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Vol. 39

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2012-04-04 PIER B Vol. 39, 393-409, 2012. doi:10.2528/PIERB12021607

Dual Band-Notched UWB Antenna Based on Spiral Electromagnetic-Bandgap Structure

Feng Xu, Zheng-Xin Wang, Xu Chen, , and Xin-An Wang

An ultra-wideband (UWB) printed monopole antenna with dual band-notched characteristics is proposed. Two spiral electromagnetic-bandgap (EBG) structures placed on the front and back side of the substrate are employed to create two notch bands at 5.2 and 5.8 GHz for the lower and upper bands of the wireless local-area network (WLAN), respectively. The notch-frequency can be tuned, and the band width is narrow and adjustable. Furthermore, the spiral EBG structure used in this design are more compact than conventional mushroom-type EBG. Equivalent circuit model is extracted and discussed to explain the operating mechanism of this structure. The proposed antenna has been simulated and measured, good agreement between calculated and experimental results has been achieved.

2012-04-03 PIER B Vol. 39, 373-392, 2012. doi:10.2528/PIERB12011212

Variational SAR Image Segmentation Based on the G0 Model and an Augmented Lagrangian Method

Jilan Feng, Zongjie Cao, and Yiming Pi

This paper present a fast algorithm for synthetic aperture radar (SAR) image segmentation based on the augmented Lagrangian method (ALM). The proposed approach considers the segmentation of SAR images as an energy minimization problem in a variational framework. The energy functional is formulated based on the statistical characteristic of SAR images. The total variation regularization is used to impose the smoothness constraint of the segmentation result. To solve the optimization problem efficiently, the energy functional is firstly modified to be convex and differentiable by using convex relaxing and variable splitting techniques, and then the constrained optimization problem is converted to an unconstrained one by using the ALM. Finally the energy is minimized with an iterative minimization algorithm. The effectiveness of the proposed algorithm is validated by experiments on both synthetic and real SAR images.

2012-03-30 PIER B Vol. 39, 355-371, 2012. doi:10.2528/PIERB12012604

An Interpolation Method to Calibrate Electromagnetic Probes in Semi-Anechoic Chambers

Ciro Tremola, Marco A. Azpurua, Eduardo Paez, Daniel Ormeno, and Alejandro Rebolledo

Based upon the standard IEEE 1309, a new calibration method for electromagnetic (EM) probes is proposed. The aforementioned method compares the electric field strength measured with the EM probe subject to calibration with the E-field intensity calculated through a linear interpolation of the corrected measurement using a reference EM probe. The corrected measurement results are computed by means of the calibration factors stated in the calibration certificate of the reference EM probe. The conditions and criteria under which it is possible to calibrate EM probes inside semi-anechoic chambers in the frequency range of 80 MHz to 1 GHz, are presented. The results shows that the calibration method proposed in this paper is characterized by deviations of less than 1 dB in almost all the frequencies considered, verifying the reliability of the method. The proposed approach is very useful for registering the measurement drift of EM probes used in EMC testing laboratories.

2012-03-26 PIER B Vol. 39, 337-354, 2012. doi:10.2528/PIERB11123011

Jute and Tea Discrimination through Fusion of SAR and Optical Data

Dipanwita Haldar, Chakrapani Patnaik, Shiv Mohan, and Manab Chakraborty

Remote sensing approaches based on both optical and microwave region of EM spectra have been widely adapted for large scale crop monitoring and condition assessment. Visible, infrared and microwave wavelengths are sensitive to different crop characteristics, thus data from optical and radar sensors are complementary. Synthetic Aperture Radar (SAR) responds to the large scale crop structure (size, shape and orientation of leaves, stalks, and fruits) and the dielectric properties of the crop canopy. Research is needed to assess the saturation effects of SAR data and to investigate the synergy between the optical and SAR imagery for exploring various dimensions of crop growth which is not possible with any one of them singly with higher degree of accuracy. An attempt has been made to study the potential of SAR and optical data individually and by fusing them to separate various landcover classes. Two-date and three-date SAR data could distinguish jute and tea crop with 70-85% accuracy, while cloud free optical data (green, red and infrared bands) resulted in accuracy 80-85%. On fusing the optical and SAR single date data of May, 29 2010 using Brovey method, an accuracy of 85{\%} was obtained. PCA and HSV with munsell based approaches resulted in similar accuracies but HSV performed the best among these. This emphasizes on the synergistic effect of SAR and optical data. Also the fused data could be used to delineate the crop condition and age by inputs like NDVI from optical and XPR (Cross polarization ratio) from SAR data. The co- and cross polarization ratios along with various indices viz. Biomass Index (BMI), Volume Scattering Index (VSI) and canopy structural index (CSI) were used to discriminate tea from jute. Due to differences in structural component of tea and jute at early season as manifested by the indices, there is clear separability as observed from the mean values. Among the dual polarization combinations, HV/VV performed the best (70%) followed by HV/HH (62%) and lastly HH/VV (42%). Among the single best indices for discrimination BMI performed the best. Combination of Co, Cross-polarization and BMI yields around 80% classification accuracy. BMI and VSI combination yielded the best classification accuracy of 84%. This level of accuracy obtained was much superior to that of multidate HH polarization SAR data.

