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2007-08-20
PIER
Vol. 76, 485-495, 2007
download: 148
An Enhanced FDTD Model for Complex Lumped Circuits
Shao-Qiu Xiao Bing-Zhong Wang Ping Du Zhenhai Shao
One of most difficult challenges in simulating hybrid RF systems by finite-difference time-domain (FDTD) method is to construct the models for active and lumped elements. In this article, by combining the circuit equations with an integral transform, an enhanced FDTD method is proposed to model the hybrid lumped network which consists of nonlinear and high order linear elements with arbitrary connections. Based on this model, an active radiation system is analyzed. And it shows the application extension of the traditional FDTD method.
AN ENHANCED FDTD MODEL FOR COMPLEX LUMPED CIRCUITS
2007-08-18
PIER
Vol. 76, 477-484, 2007
download: 356
Triple-Band Omni-Directional Antenna for WLAN Application
Ya-Jie Wu Bao-Hua Sun Jian-Feng Li Qi-Zhong Liu
A triple-band omni-directional antenna which comprises three pairs of dipoles placed back to back and printed on a dielectric substrate is presented. A prototype is constructed and tested. The experimental results show that the 10 dB return loss bandwidth (VSWR < 2.0) in 2.4 GHz, 5.2 GHz and 5.8 GHz reaches as much as 130 MHz, 500MHz and 200 MHz, respectively. Moreover, the radiation patterns are almost omni-directional in the azimuthal plane. Peak antenna gain is 1.63 dBi, 2.36 dBi and 1.54 dBi, which indicate that the proposed antenna can be used as a triple-band antenna for the WLAN application.
TRIPLE-BAND OMNI-DIRECTIONAL ANTENNA FOR WLAN APPLICATION
2007-08-03
PIER
Vol. 76, 467-475, 2007
download: 261
Electromagnetic Wave Propagation through a Slab Waveguide of Uniaxially Anisotropic Dispersive Metamaterial
Song-Hua Liu Chang-Hong Liang Wei Ding Liang Chen Wei-Tao Pan
The characteristics of the guided electromagnetic wave propagation through a slab waveguide of uniaxially anisotropic dispersive metamaterial are investigated. Taking the cold plasma media model with ωmpz < ωmp⊥ < ωep⊥ as an example,the mode classification established in terms of the operating angular frequency ω0 of the slab waveguide. The results indicate that the mode properties are closely dependent on the frequency. When ω2 mpz < ω20 < ω2mp⊥ there are infinite guided modes. It is also found that when ω2em < ω20 < ω2mpz,there may be multiple solutions of the propagating mode with imaginary transverse wave number in a slab waveguide with thickness less than a certain value.
ELECTROMAGNETIC WAVE PROPAGATION THROUGH A SLAB WAVEGUIDE OF UNIAXIALLY ANISOTROPIC DISPERSIVE METAMATERIAL
2007-08-03
PIER
Vol. 76, 449-466, 2007
download: 239
Propagation Properties of the Spp Modes in Nanoscale Narrow Metallic Gap, Channel, and Hole Geometries
Fanmin Kong Kang Li Bae-Ian Wu Hui Huang Hongsheng Chen Jin Au Kong
The propagation properties of surface plasmon polaritons (SPP) modes in nanoscale narrow metallic structures: gap, channel, and rectangular-hole waveguides, are analyzed by the complex effective dielectric constant approximation. The results show that all the SPP modes exist below the critical frequency where the real part of metal permittivity is negative unity. It is found that both cutoff frequency and cutoff height exist in channel waveguide and rectangularhole waveguide. The channel and rectangular-hole waveguides have different propagation properties at cutoffs due to their different cutoff conditions. Compared with the gap waveguide, the channel waveguide has shorter propagation length and better confinement when the operation frequency is near the critical frequency, but has longer propagation length and worse confinement when the operation frequency is far from the critical frequency. Among the three waveguides, the rectangular-hole waveguide has the best confinement factor and the shortest propagation length. The comprehensive analysis for the gap, channel, and rectangular-hole waveguides can provide some guidelines in the design of subwavelength optical devices.
