PIER | PIER Journals

2011-07-14

PIER

Vol. 118, 505-525, 2011

download: 900

RCS Computation Using a Parallel in-Core and Out-of-Core Direct Solver

Daniel Garcia-Donoro, Ignacio Martinez-Fernandez, Luis E. Garcia-Castillo, Yu Zhang and Tapan Kumar Sarkar

Application to RCS computation of a higher order solver based on the surface integral approach is presented. The solver uses a direct method to solve the corresponding algebraic system of equations. Two versions of the solver are available: in-core and out-of-core. Both are efficiently implemented as parallel codes using Message Passing Interface libraries. Several benchmark structures are analyzed showing the reliability, performance, and versatility to run in a wide variety of computer platforms, of the solver. The results shown are illustrative of what is the maximum frequency of analysis of the structures for a given type of simulation platform.

RCS COMPUTATION USING A PARALLEL IN-CORE AND OUT-OF-CORE DIRECT SOLVER

2011-07-13

PIER

Vol. 118, 487-504, 2011

doi:10.2528/PIER11051711

download: 648

Study of Nonreciprocal Devices Using Three-Strip Ferrite Coupled Line

Wojciech Marynowski and Jerzy Mazur

This paper presents the investigations of nonreciprocal devices employing a novel ferrite coupled line junction. The structure is designed using coplanar line technology with the ground half-planes reduced to the strips. The investigated junction is composed of one ferrite section placed in between of two dielectric sections. In the ferrite section the longitudinally magnetized ferrite slab is located at the top or the bottom of the strips and is covered with the dielectric layers. In the dielectric sections the ports of the junctions are located. The wave parameters and field distributions of the modes propagated in the dielectric and ferrite sections are obtained from spectral domain approach. In order to determine the scattering matrix of the junction the mode matching method is utilized. The investigation of the circulator and isolator designed based on the S-matrix of the junction are presented. The obtained results are verified by comparing them with HFSS simulations and own measurements of the fabricated devices. In both cases a very good agreement is observed.

STUDY OF NONRECIPROCAL DEVICES USING THREE-STRIP FERRITE COUPLED LINE

2011-07-13

PIER

Vol. 118, 461-486, 2011

doi:10.2528/PIER11050408

download: 556

A Bimodal Reconstruction Method for Breast Cancer Imaging

Daniel Flores-Tapia, Martin O'Halloran and Stephen Pistorius

Breast Microwave Radar (BMR) has been proposed as an alternative modality for breast imaging. This technology forms a reflectivity map of the breast region by illuminating the scan area using ultra wide band microwave waveforms and recording the reflections from the breast structures. Nevertheless, BMR images require to be interpreted by an experienced practitioner since the location and density of the breast region can make the detection of malignant lesions a difficult task. In this paper, a novel bimodal breast imaging reconstruction method based on the use of BMR and Electrical Impedance Tomography (EIT) is proposed. This technique forms an estimate of the breast region impedance map using its corresponding BMR image. This estimate is used to initialize an EIT reconstruction method based on the monotonicity principle. The proposed method yielded promising results when applied to MRI-derived numeric breast phantoms.

A BIMODAL RECONSTRUCTION METHOD FOR BREAST CANCER IMAGING

2011-07-13

PIER

Vol. 118, 441-459, 2011

doi:10.2528/PIER11053012

download: 684

Attenuation in Extended Structures Coated with Thin Magneto-Dielectric Absorber Layer

Marina Koledintseva, Alexander G. Razmadze, Aleksandr Y. Gafarov, Victor V. Khilkevich, James Drewniak and Takanori Tsutaoka

Thin absorbing layers containing magnetic alloy or ferrite inclusions can be effectively used for attenuating common-mode currents on extended structures, such as power cords, cables, or edge-coupled microstrip lines. An analytical model to evaluate attenuation on the coaxial line with the central conductor coated with a magneto-dielectric layer is proposed and validated by the experiments and numerical modeling. The analytical model is validated using available magneto-dielectric samples of different thicknesses. This model can serve for comparing and predicting the absorptive properties of different samples of magneto-dielectric materials, whose compositions may be unknown, but dielectric and magnetic properties can be determined by independent measurements over the specified frequency ranges. From modeling the absorption in a coaxial line with a wrapped central conductor, it could be concluded whether it is reasonable to use this particular material in such applications as a shield on an Ethernet or other cable, for reducing potential common-mode currents and unwanted radiation in the frequency range of interest.

