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2013-10-18 PIER Vol. 142, 799-823, 2013. doi:10.2528/PIER13081408

Circuit and Multipolar Approaches to Investigate the Balance of Powers in 2D Scattering Problems (Invited Paper)

Inigo Liberal, Inigo Ederra, Ramon Gonzalo, and Richard Ziolkowski

Circuit and multipolar approaches are presented to investigate the correlation between absorption and scattering processes in 2D problems. This investigation was inspired by earlier works of Prof.R.E. Collin, which pointed out deficiencies of the Th'evenin/Norton circuit models to evaluate the scattered and absorbed powers associated with receiving antennas and, thus, encouraged research on new analytical tools to address these problems. Power balance results are obtained with both circuit and multipolar approaches that are fully consistent. This analysis serves to illustrate how the correlation between absorption and scattering processes results in upper bounds for their power magnitudes, as well as stringent design trade-offs in both far-field and near-field source and scattering technologies.

2013-10-18 PIER Vol. 142, 771-798, 2013. doi:10.2528/PIER13072702

Polarization-Agile Ads-Interleaved Planar Arrays

Giacomo Oliveri, Leonardo Lizzi, Fabrizio Robol, and Andrea Massa

This paper presents a class of polarization-agile arrays with controlled sidelobes. The architecture is based on the interleaving of two independently polarized sub-arrays through a deterministic strategy derived from Almost Difference Sets (ADSs). The efficiency, flexibility and reliability of the proposed design technique is assessed by means of a set of numerical simulations. Moreover, selected experiments aimed at comparing the performances of the presented approach with state-of-the-art design are provided. Finally, mutual coupling effects are numerically analyzed and discussed.

2013-10-16 PIER Vol. 142, 743-770, 2013. doi:10.2528/PIER13072402

Parameter Selection and Accuracy in Type-3 Non-Uniform FFTs Based on Gaussian Gridding

Amedeo Capozzoli, Claudio Curcio, Angelo Liseno, and Antonio Riccardi

We provide a sucient condition to select the parameters of Type 3 Non-Uniform Fast Fourier Transform (NUFFT) algorithms based on the Gaussian gridding to ful ll a prescribed accuracy. This is a problem of signi cant interest in many areas of applied electromagnetics, as for example fast antenna analysis and synthesis and fast calculation of the scattered elds, as well as in medical imaging comprising ultrasound tomography, computed axial tomography, positron emission tomogr aphy and magnetic resonance imaging. The approach is related to the one dimensional case and follows the work in A. Dutt and V. Rokhlin, SIAM J. Sci. Comp. 14 (1993). The accuracy of the proposed choice is rst numerically assessed and then compared to that achieved by the approach in J.-Y. Lee and L. Greengard, J. Comp. Phys. 206 (2005). The convenience of the strategy devised in this paper is shown. Finally, the use of the Type 3 NUFFT is highlighted for an electromagnetic application consisting of the implementation of the aggregation and disaggregation steps in the fast calculation of the scattered eld by the Fast Multipole Method.

2013-10-14 PIER Vol. 142, 721-742, 2013. doi:10.2528/PIER13091202

Performance Analysis of Bistatic Interferometer Based on Spaceborne SAR

Qilei Zhang and Wenge Chang

This paper presents the performance analysis of Bistatic Interferometer BAsed on Spaceborne SAR (BIBASS). As a bistatic system with general configuration, the system response of BIBASS is azimuth/range dependent. Taking into account this peculiarity, the appropriate theoretical framework is developed to make a more accurate evaluation of the performance of BIBASS. Firstly, the interferometric features are studied. Then, considering all kinds of de-correlation factors, a comprehensive investigation of coherence of such a system is conducted, followed by the relative height accuracy analysis. The theoretical analysis and simulation show that BIBASS, with the ability of high-precision height measurement, can be widely applied as a novel remote sensing measurement system.

2013-10-11 PIER Vol. 142, 701-719, 2013. doi:10.2528/PIER13080809

Effects of the Inductive Port of Blumlein Transmission Line on the Reflection and Transmission Characteristics of Electromagnetic Waves

Yu Zhang and Jinliang Liu

The Blumlein transmission line (BTL) has broad applications in pulse modulation, microwave technology and pulsed power technology. In this paper, a new theoretical method for variable reflection and transmission of electromagnetic waves at the inductive port of transmission line is put forward, in order to analyze the wave reflection characteristics of BTL at the inductive port formed by a saturated magnetic switch. At the inductive port, the variable reflection and transmission mechanisms of the voltage waves traveling through the BTL are analyzed in detail, and the inductive effects on the square voltage pulse of load formed by the BTL are also studied. Simulation and experimental results both demonstrated the proposed new theoretical method which shows great value on high-power microwave technology, high-power pulse forming, pulse shaping and modulation.

