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2010-10-01
PIER
Vol. 108, 433-447, 2010
download: 116
Extended Doublet Bandpass Filters Implemented with Microstrip Resonator and Full-/Half-Mode Substrate Integrated Cavities
Lin-Sheng Wu Jun-Fa Mao Wei Shen Wen-Yan Yin
Two extended doublet bandpass filters with compact size and good spurious suppression characteristic are proposed. One is built up by a dual-mode microstrip resonator with a full-mode substrate integrated cavity, while the other is composed of a microstrip resonator and a half-mode cavity. The relationship between the location of their transmission zeros and the impedance ratio of the microstrip resonator is analyzed theoretically. Our proposed filters only occupy the areas of 0.69λ02/εr and 0.51λ02/εr, and they also have wide upper stopband. The predicted performances are demonstrated by the reasonable agreement obtained between their simulated and measured S-parameters.
EXTENDED DOUBLET BANDPASS FILTERS IMPLEMENTED WITH MICROSTRIP RESONATOR AND FULL-/HALF-MODE SUBSTRATE INTEGRATED CAVITIES
2010-09-30
PIER
Vol. 108, 417-432, 2010
download: 164
A Novel Adaptive Wi-Fi System with RFID Technology
Mohd Faizal Bin Jamlos Tharek Bin Abdul Rahman Muhammad Ramlee Kamarudin P. Saad M. Amir Shamsudin A. M. M. Dahlan
A novel adaptive Wireless-Fidelity (Wi-Fi) system is the combination of radio frequency identification (RFID) technology, programmable intelligent microcontroller development board (PIDB) and reconfigurable antenna with beam shape characteristics. The system is capable to sustain a Wi-Fi signal adaptively above its threshold level (-81 dBm) within a range up to 100 m across three different buildings with variety indoor environments and floors. It is found that the modified ground reflection model has successfully predicted the total path loss of the test-bay buildings which consist of corridors, several floors and windows. The modified propagation model is extremely crucial in determining the projection and height of reconfigurable antenna to efficiently cover the scattered measurement points across the three buildings. The need of comparable signal strength is compulsory since the signal strength between 2.4 GHz of reconfigurable beam shape antenna and 0.433 GHz of RFID tag is different within the same distance. When reconfigurable beam shape antenna radiates with a minimum gain of 4.85 dBi, the measured signal strength shows that most of the measurement points are below Wi-Fi‟s threshold level which is from -69.001 dBm to -115.4530 dBm. However, the proposed system is able to boost all the signal strength above the threshold level with three different gain of reconfigurable beam shape antenna, 7.2 dBi, 9.9 dBi and 14.64 dBi through the activation of mobile RFID tag at different measurement points at one time. The boosted signal strengths are within the range of -69 dBm to -73.056 dBm. The capability of the mobile RFID tag in producing certain level of signal strength has been successfully exploited as a wireless stimulator for the system to adaptively activate certain PIN diode switches of reconfigurable beam shape antenna in this finding. The proposed system also has a great potential in realizing a new smart antenna system replacing the conventional switching beam array (SBA) antenna.
A NOVEL ADAPTIVE WI-FI SYSTEM WITH RFID TECHNOLOGY
2010-09-29
PIER
Vol. 108, 401-416, 2010
download: 159
Transmitter-Grouping Robust Capon Beamforming for Breast Cancer Detection
Dallan Byrne Martin O'Halloran Edward Jones Martin Glavin
Early detection of tumor tissue is one of the most significant factors in the successful treatment of breast cancer. Microwave Breast Imaging methods are based on the dielectric contrast between normal and cancerous tissues at microwave frequencies. When the breast is illuminated with a microwave pulse, the dielectric contrast between these tissues can result in reflected backscatter. These reflected signals, containing tumor backscatter, are spatially focused using a beamformer which compensates for attenuation and phase effects as the signal propagates through the breast. The beamformer generates an energy profile of the breast where high energy regions suggest the presence of breast cancer. Data-Adaptive (DA) beamformers, use an approximation of the desired channel response based on the recorded signal data, as opposed to Data-Independent (DI) algorithms which use an assumed channel model. A novel extension of the DA Robust Capon Beamformer (RCB) is presented in this paper which is shown to significantly outperform existing beamformers, particularly in a dielectrically heterogeneous breast. The algorithm is evaluated on three anatomically accurate electromagnetic (EM) breast models with varying amounts of heterogeneity. The novel beamforming algorithm is compared, using a range of performance metrics, against a number of existing beamformers.
