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2013-03-12
PIER
Vol. 137, 759-773, 2013
download: 126
Application of Chiral Layers and Metamaterials for the Reduction of Radar Cross Section
Kimia Nikooei Tehrani Ali Abdolali Davoud Zarifi Farrokh Hojjat-Kashani
In this paper, the applications of chiral layers and metamaterials as radar absorbing materials are investigated. A perfect electric conductor plate covered by a chiral metamaterial is considered and after the formulation of the problem, reflection of the structure under an oblique plane wave incidence of arbitrary polarization is investigated. Then several examples of the applications of chiral layers in nondispersive, dispersive, and chiral nihility conditions are provided to design of zero reflection coatings. Finally, application of chiral metamaterial structures as microwave absorbers is discussed. In some of the provided examples, the method of genetic algorithm is used to optimize chiral coatings for the minimization of co- and cross reflected power.
APPLICATION OF CHIRAL LAYERS AND METAMATERIALS FOR THE REDUCTION OF RADAR CROSS SECTION
2013-03-12
PIER
Vol. 137, 741-758, 2013
download: 293
Efficient Neural Network Approach for 2D DOA Estimation Based on Antenna Array Measurements
Marija Agatonovic Zoran Stankovic Ivan Milovanovic Nebojsa Doncov Leen Sit Thomas Zwick Bratislav Milovanovic
In this paper, we present an efficient Artificial Neural Network (ANN)-based model to estimate both azimuth and elevation arrival angles of a signal source. To achieve this goal, the ANN model is constructed using measurement data obtained by a rectangular antenna array in the space-frequency domain. Unlike classical super-resolution algorithms such as 2D MUSIC, the proposed model is capable to account for imperfections of measurement equipment as well as mutual couplings between array elements. The neural model has been verified for several angular positions and frequencies. It is shown that use of ANN model to estimate angular positions of a signal source yields more accurate results when compared to 2D MUSIC. Moreover, the neural model significantly outperforms 2D MUSIC in terms of speed of computation.
EFFICIENT NEURAL NETWORK APPROACH FOR 2D DOA ESTIMATION BASED ON ANTENNA ARRAY MEASUREMENTS
2013-03-12
PIER
Vol. 137, 727-740, 2013
download: 113
Features Extraction of Rotationally Symmetric Ballistic Targets Based on Micro-Doppler
Xiaoyi Pan Wei Wang Jin Liu De-Jun Feng Yongcai Liu Guoyu Wang
It is potentially useful to perform target identification using micro-Doppler features because they contain information on the geometrical structure of the target. In this paper, the m-D effect of the rotationally symmetric ballistic target (BT) is analyzed which reveals that the m-D is not a form of sinusoidal modulation due to the sliding-type scattering. Inspired by the extended Hough transform (EHT), a method to extract all the six parameters of the BT is proposed. The m-D effect and the performance of feature extraction algorithm are demonstrated by the measured data in a microwave anechoic chamber.
FEATURES EXTRACTION OF ROTATIONALLY SYMMETRIC BALLISTIC TARGETS BASED ON MICRO-DOPPLER
2013-03-12
PIER
Vol. 137, 703-725, 2013
download: 130
Multifrequency Monopole Antennas by Loading Metamaterial Transmission Lines with Dual-Shunt Branch Circuit
He-Xiu Xu Guang-Ming Wang Yuan-Yuan Lv Mei-Qing Qi Xi Gao Shuo Ge
The theory and design of a new family of multifrequency monopole antennas by smartly loading a set of complementary metamaterial transmission line (CMTL) unit cells are investigated. The distributed CMTL elements, epsilon negative (ENG) or double negative (DNG) through incorporating additional capacitive gaps, contain a Koch-shaped extended complementary single split ring resonator pair (K-ECSSRRP) etched on the signal strip. The K-ECSSRRP features dual-shunt branches in the equivalent circuit model, rendering a distinguished resonator with dual zeroth-order resonant (ZOR) modes. By smartly controlling the element layout and loading different numbers of unit cells, ten antennas covering different communication standards (GSM1800, UMTS, Bluetooth, DMB and WIMAX) are designed and four of them are fabricated and measured. At most of operating frequencies, the antennas exhibit impedance matching better than -10 dB and normal monopolar radiation patterns. Numerical and experimental results both confirm that the single-cell or dual-cell ENG and DNG CMTL-loaded monopoles exhibit almost identical dual ZOR modes. Moreover, the loaded elements also contribute to the radiation, which is the major advantage of this prescription over previous lumped-element loadings. These antennas are compact and the multiple operating bands can be arbitrarily engineered, enabling an alternative and easy avenue toward monopoles with multifunction and high integration.