ATTENUATION IN EXTENDED STRUCTURES COATED WITH THIN MAGNETO-DIELECTRIC ABSORBER LAYER

2011-07-11

PIER

Vol. 118, 425-440, 2011

doi:10.2528/PIER11031110

download: 626

Comparison of Surface Integral Equations for Left-Handed Materials

Marta Gomez Araujo, Jose Taboada, Javier Rivero and Fernando Obelleiro

A wide analysis of left-handed material (LHM) spheres with different constitutive parameters has been carried out employing different integral-equation formulations based on the Method of Moments. The study is focused on the accuracy assessment of formulations combining normal equations (combined normal formulation, CNF), tangential equations (combined tangential formulation, CTF, and Poggio-Miller-Chang-Harrington-Wu-Tsai formulation, PMCHWT) and both of them (electric and magnetic current combined field integral equation, JMCFIE) when dealing with LHM's. Relevant and informative features as the condition number, the eigenvalues distribution and the iterative response are analyzed. The obtained results show up the suitability of the JMCFIE for this kind of analysis in contrast with the unreliable behavior of the other approaches.

COMPARISON OF SURFACE INTEGRAL EQUATIONS FOR LEFT-HANDED MATERIALS

2011-07-11

PIER

Vol. 118, 415-423, 2011

doi:10.2528/PIER11061801

download: 512

Polarization-Invariant Directional Cloaking by Transformation Optics

Krishna Agarwal, Xudong Chen, Li Hu, Hongyu Liu and Gunther Uhlmann

We propose a three-dimensional directional cloak for arbitrarily polarized incoming electromagnetic waves, motivated by the fact that there will be negligible scattering when the direction of impinging wave coincides with the axial direction of a very thin and elongated perfectly electric conducting (PEC) scatterer. The performance of the cloak under different polarizations of incoming waves are numerically investigated. The case in which the direction of incoming wave is perturbed off the ideal direction is also quantitatively studied. Numerical simulations show that the directional cloaking device is able to tolerate a large range of tilted angles of incoming waves.

POLARIZATION-INVARIANT DIRECTIONAL CLOAKING BY TRANSFORMATION OPTICS

2011-07-07

PIER

Vol. 118, 397-414, 2011

doi:10.2528/PIER11041602

download: 645

A Quasi Three-Dimensional Ray Tracing Method Based on the Virtual Source Tree in Urban Microcellular Environments

Zhong-Yu Liu and Li-Xin Guo

The increase in mobile communications traffic has led to heightened interest in the use of ray tracing (RT) methods together with digital building databases for obtaining more accurate and efficient propagation prediction in urban microcellular environments. In this paper, a novel quasi three-dimensional (3-D) RT algorithm is presented by taking into account the advantages of both the image theory (IT) and the shooting-and- bouncing ray (SBR) method. It is based on creating a new virtual source tree in which the relationship between neighbor nodes is a left-son-and-right-brother one. Our theoretical results of the signal path loss along the streets are compared with measurements which have been reported for city streets in Tokyo and Ottawa City for various values of the propagation parameters. The good agreement with these measurements indicates that our prediction model works well for such microcellular communication applications. The proposed method can provide the reliable theory basis for radio-wave propagation prediction and network planning in urban microcellular environments.

A QUASI THREE-DIMENSIONAL RAY TRACING METHOD BASED ON THE VIRTUAL SOURCE TREE IN URBAN MICROCELLULAR ENVIRONMENTS

2011-07-07

PIER

Vol. 118, 379-396, 2011

doi:10.2528/PIER11052601

download: 618

Theoretical Investigation of Rectangular Patch Antenna Miniaturization Based on the Dps-Eng BI-Layer Super-Slow TM Wave

