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Input impedance and radiation pattern of a resonant dipole embedded in a two-dimensional periodic leaky-wave structure

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IET MICROWAVES ANTENNAS & PROPAGATION 2015年第14期9卷 1567-1573页

作者： Bakhtafrouz, Ahmad Borji, Amir Isfahan Univ Technol Dept Elect & Comp Engn Esfahan *** Iran Sharif Univ Technol Dept Elect Engn Tehran *** Iran

array scanning method (ASM) is employed to study the input impedance and radiation pattern of a two-dimensional periodic leaky-wave antenna (LWA). The antenna consists of a narrow horizontal strip dipole of arbitrary length underneath a two-dimensional (2d) periodic screen of metallic patches, which acts as a partially reflective surface (PRS), and backed by a ground plane. First, the Green's function in the presence of the 2d array of metallic patches is calculated by means of the ASM and then the current distribution and input impedance of the source dipole are calculated through the electric field integral equation and method of moments. The far-field pattern is computed using the reciprocity theorem. Compared to the Hertzian dipole, which is the only type of source that has been considered in the literature, the resonant dipole substantially improves the performance of periodic LWA in terms of radiated power, efficiency and bandwidth. Numerical results are given for a resonant dipole over the frequency range of 60-70 GHz and compared with those obtained from commercial softwares, FEKO (R) and Ansys HFSS (R), showing an excellent agreement with considerable improvement in terms of memory usage and computational speed.

关键词： leaky wave antennas antenna radiation patterns dipole antenna arrays millimetre wave antenna arrays Green's function methods electric field integral equations method of moments input impedance radiation pattern resonant dipole two-dimensional periodic leaky-wave structure array scanning method ASM two-dimensional periodic LWA narrow-horizontal strip dipole arbitrary length 2d periodic screen two-dimensional periodic screen metallic patches partially reflective surface PRS ground plane Green function 2d array source dipole electric field integral equation method-of-moments far-field pattern reciprocity theorem Hertzian dipole radiated power FEKO software HFSS software frequency 60 GHz to 70 GHz

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Integrated Circuits for Volumetric Ultrasound Imaging With 2-d CMUT arrays

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IEEE TRANSACTIONS ON BIOMEdICAL CIRCUITS ANd SYSTEMS 2013年第6期7卷 796-804页

作者： Bhuyan, Anshuman Choe, Jung Woo Lee, Byung Chul Wygant, Ira O. Nikoozadeh, Amin Oralkan, Omer Khuri-Yakub, Butrus T. Stanford Univ Edward L Ginzton Lab Stanford CA 94305 USA Texas Instruments Inc Sunnyvale CA 94089 USA N Carolina State Univ Dept Elect Engn Raleigh NC 27606 USA

Real-time volumetric ultrasound imaging systems require transmit and receive circuitry to generate ultrasound beams and process received echo signals. The complexity of building such a system is high due to requirement of the front-end electronics needing to be very close to the transducer. A large number of elements also need to be interfaced to the back-end system and image processing of a large dataset could affect the imaging volume rate. In this work, we present a 3-d imaging system using capacitive micromachined ultrasonic transducer (CMUT) technology that addresses many of the challenges in building such a system. We demonstrate two approaches in integrating the transducer and the front-end electronics. The transducer is a 5-MHz CMUT array with an 8 mm x 8 mm aperture size. The aperture consists of 1024 elements (32 x 32) with an element pitch of 250 mu m. An integrated circuit (IC) consists of a transmit beamformer and receive circuitry to improve the noise performance of the overall system. The assembly was interfaced with an FPGA and a back-end system (comprising of a data acquisition system and PC). The FPGA provided the digital I/O signals for the IC and the back-end system was used to process the received RF echo data (from the IC) and reconstruct the volume image using a phased array imaging approach. Imaging experiments were performed using wire and spring targets, a ventricle model and a human prostrate. Real-time volumetric images were captured at 5 volumes per second and are presented in this paper.

关键词： 2d array capacitive micromachined ultrasonic transducer (CMUT) flip-chip bonding integrated circuits phased array imaging ultrasound volumetric imaging

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Spatial and force dependency of mechanomyographic signal features

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JOURNAL OF NEUROSCIENCE METHOdS 2006年第1期158卷 89-99页

作者： Madeleine, Pascal Cescon, Corrado Farina, dario Univ Aalborg Dept Hlth Sci & Technol Ctr Sensory Motor Interact DK-9220 Aalborg Denmark Politecn Torino Lab Ingn Sistema Neuromuscolare Turin Italy

