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2014-04-11
PIER
Vol. 145, 319-331, 2014
download: 156
A Method for Designing Broadband Doherty Power Amplifiers
Luca Piazzon Rocco Giofre Paolo Colantonio Franco Giannini
In this contribution, a design approach for the realization of broadband Doherty Power Amplifiers (DPAs) is proposed and demonstrated. The methodology is based on the exploitation of the wideband response of 2-sections branch-line couplers both as input splitter and output combiner of the DPA. These couplers are designed through a CAD optimization process which is specificaly oriented to the developement of DPAs. The method is also applied to realize a GaN based hybrid prototype that shows more than 36% of fractional bandwidth around 2 GHz frequency range, validated through single carriers and modulated signals (3gpp and WiMax). In single carrier mode an efficiency higher than 41% (>50% in saturation, with a peak of 72%) is obtained in 6 dB of output power dynamic range in the entire operating band. Experimental sesults with 5 MHz 3 gpp and WiMax signals shown an average efficiency of 50% and 45% when 37 dBm and 34 dBm of average output power are reached, respectively.
A METHOD FOR DESIGNING BROADBAND DOHERTY POWER AMPLIFIERS
2014-04-09
PIER
Vol. 145, 309-318, 2014
download: 172
Surface Plasmon Resonance Phase-Sensitive Imaging (Spr-Pi) Sensor Based on a Novel Prism Phase Modulator
Gaoao Ye Wei Yang Li Jiang Sailing He
A novel prism phase modulator (PPM) for phase difference modulation between pand s-polarization lights in a surface plasmon resonance phase-sensitive imaging sensor is proposed in this paper. The PPM consists of a rhombic prism (to obtain a curve of phase difference between the two polarizations), a rotation stage and a mirror. The PPM shows great modulation stability and helps to achieve a high detection resolution. Surface plasmon resonance phase imaging is realized with a microfluidic device and a CCD camera. Experimental result shows that the detection resolution of our SPR-PI sensor based on phase-interrogation method is 7.61×10-7 RIU with hydrous samples, which is 16 times improved compared with that based on intensity-interrogation. Real-time monitoring of the interaction between Angiogenin and anti-Angiogenin is also illustrated.
SURFACE PLASMON RESONANCE PHASE-SENSITIVE IMAGING (SPR-PI) SENSOR BASED ON A NOVEL PRISM PHASE MODULATOR
2014-04-03
PIER
Vol. 145, 299-308, 2014
download: 146
Channel Characterization and Finite-State Markov Channel Modeling for Time-Varying Plasma Sheath Surrounding Hypersonic Vehicles
Guolong He Yafeng Zhan Ning Ge Yukui Pei Bin Wu Yuan Zhao
Effects on the communication signals caused by the time-varying plasma sheath surrounding hypersonic vehicles are investigated. Using computational fluid dynamics (CFD) technique, Demetriades's plasma turbulence model and finite-difference time-domain (FDTD) algorithm, amplitude variation and phase fluctuation induced by plasma electron density turbulence are obtained, and their statistical properties are analyzed and characterized. Furthermore, a finite-state Markov channel (FSMC) model is proposed, to represent the dynamical effects on electromagnetic wave propagation through plasma sheath. With high accuracy and greatly reduced complexity, the FMSC model could be very useful to develop novel communication techniques for alleviating the radio blackout problem.