2013-10-10 PIER Vol. 142, 683-699, 2013. doi:10.2528/PIER13092509

DC Magnetic Concentrator and Omnidirectional Cascaded Cloak by Using Only One OR Two Homogeneous Anisotropic Materials of Positive Permeability

Fei Sun and Sailing He

A novel concentrator for static magnetic field enhancement is proposed and designed utilizing transformation optics. Compared with other devices for static magnetic field enhancement, our device has many good features: first, our concentrator can achieve a DC magnetic field enhancement in a relatively large free space with high uniformity. Secondly, our concentrator is composed by only one or two homogenous anisotropic materials with principal value greater than zero (without any infinitely large or zero value), which can be achieved by using currently available materials. Thirdly, the geometrical shape of the proposed device determines the enhancement factor and the permeability of the device. After choosing suitable geometrical parameters, we can obtain a concentration with a suitable enhancement factor and a material requirement that is easily achievable. The proposed concentrator will have many important applications in many areas (e.g., magnetic resonance imaging and magnetic sensors). Based on the same theoretical model, we also proposed a cascaded shielding device cloak for static magnetic fields. The proposed DC magnetic shielding device can be realized without using any material of zero permeability, and will have potential applications in, e.g., hiding a metallic object from being detected by a metal locator.

2013-10-09 PIER Vol. 142, 667-681, 2013. doi:10.2528/PIER13080705

Vectorial Electric Field Monte Caro Simulations for Focused Laser Beams (800 nm -2220 nm ) in a Biological Sample

Fuhong Cai, Jiaxin Yu, and Sailing He

Here we develop a method that combines vectorial electric field Monte Carlo simulation with Huygens-Fresnel principle theory to determine the intensity distribution of a focused laser beam in a biological sample. The proper wavelengths for deep tissue imaging can be determined by utilizing our method. Furthermore, effects of anisotropic factor, scattering and absorption coefficients on the focal spots are analyzed. Finally, the focal beams formed by objective lenses with different values of numerical aperture are also simulated to study the focal intensity in the biological sample.

2013-10-09 PIER Vol. 142, 639-665, 2013. doi:10.2528/PIER13071702

Polarimetric SAR Model for Soil Moisture Estimation Over Vineyards at C-Band

Josep David Ballester-Berman, Fernando Vicente-Guijalba, and Juan Manuel Lopez-Sanchez

In this paper we propose a two-component polarimetric model for soil moisture estimation on vineyards suited for C-band radar data. According to a polarimetric analysis carried out here, this scenario is made up of one dominant direct return from the soil and a multiple scattering component accounting for disturbing and nonmodeled signal fluctuations from soil and short vegetation. We propose a combined X-Bragg/Fresnel approach to characterize the polarized direct response from soil. A validation of this polarimetric model has been performed in terms of its consistency with respect to the available data both from RADARSAT-2 and from indoor measurements. High inversion rates are reported for different phenological stages of vines, and the model gives a consistent interpretation of the data as long as the volume component power remains about or below 50% of the surface contribution power. However, the scarcity of soil moisture measurements in this study prevents the validation of the algorithm in terms of the accuracy of soil moisture retrieval and an extensive campaign is required to fully demonstrate the validity of the model. Different sources of mismatches between the model and the data have been also discussed and analyzed.

2013-09-27 PIER Vol. 142, 625-638, 2013. doi:10.2528/PIER13070209

Broadband Millimeterwave Metamaterial Absorber Based on Embedding of Dual Resonators

Pramod Singh, Shideh Kabiri Ameri, Liu Chao, Mohammed Nurul Afsar, and Sameer Sonkusale

Metamaterial based electromagnetic wave absorbers provide perfect absorption only over a narrow bandwidth. In this paper, broadband response is achieved through embedding of one resonator inside another in each unit cell of the metamaterial absorber lattice. These two resonators are oriented in the same direction to achieve reduced coupling between them realizing two absorption frequencies close to each other in order to broaden the effective bandwidth. Paper presents such an absorber at 77 GHz with a bandwidth of 8 GHz with the peak absorption of greater than 98%. The absorber is fabricated on 125 μm thin and flexible polyimide substrate by patterning gold thin film in the shape of two split ring resonators as the metamaterial unit cell. The bandwidth is enhanced by more than a factor of two compared to what could be achieved from a metamaterial with single resonator structure.

2013-09-27 PIER Vol. 142, 615-624, 2013. doi:10.2528/PIER13082105

Casimir Force for Arbitrary Objects Using the Argument Principle and Boundary Element Methods

Phillip R. Atkins, Qi Dai, Wei E. I. Sha, and Weng Cho Chew

Recent progress in the simulation of Casimir forces between various objects has allowed traditional computational electromagnetic solvers to be used to find Casimir forces in arbitrary three-dimensional objects. The underlying theory to these approaches requires knowledge and manipulation of quantum field theory and statistical physics. We present a calculation of the Casimir force using the method of moments via the argument principle. This simplified derivation allows greater freedom in the moment matrix where the argument principle can be used to calculate Casimir forces for arbitrary geometries and materials with the use of various computational electromagnetic techniques.

