Showing papers in "Progress in Electromagnetics Research B in 2014"

Dielectric Resonator Antennas: Designs and Advances

Abstract: This article presents a comprehensive review of the research carried out on Dielectric Resonator Antennas (DRAs) over the last three decades. Dielectric resonator antennas (DRAs) have received increased attention in various applications due to their attractive features in terms of high radiation e-ciency, light weight, small size and low proflle. Over last decades, various bandwidth enhancement techniques have been developed for DRAs. In this article, the attention is focused on a type of DRAs that can ofier multi-resonance frequencies and these frequencies can be merged into a broad band. In order to efiectively review design techniques, DRAs in this article are categorized into three types, broadband, ultra-wideband (UWB) and multiband. The latest developments in DRAs are discussed in the limited scope of this article.

High Bit Encoding Chipless RFID Tag Using Multiple E Shaped Microstrip Resonators

Abstract: Encoding a large number of bits within a narrow band is an important factor in the development of chipless RFID tags. A novel 8 bit chipless RFID tag with a limited bandwidth of 650 MHz is proposed here. The proposed tag comprises a multi-resonating circuit with eight E-shaped microstrip resonators in the frequency band of 3.12 to 3.77 GHz and two cross-polarized transmitting and receiving monopole antennas. The unique feature of the proposed tag is that a different set of frequencies can be derived by changing a single parameter of the structure. The prototype of the tag is fabricated on a substrate C-MET LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. Different tag combinations are designed and tested using bistatic measurement setup. Measurement results on realized prototypes are provided to ensure the reliability of the proposed design.

Finite-difference frequency-domain algorithm for modeling electromagnetic scattering from general anisotropic objects

Abstract: The flnite-difierence frequency-domain (FDFD) method is a very simple and powerful approach for rigorous analysis of electromagnetic structures. It may be the simplest of all methods to implement and is excellent for fleld visualization and for developing new ways to model devices. This paper describes a simple method for incorporating anisotropic materials with arbitrary tensors for both permittivity and permeability into the FDFD method. The algorithm is bench marked by comparing transmission and re∞ection results for an anisotropic guided-mode resonant fllter simulated in HFSS and FDFD. The anisotropic FDFD method is then applied to a lens and cloak designed by transformation optics.

Tunable Filter-Antennas for Cognitive Radio Applications

Abstract: In this paper, frequency-tunable microstrip antennas, for cognitive radio applications, are proposed. The approach is based on electrically tuning the antenna's operating frequency by integrating reconflgurable band pass fllters into wideband antenna structures. The design of an open loop resonator (OLR)-based bandstop fllter, and its transformation to a bandpass fllter, are investigated flrst. Then, the incorporation of the bandpass fllter, with a wideband antenna, is detailed. The same methodology is employed to design cognitive radio pattern and polarization diversity tunable fllter-antennas. A good agreement between the simulated and measured results for the difierent fabricated prototypes is attained.

Microwave Dielectric Properties of Ni 0.2 Cu X Zn 0.8-X FE 2 O 4 for Application in Antenna

Abstract: Structural, vibrational and microwave dielectric properties of Nickel-Copper-Zinc ferrite (Ni0.2CuxZn0.8−xFe2O4) ceramics have been presented in this paper. Samples have been prepared using conventional auto-combustion method. The X-ray diffraction (XRD) results confirmed the ferrite samples to be of cubic spinel structure, which further was validated by Fourier transform infrared (FT-IR) and Raman spectroscopy. The relative permittivity (εr) increased from 7.474 to 8.132 with successive increase in Cu content. The observed and calculated permittivity using ClausiusMossoitti relation have been in good agreement. The temperature coefficient of resonant frequency (τf ) decreased from −75.85 ppm/◦C to −32.12 ppm/◦C with increase in successive Cu content. The relative permeability (μr) have been calculated by using the Nicholson-Ross-Weir conversion technique. Using Ni0.2Cu0.2Zn0.6Fe2O4 sample the ferrite resonator antennas have been designed in three different shapes. The experimental and theoretical characteristics of the antennas have been compared and a good agreement has been achieved.

