Vol. 119
Latest Volume
All Volumes
PIER 179 [2024] PIER 178 [2023] PIER 177 [2023] 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]
2011-08-27
PIER
Vol. 119, 497-511, 2011
download: 213
High Selectivity and Controllability of a Parallel-Plate Component with a Filled Rectangular Ridge
Constantinos Valagiannopoulos
Achieving and controlling highly selective response in an electronic component could be particularly beneficial for numerous practical applications. In this work, we consider a simple configuration of a discontinuous parallel-plate waveguide with a narrow rectangular ridge filled with axially anisotropic material. The formulated boundary value problem is rigorously treated with help from mode matching technique. The variables with respect to which the device exhibits highly selective behavior and the parameters through which the regulation of sharp variations becomes possible, have been identified. Several graphs demonstrating these properties are analyzed and discussed.
HIGH SELECTIVITY AND CONTROLLABILITY OF A PARALLEL-PLATE COMPONENT WITH A FILLED RECTANGULAR RIDGE
2011-08-19
PIER
Vol. 119, 477-495, 2011
download: 281
A Cylindrical Shaped-Reflector Antenna with a Linear Feed Array for Shaping Complex Beam Patterns
Soon Young Eom , Young-Bae Jung , S. A. Ganin and A. V. Shishlov
In this paper, we present a cylindrical shaped-reflector antenna which is spatially fed by an off-set linear feed array to form complex beam patterns. The linear feed array consists of twelve microstrip patch elements and forms a flat-topped beam pattern with a beam-width of ±45° in the azimuth plane. The vertical curve on the cylindrical reflector with the linear feed array is shaped to form a cosecant beam pattern within the range of -5° to -25° in the elevation plane. By using the proposed design procedure to form complex beam patterns, a hybrid antenna with a cylindrical reflector aperture of 140 cm x 50 is designed to be operated within the IMT 2000 service band, and a prototype antenna is also fabricated. Its electrical performance is measured and compared with simulation results.
A CYLINDRICAL SHAPED-REFLECTOR ANTENNA WITH A LINEAR FEED ARRAY FOR SHAPING COMPLEX BEAM PATTERNS
2011-08-19
PIER
Vol. 119, 461-476, 2011
download: 245
Very Miniature Dual-Band and Dual-Mode Bandpass Filter Designs on an Integrated Passive Device Chip
Chien-Hsun Chen , Chih-Syuan Shih , Tzyy-Sheng Horng and Sung-Mao Wu
This work presents extremely compact dual-mode and dual-band bandpass filter designs based on dual-resonance composite resonators developed by using integrated passive device (IPD) technology on a glass substrate. A dual-mode bandpass filter is also devised using a symmetric composite resonator with a perturbation element of grounding inductor to determine the filter bandwidth. Additionally, a feedback capacitive coupling path on the proposed dual-mode filter is implemented to produce three transmission-zero frequencies in the stopband. Furthermore, the proposed dual-band bandpass filter is designed in a high-density wiring transformer configuration with magnetic and electric mixed coupling. In addition to individually determining the fractional bandwidth of dual passbands, the magnetic and electric mixed coupling provides multiple transmission zeros to enhance the isolation between the two passbands and greatly improve the stopband rejection.
VERY MINIATURE DUAL-BAND AND DUAL-MODE BANDPASS FILTER DESIGNS ON AN INTEGRATED PASSIVE DEVICE CHIP
2011-08-18
PIER
Vol. 119, 449-460, 2011
download: 240
Terahertz Metamaterial Modulators Based on Absorption
Hao Zhou , Fei Ding , Yi Jin and Sailing He
Metamaterial absorbers can perfectly absorb an incident wave in a narrow frequency band. In this paper, metamaterial absorbers are used to construct a terahertz modulator. By controlling the carrier density in the n-doped semiconductor spacer between a patterned metallic superstructure and a metallic ground with different applied voltage bias, the absorption varies sensitively, and the reflected wave amplitude acting as the modulated signal can be strongly modulated. Two types of modulators are investigated, one of which possesses an array of metallic crosses as the superstructure, and the other has a complementary superstructure. Compared with the former, the latter may give a better modulation performance.
