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2011-11-05
PIER
Vol. 121, 535-555, 2011
download: 143
Automated SAR Reference Image Preparation for Navigation
Sanhai Ren Wenge Chang Tian Jin Zibin Wang
The preparation of good navigational synthetic aperture radar (SAR) reference image is critical to the SAR scene matching aided navigation system, especially for complex terrain. However, few papers discuss the problem, and almost none of the methods proposed by them are fully automatic. Based on the practical requirements, a fully automated method of SAR reference image preparation is introduced. Firstly, a number of distinctive control points (CP) in the simulated SAR image is detected based on a method of image segmentation and clustering. Then, the corresponding tie-points in the real SAR image are searched based on local similarity by means of template matching. To improve the accuracy of CP, a method for segmentation threshold calculation, outlier screening and sub-pixel location computation is presented. Finally, the real SAR image is warped to the simulated one, and then projected to the frame of digital elevation model (DEM) by the polynomial mapping function. Experimental results on real data sets demonstrate the accuracy and efficiency of the proposed method.
AUTOMATED SAR REFERENCE IMAGE PREPARATION FOR NAVIGATION
2011-11-05
PIER
Vol. 121, 521-534, 2011
download: 126
Implicit Boundary Conditions in Transformation-Optics Cloaking for Electromagneticwaves
Xudong Chen
The paper studies boundary conditions in transformation-optics cloaking for two and three dimensional electromagnetic waves. Implicit boundary conditions for these two cases are derived, no matter if the source is placed in the interior or exterior of the cloak layer. More importantly, the two implicit boundary conditions are derived without solving Mie scattering problems, and these conditions are characteristics of the clock-air interface. In particular, the implicit boundary condition for two-dimensional electromagnetic wave case is reported for the first time. In addition, a sensor can be cloaked in two-dimensional electromagnetic waves, i.e., waves can penetrate into the interior of the cloak layer without exterior scattering.
2011-11-04
PIER
Vol. 121, 505-520, 2011
download: 174
Parallel Implementation of MLFMA for Homogeneous Objects with Various Material Properties
Ozgur Ergul
We present a parallel implementation of the multilevel fast multipole algorithm (MLFMA) for fast and accurate solutions of electromagnetics problems involving homogeneous objects with diverse material properties. Problems are formulated rigorously with the electric and magnetic current combined-field integral equation~(JMCFIE) and solved iteratively using MLFMA parallelized with the hierarchical partitioning strategy. Accuracy and efficiency of the resulting implementation are demonstrated on canonical problems involving perfectly conducting, lossless dielectric, lossy dielectric, and double-negative spheres.
PARALLEL IMPLEMENTATION OF MLFMA FOR HOMOGENEOUS OBJECTS WITH VARIOUS MATERIAL PROPERTIES
2011-11-04
PIER
Vol. 121, 485-504, 2011
download: 165
Time Domain Analytical Modeling of a Straight Thin Wire Buried in a Lossy Medium
Silvestar Sesnic Dragan Poljak Sergey V. Tkachenko
This paper deals with an analytical solution of the time domain Pocklington equation for a straight thin wire of finite length, buried in a lossy half-space and excited via the electromagnetic pulse (EMP) excitation. Presence of the earth-air interface is taken into account via the simplified reflection coefficient arising from the Modified Image Theory (MIT). The analytical solution is carried out using the Laplace transform and the Cauchy residue theorem. The EMP excitation is treated via numerical convolution. The obtained analytical results are compared to those calculated using the numerical solution of the frequency domain Pocklington equation combined with the Inverse Fast Fourier Transform (IFFT).
