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2012-01-11
PIER
Vol. 123, 527-541, 2012
download: 233
A Dual-Band Dual-Polarized Microstrip Array Antenna for Base Stations
Khatereh Moradi Saeid Nikmehr
This paper presents a new dual-band, dual-polarized 1 x 4 antenna array design for telecommunication base station. One of the bands covers global system for mobile communication (GSM) band, while the other covers both digital communication system (DCS) and universal mobile telecommunication system (UMTS) bands. The antenna is based upon an aperture stacked patch layout and incorporates a simple and novel dual-layered feeding technique to achieve dual polarized radiation. For feeding the array elements, a corporate feed network is used. In order to achieve appropriate matching in both bands, a three-section Chebyshev transformer has been designed. The proposed antenna shows good port decoupling, less than -30 dB for dual linear polarization over its operating bands. Peak antenna gains about 11 dBi and 11.6 dBi have been obtained for lower and upper bands, respectively. The effort was directed toward the design of a single standalone dual-polarized antenna to cover all three bands.
A DUAL-BAND DUAL-POLARIZED MICROSTRIP ARRAY ANTENNA FOR BASE STATIONS
2012-01-06
PIER
Vol. 123, 509-526, 2012
download: 104
Planar Grating Multiplexers Using Silicon Nanowire Technology: Numerical Simulations and Fabrications
Jun Song Yuanzhou Li Xiang Zhou Xuan Li
Planar waveguide gratings have shown great potential for the application of the wavelength division multiplexing (WDM) functionality in optical communications due to their compactness and high spectral finesse. Planar gratings based on silicon nanowire technology have high light confinements and consequently very high integration density, which is 1--2 orders of magnitude smaller than conventional silica based devices. In the present paper, we will simulate the silicon nanowire based planar grating multiplexer with total-internal-reflection facets using a boundary integral method. The polarization dependent characteristics of the device are analyzed. In addition, the planar grating multiplexer with 1 nm spacing is fabricated and characterized. Compared with measured values, the numerical results show that the sidewall roughness in the grating facets can result in a large insertion loss for the device.
PLANAR GRATING MULTIPLEXERS USING SILICON NANOWIRE TECHNOLOGY: NUMERICAL SIMULATIONS AND FABRICATIONS
2012-01-06
PIER
Vol. 123, 485-508, 2012
download: 171
A Novel Imaging Approach for High Resolution Squinted Spotlight SAR Based on the Deramping-Based Technique and Azimuth Nlcs Principle
Dao Xiang An Z.-M. Zhou Xiao-Tao Huang Tian Jin
The imaging problem of spotlight synthetic aperture radar (SAR) in the presence of azimuth spectrum folding phenomenon can be resolved by adopting the azimuth deramping-based technique and traditional stripmap SAR imaging algorithm, and this method is the so-called two-step processing approach. However, when the spotlight SAR operates on squinted mode, the echo two-dimensional (2D) spectrum is shifted and skewed due to the squint angle. In such case, the original two-step processing approach is not suitable anymore. This paper presents a novel imaging algorithm using the deramping-based technique and azimuth nonlinear chirp scaling (ANLCS) technique. First, the problem of azimuth spectrum folding phenomenon in squinted spotlight SAR is analyzed. Subsequently, based on the analysis results, the linear range walk correction (LRWC) is applied for removing the squint angle impacts on signal azimuth coarse focusing. At last, a modified azimuth NLCS algorithm is proposed for overcoming the depth of focus (DOF) limitation problem that induced by the LRWC preprocessing. Point targets simulation results are presented to validate the effectiveness of the proposed algorithm to process squinted spotlight SAR data with azimuth spectrum folding phenomenon.