MULTIFREQUENCY MONOPOLE ANTENNAS BY LOADING METAMATERIAL TRANSMISSION LINES WITH DUAL-SHUNT BRANCH CIRCUIT
2013-03-12
PIER
Vol. 137, 687-702, 2013
download: 160
Development of Pyramidal Microwave Absorber Using Sugar Cane Bagasse (Scb)
Liyana Zahid Mohd Fareq Bin Abd Malek Hassan Nornikman Nur Adyani Mohd Affendi Azuwa Ali Nuriziani Hussin Badrul Hisham Ahmad Mohamad Zoinol Abidin Abdul Aziz
The need to find ways to effectively utilize the large quantities of agricultural waste that are produced is indicative of the huge potential associated with producing an alternative pyramidal microwave absorber for anechoic chamber-testing applications. We propose the development of a pyramidal microwave absorber that can use sugar cane bagasse (SCB), a byproduct from the production and processing of sugar cane, as the absorbent. In this paper, we report the results of our use of dielectric probe measurement to determine the dielectric constant and loss tangent of SCB. These values were used to model and simulate an SCB pyramidal microwave absorber in Computer Simulation Technology's (CST's) Microwave Studio. This absorber was operated in the microwave frequency range between 0.1 GHz and 20.0 GHz.
DEVELOPMENT OF PYRAMIDAL MICROWAVE ABSORBER USING SUGAR CANE BAGASSE (SCB)
2013-03-08
PIER
Vol. 137, 669-685, 2013
download: 125
Modeling SAR Images Based on a Generalized Gamma Distribution for Texture Component
Gui Gao Xianxiang Qin Shilin Zhou
In the applications of synthetic aperture radar (SAR) data, a crucial problem is to develop precise models for the statistics of the pixel amplitudes or intensities. In this paper, a new statistical model, called simply here GΓΓ, is proposed based on the product model by assuming the radar cross section (RCS) components (texture components) of the return obey a recently empirical generalized Gamma distribution. Meanwhile, we demonstrate theoretically that the proposed GΓΓ model has the well-known K and g0 distributions as special cases. We also derived analytically the estimators of the presented GΓΓ model by applying the "method-of-log-cumulants" (MoLC). Finally, the performance of the proposed model is tested by using some measured SAR images.
MODELING SAR IMAGES BASED ON A GENERALIZED GAMMA DISTRIBUTION FOR TEXTURE COMPONENT
2013-03-08
PIER
Vol. 137, 653-667, 2013
download: 132
A Broadband Out-of-Phase Power Divider for High Power Applications Using through Ground via (Tgv)
Yun Long Lu Gao-Le Dai Xingchang Wei Erping Li
In this paper, we present a broadband out-of-phase power divider with high power-handling capability. The proposed device consists of several sections of double-sided parallel-strip lines (DSPSLs), a mid-inserted conductor plane, and two external isolation resistors, which are directly grounded for heat sinking. A through ground via (TGV), connecting the top and bottom sides of DSPSLs, is employed. The special metal via is realized to short the isolation resistors at full-frequency band when the odd-mode is excited. Meanwhile, it can be ignored as the excitation is even-mode. This property is efficiently utilized to improve the bandwidth. To examine the proposed power divider in detail, a set of closed-form equations are derived. Meanwhile, the power operation analysis illustrates that the proposed power divider is a good candidate for high power applications. The design charts show that the proposed device can support a wide frequency ratio range (1-1.7). Furthermore, broadband responses can be obtained when proper frequency ratios are adopted. For verification, an experimental power divider operating at 1.25/1.75 GHz is implemented. The measured results exhibit a bandwidth of 44.3% with better than 15 dB return loss and 18 dB port isolation is achieved.