CHANNEL CHARACTERIZATION AND FINITE-STATE MARKOV CHANNEL MODELING FOR TIME-VARYING PLASMA SHEATH SURROUNDING HYPERSONIC VEHICLES
2014-04-03
PIER
Vol. 145, 287-298, 2014
download: 156
Travelling Wave Mechanism and Novel Analysis of the Planar Archimedean Spiral Antenna in Free Space
Teng-Kai Chen Gregory H. Huff
While Archimedean spiral antennas were invented a half-century ago, only self-complementary impedance can be evaluated directly from the Babinet's principle. This paper examines the effects of metal width and arm spacing on printed spiral's input impedance. A model is proposed based on examination by decomposition of planar spiral. A closed-form expression for the input impedance of Archimedean spiral antenna is obtained by evaluating the proposed model with conformal mapping techniques. Full-wave numerical simulations, Babinet's principle, and a fabricated antenna demonstrate the accuracy of the proposed model. The expression in this work can be used to find the impedance of a variety of spiral complementary structures analytically. The examination and discussion on the effects of other parameters and features in addition to the spiral itself are also provided through numerical simulation.
TRAVELLING WAVE MECHANISM AND NOVEL ANALYSIS OF THE PLANAR ARCHIMEDEAN SPIRAL ANTENNA IN FREE SPACE
2014-04-02
PIER
Vol. 145, 273-286, 2014
download: 200
An Improved Quality Guided Phase Unwrapping Method and Its Applications to MRI
Yu-Dong Zhang Shuihua Wang Genlin Ji Zhengchao Dong
An improved method of quality guided phase unwrapping (QGPU) is proposed in this work. It extracts the quality map via a median filtered phase derivative variance (MFPDV) that applies a twodimensional median filter on the phase derivative variance (PDV) map, in order to reduce the effect of noise in the background area. In addition, we employed the Indexed Interwoven Linked List (I2L2) structure to store the orderly adjoin list more efficiently and the Two Section Guided Strategy (TSGS) to reduce comparison frequency. The experiments demonstrate that the normalized L1 norm of MFPDV of a brain MR image is only 0.0827, less than that of PDV method at 0.0923. Besides, the computation time of QGPU with I2L2 technique is only 30% of that with sequence structure, and the computation time of QGPU with TSGS is only 65% of that without TSGS. In total, the proposed MFPDV upwrap phase images better than conventional PDV map, and I2L2 and TSGS are efficient strategies to reduce computation time.
AN IMPROVED QUALITY GUIDED PHASE UNWRAPPING METHOD AND ITS APPLICATIONS TO MRI
2014-04-01
PIER
Vol. 145, 263-272, 2014
download: 175
Dual-Band Circular Polarizer and Linear Polarization Transformer Based on Twisted Split-Ring Structure Asymmetric Chiral Metamaterial
Yongzhi Cheng Yan Nie Zhengze Cheng Rong Zhou Gong
In this paper, a bi-layer twisted split-ring structure asymmetric chiral metamaterial was proposed, which could achieve circularly polarized (giant circular dichroism effect) wave with dual bands and linear polarization transformation (giant optical activity)with asymmetric transmission wave emissions simultaneously from linearly polarized incident wave at microwave frequencies. Experiment and simulation calculations are in good agreement, indicating that the dual-band circular polarizer features high conversion efficiency around 5.32 GHz and 6.6 GHz in addition to large polarization extinction ratio of more than 16 dB, while cross linear polarization transformation with asymmetric transmission is observed around 10.52GHz. The transformation behavior for both circular and linear polarizations could be further illustrated by simulated surface current and electric field distributions. The proposed asymmetric chiral metamaterial structure could be useful in designing novel EM or optical devices, as well as polarization control devices.
DUAL-BAND CIRCULAR POLARIZER AND LINEAR POLARIZATION TRANSFORMER BASED ON TWISTED SPLIT-RING STRUCTURE ASYMMETRIC CHIRAL METAMATERIAL
2014-04-01
PIER
Vol. 145, 251-261, 2014
download: 115
Investigation on Microwave Polarimetric Scattering from Two-Dimensional Wind Fetch- and Water Depth-Limited Nearshore Sea Surfaces
Ding Nie Min Zhang Ning Li
The microwave polarimetric scattering from two-dimensional (2-D) wind fetch- and water depth-limited nearshore sea surface is investigated by using the second-order small-slope approximation (SSA-II). The sea waves are simulated by taking into account the influences of fetch and depth. Based on this, the joint influence of fetch and depth on the normalized radar cross section (NRCS) of sea surfaces for both co-polarizations and cross-polarization in different wind directions is mainly studied. Monostatic and bistatic numerical results both indicate that in the marine environment of small depth and large fetch, the nonlinear interactions among waves become more intense, which has a greater impact on NRCSs for co-polarizations than their cross-polarized counterparts. Comparison of the results for different wind directions also reflects that the backscattered echoes along wind direction have much greater strength, regardless of the magnitude of wind fetch and water depth.