Jiang Xiong, Hui Li, Bing-Zhong Wang, Yi Jin and Sailing He

The TM₀ surface mode in an infinitely long parallel-plate waveguide filled with a double-positive (DPS) and epsilon-negative (ENG) metamaterial bi-layer is studied. With proper constitutive parameters and thicknesses of the two layers, the slow-wave factor (SWF) for such a parallel-plate waveguide can tend to infinity as the frequency decreases. A 2-D cavity based on the DPS-ENG bi-layer waveguide is constructed and studied to evaluate the radiation ability of its corresponding patch antenna. Based on the cavity model analysis of patch antennas, we show that good efficiency for broadside radiation of such a cavity-based rectangular patch antenna can be achieved when one layer of the cavity is shielded (or partially shielded) by PEC boundaries. Taking practical loss and dispersion into consideration, a miniaturized cavity-based rectangular patch antenna is proposed as an example. With the super-slow TM₀ surface mode excited in the bi-layer by a simple coaxial line feeding, the antenna has a dimension of only 0.107λ₀×0.129λ₀×0.045λ₀. The patch antenna produces broadside radiation, and fairly good radiation efficiency is achieved. The PEC-Partially-Shielded-ENG-Cavity based rectangular patch antenna with a further miniaturization but reduced radiation efficiency is also discussed.

THEORETICAL INVESTIGATION OF RECTANGULAR PATCH ANTENNA MINIATURIZATION BASED ON THE DPS-ENG BI-LAYER SUPER-SLOW TM WAVE

2011-07-07

PIER

Vol. 118, 355-377, 2011

doi:10.2528/PIER11051910

download: 586

Field Synthesis in Inhomogeneous Media: Joint Control of Polarization, Uniformity and SAR in MRI b1-Field

Elia Amedeo Attardo, Tommaso Isernia and Giuseppe Vecchi

The homogeneity of the amplitude of one of the polarizations of the RF field B₁ is a crucial issue in Magnetic Resonance Imaging (MRI), and several methods have been proposed for enhancing this uniformity (``Shimming''). The existing approaches aim at controlling the homogeneity of B⁺₁ and limiting the Specific Absorption Rate (SAR) of the RF field by independently controlling magnitude and phase of individual excitation currents in MRI scanners, either birdcage or TEM coil system. A novel approach is presented here which allows a joint control of B⁺₁ uniformity, SAR, and purity of polarization of the total RF B₁ field. We propose a convex optimization procedure with convex constraints, and special attention has been devoted to the issue of convexity of the proposed functional. The method is applied to MRI brain imaging; numerical tests have been performed on a realistic head model at low, medium, and high RF field in order to assess the effectiveness of the proposed method. We found that maintaining a specific polarization plays an important role also in maintaining the homogeneity of B⁺₁ amplitude.

FIELD SYNTHESIS IN INHOMOGENEOUS MEDIA: JOINT CONTROL OF POLARIZATION, UNIFORMITY AND SAR IN MRI B<sub>1</sub>-FIELD

2011-07-06

PIER

Vol. 118, 335-354, 2011

doi:10.2528/PIER11060304

download: 765

Electric Field Discontinuity-Considered Effective-Permittivities and Integration-Tensors for the Three-Dimensional Finite-Difference Time-Domain Method

Yong-Gu Lee

Electric field Discontinuity-Considered Effective-Permittivities and Integration-Tensors (DC-EP&IT) for the three-dimensional Finite-Difference Time-Domain (FDTD) method are derived using a contour-path approach that considers the jump in the electric field at the interface of two dielectric materials. This is a natural but not so obvious extension to the work by Mohammandi et al. [1] from two to three-dimensions. Proposed method is verified by comparing with the exact Mie theory as well as the staircase, volume-averaged and subpixel methods.

ELECTRIC FIELD DISCONTINUITY-CONSIDERED EFFECTIVE-PERMITTIVITIES AND INTEGRATION-TENSORS FOR THE THREE-DIMENSIONAL FINITE-DIFFERENCE TIME-DOMAIN METHOD

2011-07-06

PIER

Vol. 118, 321-334, 2011

doi:10.2528/PIER11052303

download: 807

Design and Optimization of Equal Split Broadband Microstrip Wilkinson Power Divider Using Enhanced Particle Swarm Optimization Algorithm

Dong Wang, Hong Zhang, Tanghong Xu, Hao Wang and Guoguang Zhang

An enhanced particle swarm optimization (EPSO) algorithm is proposed. To improve convergence accuracy and velocity, we introduce a quadratic interpolation method and perturbation to personal best particles in EPSO. Then, a design procedure based on the EPSO is proposed for the design and optimization of equal split broadband microstrip Wilkinson power dividers (MWPDs). A set of numerical examples and fabricated samples are presented to validate the improvement of the proposed EPSO. Even-odd mode analysis is incorporated in the design procedure to calculate the scattering matrix of the MWPD on the basis of the dispersion and dissipation microstrip line model. A fitness function is then constructed according to the scattering parameters. The optimized widths and lengths of microstrip lines and values of isolation resistors are directly obtained by minimizing the fitness function. EPSO is also compared with the genetic algorithm (GA), standard particle swarm optimization (PSO) and improved particle swarm optimization (IPSO).