TIME DOMAIN ANALYTICAL MODELING OF A STRAIGHT THIN WIRE BURIED IN A LOSSY MEDIUM
2011-11-04
PIER
Vol. 121, 469-484, 2011
download: 135
Concentration of the Specific Absorption Rate Around Deep Brain Stimulation Electrodes During MRI
Syed Mohsin
During Magnetic Resonance Imaging (MRI), the presence of an implant such as a Deep Brain Stimulation (DBS) lead in a patient's body can pose a significant risk. This is due to the fact that the MR radiofrequency (RF) field can achieve a very high strength around the DBS electrodes. Thus the specific absorption rate (SAR), which is proportional to the square of the magnitude of the RF electric field, can have a very high concentration in the near-field region of the electrodes. The resulting tissue heating can reach dangerous levels. The degree of heating depends on the level of SAR concentration. The effects can be severe, leading to tissue ablation and brain damage, and significant safety concerns arise whenever a patient with an implanted DBS lead is exposed to MR scanning. In this paper, SAR, electric field, and temperature rise distributions have been found around actual DBS electrodes. The magnitude and spatial distribution of the induced temperature rises are found to be a function of the length and structure of the lead device, tissue properties and the MR stimulation parameters.
CONCENTRATION OF THE SPECIFIC ABSORPTION RATE AROUND DEEP BRAIN STIMULATION ELECTRODES DURING MRI
2011-11-04
PIER
Vol. 121, 453-468, 2011
download: 141
Polarization Characteristics of a Partially Coherent Gaussian Schell-Model Beam in Slant Atmospheric Turbulence
Ya Qing Li Zhen-Sen Wu Li Guo Wang
On the basis of the extended Huygens-Fresnel principle, the cross-spectral density matrix (CSDM) of partially coherent Gaussian Schell-model (GSM) beams in the slant atmospheric turbulence is derived. Given that the light emitted from a transmitter is elliptically polarized light, the degree of polarization (DoP) of the partially coherent GSM beams is represented by Stokes parameters expressed by the elements of the CSDM. The expressions of the orientation angle, polarized light intensity in the major axis are derived and the numerical results are presented. Depolarization theory is studied using a Mueller matrix and the depolarization index (DI) is obtained to describe the depolarized state of the partially coherent GSM beams propagating in the slant atmospheric turbulence. Results show that the DOP and DI of the beam tend to their initial value in the long-range propagation.
POLARIZATION CHARACTERISTICS OF A PARTIALLY COHERENT GAUSSIAN SCHELL-MODEL BEAM IN SLANT ATMOSPHERIC TURBULENCE
2011-11-03
PIER
Vol. 121, 433-452, 2011
download: 131
Optical Response of a Perfect Conductor Waveguide That Behaves as a Photonic Crystal
Alberto Mendoza-Suarez Hector Perez-Aguilar Francisco Villa-Villa
In this work, we consider a waveguide composed of two periodic, perfectly conducting, one-dimensional rough surfaces. This periodic system has a band structure similar in some aspects to a one-dimensional photonic crystal. However, our system has some additional interesting features. We calculate the band structure and the reflectivity of a corresponding finite waveguide. We found that the variation of the roughness amplitude and the relative phases allow to control at a certain degree the band structure of the system. Particularly, wide gaps can be obtained. It is even possible to obtain discrete modes for some frequency range and then the periodic waveguide acts as an unimodal filter. The system considered constitutes itself a photonic crystal whose band structure corresponds in many ways to a conventional photonic crystal but using just a single material. The key properties of this system are that it really constitutes a waveguide whose optical response is similar to that of a one-dimensional photonic crystal.
OPTICAL RESPONSE OF A PERFECT CONDUCTOR WAVEGUIDE THAT BEHAVES AS A PHOTONIC CRYSTAL
2011-11-02
PIER
Vol. 121, 409-431, 2011
download: 170
3D Bistatic Omega-k Imaging Algorithm for Near Range Microwave Imaging Systems with Bistatic Planar Scanning Geometry
Yaolong Qi Weixian Tan Yanping Wang Wen Hong Yirong Wu
By introducing bistatic geometry to near range microwave imaging systems, this paper proposes a near range three dimensional (3D) bistatic imaging geometry based on planar scanning aperture and establishes corresponding echo model. Then, the paper deduces the 3D bistatic Omega-K imaging algorithm based on implicit spectral decomposition, in which the impacts of residual phase, including position displacement, range, azimuth and elevation defocusing, are analyzed and compensated. Finally, the 3D bistatic imaging geometry and algorithm are investigated and verified via numerical simulations and experiments using a near range imaging system.