INVESTIGATION ON MICROWAVE POLARIMETRIC SCATTERING FROM TWO-DIMENSIONAL WIND FETCH- AND WATER DEPTH-LIMITED NEARSHORE SEA SURFACES
2014-03-31
PIER
Vol. 145, 241-250, 2014
download: 122
Radar Automatic Target Recognition Based on Sequential Vanishing Component Analysis
Shengqi Liu Ronghui Zhan Jun Zhang Zhaowen Zhuang
To reduce the complexity of classifier design in radar automatic target recognition (RATR), a novel RATR method for high range resolution profile(HRRP) is proposed. Linearly separable features are extracted with sequential vanishing component analysis (SVCA) which is implemented by finding the generators of each approximately vanishing polynomial set, and target classification is implemented with linear classifiers. Experiments are carried out on simulated vehicle target data and MSTAR database, and the results demonstrate the efficiency of the proposed method.
RADAR AUTOMATIC TARGET RECOGNITION BASED ON SEQUENTIAL VANISHING COMPONENT ANALYSIS
2014-03-28
PIER
Vol. 145, 229-240, 2014
download: 134
Setup for Simultaneous Microwave Heating and Real-Time Spectrofluorometric Measurements in Biological Systems
Sophie Kohler Nicolas Ticaud Maria-Minodora Iordache Mihaela G. Moisescu Tudor Savopol Philippe Leveque Delia Arnaud-Cormos
In this paper, a delivery system allowing simultaneous microwave heating and real-time spectrofluorometric measurements in biological systems is proposed and characterized. This system is used to investigate the phase behavior of lipid bilayers from about 15°C to 45°C. The delivery system is based on an open transverse electromagnetic (TEM) cell combined with a spectrofluorometer via an optical cable system. A numerical and experimental dosimetry of the delivery system is conducted. The Specific Absorption Rate (SAR) efficiency of the system is 26.1±2.1 W/kg/W. Spectrofluorometric measurements on Laurdan labeled small unilamellar vesicles (SUVs) are carried out. Generalized polarization (GP) of the SUV' membrane is obtained from the fluorescence intensities measured at two emission wavelengths.
SETUP FOR SIMULTANEOUS MICROWAVE HEATING AND REAL-TIME SPECTROFLUOROMETRIC MEASUREMENTS IN BIOLOGICAL SYSTEMS
2014-03-28
PIER
Vol. 145, 213-227, 2014
download: 415
A General Approach for Brushed DC Machines Simulation Using a Dedicated Field/Circuit Coupled Method
Raphael Andreux Julien Fontchastagner Noureddine Takorabet Nicolas Labbe Jean-Sebastien Metral
This paper deals with the modeling of the brushed DC motor used as a reinforced starter for a micro-hybrid automotive application. The aim of such a system, also called ``stop-start'', is to stop a combustion engine when the vehicle pulls to a stop, and to restart it when the driver accelerates. A reinforced starter is able to ensure this new function in addition to the classical cold start. Then, its life time has to be widely increased in comparison with a classical starter. They have to be optimized, and more especially their process of commutation in order to minimize commutator and brush wears, and thereby increase the lifetime of the device up to the whole life of the vehicle. The main contribution of the paper is the development of a coupled FE-circuit model taking into account local saturation and arc phenomena. Brush-segment contact resistance introduced in the circuit model has been computed efficiently and compared to measures. The whole model has been validated by experimental measurements which are carried out with specific experimental test benches.