PROPAGATION PROPERTIES OF THE SPP MODES IN NANOSCALE NARROW METALLIC GAP, CHANNEL, AND HOLE GEOMETRIES
2007-08-03
PIER
Vol. 76, 427-447, 2007
download: 186
Effect of Mutual Coupling and Configuration of Concentric Circular Array Antenna on the Signal-to-Interference Performance in CDMA Systems
Rajab Fallahi Mehdi Roshandel
The suitable use of an array antenna at the base station of a wireless communication system can result in improvement in signalto- interference ratio (SIR). In the present work, we consider circular array (CA) and concentric circular antenna array (CCAA) that are used for smart antenna systems. The performance criteria for SIR improvement is employed in this paper, is the spatial interference suppression coefficient. We first develop the expression of this figure of merit for CCAA and then analyze and compare the SIR performance for various configurations of eight and nine elements of CA and CCAA, with and without the element in the center by using circular patch antenna are provided. In addition, the effect of mutual coupling (MC) is taken into account.
EFFECT OF MUTUAL COUPLING AND CONFIGURATION OF CONCENTRIC CIRCULAR ARRAY ANTENNA ON THE SIGNAL-TO-INTERFERENCE PERFORMANCE IN CDMA SYSTEMS
2007-07-30
PIER
Vol. 76, 413-425, 2007
download: 90
Improvement of Transmission Properties of Multimode Fibers Using Spread Spectrum Technique and a Rake Receiver Approach
Ioannis Kamitsos Nikolaos Uzunoglu
Multimode fibers are characterized by multipath propagation of optical signals and this leads to severe intersymbol interference at the output of the fiber. In this work an approach based on the Rake receiver is proposed to overcome this drawback. An optimization algorithm was developed and appropriate software was employed to apply the proposed methodology on specific multimode fiber. Extensive simulation results were produced and are presented herein. The numerical results have shown that the order of magnitude of the maximum data rate, R, supported at different CDMA gains, in order to achieve a Bit Error Rate value smaller or equal to a convergent point, is related to the length of the multimode fiber, L, by the expression R = dL−1 with d increasing from 106 to 107 (Kbps. m) when CDMA gain increases from 50 to 500.
IMPROVEMENT OF TRANSMISSION PROPERTIES OF MULTIMODE FIBERS USING SPREAD SPECTRUM TECHNIQUE AND A RAKE RECEIVER APPROACH
2007-07-27
PIER
Vol. 76, 397-412, 2007
download: 102
Using Photon Wave Function for the Time-Domain Analysis of Electromagnetic Wave Scattering
Bahar Khadem-Hosseinieh Y. Komijani Reza Faraji-Dana Mahmoud Shahabadi
In this paper, a generalized photon wave function (PWF) which is applicable to electromagnetic problems is introduced. The formulation treats the electromagnetics fields as quantum mechanical entities. The introduced PWF is especially useful for boundaryvalue problems. For instance,the reflection coefficient at a dielectric half space is calculated based on the concepts of PWF and quantum mechanics. With the proposed method, inhomogeneous media, both isotropic and anisotropic, can also be analyzed. It is shown that by defining certain new variables, such as effective charges and effective currents, we will be able to describe the behavior of electromagnetic fields by the proposed photon wave function. At the end of this paper, a new FDTD method based on the notion of photon wave function is introduced and the resonance frequencies of a cubic cavity are obtained.
USING PHOTON WAVE FUNCTION FOR THE TIME-DOMAIN ANALYSIS  OF ELECTROMAGNETIC WAVE SCATTERING
2007-07-27
PIER
Vol. 76, 381-395, 2007
download: 128
Bistatic Scattering from Three-Dimensional Conducting Rough Surface with UV Multilevel Partitioning Method
Zhong-Xin Li
Vector wave three-dimensional (3-D) conducting rough surface scattering problem solved by a UV method with multilevel partitioning (UV-MLP) is developed in this paper. For a 3-D conducting rough surface scattering problem, the scattering structure is partitioned into multilevel block. By looking up the rank in the static problem, the impedance matrix for a given transmitting and receiving block is expressed into a product of U and V matrix. The UV method is illustrated by applying to a 3D scattering problem of random conducting rough surface in this paper. Numerical simulation results are illustrated.
