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2009-09-30
PIER
Vol. 96, 377-395, 2009
download: 378
Analysis and Design of New Active Quasi Circulator and Circulators
Reza Bahri Abdolali Abdipour Gholamreza Moradi
This paper introduces two new type active quasi circulators and three new type active circulators which use the out-of-phase power divider/combiner, symmetric/anti-symmetric couplers and generic unilateral amplifiers. The proposed circuits are full-symmetric and composed of conventional microwave devices. Analytical relations for active quasi circulator modules are described. These modules have many variations and can be used for very wide frequency range depending on the type of the employed unilateral amplifier, power divider/combiner and symmetric/anti-symmetric couplers. Based on the proposed configurations, analysis and design of n-port active circulators are presented. Also they can be used in MMICs as active quasi circulators, active circulators and in other high frequency applications.
ANALYSIS AND DESIGN OF NEW ACTIVE QUASI CIRCULATOR AND CIRCULATORS
2009-09-30
PIER
Vol. 96, 361-376, 2009
download: 92
On the Use of Dimension and Lacunarity for Comparing the Resonant Behavior of Convoluted Wire Antennas
Massimiliano Comisso
This paper analyzes the possibility to use dimension and lacunarity for comparing the resonant behavior of different convoluted wire antennas, including prefractal dipoles. Since previous studies have proved that the Hausdorff fractal dimension is not suitable for antenna comparison purposes, this work proposes the adoption of a different approach for evaluating the dimension by using the measurement at scale δ, which is more suitable for analyzing real phenomena. The results provided by this measure are compared to those obtained by using the average lacunarity. The objective is to verify if, given two convoluted wire dipoles, the dimension and average lacunarity provide sufficient information to infer which dipole exhibits the lower resonances.
ON THE USE OF DIMENSION AND LACUNARITY FOR COMPARING THE RESONANT BEHAVIOR OF CONVOLUTED WIRE ANTENNAS
2009-09-28
PIER
Vol. 96, 347-359, 2009
download: 109
Simplified Design Flow of Quasi-Optical Slot Amplifiers
Ivan Russo Luigi Boccia Giandomenico Amendola Giuseppe Di Massa
Quasi-optical (QO) techniques have been extensively studied in recent years because of the promise they hold for medium and high power generation at millimeter- and sub-millimeter-wave frequencies, demonstrating higher efficiency than conventional approaches. In this work a step-by-step flow process is proposed for the design of a slot-based QO amplifier. The proposed design procedure is based on full-wave analysis of the individual building blocks, which are then cascaded to represent the whole system. An experimental assessment is proposed based on the design and on experimental analysis of the behavior of a C-band QO unit cell.
SIMPLIFIED DESIGN FLOW OF QUASI-OPTICAL SLOT AMPLIFIERS
2009-09-26
PIER
Vol. 96, 329-346, 2009
download: 114
Narrowband Filter in a Heterostructured Multilayer Containing Ultrathin Metallic Films
Chi-Chung Liu Yang-Hua Chang Tzong-Jer Yang Chien-Jang Wu
A narrowband reflection and/or transmission filter made of heterostructured multilayer with two different ultrathin metallic films is proposed. The multilayer structure is a cascaded system that is formed by using two narrowband reflection-and-transmission filters. Each individual filter is made of an ultrathin metal film in front of a planar Fabry-Perot resonator. Using the transfer matrix method in a stratified system, the optical filtering properties are theoretically investigated and analyzed. It is found that the reflection peak at the design wavelength in the original individual filter becomes a dip in the heterostructured filter. The role played by the stack number of Bragg reflector in the design of narrowband filter is also clearly elucidated.