3D BISTATIC OMEGA-K IMAGING ALGORITHM FOR NEAR RANGE MICROWAVE IMAGING SYSTEMS WITH BISTATIC PLANAR SCANNING GEOMETRY
2011-11-02
PIER
Vol. 121, 391-408, 2011
download: 129
Time-Domain Iterative Physical Optics Method for Analysis of EM Scattering from the Target Half Buried in Rough Surface: PEC Case
Jie Li Bing Wei Qiong He Li-Xin Guo De-Biao Ge
In this paper, time-domain physical optics (TDPO) method is extended to its iterative version (TDIPO) to consider the coupling effects between two regions, and the latter is employed to investigate electromagnetic scattering from three dimensional target half-buried by a two dimensional rough surface. By using iterative scheme, more accurate transient response reflected from combinative target with multi-scattering effects would be obtained than that by using TDPO alone. The TDIPO could also be enhanced by time-domain equivalent edge current (TDEEC) to further determine the far-field characteristics of the combinative target with rough surface. An accurate composite geometry model technique which combines 2D perfectly electrically conducting (PEC) rough surface and half-buried 3D PEC target is introduced and employed to assist the meshing work. The validity of the presented method is verified by comparing the scattering results for dihedral targets with those obtained through TDPO and finite difference in time domain (FDTD), as well as multi-level fast multiple algorithm (MLFMA). Then simulations of EM scattering from the target embedded in rough surface for different incidence directions are carried out to test the availability of TDIPO/EEC. Discussions on the effects of incidence direction and the presence of the target on the backscattering in far-zone are also given.
TIME-DOMAIN ITERATIVE PHYSICAL OPTICS METHOD FOR ANALYSIS OF EM SCATTERING FROM THE TARGET HALF BURIED IN ROUGH SURFACE: PEC CASE
2011-11-01
PIER
Vol. 121, 381-389, 2011
download: 144
Ultrathin Cylindrical Cloak
Jingjing Zhang Niels Asger Mortensen
We propose a cylindrical invisibility cloak achieved utilizing two dimensional split-ring resonator structured metamaterials at microwave frequencies. The cloak has spatially uniform parameters in the axial direction, and can work very well even when the cloak shell is very thin compared with the concealed object and the working wavelength. Numerical simulation is performed to verify the functionality of the cloak, where the cloak layer is only around 1/4 of the operating wavelength. Our work provides a feasible solution to the experimental realization of cloaks with ideal parameters.
ULTRATHIN CYLINDRICAL CLOAK
2011-11-01
PIER
Vol. 121, 365-379, 2011
download: 105
Miniaturization Design of Full Differential Bandpass Filter with Coupled Resonators Using Embedded Passive Device Technology
Sung-Mao Wu Chun-Ting Kuo Pei-Yu Lyu Yu Li Shen Ching-I Chien
This paper presents two full differential bandpass filters with small occupied areas. Both filters are designed with the same basic structure which consists of two double coupled resonators with magnetic coupling. The resonators are stacked up and have the advantage of high coupling efficiency, reducing the area. Nevertheless, in the basic structure, the insertion loss in the high stopband is above -10 dB and therefore does not meet the requirement for bandpass filter design. Thus, two solutions are introduced to form the proposed filters. The first one integrates the ground plane, while the second one makes the use of an extra transmission zero. With the help of these solutions, two types of full differential bandpass filters are implemented on an FR4 using the embedded passive device technology, with the additional purpose of being designed for SiP applications. The passband of the filters conforms to the WLAN IEEE 802.11a (5 GHz) standard. Most importantly, the occupied areas of the two proposed bandpass filters are only 6 mm х 6.7 mm and 6.6 mm х 8.3 mm respectively. Compared with previous research, area reductions of up to 98.05% and 97.76% can be achieved.