TERAHERTZ METAMATERIAL MODULATORS BASED ON ABSORPTION
2011-08-16
PIER
Vol. 119, 435-447, 2011
download: 244
An Intermodulation Recycling Rectifier for Microwave Power Transmission at 2.45 GHz
Chengyang Yu , Changjun Liu , Biao Zhang , Xing Chen and Ka-Ma Huang
The microwave to direct current (MW-DC) conversion efficiency of a rectifier drops significantly in a dual-frequency microwave power transmission (MPT) system. The measured data show that the MW-DC efficiency of a rectifier drops from 67% to 53% when the microwave source is switched from a continuous wave to a dual-tone waveform at the same power level. It is mainly due to the intermodulation effects resulted from a nonlinear component, e.g., the diode, in a rectifier. A novel rectifier is designed to improve the MW-DC efficiency by recycling the intermodulation power besides the harmonic power. With the novel configuration, the maximum MW-DC conversion efficiency of 62% can be achieved for a dual-tone waveform input at 17 dBm. It implies that more than one half of the intermodulation power has been recycled to DC power.
AN INTERMODULATION RECYCLING RECTIFIER FOR MICROWAVE POWER TRANSMISSION AT 2.45 GHz
2011-08-16
PIER
Vol. 119, 423-433, 2011
download: 222
A Low-Profile Unidirectional Cavity-Backed Log-Periodic Slot Antenna
Jun Ou Yang , Song Bo , Jian Zhang and Feng Yang
A low-profile unidirectional cavity-backed coplanar waveguide-fed uniplanar log-periodic slot antenna suitable for the ultra-wideband applications (3-18 GHz) is presented. Due to the inherent balanced structure compared with the unbalanced antennas, such as dipole or loop antenna, the impedance matching and radiation performances of the proposed antenna are quite stable and satisfactory. There is a potential advantage for low profile ultra-wideband unidirectional antennas, and this paper demonstrates a technique for transforming the bidirectional beam into a unidirectional beam by using a special cavity in this ultra-wideband antenna. Meanwhile, the multi-resolution time domain (MRTD) method is applied to analyze this antenna. Experimental results reveal that the cavity has a small affect on the S-parameter of the origin antenna, and remains the perfect reflection property within the desired operation band.
A LOW-PROFILE UNIDIRECTIONAL CAVITY-BACKED LOG-PERIODIC SLOT ANTENNA
2011-08-16
PIER
Vol. 119, 407-421, 2011
download: 461
A Coupled-Line Band-Stop Filter with Three-Section Transmission-Line Stubs and Wide Upper Pass-Band Performance
Yongle Wu and Yuan'an Liu
A novel band-stop filter with wide upper pass-band performance is proposed and discussed in this paper. This band-stop filter includes two three-section transmission-line stubs and a parallel coupled-line section. Because three-section transmission-line stubs and coupled-line section are used, this filter not only features good band-stop filtering property, but also has wide upper pass band. In order to verify this new filter circuit structure and its corresponding design theory, three groups of numerical examples are demonstrated. Finally, two practical band-stop filters using common microstrip technology are designed, simulated and measured. The simulated and measured results indicate that both the coupled-line section with weak coupling and two three-section stubs can improve the upper pass-band performance. Furthermore, the measured results of the second fabricated microstrip band-stop filter (Filter B) show that the 20-dB insertion-loss band-stop bandwidth at 0.46 GHz is 90 MHz and the 1.2-dB transmission coefficient upper pass band is from 0.66 GHz to 2.52 GHz. Thus, the highest pass-band frequency is extended to larger than five times of the operating center frequency of stop band.
A COUPLED-LINE BAND-STOP FILTER WITH THREE-SECTION TRANSMISSION-LINE STUBS AND WIDE UPPER PASS-BAND PERFORMANCE
2011-08-16
PIER
Vol. 119, 395-406, 2011
download: 263
Compact Wideband Gysel Power Divider with Arbitrary Power Division Based on Patch Type Structure
Haiwei Zhang , Xiao-Wei Shi , Feng Wei and Le Xu
A novel Gysel power divider based on patch type structure is presented in this paper. The proposed power divider possesses broad bandwidth, small physical occupation and arbitrary power division. More than 30% bandwidth enhancement is achieved based on the -15 dB input return loss criteria, while 55% size reduction is realized compared with conventional Gysel power divider. What's more, flat dividing is obtained in the design without using additional transmission line sections. Based on the novel structure, a design procedure of power dividers with unequal power division ratios is provided without using narrow microstrip line. To verify the design approach, the proposed power dividers with equal and unequal (2:1 and 4:1) power divisions at the centre frequency 1.5 GHz are fabricated and measured. The results demonstrate that the design can fulfil our goals.
