Showing papers in "Progress in Electromagnetics Research-pier in 2007"
TL;DR: Central Force Optimization is a new deterministic multi-dimensional search metaheuristic based on the metaphor of gravitational kinematics that models “probes” that “fly” through the decision space by analogy to masses moving under the influence of gravity.
Abstract: Central Force Optimization (CFO) is a new deterministic multi-dimensional search metaheuristic based on the metaphor of gravitational kinematics. It models “probes” that “fly” through the decision space by analogy to masses moving under the influence of gravity. Equations are developed for the probes’ positions and accelerations using the analogy of particle motion in a gravitational field. In the physical universe, objects traveling through threedimensional space become trapped in close orbits around highly gravitating masses, which is analogous to locating the maximum value of an objective function. In the CFO metaphor, “mass” is a userdefined function of the value of the objective function to be maximized. CFO is readily implemented in a compact computer program, and sample pseudocode is presented. As tests of CFO’s effectiveness, an equalizer is designed for the well-known Fano load, and a 32-element linear array is synthesized. CFO results are compared to several other optimization methods.
390 citations
TL;DR: A wideband E-shaped microstrip patch antenna has been designed for high-speed wireless local area networks (IEEE 802.11a) and other wireless communication systems covering the 5.15-5.825 GHz frequency band.
Abstract: A wideband E-shaped microstrip patch antenna has been designed for high-speed wireless local area networks (IEEE 802.11a standard) and other wireless communication systems covering the 5.15-5.825 GHz frequency band. Two parallel slots are incorporated to perturb the surface current path, introducing local inductive effect that is responsible for the excitation of the second resonant mode. The length of the center arm can be trimmed to tune the frequency of the second resonant mode without affecting the fundamental resonant mode. A comprehensive parametric study has been carried out to understand the effects of various dimensional parameters and to optimize the performance of the antenna. A substrate of low dielectric constant is selected to obtain a compact radiating structure that meets the demanding bandwidth specification. The reflection coefficient at the input of the optimized E-shaped microstrip patch antenna is below -10 dB over the entire frequency band. The measurement results are in excellent agreement with the HFSS simulation results.
300 citations
198 citations
TL;DR: In this article, various types of nonlinear effects based on first effect such as self phase modulation, cross-phase modulation, and four-wave mixing are discussed and a comparative study of these effects is presented.
Abstract: The nonlinear effects in optical fiber occur either due to intensity dependence of refractive index of the medium or due to inelastic-scattering phenomenon. This paper describes various types of nonlinear effects based on first effect such as self-phase modulation, cross-phase modulation and four-wave mixing. Their thresholds, managements and applications are also discussed; and comparative study of these effects is presented.
194 citations
TL;DR: In this paper, a modified Printed Tapered Monopole Antenna (PTMA) is proposed for ultra wideband (UWB) wireless communication applications. But the antenna has a small area of 23 × 26.5 mm2 and offers an impedance bandwidth as high as 100% at a centre frequency of 7.2 GHz for S11 < −10 dB.
Abstract: This paper presents a novel modified Printed Tapered Monopole Antenna (PTMA) for ultra wideband (UWB) wireless communication applications. The proposed antenna consists of a truncated ground plane and two-tapered radiating patch separated by a slot (air gap) of different slopes, which provides a wideband behavior and relatively good matching. Moreover, the effects of a modified T-shaped slot inserted in the first tapered patch, on the impedance matching is investigated. The antenna has a small area of 23 × 26.5 mm2 and offers an impedance bandwidth as high as 100% at a centre frequency of 7.2 GHz for S11 < −10 dB, which has an area reduction of 15% and a frequency bandwidth increment of 72% with respect to the previous similar antenna. The presented antenna covers the 5.2/5.8 GHz WLAN and 5.5 GHz WIMAX operating bands. Numerical analysis using Ansoft HFSS and measurement results is also presented in the paper.
148 citations
TL;DR: In this paper, a band-pass Substrate Integrated Waveguide (SIW) filter based on complementary split ring Resonators (CSRRs) was proposed for transmission zero control.
Abstract: A novel band-pass Substrate Integrated Waveguide (SIW) filter based on Complementary Split ring Resonators (CSRRs) is presented in this work. Three different CSRRs cells are etched in the top plane of the SIW for transmission zero control. A demonstration band-pass filter is designed, fabricated and measured. It agreed with the simulated results well.