A NOVEL IMAGING APPROACH FOR HIGH RESOLUTION SQUINTED SPOTLIGHT SAR BASED ON THE DERAMPING-BASED TECHNIQUE AND AZIMUTH NLCS PRINCIPLE
2012-01-06
PIER
Vol. 123, 467-484, 2012
download: 105
A Novel Estimation Approach of Dynamic and Coupling Baseline for Distributed Satellite SAR
Liang Feng Huaping Xu Chun-Sheng Li Shuang Li Han Gao
In distributed satellite synthetic aperture radar (DS-SAR), along-track and cross-track baselines couple with each other and change dynamically due to formation flying, which makes it difficult to estimate interferometric baseline accurately. To solve the problem, a novel high-precision baseline estimation approach based on interferometric phase is proposed. By modeling accurate relationship between coupling baselines and two-dimensional (azimuth and range) inteferometric fringe frequency under the ellipsoid earth model, the along-track and cross-track baseline can be estimated separately by interferometric phase decoupling. By selecting several segments from interferometric phase during the whole data-take time and estimating instantaneous baseline of each segment, the dynamic baseline can be obtained via a linear filtering. Besides, to improve the baseline estimation accuracy, Semi-Newton iterative method is applied to acquire high-precision fringe frequency estimation, which can make the baseline estimation achieve centimeter level precision. The simulation validates the approach.
A NOVEL ESTIMATION APPROACH OF DYNAMIC AND COUPLING BASELINE FOR DISTRIBUTED SATELLITE SAR
2012-01-06
PIER
Vol. 123, 447-465, 2012
download: 242
Fourier Based Combined Techniques to Design Novel Sub-Wavelength Optical Integrated Devices
Luis Zavargo-Peche Alejandro Ortega-Monux Juan Gonzalo Wanguemert-Perez Inigo Molina-Fernandez
We present a tool to aid the design of periodical structures, such as subwavelength grating (SWG) structures. It is based on the Fourier Eigenmode Expansion Method and includes the Floquet modes theory. Besides, the most interesting implemented functionalities to ease the design of photonic devices are detailed. The tool capabilities are shown using it to analyse and design {three} different SWG devices.
FOURIER BASED COMBINED TECHNIQUES TO DESIGN NOVEL SUB-WAVELENGTH OPTICAL INTEGRATED DEVICES
2012-01-05
PIER
Vol. 123, 427-445, 2012
download: 96
A Comprehensive Facet Model for Bistatic SAR Imagery of Dynamic Ocean Scene
Yan Wei Zhao Min Zhang Xupu Geng Ping Zhou
A comprehensive facet model for bistatic synthetic aperture radar (Bis-SAR) imagery of dynamic ocean scene is presented in this paper. An efficient facet scattering model is developed to calculate the radar cross section (RCS) of the ocean surface for Bis-SAR firstly. Further more, this facet model is combined with a bistatic velocity bunching ($VB$) modulation of long ocean waves to obtain the Bis-SAR intensity expression in image plane of ocean scene. The displacement of the scatter elements in the image plane and the degradation of radar resolution in azimuth direction are quantificationally analyzed. Finally, Bis-SAR imagery simulations of ocean surface are illustrated, proving the validity and practicability of the presented algorithms.
A COMPREHENSIVE FACET MODEL FOR BISTATIC SAR IMAGERY OF DYNAMIC OCEAN SCENE
2012-01-04
PIER
Vol. 123, 407-426, 2012
download: 236
New Wilkinson Power Dividers Based on Compact Stepped-Impedance Transmission Lines and Shunt Open Stubs
Pu-Hua Deng Jin-Hao Guo Wen-Chi Kuo
This study presents new Wilkinson power dividers using compact stepped-impedance structures and capacitive loads to achieve the required power splitting. This approach can produce additional transmission zeros and effectively suppress the desired stopbands because shunt open stubs realize capacitive loads. This study proposes two equal-split dividers and two unequal-split dividers. For the first equal-split case, one shunt open stub forms the needed capacitor in each transmission path, creating one additional transmission zero in each path. To obtain one more transmission zero in each transmission path, the second Wilkinson power divider uses two shunt open stubs in each path to achieve the same capacitor value as the first divider. This study also tests unequal-split dividers with one and two transmission zeros in each path to confirm that compact stepped-impedance transmission lines and shunt to-ground capacitors can be utilized in unequal power division.
