PIER | PIER Journals

2012-06-08

PIER

Vol. 128, 519-537, 2012

doi:10.2528/PIER12041619

download: 571

Modified Cylindrical Holographic Algorithm for Three-Dimensional Millimeter-Wave Imaging

Bailing Ren, Shiyong Li, Hou-Jun Sun, Weidong Hu and Xin Lv

Millimeter-wave (MMW) imaging techniques have been developed for the detection of concealed weapons and plastic explosives carried on personnel at major transportation hubs and secure locations. The combination of frequency-modulated continuous-wave (FMCW) technology and MMW imaging techniques leads to wideband, compact, and cost-effective systems which are especially suitable for security detection. Cylindrical three-dimensional (3-D) imaging technique, with the ability of viewing multiple sides, is an extension of rectilinear 3-D imaging technique only viewing a single side. Due to the relatively long signal sweep time, the conventional stop-and-go approximation of the pulsed systems is not suitable for FMCW systems. Therefore, a 3-D backscattered signal model including the effects of the continuous motion within the signal duration time is developed for cylindrical imaging systems. Then, a modified cylindrical holographic algorithm, with motion compensation, is presented and demonstrated by means of numerical simulations.

MODIFIED CYLINDRICAL HOLOGRAPHIC ALGORITHM FOR THREE-DIMENSIONAL MILLIMETER-WAVE IMAGING

2012-06-06

PIER

Vol. 128, 503-518, 2012

doi:10.2528/PIER12040201

download: 964

Motion Compensation for Squint Mode Spotlight SAR Imaging Using Efficient 2D Interpolation

Sang-Hong Park, Jong-Il Park and Kyung-Tae Kim

In the squint mode airborne spotlight synthetic aperture radar system using the range migration algorithm (RMA), autofocus (AF) technique yields poor results due to the squint spreading of the point spread function (PSF) of a scatterer. Thus, two-dimensional (2D) interpolation is required to direct PSF blurring in cross-range direction, to improve the cross-range resolution ¢y and to remove the spatially-varying sidelobe. Because conventional 2D interpolation requires huge computation time and yields large computation errors, we propose an efficient 2D interpolation technique for squint-mode RMA composed of two 1D interpolations. Simulation results using the measured turbulence data show ¢y was improved considerably and PSF was successfully focused by the proposed method with a reduced computation time.

MOTION COMPENSATION FOR SQUINT MODE SPOTLIGHT SAR IMAGING USING EFFICIENT 2D INTERPOLATION

2012-06-06

PIER

Vol. 128, 479-502, 2012

doi:10.2528/PIER12041604

download: 805

Bistatic FMCW SAR Raw Signal Simulator for Extended Scenes

Yue Liu, Yun-Kai Deng, Robert Wang and Xiaoxue Jia

By mounting the transmitter and receiver of Frequency Modulated Continuous Wave (FMCW) Synthetic Aperture Radar (SAR) system on separate platforms, bistatic FMCW SAR offers more considerable capabilities, reliability and flexibility while maintaining the small size, low cost and agile reaction. The bistatic FMCW SAR raw signal simulator is highly required to quantitatively support the design of bistatic FMCW SAR, to help mission planning, test processing algorithms, and analyze jamming and noises. Bistatic FMCW SAR raw signal can be exactly simulated target-by-target in time domain but with extremely time and memory consuming, especially when extended scenes are considered. In this paper, bistatic FMCW SAR signal model and Bistatic Point Target Reference Spectrum (BPTRS) is proposed, based on which a raw signal simulator is developed in the 2-D frequency domain for the first time, where Chirp-Z Transform (CZT) is used to formulate the range migration terms. By taking advantage of Fast Fourier Transform (FFT), the proposed raw signal simulator highly reduces the computational load with respect to the time domain approach. The simulated raw data is verified by analyzing the corresponding images focused by Range Doppler Algorithm (RDA).

BISTATIC FMCW SAR RAW SIGNAL SIMULATOR FOR EXTENDED SCENES

2012-06-05

PIER

Vol. 128, 457-477, 2012

doi:10.2528/PIER12050210

download: 820

A Study on Millimeter-Wave Imaging of Concealed Objects: Application Using Back-Projection Algorithm

Sevket Demirci, Harun Cetinkaya, Enes Yigit, Caner Ozdemir and Alexey A. Vertiy

Millimeter-wave (MMW) imaging is a powerful tool for the detection of objects concealed under clothing. Several factors including different kinds of objects, variety of covering materials and their thickness, accurate imaging of near-field scattered data affect the success of detection. To practice with such considerations, this paper presents the two-dimensional (2D) images of different targets hidden under various fabric sheets. The W-band inverse synthetic aperture radar (ISAR) data of various target-covering situations are acquired and imaged by applying both the focusing operator based inversion algorithm and the spherical back-projection algorithm. Results of these algorithms are demonstrated and compared to each other to assess the performance of the MMW imaging in detecting the concealed objects of both metallic and dielectric types.