COMPACT WIDEBAND GYSEL POWER DIVIDER WITH ARBITRARY POWER DIVISION BASED ON PATCH TYPE STRUCTURE
2011-08-16
PIER
Vol. 119, 381-394, 2011
download: 212
A Differential Evolution Approach for Robust Adaptive Beamforming Based on Joint Estimation of Look Direction and Array Geometry
Rammohan Mallipeddi , Joni Lie , P. N. Suganthan , Sirajudeen Gulam Razul and Chong Meng S. See
The performance of traditional beamformers tends to degrade due to inaccurate estimation of covariance matrix and imprecise knowledge of array steering vector. The inaccurate estimation of covariance matrix can be attributed to limited data samples and the presence of desired signal in the training data. The mismatch between the actual and presumed steering vectors can be due to the error in the position (geometry) and/or in the look direction estimate. In this paper, we propose a differential evolution (DE) based robust adaptive beamforming that is able to achieve near optimal performance even in the presence of geometry error. Initially, we estimate an optimal steering vector by maximizing and minimizing the signal power in and out of the desired signal's angular range, respectively. Then, we estimate the look direction and reconstruct the covariance matrix. Based on the obtained steering vector, estimate for look direction and reconstructed covariance matrix, near optimal output SINR, can be obtained with the increase in the input SNR without observing any saturation even in the presence of geometry error. Numerical simulations are presented to demonstrate the efficacy of the proposed algorithm.
A DIFFERENTIAL EVOLUTION APPROACH FOR ROBUST ADAPTIVE BEAMFORMING BASED ON JOINT ESTIMATION OF LOOK DIRECTION AND ARRAY GEOMETRY
2011-08-16
PIER
Vol. 119, 363-379, 2011
download: 215
A New Look at the Point Target Reference Spectrum for Bistatic SAR
Junjie Wu , Jianyu Yang , Yulin Huang , Zhe Liu and Haiguang Yang
Focusing bistatic synthetic aperture radar (SAR) data in frequency domain requires two-dimensional (2D) point target reference spectrum (PTRS). Loffeld's bistatic formula (LBF) and the Method of Series Reversion (MSR) have been introduced recently to compute PTRS of bistatic SAR. In this paper, firstly we generalize the original LBF (OLBF) by introducing the Doppler contribution functions of transmitter and receiver. Thus, OLBF and its derivatives (e.g., extended LBF) can be viewed as special forms of the generalized LBF with constant Doppler contributions. Based on this, secondly the ideal LBF (ILBF) with no computing error, except the error resulting from the principle of stationary phase, is also presented. The ILBF reveals that the theoretical PTRS of bistatic SAR consists of only two monostatic terms, but it does not include bistatic deformation term in comparison with OLBF. It supplies us with a target when we deduce the PTRS for bistatic SAR. Finally, to get the precise analytical PTRS for general bistatic SAR, an approximated ILBF (AILBF) is proposed. It expresses the Doppler contributions of the transmitter and receiver as power series and can approach the ILBF very well. AILBF can keep the precision as MSR and inherit a simple form from LBF. In addition, error limit for the validity of bistatic PTRS is also given. The results in this paper can be used to develop imaging algorithms for extreme bistatic (e.g., spaceborne/airborne) and high squint (e.g., bistatic forward-looking) cases.
A NEW LOOK AT THE POINT TARGET REFERENCE SPECTRUM FOR BISTATIC SAR
2011-08-15
PIER
Vol. 119, 345-361, 2011
download: 253
Modal Analysis of Metal-Stub Photonic Band Gap Structures in a Parallel-Plate Waveguide
Ching Pin Yuan and Tsun-Hun Chang
This work presents a theoretical method to solve metal-stub photonic-band-gap (PBG) problems based on the multiple-scattering and modal analysis methods. The multiple-scattering method is generalized, which replaces the scattering coefficient by a mode-coupling matrix. Corresponding sizes between the full dielectric cylinder and the metal stub could be determined based on modal analysis. The metal stub can generate a similar frequency response to that of the full dielectric cylinder, implying that the metal stub is a good substitute for the dielectric cylinder. An experiment conducted at a low terahertz region verifies the theoretical predictions. This work offers a possibility to design two-dimensional photonic crystals using metal stub by adjusting its height for low terahertz applications.
MODAL ANALYSIS OF METAL-STUB PHOTONIC BAND GAP STRUCTURES IN A PARALLEL-PLATE WAVEGUIDE
2011-08-14
PIER
Vol. 119, 335-343, 2011
download: 241
Hydrostatic Pressure Sensor Based on Mode Interference of a Few Mode Fiber
Daru Chen , Chuang Wu , M. L. V. Tse and Hwa-Yaw Tam
A novel hydrostatic pressure sensor based on a few mode fiber (FMF) is proposed. The FMF-based hydrostatic pressure sensor is simply formed by splicing a segment of FMF to two segments of single mode fibers, where the FMF is used as the sensing element. The mode interference between LP01 mode and LP11 mode of the FMF provides an interference spectrum of the FMF-based hydrostatic pressure sensor which is sensitive to the hydrostatic pressure applied on the FMF. We experimentally show that there is a linear relationship between the hydrostatic pressure and the wavelength shift of the interference spectrum of the FMF-based hydrostatic pressure sensor.