The aim was to investigate with a novel technique the spatial inhomogeneity in surface mechanomyographic (MMG) response to muscle contraction at varying force levels. MMG signals were detected over the dominant tibialis anterior muscle of 10 volunteers using a 5 x 3 grid of accelerometers. The subjects performed. 3 s long isometric contractions at forces ranging from 0% to 100% of the maximal force (10% increment) in a randomised order. From the two-dimensional MMG recordings, maps of absolute and normalized temporal and spectral MMG descriptors were obtained. The centroid and entropy of these maps were computed to describe the spatial centre of activity and degree of homogeneity, respectively. MMG absolute amplitude did not depend on location over the muscle while normalized amplitude did and the centroid shifted with increasing force. Amplitude increased with force and its entropy decreased. Absolute and normalized spectral variables depended on location over the muscle and their centroid shifted with increasing force. In addition, the dependency of absolute and normalized spectral variables on force was affected by location. These results highlight limitations when using single-channel MMG features for the assessment of motor unit control strategies, due to a substantial effect of position on the relation between force and MMG characteristics. (c) 2006 Elsevier B.V. All rights reserved.

关键词： 2d array mechanomyography accelerometer tibialis anterior muscle

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Well-ordered arranging of Ag nanoparticles in SiO₂/Si by ion implantation

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APPLIEd SURFACE SCIENCE 2012年第19期258卷 7322-7326页

作者： Takahiro, K. Minakuchi, Y. Kawaguchi, K. Isshiki, T. Nishio, K. Sasase, M. Yamamoto, S. Nishiyama, F. Kyoto Inst Technol Dept Chem & Mat Technol Sakyo Ku Kyoto 6068585 Japan Kyoto Inst Technol Dept Math & Phys Sci Sakyo Ku Kyoto 6068585 Japan Wakasa Wan Energy Res Ctr Tsuruga Fukui 9140192 Japan Japan Atom Energy Agcy Quantum Beam Sci Directorate Takasaki Gunma 3701292 Japan Hiroshima Univ Grad Sch Engn Higashihiroshima Hiroshima 7398527 Japan

Well-ordered arrangements of Ag nanoparticles have been found for Ag-implanted SiO2 at depths corresponding to the projected range and end of range of Ag ions. Thermally grown SiO2 films of 300 nm thick on Si were implanted with 350 keV-Ag ions to fluences of 0.37-1.2 x 1017 ions/cm(2) at a current density about 4 mu A/cm(2). Cross-sectional transmission electron microscopy and scanning transmission electron microscopy reveal the presence of a two-dimensional array of Ag nanoparticles of 25-40 nm in diameter located at a depth of similar to 130 nm, together with the self-organization of delta-layer of tiny Ag nanoparticles aligned along the SiO2/Si interface. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRd) confirm the stability of these Ag nanoparticles against oxidation and sulfidation when stored in ambient air for 19-21 months. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Ion implantation Nanoparticle 2d array Interface delta-Layer Oxidation Sulfidation

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SURFACE EMITTING LASER arrayS WITH UNIFORMLY SEPARATEd WAVELENGTHS

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ELECTRONICS LETTERS 1990年第13期26卷 940-942页

作者： CHANGHASNAIN, CJ MAEdA, MW STOFFEL, NG HARBISON, JP FLOREZ, LT JEWELL, J AT&T BELL LABS HOLMDELNJ 07733

A novel and simple scheme used to achieve a 2-d array of monolithic multiple wavelength lasers is reported. Uniformly separated wavelengths are emitted from an eight-element linear array and an 8*8 2d array of surface... 详细信息

关键词： 2d array 950 nm Bragg reflectors dBR type distributed Bragg reflector lasers eight-element linear array integrated optics laser arrays laser transitions monolithic multiple wavelength lasers semiconductor junction lasers semiconductor lasers surface emitting lasers two dimensional array uniformly separated wavelengths vertical cavity type

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Single photon avalanche diodes:: Towards the large bidimensional arrays

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SENSORS 2008年第8期8卷 4636-4655页

作者： Privitera, Simona Tudisco, Salvatore Lanzano, Luca Musumeci, Francesco Pluchino, Alessandro Scordino, Agata Campisi, Angelo Cosentino, Luigi Finocchiaro, Paolo Condorelli, Giovanni Mazzillo, Massimo Lombardo, Salvo Sciacca, Emilio Ist Nazl Fis Nucl Lab Nazl Sud I-95125 Catania Italy Univ Catania DMFCI Dip Met Chim Fis Ing I-95125 Catania Italy Univ Catania Dip Fis Astron I-95125 Catania Italy ST Microelect R&D I-95100 Catania Italy IMM CNR I-95100 Catania Italy

Single photon detection is one of the most challenging goals of photonics. In recent years, the study of ultra-fast and/or low-intensity phenomena has received renewed attention from the academic and industrial communities. Intense research activity has been focused on bio-imaging applications, bio-luminescence, bio-scattering methods, and, more in general, on several applications requiring high speed operation and high timing resolution. In this paper we present design and characterization of bi-dimensional arrays of a next generation of single photon avalanche diodes (SPAds). Single photon sensitivity, dark noise, afterpulsing and timing resolution of the single SPAd have been examined in several experimental conditions. Moreover, the effects arising from their integration and the read-out mode have also been deeply investigated.