141 citations
TL;DR: In this paper, a multiband CPW-fed triangle-shaped monopole antenna for wireless applications covering 2.4 and 5 GHz WLAN bands and 3.4 GHz WIMAX band in IEEE 802.16 is proposed.
Abstract: A multiband CPW-fed triangle-shaped monopole antenna for wireless applications covering 2.4and 5 GHz WLAN bands and 3.4 GHz WIMAX band in IEEE 802.16 is proposed. Prototype of the proposed antenna have been constructed and tested. The experimental results show that the antenna can provide two separate impedance bandwidths of 140 MHz (about 5.8% centered at 2.43 GHz) and 3100 MHz (about 61.4% centered at 4.91 GHz), which meet the required bandwidths specification of 2.4/5 GHz WLAN and 3.4 GHz WIMAX standard. Good omnidirectional radiation in the desired frequency bands has been achieved. The proposed antenna with relatively low profile is suitable for multiband wireless applications.
132 citations
TL;DR: An efficient method based on bees algorithm for the pattern synthesis of linear antenna arrays with the prescribed nulls is presented and numerical examples of Chebyshev pattern with the single, multiple and broad nulls imposed at the directions of interference are given.
Abstract: An efficient method based on bees algorithm (BA) for the pattern synthesis of linear antenna arrays with the prescribed nulls is presented. Nulling of the pattern is achieved by controlling only the amplitude of each array element. Numerical examples of Chebyshev pattern with the single, multiple and broad nulls imposed at the directions of interference are given to show the accuracy and flexibility of the BA.
130 citations
TL;DR: In this paper, a novel broadband design of a coplanar waveguide (CPW) fed T-shape slot antenna is proposed and experimentally studied, where the size of the proposed antenna is reduced by over 26% compared to the reported wide slot antenna.
Abstract: 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 5690 MHz 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.
120 citations
TL;DR: To compact the structure, this paper proposes a new single layer square loop FSS configuration that operates in two frequency bands such as multi-layer SL-FSS and simulation results are shown to have good agreement with experimental results.
Abstract: A superstrate layer is used to enhance the directivity of the small radiation sources such as Microstrip Patch Antennas. In this paper, we use square loop frequency selective surface (SLFSS) configuration to design the superstrate layer. To compact the structure, we propose a new single layer square loop FSS configuration that operates in two frequency bands such as multi-layer SL-FSS. Simulation results are shown to have good agreement with experimental results.
119 citations
TL;DR: In this paper, circular and hexagonal array geometries for smart antenna applications are compared and the method of moments is used to compute the response of the uniform circular and Hexagonal dipole arrays in a mutual coupling environment.
Abstract: In this paper, circular and hexagonal array geometries for smart antenna applications are compared. Uniform circular (UCA) and hexagonal arrays (UHA) with 18 half-wave dipole elements are examined; also planar (2 concentric rings of radiators) uniform circular (PUCA) and hexagonal arrays (PUHA) are considered. The effect of rotating the outer ring of the PUCA is studied. In our analysis, the method of moments is used to compute the response of the uniform circular and hexagonal dipole arrays in a mutual coupling environment. The particle swarm optimization (PSO) algorithm is used to optimize the complex excitations, amplitudes and phases, of the adaptive arrays elements for beamforming.
TL;DR: In this paper, a novel ring monopole antenna with double meander lines is proposed for wireless local area networks (WLAN) applications in IEEE 802.11b/g/a systems.
Abstract: A novel compact ring monopole antenna with double meander lines is proposed for wireless local area networks (WLAN) applications in IEEE 802.11b/g/a systems. The designed antenna, fed by a 50 Ω microstrip transmission line, is only 32 mm in height and 16 mm in width. By introducing a horizontal and a vertical branched strips to a closed rectangular strip ring, the proposed antenna can generate two separate impedance bandwidths. Prototypes of the proposed antenna have been constructed and tested. The obtained impedance bandwidths reach about 12% for the 2.4 GHz band and 45.3% for the 5 GHz band, which meet the required bandwidth specification of 2.4/5 GHz WLAN standard. Also, good radiation performance and antenna gain over the two frequency ranges have been obtained.
TL;DR: In this paper, an optimization method based on real-coded GA with elitist strategy for thinning a large linear array of uniformly excited isotropic antennas to yield the maximum relative sidelobe level (SLL) equal to or below a fixed level.