A STUDY ON MILLIMETER-WAVE IMAGING OF CONCEALED OBJECTS: APPLICATION USING BACK-PROJECTION ALGORITHM

2012-06-02

PIER

Vol. 128, 441-456, 2012

doi:10.2528/PIER12042405

download: 1134

Development of a Broadband Horizontally Polarized Omnidirectional Planar Antenna and Its Array for Base Stations

Xu Lin Quan, Rong-Lin Li, Jian Ye Wang and Yue Hui Cui

A novel broadband horizontally polarized (HP) omnidirectional planar antenna is developed for mobile communications. The proposed antenna consists of four printed arc dipoles that form a circular loop for HP omnidirectional radiation. A broadband feeding network which includes four broadband baluns and an impedance matching circuit is designed to excite the four arc dipoles. An eight-element linear antenna array is developed for 2G/3G base stations. A broadband power divider is used to feed the antenna array. Experimental results show that the HP omnidirectional antenna element has a bandwidth of 31% (1.66-2.27 GHz) while its array has a bandwidth of 34% (1.67-2.35 GHz) and an omnidirectional antenna gain of ~8 dBi. Both of the antenna element and its array have good omnidirectivity over the 10-dB return loss bandwidth. Simulated and measured results for the antenna element and its array are presented.

DEVELOPMENT OF A BROADBAND HORIZONTALLY POLARIZED OMNIDIRECTIONAL PLANAR ANTENNA AND ITS ARRAY FOR BASE STATIONS

2012-06-02

PIER

Vol. 128, 419-440, 2012

doi:10.2528/PIER12041207

download: 744

An Active Ring Slot with RF MEMS Switchable Radial Stubs for Reconfigurable Frequency Selective Surface Applications

Rosalba Martinez-Lopez, Jorge Rodriguez-Cuevas, Alexander E. Martynyuk and Jose I. Martinez-Lopez

An active ring slot resonator loaded by switchable radial stubs is investigated. It is shown that this element can be used as the unit cell of a switchable reconfigurable frequency selective surface (RFSS). Equivalent circuit and full-wave mathematical models are obtained to evaluate the reflection characteristics of the RFSS based on this element. The possibility to obtain different resonant transmission frequencies is discussed. The mathematical model developed is used to design an X band RFSS capable of obtaining resonant frequencies at 9.65, 10.28, 10.83 and 12.05 GHz. Commercially available RF MEMS switches are used to evaluate the effect of the off-state capacitances over the response of the periodic structure. To validate the numerical simulation results, different active and passive diaphragms were designed, fabricated, and tested using the waveguide simulator. A good agreement between numerical and measured results was found.

AN ACTIVE RING SLOT WITH RF MEMS SWITCHABLE RADIAL STUBS FOR RECONFIGURABLE FREQUENCY SELECTIVE SURFACE APPLICATIONS

2012-06-02

PIER

Vol. 128, 399-418, 2012

doi:10.2528/PIER12041105

download: 689

Specific Absorption Rate Computations with a Nodal-Based Finite Element Formulation

Ruben Otin and Herve Gromat

The aim of this work is to asses the performance of a nodal-based finite element formulation when applied to the computation of specific absorption rate (SAR) problems. This formulation solves numerically the regularized Maxwell equations using nodal elements and, in principle, it offers several advantages: It provides spurious-free solutions and well-conditioned matrices without the need of Lagrange multipliers or scalar potentials. Its integral representation is well-suited for hybridization with integral numerical techniques because of a low-order singular kernel. Also, the nodal approximation of the electromagnetic problem is easier to couple to a thermal finite element problem which usually also employs nodal elements. But, on the other hand, we need to take special care of the points of the domain where the field is singular to obtain accurate solutions. In this paper, we show the impact of the singularities on the performance of the proposed finite element formulation and how its good features are affected when solving real-life SAR problems.₁

SPECIFIC ABSORPTION RATE COMPUTATIONS WITH A NODAL-BASED FINITE ELEMENT FORMULATION

2012-06-02

PIER

Vol. 128, 381-398, 2012

doi:10.2528/PIER12040307

download: 622

A Wideband Planar Monopole Antenna Array with Circular Polarized and Band-Notched Characteristics

Wang-Sang Lee, Kyoung-Sub Oh and Jong-Won Yu

A wideband circular polarized planar monopole antenna array (PMAA) that employs dual band-notched characteristics is presented in this paper. The proposed antenna array is formed by four pinwheel-shaped folded planar monopole antennas (PMAs) in order to improve the performance of circular polarization and high directivity. Also, it achieves low-profile, smallsized structure. The attractive characteristics of the proposed PMAA are a wide impedance bandwidth of 87.3% (1 GHz to 2.55 GHz), the 3 dB axialratio (AR) bandwidth of 92.3% (1.05 GHz to 2.85 GHz) excluding dual notch bands, the total bandwidth of 35% (1.8 GHz to 2.55 GHz), and the maximum gain of 8.24 dBic within the total bandwidh. Moreover, in order to generate dual band-notched characteristics in a circular polarized antenna, a folded PMAA with multiple U radiators and inverted W slots is proposed.