A Preprocessing Filter for Multistatic Microwave Breast Imaging for Enhanced Tumour Detection

Abstract: Ultra Wideband Radar imaging has shown promising results in the detection of small tumours within low to medium density human breasts. A wide range of beamforming algorithms has been presented in several recent studies with good tumour localization capabilities, but most of these sufier a deterioration in performance with an increase in breast tissue density. In this paper, a preprocessing fllter is used to compensate for path-dependent attenuation and phase efiects, in conjunction with a range of existing data-dependent and data-independent confocal microwave imaging algorithms. Results indicate that this data preprocessing improves the performance of all beamformers, enabling detection and accurate localization of multiple tumours in mild to moderately dense human breasts. The proposed framework is tested on 3D anatomically accurate numerical breast models and the performance is evaluated across a range of appropriate metrics.

Influence of Slots and Rotor Poles Combinations on Noise and Vibrations of Magnetic Origins in `U'-Core Flux-Switching Permanent Magnet Machines

Abstract: This paper deals with the computation of vibrations and noise of electromagnetic origin for 'U'-shaped stator core flux switching permanent magnet (FSPM) machines. The investigation concerns a family of FSPM stator/rotor configurations with 12 slots and 10, 11, 13, and 14 rotor poles. More precisely, the study focuses on the influence of different number of rotor poles on the sound power level of U-core FSPM machines. Electromagnetic forces acting on the stator frame inner surface are calculated with the Maxwell stress tensor thanks to 2-D finite element (FE) simulations. The local magnetic force density serves then as a boundary condition to the 3-D finite element vibrational simulations of the whole stator frame with housing. Finally, obtained displacements help the authors to conduct the acoustic computations using a dedicated 3-D FE analysis model. The obtained vibro-acoustic spectra help electric machines designers to make appropriate choice of stator/rotor pole combination with respect to specifications at early stages of the design process.

A New Design of Dual-Port Active Integrated Antenna for 2.4/5.2 GHz WLAN Applications

Abstract: A new design of dual-port monopole-slot-like microstrip active integrated antenna (AIA) is presented and discussed in this paper. The primary designed passive antenna is capable of supporting two difierent WLAN bands at 2.4{2.84GHz and 5.15{5.35GHz due to its dual-port structure. In order to reduce the transmission coe-cient between the two ports of antenna a coupling sleeve-arm and an inverted T-shaped slot are utilized on the ground plane of antenna each beneath one of the corresponding feed-lines which act as flltering structures at desirable frequencies. The proposed passive dual-port antenna is integrated with a power amplifler (PA) and a low noise amplifler forming a dual- port microstrip AIA which can be used as a full-duplex transceiver at its operating WLAN frequency bands. The measured results for both passive and active antennas show that the designed antennas have proper radiation characteristics at their desired operation frequencies. The fabricated passive antenna exhibits dual-band performance at 2{3.42GHz and 4.5{5.6GHz while the fabricated AIA covers 2.31{ 2.82GHz (at PA port) and 4.45{5.5GHz (at LNA Port) with 13dB and 9dB gain level improvement respectively.

Analysis of Microstrip Line Feed Slot Loaded Patch Antenna Using Artificial Neural Network

Abstract: In this article, the parametric analysis of the slot-loaded microstrip line feed patch antenna is investigated using artiflcial neural network model. The bandwidths of the proposed antenna obtained at TM01, TM02, and TM03 frequency modes are 10.2GHz, 13.6GHz, and 17.2GHz, respectively. The performance of the proposed antenna is analyzed using artiflcial neural network model. The changes obtained in bandwidth due to the position of slot length and slot width are reported. The antenna parameters such as return loss, VSWR, gain and e-ciency are also calculated. The simulated results obtained with the help of IE3D simulation software are trained and tested using ANN. Theoretical results are compared with simulated and experimental ones, and they are in close agreement. Microstrip antennas have sparked interest among researchers because of their attractive features like low proflle, light weight, and conformal to mounting structures, but they have two most serious limitations, narrow bandwidth and low gain (1). Available methods for the analysis of MSA have high level of complexity. Generally, there are two methods for analysis of microstrip antenna such as numerical method and analytical method. The numerical methods is complicated compared to analytical methods and require much more time, whereas, analytical methods are easy and specifled to only some deflnite shapes of microstrip antenna. An artiflcial neural network (ANN) is used here for reducing some of these problems. ANNs are computational tools that learn from experience (training), which provide fast and accurate models for microwave modeling, simulation, and optimization. Using artiflcial neural network microstrip patch antenna was reported by Vegni and Toscano (2) in which they proposed the analysis of MSA using artiflcial neural network. Further, Mishra and Patnaik (3,4) proposed a CAD model for the design of square patch antenna and artiflcial model for efiective dielectric constant of microstrip line. Later, CAD model using spectral domain formulation (5) was also reported for the designing of rectangular patch antenna. Therefore, Guney and Sarikaya (6) proposed a comparative study of MAMDANI and Sugeno fuzzy interface system models for the resonant frequency calculation of rectangular microstrip patch antenna. Several other papers have also used ANN model to analyze and synthesize the microwave circuits (7{15). Thakare and Singhal (16) proposed the analysis of broadband slot-loaded inset feed microstrip patch antenna using ANN model. Most of these papers are based on ANN model presented only simulated and experimental results. In this paper, we provide a theoretical investigation and compare its results with simulated and experimental ones. In this paper, the microstrip line feed slot-loaded patch antenna is proposed. Its theoretical, simulated and ANN results have also been verifled experimentally. The proposed antenna is investigated for triple frequency-band operation, so that single antenna can be utilized for more than one frequency bands. The theoretical analysis of the proposed antenna is discussed using circuit theory concept based on modal expansion cavity model whereas ANN used RBFNN model.

