Vol. 127
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2012-05-10
PIER
Vol. 127, 553-569, 2012
A Modified Taguchi's Optimization Algorithm for Beamforming Applications
Zaharias D. Zaharis
The present paper is a study of adaptive beamforming (ABF) techniques applied to antenna arrays. The structure of these techniques is based on Taguchi's Optimization (TagO) method. The high convergence speed and the ability to reach near-optimal solutions by adjusting only one parameter make the Taguchi's method an attractive choice for real time implementations like the case of ABF. Modifications are proposed in order to enhance the applicability of the TagO algorithm and decrease the computational time needed by the algorithm to terminate. The TagO method is used here to construct an ABF technique that aims at steering the main lobe of a uniform linear array towards a signal of interest, under the constraint of low side lobe level (SLL) or the constraint of placing radiation pattern nulls towards respective interference signals. Properly defined fitness functions must be minimized by the TagO algorithm to satisfy respectively the above mentioned constraints. The TagO-based ABF technique is compared with typical beamforming methods, like the Sample Matrix Inversion (SMI) and Maximum Likelihood (ML) ones, and with two evolutionary ABF techniques based on Particle Swarm Optimization (PSO) and Differential Evolution (DE), respectively. The comparison is performed regarding the convergence speed, the ability to achieve better fitness values in less time, the ability to properly steer the main lobe and finally the null-steering ability or the SLL control depending on the constraint type. The results exhibit the superiority of the TagO-based technique.
2012-05-09
PIER
Vol. 127, 537-552, 2012
A Novel Dual-Loop Coupler for One-Port Cylindrical Cavity Permittivity Measurement
Hai Zhang Bao-Qing Zeng Lei Ao Zhaotang Zhang
The one-port cavity resonator method based on the S11 parameter measurement technique for measuring the complex permittivity of dielectric samples has been proposed. A novel dual-loop coupler is developed for avoiding and suppressing the spurious modes in one-port cavity resonator. Through threading the pair of half loop in the opposite direction, the opposite surface currents can be generated and only TE011 mode will be excited. The operating principles of the dual-loop coupler are investigated. This technique has the advantages of the coupling. Equivalent electronic circuit model has been set up. Simulation and experimental results show good agreement.
2012-05-07
PIER
Vol. 127, 523-536, 2012
Design and Analysis of Planar Ultra-Wideband Antenna with Dual Band-Notched Function
Fuguo Zhu Steven Gao Anthony Tung Shuen Ho Chan Hwang See Raed A. Abd-Alhameed Jianzhou Li Jia-Dong Xu
A novel planar ultra-wideband (UWB) antenna with dual band-notched characteristics is proposed. The antenna is fabricated on a printed circuit board (PCB), having a circular monopole and arc-shaped parasitic strips on one side and a ground plane with a slot aperture on the other side. Two narrow bands at 5.15-5.35 GHz and 5.725-5.825 GHz are notched by using two arc-shaped parasitic strips on the same layer of the radiator. Compared with other band-notched UWB antennas, the proposed antenna exhibits the advantages of simple structure, compact size, simple control of each notched frequency band using separate parasitic strips, and good performance. Surface current distributions and equivalent circuit model are applied to analyze the operating principle of the proposed antenna. To validate the concept, a prototype is fabricated and tested. Both simulated and measured results confirm that the proposed antenna achieves a wide bandwidth from 3.1 GHz to 10.6 GHz with two narrow bands notched successfully. The results of VSWR, radiation patterns and gain response are shown and discussed in detail. The antenna enables the independent control of the notched frequency bands, and the proposed method can be extended for designing planar UWB antennas with multiple band-notched characteristics and reconfigurable notched frequency.
2012-05-07
PIER
Vol. 127, 501-522, 2012
Scattering of Electromagnetic Plane Wave by a Circular Disk with Surface Impedance
Allah Ditta Ulfat Jafri Qaisar Naqvi Kohei Hongo
In this investigation, scattering from a circular disk with surface impedance has been studied rigorously. The method of analysis is Kobayashi Potential (KP). The mathematical formulation yields the dual integral equations (DIEs). These DIEs are solved by using the discontinuous properties of Weber-Schafheitlin's integral. After applying the boundary conditions and projection, the resulting expressions, finally, reduce to matrix equations for expansion coefficients. The matrix elements are in the form of infinite integrals with single variable. These are then used to compute the values of expansion coefficients. The far field patterns of the scattered wave are computed for different incident angles and surface impedances for both E- and H-polarizations. To verify the results, we have computed the solution based on the physical optics approximation. The agreement between them is fairly good.