A WIDEBAND PLANAR MONOPOLE ANTENNA ARRAY WITH CIRCULAR POLARIZED AND BAND-NOTCHED CHARACTERISTICS

2012-06-02

PIER

Vol. 128, 365-380, 2012

doi:10.2528/PIER12040802

download: 574

Application of a Useful Uncertainty Analysis as a Metric Tool for Assessing the Performance of Electromagnetic Properties Retrieval Methods of Bianisotropic Metamaterials

Ugur Cem Hasar, Joaquim Jose Barroso, Mehmet Ertugrul, Cumali Sabah and Bulent Cavusoglu

We applied a useful uncertainty model, ignored in most metamaterials retrieval studies, to monitor the accuracy of retrieved electromagnetic properties of bianisotropic metamaterial (MM) slabs composed of split-ring resonators and cut wires. Two different MM slab structures are considered to make the analysis complete. As uncertaintymaking factors, we took into consideration of uncertainties in scattering (S-) parameters of bianisotropic MM slabs as well as the length of these slabs. The applied uncertainty model is based upon considering the effect of minute change (differential) in uncertainty factors on the retrieved electromagnetic properties of bianisotropic MM slabs. The significant results concluded from the analysis are: 1) any abrupt changes in the phase of S-parameters of bianisotropic MM slabs remarkably influence the retrieved electromagnetic properties; 2) any small-scale loss (i.e., the loss of the substrate) in the bianisotropic MM slabs improves the accuracy of the retrieved electromagnetic properties of these slabs; and 3) precise knowledge of bianisotropic MM slab lengths are required for correct analysis of exotic properties of these slabs. The presented uncertainty analysis can be utilized as a metric tool for evaluating various retrieval methods of MM slabs in the literature.

APPLICATION OF A USEFUL UNCERTAINTY ANALYSIS AS A METRIC TOOL FOR ASSESSING THE PERFORMANCE OF ELECTROMAGNETIC PROPERTIES RETRIEVAL METHODS OF BIANISOTROPIC METAMATERIALS

2012-06-02

PIER

Vol. 128, 347-363, 2012

doi:10.2528/PIER12040106

download: 546

Path-Loss Prediction of Radio Wave Propagation in an Orchard by Using Modified UTD Method

Kittisak Phaebua, Chuwong Phongcharoenpanich, Monai Krairiksh and Titipong Lertwiriyaprapa

The proposed theoretical path-loss prediction procedure and measured results of radio wave propagation in an orchard environment are presented. The wireless sensor network (WSN) in a Durian orchard is primarily chosen to be an example of this study. The three-dimensional (3-D) modified uniform geometrical theory of diffraction (UTD) for curved impedance surface is employed for theoretical path-loss prediction in this paper. The orchard scenario is modeled by using canonical geometries such as a dielectric flat surface and cylindrical structures with an impedance surface to respectively represent ground and trees. Moreover, since the wireless sensor node is attached to the outside peel of a hanging durian fruit, the fruit partially acts as a wireless sensor node. Therefore, to obtain greater accuracy in the source radiation pattern, the Gaussian beam (GB) expansion via the CSP technique is used for source modeling. The path loss prediction from the proposed numerical procedure and the measured results are in good agreement. The proposed numerical procedure to calculate the path loss from actual scenario of the orchard is useful for network planning such as the pre-harvesting WSN system and other orchard scenarios.

PATH-LOSS PREDICTION OF RADIO WAVE PROPAGATION IN AN ORCHARD BY USING MODIFIED UTD METHOD

2012-06-01

PIER

Vol. 128, 331-346, 2012

doi:10.2528/PIER12031301

download: 933

Design of Low-Loss and Highly-Selective CMOS Active Bandpass Filter at k-Band

Sen Wang and Bo-Zong Huang

In this paper, a second-order Chebyshev active bandpass filter (BPF) with three finite transmission zeros is presented. The filter utilizes a tapped-inductor feedback technique to compensate resistive losses of on-chip inductors, and a shunt-feedback inductor between input and output ports to achieve the transmission zeros. Moreover, one transmission zero is in the lower stopband, and two transmission zeros are in the upper stopband, thus improving the selectivity of the filter significantly. The filter is designed and fabricated in a standard 0.18-μm CMOS technology with a chip area of 0.57 mm×0.65 mm including all testing pads. The circuit draws 6 mA from a 0.7-V supply voltage. Additionally, the filter achieves a 1.65-dB insertion loss and 13.2-dB return loss with a 17% 3-dB bandwidth at 23.5 GHz. The measured NF and input P_{1 dB} is 6.7 dB and -3.5 dBm. The rejection levels at the transmission zeros are greater than 15.2 dB. Finally, the large-signal characterizations are also investigated by the 1-dB compression point (P_{1 dB}) of the filter.