HYDROSTATIC PRESSURE SENSOR BASED ON MODE INTERFERENCE OF A FEW MODE FIBER
2011-08-10
PIER
Vol. 119, 315-333, 2011
download: 222
Validation of a Numerical Approach to the Analysis of a Live-Line Worker Exposure to the Electric Field
Wojciech Krajewski
The aim of this paper is to validate a proposed simplified boundary-integral approach (that is called here LEM&BEM) for the analysis of electric field in a live-line-working zone. A human body model of a simplified geometry that is applied to the electric field estimation around the live-line worker is also tested. Numerical results of a more accurate numerical approach, laboratory measurements as well as results of measurements taken on a real tower of HV overhead line are employed for this purpose. The numerical analysis of the electric field distribution in the hot-stick working zone on an anchor tower of 400 kV transmission line is presented to demonstrate the effectiveness of the numerical technique under consideration. The author's own software packages has been applied in computations.
VALIDATION OF A NUMERICAL APPROACH TO THE ANALYSIS OF A LIVE-LINE WORKER EXPOSURE TO THE ELECTRIC FIELD
2011-08-08
PIER
Vol. 119, 299-313, 2011
download: 194
Optimization of the Synchronization Bandwidth of Rationally Synchronized Oscillators Based on Bifurcation Control
Miguel Fernandez-Garcia , Samuel Ver-Hoeye , Carlos Vazquez-Antuna , George Roberto Hotopan , Rene Camblor-Diaz and Fernando Las Heras Andres
In this work, a nonlinear technique for the optimization of the synchronization bandwidth of Rationally Synchronized Oscillators (RSO) is presented. The circuit is forced to operate near a Hopf bifurcation point which is created around the frequency of the input reference signal. Under this operating regime, the reference signal is strongly amplified and the synchronization bandwidth of the circuit is considerably improved. A 5-3 GHz rationally synchronized oscillator has been optimized using the proposed method. The manufactured RSO provides a 5 MHz synchronization bandwidth with a reference signal power of -22 dBm, in good agreement with simulation results.
OPTIMIZATION OF THE SYNCHRONIZATION BANDWIDTH OF RATIONALLY SYNCHRONIZED OSCILLATORS BASED ON BIFURCATION CONTROL
2011-08-05
PIER
Vol. 119, 279-298, 2011
download: 251
Investigation of Low-Grazing-Angle Microwave Backscattering from Threedimensional Breaking Sea Waves
Wei Luo , Min Zhang , Chao Wang and Hong-Cheng Yin
The microwave backscattering of the sea surface is investigated with the wedge-shaped breaking waves for the super events at low grazing angles (LGA). According to the relationship between the wave breaking and the whitecap, the finite three-dimensional wedges are utilized to approximately model the breaking waves, of which the spatial distribution is simulated with whitecap coverage. The phase-modified two-scale method (TSM) and method of equivalent currents (MEC) are used to calculate the surface and volume scattering of sea surface and breaking waves respectively. The sea spikes in LGA are observed by this model, and the strong directionality is caused by the breakers. Considering the Bragg phase velocity, orbital motion of facets and wind drift, the Doppler spectrum is simulated with the time series of sea clutter. Included the breaking waves, the scattering model indicates that the enhanced non-Bragg scattering leads to the extended Doppler spectrum width. The numerical results agree with the measured data well at LGA. Compared with the statistical models, the complex physical mechanism of the sea scattering is explicitly described in this paper.
INVESTIGATION OF LOW-GRAZING-ANGLE MICROWAVE BACKSCATTERING FROM THREEDIMENSIONAL BREAKING SEA WAVES
2011-08-04
PIER
Vol. 119, 265-277, 2011
download: 351
Design of Planar Arrays Composed by an Active Dipole Above a Ground Plane with Parasitic Elements
Juan Antonio Rodríguez-Gonzalez and Francisco Ares-Pena
In this paper, several simple antenna designs based on the use of an active dipole placed above a ground plane with an array of parasitic dipoles are presented. The parasitic dipoles are used to modify the pattern of the active dipole yielding a pencil beam of moderate gain. The use of one active element provides a very simple feeding network that reduces the complexity of the antenna. The proposed technique optimizes the geometry and configuration of both active and parasitic elements. It is shown that the performance of the designed antennas is considerably better than that of a similar antenna without parasitic elements.