BISTATIC SCATTERING FROM THREE-DIMENSIONAL CONDUCTING ROUGH SURFACE WITH UV MULTILEVEL PARTITIONING METHOD
2007-07-27
PIER
Vol. 76, 369-379, 2007
download: 333
Design of a Ku Band Six Bit Phase Shifter Using Periodically Loaded-Line and Switched-Line with Loaded-Line
Zhigang Wang Bo Yan Rui-Min Xu Yunnchuan Guo
A Ku band six-bit phase shifter is presented in this work. The developed phase shifter consists of four bits realized as periodically loaded-line and two bits based on novel switched-line with loaded-line. A 71Ω line impedance is chosen for the main transmission line in order to reduce the diode loss. Every bit has special tuning elements for the fine tuning of the required phase shift. The phase error for the 64 phase states is not greater than 3.4 degrees at the designed center frequency of 15 GHz, and the insertion loss for the 64 phase states is 5.2 dB±1.1 dB over the operating bandwidth of 14.9-15.1 GHz.
DESIGN OF A KU BAND SIX BIT PHASE SHIFTER USING PERIODICALLY LOADED-LINE AND SWITCHED-LINE WITH LOADED-LINE
2007-07-25
PIER
Vol. 76, 357-368, 2007
download: 198
Analysis of Electromagnetics Scattering from Reflector and Cylindrical Antennas Using Wavelet-Based Moment Method
Mohamed Lashab Fatiha Benabdelaziz Chemseddine Zebiri
The aim of this work is to introduce the application of wavelet in Electromagnetic Scattering and making improvement in the moment method development. The conventional moment method basis and testing functions are used to digitalize the integral equations of the electric or magnetic field, resulting in dense matrix impedance. By using the wavelet expansion, wavelets as basis and testing functions, a sparse matrix is generated from the previous moment method dense matrix, which may save computational cost. Here application has been made upon two types of two dimensional antennas, which are circular cylindrical antennas and parabolic reflector antennas. Results are compared to the previous work done and published, excellent results are obtained.
ANALYSIS OF ELECTROMAGNETICS SCATTERING FROM REFLECTOR AND CYLINDRICAL ANTENNAS USING WAVELET-BASED MOMENT METHOD
2007-07-25
PIER
Vol. 76, 341-356, 2007
download: 144
Multi-Feed Dielectric Resonator Antenna with Reconfigurable Radiation Pattern
Hazem Fayad Paul Record
This paper describes a steerable broadband dielectric antenna with 30% fractional bandwidth, operating at 11 GHz. The structure consists of a hollow cylindrical dielectric pellet of permittivity 6 fed by four probes. Two methods are described for beam forming: 1- Beam forming has been achieved by individually switching between excited probes. The switched excitation mechanism provides the antenna with a reconfigurable radiation beam that can be moved in the azimuth plane. 2- Variable phase excitation of several probes. Complete azimuth sweep was demonstrated by both methods, allowing any desired angle of beam directions. Simulation and experimental results are presented to illustrate the advantages of both designs.
MULTI-FEED DIELECTRIC RESONATOR ANTENNA WITH RECONFIGURABLE RADIATION PATTERN
2007-07-24
PIER
Vol. 76, 327-340, 2007
download: 151
Radiation Patterns Synthesis for a Conformal Dipole Antenna Array
Qing-Qiang He Bing-Zhong Wang
A conformal cylindrical dipole array is developed in this paper. Because the conformal dipole array is curved, new far field pattern behaviors emerge. In this paper, we start to analyse the equations for the far field of the conformal dipole array by using the method of moments (MoM) with a dyadic Green's function, and then validate the accuracy of the far field expressions. Next, a novel Gauss amplitude distribution, which is capable to yield a desired far field radiation pattern when the array structure has a relative small cylindrical radius, is proposed. The advantage of the proposed method is that it can provide good aperture distributions to obtain low sidelobe level.