2013-09-25 PIER Vol. 142, 591-613, 2013. doi:10.2528/PIER13070806

Miniaturized 0.3-6 GHz LTCC Six-Port Receiver for Software Defined Radio

Cristina de la Morena-Álvarez-Palencia, Mateo Burgos-Garcia, and Javier Gismero-Menoyo

The six-port architecture reemerges from the search of low-cost, multi-band and multi-standard transceivers. Its inherent advantages, especially its broadband behavior, make this a structure a good candidate to implement a Software Defined Radio (SDR). However, broadband six-port network designs lead to large size circuits, especially for operating frequencies in the lower gigahertz region. New technologies must be explored in order to achieve compact size and low-cost productions for configurable radio terminals and mobile communication applications. In this paper, the Low Temperature Co-fired Ceramic (LTCC) technology is proposed for implementing a broadband six-port receiver. A compact (30 mm × 30 mm × 1.25 mm) four-octave LTCC sixport receiver is presented. Experimental demodulation results show a good performance over the frequency range from 0.3 to 6 GHz. The demodulation of up to 15.625 Msymbol/s signals, i.e., 93.6 Mbps for 64-QAM, has been satisfactorily performed, with a measured Error Vector Magnitude (EVM) value of 3.7%.

2013-09-23 PIER Vol. 142, 579-590, 2013. doi:10.2528/PIER13082102

Static Magnetic Field Concentration and Enhancement Using Magnetic Materials with Positive Permeability

Fei Sun and Sailing He

In this paper a novel compressor for static magnetic fields is proposed based on finite embedded transformation optics. When the DC magnetic field passes through the designed device, the magnetic field can be compressed inside the device. After it passes through the device, one can obtain an enhanced static magnetic field behind the output surface of the device (in a free space region). We can also combine our compressor with some other structures to get a higher static magnetic field enhancement in a free space region. In contrast with other devices based on transformation optics for enhancing static magnetic fields, our device is not a closed structure and thus has some special applications (e.g., for controlling magnetic nano-particles for gene and drug delivery). The designed compressor can be constructed by using currently available materials or DC meta-materials with positive permeability. Numerical simulation verifies good performance of our device.

2013-09-22 PIER Vol. 142, 559-578, 2013. doi:10.2528/PIER13031402

Lasso Based Performance Evaluation for Sparse One-Dimensional Radar Problem Under Random Sub-Sampling and Gaussian Noise

Yin Xiang, Bingchen Zhang, and Wen Hong

Sparse microwave imaging is the combination of microwave imaging and sparse signal processing, which aims to extract physical and geometry information of sparse or transformed sparse scene from least number of radar measurements. As a primary investigation on its performance, this paper focuses on the performance guarantee for a one-dimensional radar, which detects delays of several point targets located at a sparse scene via randomly sub-sampling of radar returns. Based on the Lasso framework, the quantity relationship among three important factors is discussed, including the sub-sampling ratio ρM, sparse ratio ρK and signal-to-noise ratio (SNR), where ρM is the ratio of number of random sub-sampling to that of Nyquist's sampling, and ρK is the ratio of sparsity to the number of unknowns. In particular, to ensure correct delay detection and accurate back scattering coefficient reconstruction for each target, one needs ρM to be greater than C(ρK)ρKlogN and the input SNR be of order logN, where N is the number of range cells in scene.

2013-09-17 PIER Vol. 142, 545-557, 2013. doi:10.2528/PIER13081802

Novel Energy Harvesting Antenna Design Using a Parasitic Radiator

Jung-Ick Moon and Young-Bae Jung

A novel energy harvesting antenna for various wireless transceivers is proposed. This antenna is composed of two parts, the main and the parasitic radiator. The main radiator has the same role as a general element antenna. i.e., to transmit and receive the RF signal. The parasitic radiator is used to gather the RF power from the main radiators, which mostly do not contribute the main radiator's electrical performance. Thus, we can generate DC power using the dissipated RF energy that is radiated from the main radiator. The main radiator is designed as a printed dipole and the parasitic radiator has a two-turn loop structure fabricated on a substrate. The main radiator is vertically placed on the ground and inserted in the rectangular slit of the substrate of the parasitic radiator. The height of the parasitic radiator can be controlled by two supporters. In the design process, we analyzed how the antenna performance changed when adjusting the height of the parasitic radiator and thus determined its optimal height.

2013-09-17 PIER Vol. 142, 523-544, 2013. doi:10.2528/PIER13081407

Hp-FEM and PML Analysis of Plasmonic Particles in Layered Media

Mengyu Wang, Kersten Schmidt, Aytac Alparslan, and Christian V. Hafner

In this paper, we introduce a high order finite element (FEM) implementation using perfectly matched layer (PML) for the scattering by plasmonic structures inside layered media. The PML is proven to be very accurate and efficient by a comparative analysis with a commercial FEM software and the Multiple Multipole Program (MMP). A convergence analysis using hp-adaptive refinement inside the PML layer shows that adaptive mesh refinement inside the PML layer is most efficient. Based on this convergence analysis an hp-strategy is proposed, which shows a remarkable error reduction for small additional computational costs.