关键词： single photon avalanche photodiode silicon photomultiplier photon detection efficiency timing afterpulsing cross-talk 2d array

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Ultrasonic transducers for medical diagnostic imaging

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BIOMEdICAL ENGINEERING LETTERS 2017年第2期7卷 91-97页

作者： Lee, Wonseok Roh, Yongrae Alpin Med Syst Co Ltd Probe Dev Team Seoul South Korea Kyungpook Natl Univ Sch Mech Engn Daegu South Korea

Over the past decades, ultrasound imaging technology has made tremendous progress in obtaining important diagnostic information from patients in a rapid, noninvasive manner. Although the technology has benefited from sophisticated signal processing technology and imaging system integration, much of this progress has been derived from the development of ultrasonic transducers that are in direct contact with patients. An overview of medical ultrasonic imaging transducers is presented in this review that describes their structure, types, and application fields. The structural components of a typical transducer are presented in detail including an active layer, acoustic matching layers, a backing block, an acoustic lens, and kerfs. The types of transducers are classified according to the dimensions of ultrasound images: one-dimensional array, mechanical wobbling, and two-dimensional array transducers. Advantages of each transducer over the other and the technical issues for further performance enhancement are described. Application of the transducers to various clinical imaging fields is also reviewed.

关键词： Ultrasonic transducer Ultrasound image 1d array Mechanical wobbling transducer 2d array

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A two-dimensional array of tunnel junctions used for Coulomb blockade thermometry

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PHYSICA B 2000年第PART II期284卷 1788-1789页

作者： Bergsten, T Claeson, T delsing, P Chalmers Univ Technol SE-41296 Gothenburg Sweden Univ Gothenburg Dept Microelect & Nanosci SE-41296 Gothenburg Sweden

We have measured current-voltage characteristics of a two-dimensional array of small tunnel junctions at temperatures from 1.4 to 4.2 K. This corresponds to thermal energies larger than the charging energy. We show that 2d-arrays can be used as primary thermometers in the same way as 1d-arrays, and have several advantages over 1d-arrays. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： 2d array Coulomb blockade primary thermometer

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Electrical, thermal and optomechanical packaging of large 2d optoelectronic device arrays for free-space optical interconnects

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JOURNAL OF OPTICS A-PURE ANd APPLIEd OPTICS 1999年第2期1卷 267-271页

作者： Ayliffe, MH Kabal, d Lacroix, F Bernier, E Khurana, P Kirk, AG Tooley, FAP Plant, dV McGill Univ Photon Syst Grp Dept Elect & Comp Engn Montreal PQ H3A 2A7 Canada

Innovative approaches to the design of a high-performance package module accommodating a 32 x 32 array of surface-active devices indium bump bonded to a 8 x 8 mm(2) VLSI chip are presented. Electrical, thermal and optomechanical design considerations are discussed and experimental performance results of a prototype implementation are described. The package module supports 139 impedance-controlled signal connections as well as active temperature stabilization of the optoelectronic VLSI chip. The package module is compact, simple to assemble, alignment-tolerant and can be passively inserted into a free-space optical system with no need for further adjustments.

关键词： optoelectronic packaging free-space optical interconnect 2d array passive alignment optomechanics

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A Novel 24 GHz One-Shot, Rapid and Portable Microwave Imaging System

A Novel 24 GHz One-Shot, Rapid and Portable Microwave Imagin...

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25th IEEE Instrumentation and Measurement Technology Conference

作者： Ghasr, M. T. Abou-Khousa, M. A. Kharkovsky, S. Zoughi, R. Pommerenke, d. Missouri Univ Sci & Technol Dept Elect & Comp Engn AMNTL Rolla MO 65409 USA Missouri Univ Sci & Technol Dept Elect & Comp Engn Electromagnet Compatibil Lab Rolla MO 65409 USA

ISBN: (纸本)9781424415403

development of microwave and millimeter wave imaging systems has received significant attention in the past decade. Signals at these frequencies penetrate imide of dielectric Materials and have relatively small wavelengths. Thus, imaging systems at these frequencies can produce images of the dielectric and geometrical distributions of objects. Although there are many different approaches for imaging of these frequencies, they each have their respective advantageous and limiting features (hardware, reconstruction algorithms). One method involves electronically scanning a given spatial domain while recording the coherent scattered field distribution from an object. Consequently, different reconstruction or imaging techniques may be used to produce an image (dielectric distribution and geometrical features) of the object. The ability to perform this accurately and fast can lead to the development of a rapid imaging system that can be used in the same manner as a video camera This paper describes the design of such a system, operating at 24 GHz, using modulated scatterer technique applied to 30 resonant slots in a prescribed measurement domain.

关键词： electric field distribution modulated scatterer technique resonant slots 2d array microwave imaging

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