NEW WILKINSON POWER DIVIDERS BASED ON COMPACT STEPPED-IMPEDANCE TRANSMISSION LINES AND SHUNT OPEN STUBS
2012-01-03
PIER
Vol. 123, 385-405, 2012
download: 134
Facet-Based Treatment on Microwave Bistatic Scattering of Three-Dimensional Sea Surface with Electrically Large Ship
Hui Chen Min Zhang Hong-Cheng Yin
A feasible simulator, of which formulation and mechanism should be simple and time saving, is developed in this paper to overcome the difficulties of prediction on the EM scattering from three-dimensional (3-D) electrically very large ship-sea models. The work in this paper is twofold. First, the sea surfaces are supposed to be a combination of many locally-tilted slightly rough facets with two-scale profiles. The radar return from each local facet is associated to a semi-deterministic scheme which is established by combining the geometric optics limit of Kirchhoff Approximation (KA-GO) with the Bragg components of Bass-Fuks' two-scale model (BFTSM). Furthermore, we associate the complex reflective function of the respective facet by a so-called Phase-modified Facet Model (PMFM), in which the facet's phase is treated approximately as a combination of inherent part that follows a homogeneous random distribution and coherent part associated with the relative path-delay. Second, in companion with the semi-deterministic treatment of the sea scattering model, a hybrid approximate algorithm is proposed to deal with the composite scattering of electrically large ship-sea model, which is entirely evolved through facets (for the sea surface) and wedges (for the ship target). The method of equivalent currents (MEC) and a hybrid frame which combines the four path model (FPM) with the quasi-image method (QIM) are employed to calculate the scattering characteristics of the ship-like target and ship-sea interactions, respectively. The entire simulator is of comparatively significant computational efficiency, and suitable for providing a preliminary prediction on the instantaneous complex reflective functions and normalized radar cross sections (NRCS) mean levels for electrically very large ship-sea model.
FACET-BASED TREATMENT ON MICROWAVE BISTATIC SCATTERING OF THREE-DIMENSIONAL SEA SURFACE WITH ELECTRICALLY LARGE SHIP
2011-12-31
PIER
Vol. 123, 371-384, 2012
download: 130
New Dual-Band Bandpass Filter with Wide Upper Rejection Band
Jen-Tsai Kuo Shih-Wei Lai
new circuit structure is proposed for design of dual-band bandpass filters with a wide upper stopband. The unit cell of the circuit consists of two two-port networks in shunt connection; one is a coupled-line section of λ/4 long followed by a transmission line segment of identical length, and the other has the same elements but cascaded in reverse order, where λ/4 is the wavelength at arithmetic mean frequency of the two passbands. Higher-order circuits can be obtained by directly cascading two or more such cells and show improved frequency selectivity. In addition to on both sides of the passbands, transmission zeros are also created in the rejection bands. Analysis of the unit cell circuit is formulated by the transmission line theory, and design curves for one- and two-cell circuits are provided. In realization, interdigital capacitors are incorporated with the λ/4 coupled sections for compensating the effect of unequal modal phase velocities on the filter performance in the rejection band. Two circuits are fabricated and measured to validate the analysis.
NEW DUAL-BAND BANDPASS FILTER WITH WIDE UPPER REJECTION BAND
2011-12-31
PIER
Vol. 123, 355-370, 2012
download: 112
Reduced Peec Modeling of Wire-Ground Structures Using a Selective Mesh Approach
Zhenfei Song Fei Dai Donglin Su Shuguo Xie Fabrice Duval
The wire-ground electromagnetic coupling structures are quite common in avionics system electromagnetic compatibility (EMC) analysis. The increasing complexities of physical structures make electromagnetic modeling an increasingly tough task, and computational efficiency is desirable. In this paper, a novel selective mesh approach is presented for partial element equivalent circuit (PEEC) modeling where intense coupling parts are meshed while the remaining parts are eliminated. With the proposed approach, the meshed ground plane is dependent on the length and height of the above wires. Relevant compact formulae for determining mesh boundaries are deduced, and a procedure of general mesh generation is also given. A numerical example is presented, and a validation check is accomplished, showing that the approach leads to a significant reduction in unknowns and thus computation time and consumed memories, while preserving the sufficient precision. This approach is especially useful for modeling the electromagnetic coupling of wires and reference ground, and it may also be beneficial for other equivalent circuit modeling techniques.