Abstract: In this paper, we propose an optimization method based on real-coded genetic algorithm (GA) with elitist strategy for thinning a large linear array of uniformly excited isotropic antennas to yield the maximum relative sidelobe level (SLL) equal to or below a fixed level. The percentage of thinning is always kept equal to or above a fixed value. Two examples have been proposed and solved with different objectives and with different value of percentage of thinning that will produce nearly the same sidelobe level. Directivities of the thinned arrays are found out and simulation results of different problems are also compared with published results to illustrate the effectiveness of the proposed method.
TL;DR: In this paper, the transmission coefficient of a thin dielectric slab placed in a waveguide has been derived for the measurement of the Teflon reflectance, and the exact solution for transmission through a thin sample is presented.
Abstract: Apractical problem in the reflection method for dielectric constant measurement is the difficulty to ensure the sample is placed exactly at the waveguide flange. Asmall position offset of the dielectric sample will give rise to some errors in calculating the dielectric constant, especially when a thin sample is used. To circumvent this problem, a method to determine the dielectric constant by measuring the transmission coefficient of the thin slab placed in a waveguide has been developed. Slab position offset from the measurement reference plane has no effect on the measurement accuracy. An explicit expression for the dielectric constant is obtained in terms of the transmission coefficient by simplifying the exact solution for transmission through a thin dielectric slab. The method is verified with measurement on Teflon of 0.5-mm thickness. The measured dielectric constant of Teflon shows excellent agreement of both e � and e �� with published data. Subsequently, the dielectric constant of a vegetation
TL;DR: In this article, a Hilbert curve ring (HCR) fractaldefected ground structure (DGS) and its equivalent circuit are investigated and an improved HCR DGS cell model with open stubs loaded on the conductor line is presented to improve the out-band suppression.
Abstract: LOWPASSFILTERDESIGNOFHILBERTCURVERINGDEFECTEDGROUNDSTRUCTUREJ.Chen,Z.-B.Weng,Y.-C.Jiao,andF.-S.ZhangNational Key Laboratory of Antennas and Microwave TechnologyXidian UniversityXi’an 710071,ChinaAbstract—In this paper,a novel Hilbert curve ring (HCR) fractaldefected ground structure (DGS) and its equivalent circuit areinvestigated. Furthermore,an improved HCR DGS cell model withopen stubs loaded on the conductor line is then presented to improvethe out-band suppression. By employing three cascaded improvedHCR DGS cells,an L-band microstrip low-pass is designed andfabricated. This lowpass filter achieves a quite steep rejection property;a low in-band insertion loss of below 0.5dB and a high out-bandsuppression of more than 33dB.1. INTRODUCTIONRecently,there has been an increasing interest in the applicationsof defected ground structure (DGS) in microwave and millimeter-wave applications [1–3]. The DGS of the microstrip line employsan intentional defect on the ground and it provides band rejectioncharacteristic from the resonance property. The applications of theDGS are developed in divider,filter,and amplifier circuits. Thedefect of the conventional DGS is with the dumbbell shape or therectangle shape,these conventional DGSs,however,have a flat slopeof their rejection characteristic. To fabricate a lowpass filter with steeprejection property,many these DGSs are needed to be cascaded,whichalso means higher in-band insertion and larger size.Different from Euclidean geometries,fractal geometries have twocommon properties,space-filling and self-similarity. It has been shownthat the self-similarity property of fractal shapes can be successfullyapplied to the design of multi-band fractal antennas,such as theSierpinski gasket antenna [4],while the space-filling property of fractalscan be utilized to reduce antenna size [5,6].
TL;DR: In this paper, a new technique to evaluate the dielectric constant and loss factor of a homogeneous material using rectangular shaped perturb cavity has been developed, where the values of S-parameters are measured experimentally by placing the sample in the center of the cavity resonator.
Abstract: A new technique to evaluate the dielectric constant and loss factor of a homogeneous dielectric material using rectangular shaped perturb cavity has been developed. The values of S-parameters are measured experimentally by placing the sample in the center of the cavity resonator. Sample under test is fabricated in the form of a cylinder. The real and imaginary part of the permittivity can be then calculated from the shift in the resonance frequency and Q-factor. The results of a Teflon sample are also tabulated.
TL;DR: A comparison study between phase-only and amplitude-phase synthesis of symmetrical dual-pattern linear antenna arrays using floating-point or real-valued genetic algorithms (GA).
