Vol. 128
Latest Volume
All Volumes
PIER 176 [2023] PIER 175 [2022] PIER 174 [2022] PIER 173 [2022] PIER 172 [2021] PIER 171 [2021] PIER 170 [2021] PIER 169 [2020] PIER 168 [2020] PIER 167 [2020] PIER 166 [2019] PIER 165 [2019] PIER 164 [2019] PIER 163 [2018] PIER 162 [2018] PIER 161 [2018] PIER 160 [2017] PIER 159 [2017] PIER 158 [2017] PIER 157 [2016] PIER 156 [2016] PIER 155 [2016] PIER 154 [2015] PIER 153 [2015] PIER 152 [2015] PIER 151 [2015] PIER 150 [2015] PIER 149 [2014] PIER 148 [2014] PIER 147 [2014] PIER 146 [2014] PIER 145 [2014] PIER 144 [2014] PIER 143 [2013] PIER 142 [2013] PIER 141 [2013] PIER 140 [2013] PIER 139 [2013] PIER 138 [2013] PIER 137 [2013] PIER 136 [2013] PIER 135 [2013] PIER 134 [2013] PIER 133 [2013] PIER 132 [2012] PIER 131 [2012] PIER 130 [2012] PIER 129 [2012] PIER 128 [2012] PIER 127 [2012] PIER 126 [2012] PIER 125 [2012] PIER 124 [2012] PIER 123 [2012] PIER 122 [2012] PIER 121 [2011] PIER 120 [2011] PIER 119 [2011] PIER 118 [2011] PIER 117 [2011] PIER 116 [2011] PIER 115 [2011] PIER 114 [2011] PIER 113 [2011] PIER 112 [2011] PIER 111 [2011] PIER 110 [2010] PIER 109 [2010] PIER 108 [2010] PIER 107 [2010] PIER 106 [2010] PIER 105 [2010] PIER 104 [2010] PIER 103 [2010] PIER 102 [2010] PIER 101 [2010] PIER 100 [2010] PIER 99 [2009] PIER 98 [2009] PIER 97 [2009] PIER 96 [2009] PIER 95 [2009] PIER 94 [2009] PIER 93 [2009] PIER 92 [2009] PIER 91 [2009] PIER 90 [2009] PIER 89 [2009] PIER 88 [2008] PIER 87 [2008] PIER 86 [2008] PIER 85 [2008] PIER 84 [2008] PIER 83 [2008] PIER 82 [2008] PIER 81 [2008] PIER 80 [2008] PIER 79 [2008] PIER 78 [2008] PIER 77 [2007] PIER 76 [2007] PIER 75 [2007] PIER 74 [2007] PIER 73 [2007] PIER 72 [2007] PIER 71 [2007] PIER 70 [2007] PIER 69 [2007] PIER 68 [2007] PIER 67 [2007] PIER 66 [2006] PIER 65 [2006] PIER 64 [2006] PIER 63 [2006] PIER 62 [2006] PIER 61 [2006] PIER 60 [2006] PIER 59 [2006] PIER 58 [2006] PIER 57 [2006] PIER 56 [2006] PIER 55 [2005] PIER 54 [2005] PIER 53 [2005] PIER 52 [2005] PIER 51 [2005] PIER 50 [2005] PIER 49 [2004] PIER 48 [2004] PIER 47 [2004] PIER 46 [2004] PIER 45 [2004] PIER 44 [2004] PIER 43 [2003] PIER 42 [2003] PIER 41 [2003] PIER 40 [2003] PIER 39 [2003] PIER 38 [2002] PIER 37 [2002] PIER 36 [2002] PIER 35 [2002] PIER 34 [2001] PIER 33 [2001] PIER 32 [2001] PIER 31 [2001] PIER 30 [2001] PIER 29 [2000] PIER 28 [2000] PIER 27 [2000] PIER 26 [2000] PIER 25 [2000] PIER 24 [1999] PIER 23 [1999] PIER 22 [1999] PIER 21 [1999] PIER 20 [1998] PIER 19 [1998] PIER 18 [1998] PIER 17 [1997] PIER 16 [1997] PIER 15 [1997] PIER 14 [1996] PIER 13 [1996] PIER 12 [1996] PIER 11 [1995] PIER 10 [1995] PIER 09 [1994] PIER 08 [1994] PIER 07 [1993] PIER 06 [1992] PIER 05 [1991] PIER 04 [1991] PIER 03 [1990] PIER 02 [1990] PIER 01 [1989]
2012-06-11
PIER
Vol. 128, 539-555, 2012
download: 108
Scattering of Gaussian Beam by a Spheroidal Particle
Xianming Sun Haihua Wang Huayong Zhang
Gaussian beam scattering by a spheroidal particle is studied in detail. A theoretical procedure is given to expand an incident Gaussian beam in terms of spheroidal vector wave functions within the generalized Lorenz-Mie theory framework. Exact analytic solutions are obtained for an arbitrarily oriented spheroid with non-confocal dielectric coating. Normalized differential scattering cross sections are shown and discussed for three different cases of a dielectric spheroid, spheroid with a spherical inclusion and coated spheroid.
SCATTERING OF GAUSSIAN BEAM BY A SPHEROIDAL PARTICLE