NARROWBAND FILTER IN A HETEROSTRUCTURED MULTILAYER CONTAINING ULTRATHIN METALLIC FILMS
2009-09-26
PIER
Vol. 96, 309-328, 2009
download: 116
Characterization of the Validity Region of the Extended T-Matrix Method for Scattering from Dielectric Cylinders with Finite Length
Wen-Zhe Yan Yang Du Zengyuan Li Er-Xue Chen Jian-Cheng Shi
The T-matrix approach is effective in analyzing electromagnetic scattering from finite scatterers. Yet for scatterers with extreme geometry, this approach may fail. One example is its inability to analyze scattering from dielectric cylinders with large aspect ratios. To deal with such difficulty, recently we proposed a method based on an extension of the T-matrix approach, where a long cylinder is hypothetically divided into a cluster of identical sub-cylinders, for each the T matrix can be numerically stably calculated. Special care was paid to fulfill the boundary conditions at the hypothetic surface of any two neighboring sub-cylinders. The resultant coupled equations are different from that of multi-scatterer theory. The model results were in good agreement with experiment data available in the literature. However, the validity region of the proposed method was not fully characterized. Now we have developed and validated a method of moment (MoM) code, and are in a position to carry on the task of characterizing the validity region. The proposed method is found to be applicable to dielectric cylinders of arbitrary length as long as the T matrix is attainable for the elementary sub-cylinder. The conditions for the T matrix to be numerically stably calculated in terms of the equivalent volumetric radius and relative dielectric constant are also empirically obtained.
CHARACTERIZATION OF THE VALIDITY REGION OF THE EXTENDED T-MATRIX METHOD FOR SCATTERING FROM DIELECTRIC CYLINDERS WITH FINITE LENGTH
2009-09-25
PIER
Vol. 96, 299-308, 2009
download: 143
A Novel Ultra-Wide Band Antenna with Reduced Radar Cross Section
Tao Hong Shu-Xi Gong Wen Jiang Yun-Xue Xu Xing Wang
A novel printed dual circular ring monopole antenna with low radar cross section (RCS) for ultra-wide band (UWB) application is proposed. The proposed antenna is designed to realize RCS reduction. The two circular rings are connected by several metallic via holes to improve the radiation characteristics of the proposed antenna. Its UWB-related characteristics are simulated and experimentally verified. The RCS performance of the proposed antenna under different loads is studied and compared with that of a commonly used circular-disc monopole antenna. The results show that the proposed antenna has good radiation performances and lower RCS than the reference antenna. The proposed antenna serves as a good candidate in the design of UWB antenna with the requirement of RCS control.
A NOVEL ULTRA-WIDE BAND ANTENNA WITH REDUCED RADAR CROSS SECTION
2009-09-23
PIER
Vol. 96, 287-298, 2009
download: 262
Design of Narrow Band-Pass Frequency Selective Surfaces for Millimeter Wave Applications
Jian-Cheng Zhang Ying-Zeng Yin Jin-Ping Ma
A design methodology of narrow band-pass frequency selective surfaces (FSSs) using the Fabry-Perot approach is presented. The whole FSS structure consists of two identical single layer FSSs separated by a foam layer, which forms a Fabry-Perot interferometer (FPI). The band-pass characteristic is a result of the FPI. The pass band can be controlled by the thickness of the foam, and the bandwidth can be controlled by the reflection coefficients of the single layer FSSs. The effects of both metallic and dielectric losses are discussed. It is interesting to note that the transmission peaks of FPI with high Q factor decline rapidly and finally disappear as the losses increase, and the insertion loss is mainly due to the refection. The relationship between the insertion loss and the Q factor of the FPI is examined. As examples, narrow band-pass FSSs at about 96 GHz with different bandwidths are designed.
DESIGN OF NARROW BAND-PASS FREQUENCY SELECTIVE SURFACES FOR MILLIMETER WAVE APPLICATIONS
2009-09-21
PIER
Vol. 96, 267-285, 2009
download: 105
Multi-Resolution Retrieval of Non-Measurable Equivalent Currents in Microwave Imaging Problems-Experimental Assessment
Paolo Rocca
In this paper, an approach based on a multi-scaling strategy for the reconstruction of the non-measurable components of equivalent current distributions is tested against experimental data. An extensive set of simulations is carried out considering single and multiple scatterers with homogeneous as well as inhomogeneous properties. Selected results are reported and discussed to show potentialities and limitations of the method.