RADIATION PATTERNS SYNTHESIS FOR A CONFORMAL DIPOLE ANTENNA ARRAY
2007-07-24
PIER
Vol. 76, 299-326, 2007
download: 100
Complex Analysis of the Induced Currents on a Perfectly Conducting Plane Under Complex Beam Incidence
Maria-Jesus Gonzalez-Morales Emilio Gago-Ribas Carlos Dehesa-Martinez
This paper is concerned with the analysis of the currents induced on a 2D infinite perfectly conducting plane illuminated by a complex beam obtained from the analytical continuation of the real location of a unit impulse source into a complex one. The main goal considering this well-known problem is to understand the meaning of the analytical continuation and the physical information underlying the complex quantities arising from it,and to investigate the capabilities of operating in complex spaces instead of the original real ones through a simple example. Several complex quantities directly related to this problem are analysed and translated into the real domain,leading to a clear and general description of all the possible behaviours of the currents. These results will provide some new insight to extend the complex analysis methodology to more complicated scattering problems. As expected,complex analysis appears to be a full-meaning tool to obtain parameterizations of EM problems,leading to more general solutions and their physical descriptions.
COMPLEX ANALYSIS OF THE INDUCED CURRENTS ON A PERFECTLY CONDUCTING PLANE UNDER COMPLEX BEAM INCIDENCE
2007-07-22
PIER
Vol. 76, 285-298, 2007
download: 108
Computational Modeling Analysis of Radar Scattering by Clothing Covered Arrays of Metallic Body-Worn Explosive Devices
Amanda Angell Carey Rappaport
In this study, we address the problem of detecting bodyworn improvised explosive devices (IEDs) from a safe distance using radar. We have used a finite difference frequency domain (FDFD) model to simulate the radar signature of a typical scenario for bodyworn IEDs, and have analyzed wrinkled clothing as a possible source of clutter, as well as the possibility for uniform versus nonuniform array spacing of explosive-filled metal pipes. Our analysis shows distinct characteristics of the pipe backscattered farfield signal for uniformly spaced pipes, with no significant clutter added when the metallic pipe is covered with wrinkled clothing.
COMPUTATIONAL MODELING ANALYSIS OF RADAR SCATTERING BY CLOTHING COVERED ARRAYS OF METALLIC BODY-WORN EXPLOSIVE DEVICES
2007-07-22
PIER
Vol. 76, 275-284, 2007
download: 118
FDTD/TDPO Hybrid Approach for Analysis of the EM Scattering of Combinative Objects
Ling-Xia Yang De-Biao Ge Bing Wei
A time-domain hybrid approach that combines the Finite- Difference Time-Domain (FDTD) method with Time Domain Physical Optics (TDPO) is presented. The approach can be applied to the analysis of the backscattering of combinative objects including a Small- Size structure (SS) and a Large-Size structure (LS) with respect to the wavelength of interest. When dealing with the coupling of SS to LS, the near-to-near field extrapolation technique based on Kirchhoff's surface integral representation is used and a sequential transfer method is developed. According to the time domain calculation sequence in FDTD, the contribution of SS to LS is transferred directly to far zone observation point. The sequential transfer method has some advantages in high efficiency and small amounts of computer memory. For far zone back scattering, the influence of LS onto SS can be obtained by using the reciprocity theorem. Finally, the validation and application examples are presented, demonstrating the accuracy and effectiveness of this approach.
FDTD/TDPO HYBRID APPROACH FOR ANALYSIS OF THE EM SCATTERING OF COMBINATIVE OBJECTS
2007-07-20
PIER
Vol. 76, 253-274, 2007
download: 97
Bistatic Scattering from Rough Dielectric Soil Surface with a Conducting Object with Arbitrary Closed Contour Partially Buried by Using the FBM/SAA Method
Zhong-Xin Li
A hybrid approach of the forward-backward method (FBM) with spectral accelerate algorithm (SAA) and Monte Carlo method is developed in this paper. It is applied to numerical simulation of bistatic scattering from one-dimensional arbitrary dielectric constant soil surface with a conducting object with arbitrary closed contour partially buried under both the horizontal and vertical polarization tapered wave incidence at low grazing angle. The energy conservation has been checked for the FBM/SAA. Numerical simulations of bistatic scattering at low grazing angle have been discussed in this paper.