DESIGN OF PLANAR ARRAYS COMPOSED BY AN ACTIVE DIPOLE ABOVE A GROUND PLANE WITH PARASITIC ELEMENTS
2011-08-02
PIER
Vol. 119, 253-263, 2011
download: 325
A Validation of Conventional Protection Devices in Protecting EMP Threats
Seung Moon Han , Chang-Su Huh and Jin-Su Choi
The performance of complementary ESD/Lightning protection devices being exposed to EMP was studied. We studied protection devices such as GDT (Gas Discharge Tube), TVS (Transient Voltage suppressor), and Varistor. The EMP signal has a very fast rise time of 100 psec and the maximum peak voltage of 2 kV. The GDT could not protect the EMP signal. The varistor showed about 35% of protection ability, and the TVS showed about 50% of protection ability. Thus the GDT is not a proper device to protect EMP. However, all of the protection devices did not show their nonlinear property.
A VALIDATION OF CONVENTIONAL PROTECTION DEVICES IN PROTECTING EMP THREATS
2011-08-01
PIER
Vol. 119, 239-252, 2011
download: 238
Electromagnetic Scattering and Doppler Analysis of Three-Dimensional Breaking Wave Crests at Low-Grazing Angles
Conghui Qi , Zhiqin Zhao , Wei Yang , Zai-Ping Nie and Guoping Chen
The electromagnetic scattering of the synthesized three-dimensional (3-D) breaking wave crests which are formed by azimuthally aligning the individual 2-D breaking wave profiles has been numerically studied at the low-grazing angles (LGA) by using the multilevel fast multipole algorithm (MLFMA) with adaptive higher order hierarchical Legendre basis functions. Different from the specular (or quasi-specular) reflection and Bragg scattering, the ``sea-spike'' phenomenon which is characterized by that horizontally polarization (HH) signals greatly exceed vertically polarization (VV) signals has been demonstrated by analyzing both the backscattering of 3-D LONGTANK series and a plunging breaker. For the time-dependent evolution of the plunging breaker, the Doppler shifts and Doppler splitting effects are investigated by applying the fast Fourier transform (FFT) with a moving Hamming window. The spectrum of HH scattering has the feature of concentration, while the spectrum of VV scattering shows the Doppler splitting effects.
ELECTROMAGNETIC SCATTERING AND DOPPLER ANALYSIS OF THREE-DIMENSIONAL BREAKING WAVE CRESTS AT LOW-GRAZING ANGLES
2011-07-30
PIER
Vol. 119, 225-237, 2011
download: 199
Dual-Frequency Electromagnetic Cloaks Enabled by LC-Based Metamaterial Circuits
Jin Shao , Hualiang Zhang , Yuankun Lin and Hao Xin
A dual-frequency cloak based on lumped LC-circuits is proposed. Multiple LC-resonant tanks are employed to satisfy the specific conditions for dual-frequency operations. In this way, the designed cloak features greatly reduce scattering cross sections at the two working frequencies simultaneously. Besides, explicit design equations are derived for the developed circuit systems. Based on these formulas, the range of the realizable frequency ratio of the presented cloak (the ratio between the two operating frequencies) is discussed. To verify the theoretical predictions, full-wave electromagnetic simulations are implemented. Good consistency between the numerical results and the design theories is achieved.
DUAL-FREQUENCY ELECTROMAGNETIC CLOAKS ENABLED BY LC-BASED METAMATERIAL CIRCUITS
2011-07-28
PIER
Vol. 119, 207-224, 2011
download: 209
An Advanced Dss-SAR InSAR Terrain Height Estimation Approach Based on Baseline Decoupling
Shuang Li , Huaping Xu and Lvqian Zhang
In the distributed small satellites synthetic aperture radar (DSS-SAR), baseline is usually coupled, that is, along-track baseline and across-track baseline exist simultaneously. However, coupling baseline makes it difficult to distinguish phase differences caused by terrain height and Doppler frequency difference. In SAR interferometry (InSAR) geometric model, across-baseline is necessary to bring interferometric phase to estimate terrain height. Oppositely, along-track baseline will bring extra phase difference and dramatically decrease the accuracy of terrain height estimation. Considering the aforementioned problem, this paper focuses on the study of baseline decoupling of DSS-SAR. We firstly analyze the effect of coupling baseline on terrain height estimation, and then propose the method of baseline decoupling through space projection theory. In order to realize baseline decoupling, equivalent slave satellite, equivalent baseline, and equivalent slant range are defined through projecting slave satellite on range-height plane of master satellite. Furthermore, based on our baseline decoupling, an advanced approach of estimating terrain height is presented, which is more effective than traditional InSAR geometric model. Simulation results illuminate that the baseline decoupling can eliminate along-track baseline effect on terrain height estimation effectively and confirm the validity and efficiency of terrain height estimation approach proposed in this paper.