2012-06-08
PIER
Vol. 128, 519-537, 2012
download: 118
Modified Cylindrical Holographic Algorithm for Three-Dimensional Millimeter-Wave Imaging
Bailing Ren Shiyong Li Hou-Jun Sun Weidong Hu 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
download: 129
Motion Compensation for Squint Mode Spotlight SAR Imaging Using Efficient 2D Interpolation
Sang-Hong Park Jong-Il Park 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
download: 120
Bistatic FMCW SAR Raw Signal Simulator for Extended Scenes
Yue Liu Yun-Kai Deng Robert Wang 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
download: 325
A Study on Millimeter-Wave Imaging of Concealed Objects: Application Using Back-Projection Algorithm
Sevket Demirci Harun Cetinkaya Enes Yigit Caner Ozdemir 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
download: 249
Development of a Broadband Horizontally Polarized Omnidirectional Planar Antenna and Its Array for Base Stations
Xu Lin Quan Rong-Lin Li Jian Ye Wang 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
download: 149
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 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
download: 116
Specific Absorption Rate Computations with a Nodal-Based Finite Element Formulation
Ruben Otin 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
download: 149
A Wideband Planar Monopole Antenna Array with Circular Polarized and Band-Notched Characteristics
Wang-Sang Lee Kyoung-Sub Oh 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
download: 122
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 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
download: 126
Path-Loss Prediction of Radio Wave Propagation in an Orchard by Using Modified UTD Method
Kittisak Phaebua Chuwong Phongcharoenpanich Monai Krairiksh 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
download: 132
Design of Low-Loss and Highly-Selective CMOS Active Bandpass Filter at k -Band
Sen Wang 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 P1 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 (P1 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
download: 146
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 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
download: 128
Adaptive Clutter Suppression for Airborne Random Pulse Repetition Interval Radar Based on Compressed Sensing
Zhen Liu Xizhang Wei 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
download: 139
Multilayer Model Formulation and Analysis of Radar Backscattering from Sea Ice
Mohan Dass Albert Yu Jen Lee Hong-Tat Ewe 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
download: 218
Finite Element Matrix Generation on a GPU
Adam Dziekonski Piotr Sypek Adam Lamecki 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
download: 141
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 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
download: 116
Stopband-Extended Balanced Filters Using Both λ/4 and λ/2 SIRs with Common-Mode Suppression and Improved Passband Selectivity
Shih-Cheng Lin 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 8fd0, where fd0 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
download: 102
Constrained Trilinear Decomposition with Application to Array Signal Processing
Xu Liu Ting Jiang Longxiang Yang 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
download: 116
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 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