Abstract: In this paper, we present a comparison study between phase-only and amplitude-phase synthesis of symmetrical dual-pattern linear antenna arrays using floating-point or real-valued genetic algorithms (GA). Examples include a sum pattern and a sector beam pattern. In the former, phase is only optimized with predetermined Gaussian amplitude distribution of fixed dynamic range ratio (|amax/amin|) and in the latter, both are optimized with less dynamic range ratio than the former and yet share a common amplitude distribution.
TL;DR: In this article, a cross-coupled dual-band filter with four equal-length split-ring resonators is designed, and several finite out-of-band attenuation poles are realized to improve the selectivity of the proposed filter.
Abstract: A compact dual-band bandpass filter using equal-length split-ring resonators (SRRs) is proposed in this paper. The two- resonance frequency response of equal-length split-ring resonator is described in detail. A cross-coupled dual-band filter with four equal- length split-ring resonators is designed. Several finite out-of-band attenuation poles are realized to improve the selectivity of the proposed filter. The measurement of the filter is in good agreement with the simulation.
TL;DR: In this article, a dual-band coplanar waveguide (CPW)-fed planar monopole antenna suitable for WLAN application is presented, and the antenna resembling as a "G" shape and optimally designed by using the particle swarm optimization (PSO) algorithm can produce dual resonant modes and a much wider impedance bandwidth for the higher band.
Abstract: A dualband coplanar waveguide (CPW)-fed planar monopole antenna suitable for WLAN application is presented in this paper. The antenna resembling as a "G" shape and optimally designed by using the particle swarm optimization (PSO) algorithm can produce dual resonant modes and a much wider impedance bandwidth for the higher band. Prototypes of the obtained optimized antenna have been constructed and tested. The measured results explore good dualband operation with −10 dB impedance bandwidths of 9.7% and 62.8% at bands of 2.43 and 4.3 GHz, respectively, which cover the 2.4/5.2/5.8 GHz WLAN operating bands, and show good agreement with the numerical prediction. Also, good antenna performances such as radiation patterns and antenna gains over the operating bands have been observed.
TL;DR: In this paper, dispersion behavior of two specific Vivaldi antennas has been fully investigated in both frequency and time domains and results are verified by experimental data.
Abstract: Besides the return loss and radiation pattern, dispersion characteristic of the antenna is one of the most important factors which should be considered in ultra wideband applications. In this paper, dispersion behavior of two specific Vivaldi antennas has been fully investigated in both frequency and time domains. All simulations are carried out by CST MS software. Moreover, by fabricating the antennas, the simulation results are verified by experimental data.
TL;DR: In this paper, the authors describe stimulated Brillouin scattering and stimulated Raman scattering processes in optical fiber and their thresholds, reduction in power penalty and applications along with comparative study of these effects are also presented.
Abstract: The nonlinear scattering effects in optical fiber occur due to inelastic-scattering of a photon to a lower energy photon. This paper describes stimulated Brillouin scattering and stimulated Raman scattering processes. Their thresholds, reduction in power penalty and applications along with comparative study of these effects are also presented.
TL;DR: In this article, the authors proposed a compact antenna with good impedance matching for ultrawide-band (UWB) impulse radio technology in the frequency band 3.1-10.6 GHz for commercial use.
Abstract: With the definition and acceptance of the ultrawide-band (UWB) impulse radio technology in the USA [1], there has been considerable research effort put into UWB radio technology worldwide. Recently, the Federal Communication Commission (FCC)’s allocation of the frequency band 3.1–10.6 GHz for commercial use has sparked attention on ultra-wideband (UWB) antenna technology in the industry and academia. Several antenna configurations have been studied for UWB applications [2–6]. It is of a particular interest to design a compact antenna with good impedance matching
TL;DR: In this article, the authors measured the rain attenuation in the 12 GHz band and one-minute rain rate at four satellite beacons located in South East Asia countries over a three-year period (2002-2004).
Abstract: The rain attenuation in the 12-GHz band and one-minute- rain rate were measured at four satellite beacons located in South East Asia countries over a three-year period (2002-2004). The cumulative distribution of rain rate obtained as well as cumulative distribution of rain attenuation obtained are presented and compared with the rain prediction models. Most of the rain prediction models showed noticeable deviation to the measured values above the existence of the breakpoint (the point at which the slope changes). The results can be employed to guide the design and application of slant-path communication systems, especially in South East Asia countries.