MINIATURIZATION DESIGN OF FULL DIFFERENTIAL BANDPASS FILTER WITH COUPLED RESONATORS USING EMBEDDED PASSIVE DEVICE TECHNOLOGY
2011-11-01
PIER
Vol. 121, 343-363, 2011
download: 118
Using Nanoparticles for Enhancing the Focusing Heating Effect of an External Waveguide Applicator for Oncology Hyperthermia: Evaluation in Muscle and Tumor Phantoms
Citlalli Jessica Trujillo-Romero Sonia Garcia-Jimeno Arturo Vera-Hernandez Lorenzo Leija-Salas Joan Estelrich
A technical challenge in hyperthermia therapy is to locally heat the tumor region up to an appropriate temperature to destroy cancerous cells, without damaging the surrounding healthy tissue. Magnetic fluid hyperthermia (MFH) is a novel, minimally invasive therapy aiming at concentrating heat inside cancerous tissues. This therapy is based on the injection of different superparamagnetic nanoparticles inside the tumor. In our study, superparamagnetic nanoparticles, which we developed and characterized, consisted of iron oxide nanoparticles stabilized with polyethylene glycol. Moreover, a new technique for MFH using a specially designed external electromagnetic waveguide as applicator is presented. Three magnetite concentrations were used for making the tumor phantoms, which were embedded in muscle phantoms. The phantoms were radiated and located at three different distances from the applicator. Furthermore, two volumes of tumor (2.5 mL and 5.0 mL) were assayed. Heating curves, as a function of time, allowed the establishment of a more appropriate nanoparticle concentration for obtaining the temperature increase suitable for hyperthermia therapy. The results shown in this paper confirm the feasibility of using nanoparticles as agents to focus the energy over the tumor, without creating hot spots in healthy tissue. In addition, the experiments validated that by using this applicator in combination with nanoparticles, it is also possible to locally control the increments of temperature in tissues.
USING NANOPARTICLES FOR ENHANCING THE FOCUSING HEATING EFFECT OF AN EXTERNAL WAVEGUIDE APPLICATOR FOR ONCOLOGY HYPERTHERMIA: EVALUATION IN MUSCLE AND TUMOR PHANTOMS
2011-10-31
PIER
Vol. 121, 317-342, 2011
download: 138
Rigorous Analysis of Electromagnetic Scattering by Cylindrical EBG Structures
Vakhtang Jandieri Kiyotoshi Yasumoto Young-Ki Cho
Cylindrical EBG structures excited by a Hertzian dipole source and TM polarized plane wave at oblique incidence are analyzed using a rigorous semi-analytical method based on the cylindrical Floquet mode expansion. Concentric and eccentric cylindrical EBG structures are investigated. Resonance and stopband characteristics in the transmission spectra of the cylindrical EBG structures, enhancement and shading effects in the excited fields, radiation patterns of Hertzian dipole located inside the cylindrical EBG structures in both H-plane and E-plane are numerically studied. Co-polarization and cross-polarizations scattering effects between the electric and magnetic fields are investigated at the oblique incidence of plane waves.