MULTI-RESOLUTION RETRIEVAL OF NON-MEASURABLE EQUIVALENT CURRENTS IN MICROWAVE IMAGING PROBLEMS-EXPERIMENTAL ASSESSMENT
2009-09-18
PIER
Vol. 96, 251-266, 2009
download: 103
Fast Capacitance Extraction for Finite Planar Periodic Structures Using the Generalized Forward-Backward and Novel Spectral Acceleration Method
Chatrpol Lertsirimit Danai Torrungrueng
The generalized forward-backward and novel spectral acceleration (GFB/NSA) method is applied to capacitance extraction problems of finite planar periodic structures. In the GFB method, the interaction within a unit cell can be calculated and stored beforehand. The interactions between relatively far-separated unit cells are however calculated by the GFB/NSA method to further accelerate the calculation speed. The contributions to a receiving element on finite planar periodic structures are separated into weak and strong source contributions by an appropriate separation index, which is conveniently specified by an amount of unit cells rather than a distance. The strong source contribution is performed by the standard matrix-vector multiplication in the GFB method, while the weak source contribution is computed using the NSA algorithm. Numerical examples show comparisons of the GFB/NSA method with a commercial software, including the efficiency of the method. With the array increment in one direction, the GFB/NSA method shows O(N) in the calculation time per iteration, while its memory requirement for a very large problem also tends to be O(N), where N is the number of unknowns.
FAST CAPACITANCE EXTRACTION FOR FINITE PLANAR PERIODIC STRUCTURES USING THE GENERALIZED FORWARD-BACKWARD AND NOVEL SPECTRAL ACCELERATION METHOD
2009-09-16
PIER
Vol. 96, 237-249, 2009
download: 235
Bright and Dark Soliton Generation in a Left-Handed Nonlinear Transmission Line with Series Nonlinear Capacitors
Fatemeh Gharakhili Mahmoud Shahabadi Mohammad Hakkak
In this article, we demonstrate that in the case of a positive group velocity left-handed nonlinear (LH-NL) transmission line with series nonlinear capacitances, the spatial derivative of the voltage distribution satisfies the nonlinear Schrödinger (NLS) equation. Consequently, it will shown that a LH-NL transmission line with series varactors can be used to generate both bright and dark solitons similar to a composite right-left-handed (CRLH) transmission line periodically loaded with shunt varactors. The paper also discusses the conditions for generation of bright and dark solitons.
BRIGHT AND DARK SOLITON GENERATION IN A LEFT-HANDED NONLINEAR TRANSMISSION LINE WITH SERIES NONLINEAR CAPACITORS
2009-09-16
PIER
Vol. 96, 217-236, 2009
download: 760
Reduction of Leakage Magnetic Field in Electromagnetic Systems Based on Active Shielding Concept Verified by Eigenvalue Analysis
Faramarz Faghihi Hossein Heydari
Leakage fields are one of the main issues in design of electromagnetic systems. Some of these fields close their paths through the core and air, giving rise to non-ideal behavior of the magnetic systems. This paper explains a novel concept of active shielding which consists of two compensation coils in series and generates a counter field opposite to the leakage fields leaking from an iron-core system. As the method is based on physical reasoning of electromagnetic coupled circuit theory, the design criterions for the compensating coils parameters, their number of turns and their adaptation to the systems, were considered. The state of the art is presented by a model which is verified by roots of system characteristic equations, using state equations. In a case study, this method was investigated in a 25kA (125kVA) current injection transformer (CIT) system delivering a secondary current as closely proportioned to the primary current as possible, using finite element method (FEM) simulation. This paper will also push the state of the art by reducing the age effect of the CIT through mechanical force reduction.
REDUCTION OF LEAKAGE MAGNETIC FIELD IN ELECTROMAGNETIC SYSTEMS BASED ON ACTIVE SHIELDING CONCEPT VERIFIED BY EIGENVALUE ANALYSIS
2009-09-15
PIER
Vol. 96, 205-215, 2009
download: 171
A Non-Spurious Vector Spectral Element Method for Maxwell's Equations
Jiefu Chen Qing Huo Liu
In this paper, a non-spurious vector spectral element method is proposed to solve Maxwell's equations using E and H as variables. The mixed-order curl-conforming basis functions are used for both variables to facilitate applying boundary and interface conditions; and the interpolation degree of basis functions for E is set different from that for H to suppress the spurious modes. The proposed method can be utilized in both time domain and frequency domain, and it is very suitable for the future implementation of discontinuous Galerkin spectral element method. Numerical results demonstrate the property of spurious-free and the spectral accuracy of this method. The method has also been implemented for the more general finite element method in time and frequency domains.