2012-03-26 PIER B Vol. 39, 319-335, 2012. doi:10.2528/PIERB12022109

Amplitude and Directional of Arrival Estimation: Comparison Between Different Techniques

Fawad Zaman, Ijaz Mansoor Qureshi, Aqdas Naveed, Junaid Ali Khan, and Raja Muhammad Asif Zahoor

In this work, we propose a method based on Genetic algorithm hybridized with Pattern Search for joint estimation of Amplitude and Direction of Arrival, azimuth as well as elevation angles using L-type array. Four other schemes i.e., the Genetic algorithm, Pattern Search, Simulated Annealing and Simulated Annealing hybridized with Pattern Search are also discussed and compared with Genetic algorithm hybridized with Pattern Search. Multiple sources are taken in the far field of sensors array and Mean Square Error is taken as a fitness function. This fitness function is optimal in nature and requires only a single snapshot. It avoids any ambiguity or required permutation as in some other methods to link it with angles found in the previous snapshot. The reliability and effectiveness of the proposed scheme is tested on the basis of Monte- Carlo simulations and its statistical analysis.

2012-03-24 PIER B Vol. 39, 301-318, 2012. doi:10.2528/PIERB12021404

Design and Fabrication of RF-MEMS Switch for V-Band Reconfigurable Application

Thanh Mai Vu, Gaetan Prigent, Jinyu Ruan, and Robert Plana

This paper presents a study of RF MEMS switch designed to be integrated in tunable filters for applications from W-frequency band to V-frequency band. Along the whole process, we go into detail of each procedure to present a complete study from design to fabrication and characterization of a RF-MEMS switch. The proposed concepts are validated by experimental results.

2012-03-22 PIER B Vol. 39, 281-299, 2012. doi:10.2528/PIERB12020304

Electromagnetic Vector-Sensor Array Processing for Distributed Source Localization

X.M. Shi and Zhiwen Liu

We consider the problem of direction-of-arrival (DOA) estimation for distributed signals with electromagnetic vector sensors, of which each provides measurements of the complete electric and magnetic fields induced by electromagnetic (EM) signals. In this paper, we consider situations where the sources are distributed not only in space with a deterministic angular signal density,but also in polarization with partially polarized components. A distributed signals general model with electromagnetic vector-sensor array (EMVS-DIS) is established with some reasonable assumptions. Based on the EMVS-DIS model, the minimum-variance distortionless response (MVDR) estimators for distributed source DOA are derived. MVDR estimators do not require the knowledge of the effective dimension of the pseudosignal subspace. We compare our method with the distributed signal MUSIC-like estimator in electromagnetic vector-sensor arrays. The simulation studies show significant advantages in using the proposed EMVS-DIS model with electromagnetic vector sensors. Simulation results show that the new MVDR method outperforms the MUSIC-like algorithm by reducing the estimation RMSE and improving resolution performance for scenario with distributed sources. A robustness study of MVDR localizer was also conducted via simulations.

2012-03-21 PIER B Vol. 39, 267-280, 2012. doi:10.2528/PIERB12011110

The Role of Fibre Orientation on the Electromagnetic Performance of Waveguides Manufactured from Carbon Fibre Reinforced Plastic

Alexe Bojovschi, Kelvin J. Nicholson, Amir Galehdar, Paul J. Callus, and Kamran Ghorbani

Aircraft skins manufactured from carbon fibre reinforced plastic (CFRP) can simultaneously support structural load and act as antennas. This offers the potential for disproportionately large antenna elements and arrays, and thus enhanced aircraft capability. The efficient design of such structures requires that the link between CFRP microstructure and electromagnetic performance be established. This paper presents a method of predicting the electromagnetic attenuation of waveguides manufactured from CFRP. The method considers both the orthotropic, complex conductivity of CFRP, high in the fibre direction and low transverse to it, and the local electric fields in waveguides, which vary with location and frequency. The method was validated experimentally using waveguides manufactured from aerospace grade IM7/977-3 prepreg tape with [0 90]s, [90 0]s and [±45]s ply stacking sequences.

