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guided-waves
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Polynomial expansion for extraction of eigenmodes in layered waveguides
, Article Aplications of Photonic Technology, Quebec City, 1 June 2002 through 6 June 2002 ; Volume 4833 , 2002 , Pages 769-775 ; 0277786X (ISSN) ; Rashidian, B ; Sharif University of Technology
2002
Abstract
In this article, polynomial expansion approach for extraction of guided and leaky modes in layered waveguides in which loss and gain can be present simultaneously is proposed. To verify the method, results of analysis of a typical test case have been compared to the other references, proving a good agreement. Polynomial expansion is a nonharmonic expansion and does not involve harmonic functions or intrinsic modes of homogenous layers. This approach has the benefit of leading to algebraic dispersion equations rather than transcendental dispersion equation; therefore, it will be easier to solve compared with other methods such as argument principle method (APM), reflection pole method (RPM)...
THz plasmonic devices based on an array of metallic posts in a parallel-plate waveguide
, Article International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, Mainz ; 2013 ; 21622027 (ISSN) ; 9781467347174 (ISBN) ; Shahabadi, M ; Altmann, K ; Sharif University of Technology
2013
Abstract
An array of metallic posts sandwiched between two parallel metal plates supports highly-confined surface waves that can be regarded as spoof surface plasmons. This structure which is called the parallel-plate ladder waveguide (PPLWG) can be used for implementing THz guided-wave devices. In this paper, the effect of post shapes on waveguiding characteristics of PPLWG is analyzed and realization of certain devices such as couplers using the proposed structure is investigated
Fatigue damage detection in large thin wall plate based on ultrasonic guided wave by using a piezoelectric sensor network
, Article 29th Congress of the International Council of the Aeronautical Sciences, ICAS 2014 ; 2014 ; Abedian, A ; Sharif University of Technology
Abstract
Today, structural Health monitoring is a major concern in the engineering community. Multisite fatigue damage, hidden cracks and corrosion in hard-to-reach locations are among the major flaws encountered in today's extensive diagnosis and/or prognosis of aircraft structures. Ultrasonic waves, lamb waves are particularly advantageous because of their propagation at large distances with little damp in thin-wall structures. In this paper a new rectangular shape array of embedded piezoelectric sensors is developed to detect some damages in large planar structures. An artificial neural network is trained to identify the damage state and its location. Output signals of each sensor due to various...
Design and Fabrication of a 16-Way Ultra-Wideband Spatial Power Divider/Combiner
, M.Sc. Thesis Sharif University of Technology ; Banai, Ali (Supervisor)
Abstract
High power, broadband amplifiers at microwave and millimeter wave frequencies are needed for military and civilian applications. High power, broadband, high linearity, low noise, high efficiency and graceful degradation on failure are among the most important features in amplifier design. Solid state and vacuum tube devices have many disadvantages. A promising solution has been spatial power combining technique. Spatial power combining is a method of coherently combining the power of many amplifying devices using free space as the power dividing/combining medium within a guided wave structure in contrast to traditional circuit based amplifiers. This thesis presents the design and fabrication...
Analysis and simulation of ring resonator silicon electro-optic modulators based on PN junction in reverse bias
, Article Optical Engineering ; Vol. 53, issue. 12 , 2014 ; ISSN: 00913286 ; Akbari, M ; Sharif University of Technology
Abstract
The theory of silicon optical modulators of ring resonators based on PN diode in reverse bias is primarily discussed. It secondarily provides a full-featured simulator to investigate the behavior of such modulators. Wave equation for ring structure will be solved by using the conformal transformation method and the matrix method as it was used to analyze bent planar optical waveguides. Power coupling between ring and straight waveguides will be calculated by coupled theory of nonparallel waveguides based on experimental results. The time response demonstrates the capability of this device to operate correctly at up to 10 Gbs-1 bitrate, and the frequency spectrum analysis of device shows a >...
Inastantaneous baseline multiple damage detection and localization in an aluminum plate using Lamb waves
, Article 30th Congress of the International Council of the Aeronautical Sciences, 25 September 2016 through 30 September 2016 ; 2016 ; 9783932182853 (ISBN) ; Abedian, A ; Nasiri, M ; Sharif University of Technology
International Council of the Aeronautical Sciences
Abstract
In recent years, new Structural Health Monitoring (SHM) methodologies with a concept of "instantaneous baseline damage detection" are being developed by many researchers. In this context, this paper uses a new method to identify multiple damage in the aluminum plate. For this goal use from spars PZWS sensor network to generate and received guided waves. Ultrasonic waves are generated and measured from all possible different pairs of excitation and sensing transducers. For feature extraction of received signals used from continues wavelet transform. A probabilistic damage diagnostic algorithm based on correlation analysis was investigated to locate single or multiple damages. In this study,...
Optimization and simulation of micrometre-scale ring resonator modulators based on p-i-n diodes using firefly algorithm
, Article Optik ; Volume 128 , 2017 , Pages 101-112 ; 00304026 (ISSN) ; Akbari, M ; Sharif University of Technology
Elsevier GmbH
2017
Abstract
Field analysis of ring resonator modulators based on p-i-n diodes has been dissected in this paper. This analysis is performed in time and frequency domains. The conformal transformation method has been used for solving 3-D wave equation. Coupling coefficient between the ring and straight waveguides are obtained by developing the coupled-mode assumption. In the resonant wavelength of 1573.91 nm, a drop of more than 15 dB in frequency spectrum of the device has been observed. Time domain simulation shows that this modulator could support up to 0.4 Gb/s and up to 1.5 Gb/s for NRZ and RZ signals, respectively. Obtained simulation results in both domains have been properly complied with...