DESIGN OF LOW-LOSS AND HIGHLY-SELECTIVE CMOS ACTIVE BANDPASS FILTER AT K-BAND

2012-06-01

PIER

Vol. 128, 313-329, 2012

doi:10.2528/PIER12022809

download: 536

Printed Wideband Antenna with Chip-Capacitor-Loaded Inductive Strip for LTE/GSM/UMTS WWAN Wireless USB Dongle Applications

Yong-Ling Ban, Jin-Hua Chen, Si-Cheng Sun, Joshua Le-Wei Li and Jin-Hong Guo

This paper proposes a planar printed wideband antenna for eight-band LTE/GSM/UMTS WWAN wireless USB dongle applications. An inductive shorted strip with a chip capacitor loaded is employed in order to improve the characteristics of small-size terminal antennas which usually have a narrow band over the LTE700/GSM850/900 (698-960 MHz) operation. While the desired upper band is mainly realized by the rectangular radiating patch, covering DCS1800/PCS1900/UMTS2100/LTE2300/2500 (1710-2690 MHz) band. Easily printed on a 0.8-mm thick FR4 dielectric substrate of size 20×70 mm², the proposed antenna structure occupies a compact size of 20×19 mm². Then the proposed design can be attached to laptop computer by the USB interface. Good radiation efficiency and antenna gain for frequencies over the desired operating bands is obtained. Detailed design considerations of the proposed antenna are described, and both experimental and simulation results are also presented and discussed.

PRINTED WIDEBAND ANTENNA WITH CHIP-CAPACITOR-LOADED INDUCTIVE STRIP FOR LTE/GSM/UMTS WWAN WIRELESS USB DONGLE APPLICATIONS

2012-06-01

PIER

Vol. 128, 291-311, 2012

doi:10.2528/PIER12022001

download: 849

Adaptive Clutter Suppression for Airborne Random Pulse Repetition Interval Radar Based on Compressed Sensing

Zhen Liu, Xizhang Wei and Xiang Li

We present an adaptive clutter suppression method for airborne random pulse repetition interval radar by using prior knowledge of clutter boundary in Doppler spectrum. In this method, by exploiting the intrinsic sparsity, compressed sensing based on iterative grid optimization (CS-IGO) is applied to directly recover the clutter spectrum with only the test range cell instead of nonhomogeneous training data from adjacent range cells. Since the sensing matrix and clutter spectrum obtained by CS-IGO are well adapted to the data, the prewhitening filter can be effectively obtained to cancel the mainlobe clutter. Further, the clutter residue can be suppressed by the iterative reweighted l1 minimization to enhance the target response. Simulation results show that the approach is capable of effective suppression of clutter and precise recovery of targets' unambiguous spectrum, offering a high performance of output signal to clutter and noise ratio.

ADAPTIVE CLUTTER SUPPRESSION FOR AIRBORNE RANDOM PULSE REPETITION INTERVAL RADAR BASED ON COMPRESSED SENSING

2012-06-01

PIER

Vol. 128, 267-290, 2012

doi:10.2528/PIER12020205

download: 749

Multilayer Model Formulation and Analysis of Radar Backscattering from Sea Ice

Mohan Dass Albert, Yu Jen Lee, Hong-Tat Ewe and Hean-Teik Chuah

The Antarctic continent is an extremely suitable environment for the application of remote sensing technology as it is one of the harshest places on earth. Satellite images of the terrain can be properly interpreted with thorough understanding of the microwave scattering process. The proper model development for backscattering can be used to test the assumptions on the dominating scattering mechanisms. In this paper, the formulation and analysis of a multilayer model used for sea ice terrain is presented. The multilayer model is extended from the previous single layer model developed based on the Radiative Transfer theory. The Radiative Transfer theory is chosen because of its simplicity and ability to incorporate multiple scattering effects into the calculations. The propagation of energy in the medium is characterized by the extinction and phase matrices. The model also incorporates the Dense Medium Phase and Amplitude Correction Theory (DM-PACT) where it takes into account the close spacing effect among scatterers. The air-snow interface, snowsea ice interface and sea ice-ocean interface are modelled using the Integral Equation Method (IEM). The simulated backscattering coefficients for co- and crosspolarization using the developed model for 1 GHz and 10 GHz are presented. In addition, the simulated backscattering coefficients from the multilayer model were compared with the measurement results obtained from Coordinated Eastern Artic Experiment (CEAREX) (Grenfell, 1992) and with the results obtained from the model developed by Saibun Tjuatja (based on the Matrix Doubling method) in 1992.