A BROADBAND OUT-OF-PHASE POWER DIVIDER FOR HIGH POWER APPLICATIONS USING THROUGH GROUND VIA (TGV)
2013-03-07
PIER
Vol. 137, 643-652, 2013
download: 114
A Synchronous Wideband Frequency-Domain Method for Long-Distance Channel Measurement
Chu-Feng Hu Zhou Zhou Shu Xia Guo
This paper proposes a novel synchronous wideband frequency domain method for measuring time domain response of long-distance channel. Its core consists of: (1) baseband signal generators at the transmission terminal and the reception terminal respectively are used to generate the wideband signal of the same frequency; (2) the two GPS clock frequency reference sources locked on the same satellite are used to yield the high-stability 10MHz signal as the external reference source of the baseband signal generator so that the initial phases of the wideband signals are basically the same; (3) the pulse per second (PPS) signal generated by the GPS clock frequency reference source is used as trigger signal to ensure that the baseband signal generator and the vector network analyzer (VNA) can transmit and receive signals synchronously; (4) the time domain response of the channel is indirectly obtained through the inverse Fourier transform of amplitude and phase of the frequency domain response. To verify the measurement method, experiments were performed, in which the sea surface evaporation waveguide which is tens of kilometers apart from each other was selected as the channel. The experimental results, given in Figs. 4 and 5, and their analysis show that the measurement method can obtain amplitude and phase of the signal whose band is hundreds of MHz and whose equivalent pulse width reaches 5ns. The measurement method is used to obtain the time domain response of the long-distance channel, verifying that the measurement method is effective.
A SYNCHRONOUS WIDEBAND FREQUENCY-DOMAIN METHOD FOR LONG-DISTANCE CHANNEL MEASUREMENT
2013-03-07
PIER
Vol. 137, 621-642, 2013
download: 162
A Novel Three-Step Image Formation Scheme for Unified Focusing on Spaceborne SAR Data
Wei Yang Jie Chen Hongceng Zeng Jian Zhou Pengbo Wang Chun-Sheng Li
Current advanced spaceborne synthetic aperture radar (SAR) systems may operate at multiple imaging modes, including conventional modes as stripmap, ScanSAR and spotlight, as well as the state-of-the-art SAR modes, e.g., sliding spotlight, TOPS (Terrain Observation by Progressive Scans) and inverse TOPS, etc. A novel image formation scheme for unified processing spaceborne SAR data was proposed, which significantly simplified complexity of SAR processor sub-system. The unified-model-coefficient (UMC) was defined for modeling all SAR modes by means of analyzing both imaging geometry and time-frequency diagram corresponding to each imaging mode, respectively. The unified mathematical formula for modeling all SAR modes echo signal was derived as a function of UMC. Consequently, a unified image formation scheme for accurately focusing spaceborne SAR data in an arbitrary mode was proposed, which integrates all of SAR image formation procedures into a standard three-step processing framework, namely, de-rotation, data focusing and re-sampling, which evidently improve efficiency and robustness of data processing sub-system. Computer simulation experiment results verify the effectiveness of the proposed scheme.
A NOVEL THREE-STEP IMAGE FORMATION SCHEME FOR UNIFIED FOCUSING ON SPACEBORNE SAR DATA
2013-03-07
PIER
Vol. 137, 599-619, 2013
download: 182
Broadband Modified Rectangular Microstrip Patch Antenna Using Stepped Cut at Four Corners Method
Alireza Moradi Tharek Bin Abdul Rahman
In this paper, a new method that called the ``Stepped Cut at Four Corners'' is introduced to design a multi-mode/broadband modified rectangular microstrip patch antennas (MRMPAs). In order to become acquainted with the new method, the design process of a monopole broadband MRMPA suitable for multifunctional wireless communication bands is explained. The methodology of the proposed broadband MRMPA design is presented in six stages. The first stage is designing a single-mode RMPA. Subsequently, by creating a step at the corners using the proposed method a dual-mode antenna is obtained at the second stage, while the triple-mode and multi-mode antennas are designed, at the third and fourth stages respectively. Two types of broadband antennas are obtained, the stepped line and straight line antennas. By increasing the number of steps, the antenna's operating bandwidth (BW), with return loss less than −10 dB, covers the frequency range from 900 MHz to 2.6 GHZ, which is suitable for GSM (900 MHz and 1.5 GHz), WiFi (2.4 GHz) and LTE (2.6 GHz) applications. In addition, the antenna prototype has been fabricated and measured in the all stages, in order to validate the simulation results, and there is a close agreement between the simulated and measured results.