DESIGN AND OPTIMIZATION OF EQUAL SPLIT BROADBAND MICROSTRIP WILKINSON POWER DIVIDER USING ENHANCED PARTICLE SWARM OPTIMIZATION ALGORITHM

2011-07-06

PIER

Vol. 118, 303-319, 2011

doi:10.2528/PIER11042702

download: 542

ANN-Based Pad Modeling Technique for MOSFET Devices

Xiuping Li, Yushan Li and Junhui Zhao

In this paper, an approach for the pad modeling of the test structure for Metal Oxide Semiconductor Field Effect Transistor (MOSFET) up to 40\,GHz is presented. The approach is based on a combination of the conventional equivalent circuit model and artificial neural network (ANN). The pad capacitances and series resistors are directly obtained from EM (electromagnetic) simulation of the $S$ parameters with different size of pad and operating frequency. The parasitic elements in the test structure can be modeled by using a sub artificial neural network (SANN). So the pad capacitances and series resistors can be regarded as functions of the dimensions of the pad structure and operating frequencies by using SANN. Good agreement between the ANN-based modeling and EM simulation results has been demonstrated. In order to remove the impact of the parasitic elements, the de-embedding procedure for MOSFET device using ANN-based pad model is also demonstrated.

ANN-BASED PAD MODELING TECHNIQUE FOR MOSFET DEVICES

2011-07-05

PIER

Vol. 118, 287-301, 2011

doi:10.2528/PIER11053105

download: 586

A Slow Light Fishnet-Like Absorber in the Millimeter-Wave Range

Miguel Navarro-Cia, Victor Torres Landivar, Miguel Beruete and Mario Sorolla Ayza

A novel route to achieve a narrowband free-space electromagnetic absorber in any range of the spectrum based on stacked subwavelength hole arrays is proposed. The absorption is obtained by means of a slow light mode inside a fishnet-like engineered structure and exploiting the unavoidable misalignments and bucklings of the free-standing stack. An incoming pulse becomes permanently trapped in the structure due to the near zero group velocity which causes an enhancement of the radiation-structure interaction that leads to a huge increment of losses arising from the finite conductivity of the metal as well as arrangement tolerances. This approach is studied not only by simulation but also experimentally under normal incidence at millimeter wavelengths. Moreover, a basic grasp about the angular dependence of the structure is given by analyzing the 2D dispersion diagram. It shows that this scheme may also display high absorption under oblique incidence for s-polarization (or TE-polarization), whereas $p$-polarization (TM-polarization) would degrade its performance.

A SLOW LIGHT FISHNET-LIKE ABSORBER IN THE MILLIMETER-WAVE RANGE

2011-07-05

PIER

Vol. 118, 273-286, 2011

doi:10.2528/PIER11042005

download: 517

Impedance-Mismatched Hyperlens with Increasing Layer Thicknesses

Xuan Li, Yuqian Ye and Yi Jin

Structure with non-negative effective permittivities in the radial and tangential directions can also perform far-field imaging beyond the diffraction limit since the dispersion curves can be long and flat enough and utilized to transfer the subwavelength information. Thus we propose an impedance-mismatched hyperlens with such a dispersion curve and increasing thicknesses (from the innermost layer to the outermost) to reduce reflection losses due to the impedance difference between the nearby layer pairs. Compared with the hyperlens with same thickness for each period, the resolution ability of the hyperlens with varying thicknesses can be improved dramatically, while the image intensity is weaker. Furthermore, the influence of the layer number on the imaging is also analyzed to improve the performance of the system and an improved hyperlens with repeated thickness setting is also utilized to increase the intensity of the magnified image.