A GENERAL APPROACH FOR BRUSHED DC MACHINES SIMULATION USING A DEDICATED FIELD/CIRCUIT COUPLED METHOD
2014-03-24
PIER
Vol. 145, 203-212, 2014
download: 348
A General Method for Designing a Radome to Enhance the Scanning Angle of a Phased Array Antenna
Fei Sun Shuai Zhang Sailing He
We propose a general method to design an arbitrarily shaped radome which can extend the scanning angle of a phased array antenna through finite embedded transformation (FET). The main advantage of our method is that the relationship between the incident angle and steered output angle of the radome can be designed in advance (e.g., a linear relation can be achieved). Unlike a traditional FET, which is often applied onto a slab region, we first apply FET onto an arbitrarily shaped region to bestow the desired radome with an arbitrary shape. Two specific examples have been given to demonstrate our method. Numerical simulations show good performance of our radome.
A GENERAL METHOD FOR DESIGNING A RADOME TO ENHANCE THE SCANNING ANGLE OF A PHASED ARRAY ANTENNA
2014-03-24
PIER
Vol. 145, 195-202, 2014
download: 189
Performance of an Implanted Electrically Coupled Loop Antenna Inside Human Body
Ali Ibraheem Majid Manteghi
Implanted antennas are widely used in hyperthermia and biomedical applications. The antenna needs to be extremely small while maintaining a permissible Specific Absorption Rate (SAR) and being able to cope with the detuning effects due to the dielectric properties of human body tissues. Most of the proposed antennas for implanted applications are electric field antennas such as Planner Inverted-F Antennas (PIFA) and micro-strip patch antennas. By minimizing the size of an electric field antenna, the near zone electric field will increase, resulting in higher SAR. This work is devoted to design a miniaturized magnetic field antenna to overcome the above limitations. The proposed electrically coupled loop antenna (ECLA) has high magnetic field and low electric field in the near zone and therefore, has a small SAR and is less sensitive to detuning effects. ECLA is designed at the Medical Implanted Communication Service (MICS) band with dimensions of (5×5×3 mm3). ECLA has been simulated inside one-layer human body model, three-layer spherical human head model, human head and human body. From the simulation results, ECLA inside the human body has a 5 MHz -3 dB bandwidth, -14 dB gain, and radiation efficiency of 0.525%. The 1 g average SAR inside the human body for 10 mW input power is about 1 W/kg which is 7 times lower than the SAR for a patch antenna of the same size with the same accepted power.
PERFORMANCE OF AN IMPLANTED ELECTRICALLY COUPLED LOOP ANTENNA INSIDE HUMAN BODY
2014-03-24
PIER
Vol. 145, 185-193, 2014
download: 124
Thick Metal EBG Cells with Narrow Gaps and Application to the Design of Miniaturized Antennas
Mehdi Hosseini David M. Klymyshyn Garth Wells Xun Liu
The paper presents a methodology to achieve efficient low-profile electromagnetic bandgap (EBG) antennas based on thick EBG unit cells. The EBG cells are composed of thick metal patches separated by narrow high aspect ratio (HAR) gaps, and positioned on a PEC-backed substrate. This approach yields new miniaturized EBG cells with considerably reduced electrical size. The miniaturized cells are employed to demonstrate new compact self-excited EBG resonator antennas with considerably reduced operating frequencies. Full-wave simulations and experimental results demonstrate the design approach.