REDUCED PEEC MODELING OF WIRE-GROUND STRUCTURES USING A SELECTIVE MESH APPROACH
2011-12-29
PIER
Vol. 123, 337-354, 2012
download: 145
Improved Performance of Circularly Polarized Antenna Using Semi-Planar Chiral Metamaterial Covers
Davoud Zarifi Homayoon Oraizi Mohammad Soleimani
The influence of semi-planar chiral metamaterial (CMM) structures on the important characteristics of circularly polarized (CP) antennas is investigated in this paper. Based on this idea, CP planar two-arm Archimedean spiral (ARSPL) antenna and helical antenna are designed and the effects of chiral covers on their gain (or directivity), axial-ratio (AR), and return loss are considered. The results demonstrate that this method is greatly effective and the addition of a semi-planar CMM cover at an optimized distance over the CP antenna, significantly improves its gain and axial ratio.
IMPROVED PERFORMANCE OF CIRCULARLY POLARIZED ANTENNA USING SEMI-PLANAR CHIRAL METAMATERIAL COVERS
2011-12-29
PIER
Vol. 123, 321-336, 2012
download: 272
Characteristic of Plasma Sheath Channel and Its Effect on Communication
Lei Shi Baolong Guo Yanming Liu Jiangting Li
The plasma sheath communication blackout issue for hypersonic or reentry vehicles is addressed from a channel characteristic perspective. Different from previous research, this paper emphasizes the importance of plasma sheath channel in the study of plasma communication blackout, and the discussion on transmission and phase shift characteristic of plasma sheath channel and their effect on communication performance was made with detail. A mathematical plasma sheath channel model is proposed and following the roadmap about how to obtain channel characteristic parameter is given. Flow field simulation of a blunt conical body physical was made, and the electron density and collision frequency profile got from flow field result under different incident angle at Mach 10-20 are presented thoroughly. The performance for QPSK based communication system under the established plasma channel is evaluated finally. It is indicated in our research that channel attenuation feature variation regularity is consistent with that of incident wave or Mach number, but the phase shift variation regularity with incident frequency or Mach number appears fall into chaos because of multiple 360 degree removal of original phase shift from communication view and complicated ratio relationships among incident wave, plasma frequency and collision frequency. Communication simulations result show that bit error rate agree with phase shift chaos well and phase shift exert large influence on present typical racking, telemetry, and command system. Some useful implications obtained from this study to improve communication performance include high frequency, high power and further rapid acquisition/tracing phase-locked loop compensating large phase shift.
CHARACTERISTIC OF PLASMA SHEATH CHANNEL AND ITS EFFECT ON COMMUNICATION
2011-12-29
PIER
Vol. 123, 299-320, 2012
download: 141
Gradual Thinning Synthesis for Linear Array Based on Iterative Fourier Techniques
Xin-Kuan Wang Yong-Chang Jiao Yan Yan Tan
In this paper, a modified iterative fourier technique (MIFT) for thinning uniformly spaced linear arrays featuring a minimum sidelobe level as well as narrow beam is presented. Since IFT is a thinning procedure which has to be performed many trial times with different initial element distributions to get the optimum solution, it is, to some extent, time consuming. Moreover, in each trial of IFT, the number of iterations is usually low, which makes the method tend to be trapped in local solution even with a large number of trials. Therefore, the similar procedures for both MIFT and IFT are to derive the element excitations from the prescribed array factor using successive forward and backward Fourier transforms, and array thinning is accomplished by setting the amplitudes of a predetermined number of the largest element excitations to unity while the others to zero during each iteration cycle. Furthermore, in MIFT, based on the idea of gradual thinning which is inspired by perturbation theory, an adaptively changed fill factor is proposed to modify IFT with the purpose of accelerating computational speed and facilitating convergence. The immediate result caused by this modified fill factor can be embodied in two points. One point is that unlike the random number of iterations contained in different trials of IFT, the number of iterations in all trials of MIFT is a fixed value and only predetermined by the array inherent features (symmetrical or asymmetrical) and fill factor. Therefore, sufficient iterations are ensured in each trial to effectively help the algorithm avoid trapping. The other point is that when MIFT is performed, the array elements are gradually truncated, which maintains the most useful element excitations while maximally excludes the bad excitations, so that the optimum solution could be obtained through only a small number of trials and thereby substantially save computational cost. The effectiveness of MIFT will be demonstrated for various linear arrays and compared with the published reports.