IMPEDANCE-MISMATCHED HYPERLENS WITH INCREASING LAYER THICKNESSES

2011-07-05

PIER

Vol. 118, 253-271, 2011

doi:10.2528/PIER11042905

download: 627

A Compact Dual-Polarized Broadband Antenna with Hybrid Beam-Forming Capabilities

Hong-Li Peng, Wen-Yan Yin, Jun-Fa Mao, Di Huo, Xu Hang and Liang Zhou

A broadband dual-polarized four-port (DPFP) antenna is presented in this paper, which consists of a radiation element and a feed network. It is very compact in size, with the diameter of 150.0 mm and the height of 47.0 mm, with the following unique properties: (1) it has hybrid beam-forming capability and operates at two modes, which depends on its excitation; (2) its operating frequency range is from 0.96 to1.78 GHz, and the return loss is about 10 dB; (\ref{eq3}) its insertion loss is (3±0.5) dB, with its balanced power splitting over the relative bandwidths of 37% at Mode 1 (180°±5° phase shifting) and 55% at Mode 2 (±5° phase shifting), respectively; (\ref{eq4}) an isolation of 30 dB at Mode 1 is obtained between the dual polarized ports, with the gain of 7.6 dBi and 42° of the 3 dB-bandwidth at 1.25 GHz; and (5) the gain difference between Modes 1 and 2 is about 7 dB, within the angle of -15° ≤ θ ≤ 15° for the same polarization at 1.25 GHz. For the application of DPFP, a hybrid beam forming algorithm is proposed with an angular precision of 3°, as validated by measurement.

A COMPACT DUAL-POLARIZED BROADBAND ANTENNA WITH HYBRID BEAM-FORMING CAPABILITIES

2011-07-03

PIER

Vol. 118, 243-251, 2011

doi:10.2528/PIER11060102

download: 559

Efficient Proper Orthogonal Decomposition for Backscatter Pattern Reconstruction

Chao-Fu Wang

A novel approach is presented for efficiently solving electromagnetic (EM) scattering problems using proper orthogonal decomposition (POD). As a proof of concept and demonstration of how to use the POD to solve EM scattering problems, two ways of implementing the POD procedure have been proposed and realized for calculating EM scattering from PEC targets. Numerical results obtained show that the POD is quite accurate for reconstructing backscatter patterns over wide range of frequencies and angles of interest based on the given snapshots.

EFFICIENT PROPER ORTHOGONAL DECOMPOSITION FOR BACKSCATTER PATTERN RECONSTRUCTION

2011-07-03

PIER

Vol. 118, 223-241, 2011

doi:10.2528/PIER11040902

download: 551

A Higher Order Analysis of a Class of Inhomogeneously Filled Conducting Waveguides

Ehsan Khodapanah and Saeid Nikmehr

A higher order analysis is applied to solve the problem of a class of inhomogeneously-filled conducting waveguides. This includes an arbitrary but smooth hollow conducting waveguides and waveguides filled with layered inhomogeneous materials. The method employs a set of spline-harmonic basis functions and leads to one-dimensional integrals for system matrix elements. This fact along with the higher order nature of the basis functions provides an accurate method for the analysis of the aforementioned waveguides. The accuracy and the convergence behavior of the method are studied through several numerical examples and the results are compared with the exact solutions and with the results of Ansoft HFSS simulator to establish the validity of the proposed method.

A HIGHER ORDER ANALYSIS OF A CLASS OF INHOMOGENEOUSLY FILLED CONDUCTING WAVEGUIDES

2011-07-03

PIER

Vol. 118, 205-221, 2011

doi:10.2528/PIER11050502

download: 499

Synthesis of Unequally Spaced Antenna Arrays by Using Inheritance Learning Particle Swarm Optimization

Dong Liu, Quanyuan Feng, Wei-Bo Wang and Xiao Yu

In this paper, synthesis of unequally spaced linear antenna arrays based on an inheritance learning particle swarm optimization (ILPSO) is presented. In order to improve the optimization efficiency of the PSO algorithm, we propose an inheritance learning strategy that can be applied to different topology of different PSO algorithms. In ILPSO algorithm, each cycle contains several PSO optimization processes, and uniform initial particle positions, part of which inherited from the good results in pre-cycles, are adopted in post-cycles. ILPSO enhances the exploration ability of PSO algorithm significantly, and can escape from the trap of local optimum areas with greater probability. The results demonstrate good performance of the ILPSO in solving a set of eight 30-D benchmark functions when compared to nine other variants of the PSO. The novel proposed algorithm has been applied in 32-element position-only array synthesis with three different constraints, simulation results show that ILPSO obtains better synthesis results reliably and efficiently.