2013-09-16 PIER Vol. 142, 505-521, 2013. doi:10.2528/PIER13080102

Extended High Resolution Range Profile-Jet Engine Modulation Analysis with Signal Eccentricity

Ji-Hoon Park, Woo-Yong Yang, Jun-Woo Bae, Seong-Cheol Kang, and Noh-Hoon Myung

In this paper, high resolution range profile-jet engine modulation (HRRP-JEM) analysis is extended by including quantitative estimation of the jet engine location and extraction of the JEM micro-Doppler component. Based on a parametric model of the range cell data, signal eccentricity was introduced for the purpose of determining the jet engine location. Then, complex empirical mode decomposition (CEMD) was employed to extract the embedded JEM component. The signal eccentricity also served as an auxiliary means of CEMD-based micro-Doppler extraction. Application to the simulated HRRP-JEM data demonstrated that the analysis results described in this paper could be useful for advanced radar target recognition with HRRP-JEM.

2013-09-13 PIER Vol. 142, 485-503, 2013. doi:10.2528/PIER13062805

An Impulse Sampling Approach for Efficient 3D TLM-Based Adjoint Sensitivity Analysis

Osman S. Ahmed, Mohamed H. Bakr, and Xun Li

We present a memory efficient algorithm for the estimation of adjoint sensitivities with the transmission line modeling (TLM) method. Our algorithm manipulates the local scattering matrices to drastically reduce the required storage for problems with lossy dielectric discontinuities. Only one impulse per cell is stored for two dimensional simulations and three impulses per cell are stored for three dimensional simulations. The required memory storage for our impulse sampling approach is only 10% of that of the original TLM-based adjoint sensitivity analysis. The technique is illustrated through two examples including the sensitivity analysis of a dielectric resonator antenna.

2013-09-11 PIER Vol. 142, 463-483, 2013. doi:10.2528/PIER13080706

Full-Vectorial Parallel Finite-Element Contrast Source Inversion Method

Amer Zakaria, Ian Jeffrey, Joe LoVetri, and Amer Zakaria

The multiplicatively regularized finite-element contrast source inversion algorithm (MR-FEM-CSI) is used to solve the full-vectorial three-dimensional (3D) inverse scattering problem. The contrast and contrast-source optimization variables are located at the centroids of tetrahedra within the problem domain; whereas the electric field is expanded in terms of edge basis functions on the same tetrahedra. A dual-mesh is created in order to apply the multiplicative regularization. To handle large-scale problems the inversion algorithm is parallelized using the MPI library, with sparse matrix and vector computations supported by PETSc. The algorithm is tested using experimental datasets obtained from the Institut Fresnel database. A synthetic example shows that the technique is able to successfully image moisture hot-spots within a partially lled grain bin.

2013-09-11 PIER Vol. 142, 437-462, 2013. doi:10.2528/PIER13080802

Dipole Radiation Near Anisotropic Low-Permittivity Media (Invited Paper)

Mohammad Memarian and George Eleftheriades

We investigate radiation of a dipole at or below the interface of (an)isotropic Epsilon Near Zero (ENZ) media, akin to the classic problem of a dipole above a dielectric half-space. To this end, the radiation patterns of dipoles at the interface of air and a general anisotropic medium (or immersed inside the medium) are derived using the Lorentz reciprocity method. By using an ENZ halfspace, air takes on the role of the denser medium. Thus we obtain shaped radiation patterns in air which were only previously attainable inside the dielectric half-space. We then follow the early work of Collin on anisotropic artificial dielectrics which readily enables the implementation of practical anisotropic ENZs by simply stacking sub-wavelength periodic bi-layers of metal and dielectric at optical frequencies. We show that when such a realistic anisotropic ENZ has a low longitudinal permittivity, the desired shaped radiation patterns are achieved in air. In such cases the radiation is also much stronger in air than in the ENZ media, as air is the denser medium. Moreover, we investigate the subtle differences of the dipolar patterns when the anisotropic ENZ dispersion is either elliptic or hyperbolic.

2013-09-11 PIER Vol. 142, 423-435, 2013. doi:10.2528/PIER13080107

Vertical Cascaded Planar EBG Structure for SSN Suppression

Ling-Feng Shi and Hong-Feng Jiang

A novel vertical cascaded planar electromagnetic bandgap (EBG) structure is proposed for SSN suppression with the ultra-wideband at the restraining depth of -30 dB by analyzing the simultaneous switching noise (SSN) suppression mechanism and the equivalent circuit model for EBG structure. Moreover, the SSN suppression bandwidth can be broadened by using different novel EBG structures required by vertically cascading different planar EBG structures. In addition, the structure is verified to meet signal integrity (SI) by the time-domain simulation. The tested results show that the presented EBG is accordant to the simulated results of the theory method by the vector network analyzer. The proposed structures provide a new designing method for EBG structures to improve the ability of suppressing SSN.