Experimental Characterization of the Propagation Channel along a Very Large Virtual Array in a Reverberation Chamber

Abstract: We show that the combined use of radio frequency absorbers and directive antennas can produce significant changes of the radio propagation channel properties along the positions of a virtual array ...

Investigation of the Effect of Ionospheric Gradients on GPS Signals in the Context of Laas

Abstract: Local Area Augmentation System (LAAS) is expected to enable the pilots to guide the aircraft more precisely and safely into busy airports even in poor visibility conditions. The anomalous low and equatorial latitude Ionosphere is severe threat to the LAAS system. To characterize the anomalous ionospheric gradients, the performance of an ionospheric threat model is evaluated. In our investigation, in contrast to the reported work available in the open literature, smoothed code phase measurements are used in the threat model to obtain precise ionospheric time delay. The three key parameters of the threat model gradient slope (mm/km), width (km) and front speed (m/s) are used in the analysis. Further, geometry screening using Maximum Ionosphere Induced Error in Vertical (MIEV) as a key parameter is carried out to identify the stationary gradients and its impact on system performance for CAT-I operations. A maximum ionospheric gradient of 355.74mm/km over a distance of approximately 75km is reported at mid latitudes. Whereas, in our flndings at low/equatorial latitudes even within a distance of approximately 4km a maximum gradient of 460mm/km is observed, which is comparatively very high. Our results show that, there is necessity to enhance upper bound for the ionospheric gradients threat space over low latitudes.

Design of Asymmetric Slot Antenna with Meandered Narrow Rectangular Slit for Dual Band Applications

Abstract: A compact, coplanar waveguide (CPW) fed asymmetric slot antenna with dual operating bands is proposed. The slot is modifled rectangular in shape and asymmetrically cut in the ground plane. A hexagonal patch fed by a two-step CPW is used to excite the slot. The feed itself is slightly asymmetric (shifted, with unequal ground planes). The asymmetric cuts on the slot together with the feed line asymmetry have helped in obtaining ultra wideband impedance matching. An extra resonance at 2.4GHz for Bluetooth applications is obtained by cutting an additional meandered narrow rectangular shape slit in the ground plane. The prototype of the proposed antenna has been fabricated and tested. The measured 10dB return loss bandwidth of the proposed antenna is 200MHz (2.3{2.5GHz) for the flrst band and 12.1GHz (2.9{15.0GHz) for the second band. The radiation patterns of the proposed antenna are obtained and found to be Omni-directional in H-plane and bi-directional in E-plane. The measured and simulated results are in good agreement.

Patch and Ground Plane Design of Microstrip Antennas by Material Distribution Topology Optimization

Abstract: We use a gradient-based material distribution approach to design conductive parts of microstrip antennas in an efficient way. The approach is based on solutions of the 3D Maxwell's equation compute ...