BROADBAND MODIFIED RECTANGULAR MICROSTRIP PATCH ANTENNA USING STEPPED CUT AT FOUR CORNERS METHOD
2013-03-06
PIER
Vol. 137, 585-597, 2013
download: 136
Novel in-Line Microstrip Coupled-Line Bandstop Filter with Sharp Skirt Selectivity
Gui Liu Yongle Wu
This paper presents a novel design approach to design in-line microstrip bandstop filter with accurate design theory and sharp skirt selectivity. This kind of bandstop filter is based on a simple coupled-line structure, indicating compact and flexible circuit layout for microstrip implementation. For a single-section bandstop filter, the scattering parameters and their constrain conditions are achieved, which provides an effective design guide for multi-section bandstop filters. Theoretical analysis indicates that the even-mode and odd-mode characteristic impedances can be easily used to determine the desired bandstop performance while the total circuit layout keeps very compact. For demonstration, seven numerical examples are designed, calculated, and compared. Finally, both experimental and simulation results of a two-section two-cell microstrip bandstop filter operating at 1 GHz are presented to verify the theoretical predications.
NOVEL IN-LINE MICROSTRIP COUPLED-LINE BANDSTOP FILTER WITH SHARP SKIRT SELECTIVITY
2013-03-06
PIER
Vol. 137, 565-583, 2013
download: 127
FEM-Based Method for the Simulation of Dielectric Waveguide Grating Biosensors
Thomas Guillod Florian Kehl Christian V. Hafner
Label-free optical biosensors are important tools to study the kinetics, interaction and presence of (bio)chemical compounds in various fields such as biotechnology, pharma, diagnostics as well as environmental and food quality monitoring. Systems based on planar optical waveguides with input/output grating couplers are of interest as they offer multiple tuning parameters for the chip design and their high sensitivity. In the present paper, an algorithm based on the Finite-Elements Method (FEM) is proposed for finding the chip response and optimizing the sensitivity of the sensor system. Total field and scattered field coupled with the Transmission Line Transfer Matrix Method (TLTMM) are compared for the FEM. Unlike some widely used approximations, the impact of the grating depth, shape, duty cycle as well as losses and surface roughness are taken into account. Another advantage of the presented method is the possibility to implement a large part of the algorithm with commercially available FEM solver. Several practical situations are treated proving the validity of the approach against the Local Interference Method (LIME). The waveguide losses appear to be a decisive parameter for the chip design.
FEM-BASED METHOD FOR THE SIMULATION OF DIELECTRIC WAVEGUIDE GRATING BIOSENSORS
2013-03-04
PIER
Vol. 137, 551-564, 2013
download: 138
Electric Time Domain Reflectometry Sensors for Non-Invasive Structural Health Monitoring of Glass Fiber Composites
Gaurav Pandey Erik T. Thostenson Dirk Heider
Time domain reflectometry (TDR) offers the advantage of distributed sensing using a single transmission line sensor. In the present study, a parallel plate type non-invasive TDR sensor for structural health monitoring (SHM) of composite has been designed, modeled and experimentally tested. Five layer unidirectional glass fiber/epoxy composite specimens are fabricated. Specimens included a damage initiator in form of a cut in the central ply. The TDR sensor detects sub-surface damage in the composite non-invasively as the effective dielectric constant of the composite decreases due to the presence of delamination cracks. Previous work done on dielectrostriction is used to model the TDR response to strain changes. Qualitative agreement between theory and experimental results for strain sensing are found.