2013-09-10 PIER Vol. 142, 409-422, 2013. doi:10.2528/PIER13061303

Radio Interface Design for Inkjet-Printed Biosensor Applications

Janne Jalo, Hannu P. Sillanpaa, and Riku M. Makinen

Biomedical wireless sensors require thin, lightweight, and flexible single-layer structures operating in immediate proximity of human body. This poses a challenge for RF and antenna design required for wireless operation. In this work, the radio interface design for a 2.4 GHz wireless sensor including a discrete filter balun circuit and an antenna operating at 0.3 mm distance from the body is presented. Thin, lightweight single-layer structure is realized using printed electronics manufacturing technology. The RF and antenna designs are validated by measurements, and a sensor with a fully functional radio interface is implemented and verified. At 0.3 mm from the body, 2.4 dB insertion loss and -10 dBi realized gain at 2.4 GHz were achieved for a discrete lter balun and antenna, respectively. The received power level on a Bluetooth low energy (BLE) channel was above -80 dBm at 1 m distance from the body, indicating capability for short-range off-body communications. The paper also provides guidelines for printed electronics RF and antenna design for on-body operation.

2013-09-08 PIER Vol. 142, 389-408, 2013. doi:10.2528/PIER13070404

NMR Detection at 8.9 mT with a GMR Based Sensor Coupled to a Superconducting Nb Flux Transformer

Raffaele Sinibaldi, Cinzia De Luca, Jaakko O. Nieminen, Angelo Galante, Vittorio Pizzella, Piero Sebastiani, Myriam Pannetier-Lecoeur, Antonietta Manna, Piero Chiacchiaretta, Gabriella Tamburro, Antonello Sotgiu, Claude Fermon, Gian Luca Romani, and Stefania Della Penna

This study presents NMR signal detection by means of a superconducting channel consisting of a Nb surface detection coil inductively coupled to a YBCO mixed sensor. The NMR system operates at a low field (8.9 mT) in a magnetically shielded room suitable for magnetoencephalographic (MEG) recordings. The main field is generated by a compact solenoid and the geometry of the pickup coil has been optimized to provide high spatial sensitivity in the NMR field of view. The Nb detection coil is coupled to the mixed sensor through a Nb input coil. The mixed sensor consists of a superconducting YBCO loop with 2-μm constriction above which two Giant Magneto Resistance sensors are placed in a half-bridge configuration to detect changes of the bridge voltage as a function of the flux through the YBCO loop. The sensitivity of the receiving channel is calibrated experimentally. The measured spatial sensitivity is in agreement with the simulations and is ~10 times better than that of the stand-alone mixed sensor. A NMR echo at 375 kHz shows a SNR only a factor 4 smaller than a tuned room temperature coil tightly wound around the sample, with a noise level which is a factor 3 better than for the volume coil. Our results suggest that mixed sensors are suitable for the integration of low-field MRI and MEG in a hybrid apparatus, where MEG and MRI would be recorded by SQUIDs and mixed sensors, respectively.

2013-09-08 PIER Vol. 142, 369-388, 2013. doi:10.2528/PIER13062601

Sparsity of the Field Signal-Based Method for Improving Spatial Resolution in Antenna Sensor Array Processing

Patrizia Vergallo, Aime Lay-Ekuakille, and Diego Caratelli

The goal of array processing is to gather information from propagating radio-wave signals, as their Direction Of Arrival (DOA). The estimation of the DOA can be carried out by extracting the information of interest from the steering vector relevant to the adopted antenna sensor array. Such task can be accomplished in a number of different ways. However, in source estimation problems, it is essential to make use of a processing algorithm which feature not only good accuracy under ideal working conditions, but also robustness against non-idealities such as noise, limitations in the amount of collectible data, correlation between the sources, and modeling errors. In this work particular attention is devoted to spectrum estimation approaches based on sparsity. Conventional algorithms based on Beamforming fail wherein the radio sources are not within Rayleigh resolution range which is a function of the number of sensors and the dimension of the array. DOA estimation techniques such as MUSIC (MUltiple Signal Classifications) allow having a larger spatial resolution compared to Beamforming-based procedures, but if the sources are very close and the Signal to Noise Ratio (SNR) level is low, the resolution turns to be low as well. A better resolution can be obtained by exploiting sparsity: if the number of sources is small, the power spectrum of the signal with respect to the location is sparse. In this way, sparsity can enhance the accuracy of the estimation. In this paper, an estimation procedure based on the sparsity of the radio signals and useful to improve the conventional MUSIC method is presented and analyzed. The sparsity level is set in order to focus the signal energy only along the actual direction of arrival. The obtained numerical results have shown an improvement of the spatial resolution as well as a reduced error in DOA estimation with respect to conventional techniques.