Ground Fault Current Distribution When a Ground Fault Occurs in Hv Substations Located in an Urban Area

Abstract: The paper presents a method of determination of ground fault current distribution when HV (high voltage) substations are located in urban or suburban areas, or where many relevant data necessary for determination of this distribution are uncertain or completely unknown. The problem appears as a consequence of the fact that many of urban metal installations are situated under the surface of the ground and cannot be visually determined or verifled. On the basis of on-the-site measurements, the developed method enables compensating all deflciencies of the relevant data about metal installations involved with the ∞uctuating magnet fleld appearing around and along a feeding power line during an unbalanced fault. The presented analytical procedure is based on the fact that two measurable quantities, currents in one phase conductor and in one neutral line conductor, cumulatively involve the inductive efiects of all, known and unknown surrounding metal installations. Once, this quantity has been determined, the problem of determination of difierent parts of a ground fault current becomes solvable by using a relatively simple calculation procedure. The presented quantitative analysis indicates at the beneflts that can be obtained by taking into account the presence of surrounding metal installations.

Imaging of 3-D Dielectric Objects Using Far-Field Holographic Microwave Imaging Technique

Abstract: This paper describes the working principle of a three-dimensional (3-D) holographic microwave imaging (HMI) method for imaging small inclusion embedded in a dielectric object. Using published dielectric properties of various materials, a 3-D mathematical model is developed under the MATLAB environment to validate the HMI on various dielectric objects. Results indicate that the 3-D HMI has an ability to produce a 3-D image and detect small inclusions embedded within a dielectric object. Several potential applications of the 3-D HMI method includes biological tissues imaging, security screening and packaged food evaluation.

Electromagnetic Wave Scattering from Rough Layered Interfaces: Analysis with the Small Perturbation Method and the Small Slope Approximation

Abstract: We propose a theoretical study on the electromagnetic wave scattering from layered structures with an arbitrary number of rough interfaces by using the small perturbation method and the small slope approximation. The interfaces are characterized by Gaussian height distributions with zero mean values and Gaussian correlation functions. They can be correlated or not. The electromagnetic fleld in each medium is represented by a Rayleigh expansion and a perturbation method is used for solving the boundary value problem and determining the flrst-order scattering amplitudes by recurrence relations. The scattering amplitude under the flrst-order small slope approximation are deduced from results derived from the flrst-order small perturbation method. Comparison between these two analytical models and a numerical method based on the combination of scattering matrices is presented. The study of electromagnetic wave scattering from rough layered interfaces has many applications in remote sensing, communication techniques, civil engineering, geophysics and optics. Several models give the average scattered fleld and the average intensity. Analytical methods are based on physical approximations and give closed-form formulae for the flrst- and second-order moments of the scattered fleld. Exact methods estimate the average scattered fleld and the average intensity from the results over many realizations of rough layered interfaces. In this paper, we propose a theoretical study on the electromagnetic wave scattering from layered structures with an arbitrary number of rough interfaces by using two analytical models: the flrst-order small perturbation method (SPM) and the flrst-order small slope approximation (SSA). Elson was one of the flrst authors to develop a vector theory of scattering from a stratifled medium. This vector theory allows the angular distribution of scattered light to be determined and can be used with correlated or uncorrelated surface roughness (1,2). The SPM has been used for the study of light scattering from multilayer optical coatings (1{5) and many authors have also implemented a perturbative theory for analyzing remote sensing problems (6{12). The small slope approximation (SSA1) has an extended domain of applicability (13{15) which includes the domain of the small-perturbation method that is only valid for surfaces with small roughness (16) and the domain of the Kirchhofi approximation that is applicable to surfaces with long correlation length (17,18). In the present paper, the structure under consideration is a stack of several rough one-dimensional interfaces. The interfaces are characterized by Gaussian height distributions with zero mean values and Gaussian correlation functions. The electromagnetic fleld in each region is represented by a continuous spectrum of plane waves, the amplitudes of which are found by matching the boundary conditions

Fully Time-Domain Scanning of EM Near-Field Radiated by RF Circuits

Abstract: This paper deals with planar scanning technique of electromagnetic (EM) near-fleld (NF) emitted by electronic printed circuit boards (PCBs) fully in the time-domain (TD). The proposed EM scanning metrology is essentially based on the NF test bench available at the IRSEEM laboratory. It comprises motorized mechanical structures for moving the probe interconnected to electronic measurement instruments and controlled by a driver PC. The synoptic of the test bench is presented and technically examined. The characteristics of difierent elements constituting the measurement chain of the TD test bench understudy are described. The NF metrology developed is originally focused on the measurement of time-dependent magnetic fleld H(t) dedicated to the radiated emission electromagnetic compatibility (EMC) applications. An innovative calibration technique of the loop probe for detecting H(t) is established in order to ensure the post processing and extraction of the measured NF data. Then, validations were carried out via comparison with difierent simulations run with standard commercial tools. Mathematical analyses were also conducted for the improvement of the measurement post processing. To realize the mapping of time-dependent EM fleld components, a software interface edited with the graphical language LabVIEW was emulated to synchronize the probe displacement and the data acquisition. An UWB amplifler with average gain about 30dB from DC to 300MHz was designed and fabricated in order to decrease the measurement noise and to improve the quality of measured signals. As results of the study, TD NF mapping is demonstrated successfully by measuring the EM radiation emitted by electronic planar circuits. The technique developed is extremely useful in the fleld of EMC engineering for predicting the transient perturbations susceptible to degrade electronic functions in complex systems encountered usually for the automotive and aeronautic applications.