SYNTHESIS OF UNEQUALLY SPACED ANTENNA ARRAYS BY USING INHERITANCE LEARNING PARTICLE SWARM OPTIMIZATION

2011-07-01

PIER

Vol. 118, 185-203, 2011

doi:10.2528/PIER11042704

download: 551

On the Feasibility of the Linear Sampling Method for 3D GPR Surveys

Ilaria Catapano, Francesco Soldovieri and Lorenzo Crocco

We discuss the applicability of the Linear Sampling Method (LSM) to GPR surveys carried out using array-based configurations. Since the images achieved via LSM are known to get worse when using a small number of antennas and a limited aperture, we introduce an analytic tool to foresee the expected LSM performance for a fixed array size and number of antennas. Notably, such a tool allows us to support (and appraise) the adoption of LSM to data collected with short arrays moved above the investigated domain, which is the configuration most viable in applications.

ON THE FEASIBILITY OF THE LINEAR SAMPLING METHOD FOR 3D GPR SURVEYS

2011-06-30

PIER

Vol. 118, 167-183, 2011

doi:10.2528/PIER11050403

download: 678

Analysis of Reflection Gratings by Means of a Matrix Method Approach

Jorge Frances Monllor, Cristian Neipp, Andres Marquez Ruiz, Augusto Belendez and Inmaculada Pascual

In this work, a matrix method is applied to study the propagation of electromagnetic waves inside a non-slanted reflection grating. The elements of the matrix which characterizes the periodic medium are obtained in terms of Mathieu functions and their derivatives, and the expressions of the efficiencies of reflected and transmitted orders are calculated in terms of the elements of the matrix. In addition the band structure of a general reflection grating is studied with the layer matrix of one single period. The results obtained by this matrix method are firstly compared to the results obtained by Kogelnik's expressions in index-matched media showing good agreement. The comparison is also made for a reflection grating embedded in two media with different refractive indexes, showing good agreement with an FDTD method, but slight differences with respect to Kogelnik's Coupled Wave Theory.

ANALYSIS OF REFLECTION GRATINGS BY MEANS OF A MATRIX METHOD APPROACH

2011-06-30

PIER

Vol. 118, 151-165, 2011

doi:10.2528/PIER11040202

download: 530

Analysis of Dependence of Resonant Tunneling on Static Positive Parameters in a Single-Negative Bilaye

Wei-Hsiao Lin, Chien-Jang Wu, Tzong-Jer Yang and Shoou-Jinn Chang

It is known that electromagnetic resonant tunneling phenomenon can be found in the single-negative (SNG) bilayer, a two-layer coating made of the epsilon-negative (ENG) and the mu-negative (MNG) media. In this work, we report that this resonant tunneling is strongly dependent on the static positive parameters in SNG materials. The values of the static permeability in ENG layer and the static permittivity in MNG layer for obtaining the resonant tunneling are theoretically analyzed and discussed for two possible cases of equal- and unequal-thicknesses. Useful design guidelines in selecting positive parameters for the resonant tunneling are obtained. We also investigate the possible influence in the resonant tunneling due to the losses from the ENG and MNG materials. Additionally, we examine the polarization-dependent resonant tunneling, that is, the dependence of angle of incidence is examined.

ANALYSIS OF DEPENDENCE OF RESONANT TUNNELING ON STATIC POSITIVE PARAMETERS IN A SINGLE-NEGATIVE BILAYE

2011-06-27

PIER

Vol. 118, 135-149, 2011

doi:10.2528/PIER11052408

download: 515

Transient Wave Propagation in a General Dispersive Media Using the Laguerre Functions in a Marching-on-in-Degree (MOD) Methodology

Baek-Ho Jung, Zicong Mei and Tapan Kumar Sarkar

The objective of this paper is to illustrate how the marching-on-in-degree (MOD) method can be used for efficient and accurate solution of transient problems in a general dispersive media using the finite difference time-domain (FDTD) technique. Traditional FDTD methods when solving transient problems in a general dispersive media have disadvantages because they need to approximate the time domain derivatives by finite differences and the time domain convolutions by using finite summations. Here we provide an alternate procedure for transient wave propagation in a general dispersive medium where the two issues related to finite difference approximation in time and the time consuming convolution operations are handled analytically using the properties of the associate Laguerre functions. The basic idea here is that we fit the transient nature of the fields, the permittivity and permeability with a series of orthogonal associate Laguerre basis functions in the time domain. In this way, the time variable can not only be decoupled analytically from the temporal variations but that the final computational form of the equations is transformed from FDTD to a FD formulation in the differential equations after a Galerkin testing. Numerical results are presented for transient wave propagation in general dispersive materials which use for example, a Debye, Drude, or Lorentz models.