2013-09-06 PIER Vol. 142, 353-368, 2013. doi:10.2528/PIER13052409

A Dispersive Conformal FDTD Technique for Accurate Modeling Electromagnetic Scattering of THz Waves by Inhomogeneous Plasma Cylinder Array

Xia Ai, Yuan Tian, Zhiwei Cui, Yiping Han, and Xiao-Wei Shi

A dispersive conformal FDTD method has been proposed to accurately model the interface between two adjacent dispersive mediums and implemented to study the scattering of THz electromagnetic (EM) waves by inhomogeneous collisional plasma cylinder array. The method is based on the technology of area average, which is different from existing dispersive conformal FDTD schemes. Numerical results show that the proposed method enhance the accuracy level compared to the staircasing FDTD scheme involved in the inhomogeneous plasma. It is interesting to find that the THz EM waves can propagate through the plasma array more easily with higher frequencies or larger separations, hence the scattering width in the backward direction becomes smaller, and the forward scattering exhibits a little difference. This study will be useful for further designing intelligent plasma antenna arrays in THz band and terahertz reentry telemetry through plasma.

2013-09-05 PIER Vol. 142, 333-351, 2013. doi:10.2528/PIER13061712

Electromagnetic Design and Analysis of Magnetless Double-Rotor Dual-Mode Machines

Christopher H. T. Lee, Kwok-Tong Chau, and Chunhua Liu

Two magnetless double-rotor (DR) dual-mode machines, namely the DR DCexcited multi-tooth switched reluctance (DR-DC-MSR) machine and the DR flux-switching DC (DR-FS-DC) machine, are proposed for special direct-drive applications where two rotating bodies are required to operate independently. Both machines can offer two different operation modes, namely the doubly-salient DC (DSDC) mode and MSR mode, normal and fault-tolerant operations, respectively. With the independent armature windings, both machines are able to couple their two rotors with two rotating bodies operating at various speeds. The proposed machines are designed and analyzed by using the time-stepping finite element method (TS-FEM). The simulation results confirm the validity of the proposed machines.

2013-09-05 PIER Vol. 142, 321-332, 2013. doi:10.2528/PIER13081502

A Solar Cell Stacked Slot-Loaded Suspended Microstrip Patch Antenna with Multiband Resonance Characteristics for WLAN and WiMAX Systems

Okan Yurduseven, David Smith, Nicola Pearsall, and Ian Forbes

In this paper, a novel self-complementary shaped multiple-L slot loaded suspended microstrip patch antenna stacked with a polycrystalline silicon (poly-Si) solar cell is presented for 2.4/5.2 GHz band WLAN and 2.5/3.3/5.8 GHz band WiMAX networks. While the proposed self-complementary shaped multiple-L slot loaded suspended patch enables the propagation of multiple TMmn modes to be present, the poly-Si solar cell works as an RF parasitic patch element in addition to its photovoltaic function. The proposed stacked solar antenna combination topology enables the radiating patch to be easily modified by slot-loading to achieve multiband resonance characteristics and the poly-Si solar cell to operate without being shaded by any RF components of the antenna ensuring an optimum solar operation performance.

2013-09-05 PIER Vol. 142, 309-320, 2013. doi:10.2528/PIER13080507

Novel Design of a Compact Triple-Band Bandpass Filter Using Short Stub-Loaded SIRs and Embedded SIRs Structure

Kai-Da Xu, Yong-Hong Zhang, Daotong Li, Yong Fan, Joshua Le-Wei Li, William Joines, and Qing Huo Liu

A novel compact planar triple-band bandpass filter using two sets of short stub-loaded stepped impedance resonators (SSLSIRs) and a pair of embedded stepped impedance resonators (ESIRs) has been proposed. The SSLSIRs can adjust the bandwidths of the corresponding passbands over a wide range, and the ESIRs employing non 0° -feed coupled structure with mixed electric and magnetic coupling can obtain an extra transmission zero. The embedded resonators structure can further miniaturize the dimensions of the whole triple-band filter. The operating frequencies of the SSLSIRs and ESIRs are designed for the applications of the WLAN (2.45/5.2 GHz) and WiMAX (3.5 GHz) systems, respectively. The simulated and measured results are both presented and show good agreement.

2013-09-05 PIER Vol. 142, 291-308, 2013. doi:10.2528/PIER13052014

Horn-Based Circular Polarized Antenna Array with a Compact Feeding for Ka-Band Monopulse Antenna

Yongli Ren, Jian Wang, Da-Cheng Hu, and Ning Zhang

A pyramidal horn monopulse array is proposed for working at Ka-band with circular polarization (CP) characteristic. The array is composed of 28 elements with a 28-way waveguide power divider network. The element has a pyramidal horn with a rectangular waveguide, which is placed downside the horn. And a 45° inclined slot cut in the wide wall of the rectangular waveguide. The inclined slot can convert the excitation into two orthogonal modes (TE10 and TE01) with equal amplitude, and 90° out of phase is produced due to different propagation constants of the two modes in the pyramidal horn. Therefore, the antenna can achieve CP by using a compact structure without polarizer. This paper also provides procedure of the compact power divider network for synthesizing monopulse pattern. This monopulse array has excellent performance: The simulated and measured reflection coefficients of the sum port and the difference port of the array are below -15 dB, the side lobe level of array less than -27 dB, and axial ratio <3 dB in the mainlobe beamwidth. The simulated and measured results are in good agreement.