Feasibility Investigation of Low Cost Substrate Integrated Waveguide (SIW) Directional Couplers

Abstract: In this paper, the feasibility of Substrate Integrated Waveguide (SIW) couplers, fabricated using single-layer TACONIC RF-35 dielectric substrate is investigated. The couplers have been produced employing a standard PCB process. The choice of the TACONIC RF-35 substrate as alternative to other conventional materials is motivated by its lower cost and high dielectric constant, allowing the reduction of the device size. The coupler requirements are 90-degree phase shift between the output and the coupled ports and frequency bandwidth from about 10.5GHz to 12.5GHz. The design and optimization of the couplers have been performed by using the software CST Microwave Studio c ∞ . Eight difierent coupler conflgurations have been designed and compared. The better three couplers have been fabricated and characterized. The proposed SIW directional couplers could be integrated within more complex planar circuits or utilized as stand-alone devices, because of their compact size. They exhibit good performance and could be employed in communication applications as broadcast signal distribution and as key elements for the construction of other microwave devices and systems.

Inhomogeneous and Homogeneous Losses and Magnetic Field Effect in Planar Undulator Radiation

Abstract: We construct an analytical model for the description of emission of undulator radiation (UR) harmonics with account for several sources of line broadening, including the efiect of a constant magnetic constituent. We compare it with that of the beam energy spread, emittance and focusing components. The analytical expressions obtained for the UR intensity and spectrum allow for profound analysis of homogeneous and inhomogeneous losses in their explicit form. We analyse the contributions to the fundamental frequency as well as to higher harmonics in long undulators. We study a possibility to compensate for the ofi-axis efiects in undulators by a properly imposed constant magnetic fleld and obtain an expression for the intensity of such compensating efiect. The results obtained are discussed in the context of their possible applications to free electron lasers (FEL). Recommendations for improvement of an UR harmonic line quality, profltable for FEL, are also proposed.

The Three-Transponder Method: A Novel Method for Accurate Transponder RCS Calibration

Abstract: Transponders (also known as polarimetric active radar calibrators or PARCs) are commonly used for radiometric calibration of synthetic aperture radars (SARs). Currently three methods for the determination of a transponder's frequency-dependent radar cross section (RCS) are used in practice. These require either to measure disassembled transponder components, or a separate radiometric measurement standard (like a flat, metallic plate or a corner reflector), leading to additional uncertainty contributions for the calibration result. In this paper, a novel method is introduced which neither requires disassembly nor an additional radiometric reference. Instead, the measurement results can be directly traced back to a realization of the meter, lowering total measurement uncertainties. The method is similar in approach to the well known three-antenna method, but is based on the radar equation instead of Friis transmission formula. The suitability of the method is demonstrated by a measurement campaign for DLR's three new Kalibri C-band transponders, completed by an uncertainty analysis. The method is not universally applicable for all transponder calibrations because (a) three devices are necessary (instead of only one for the known methods), and (b) the transponders must provide certain additional features. Nevertheless, these features have become standard in modern SAR calibration transponder designs. The novel, potentially more accurate three-transponder method is thus a viable alternative for transponder RCS calibration, ultimately contributing to synthetic aperture radars with a reduced radiometric measurement uncertainty.

Calculation of the Mutual Coupling Parameters and Their Effects in 1-D Planar Almost Periodic Structures

Abstract: This paper proposes a new modal analysis based on Floquet's theorem which is needful for the study of a 1-D periodic phased array antenna excited by arbitrary located sources. This analysis requires an accurate estimation for calculation of the mutual coupling parameters (for example: mutual impedances or admittances ...) between the array elements and their efiects integrating a large planar radiating structure. Two difierent formulations are suggested, in spectral and spatial domains, to solve the problem and to calculate the coupling coe-cients between the neighbouring elements in a periodic environment. Important gain in the running time and used memory is obtained using Floquet analysis. One numerical method is used for modeling the proposed structures: the moment method combined with Generalized Equivalent Circuit (MoM-GEC).