RIGOROUS ANALYSIS OF ELECTROMAGNETIC SCATTERING BY CYLINDRICAL EBG STRUCTURES
2011-10-27
PIER
Vol. 121, 301-315, 2011
download: 127
Optimal Design of Mfl Sensor for Detecting Broken Steel Strands in Overhead Power Line
Xingliang Jiang Yunfeng Xia Jianlin Hu Fanghui Yin Caixin Sun Ze Xiang
Aluminum conductor steel-reinforced (ACSR) cable is a specific type of stranded cable typically used for electrical power delivery. Steel strands in ACSR cable play a supportive role for overhead power line. Inspection timely is an important means to insure safety operation of power lines. As steel strands are wrapped in the center of ACSR cable, the common artificial inspection methods with optical instruments are limited to find inner flaws of power line. Recently, inspection of power line by robot with detectors is a method with good prospect. In this paper, the optimal design model of detector based on magnetic leakage flux (MLF) carried by robot for detecting broken steel strands in ACSR cables has been proposed. The optimal design model of MFL sensor is solved by niche genetic algorithm (NGA). Field experiment results show that the design method of the detector can be applied to different types of ACSR cables. The magnitude field induced by transmission current has nearly no influences on the detection of broken steel strands, and the developed detector carried by robot can identify broken steel strands with high reliability and sensitivity.
OPTIMAL DESIGN OF MFL SENSOR FOR DETECTING BROKEN STEEL STRANDS IN OVERHEAD POWER LINE
2011-10-27
PIER
Vol. 121, 281-299, 2011
download: 119
Interaction of an Asymmetric Scanning Near Field Optical Microscopy Probe with Fluorescent Molecules
Valeria Lotito Urs Sennhauser Christian V. Hafner Gian-Luca Bona
We present a numerical analysis of the interaction between novel scanning near field optical microscopy probes based on an asymmetric structure and a single fluorescent molecule. Our finite element analysis shows how such near field probes can be effectively used for high resolution detection of single molecules, in particular those with a longitudinal dipole moment. At the same time, fluorescent molecules can be exploited as point-like probes of the single vectorial components of the near field distribution at the probe apex, providing a powerful tool for near field probe characterization.
INTERACTION OF AN ASYMMETRIC SCANNING NEAR FIELD OPTICAL MICROSCOPY PROBE WITH FLUORESCENT MOLECULES
2011-10-27
PIER
Vol. 121, 271-279, 2011
download: 165
A Compact Bandstop Filter Based on Two Meandered Parallel-Coupled Lines
Dongnuan Cui Yuan'an Liu Yongle Wu Shulan Li Cuiping Yu
In this paper, a compact wideband high-rejection microstrip bandstop filter using two meandered parallel-coupled lines of different electrical lengths and characteristic impedances in shunt is presented. The transmission and reflection zeros of the filter can be controlled through analytical equations and rulers given. Using this signal interferences technology, this filter obtains a low insertion loss and sharp rejection. Bandwidth and rejection level of the filters of this bandstop filter can be designed by choosing different even- and odd-mode characteristic impedances values of the coupled lines. According to the transmission zeros number, two types of filters are shown in the paper. To validated this topology, a wideband bandstop filter with a 3 dB cutoff frequency bandwidth of 92% centered at 2.6 GHz with sharp rejection characteristics is built to verify the theoretical prediction. The measured frequency response of the filter agrees excellently with the predicted result.
A COMPACT BANDSTOP FILTER BASED ON TWO MEANDERED PARALLEL-COUPLED LINES
2011-10-26
PIER
Vol. 121, 249-269, 2011
download: 130
Integral-Equation Analysis of Frequency Selective Surfaces Using Ewald Transformation and Lattice Symmetry
Jianxun Su Xiao-Wen Xu Mang He Kang Zhang
In this paper, we present the space-domain integral-equation method for the analysis of frequency selective surfaces (FSS), consisting of an array of periodic metallic patches or a metal screens perforated periodically with arbitrarily shaped apertures. The computation of the spatial domain Green's function is accelerated by the Ewald transformation. The geometric model is simplified by the lattice symmetry, so that the unknowns are greatly reduced. Time of filling MOM matrix and solving linear system is dramatically reduced. Our technique shows much higher efficiency when compared with the available commercial software and the existing methods published.