THICK METAL EBG CELLS WITH NARROW GAPS AND APPLICATION TO THE DESIGN OF MINIATURIZED ANTENNAS
2014-03-18
PIER
Vol. 145, 175-183, 2014
download: 154
Polarization-Insensitive Triple-Band Microwave Metamaterial Absorber Based on Rotated Square Rings
Guo-Dong Wang Jun-Feng Chen Xiwei Hu Zhao-Quan Chen Minghai Liu
An ultra-thin triple-band metamaterial absorber (MA) is proposed in the microwave region, which is composed of a periodic array of three rotated square rings (RSRs) and a continuous metal film separated by only 1 mm dielectric substrate. The fabricated MA exhibits three experimental absorption peaks at 4.88 GHz, 7.88 GHz, and 11.32 GHz with the corresponding absorption rates of 98.8%, 96.5%, and 95.9%, which shows an excellent agreement with the simulated results. The triple-band MA is polarization-insensitive at the normal incidence. Finally, the multi-reflection interference theory is introduced to interpretate the absorption mechanism. The calculated absorption rates of the improved unit cell for the strongly coupled MA coincide well with the simulated results at wide angles of incidence for both transverse electric (TE) and transverse magnetic (TM) waves.
POLARIZATION-INSENSITIVE TRIPLE-BAND MICROWAVE METAMATERIAL ABSORBER BASED ON ROTATED SQUARE RINGS
2014-03-14
PIER
Vol. 145, 163-173, 2014
download: 124
A Compact and Wideband Circularly Polarized Rectenna with High Efficiency at X-Band
Jinwoo Shin Mihui Seo Junho Choi Joonho So Changyul Cheon
A new design for a compact and wideband circularly-polarized rectenna with high efficiency operating at X-band is proposed. A dual-slot coupled antenna excited by an H-shaped slot fed by a T-shaped microstrip is designed to yield wideband performance as a receiving array antenna. Rectifying circuit models for harmonic suppression circuit, impedance matching, DC-pass circuit, and DC return circuit at the input and output of the diode are built up and optimized to transfer the maximum power from the antenna to the load using an ADS circuit simulator. An RF-DC conversion efficiency of 71.9% is measured on the conditions of 300 load, and 50.1 mW RF input power at 9.5 GHz operating frequency. For the proposed wideband rectenna, the efficiency of more than 50% is measured over a 1 GHz frequency bandwidth. The measured gain, axial ratio, and return loss of the circularly polarized antenna with a 4-element array are 11.2 dBi, 1.1 dB, and -16.4 dB, respectively. The reflection coefficient of the array antenna is measured at less than -10 dB over a wide frequency range of about 2 GHz. Using this antenna as transmitting (TX) and receiving (RX) radiators, the free-space power transfer capability of the rectenna is tested in free space to turn on an LED at 25 cm distance.
A COMPACT AND WIDEBAND CIRCULARLY POLARIZED RECTENNA WITH HIGH EFFICIENCY AT X-BAND
2014-03-12
PIER
Vol. 145, 153-161, 2014
download: 134
The Effect of Antenna Incident Field Distribution on Microwave Tomography Reconstruction
Nozhan Bayat Puyan Mojabi
For microwave tomography applications, we show that the utilized incident field distribution can affect the achievable image quantitative accuracy and resolution. In particular, for the synthetic cases considered here, it is shown that the use of a focused incident field distribution within the imaging domain often results in either enhanced or equivalent image reconstruction as compared to the use of an omnidirectional incident field distribution.
THE EFFECT OF ANTENNA INCIDENT FIELD DISTRIBUTION ON MICROWAVE TOMOGRAPHY RECONSTRUCTION
2014-03-12
PIER
Vol. 145, 141-151, 2014
download: 109
Space-Borne Multibeam Array Pattern Synthesis for Increasing Capacity
Haiwei Song Guang Liang Wenbin Gong Jinpei Yu
The traditional pattern synthesis method of space-borne array is to achieve a ``iso-flux'' beam coverage via approximating a desired pattern; however, the synthesized pattern may not optimize the whole satellite communication (SatCom) system performance. This paper analyzes the interference in multibeam SatCom system using CDMA, and establishes the relation model between user capacity and multibeam pattern. Additionally, a novel particle swarm optimization (PSO) based on simulated annealing (SA) pattern synthesis method is proposed, which chooses user capacity as synthesis objective function. The numerical analysis, which is performed for a hexagonal array with 19 stacked patch elements, confirms that user capacity is at least doubled with the ``max-gain-flux'' beam coverage implemented by our method, compared to the ``iso-flux'' coverage when communication outage probability is 10%.