A NON-SPURIOUS VECTOR SPECTRAL ELEMENT METHOD FOR MAXWELL'S EQUATIONS
2009-09-11
PIER
Vol. 96, 193-204, 2009
download: 111
High Resolution Range Profile Identifying Simulation of Laser Radar Based on Pulse Beam Scattering Characteristics of Targets
Ming-Jun Wang Zhen-Sen Wu Ying-Le Li Geng Zhang
This is a presentation of an innovative technique of rigid body estimation for use with laser high-range resolution profile (LHRRP) simulations. The theory of pulse beam scattering from random rough surface is used to build a theoretical model which computes simulations for the laser pulse HRRP of the whole dimension target. As two especial cases, the LHRRP of sphere and cone are simulated in detail. We discuss and analyze some influential factors on laser radar HRRP imaging such as their dimensions, correlation length and height root mean square of the rough surface, refractive index of the material and width pulse. The simulated results suggest that the reliable identifications are possible provided in some aero and aerial recognized applications with higher resolution by laser radar.
HIGH RESOLUTION RANGE PROFILE IDENTIFYING SIMULATION OF LASER RADAR BASED ON PULSE BEAM SCATTERING CHARACTERISTICS OF TARGETS
2009-09-10
PIER
Vol. 96, 173-191, 2009
download: 117
A Fully-Adaptive Smart Antenna Prototype: Ideal Model and Experimental Validation in Complex Interference Scenarios
Manuel Benedetti Giacomo Oliveri Paolo Rocca Andrea Massa
In this paper, the architecture of a smart antenna prototype is described and its functionality assessed. The system prototype is composed by an 8-elements linear array of dipoles with a finite reflecting plane and the adaptive behavior is obtained modifying a set of array weights with electronically-driven vector modulators. In order to real-time react to complex interference scenarios, the system is controlled by a software control module based on a Particle Swarm Optimizer. To demonstrate the feasibility and the effectiveness of the proposed implementation, a set of representative results concerned with different interference scenarios is reported and discussed.
A FULLY-ADAPTIVE SMART ANTENNA PROTOTYPE: IDEAL MODEL AND EXPERIMENTAL VALIDATION IN COMPLEX INTERFERENCE SCENARIOS
2009-09-09
PIER
Vol. 96, 155-172, 2009
download: 129
A Unified FDTD Approach for Electromagnetic Analysis of Dispersive Objects
Yu-Qiang Zhang De-Biao Ge
In order to obtain a unified approach for the Finite-Difference Time-Domain (FDTD) analysis of dispersive media described by a variety of models, the coordinate stretched Maxwell's curl equation in time domain is firstly deduced. Then the FDTD update formulas combined with the semi-analytical recursive convolution (SARC) in Digital Signal Process (DSP) technique for general dispersive media are obtained. In this method, the flexibility of FDTD in dealing with complicated object is retained; the advantages of absolute stability, high accuracy, less storage and high effectiveness of SARC in treating the linear system problem are introduced, and a more unified update formulation for a variety of dispersion media model including Convolution Perfectly Matched Layers (CPML) absorbing boundary is possessed. Therefore it can be applied to analysis of general dispersive media provided that the poles and corresponding residues in dispersive medium model of interest are given. Finally, three typical kinds of dispersive model, i.e. Debye, Drude and Lorentz medium are tested to demonstrate the feasibility of presented approach.
A UNIFIED FDTD APPROACH FOR ELECTROMAGNETIC ANALYSIS OF DISPERSIVE OBJECTS
2009-09-09
PIER
Vol. 96, 141-154, 2009
download: 100
Study of a Novel Wideband Circular Slot Antenna Having Frequency Band-Notched Function
Guo-Ping Gao Ming Li Shu-Fei Niu Xiao-Jun Li Bo-Nian Li Jin-Sheng Zhang
In this paper, the design, simulation, and fabrication of a novel printed circular slot antenna with a band-notched function suitable for UWB application is presented and investigated. The band-notched characteristic is achieved and adjusted by inserting L-shaped branches into the ground plane. Experimental results show that the proposed antenna meets the requirement of wide working bandwidth of 3.1-10.6 GHz with return loss < -10 dB, while avoiding the interference with the 5-GHz WLAN band. The study of transfer function (amplitude of S21/group delay) and time domain characteristic (fidelity/power spectrum density (PSD)) indicate a band-notched function of the antenna. The proposed antenna has a compact size, good radiation characteristics, ultra wide band-width, and good time-domain behaviors to satisfy the requirement of the current wireless communication systems.