2013-09-05 PIER Vol. 142, 275-289, 2013. doi:10.2528/PIER13072304

A Novel Double-Winding Permanent Magnet Flux Modulated Machine for Stand-Alone Wind Power Generation

Linni Jian, Jianing Liang, Yujun Shi, and Guo Xu

This paper proposes a novel double-winding flux modulated permanent magnet machine (FMPM) for stand-alone wind power generation. Based on the flux-modulating effect, a concentrated winding set and a distributed winding set can be artfully equipped on one stator component. This makes the proposed machine possessing much simpler structure than traditional double-winding double-stator PM machines. Comparative study shows that the proposed FMPM can offer higher torque capability and stronger flux adjustability than the existing single-winding FMPMs.

2013-09-04 PIER Vol. 142, 261-273, 2013. doi:10.2528/PIER13062001

A 23-GHz Bandwidth Automatic Gain Control Amplifier with Wide Dynamic Range for High Speed Communication

Bo Zhang, Yong-Zhong Xiong, Lei Wang, Sanming Hu, and Joshua Le-Wei Li

In this paper, a wide bandwidth and wide dynamic range AGC amplifier is presented. A push-pull variable gain amplifier (VGA) structure is proposed for wide dynamic rang. Moreover the bandwidth enhancement technique is used in the post amplifier design to ensure the wide bandwidth and gain of whole circuit. The experimental results demonstrate that the proposed AGC amplifier that is fabricated in 0.13 μm SiGe BiCMOS process, achieves a 23-GHz bandwidth and 36-dB dynamic rang among the recently published AGC amplifiers, whereas the power and area consumption are 57.6 mW and 1.9 mm2, respectively.

2013-09-02 PIER Vol. 142, 243-260, 2013. doi:10.2528/PIER13070308

Electromagnetic Isolation of a Microstrip by Embedding in a Spatially Variant Anisotropic Metamaterial

Raymond C. Rumpf, Cesar R. Garcia, Harvey H. Tsang, Julio E. Padilla, and Michael D. Irwin

The near-field surrounding devices can be arbitrarily sculpted if they are placed inside a spatially variant anisotropic metamaterial (SVAM). Our SVAMs are low loss because they do not contain metals and are extraordinarily broadband, working from DC up to a cutoff. In the present work, a microstrip transmission line was isolated from a metal object placed in close proximity by embedding it in an SVAM so that the field avoided the object. Our paper begins by outlining a simple finite-difference modeling approach for studying transmission lines embedded in SVAMs. We then present our design and experimental results to confirm the concept.

2013-09-01 PIER Vol. 142, 231-241, 2013. doi:10.2528/PIER13062806

Application of Interval Analysis on Error Analysis of Reflection-Only Material Characterization Methods

Raenita A. Fenner, Edward J. Rothwell, and Lydell L. Frasch

When performing electromagnetic material characterization, an error analysis should be performed to determine the sensitivity of the extracted permittivity and permeability. Traditional error analysis methods such as the error propagation method and Monte Carlo simulations can pose difficulties when analyzing free space material characterization methods. This paper thus shows how interval analysis can be implemented to perform error analysis on free space material characterization methods and provide an alternate means to perform error analysis. Background is presented on interval representations and interval functions, and a procedure for performing error analysis with interval analysis is presented. An error analysis is performed on the free space implementation of the layer-shift method with interval analysis and the subsequent standard deviations computed with interval analysis are compared to standard deviations computed through Monte Carlo simulation.

2013-09-01 PIER Vol. 142, 221-229, 2013. doi:10.2528/PIER13052607

Four-Band Polarization-Insensitive Metamaterial Absorber Based on Flower-Shaped Structures

Donghao Zheng, Yongzhi Cheng, Dongfang Cheng, Yan Nie, and Rong Zhou Gong

In this paper, a four-band metamaterial absorber (MA) based on flower-shaped structure is proposed. The design, simulation, fabrication, and measurement of the absorbers working in four bands are presented. Simulation results show that the MA has four distinctive absorption peaks at frequencies 6.69 GHz, 7.48 GHz, 8.67 GHz, and 9.91 GHz with the absorptivity of 0.96, 0.99, 0.99 and 0.98, respectively. Experiment results matches well with the simulation. Both experiment and simulation results exhibit that the MA are polarization-insensitive for TE wave and TM wave. The flower-shaped structure is also suitable for designing of a four-band THz and even higher frequency MM absorber, which would be a promising candidate as absorbing elements in scientific and technical applications.