TRANSMITTER-GROUPING ROBUST CAPON BEAMFORMING FOR BREAST CANCER DETECTION
2010-09-30
PIER
Vol. 108, 385-400, 2010
download: 124
Larger Absolute Band Gaps in Two-Dimensional Photonic Crystals Fabricated by a Three-Order-Effect Method
Hai Li Xiangbo Yang
In this paper, based on different influences of the lattice symmetry, the geometry of dielectric rod, and the structure of unit cell to absolute gaps we propose a so-called three-order-effect method for the construction of two-dimensional (2D) photonic crystals (PCs) with larger absolute gaps. As an example, by means of our approach we fabricate a 2D hexagonal lattice of cylinder with an optimal rod adding at the center of the unit cell, where the absolute gap is larger than that of the PC with similar structure studied by other group previously. On the other hand, we also find that many of the 2D PCs with larger absolute gaps reported previously possess optimal first-order and second-order substructures. Our three-order-effect method would be useful for the design of 2D PCs with larger absolute gaps.
LARGER ABSOLUTE BAND GAPS IN TWO-DIMENSIONAL PHOTONIC CRYSTALS FABRICATED BY A THREE-ORDER-EFFECT METHOD
2010-09-28
PIER
Vol. 108, 361-383, 2010
download: 114
Theoretical Establishment and Evaluation of a Novel Optimal Pyramidal Horn Design Criterion
Konstantinos B. Baltzis
This paper proposes a novel design criterion for optimal pyramidal horns. According to it, the optimal aperture phase error parameters of a pyramidal horn are determined from the minimization of the horn's lateral surface area. We present two families of curves that illustrate the optimal aperture phase error parameters for frequency and directivity values in the area of practical interest. We also discuss two simple approximate design methods for the calculation of the optimal horn parameters. Comparisons with well-known design methods demonstrate the efficacy of our approach. The proposed criterion produces the lightest horn for a given directivity; as a result its fabrication requires less material compared to other structures. Moreover, the designed horns have smaller aperture area and occupy less space. The present approach is a useful design tool when the size and weight of a pyramidal horn or its manufacturing cost are of concern.
THEORETICAL ESTABLISHMENT AND EVALUATION OF A NOVEL OPTIMAL PYRAMIDAL HORN DESIGN CRITERION
2010-09-26
PIER
Vol. 108, 343-359, 2010
download: 132
Scanning Antenna at THz Band Based on Quasi-Optical Techniques
Wen-Bin Dou Hong Fu Meng Bei Nie Zong-Xin Wang Fei Yang
A scanning antenna at THz region is proposed and developed based on the quasi-optical techniques. It is composed of extended hemispherical lens/dielectric waveguide feed, inverse Cassegrain antenna, and transform lens. The extended hemispherical lens/dielectric waveguide feed is the key innovation of the scanning antenna. The inverse Cassegrain antenna is realized at THz region with special process and techniques, and the transform lens is used to match the input beam and the quasi-optical feed. The properties of the quasi-optical antenna are simulated with the FDTD method, and the experiments are carried out. The measured radiation pattern of the antenna is in agreement with the simulated result.
SCANNING ANTENNA AT THZ BAND BASED ON QUASI-OPTICAL TECHNIQUES
2010-09-24
PIER
Vol. 108, 323-341, 2010
download: 107
Analysis of Perpendicular Crossing Dielectric Waveguides with Various Typical Index Contrasts and Intersection Profiles
Hung-Wen Chang Yan-Huei Wu
We present a rigorous 2D numerical study of the transmission, reflection and crosstalk coefficients of the perpendicular, identical dielectric crossing waveguide with various core-cladding index contrasts for both TE and TM polarizations. Our method is based on a hybrid frequency-domain finite-difference (FD-FD) technique computed with the cross-symmetry model. By varying the intersection profile, such as the circular, filleted, tapered and elliptical shapes, we achieve, even for a large 3.5 to 1.5 index ratio, a low 0.25dB insertion loss, a nontrivial reduction over the straight direct crossing case.