2012-03-20 PIER B Vol. 39, 241-266, 2012. doi:10.2528/PIERB12011902

Design and Optimization of Multilayered Electromagnetic Shield Using a Real-Coded Genetic Algorithm

Heeralal Gargama, Sanjay Kumar Chaturvedi, and Awalendra K. Thakur

We report optimized design of multilayered electromagnetic shield using real coded genetic algorithm. It is observed that the shielding effectiveness in multilayer design is higher than single layered counterpart of equal thickness. An effort has been made to develop alternative approach to achieve specific objective of identifying the design characteristics of each layer in the multilayered shielding configuration. The proposed approach incorporates interrelated factors, such as, absorption and reflection in the design optimization as per specific shielding requirements. The design problem has been solved using shielding effectiveness theory based on transmission line (TL) modeling and real-coded genetic algorithm (GA) with simulated binary crossover (SBX) and parameter-based mutation. The advantage of real-coded GA lies in efficient solution for electromagnetic interference (EMI) shielding design due to its strength in solving constraint optimization problems of continuous variables with many parameters without any gradient information. Additionally, the role of material parameters, such as permittivity and permeability on reflection characteristics and shielding effectiveness has also been investigated and optimized using the proposed models and real-coded GA. Theoretical optimization of electromagnetic parameters has been carried out for SE ~40 dB for many industrial/commercial applications and SE ~80 dB for military applications.

2012-03-15 PIER B Vol. 39, 225-239, 2012. doi:10.2528/PIERB11121212

Four-Dimensional SAR Imaging Scheme Based on Compressive Sensing

Xiao-Zhen Ren, Yong Feng Li, and Ruliang Yang

The observation data obtained from 4-D synthetic aperture radar system is sparse and non-uniform in the baseline-time plane. Hence, the imaging results acquired by traditional Fourier-based methods are limited by high sidelobes. Considering the sparse structure of actual target space in high frequency radar application, a novel 4-D imaging scheme based on compressive sensing is proposed in this paper. Firstly, the azimuth-slant range image is acquired by traditional pulse compression. Then, the basis matrix and the measurement matrix are constructed based on the sparse distribution of the radar positions and the signal form after the azimuth-slant range compression. Moreover, a weighted matrix related to the supporting field of the target is introduced to the cost function. Finally, the elevation-velocity image is reconstructed with this new cost function. Simulation results confirm the effectiveness of the proposed method.

2012-03-15 PIER B Vol. 39, 197-223, 2012. doi:10.2528/PIERB12020112

Surface Parameter Estimation Using Bistatic Polarimetric X-Band Measurements

Kais Khadhra, Thomas Boerner, David Hounam, and Madhu Chandra

The main purpose of this paper is to separately estimate the important surface parameters (soil moisture and roughness) by using full polarimetric bistatic measurements. The results provide a basis for new satellite application of future bistatic measurement systems such as the TanDEM-X satellite mission. Initially, bistatic X-band measurements, which have been recorded in the Bistatic Measurement Facility (BMF) at the DLR Oberpfaffenhofen, Microwaves and Radar Institute, will be presented. The bistatic measurement sets are composed of soils with different well-known statistical roughness scales and different moistures. The BMF has been calibrated using the Isolated Antenna Calibration Technique (IACT). The validation of the calibration was achieved by measuring the reflectivity of fresh water. In the second part, the assessment of the surface parameters (soil moisture and surface roughness) using the well calibrated data introduced in the former related part, will be detailed. The validation of the specular algorithm by estimating the soil moisture of two surfaces with different roughness scales will be reported. Additionally, a new technique using the coherent term of the Integral Equation Method (IEM) to estimate the soil roughness will be presented, as well as the sensitivity of phase and reflectivity with regard to moisture variation and therefore the penetration depth was evaluated. Current results demonstrate a non-linear relationship between the signal phase and the soil moisture, as expected, confirming the possibility of using DInSAR to measure variations in soil moisture.