ELECTRIC TIME DOMAIN REFLECTOMETRY SENSORS FOR NON-INVASIVE STRUCTURAL HEALTH MONITORING OF GLASS FIBER COMPOSITES
2013-03-04
PIER
Vol. 137, 539-549, 2013
download: 118
A Novel Quad-Band (Gsm850 to IEEE 802.11a) PIFA for Mobile Handset
Pengcheng Li Jin Pan Deqiang Yang Zai-Ping Nie Jun Xing
In this paper, a novel planar inverted-F antenna (PIFA) with slotted ground structure is proposed for multiband mobile communication application. The multimode performance is applied for multiband operation in our design. The proposed antenna has good impedance matching characteristics for GSM850/900, DCS1800/1900, LTE2300/2500, IEEE 802.11a/b. The measured radiation efficiency of proposed antenna is all higher than 69% in GSM (824-960 MHz)/DCS (1710-1880 MHz)/PCS (1850-1990 MHz)/LTE (2300-2400 MHz, 2500-2690 MHz)/802.11b (2.4-2.48 GHz), and is up to 50% in IEEE 802.11a (5.15-5.825 GHz).
A NOVEL QUAD-BAND (GSM850 TO IEEE 802.11A) PIFA FOR MOBILE HANDSET
2013-03-04
PIER
Vol. 137, 527-538, 2013
download: 138
Arbitrary Loss Factors in the Wave Propagation Between RHM and LHM Media with Constant Impedance Throughout the Structure
Mariana Dalarsson Martin Karl Norgren Tatjana Asenov Nebojsa Doncov
We investigate the wave propagation properties in lossy structures with graded permittivity and permeability involving left-handed metamaterials. An exact analytic solution to Helmholtz' equation for a lossy case with both real and imaginary parts of permittivity and permeability profile, changing according to a hyperbolic tangent function along the direction of propagation, is obtained. It allows for different loss factors in RHM and LHM media. Thereafter, the corresponding numerical solution for the field intensity along the composite structure is obtained by means of a dispersive numerical model of lossy metamaterials that uses a transmission line matrix method based on Z-transforms. We present the expressions and graphical results for the field intensity along the composite structure and compare the analytic and numerical solutions, showing that there is an excellent agreement between them.
ARBITRARY LOSS FACTORS IN THE WAVE PROPAGATION BETWEEN RHM AND LHM MEDIA WITH CONSTANT IMPEDANCE THROUGHOUT THE STRUCTURE
2013-03-04
PIER
Vol. 137, 513-526, 2013
download: 101
Super/Zero Scattering Characteristics of Circular SRR Arrays
Yuan Zhang Erik Forsberg Sailing He
The ability to control the scattering property of an object is important in many applications. In this paper, we propose and study the scattering characteristics of a circular array of split-ring resonators (SRRs). By calculating the scattered energy spectrum, we show that the proposed structure has a localized surface plasmon resonance like behavior, which makes it useful as a super scatterer. Furthermore, in a special case, the proposed structure exhibits transparency to the illuminated waves, i.e. it does not scatter any energy at all and thus acts as a zero electromagnetic scattering object.
SUPER/ZERO SCATTERING CHARACTERISTICS OF CIRCULAR SRR ARRAYS
2013-03-04
PIER
Vol. 137, 487-512, 2013
download: 114
Elimination of Numerical Dispersion from Electromagnetic Time Domain Analysis by Using Resource Efficient Finite Element Technique
S M Raiyan Kabir B. M. Azizur Rahman Arti Agrawal Ken Thomas Victor Grattan
Time domain analysis of electromagnetic wave propagation is required for design and characterization of many optical and microwave devices. The FDTD method is one of the most widely used time domain methods for analysing electromagnetic scattering and radiation problems. However, due to the use of the Finite Difference grid, this method suffers from higher numerical dispersion and inaccurate discretisation due to staircasing at slanted and curve edges. The Finite Element (FE)-based meshing technique can discretize the computational domain offering a better approximation even when using a small number of elements. Some of the FE-based approaches have considered either an implicit solution, higher order elements, the solution of a large matrix or matrix lumping, all of which require more time and memory to solve the same problem or reduce the accuracy. This paper presents a new FE-based method which uses a perforated mesh system to solve Maxwell's equations with linear elements. The perforated mesh reduces the requirement on memory and computational time to less than half of that compared to other FE-based methods. This paper also shows a very large improvement in the numerical dispersion over the FDTD method when the proposed method is used with an equilateral triangular mesh.