ANALYSIS OF PERPENDICULAR CROSSING DIELECTRIC WAVEGUIDES WITH VARIOUS TYPICAL INDEX CONTRASTS AND INTERSECTION PROFILES
2010-09-23
PIER
Vol. 108, 307-322, 2010
download: 139
Can Maxwell's Fish Eye Lens Really Give Perfect Imaging?
Fei Sun Sailing He
Both explicit analysis and FEM numerical simulation are used to analyze the field distribution of a line current in the so-called Maxwell's fish eye lens [bounded with a perfectly electrical conductor (PEC) boundary]. We show that such a 2D Maxwell's fish eye lens cannot give perfect imaging due to the fact that high order modes of the object field can hardly reach the image point in Maxwell's fish eye lens. If only zeroth order mode is excited, a good image of a sharp object may be achieved in some cases, however, its spot-size is larger than the spot size of the initial object field. The image resolution is determined by the field spot size of the image corresponding to the zeroth order component of the object field. Our explicit analysis consists very well with the FEM results for a fish eye lens. Time-domain simulation is also given to verify our conclusion. Multi-point images for a single object point are also demonstrated.
CAN MAXWELL'S FISH EYE LENS REALLY GIVE PERFECT IMAGING?
2010-09-23
PIER
Vol. 108, 293-306, 2010
download: 127
Enhancement of Blue Light Emission Using Surface Plasmons Coupling with Quantum Wells
Jia Zhao Kang Li Fanmin Kong Du Liu-Ge
3-dimension finite-difference time-domain (FDTD) method is used to simulate the enhanced blue light emission of gallium nitride light emitting diode (GaN-LED) using the surface-plasmons (SPs) coupling with the quantum wells. The numerical simulation results demonstrate that when the silver film is coated on GaN-LED, the excited SPs play a key role in the enhanced blue light emission, and the enhancement depends on the geometries of GaN-LED and silver film. An enhancement factor is given to describe the enhancement effect of light emission. By changing the structure parameters of GaN-LED and silver film, the enhanced peak of the light emission in the visible region can be controlled. Under the optimal parameters, about 17 times enhancement at 460 nm can be obtained, and the enhancement effect is evidently demonstrated by the SPs field distribution.
ENHANCEMENT OF BLUE LIGHT EMISSION USING SURFACE PLASMONS COUPLING WITH QUANTUM WELLS
2010-09-22
PIER
Vol. 108, 277-291, 2010
download: 219
Log-Amplitude Variance of Laser Beam Propagation on the Slant Path through the Turbulent Atmosphere
Hong-Yan Wei Zhen-Sen Wu Qingliang Ma
Based on the altitude-dependent model of ITU-R slant atmospheric turbulence structure constant, the log-amplitude variance of laser beam propagation on the slant path through turbulent atmosphere is obtained with transmitter and receiver parameters and can be degenerated to the result of the horizontal path with atmospheric structure constant as a fixed value. These expressions are convenient tools for beam-wave analysis. Finally, we apply the ITU-R turbulence structure constant model to calculate collimated, divergent and convergent beam log-amplitude variance. The numerical conclusions indicate the log-amplitude variance of laser beam propagation on slant path is generally smaller than those on horizontal path.
LOG-AMPLITUDE VARIANCE OF LASER BEAM PROPAGATION ON THE SLANT PATH THROUGH THE TURBULENT ATMOSPHERE
2010-09-22
PIER
Vol. 108, 249-275, 2010
download: 120
Performance Evaluation of Track Association and Maintenance for a Mfpar with Doppler Velocity Measurements
Faruk Kural Feza Arikan Orhan Arikan Murat Efe
This study investigates the effects of incorporating Doppler velocity measurements directly into track association and maintenance parts for single and multiple target tracking unit in a multi function phased array radar (MFPAR). Since Doppler velocity is the major discriminant of clutter from a desired target, the measurement set has been expanded from range, azimuth and elevation angles to include Doppler velocity measurements. We have developed data association and maintenance part of a well known tracking method, Interacting Multiple Model Probabilistic Data Association Filter (IMMPDAF), with the Doppler velocity measurements and demonstrated the performance improvement through simulations in terms of track update interval, track maintenance rate, RMS position estimation error, probability of detection and processing time. Since Doppler velocity measurements are employed in track maintenance, non-linear filters are used in the scheme leading to the use of Extended Kalman Filter (EKF) based PDAF. Comprehensive simulations have revealed that using Doppler velocity measurements along with 3D position measurements in heavy clutter conditions lead to an increase in track maintenance rate, track update interval; a decrease in position estimation error, processing time and no considerable effect on the probability of detection. This result is very significant for the efficient use of the limited resources of a multi function phased array radar.