2012-05-07
PIER
Vol. 127, 479-499, 2012
Non Linear Optimization Technique for the Reduction of the Frequency Scanning Effect in a Phased Array Based on Broadband Injection-Locked Third Harmonic Self-Oscillating Mixers
Miguel Fernandez-Garcia Samuel Ver-Hoeye Carlos Vazquez-Antuna George Roberto Hotopan Rene Camblor-Diaz Fernando Las Heras Andres
In this work, an electronically tunable large range phase shifter based on a broadband Injection-Locked Third Harmonic Self-Oscillating Mixer (IL3HSOM) is designed and analyzed. This multifunctional circuit generates a down-converted Intermediate Frequency (IF) signal and provides a theoretical 540◦ continuous phase shift range. The conversion gain and the bandwidth of the circuit are optimized through bifurcation control techniques. The IL3HSOM will be used as the core of a broadband phased antenna array with electronic beam-steering capabilities. The use of a multi-harmonic load based on an arbitrarily width modulated transmission line allows the nonlinear optimization of the circuit phase shift frequency response to ompensate the frequency scanning effect, which negatively influences the performance of broadband antenna arrays.
2012-05-03
PIER
Vol. 127, 461-478, 2012
Principle Component Analysis and Fuzzy Logic Based through Wall Image Enhancement
Principle component analysis based through wall image enhancement is proposed which is capable of discriminating target, noise and clutter signals. The overlapping boundaries of clutter, noise and target signals are separated using fuzzy logic. Fuzzy inference engine is used to assign weights to principle components. The proposed scheme works well significantly for extracting multiple targets having different range profiles in heavy cluttered through wall images. Simulation results are compared on the basis of mean square error, peak signal to noise ratio and visual inspection.
2012-05-03
PIER
Vol. 127, 445-459, 2012
Complex Point Source for the 3D Laplace Operator
Maria-Jesus Gonzalez-Morales Raul Mahillo-Isla Carlos Dehesa-Martinez Emilio Gago-Ribas
The research about the so-called \emph{complex beams}, localized solutions of the Helmholtz wave equation, lead to the problem of finding the sources of such solutions, which may be formally expressed as a Dirac delta function of a complex argument. To investigate about the meaning of the Dirac delta distribution of complex argument, the Green's function of the 3D Poisson problem with a point source localized at an imaginary position in free space is considered. The main physical features of the potential created by that source are described. The inverse problem consists in looking for the real source distribution which causes that potential. The sources appear on a disk in the real space. Their physical interpretation requires a regularization process based on including the border of the disk.
2012-04-27
PIER
Vol. 127, 427-444, 2012
Utilization of Screen Printed Low Curing Temperature Cobalt Nanoparticle Ink for Miniaturization of Patch Antennas
Mikko Nelo Arun K. Sowpati Vamsi Krishna Palukuru Jari Juuti Heli Jantunen
This investigation is one of the first steps towards the realization of low-cost, mass producible, miniaturized antenna solutions utilizing screen printed magnetic thick films of cobalt nanoparticle ink. The ink has a curing temperature lower than 125°C, feasible printing characteristics and metal loading higher than 85 wt.%. The properties are achieved by using an oxidatively polymerising natural fatty acid, linoleic acid, both as a surfactant and a binder. DSC-TGA-MS-analysis, TEM and SEM microscopies were utilized to investigate ink composition, nanoparticle coating and print quality. The resonant frequency of a microstrip patch antenna was tuned by screen printing of cobalt nanoparticle ink with different layer thicknesses on top of the antenna element. The influence of magnetic layers on resonance frequency, return loss, total efficiency and radiation pattern was measured and compared with a reference antenna without the magnetic films. For example, five layers of magnetic film (52 μm total thickness) tuned the resonance frequency (2.49 GHz) of the patch antenna by 68 MHz. The radiation efficiency of the patch antenna was increased from 39% to 43% by the loading of a 52 μm thick magnetic film compared to the reference antenna. The radiation patterns remained essentially unchanged, despite the presence of the magnetic thick films.
2012-04-27
PIER
Vol. 127, 405-426, 2012
The Real-Valued Time-Domain TE-Modes in Lossy Waveguides
Oleg Tretyakov Mehmet Kaya
The time-domain studies of the modal fields in a lossy waveguide are executed. The waveguide has a perfectly conducting surface. Its cross section domain is bounded by a singly-connected contour of rather arbitrary but enough smooth form. Possible waveguide losses are modeled by a conductive medium which fills the waveguide volume. Standard formulation of the boundary-value problem for the system of Maxwell's equations with time derivative is given and rearranged to the transverse-longitudinal decompositions. Hilbert space of the real-valued functions of coordinates and time is chosen as a space of solutions. Complete set of the TE-time-domain modal waves is established and studied in detail. A continuity equation for the conserved energetic quantities for the time-domain modal waves propagating in the lossy waveguide is established. Instant velocity of transportation of the modal flux energy is found out as a function of time for any waveguide cross section. Fundamental solution to the problem is obtained in accordance with the causality principle. Exact explicit solutions are obtained and illustrated by graphical examples.