TL;DR: In this paper, the effect of group velocity dispersion (GVD) imposes severe limit on information carrying capacity of optical communication systems and the application of solitons in communication systems opens the way to ultrahigh-speed information superhighways.
Abstract: The group velocity dispersion (GVD) imposes severe limit on information carrying capacity of optical communication systems. By choosing appropriate pulse shape highly stable light pulses known as solitons are generated when effect of GVD is balanced by self-phase modulation (SPM). The application of solitons in communication systems opens the way to ultrahigh-speed information superhighways. Transmission speed of order of Tbit/s can be achieved if optical amplifiers are combined with WDM in soliton based communication systems.
TL;DR: In this paper, the performance of a dual-band PIFA and a dual band helical antenna designed for operating in GSM900 and DCS1800 frequency bands is investigated in free space as well as in the presence of head and hand.
Abstract: Helical antenna and planar inverted-F antenna (PIFA) are two commonly used handset antennas. This paper presents a comprehensive study on the performance of a dual band PIFA and a dual band helical antenna designed for operating in GSM900 and DCS1800 frequency bands. Radiation patterns and VSWR of these antennas are computed in free space as well as in the presence of head and hand. The specific absorption rate (SAR) of the helical antenna is calculated and compared with that of the PIFA handset antenna. The peak average SAR in the head is compared with SAR limits in the safety standards and so the maximum radiation power of each antenna is determined. In addition, radiation efficiencies of these handset antennas are computed in the presence of head and hand. All numerical simulations are performed using the Ansoft HFSS software. Numerical simulations results are in good agreement with published measurement results.
TL;DR: In this article, the scattering of electromagnetic plane wave by a perfectly conducting disk is formulated rigorously in a form of the dual integral equations (abbreviated as DIE), where the unknowns are the induced surface current and the tangential components of the electric field on the disk.
Abstract: The scattering of electromagnetic plane wave by a perfectly conducting disk is formulated rigorously in a form of the dual integral equations (abbreviated as DIE). The unknowns are the induced surface current (or magnetic field) and the tangential components of the electric field on the disk. The solution for the surface current is expanded in terms of a set of functions which satisfy Maxwell's equation for the magnetic field on the disk and the required edge condition. At this step we have used the method of the Kobayashi potential and the vector Hankel transform. Applying the projection solves the rest of a pair of equations. Thus the problem reduces to the matrix equations for the expansion coefficients. The matrix elements are given in terms of the infinite integrals with a single variable and these may be transformed into infinite series that are convenient for numerical computation. The numerical results are obtained for far field patterns, current densities induced on the disk, transmission coefficient through the circular aperture, and radar cross section. The results are compared with those obtained by other methods when they are available, and agreement among them is fairly well.
TL;DR: In this article, a square patch perturbs the symmetry and splits the two degenerate modes to create dual-band operation, and the frequency ratio in the range of 1.04 to 1.4 can be achieved by the proper selection of the square patch size.
Abstract: A novel compact dual-band reconfigurable square-ring microstrip antenna is presented. The tuning is achieved using a single varactor diode connected to a small square patch attached to an inner corner of the square-ring. The square patch perturbs the symmetry and splits the two degenerate modes to create dual-band operation. The frequency ratio in the range of 1.04 to 1.4 can be achieved by the proper selection of the square patch size. The lower resonance frequency can be further decreased by loading the square patch at its corner by a reverse biased varactor diode. The diode has almost no effect on the upper resonance frequency. This technique is used to implement an electronically tunable dual-band antenna on FR4 material with er =4 .5 and 1.5 mm thickness. The size of the ring,the square patch,and the varactor used,are selected to yield a fixed upper resonance frequency at about 1.93 GHz. The resulting lower resonance frequency is tuned from 1.37 to 1.7 GHz in the voltage range from 0 to 30 V,respectively. The measurements agree well with simulation results.
TL;DR: In this article, the propagation of ultra-wideband (UWB) pulse based on time reversal (TR) technique is studied by finite-different time-domain method in indoor environment.
Abstract: In this paper, the propagation of ultra-wideband (UWB) pulse based on time reversal (TR) technique is studied by finite- different time-domain method in indoor environment. Time compression and spatial focusing of TR waveform are simulated and the propagation of multi-waveform string is analyzed. Then UWB wireless signal transmission based on TR concept is studied numerically. The studied results indicate that the UWB communication based on TR technique can obtain better Inter-Symbol Interference (ISI) and Co- Channel Interference (CCI) performance than traditional one because of its unique property.