STUDY OF A NOVEL WIDEBAND CIRCULAR SLOT ANTENNA HAVING FREQUENCY BAND-NOTCHED FUNCTION
2009-09-09
PIER
Vol. 96, 127-139, 2009
download: 182
Enhance Gain and Bandwidth of Circularly Polarized Microstrip Patch Antenna Using Gap-Coupled Method
The-Nan Chang Jing-Hae Jiang
In this paper, one 3×3 and one 5×5 antenna arrays are studied. In each array, one probe-fed circularly polarized (CP) microstrip patch antenna is placed at the center as the driven antenna and is gapped coupled to the remaining elements. It is investigated that CP performance of the patch can be proved by properly arranging these parasitic elements. The driven patch is a perturbed square one with two diagonal corners truncated. The remaining elements are square patches slightly smaller than the driven patch. The proposed antennas have been constructed and measured. The 3×3 array has a measured gain of 7.7 dBic with a 3 dB axial ratio bandwidth of 3.3%. The 5×5 array has a measured gain of 9.3 dBic with a 3dB axial ratio bandwidth of 8.1%.
ENHANCE GAIN AND BANDWIDTH OF CIRCULARLY POLARIZED MICROSTRIP PATCH ANTENNA USING GAP-COUPLED METHOD
2009-09-09
PIER
Vol. 96, 117-125, 2009
download: 134
Design of Triple-Mode Bandpass Filter Using Improved Hexagonal Loop Resonator
Shao-Guo Mo Zhi-Yuan Yu Long Zhang
A novel triple-mode hexagonal bandpass filter with capacitive loading stubs is introduced in this article. The technique, adding an open capacitive stub, is applied to enlarge the equivalent self-capacitance of the resonator, which declines its resonant frequencies. Three radial-line stubs in the center of top layer are used to implement this technique. One mode resonant frequency is varied with the radii of three radial-line stubs, while the other two modes are nearly not affected. This filter has a pair of transmission zeros which are close to the passband, thus it behaves with high selectivity. For method validation, a bandpass filter operating at 2.4 GHz is fabricated and measured. The experimental results are demonstrated and discussed.
DESIGN OF TRIPLE-MODE BANDPASS FILTER USING IMPROVED HEXAGONAL LOOP RESONATOR
2009-09-08
PIER
Vol. 96, 101-116, 2009
download: 115
Fractional Rectangular Impedance Waveguide
Akhtar Hussain Qaisar Naqvi
Fractional rectangular impedance waveguide has been studied using fractional curl operator. Behavior of field inside the fractional rectangular impedance waveguide has been studied with respect to the original impedance of walls of the guide as well as fractional parameter. Analysis of the impedance of the walls as well as power distribution over the cross sectional plane of fractional impedance rectangular waveguide has been given. It has been found that fractional curl can be used to control the power distribution pattern over the cross sectional plane.
FRACTIONAL RECTANGULAR IMPEDANCE WAVEGUIDE
2009-09-07
PIER
Vol. 96, 83-100, 2009
download: 108
Analysis of Electromagnetic Scattering with Higher-Order Moment Method and NURBS Model
Zi-Liang Liu Juan Yang
A novel scheme of combining non-uniform rational B-splines (NURBS) model with higher-order moment method (HOMM) is presented. The mesh precision of conforming to practical object is a major factor for HOMM to yield accurate results. In the present paper, NURBS technique is employed to model complex objects accurately with large curved Bezier patches and no factitious geometric discontinuities are introduced between the adjoining patches. The higher-order modified Legendre basis functions are defined on Bezier patch. As a result of the combination of NURBS model with HOMM, the accuracy of results is greatly improved compared with HOMM on curved parametric quadrilateral (CPQ) model, meanwhile, the number of unknowns is much reduced. Numerical results show that NURBS-HOMM is an efficient technique with good potential to solve the electromagnetic (EM) problems of complex electrically large objects.
ANALYSIS OF ELECTROMAGNETIC SCATTERING WITH HIGHER-ORDER MOMENT METHOD AND NURBS MODEL