Design and Analysis of a Compact Triple Band Slotted Microstrip Antenna with Modified Ground Plane for Wireless Communication Applications

Abstract: A novel single layer, coaxial probe feed compact triple band slotted microstrip patch antenna with modifled ground plane for wireless application has been designed and analyzed. The presented antenna, occupying a compact size of 24 £ 22 £ 1:6mm 3 , embodies a rectangular slotted patch and a rectangular ground plane modifled with open ended step graded slots. The step graded slots are introduced on the ground plane to reduce the size of the antenna by reducing the resonant frequency and also to improve the operating bandwidth of the proposed antenna. The size of the antenna has been reduced by 74% by introducing slots on the ground plane. The measured bandwidths for i10dB re∞ection coe-cient are 360MHz (1.72{2.08GHz) at lower band, 300MHz (3.36{3.66GHz) at middle band and 3650MHz (4.85{8.5GHz) at upper band which cover the bandwidth requirements of 1.92GHz PCS, 1.9GHz PHS, 3.5/5.5GHz WiMAX, 5.2/5.8GHz WLAN, 5.2GHz HisWaNa and 5GHz HiPERLAN wireless application bands.

Ducting and Turbulence Effects on Radio-Wave Propagation in an Atmospheric Boundary Layer

Abstract: The split-step Fourier (SSF) algorithm is applied to simulate the propagation of radio waves in an atmospheric duct. The refractive-index fluctuation in the ducts is assumed to follow a two- dimensional Kolmogorov power spectrum, which is derived from its three-dimensional counterpart via the Wiener-Khinchin theorem. The measured profiles of temperature, humidity and wind speed in the Gulf area on April 28, 1996, are used to derive the average refractive index and the scaling parameters in order to estimate the outer scale and the structure constant of turbulence in the atmospheric boundary layer (ABL). Simulation results show significant turbulence effects above sea in daytime, under stable conditions, which are attributed to the presence of atmospheric ducts. Weak turbulence effects are observed over lands in daytime, under unstable conditions, in which the high surface temperature prevents the formation of ducts.

Microwave Model of Radiation from the Multilayer \Ocean-Atmosphere" System for Remote Sensing Studies of the Polar Regions

Abstract: Microwave model for simulation of radiation from the multilayer system \sea surface-sea ice- snow cover-atmosphere" is introduced. In the general case, ice and snow cover is modelled by multilayer medium, where every layer is characterized by its speciflc physical parameters. Electrodynamical properties of each layer are determined from the original authors' model of the efiective permittivity of heterogeneous medium. This model takes into account efiects of radiation scattering on irregularities of environment. Measurable physical characteristics of sea ice and snow are used as the model input data. This advantage allows using this model for interpretation of remote sensing images of the ice cover in the Polar Regions. Major attention is drawn to comparison of model calculations with satellite data and visual observations from ships. The collection of SSM/I and SSMIS images from GLOBAL-RT data base, and processed visual observations from ships in Arctic cruises were used. Observations data served as the input parameters for electrodynamical model. Comparison of model results with SSM/I images demonstrated good coincidence at various frequencies.

A Mathematical Model for the Transient Lightning Response from Grounding Systems

Abstract: With the Fast Fourier Transform (FFT), a mathematical model for accurately computing distribution of a lightning currents ∞owing along a high voltage a.c. substation's grounding system buried in half inflnite homogenous earth has been developed in this paper. It is a hybrid of Galerkin's method of moment (MoM) and a conventional nodal analysis method. The model can directly calculate the distribution of both branch and leakage currents along the grounding system. A dynamic state complex image method and a closed form of Green's function of a dipole or monopole in the half inflnite homogenous earth model are introduced into this model to accelerate calculations of mutual impedance and induction coe-cients. Analytical formulae for the mutual induction and impedance coe-cients have been developed to accelerate the calculation for near fleld case by using Maclaurin expansion. With the inverse FFT, the model can be used to study the transient lightning response of a grounding system.

