this paper, a metamaterial paradigm for achieving an efficient, electrically small antenna is introduced Spherical shells of homogenous, isotropic negative permittivity (ENG) material are designed to create a resonant system for several antennas: an infinitesimal electric dipole, a very short center-fed cylindrical electric dipoles, and a coaxially-fed electric monopole over an infinite ground plane.
Abstract: A metamaterial paradigm for achieving an efficient, electrically small antenna is introduced Spherical shells of homogenous, isotropic negative permittivity (ENG) material are designed to create electrically small resonant systems for several antennas: an infinitesimal electric dipole, a very short center-fed cylindrical electric dipole, and a very short coaxially-fed electric monopole over an infinite ground plane Analytical and numerical models demonstrate that a properly designed ENG shell provides a distributed inductive element resonantly matched to these highly capacitive electrically small antennas, ie, an ENG shell can be designed to produce an electrically small system with a zero input reactance and an input resistance that is matched to a specified source resistance leading to overall efficiencies approaching unity Losses and dispersion characteristics of the ENG materials are also included in the analytical models Finite element numerical models of the various antenna-ENG shell systems are developed and used to predict their input impedances These electrically small antenna-ENG shell systems with idealized dispersionless ENG material properties are shown to be very efficient and to have fractional bandwidths above the values associated with the Chu limit for the quality factor without any degradation in the radiation patterns of the antennas Introducing dispersion and losses into the analytical models, the resulting bandwidths are shown to be reduced significantly, but remain slightly above (below) the corresponding Chu-based value for an energy-based limiting (Drude) dispersion model of the permittivity of the ENG shell

519 citations

Patent
03 Jul 2002
TL;DR: In this paper, a vehicle diagnostic system which diagnoses the state of the vehicle or the states of a component of a vehicle and generates an output indicative or representative thereof is presented. But it is not shown how to generate the output of the diagnostic system.
Abstract: Vehicle diagnostic system which diagnoses the state of the vehicle or the state of a component of the vehicle and generates an output indicative or representative thereof. A communications device transmits the output of the diagnostic system to a remote location, possibly via a satellite or the Internet. The diagnostic system can include sensors mounted on the vehicle, each providing a measurement related to a state of the sensor or a measurement related to a state of the mounting location, and a processor coupled to the sensors and arranged to receive data from the sensors and process the data to generate the output indicative or representative of the state of the vehicle or its component. The processor may embody a pattern recognition algorithm trained to generate the output from the data received from the sensors and be arranged to control parts of the vehicle based on the output.

446 citations

Journal ArticleDOI
TL;DR: In this paper, the pull-in instability in microelectromechanical (MEMS) resonators was studied and the authors proposed a low-voltage MEMS RF switch actuated with a combined DC and AC loading, which uses a voltage much lower than the traditionally used DC voltage.
Abstract: We study the pull-in instability in microelectromechanical (MEMS) resonators and find that characteristics of the pull-in phenomenon in the presence of AC loads differ from those under purely DC loads. We analyze this phenomenon, dubbed dynamic pull-in, and formulate safety criteria for the design of MEMS resonant sensors and filters excited near one of their natural frequencies. We also utilize this phenomenon to design a low-voltage MEMS RF switch actuated with a combined DC and AC loading. The new switch uses a voltage much lower than the traditionally used DC voltage. Either the frequency or the amplitude of the AC loading can be adjusted to reduce the driving voltage and switching time. The new actuation method has the potential of solving the problem of high driving voltages of RF MEMS switches.

421 citations