AN ADVANCED DSS-SAR INSAR TERRAIN HEIGHT ESTIMATION APPROACH BASED ON BASELINE DECOUPLING
2011-07-27
PIER
Vol. 119, 191-206, 2011
download: 221
Superresolution Enhancement for the Superlens with Anti-Reflection and Phase Control Coatings via Surface Plasmons Modes of Asymmetric Structure
Pengfei Cao , Xiaoping Zhang , Wei-Jie Kong , Lin Cheng and Hao Zhang
The paper discusses the reason why the image resolution can be significantly enhanced by the superlens with anti-reflection and phase control coatings (ARPC-superlens) via analyzing the surface plasmons (SPs) modes. ARPC-superlens is an asymmetric structure with finite thickness, in which we first find that there are two asymmetric SPs modes. By comparing the dispersion curve of SPs of ARPC-superlens and the SPs group velocity with their counterparts in the metric ones, we find that the Up Asymmetric Mode and Down Asymmetric Mode are excited within the ARPC-superlens with asymmetric structure. By simulating the aerial images in different SPs modes, the paper also discusses the optimal ratio between the metal slab and the ARPC coatings thickness. The results demonstrate that the subwavelength resolution of ARPC-superlens in Down Asymmetric Mode has been enhanced, when the metal/ARPC thickness ratio is 2:1.
SUPERRESOLUTION ENHANCEMENT FOR THE SUPERLENS WITH ANTI-REFLECTION AND PHASE CONTROL COATINGS VIA SURFACE PLASMONS MODES OF ASYMMETRIC STRUCTURE
2011-07-25
PIER
Vol. 119, 171-190, 2011
download: 273
A Novel High-Power Amplifier Using a Generalized Coupled-Line Transformer with Inherent DC-Block Function
Yongle Wu , Yuan'an Liu , Shun Li and Shulan Li
The purpose of this paper is to propose a novel generalized single-band transformer for two arbitrary complex load and source impedances and a novel high-power amplifier using this new transformer. By adding two reactive parts at across terminals, the coupled line with flexible electrical length has practical even- and odd-mode characteristic impedances. Thus, the total circuit layout can be realized on common printed circuit board without any restriction. The synthesis theory of this proposed transformer is complete and analytical. Furthermore, unlike conventional quarter-wavelength transformers, this structure exhibits four main features such as effective matching for extremely low-resistive load impedance, effective matching for extremely high-resistive load impedance, tunable characteristic for equivalent electrical length and inherent DC-block function. For theoretical verification, several impedance transformers, which include some fixed operating-frequency cases and a tunable case, for smaller than 7 Ohm or larger than 1500 Ohm, are presented. As a typical experimental example, this analyzed transformer with inherent DC-block function has been applied in a 4-Watt power amplifier as output matching structure.
A NOVEL HIGH-POWER AMPLIFIER USING A GENERALIZED COUPLED-LINE TRANSFORMER WITH INHERENT DC-BLOCK FUNCTION
2011-07-25
PIER
Vol. 119, 155-170, 2011
download: 285
An Improved Polar Format Algorithm with Performance Analysis for Geosynchronous Circular SAR 2D Imaging
Qi Liu , Wen Hong , Weixian Tan , Yun Lin , Yanping Wang and Yirong Wu
This paper presents an improved polar format algorithm (PFA) for geosynchronous synthetic aperture radar which undergoes a near-circular track (GeoCSAR). GeoCSAR imaging geometry and signal formulation considering orbit perturbations were derived to ensure accurate slant range between antenna and targets. The illuminated area is more than one million square kilometers due to the long slant distance, resulting in large amount of data to be processed and that the scene is a spherical crown rather than a plane. By assuming spherical wavefronts instead of planar wavefronts, improved polar format algorithm (PFA) was proposed to focus GeoCSAR raw data on a spherical reference surface (ground surface), so that the size of focused scene is no longer limited by the range curvature phase error. Thus, this method could deal with large area imaging for GeoCSAR precisely and efficiently. The implementation procedure, computational complexity, phase error and achievable resolution were presented to show the focusing capabilities of this imaging algorithm. Numerical simulation was further performed to validate the feasibility of this imaging algorithm and the correctness of analysis.