2012-04-27
PIER
Vol. 127, 389-404, 2012
The Reflection and Transmission of Electromagnetic Waves by a Uniaxial Chiral Slab
Jian-Feng Dong Jie Li
The reflection and transmission of electromagnetic waves obliquely incident on a uniaxial chiral slab with the optical axis perpendicular to the interface have been investigated. Firstly, the formulas of the reflection and transmission are derived. Then numerical results for four cases of the uniaxial chiral media are presented and different chiral parameters are considered. Finally, the Brewster's angles and total transmission are discussed.
2012-04-26
PIER
Vol. 127, 371-387, 2012
Synthesis of Thinned Linear and Planar Antenna Arrays Using Binary PSO Algorithm
Wei-Bo Wang Quanyuan Feng Dong Liu
Traditional optimization methods are not well suited for thinning large arrays to obtain a low sidelobe level (SLL). The chaotic binary particle swarm optimization (CBPSO) algorithm is presented as a useful alternative in the synthesis of thinned arrays. The proposed algorithm is improved by nonlinear inertia weight with chaotic mutation to increase the diversity of particles. Two examples have been proposed and solved. Simulation results compared with published results illustrate the effectiveness of the proposed method for both linear and planar arrays.
2012-04-26
PIER
Vol. 127, 351-370, 2012
The "Slope" Effect of Coherent Transponder in InSAR Dem
Qingfu Liu Shiqi Xing Xuesong Wang Jian Dong Dahai Dai Yongzhen Li
Although a Coherent Transponder (CT) is widely utilized in the field of Synthetic Aperture Radar (SAR), its Digital Elevation Model (DEM) has yet not been well studied for Interferometry SAR (InSAR). Based on the fact that the interferometry phase is a constant for CT with single transmit antenna, this paper mainly focuses on InSAR DEM induced by CT. The decorrelation effect in the intersection region of CT and nature terrain is researched in detail to support the analysis of CT's phase-unwrapping. The most important property, which makes DEM of CT being unique, is found to be the "slope" effect. The incline angel of "main slope" of DEM is verified to be determined only by the depression angle of InSAR system, whereas the incline angles of the "subordinate slopes" are affected by all the geometric parameters of InSAR baseline. Finally, all the incline angels are independent of CT' s waveform modulations, since the modulations have no contribution to the interferometry phase.
2012-04-20
PIER
Vol. 127, 335-350, 2012
Efficient Geosynchronous Circular SAR Raw Data Simulation of Extended 3-D Scenes
Qi Liu Wen Hong Weixian Tan Yirong Wu
Geosynchronous Circular Synthetic Aperture Radar (GeoCSAR) has the Circular SAR configuration and undergoes a near-ellipse geosynchronous track rather a 8''-like track of conventional GeoSAR. It could produce three dimensional (3-D) images of extended Earth scenes. GeoCSAR raw data simulator is of vital for predicting system performance, developing suitable data processing algorithms, etc.. It should include degrading conditions such as motion instability, angular deviations and orbit perturbations in order to approach the real situation. The common generation algorithm of raw data in time domain is precise but time-consuming for extended 3-D scene. In this paper, a novel raw data simulation algorithm based on inverse Improved Polar Format Algorithm (IPFA) for GeoCSAR was proposed, which possessed both the advantages of precision of time domain simulator and efficiency of frequency domain simulator. Implementation details were presented, and several simulation results were provided and analyzed to validate the algorithm.
2012-04-20
PIER
Vol. 127, 319-334, 2012
Study and Simulation of an Edge Couple Split Ring Resonator (Ec-SRR) on Truncated Pyramidal Microwave Absorber
Hassan Nornikman Badrul Hisham Ahmad Mohamad Zoinol Abidin Abdul Aziz Mohd Fareq Bin Abd Malek Hindstan Imran Abdul Rani Othman
Split ring resonator (SRR) can potentially be used as a design to be incorporated onto the truncated pyramidal microwave absorber. This study considers three different patterns of edge couple split ring resonator (EC-SRR) designs. Each EC-SRR design is then placed onto the truncated pyramidal microwave absorber. Outer split gap dimension widths of the EC-SRR are varied, and the various S21 performances are compared. This EC-SRR truncated pyramidal microwave absorber is simulated using CST Microwave Studio simulation software. The study and simulation are performed in low frequency range (0.01 GHz to 1 GHz) as well as in microwave frequencies range (1 GHz to 20 GHz). Simulation results of this EC SRR show improvement of reflection loss and S11 performance in the high frequency range of the pyramidal truncated microwave absorber.