MULTILAYER MODEL FORMULATION AND ANALYSIS OF RADAR BACKSCATTERING FROM SEA ICE

2012-05-31

PIER

Vol. 128, 249-265, 2012

doi:10.2528/PIER12040301

download: 841

Finite Element Matrix Generation on a GPU

Adam Dziekonski, Piotr Sypek, Adam Lamecki and Michal Mrozowski

This paper presents an efficient technique for fast generation of sparse systems of linear equations arising in computational electromagnetics in a finite element method using higher order elements. The proposed approach employs a graphics processing unit (GPU) for both numerical integration and matrix assembly. The performance results obtained on a test platform consisting of a Fermi GPU (1x Tesla C2075) and a CPU (2x twelve-core Opterons), indicate that the GPU implementation of the matrix generation allows one to achieve speedups by a factor of 81 and 19 over the optimized single-and multi-threaded CPU-only implementations, respectively.

FINITE ELEMENT MATRIX GENERATION ON A GPU

2012-05-30

PIER

Vol. 128, 229-248, 2012

doi:10.2528/PIER12020108

download: 732

Improved Thermal Ablation Efficacy Using Magnetic Nanoparticles: A Study in Tumor Phantoms

Sonia García-Jimeno, Rocío Ortega-Palacios, Mario Francisco Cepeda-Rubio, Arturo Vera, Lorenzo Leija-Salas and Joan Estelrich

Magnetic heating used for inducing hyperthermia and thermal ablation is particularly promising in the treatment of cancer provided that the therapeutic temperature is kept constant during the treatment time throughout the targeted tissue and the healthy surrounding tissues are maintained at a safe temperature. The present study shows the temperature increment produced by different concentrations of magnetic nanoparticles (ferrofluid and magnetoliposomes) inside a phantom, after irradiating tissue-mimicking materials (phantoms) with a minimally invasive coaxial antenna working at a frequency of 2.45 GHz. This frequency was chosen because maximum dielectric loss of water molecules begins at 2.4 GHz and because this is an ISM (industrial, scientific and medical) frequency. Temperature sensors were placed inside and outside the tumor phantom to assess the focusing effect of heat produced by nanoparticles. Results have shown that the temperature increments depend on the nanoparticles concentration. In this way, a temperature increment of more than 56 ºC was obtained with a ferrofluid concentration of 13.2 mg/mL, whereas the increment in the reference phantom was only of ≈ 21 ºC. Concerning the magnetoliposomes, the temperature achieved was similar to that obtained with the ferrofluid but at a lesser concentration of nanoparticles. These results demonstrate that it is possible to achieve higher temperatures and to focus energy where the nanoparticles are located.

IMPROVED THERMAL ABLATION EFFICACY USING MAGNETIC NANOPARTICLES: A STUDY IN TUMOR PHANTOMS

2012-05-30

PIER

Vol. 128, 215-228, 2012

doi:10.2528/PIER12041403

download: 591

Stopband-Extended Balanced Filters Using Both λ/4 and λ/2 SIRs with Common-Mode Suppression and Improved Passband Selectivity

Shih-Cheng Lin and Chong-You Yeh

Benefitting from the simultaneous utilization of quarter-wave (λ/4) and half-wave (λ/2) microstrip resonators, a via-free balanced bandpass filter (BPF) with direct-coupled scheme is presented in this study. In the beginning, a single-ended filter with transmission zeros (TZs) is newly proposed and the mechanism of creating two TZs around the passband without necessitating cross couplings is adopted. The TZs can be made structure-inherent based on the coexisted out-of-phase couplings among a coupled-resonator pair. On the foundation of the presented single-ended filter, a balanced filter featuring extended differential-mode (DM) stopband, good common-mode (CM) suppression, and improved passband selectivity has been designed and implemented. The DM stopband extension is achieved by misaligning the higher-order harmonic frequencies of each resonator in the DM bisected circuit while the CM suppression is accomplished by both harmonic misalignment and careful designed coupled structure in the CM bisected circuit. Eventually, a demonstrated balanced filter centering at 1.5 GHz possesses DM stopband extended up to 8f^d₀, where f^d₀ denotes the DM operation frequency, and its CM rejection ratio (CMRR) within DM passband better than 51.9 dB is attained. For measurement convenience, the DM characterizations have been accomplished by 2-port network analyzer with simple rat-race baluns and are found relatively accurate within the -15dB bandwidth of the utilized baluns.