INTEGRAL-EQUATION ANALYSIS OF FREQUENCY SELECTIVE SURFACES USING EWALD TRANSFORMATION AND LATTICE SYMMETRY
2011-10-25
PIER
Vol. 121, 225-247, 2011
download: 190
Signal Constellation Distortion and BER Degradation Due to Hardware Impairments in Six-Port Receivers with Analog I/Q Generation
Alvaro Moscoso-Martir Inigo Molina-Fernandez Alejandro Ortega-Monux
Since its introduction in 1994 direct conversion six-port receivers have attracted a considerable attention at microwave frequencies, with most recent work focusing on the so called six-port receivers with analog $I/Q$ generation. Besides its applications at microwave frequencies, six-port receivers with I/Q regeneration play a crucial role in the optical communications field, as they are the most promising candidates for optical coherent receivers that are being developed for 100 Gigabit Ethernet transceivers. In this paper we analytically model the influence of six-port junction hardware impairments on receiver performance. New analytical expressions are developed which give geometrical interpretation of signal constellation distortion due to hardware impairments and allow for the definition of several interesting figures of merit. Closed formulas are also proposed to analytically calculate BER degradation, under AWGN conditions, from these figures of merit. Finally, the proposed formulas are validated by means of simulation, and it is shown that they can be of practical interest to set the specifications of the six-port junction components.
SIGNAL CONSTELLATION DISTORTION AND BER DEGRADATION DUE TO HARDWARE IMPAIRMENTS IN SIX-PORT RECEIVERS WITH ANALOG I/Q GENERATION
2011-10-25
PIER
Vol. 121, 215-224, 2011
download: 143
Experimental Demonstration of Double-Negative Metamaterials Partially Filled in a Circular Waveguide
Zhaoyun Duan Yanshuai Wang Xutong Mao Wen-Xiang Wang Min Chen
We have studied a new type of double-negative metamaterials (DNMs) composed of split ring resonators (SRRs) and wire strips with substrate teflon, suitable for generation of reversed Cherenkov radiation (RCR) which is TM radiation. We have experimentally observed a narrow pass band in a circular waveguide partially loaded with the DNMs and stop bands for SRRs-only with teflon and for wire strips-only with teflon, respectively. The experimental data show that the DNMs exhibit double-negative behavior over a frequency band of interest. This study provides a foundation for future experiment to observe RCR emitted by charged particles.
EXPERIMENTAL DEMONSTRATION OF DOUBLE-NEGATIVE METAMATERIALS PARTIALLY FILLED IN A CIRCULAR WAVEGUIDE
2011-10-24
PIER
Vol. 121, 181-213, 2011
download: 195
Investigation of the Characteristics of Barium Strontium Titanate (BST) Dielectric Resonator Ceramic Loaded on Array Antennas
Fwen Hoon Wee Mohd Fareq Bin Abd Malek Srimala Sreekantan Azlan Umar Al-Amani Farid Ghani You Kok Yeow
We investigated a dielectric resonator ceramic microstrip patch antenna. The antenna was formed using barium strontium titanate (BST), which has a dielectric constant of 15. A new approach, i.e., the use of a high temperature dielectric probe kit, was used to determine the dielectric constant of BST. A computer simulation technology (CST) microwave studio was used to simulate the BST array antennas, taking into consideration the dielectric constant. We also measured the gain of the antennas loaded with two-, four-, and six-element arrays of the BST antenna and found that the gain of a six-element BST array antenna was enhanced by a gain of about 1.6 dB over the four-element BST array antenna at 2.3 GHz. The impedance bandwidths of these BST array antennas for voltage standing wave ratio (VSWR) < 2 were in the application ranges, i.e., 2.30 to 2.50 GHz, established for Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN). Compared with the conventional array antenna with the same aperture size, the performance of the antenna obviously was improved, and the design is suitable for array applications, including base stations, for example.
INVESTIGATION OF THE CHARACTERISTICS OF BARIUM STRONTIUM TITANATE (BST) DIELECTRIC RESONATOR CERAMIC LOADED ON ARRAY ANTENNAS