GRADUAL THINNING SYNTHESIS FOR LINEAR ARRAY BASED ON ITERATIVE FOURIER TECHNIQUES
2011-12-24
PIER
Vol. 123, 279-298, 2012
download: 135
On Linear Mapping of Filter Characteristic to Position of Tuning Elements in Filter Tuning Algorithm
Jerzy Julian Michalski
This work presents a novel approach in building a multidimensional approximator which is used as a linear operator for mapping the vector of detuned filter characteristic to the vector of deviations of tuning elements. This has been done for the purpose of using it in postproduction filter tuning algorithm. With the use of collected sets of deviations of tuning elements and filter characteristics corresponding to them, the least squares method (LSM) is applied to determine the matrix which realizes the linear mapping between these vectors. The matrix found in this method approximates the vectors of both spaces (filter characteristics and corresponding deviations of tuning elements). In tuning process this matrix is used to determine the vector of tuning element deviations for a given detuned filter characteristic read from Vector Network Analyzer. To increase the ``quality'' of linear operator filter characteristics are transformed with the use of Karhunen-Loeve transform (Principal Component Analysis). In contrast to non-linear artificial intelligence approximators used in filter tuning and published to-date, this method does not require a time-consuming training process. Filter tuning experiments have been performed and proved the correctness of the presented approach.
ON LINEAR MAPPING OF FILTER CHARACTERISTIC TO POSITION OF TUNING ELEMENTS IN FILTER TUNING ALGORITHM
2011-12-24
PIER
Vol. 123, 263-277, 2012
download: 119
Composite Scattering of Ship on Sea Surface with Breaking Waves
Min Zhang Wei Luo Gen Luo Chao Wang Hong-Cheng Yin
The composite backscattering of the ship model on sea surface is investigated with the spilling breaking waves and ship bow waves. The spilling breakers are approximately modeled with the wedge-like waves, and the ship bow waves are simulated based on the Kelvin model. With the modified four-path model, each scattering component is evaluated with the high frequency approximation methods for the total composite scattering. Due to the volume scattering, the composite scattering at large incidence angles is strongly enhanced by the non-Bragg scattering. The relationship of the composite scattering and the ship motion is analyzed. The numerical results of sea surface scattering agree with the measured data well, and the complex physical mechanism of the low-grazing-angle composite scattering is explicitly evaluated in this paper.
COMPOSITE SCATTERING OF SHIP ON SEA SURFACE WITH BREAKING WAVES
2011-12-22
PIER
Vol. 123, 243-261, 2012
download: 297
The Far Field Transformation for the Antenna Modeling Based on Spherical Electric Field Measurements
Ping Li Li Jun Jiang
According to the uniqueness theorem, the far field radiation pattern of radiators such as antennas can be determined from the measured tangential electric or magnetic field components over an arbitrary Huygens' surface enclosing the radiator. In this paper, a method using the spherical electric field measurement is developed to calculate the far field radiation. Following the Schelkunoff's field equivalence principle, a spherical region surrounding the radiator is assumed and its internal space is filled up with the perfect electric conductor (PEC). The radiated field from the Huygens' equivalent electric current is zero. Referring to the Ohm-Rayleigh method and the scattering wave superposition, the dyadic Green's function (DGF) with the presence of a PEC sphere is expanded by a series of spherical vector wave functions. Based on the DGF and the measured tangential electric field, the radiation behavior of the radiator can be directly predicted without involving the uncertainty from the inverse process. The robustness and accuracy of the proposed method are verified through several canonical antenna benchmarks.