STOPBAND-EXTENDED BALANCED FILTERS USING BOTH λ/4 AND λ/2 SIRS WITH COMMON-MODE SUPPRESSION AND IMPROVED PASSBAND SELECTIVITY

2012-05-29

PIER

Vol. 128, 195-214, 2012

doi:10.2528/PIER12031410

download: 507

Constrained Trilinear Decomposition with Application to Array Signal Processing

Xu Liu, Ting Jiang, Longxiang Yang and Hong-Bo Zhu

This paper links the constrained trilinear tensor model into array signal processing. The structure properties of baseband signal, such as the Constant-Modulus (CM) and Finite Alphabet (FA) structures which are already known in the receiving array, are exploited in trilinear decomposition. Two novel algorithms for constrained trilinear decomposition are proposed and applied to array signal processing. The distinguishing features of the proposed model and algorithms compared to the traditional trilinear signal processing methods are: (i)~the proposed model has a better performance and lower computation complexity. (ii)~it can still work well even if degeneracy of factors are involved in the data model, which is not valid in traditional algorithms. Simulation results are presented to illustrate the application of the constrained trilinear decomposition to array signal processing and evaluate the performance of the proposed algorithms in DOAs estimation.

CONSTRAINED TRILINEAR DECOMPOSITION WITH APPLICATION TO ARRAY SIGNAL PROCESSING

2012-05-27

PIER

Vol. 128, 171-193, 2012

doi:10.2528/PIER12011502

download: 642

Novel Pre-Processing Techniques for Coherence Improving in Along-Track Dual-Channel Low Frequency SAR

Chongyi Fan, Xiao-Tao Huang, Tian Jin, Jun-Gang Yang and Dao Xiang An

The coherence between the complex image pair from two channels is important for improving the capability of along-track interferometry (ATI) processing in synthetic aperture radar (SAR) ground moving target indication (GMTI). The along-track dual-channel low frequency SAR can be easily influenced by not only mismatch errors of the image pair but also the radio frequency interference (RFI). RFI has great impacts on the joint probability density function (PDF) of magnitude and phase in the interferometric image. However, little work has been done to investigate the coherence improvement under RFI. This study develops an algorithm to improve the coherence of the image pair for along-track dual-channel low frequency SAR, which can be used by ATI. After analyzing RFI imaging in detail, it is proposed that the along-track interferometric image in the range frequency and cross-range slow time domain can be used to detect RFI. Median filters are proposed to further suppress RFI. This suppression has the same implementations to the image pair without heavy computation load. Considering RFI suppression and mismatch errors compensation, a pre-processing flow is proposed to achieve high coherence of the interferometric image in low frequency SAR. It is shown that the coherence of the complex image pair can be improved greatly by using this pre-processing flow. The effectiveness of this algorithm is demonstrated with real data acquired by an airborne along-track dual-channel P-band SAR GMTI system.

NOVEL PRE-PROCESSING TECHNIQUES FOR COHERENCE IMPROVING IN ALONG-TRACK DUAL-CHANNEL LOW FREQUENCY SAR

2012-05-27

PIER

Vol. 128, 153-170, 2012

doi:10.2528/PIER12032306

download: 624

A Hybrid Implicit-Explicit Spectral FDTD Scheme for Oblique Incidence Problems on Periodic Structures

Yunfei Mao, Bin Chen, Hao-Quan Liu, Jing-Long Xia and Ji-Zhen Tang

This paper combines a hybrid implicit-explicit (HIE) method with spectral finite-difference time-domain (SFDTD) method for solving periodic structures at oblique incidence, resulting in a HIE-SFDTD method. The new method has the advantages of both HIE-FDTD and SFDTD methods, not only making the stability condition weaker, but also solving the oblique incident wave on periodic structures. Because the stability condition is determined only by two space discretizations in this method, it is extremely useful for periodic problems with very fine structures in one direction. The method replaces the conventional single-angle incident wave with a constant transverse wave-number (CTW) wave, so the fields have no delay in the transverse plane, as a result, the periodic boundary condition (PBC) can be implemented easily for both normal and oblique incident waves. Compared with the ADI-SFDTD method it only needs to solve two untridiagonal matrices when the PBC is applied to, other four equations can be updated directly, while four untridiagonal matrices, two tridiagonal matrices, and six explicit equations should be solved in the ADI-SFDTD method. Numerical examples are presented to demonstrate the efficiency and accuracy of the proposed algorithm. Results show the new algorithm has better accuracy and higher efficiency than that of the ADI-SFDTD method, especially for large time step sizes. The CPU running time for this method can be reduced to about 45% of the ADI-SFDTD method.

A HYBRID IMPLICIT-EXPLICIT SPECTRAL FDTD SCHEME FOR OBLIQUE INCIDENCE PROBLEMS ON PERIODIC STRUCTURES

2012-05-23

PIER

Vol. 128, 137-151, 2012

doi:10.2528/PIER12032210

download: 594

Performance Analysis of the Scenario-Based Construction Method for Real Target ISAR Recognition

Sang-Hong Park, Joon-Ho Lee and Kyung-Tae Kim

Due to the difficulty in estimating the 2D image plane of the inverse synthetic aperture radar (ISAR) image, we recently proposed a new paradigm to construct the training database based on the flight scenario. However, because the flight condition for the training and the test data was identical, much more study is required for this method to be applied to the real ISAR scenario. This paper presents a study on the factor that can affect the applicability of scenario-based method to the real target ISAR recognition. Simulation results using five scatterer models show that accurate measurement of flight direction and aspect angle variation are required and enough bandwidth larger than 200 MHz should be guaranteed for the successful classification.