PERFORMANCE EVALUATION OF TRACK ASSOCIATION AND MAINTENANCE FOR A MFPAR WITH DOPPLER VELOCITY MEASUREMENTS
2010-09-21
PIER
Vol. 108, 235-247, 2010
download: 125
Fast Inhomogeneous Plane Wave Algorithm for Analysis of Composite Bodies of Revolution
Xi Rui Jun Hu Qing Huo Liu
A fast inhomogeneous plane wave algorithm is developed for the electromagnetic scattering problem from the composite bodies of revolution (BOR). Poggio-Miller-Chang Harrington-Wu (PMCHW) approach is used for the homogeneous dielectric objects, while the electric field integral equation (EFIE) is used for the perfect electric conducting objects. The aggregation and disaggregation factors can be expressed analytically by using the Weyl identity. Compared with the traditional method of moments (MoM), both the memory requirement and CPU time, are reduced for large-scale composite BOR problems. Numerical results are given to demonstrate the validity and the efficiency of the proposed method.
FAST INHOMOGENEOUS PLANE WAVE ALGORITHM FOR ANALYSIS OF COMPOSITE BODIES OF REVOLUTION
2010-09-20
PIER
Vol. 108, 221-234, 2010
download: 142
Hybrid PIFA-Patch Antenna Optimized by Evolutionary Programming
Rocio Sanchez-Montero Sancho Salcedo-Sanz J. A. Portilla-Figueras Richard J. Langley
In this paper we study the optimization process of a novel hybrid antenna, formed by a Planar Inverted-F Antenna (PIFA) and a coplanar patch in the same structure, and intended to be used in mobile communications and WIFI applications simultaneously. This hybrid device has been recently proposed and characterized in the literature, and it has been shown that it allows a bandwidth of 850 MHz (49%) in the lower band and 630 MHz (11.25%) in the upper band. In spite of these good performance results, the fine tuning of the joint PIFA-patch parameters in the hybrid antenna is a hard task, not easy to automatize. In this paper we propose the use of an Evolutionary Programming (EP) approach, an algorithm of the Evolutionary Computation family, which has been shown to be very effective in continuous optimization problems. We use a real encoding of the antenna's parameters and the CST Microwave Studio simulator to obtain the performance of the antenna. The simulator is therefore incorporated to the EP algorithm as a part of the antenna's evaluation process. We will show that the EP is able to obtain very good sets of parameters in terms of the designer necessities, usually a larger bandwidth at the design frequencies. In this case, the bandwidth of the EP optimized antenna results in 980 MHz (55%) for the lower band and 870 MHz (17%) for the upper band.
HYBRID PIFA-PATCH ANTENNA OPTIMIZED BY EVOLUTIONARY PROGRAMMING
2010-09-17
PIER
Vol. 108, 205-219, 2010
download: 109
Analysis of Microwave Emission of Exponentially Correlated Rough Soil Surfaces from 1.4 GHz to 36.5 GHz
Peng Xu Kunshan Chen Leung Tsang
We analyzed the microwave emission from a rough soil surface with exponential correlation by characterizing its dependences of polarization, look angle, and frequency. Using the same set of physical surface parameters of rms height and correlation lengths, results are obtained for a wide range of frequencies at 1.4 GHz, 5 GHz, 10 GHz, 18 GHz, and 36.5 GHz. Accurate simulations for the 2-D scattering problem are conducted by Galerkin's method with the rooftop basis function, followed by near-field integration, fine discretization, and cubic spline interpolation of surfaces. The multilevel UV method was employed to accelerate the solution. Accuracy is ensured by energy conservation check. Simulation results are compared with SPM, KA and AIEM. Results suggest that there exists distinct emission characteristic between the exponential and the Gaussian correlated surface. These charcateristics should be very useful in developing retrieval algorithm of the soil moisture from emissivity measurements.