ELIMINATION OF NUMERICAL DISPERSION FROM ELECTROMAGNETIC TIME DOMAIN ANALYSIS BY USING RESOURCE EFFICIENT FINITE ELEMENT TECHNIQUE
2013-02-28
PIER
Vol. 137, 475-485, 2013
download: 131
Magnetic Response and Negative Refraction at Optical Frequencies on the Basis of Electronic Transitions in Rare-Earth Ions Doped Crystals
Xiaojian Fu Yuanda Xu Ji Zhou
Magnetic response based on a two-level magnetic dipole transition in rare earth ions doped crystals was studied. Semi-classic theory and Wigner-Eckart theorem were used to calculate the magnetic permeability. It is found that negative permeability can be attained near the transition frequencies. In order to realize simultaneously negative permittivity and negative permeability, an electric dipole transition at the same frequency was also adopted, and a negative refraction region with a bandwidth of 0.57 MHz is demonstrated in (Yb0.02 Sm0.02Y0.96)3Al5O12 crystal. This explores a new route to obtain magnetic response and negative refraction at optical frequencies with nature-existed materials instead of metamaterials.
MAGNETIC RESPONSE AND NEGATIVE REFRACTION AT OPTICAL FREQUENCIES ON THE BASIS OF ELECTRONIC TRANSITIONS IN RARE-EARTH IONS DOPED CRYSTALS
2013-02-28
PIER
Vol. 137, 453-473, 2013
download: 228
The Influence of Human Head Model Wearing Metal-Frame Spectacles to the Changes of SAR and Antenna Gain: Simulation of Frontal Face Exposure
Mohd Hafizuddin Mat Mohd Fareq Bin Abd Malek William G. Whittow Suzanna Harun Ronald Muhammad Solihin Zulkefli Norshafinash Saudin Latifah Mohamed
The relationship between specific absorption rate (SAR) and antenna gain inside the head due to the metal-frame spectacles was investigated. The radio frequency (RF) energy source considered is the smartphone used in the frontal face. A computer simulation using CST Microwave Studio 2012 was used for the investigation. Two sets of dipole antennas, operated at 900 MHz and 1800 MHz for GSM applications, were used as representative radiation sources from a mobile phone. Parametric studies were conducted to determine the optimum length of the metal rod, and the length was used to study the possibility of RF irradiation of the metal spectacles model. Then, the spectacles model was used as an analysis tool to study the interaction between gain and SAR in the head. The radiation pattern was plotted to identify the causes of the interactions. The gain decreased when the energy source was very close to the spectacles, and SAR increased enormously.
THE INFLUENCE OF HUMAN HEAD MODEL WEARING METAL-FRAME SPECTACLES TO THE CHANGES OF SAR AND ANTENNA GAIN: SIMULATION OF FRONTAL FACE EXPOSURE
2013-02-28
PIER
Vol. 137, 439-452, 2013
download: 95
Use of Aligned Carbon Nanotubes as Electric Field Sensors
Chieh-Lien Lu Hsin-Jung Tsai Bee-Yu Wei Wen-Kuang Hsu
Application of electric field in normal to aligned carbon nanotubes creates Coulomb forces at intertube junctions and tubes become closely packed. Packed structure facilitates intertube transfer of carriers and reduced resistance is found to scale with field strength. Aggregated nanotubes are therefore used as field sensors and sensitivity is evident by drastic fluctuations of resistance. Sensing mechanism is discussed and verified.
USE OF ALIGNED CARBON NANOTUBES AS ELECTRIC FIELD SENSORS