AN IMPROVED POLAR FORMAT ALGORITHM WITH PERFORMANCE ANALYSIS FOR GEOSYNCHRONOUS CIRCULAR SAR 2D IMAGING
2011-07-24
PIER
Vol. 119, 133-153, 2011
download: 298
Calculation of Whole-Body SAR from a 100 MHz Dipole Antenna
Ming Zhang and A. Alden
This paper presents results of a dosimetry study at an FM broadcasting frequency of 100 MHz. The work focused on SAR calculations with high resolution Magnetic Resonance Imaging (MRI)-based full-body models. FDTD computer modeling used a half-wave dipole as the exposure source. Extensive calculations give the variation of SAR with distance and show that whole-body average SAR exhibits a different distance dependency from the incident power density. Body size has a significant effect on SAR. Based on the numerical results, an empirical formula was developed to describe the relationship between antenna input power and distance for the limiting SAR value.
CALCULATION OF WHOLE-BODY SAR FROM A 100 MHZ DIPOLE ANTENNA
2011-07-21
PIER
Vol. 119, 107-132, 2011
download: 239
A Novel Approach to Target Localization through Unknown Walls for through -the-Wall Radar Imaging
Yong Jia , Lingjiang Kong and Xiaobo Yang
This paper mainly deals with the problem of target localization with unknown wall parameters for through-the-wall radar imaging (TWRI) applications. A novel approach is presented to correct the shift in target position due to the ambiguities of the wall parameters. This approach is based on imaging by using at least two assumed wall relative permittivities. For each assumed relative permittivity, a sequence of target images are obtained using different assumed wall thicknesses, and a linear trajectory is formed via Radon transform. The intersection of these linear trajectories corresponding to different assumed relative permittivities is the estimated target position. Besides, the estimated wall parameters are acquired to form the high-quality image. Simulation and experiment results show that the estimated target positions with the proposed approach are well consistent with the true target locations, and the high-quality images are generated with the estimated wall parameters.
A NOVEL APPROACH TO TARGET LOCALIZATION THROUGH UNKNOWN WALLS FOR THROUGH-THE-WALL RADAR IMAGING
2011-07-21
PIER
Vol. 119, 85-105, 2011
download: 279
Taylor-Orthogonal Basis Functions for the Discretization in Method of Moments of Second Kind Integral Equations in the Scattering Analysis of Perfectly Conducting OR Dielectric Objects (Invited Paper)
Eduard Ubeda , José M. Tamayo and Juan Rius
We present new implementations in Method of Moments of two types of second kind integral equations: (i) the recently proposed Electric-Magnetic Field Integral Equation (EMFIE), for perfectly conducting objects, and (ii) the Müller formulation, for homogeneous or piecewise homogeneous dielectric objects. We adopt the Taylor-orthogonal basis functions, a recently presented set of facet-oriented basis functions, which, as we show in this paper, arise from the Taylor's expansion of the current at the centroid of the discretization triangles. We show that the Taylor-orthogonal discretization of the EMFIE mitigates the discrepancy in the computed Radar Cross Section observed in conventional divergence-conforming implementations for moderately small, perfectly conducting, sharp-edged objects. Furthermore, we show that the Taylor-discretization of the Müller-formulation represents a valid option for the analysis of sharp-edged homogenous dielectrics, especially with low dielectric contrasts, when compared with other RWG-discretized implementations for dielectrics. Since the divergence-Taylor Orthogonal basis functions are facet-oriented, they appear better suited than other, edge-oriented, discretization schemes for the analysis of piecewise homogenous objects since they simplify notably the discretization at the junctions arising from the intersection of several dielectric regions.