ANALYSIS OF MICROWAVE EMISSION OF EXPONENTIALLY CORRELATED ROUGH SOIL SURFACES FROM 1.4 GHz TO 36.5 GHz
2010-09-16
PIER
Vol. 108, 177-204, 2010
download: 202
The Effect of Soil Texture in Soil Moisture Retrieval for Specular Scattering at C-Band
Rishi Prakash Dharmendra Singh Nagendra Prasad Pathak
The objective of this paper is to analyze the behavior of specular scattering for different soil texture fields at various soil moisture (mv) and analyze the data to retrieve the soil moisture with minimizing the effect of the soil texture. To study the soil texture effect on specular scattering 10 different soil fields were prepared on the basis of change in soil constituents (i.e, percentage of sand, silt and clay) and experiments were performed in both like polarizations (i.e., HH-polarization and VV-polarization) at various incidence angles (i.e., varying incidence angle from 25°to 70°in step of 5°). Angular response of specular scattering coefficients (σ°hh in HH-polarization and σ°vv VV-polarization) were analyzed for different soil texture fields with varying soil moisture content whereas the surface roughness condition for all the observations were kept constant. The changes in specular scattering coefficient values were observed with the change in soil texture fields with moisture for both like polarizations. Further, copolarization ratio (P=(σ°hh/σ°vv) study was performed and it was observed that the dependency of copolarization ratio for change in soil texture field at constant soil moisture is less prominent whereas the value of copolarization ratio is varying with variation of moisture content. This emphasizes that copolarization ratio may be minimizing the effect of soil texture while observing the soil moisture on specular direction. Regression analysis is carried out to select the best suitable incidence angle for observing the moisture and texture at C-band in specular direction and 60°incidence angle was found the best suitable incidence angle. An empirical relationship between P and mv was developed for the retrieval of mv and the obtained relationship gives a good agreement with observed mv. In addition, mv was also retrieved through the Kirchhoff Approximation (SA) and a comparison was made with the retrieved results of empirical relationship. The empirical relationship outperformed the SA.
THE EFFECT OF SOIL TEXTURE IN SOIL MOISTURE RETRIEVAL FOR SPECULAR SCATTERING AT C-BAND
2010-09-14
PIER
Vol. 108, 155-175, 2010
download: 171
A Comparative Study on ISAR Imaging Algorithms for Radar Target Identification
Jong-Il Park Kyung-Tae Kim
Inverse synthetic aperture radar (ISAR) images represent the two-dimensional (2-D) spatial distribution of the radar cross-section (RCS) of an object and, thus, they can be applied to the problem of target identification. The traditional approach to ISAR imaging is the range-Doppler algorithm based on the 2-D Fourier transform. However, the 2-D Fourier transform often results in poor resolution ISAR images, especially when the measured frequency bandwidth and angular region are limited. Instead of the Fourier transform, high resolution spectral estimation techniques can be adopted to improve the resolution of ISAR images. These are the autoregressive (AR) model, multiple signal classification (MUSIC), and matrix enhancement and matrix pencil MUSIC (MEMP-MUSIC). In this study, the ISAR images from these high-resolution spectral estimators, as well as the FFT approach, are identified using a recently developed identification algorithm based on the polar mapping of ISAR images. In addition, each ISAR imaging algorithm is analyzed and compared in the framework of radar target identification. The results show that the dynamic range as well as the resolution of the ISAR images plays an important role in the identification performance. Moreover, the optimum size of the subarray (i.e. covariance matrix) for MUSIC and MEMP-MUSIC in terms of target identification is experimentally derived.
A COMPARATIVE STUDY ON ISAR IMAGING ALGORITHMS FOR RADAR TARGET IDENTIFICATION
2010-09-14
PIER
Vol. 108, 141-153, 2010
download: 150
A Dual-Wideband Bandpass Filter Based on E-Shaped Microstrip SIR with Improved Upper-Stopband Performance
Yan-Liang Wu Cheng Liao Xiang-Zheng Xiong
A novel dual-wideband microstrip bandpass filter (BPF) with improved upper-stopband performance is presented. With the use of some special structures such as E-shaped microstrip Stepped-Impedance Resonator (SIR) and input-output cross-coupling feed structure, this filter can generate five transmission zeros which are beneficial for improving its frequency selectivity and upper-stopband performance. Finally the microstrip dual-wideband BPF has been simulated, fabricated and measured. Measurement results show that the two passbands are centered at 3.7 GHz and 5.8 GHz with the fractional bandwidth of 31% and 13% respectively. Meanwhile more than 50% relative upper stopband bandwidth with 20 dB rejection has been realized. The simulated and measured results are in good agreement.