BISTATIC SCATTERING FROM ROUGH DIELECTRIC SOIL SURFACE WITH A CONDUCTING OBJECT WITH ARBITRARY CLOSED CONTOUR PARTIALLY BURIED BY USING THE FBM/SAA METHOD
2007-07-20
PIER
Vol. 76, 243-252, 2007
download: 267
A Novel Compact Planar Six-Way Power Divider Using Folded and Hybrid-Expanded Coupled Lines
Hui Chen Yu-Xing Zhang
A novel planar six-way power divider is proposed. Based on the conventional planar microstrip coupled line technology, the proposed compact six-way power divider is comprised of two stages coupled transmission lines, which is different to the conventional multistage power divider using the same expanded structure, one stage folded two-coupled line, and the other hybrid-expanded symmetrical three-coupled line. Therefore, the proposed power divider is size reduction, and has a broad-band property, which is better than 40% of fractional bandwidth. Furthermore, compared to a traditional six-way power divider, it is designed and fabricated easily. From the simulated and measured results, the six-way planar power divider shows a good specifications, which are insert loss 8.1±0.2 dB from 2 GHz to 3 GHz, and return loss less than −18 dB, isolation less than −19.5dB at 2.5 GHz, respectively.
A NOVEL COMPACT PLANAR SIX-WAY POWER DIVIDER USING FOLDED AND HYBRID-EXPANDED COUPLED LINES
2007-07-20
PIER
Vol. 76, 237-242, 2007
download: 157
A Broadband CPW-Fed T-Shape Slot Antenna
Jun-Ju Jiao Gang Zhao Fu-Shun Zhang Hong-Wei Yuan Yong-Chang Jiao
A novel broadband design of a coplanar waveguide (CPW) fed T-shape slot antenna is proposed and experimentally studied. The size of the proposed antenna is reduced by over 26% compared to the reported wide slot antenna. The obtained results show that the impedance bandwidth, determined by 10-dB return loss, of the proposed slot antenna can be as large as 5690MHz or about 121% centered at about 4.695 GHz. The design considerations for achieving broadband operation of the proposed slot antenna are described, and experimental results are presented.
A BROADBAND CPW-FED T-SHAPE SLOT ANTENNA
0000-00-00
PIER
Vol. 76, 229-236, 2007
download: 107
A Wideband Monopole with g Type Structure
Hong-Tao Zhang Ying-Zeng Yin Xi Yang
In this paper,a new monopole with G type structure is proposed,consisting of two wires rectangle rings with radius of 2 mm. The software Numerical Electromagnetic Code (NEC) is used to analyze the proposed antenna and a prototype is designed. The experimental and numerical results of the designed wideband antenna are presented and analyzed,and a 510MHz bandwidth from 0.86 GHz to 1.37 GHz is demonstrated. The experimental and numerical results fit well.
A WIDEBAND MONOPOLE WITH G TYPE STRUCTURE
2007-07-20
PIER
Vol. 76, 223-228, 2007
download: 227
Microstrip Bandpass Filter at s Band Using Capacitive Coupled Resonator
Somasandharam Prabhu Mandeep Singh Sinisa Jovanovic
A microstrip bandpass filter with a new type of capacitive coupled resonator is presented. The filter is designed to be smaller compared to the same type of parallel-coupled bandpass filter. The filter is designed for a centre frequency of 2.5 GHz that lies in the S-band frequency range. The insertion loss at ƒo is 2.4 dB and the measured 3 dB bandwidth is 8.6%. The agreement between the predicted and measured results is excellent, and even the circuit simulator gives a very good prediction for the filter characteristics.
MICROSTRIP BANDPASS FILTER AT S BAND USING CAPACITIVE COUPLED RESONATOR