SPACE-BORNE MULTIBEAM ARRAY PATTERN SYNTHESIS FOR INCREASING CAPACITY
2014-03-11
PIER
Vol. 145, 133-139, 2014
download: 121
A Novel Array Error Estimation Method for Azimuth Multichannel SAR
Xile Ma Zhen Dong Zaoyu Sun Feng He Diannong Liang
Minimum side-zone power to center-zone power ratio (MSCR) method is presented to estimate array errors of azimuth multichannel synthetic aperture radar (SAR). Spaceborne azimuth multichannel SAR is one of the most promising candidates for achieving high-resolution wide-swath imaging. However, array errors brought in by instrument influences and aperture position errors need to be compensated. MSCR method is designed to obtain phase error estimates by minimizing side-zone power to center-zone power ratio, where the side-zone and the center-zone indicate the intervals far from and around Doppler centroid respectively. The proposed method achieves significantly improved performance on phase error estimation especially when signal to noise ratio is low. Experiment results confirm the validity and solidity of the method.
A NOVEL ARRAY ERROR ESTIMATION METHOD FOR AZIMUTH MULTICHANNEL SAR
2014-03-11
PIER
Vol. 145, 123-132, 2014
download: 192
Complex Resonances of a Rectangular Patch in a Multilayered Medium: a New Accurate and Efficient Analytical Technique
Mario Lucido
A new analytical technique to study the complex resonances of a rectangular patch in a multilayered medium is introduced. The problem is formulated as an electric field integral equation (EFIE) in the spectral domain and discretized by means of products of Chebyshev polynomials of first and second kind multiplied by their orthogonal weights in a Galerkin's scheme. The method is fast convergent, i.e., few expansion functions are needed to achieve accurate results, but leads to the numerical evaluation of infinite double integrals of oscillating and slowly decaying functions. To overcome this problem, suitable half-space contributions are pulled out of the kernels of such integrals in order to obtain exponentially decaying integrands. Moreover, the slowly converging integrals of the extracted contributions are expressed as combinations of quickly converging integrals by means of algebraic manipulations and an appropriate integration procedure in the complex plane.
COMPLEX RESONANCES OF A RECTANGULAR PATCH IN A MULTILAYERED MEDIUM: A NEW ACCURATE AND EFFICIENT ANALYTICAL TECHNIQUE
2014-03-05
PIER
Vol. 145, 115-121, 2014
download: 149
MIMO Reference Antennas with Controllable Correlations and Total Efficiencies
Shuai Zhang Kun Zhao Bangguo Zhu Zhinong Ying Sailing He
MIMO reference antennas are proposed for over the air (OTA) measurement applications. The reference antennas could get rid of feeding cable interference and control envelope correlation coefficients (ECC) continuously by only changing the length of an etched slot on a dual-feed PIFA. If only the ECC is investigated, the MIMO reference antenna is optimized to have a small variation of total efficiency from 70% to 50% when the ECC increases from 0.1 to 0.88. The prototypes are fabricated and measured in a scattered field chamber (SFC). Measurements agree well with the simulations. A practical example of applying this kind of reference antenna is provided. If the MIMO performance is studied, the MIMO reference antenna is proposed to own a large variation of total efficiencies from 90% to 47% while the ECC increases from 0 to 0.98. The bandwidth of the proposed reference antennas depend on the size of the antennas. This method is valid for all the frequencies.
MIMO REFERENCE ANTENNAS WITH CONTROLLABLE CORRELATIONS AND TOTAL EFFICIENCIES