2012-03-12 PIER B Vol. 39, 179-195, 2012. doi:10.2528/PIERB12011105

Combline Loadings of Printed Triangular Monopole Antennas for the Realization of Multi-Band and Wideband Characteristics

Homayoon Oraizi and Bahram Rezaei

In this paper, we use the concept of stub loadings of planar microstrip antennas to convert a single band antenna into a dual-band antenna used for WLAN. We load a planar triangular monopole (PTM) antenna by combline stubs attached to the edges of patch in order to obtain a second resonance frequency. The simple PTM antenna is first designed to produce the lower resonance frequency and the geometry of combline stubs is then optimally designed to generate the higher resonance frequency to realize a dual-band or a wideband antenna. Three prototype models of PTM antennas are designed, fabricated and measured. Their performances verify the concept of inductive loadings of planar antennas by combline stubs for the realization of dual-band and wideband performance for WLAN.

2012-03-07 PIER B Vol. 39, 163-178, 2012. doi:10.2528/PIERB12012103

A Simple Pattern Recognition Approach for Monitoring Incipient Stator Faults in Salient-Pole Synchronous Generators

J. A. Dente and Paulo José da Costa Branco

This paper studies the effect of incipient stator faults in salient-pole synchronous generators and its detection using a simple pattern recognition methodology. A theoretical linear model for the synchronous generator is first developed to provide the relationships between stator and rotor harmonic currents and possible incipient faults on stator electric circuits. All theoretical findings were verified by experimental results. The stator currents and its αβ and dq representations have been used to detect incipient faults on salient-pole synchronous generators using a similar pattern recognition technique which have been proposed for induction machines. From our test results, it became clear that the proposed methodology is capable of correctly monitoring incipient stator faults in salient-pole synchronous generators.

2012-03-02 PIER B Vol. 39, 141-161, 2012. doi:10.2528/PIERB11122705

Influence of Cellular Properties on the Electric Field Distribution Around a Single Cell

Hui Ye, Marija Cotic, Michael G. Fehlings, and Peter L. Carlen

Electric fields have been widely used for the treatment of neurological diseases, using techniques such as non-invasive brain stimulation. An electric current controls cell excitability by imposing voltage changes across the cell membrane. At the same time, the presence of the cell itself causes a re-distribution of the local electric field. Computation of the electric field distribution at a single cell microscopic level is essential in understanding the mechanism of electric stimulation. In addition, the impact of the cellular biophysical properties on the field distribution in the vicinity of the cell should also be addressed. In this paper, we have begun by first computing the field distribution around and within a spherical model cell. The electric fields in the three regions differed by several orders of magnitude. The field intensity in the extracellular space was of the same order as that of the externally applied field, while in the membrane, it was calculated to be several thousand times greater than the applied field. In contrast, the field intensity inside the cell was greatly attenuated to approximately 1/133th of the applied field. We then performed a detailed analysis on the dependency of the local field distribution on both the electrical properties (i.e., conductivity, dielectricity), and the geometrical properties (i.e., size, membrane thickness) of the target cell. Variations of these parameters caused significant changes to the amplitude and direction of the electric field around a single cell. The biophysical mechanisms of such observations and their experimental implications are discussed. These results highlight the significance of considering cellular properties during the electric stimulation of neuronal tissues.

2012-03-02 PIER B Vol. 39, 115-139, 2012. doi:10.2528/PIERB11122208

Neighborhood-Based Algorithm to Facilitate the Reduction of Skin Reflections in Radar-Based Microwave Imaging

B. Maklad, C. Curtis, Elise C. Fear, and Geoffrey G. Messier

Radar-based microwave imaging is being investigated as a complementary diagnostic tool for breast cancer detection. One of the major challenges associated with radar-based breast imaging is the removal of the overwhelming reflection caused by the skin. This paper presents an algorithm that has been designed for realistic 3D scenarios. The algorithm is tested on a variety of realistic 3D numerical breast models, as well as measured data from a phantom and patient. In all cases, the reflections from the skin are significantly reduced, facilitating detection of known tumors.

2012-02-22 PIER B Vol. 39, 89-114, 2012. doi:10.2528/PIERB12012409

Towards Broadband Over Power Lines Systems Integration: Transmission Characteristics of Underground Low-Voltage Distribution Power Lines