THE FAR FIELD TRANSFORMATION FOR THE ANTENNA MODELING BASED ON SPHERICAL ELECTRIC FIELD MEASUREMENTS
2011-12-20
PIER
Vol. 123, 227-241, 2012
download: 132
Deformable, Time-Varying Boundary Problems in Electrodynamics
M. J. Mehler Constantinos Constantinou M. J. Neve
A novel perturbation technique is formulated that enables the efficient calculation of current on surfaces undergoing time-varying mechanical deformations. The technique computes the current on the perturbed surface using as its starting point the solution for a related static case. This is initially derived using a standard analytical or numerical technique. The key advantage of this approach is that only an initial (computationally expensive) electromagnetic characterisation of the static problem is required. The surface current perturbation terms (and hence the radiated fields) are then directly computed from the static problem with a very low computational overhead.
DEFORMABLE, TIME-VARYING BOUNDARY PROBLEMS IN ELECTRODYNAMICS
2011-12-20
PIER
Vol. 123, 205-225, 2012
download: 152
A Hybrid Nfm/MoM Full-Wave Analysis of Layered Prolate Head Model Exposed to Handset Antenna
Lei Zhao Ke-Li Wu
The electromagnetic radiation of a handset antenna to a human head model is rigorously analyzed by a new hybrid approach. In the analysis, human head is modeled by a double layered prolate spheroid with complex permittivity. A hybrid Null Field Method/Method of Moments (NFM/MoM) approach is proposed for the first time. The method is general and capable of dealing with multiple scatterers and radiators. By means of the hybrid approach, the NFM is used to model the scattering problem of the head model, and the MoM is applied to a handset antenna. The electromagnetic coupling between the head model and an antenna is taken into account by a fast convergent iteration process. Numerical results of electric field near and inside the head model and the input impedance of the antenna are calculated by the proposed hybrid approach and commercial full wave EM software. Very good agreement is obtained, which demonstrates the accuracy and efficiency of the proposed approach.
A HYBRID NFM/MOM FULL-WAVE ANALYSIS OF LAYERED PROLATE HEAD MODEL EXPOSED TO HANDSET ANTENNA
2011-12-20
PIER
Vol. 123, 189-204, 2012
download: 115
Experimental Comparison of Remedial Single-Channel Operations for Redundant Flux-Switching Permanent-Magnet Motor Drive
Wenxiang Zhao Ming Cheng Ruiwu Cao Jinghua Ji
Redundant flux-switching permanent-magnet (R-FSPM) motor is a new fault-tolerant machine having PMs in the stator, offering high efficiency, high reliability, and robust structure. This paper proposes two remedial control strategies for fault-tolerant operations of the R-FSPM motor drive in the single-channel (SC) mode. First, by doubling the healthy-channel currents, the reduced torque due to one channel loss can be remedied, the so-called remedial brushless AC (BLAC) operation mode. Second, by injecting harmonic current (IHC) considering harmonic back-EMF effect, the reduced torque can also be smoothly remedied, the so-called remedial IHC operation mode. Finally, both of the proposed remedial control strategies are verified by co-simulation and experimentation, hence confirming the validity of the proposed fault-tolerant R-FSPM motor drive.
EXPERIMENTAL COMPARISON OF REMEDIAL SINGLE-CHANNEL OPERATIONS FOR REDUNDANT FLUX-SWITCHING PERMANENT-MAGNET MOTOR DRIVE
2011-12-19
PIER
Vol. 123, 175-187, 2012
download: 119
A Class of Polarization-Invariant Directional Cloaks by Concatenation via Transformation Optics
Jingzhi Li Hongyu Liu
This article is devoted to the construction and investigation of a class of polarization-invariant directional cloaks by concatenation of cloaking medium components via transformation optics. It improves the construction of the first polarization-invariant directional cloak, introduced by Agarwal et al. [1]. The main ingredient is to construct a capsuloid transformed metamaterial consisting of an lp-cylindrical transformation map and two half lp--spherical transformation maps. Numerical investigation is carried out to test the performances of the cloaks under different polarized incoming waves. A salient feature of our cloaks is compact-sizedness, namely the geometrical size is no longer dependent on the regularization parameter ρ under the non-uniform map. In particular, we study the cloaking effect with respect to the regularization parameter ρ and the incident direction.
A CLASS OF POLARIZATION-INVARIANT DIRECTIONAL CLOAKS BY CONCATENATION VIA TRANSFORMATION OPTICS