A DUAL-WIDEBAND BANDPASS FILTER BASED ON E-SHAPED MICROSTRIP SIR WITH IMPROVED UPPER-STOPBAND PERFORMANCE
2010-09-13
PIER
Vol. 108, 131-140, 2010
download: 137
Efficient Radar Target Recognition Using a Combination of Range Profile and Time-Frequency Analysis
Seung-Ku Han Hyo-Tae Kim Sang-Hong Park Kyung-Tae Kim
In this paper, a new hybrid classification method using both range profile (RP) and time-frequency image is proposed. The time-frequency image is obtained using the short-time Fourier transform before calculating the RP and this image is used for classification. 2-Dimensional Principal Components Analysis (2DPCA) is used to further compress the time-frequency image and to derive useful features from the image. The proposed method achieves a higher correct classification ratio than existing methods, especially when the signal-to-noise ratio is low.
EFFICIENT RADAR TARGET RECOGNITION USING A COMBINATION OF RANGE PROFILE AND TIME-FREQUENCY ANALYSIS
2010-09-10
PIER
Vol. 108, 101-130, 2010
download: 149
Electromagnetic Transients in Radio/Microwave Bands and Surge Protection Devices
Chandima Gomes Vernon Cooray
A comprehensive review has been done on the types of electromagnetic transients that may affect low voltage electrical systems. The paper discusses various characteristics of lightning, switching, nuclear and intentional microwave impulses giving special attention to their impact on equipment and systems. The analysis shows that transients have a wide range of rise time, half peak width, action integral etc. with respect to both source and coupling mechanism. Hence, transient protection technology should be more specific with regard to the capabilities of the protection devices. Furthermore, we discuss the components and techniques available for the protection of low voltage systems from lightning generated electrical transients and the adequacy of International Standards in addressing the transient protection issues. The outcome of our analysis questions the suitability of 8/20 μs test current impulse in representing characteristics such as the time derivative and the energy content of lightning impulses. The 10/350 μs test current impulse better represents the integrated effects of the energy content of impulse component and long continuing current. A new waveform is required to be specified for testing the ability of protective devices to respond to the fast leading edges of subsequent strokes that may appear 100s of millisecond after the preceding stroke. The test voltage waveform 1.2/50 μs should also be modified to evaluate the response of protective devices for fast leading edges of induced voltage transients. A surge protective device that is tested for lightning transients may not be able to provide defense against other transients.
ELECTROMAGNETIC TRANSIENTS IN RADIO/MICROWAVE BANDS AND SURGE PROTECTION DEVICES
2010-09-10
PIER
Vol. 108, 81-99, 2010
download: 133
Efficient Solutions of Metamaterial Problems Using a Low-Frequency Multilevel Fast Multipole Algorithm
Ozgur Ergul Levent Gurel
We present fast and accurate solutions of electromagnetics problems involving realistic metamaterial structures using a lowfrequency multilevel fast multipole algorithm (LF-MLFMA). Accelerating iterative solutions using robust preconditioning techniques may not be sufficient to reduce the overall processing time when the ordinary high-frequency MLFMA is applied to metamaterial problems. The major bottleneck, i.e., the low-frequency breakdown, should be eliminated for efficient solutions. We show that the combination of an LF-MLFMA implementation based on the multipole expansion with the sparse-approximate-inverse preconditioner enables efficient and accurate analysis of realistic metamaterial structures. Using the robust LF-MLFMA implementation, we demonstrate how the transmission properties of metamaterial walls can be enhanced with randomlyoriented unit cells.
EFFICIENT SOLUTIONS OF METAMATERIAL PROBLEMS USING A LOW-FREQUENCY MULTILEVEL FAST MULTIPOLE ALGORITHM