PERFORMANCE ANALYSIS OF THE SCENARIO-BASED CONSTRUCTION METHOD FOR REAL TARGET ISAR RECOGNITION

2012-05-22

PIER

Vol. 128, 121-136, 2012

doi:10.2528/PIER12030105

download: 606

Analysis of Materials Effects on Radio Frequency Electromagnetic Fields in Human Head

Mohammad Tariqul Islam, Hafizah Zainool Abidin, Mohammad Rashed Iqbal Faruque and Norbahiah Misran

In this paper, we propose to study the variability of specific absorption rate (SAR) of a human head due to different materials in the vicinity of the handset. We include the effects of the human hand, handset chassis and additional conductive material particularly hand-ring jewelry. A finite-difference time-Domain (FDTD) method was used to analyze different positions of the conductive ring materials within the hand model. Furthermore, the impact of this material on the performance of an antenna was considered in this study. We found that including a hand model leads to a significant reduction in SAR. The hand influences not only SAR distribution but also antenna performance. Moreover, adding conductive materials to the hand results in increases in the local SAR values of the head model. The results suggest that the hand model is important in SAR evaluation and that having an additional conductive material on the hand may vary the amount of electromagnetic (EM) energy absorption depending on the position of the material.

ANALYSIS OF MATERIALS EFFECTS ON RADIO FREQUENCY ELECTROMAGNETIC FIELDS IN HUMAN HEAD

2012-05-18

PIER

Vol. 128, 105-120, 2012

doi:10.2528/PIER12041818

download: 765

Analysis of Scattering with Multi-Slotted Cylinder with Thickness: TM Case

Wang-Sang Lee, Han-Lim Lee, Hyeong-Seok Jang, Hyun-Sung Tae and Jong-Won Yu

An exact series solution for radiation and scattering of the dielectric-loaded multi-slotted cylinder with thickness is formulated by using radial mode matching technique. The radiated and guided fields are represented in terms of an infinite series of radial modes. By applying the appropriate boundary conditions, the coefficients of radiated and guided fields are obtained. The behaviors of resonance features are characterized for variation in frequencies, source positions, slot thickness, and dielectric coating properties.

ANALYSIS OF SCATTERING WITH MULTI-SLOTTED CYLINDER WITH THICKNESS: TM CASE

2012-05-18

PIER

Vol. 128, 91-103, 2012

doi:10.2528/PIER12040306

download: 546

Multi-Refraction with Same Polarization State in Two Dimensional Triangular Photonic Crystals

Guoyan Dong, Ji Zhou, Xiulun Yang and Xiangfeng Meng

Multi-refraction effects with one polarization in a two-dimensional triangular photonic crystal (PhC) were systematically studied by theoretical analysis and numerical simulation. The more complicated refraction behaviors can be excited in the higher band regions based on the intricate undulation of one band or the overlap of different bands. A novel non-handedness effect is proposed for the first time with group velocity perpendicular to phase velocity. Furthermore, triple refraction phenomena and special collimation effects of symmetrical positive-negative refraction with the loose incident conditions have been found in different band regions of this PhC. These unique features will provide us with more understanding of electromagnetic wave propagation in PhCs and give important guideline for the design of new type optical device.

MULTI-REFRACTION WITH SAME POLARIZATION STATE IN TWO DIMENSIONAL TRIANGULAR PHOTONIC CRYSTALS

2012-05-18

PIER

Vol. 128, 75-90, 2012

doi:10.2528/PIER11101408

download: 758

Study of Magnetic Gravity Compensator Topologies Using an Abstraction in the Analytical Interaction Equations

Jeroen L. G. Janssen, Johannes J. H. Paulides and Elena A. Lomonova

This paper identifies an abstraction that is found in the equations that describe the 3D interaction between cuboidal permanent magnets and applies this to the magnetic design of a gravity compensator. It shows how the force between magnets and its position-sensitivity, important design parameters for magnetically levitated 6-DoF gravity compensators, may be translated into the magnetic domain and verifies this with 3D analytical models. With this information, a number of basic gravity compensator topologies is derived. These topologies are subsequently investigated in more detail, with specific focus on combining a high force with low position sensitivity.