TRANSIENT WAVE PROPAGATION IN A GENERAL DISPERSIVE MEDIA USING THE LAGUERRE FUNCTIONS IN A MARCHING-ON-IN-DEGREE (MOD) METHODOLOGY

2011-06-24

PIER

Vol. 118, 117-133, 2011

doi:10.2528/PIER11052403

download: 484

On the Dispersion Relations of Tapered Core Optical Fibers with Liquid Crystal Clad

Pankaj Kumar Choudhury and Patrick T. S. Ping

The paper deals with the case of a three-layer liquid crystal tapered optical fiber (LCTOF) for which the dispersion relations are deduced corresponding to the TE and the TM modes. For the LCTOF under consideration, the outermost clad section is made of liquid crystal material with radial anisotropy whereas the core and the inner clad are homogeneous, non-magnetic and isotropic dielectric regions. Rigorous field expressions corresponding to different LCTOF sections are deduced, and the eigenvalue equations are reported followed by the modal behaviour of the guide in respect of the propagation constants and cutoff situations. Apart from that, a glimpse of the power confinement through the TE and the TM excitations in different fiber sections is also touched upon.

ON THE DISPERSION RELATIONS OF TAPERED CORE OPTICAL FIBERS WITH LIQUID CRYSTAL CLAD

2011-06-24

PIER

Vol. 118, 89-116, 2011

doi:10.2528/PIER11041403

download: 757

Oscillator Accurate Linear Analysis and Design. Classic Linear Methods Review and Comments

Vicente Gonzalez-Posadas, Jose Luis Jiménez-Martín, Ángel Parra-Cerrada, Daniel Segovia-Vargas and Luis Enrique Garcia-Munoz

This paper is a deep analysis of oscillator plane reference design methods. It defines applicable conditions and the expected accuracy that can be archived with these methods. Some examples will be shown to illustrate wrong solutions that the use of linear reference plane methods can produce. The wrong solutions will be justified by necessary conditions for proper use of these methods. The strengths and weaknesses of the, widely used, plane reference methods are described in this paper. Several classic topologies of microwave oscillators, as Grounded Collector Tuned Bases (GCTB) and Grounded Bases Tuned Oscillator (GBTO), are used to illustrate these results and the additional required conditions.

OSCILLATOR ACCURATE LINEAR ANALYSIS AND DESIGN. CLASSIC LINEAR METHODS REVIEW AND COMMENTS

2011-06-24

PIER

Vol. 118, 71-87, 2011

doi:10.2528/PIER11050301

download: 554

Frequency Domain Dynamic Thermal Analysis in GaAs Hbt for Power Amplifier Applications

Than Tun Thein, Choi Look Law and Kai Fu

Dynamic temperature distributions in GaAs HBT are numerically analyzed in frequency domain as a function of power dissipation, frequency and space. Complete thermal characteristics, including frequency-dependent thermal impedance and phase lag behavior, are presented. The analysis is also extended for arbitrary periodic or aperiodic pulse heating operation to predict junction temperature of a Power Amplifier (PA) with non-constant envelope input signal. Dynamic junction temperatures of a single finger 2 μm x 20 μm GaAs HBT are predicted for square pulse envelope signal input with power levels varying with up to 10 dB above a nominal average level of 40 mW and with pulse widths ranging from 10 ns to 100 μs. With the input envelope signal amplitude of 10 dB above the average, the analytical results show that junction temperature rises from room temperature of 27^oC to 39^oC when heated by 10 ns pulse, increase to 36^oC by 100ns pulse, 105^oC by 1μs pulse and to 198^oC by 100 μs pulse. A novel setup is developed for nano-second pulsed measurements, and the analysis is validated through time domain on wafer pulsed measurements at three different power levels: 0 dB, 3 dB, and 6 dB above the average level. Results show that analytical results track well with measured junction temperature within the accuracy of ±5^oC over the entire measurement set.