Athanasios G. Lazaropoulos

A complete methodology is employed to determine the transmission characteristics of low-voltage/broadband over power lines (LV/BPL) channels associated with underground power distribution networks, in the light of the multiconductor transmission line (MTL) theory. The established bottom-up approach, already used to treat overhead and underground MV/BPL transmission, is extended to analyze BPL transmission in three-phase N-conductor underground lines with common shield and armor. This analysis shows that these cables may support N + 2 modes, giving rise to N + 2 separate transmission channels which reduce to N + 1 if the armor either does not exist or is grounded and to N if the shield is also grounded. In addition to the generalized analysis, a simplified approximation concerning three-phase N-conductor underground cables is also presented. Taking the generalized analysis and the simplified approximation into account, their numerical results concerning attenuation in various underground LV/BPL channels in the frequency range 1-100 MHz are validated against relevant sets of simulations and measurements with satisfactory accuracy and compared to corresponding results of overhead and underground MV/BPL channels. It has been verified that the attenuation in overhead and underground BPL channels depends drastically on power distribution grid type, MTL configuration, and cables used. Moreover, the attenuation in underground LV/BPL channels exhibits a lowpass behavior, is significantly higher than that of overhead MV/BPL ones, and is comparable to that of underground MV/BPL ones. A consequence of the proposed methodology is that it can facilitate the integration process and intraoperability of LV/BPL and MV/BPL systems through their common physical layer handling.

2012-02-22 PIER B Vol. 39, 71-88, 2012. doi:10.2528/PIERB11120601

FDTD Analysis of the Dispersion Characteristics of the Metal PBG Structures

Ashutosh Singh and Pradip Kumar Jain

Two dimensional metallic photonic band gap (PBG) structures, which have higher power handling capability, have been analyzed for their dispersion characteristics. The analysis has been performed using finite difference time domain (FDTD) method based on the regular orthogonal Yee's cell. A simplified unit cell of triangular lattice PBG structure has been considered for the TE and TM modes of propagation. The EM field equations in the standard central-difference form have been taken in FDTD method. Bloch's periodic boundary conditions have been used by translating the boundary conditions along the direction of periodicity. For the source excitation, a wideband Gaussian pulse has been used to excite the possible modes in the computational domain. Fourier transform of the probed temporal fields has been calculated which provides the frequency spectrum for a set of wave vectors. The determination of eigenfrequencies from the peaks location in the frequency spectrum has been described. This yields the dispersion diagram which describes the stop and pass bands characteristics. Effort has been made to describe the estimation of defect bands introduced in the PBG structures. Further, the present orthogonal FDTD results obtained have been compared with those obtained by a more involved non-orthogonal FDTD method. The universal global band gap diagrams for the considered metal PBG structure have been obtained by varying the ratio of rod radius to lattice constant for both polarizations and are found identical with those obtained by other reported methods. Convergence of the analysis has been studied to establish the reliability of the method. Usefulness of these plots in designing the devices using 2-D metal PBG structure has also been illustrated.

2012-02-20 PIER B Vol. 39, 55-69, 2012. doi:10.2528/PIERB12010705

New Class of Surface Magnon Polaritons in Enantiomeric Antiferromagnetic Structures

Roland Tarkhanyan

A novel class of surface magnon polaritons supported in identical enantiomeric antiferromagnetic structures is presented. The surface waves arise due to bianisotropy. The existence of two distinct surface modes with unusual dispersion and polarization properties is predicted. The role of losses is investigated and the propagation length of the surface waves is determined.

2012-02-20 PIER B Vol. 39, 39-53, 2012. doi:10.2528/PIERB11122108

Inverse Scattering Shape Reconstruction of 3D Bacteria Using the Level Set Algorithm

Ahmed M. Hassan, Mohammad Reza Hajihashemi, and Magda El-Shenawee

Bacteria exist in a variety of groups of shapes, sizes, and single or multiple cell formations. In this paper, the level set shape reconstruction technique, the method of moments, and the marching cubes methods are integrated in the high frequency band for imaging three dimensional bacteria. The time step and the resolution of the marching cubes method are investigated to smooth the error function of the level set and hence speed up the convergence at high frequencies. The numerical results demonstrate the robustness of the level set algorithm for the detection of bacteria based on their shapes. The three dimensional shape reconstructions of unknown bacteria can be utilized to classify biological warfare agents.

2012-02-12 PIER B Vol. 39, 1-37, 2012. doi:10.2528/PIERB11112106

Solving for Micro- and Macro-Scale Electrostatic Configurations Using the Robin Hood Algorithm

Joseph A. Formaggio, Predrag Lazic, Thomas Joseph Corona, Hrvoje Stefancic, Hrvoje Abraham, and Ferenc Gluck

We present a novel technique by which highly-segmented electrostatic configurations can be solved. The Robin Hood method is a matrix-inversion algorithm optimized for solving high density boundary element method (BEM) problems. We illustrate the capabilities of this solver by studying two distinct geometry scales: (a) the electrostatic potential of a large volume beta-detector and (b) the field enhancement present at surface of electrode nano-structures. Geometries with elements numbering in the O(105) are easily modeled and solved without loss of accuracy. The technique has recently been expanded so as to include dielectrics and magnetic materials.