TAYLOR-ORTHOGONAL BASIS FUNCTIONS FOR THE DISCRETIZATION IN METHOD OF MOMENTS OF SECOND KIND INTEGRAL EQUATIONS IN THE SCATTERING
ANALYSIS OF PERFECTLY CONDUCTING OR DIELECTRIC OBJECTS (Invited Paper)
2011-07-21
PIER
Vol. 119, 59-84, 2011
download: 257
A Contribution to Linearity Improvement of a Highly Efficient Pa for WiMAX Applications
Latifa El Maazouzi , Angel Mediavilla Sanchez and Paolo Colantonio
This paper describes the design of a highly efficient and linear GaN HEMT power amplifier which may be used in WiMAX application. To improve linearity of highly efficient power amplifiers, a technique using diodes in the gate DC path was applied to TL and 2HT amplifier. This solution using diodes offers a good manner to improve linearity near saturation zone compared to the approach using only a DC gate resistor for TL (tuned load) case as well as for 2HT (second harmonic tuning approach). A 2.5 GHz 2HT power amplifier circuit was built, and measured data confirm the linearity improvement, particularly near saturation zone, as predicted by simulation, maintaining higher power performances. An output power of 36.8 dBm has been measured with an associated power added efficiency of 46.5% and carrier to third order intermodulation (C/I3) of 53.4 dBc. A 2HT PA also exhibits good performances across the full (2.3-2.7) GHz band. An output power ranging from (35-36.9) dBm with an associated gain of $12.9±0.9 and a power added efficiency ranging from (40-46)% are measured across the full (2.3-2.7) GHz band.
A CONTRIBUTION TO LINEARITY IMPROVEMENT OF A HIGHLY EFFICIENT PA FOR WIMAX APPLICATIONS
2011-07-19
PIER
Vol. 119, 35-57, 2011
download: 654
SAR Image Simulation with Application to Target Recognition
Yang-Lang Chang , Cheng-Yen Chiang and Kunshan Chen
This paper presents a novel synthetic aperture radar (SAR) image simulation approach to target recognition, which consists of two frameworks, referred to as the satellite SAR images simulation and the target recognition and identification. The images simulation makes use of the sensor and target geo-location relative to the Earth, movement of SAR sensor, SAR system parameters, radiometric and geometric characteristics of the target, and target radar cross section (RCS), orbital parameters estimation, SAR echo signal generation and image focusing to build SAR image database. A hybrid algorithm that combines the physical optics, physical diffraction theory, and shooting and bouncing rays was used to compute the RCS of complex radar targets. Such database is vital for aided target recognition and identification system Followed by reformulating the projection kernel in an optimization equation form, the target's reflectivity field can be accurately estimated. Accordingly, the target's features can be effectively enhanced and extracted, and the dominant scattering centers are well separated. Experimental results demonstrate that the simulated database developed in this paper is well suited for target recognition. Performance is extensively tested and evaluated from real images by Radarsat-2 and TerraSAR-X. Effectiveness and efficiency of the proposed method are further confirmed.
SAR IMAGE SIMULATION WITH APPLICATION TO TARGET RECOGNITION
2011-07-19
PIER
Vol. 119, 19-33, 2011
download: 211
Design of Compact Quadruplexer Based on Defected Stepped Impedance Resonators
Jian Zhong Chen , Nan Wang , Kun Deng and Shuai Yang
A novel compact quadruplexer based on defected stepped impedance resonator (DSIR) with high isolation is presented in this paper. The proposed quadruplexer consists of a common input feeding line, four kinds of folded DSIRs and four individual output feeding lines. Considering the loading effect among channel filters, the input DSIRs must be properly located with respect to the common feeding line in order to realize all external quality factors at the same time, so that the loading effect becomes very small. Furthermore, since the compact DSIRs resonate at multiple fundamental frequencies, a high-isolation quadruplexer with size reduction can be obtained. A fabricated prototype of the proposed quadruplexer is developed. The channel performance obtained by measurement and EM simulation are in good agreement.
DESIGN OF COMPACT QUADRUPLEXER BASED ON DEFECTED STEPPED IMPEDANCE RESONATORS
2011-07-14
PIER
Vol. 119, 1-18, 2011
download: 340
Bistatic Image Formation from Shooting and Bouncing Rays Simulated Current Distributions
H. Buddendick and Thomas F. Eibert
Inverse Synthetic Aperture Radar (ISAR) imaging is one of the most sophisticated methods to obtain information about the scattering or radiation properties of a finite sized object. The idea is to process the scattered or radiated fields coherently over a certain frequency bandwidth and over a certain angular range in order to generate the image. In a simulation based approach, this procedure can be considerably simplified, if the source currents are known (either real or equivalent) and if a bistatic image is desired. By inserting the radiation integral into the imaging integral and by interchanging the integration orders, the imaging point spread function can be generated and the image formation is reduced to a convolution of the point spread function with the current distribution. A concise formulation of this well-known methodology is presented together with a discussion of important properties. Various examples of 2D and 3D images for complex metallic objects such as automobiles are shown, which have been obtained from the surface currents of a Shooting and Bouncing Rays (SBR) field solver.
BISTATIC IMAGE FORMATION FROM SHOOTING AND BOUNCING RAYS SIMULATED CURRENT DISTRIBUTIONS