Analysis of Temporal Polarization Phase Difference for Major Crops in India

Abstract: A polarimetric radar system measures the complete scattering matrix of a target in the backscattered fleld that includes magnitudes of linearly polarized scattering amplitudes and the co- polarised and cross-polarised phase angles. Apart from backscattering intensity, the co-polarization phase difierence (CPD) calculated from polarimetric synthetic aperture radar (SAR) data produces important information about target physical, geometrical and dielectric properties. In the present work, the distribution of CPD in C-band polarimetric SAR data corresponding to major kharif and rabi crops (denoting the monsoon and the winter season) and other land cover features have been studied over Central State Farm, Hisar, Haryana. The probability density functions (PDF) of CPD have been compared with dominant scattering contributions from these targets as obtained from polarimetric target decompositions. The results show that crops and other land cover features show characteristic CPD distributions, which relates well with crop physical and geometrical properties. An intuition of the rate of growth and plant vigour is indicative from the temporal PDF pattern.

A Comparative Study of Material Leucaena Leucocephala Stem Wood Plastic Composite (Wpc) Substrate with Fr4 Substrate Throughout Single Patch Antenna Design

Abstract: The fabrication of single square patch antenna for proposed Leucaena Leucocephala (\Petai Belalang") Wood Plastic Composite (WPC) substrate board (PB Substrate board) and FR4 substrate board is presented in this paper. The experiment objective is to measure the performance of an antenna fabricated on the FR4 and PB substrate (proposed substrate) by comparing the performance in terms of material's dielectric constant and electron mobility and antennas' loss tangent, return loss (S11), radiation pattern and practical antenna transmitting performance. The new substrate compositions of Leucaena Leucocephala stem and polypropylene (PP) are 30% and 70% consecutively. The result for 150"m (sample B) indicates stability on most dielectric constant ("r = 3:02), loss tangent (tan- = 0:029) and electron mobility (5:31 £ 10 3 cm 2 /Vs), with the consistency of antenna result, between simulation and measurement. All results obtained will be analyzed and displayed in the form of data and graphs.

Channel Modelling and Performance Analysis of V2I Communication Systems in Blind Bend Scattering Environments

Abstract: In this paper, we derive a new geometrical blind bend scattering model for vehicle-to- infrastructure (V2I) communications. The proposed model takes into account single-bounce and double- bounce scattering stemming from flxed scatterers located on both sides of a curved street. Starting from the geometrical blind bend model, the exact expression of the angle of departure (AOD) is derived. Based on this expression, the probability density function (PDF) of the AOD and the Doppler power spectrum are determined. Analytical expressions for the channel gain and the temporal autocorrelation function (ACF) are provided under non-line-of-sight (NLOS) conditions. Additionally, we investigate the impact of the position of transmitting vehicle relatively to the receiving road-side unit on the channel statistics. Moreover, we study the performance of difierent digital modulations over a sum of singly and doubly scattered (SSDS) channel. Note that the proposed V2I channel model falls under the umbrella of SSDS channels since the transmitted signal undergoes a combination of single-bounce and double-bounce scattering. We study some characteristic quantities of SSDS channels and derive expressions for the average symbol error probability of several modulation schemes over SSDS channels with and without diversity combining. The validity of these analytical expressions is conflrmed by computer-based simulations.

A Compact Multiband Planar Monopole Antenna for Slim Mobile Handset Applications

Abstract: A planar compact multiband monopole antenna is presented for ultra-slim mobile handset applications. The proposed antenna operates over 0.885 GHz-0.962 GHz and 1.69 GHz-3.8 GHz frequency bands with −6 dB impedance bandwidth that covers GSM900, GSM1800, GSM1900, UMTS, IMT2100, WLAN, WiMAX along with most of the higher LTE bands of modern mobile phone applications. The radiation characteristics of the antenna is analyzed in term of radiation patterns, peak realized gain, total radiation efficiency, and surface current distribution. The radiation patterns of the proposed antenna are dipole like which is suitable for mobile applications with 73-93% total radiation efficiency. The proposed antenna is investigated in free space as well as in actual mobile environment consisting of mobile plastic housing along with large metallic display screen and battery. No significant effect on the operating bands of the mobile antenna due to the actual mobile environment on the impedance bandwidth is observed. Specific absorption rate (SAR) computation is carried out on human head phantom. The computed values of SAR lie well below the specified limit over 1 g and 10 g of tissues. The parametric analysis is also carried out to understand the effect of the shape parameters.