2012-04-16
PIER
Vol. 127, 297-318, 2012
Transpose Return Relation Method for Designing Low Noise Oscillators
In this paper, a new linear method for optimizing compact low noise oscillators for RF/MW applications will be presented. The first part of this paper makes an overview of Leeson's model. It is pointed out, and it is demonstrates that the phase noise is always the same inside the oscillator loop. It is presented a general phase noise optimization method for reference plane oscillators. The new method uses Transpose Return Relations (RRT ) as true loop gain functions for obtaining the optimum values of the elements of the oscillator, whatever scheme it has. With this method, oscillator topologies that have been designed and optimized using negative resistance, negative conductance or reflection coefficient methods, until now, can be studied like a loop gain method. Subsequently, the main disadvantage of Leeson's model is overcome, and now it is not only valid for loop gain methods, but it is valid for any oscillator topology. The last section of this paper lists the steps to be performed to use this method for proper phase noise optimization during the linear design process and before the final non-linear optimization. The power of the proposed RRT method is shown with its use for optimizing a common oscillator, which is later simulated using Harmonic Balance (HB) and manufactured. Then, the comparison of the linear, HB and measurements of the phase noise are compared.
2012-04-16
PIER
Vol. 127, 277-295, 2012
Efficient Model Order Reduction for FEM Analysis of Waveguide Structures and Resonators
Grzegorz Fotyga Krzysztof Nyka Michal Mrozowski
An efficient model order reduction method for three-dimensional Finite Element Method (FEM) analysis of waveguide structures is proposed. The method is based on the Efficient Nodal Order Reduction (ENOR) algorithm for creating macro-elements in cascaded subdomains. The resulting macro-elements are represented by very compact submatrices, leading to significant reduction of the overall number of unknowns. The efficiency of the model order reduction is enhanced by projecting fields at the boundaries of macro-elements onto a subspace spanned by a few low-order waveguide modes. The combination of these two techniques results in considerable saving in overall computational time and memory requirement. An additional advantage of the presented method is that the reduced-order system matrix remains frequency-independent, which allows for very fast frequency sweeping and efficient calculation of resonant frequencies. Several numerical examples for driven and eigenvalue problems demonstrate the performance of the proposed methodology in terms of accuracy, memory usage and simulation time.
2012-04-16
PIER
Vol. 127, 259-275, 2012
Applications of Compressed Sensing for Multiple Transmitters Multiple Azimuth Beams SAR Imaging
Jing Li Shunsheng Zhang Junfei Chang
High speed analog-to-digital (A/D) sampling and a large amount of echo storage are two basic challenges of high resolution synthetic aperture radar (SAR) imaging. In this paper, a novel SAR imaging algorithm which named CS-MTMAB is proposed based on compressed sensing (CS) and multiple transmitters multiple azimuth beams (MTMAB). In particular, this new algorithm, which respectively reconstructs the targets in range and azimuth directions via CS technique, simultaneously provides a high resolution and wideswath two-dimensional map of the spatial distribution of targets with a significant reduction in the number of data samples beyond the Nyquist theorem and with an implication in simplification of radar architecture. The simulation results and analysis show that this new imaging scheme allows the aperture to be compressed and presents many important applications and advantages among which include reduced on-board storage constraints, higher resolution, lower peak side-lobe ratio (PSLR) and integrated side-lobe ratio (ISLR), less sampled data than the traditional SAR imaging algorithm, and also indicate that it has high robustness and strong immunity in the presence of serious noise. Finally, the real raw airborne SAR data experiment is performed to validate the proposed processing procedure.
2012-04-16
PIER
Vol. 127, 211-257, 2012
An Efficient Method for Computing Highly Oscillatory Physical Optics Integral
Yumao Wu Li Jun Jiang Weng Cho Chew
In this work, we use the numerical steepest descent path (numerical SDP) method in complex analysis theory to calculate the highly oscillatory physical optics (PO) integral with quadratic phase and amplitude variations on the triangular patch. The Stokes' phenomenon will occur due to various asymptotic behaviors on different domains. The stationary phase point contributions are carefully studied by the numerical SDP method and complex analysis using contour deformation. Its result agrees very well with the leading terms of the traditional asymptotic expansion. Furthermore, the resonance points and vertex points contributions from the PO integral are also extracted. Compared with traditional approximate asymptotic expansion approach, our method has significantly improved the PO integral accuracy by one to two digits (10-1 to 10-2) for evaluating the PO integral. Moreover, the computation effort for the highly oscillatory integral is frequency independent. Numerical results for PO integral on the triangular patch are given to verify the proposed numerical SDP theory.
2012-04-13
PIER
Vol. 127, 189-210, 2012