STUDY OF MAGNETIC GRAVITY COMPENSATOR TOPOLOGIES USING AN ABSTRACTION IN THE ANALYTICAL INTERACTION EQUATIONS

2012-05-15

PIER

Vol. 128, 55-74, 2012

doi:10.2528/PIER12041006

download: 603

Symmetric Inverse-Based Multilevel Ilu Preconditioning for Solving Dense Complex Non-Hermitian Systems in Electromagnetics

Bruno Carpentieri and Matthias Bollhöfer

Boundary element discretizations of exterior Maxwell problems lead to dense complex non-Hermitian systems of linear equations that are difficult to solve from a linear algebra point of view. We show that the recently developed class of inverse-based multilevel incomplete LU factorization has very good potential to precondition these systems effectively. This family of algorithms can produce numerically stable factorizations and exploits efficiently the possible symmetry of the underlying integral formulation. The results are highlighted by calculating the radar-cross-section of a full aircraft, and by a numerical comparison against other standard preconditioners.

SYMMETRIC INVERSE-BASED MULTILEVEL ILU PRECONDITIONING FOR SOLVING DENSE COMPLEX NON-HERMITIAN SYSTEMS IN ELECTROMAGNETICS

2012-05-15

PIER

Vol. 128, 35-53, 2012

doi:10.2528/PIER12041908

download: 558

Surface Plasmon Properties of Hollow Auag Alloyed Triangular Nanoboxes and Its Applications in Sers Imaging and Potential Drug Delivery

XinWei Liu, Jiao Lin, Tian Feng Jiang, Zhen Feng Zhu, Qiuqiang Zhan, Jun Qian and Sailing He

We successfully synthesized hollow AuAg alloyed triangular nanoboxes (TNBs) with localized surface plasmon resonances (LSPR) spectra position from visible to NIR region. We then study the surface plasmon properties of AuAg alloyed TNBs and explore their application in surface enhanced Raman scattering (SERS) imaging. We also investigated the laser induced near-field ablation of TNBs, which have the potentials of drug delivery for cancer treatment. Finite Difference Time Domain (FDTD) method is used to calculate electromagnetic fields induced by optical excitation of LSPR of AuAg alloyed TNBs for the first time. The calculated results are proved through in-vivo SERS imaging by three types of SERS tags based on TNBs. Furthermore, the unique hollow structure of TNBs may facilitate direct encapsulation of anticancer drugs, without any surface coatings. The femtosecond laser near-field ablation experiment is studied as one possible method to release the drug encapsulated inside the hollow structure. These studies show that the nanostructures are easy to break down and promising as a nanodevice model for controlled drug delivery.

SURFACE PLASMON PROPERTIES OF HOLLOW AUAG ALLOYED TRIANGULAR NANOBOXES AND ITS APPLICATIONS IN SERS IMAGING AND POTENTIAL DRUG DELIVERY

2012-05-14

PIER

Vol. 128, 19-34, 2012

doi:10.2528/PIER12041205

download: 908

Switchable Distance-Based Impedance Matching Networks for a Tunable HF System

Wang-Sang Lee, Han-Lim Lee, Kyoung-Sub Oh and Jong-Won Yu

Distance-based impedance matching networks for a tunable high frequency (HF) system are presented in this paper for the improved performance. The transmitting antenna for a HF system with an operating frequency of 13.56 MHz consists of a two-turn loop and three channel impedance matching networks corresponding to the distance of the receiving antenna. Each impedance matching network maximizes the system performance such as uniform power efficiency and reading range at specific distance between a transmitting and a receiving antenna. By controlling the distance-based matching networks, the power efficiency of the proposed antenna improves by up to 89% compared to the conventional antenna system with the fixed matching (FM) condition for distances, and the reliable reading range according to the impedance matching conditions is also increased. The proposed technique is applicable for near field communication (NFC), radio frequency identification (RFID), or wireless power transfer (WPT) devices.

SWITCHABLE DISTANCE-BASED IMPEDANCE MATCHING NETWORKS FOR A TUNABLE HF SYSTEM

2012-05-12

PIER

Vol. 128, 1-17, 2012

doi:10.2528/PIER12031505

download: 723

Comprehensive Analysis of Lenz Effect on the Artificial Heart Valves During Magnetic Resonance Imaging

Laleh Golestanirad, Emad Dlala, Graham Wright, Juan Mosig and Simon J. Graham

This work presents results of a comprehensive analysis of the Lenz effect due to motion of artificial heart valves during magnetic resonance imaging. The interaction of rotating metallic heart valves with magnetic fields is studied by performing a time-domain analysis of the corresponding electromagnetic problem. We applied the finite element method (FEM) to solve the T-Ω formulation of Maxwell equations in two cases: first, for metallic disks located in the high intensity homogenous field of the magnet iso-center, and second, disks located in the non-uniform fringe field of the bore entrance. We showed that for valves with full solid disks (such as Starr-Edwards 6500) located in the magnet iso-center, the magnitude of adverse forces can be comparable to the forces applied by the beating heart. However, for rings which consist of multiply connected conductive regions, skin effect and proximity effect counteract, which leads to a diminished magnetic force. Results of this study show that mechanical heart valves with strengthening rings {may} be considered safe even under ultra-high imaging conditions with field intensities as high as 10 T. However, heart valves with full conducting disks should be considered as a contraindication to MR imaging.