FREQUENCY DOMAIN DYNAMIC THERMAL ANALYSIS IN GAAS HBT FOR POWER AMPLIFIER APPLICATIONS

2011-06-23

PIER

Vol. 118, 57-69, 2011

doi:10.2528/PIER11051709

download: 578

Millimeter Wave Microstrip Mixer Based on Graphene

George Roberto Hotopan, Samuel Ver-Hoeye, Carlos Vazquez-Antuna, Rene Camblor-Diaz, Miguel Fernandez-Garcia, Fernando Las Heras Andres, P. Alvarez and R. Menéndez

In this work, a millimeter wave microstrip frequency-mixer design based on graphene is presented. The desired frequency mixing behavior is obtained using a nonlinear component consisting in a microstrip line gap covered by a graphene layer. The circuit includes microstrip filters that have been designed to obtain a high isolation between the input and output ports. The nonlinear behavior of the frequency mixer has been experimentally evaluated in the 38.6-40 GHz input signal frequency range, for different values of the input power and local oscillator power.

MILLIMETER WAVE MICROSTRIP MIXER BASED ON GRAPHENE

2011-06-22

PIER

Vol. 118, 37-56, 2011

doi:10.2528/PIER11040810

download: 538

Transport and Electronic Properties of the GaAs Ald-Fet

Outmane Oubram, Luis Manuel Gaggero-Sager, O. Navarro and M. Ouadou

According to the scaling-down theory, the ALD-FET (Atomic Layer Doping-Field Effect Transistor) structure has attracted a lot of attention in view of its uses for developing devices with very short channels and for achieving very-high-speed operation. Therefore, there is a strong need to obtain an accurate understanding of carrier transport (mobility and conductivity) in such devices. In this work, we report the carrier transport based on the electronic structure of devices. Our results include analytical expressions of both mobility and conductivity. Our analytical expressions for the mobility and conductivity allow us to analyze transport in ALD-FET. We report regions where this device operates in digital and analogue mode. These regions are delimited in terms of intrinsic and extrinsic parameters of the system. The width of the Ohmic region as well as the NDR (Negative Differential Resistance) properties of the system are also characterized.

TRANSPORT AND ELECTRONIC PROPERTIES OF THE GaAs ALD-FET

2011-06-20

PIER

Vol. 118, 17-35, 2011

doi:10.2528/PIER11041401

download: 798

Multifolded Bandwidth Branch Line Coupler with Filtering Characteristic Using Coupled Port Feeding

Yuk Shing Wong, Shao Yong Zheng and Wing Shing Chan

A new uni-planar structure branch-line coupler with broad bandpass response is proposed. Single section branch line couplers (SSBC) are popular due to their simplicity and ease of use but suffer from narrow return loss bandwidth and poor out of band rejection characteristics. The work presented here overcomes these limitations with the use of coupled port feeding. Through the study of input impedance of feeding network and single section branch line coupler, the bandwidth of the new coupler increased by almost 6-times. In addition, the coupler exhibited band-pass filtering characteristics. Measured results exhibited low insertion loss (≤4-dB), small magnitude difference (≤1-dB), good return loss and isolation (≥10-dB) and small phase variation (90°±5) within the passband. A measured bandwidth of 58% was achieved with this single section coupled port fed branch line coupler at a centre frequency of 1-GHz. Its two output ports achieved rejection levels better than 25 dB in the stopband.

MULTIFOLDED BANDWIDTH BRANCH LINE COUPLER WITH FILTERING CHARACTERISTIC USING COUPLED PORT FEEDING

2011-06-20

PIER

Vol. 118, 1-15, 2011

doi:10.2528/PIER11051907

download: 599

Fuzzy-Control-Based Particle Filter for Maneuvering Target Tracking

Xianfeng Wang, Jun-Feng Chen, Zhi-Guo Shi and Kang Chen

In this paper, we propose a novel fuzzy-control-based particle filter (FCPF) for maneuvering target tracking, which combines the advantages of standard particle filter (SPF) and multiple model particle filter (MMPF). That is, the SPF is adopted during non-maneuvering movement while the MMPF is adopted during maneuvering movement. The key point of the FCPF is to use a fuzzy controller, which could imitate the thoughts of human beings in some degree, to detect the target's maneuver and use a backward correction sub-algorithm to alleviate the performance degradation of MMPF caused by detection delay. Simulation results indicate that the proposed algorithm has a much better tracking accuracy than the SPF while keeps approximately equal computational complexity. Compared with MMPF, both algorithms have no tracking lost, but the tracking accuracy of the proposed FCPF is a little better than the MMPF, and the FCPF consumes about 66% computation time of the MMPF. Thus, the proposed algorithm offers a more effective way for maneuvering target tracking.