2013-08-25 PIER Vol. 142, 207-220, 2013. doi:10.2528/PIER13071105

Analytical Calculation of the Inductance of Planar Zig-Zag Spiral Inductors

Leonardo Sandrolini, Ugo Reggiani, and Giovanni Puccetti

An analytical procedure for the calculation of the inductance of planar zig-zag spiral inductors is proposed. The procedure is based on the partial inductance concept and models the inductor as a series of a number of parts. The self-inductance of each individual part, which has the shape of a parallelogram, and the mutual inductance between any two parts of the inductor are determined. The inductance of a planar zig-zag spiral inductor can thus be obtained for any width, length and angle of the saw-tooth configuration. The procedure is validated with experimental measurements; the agreement between estimated and measured inductances is very good.

2013-08-25 PIER Vol. 142, 189-205, 2013. doi:10.2528/PIER13070204

Reconfigurable SIW Antenna Based on RF-MEMS Switches

Bahram Khalichi, Saeid Nikmehr, and Ali Pourziad

In this article, a novel compact reconfigurable antenna based on substrate integrated waveguide (SIW) technology is introduced. The geometry of the proposed antennas is symmetric with respect to the horizontal center line. The electrical shape of the antenna is composed of double H-plane SIW based horn antennas and radio frequency micro electro mechanical system (RF-MEMS) actuators. The RF-MEMS actuators are integrated in the planar structure of the antenna for reconfiguring the radiation pattern by adding nulls to the pattern. The proper activation/deactivation of the switches alters the modes distributed in the structure and changes the radiation pattern. When different combinations of switches are on or off, the radiation patterns have 2, 4, 6, 8,... nulls with nearly similar operating frequencies. The attained peak gain of the proposed antenna is higher than 5 dB at any point on the far field radiation pattern except at the null positions. The design procedure and closed form formulation are provided for analytical determination of the antenna parameters. Moreover, the designed antenna with an overall dimensions of only 63:6 ×50 mm2 is fabricated and excited through standard SMA connector and compared with the simulated results. The measured results show that the antenna can clearly alters its beams using the switching components. The proposed antenna retains advantages of low cost, low cross-polarized radiation, and easy integration configuration.

2013-08-25 PIER Vol. 142, 159-188, 2013. doi:10.2528/PIER13060906

Semi-Analytical Solutions of the 3-D Homogeneous Helmholtz Equation by the Method of Connected Local Fields

Hung-Wen Chang and Sin-Yuan Mu

We advance the theory of the two-dimensional method of connected local fields (CLF) to the three-dimensional cases. CLF is suitable for obtaining semi-analytical solutions of Helmholtz equation. The fundamental building block (cell) of the 3-D CLF is a cube consisting of a central point and twenty six points on the cube's surface. These surface points form three symmetry groups: six on the planar faces, twelve on the edges, and eight on the vertices (corners). The local field within the unit cell is expanded in a truncated spherical Fourier-Bessel series. From this representation we develop a closed-form, 3-D local field expansion (LFE) coefficients that relate the central point to its immediate neighbors. We also compute the CLF-based FD-FD numerical solutions of the 3D Green's function in free space. Compared with the analytic solution, we found that even at a low three points per wavelength spatial sampling, the accumulated phase errors of the CLF 3D Green's function after propagating a distance of ten wavelengths are well under ten percent.

2013-08-23 PIER Vol. 142, 141-157, 2013. doi:10.2528/PIER13052906

Complete Complementary Sequence Coding Waveform Based Azimuth Multi-Channel Space-Borne SAR with Ultra-Low Range Sidelobe Ratio Performance

Jie Chen, Yanqing Zhu, Pengbo Wang, and Wei Yang

Sidelobes of strong targets substantially impact image quality of synthetic aperture radar (SAR) using linear frequency modulation (LFM) waveform, especially in urban areas. A novel space-borne azimuth multi-channel SAR scheme with ultra-low range sidelobe-ratio (RSLR) performance was proposed, employing complete complementary sequence (CC-S) coding waveform. The CC-S waveform was utilized to acquire ultra-low RSLR performance in range direction. Azimuth multi-channel scheme was introduced, to compensate reduction of effective PRF due to employing CC-S, and to mitigate azimuth resolution lost resulted from strong azimuth weighting, in order to implement low side-lobe performance in both range and azimuth direction. The method for pre-processing the CC-S based multi-channel SAR data was proposed, which would both compensate receiving time difference of sub-sequences and reconstruct azimuth spectrum of multi-channel SAR data. Furthermore, the corresponding image formation algorithm for accurately focusing raw data of the SAR system was also proposed. Computer simulation results were presented, which demonstrated the validity of the proposed SAR scheme and image formation algorithm.

2013-08-23 PIER Vol. 142, 123-140, 2013. doi:10.2528/PIER13062403

A Novel SAR Target Detection Algorithm Based on Contextual Knowledge

Fei Gao, Achang Ru, Jinping Sun, and Amir Hussain

This paper proposes a Synthetic Aperture Radar (SAR) vehicle target detection algorithm based on contextual knowledge. The proposed algorithm firstly obtains the general classification of SAR image with a Markov Random Field (MRF)-based segmentation algorithm; then modifies the prior target presence probability utilizing terrain types, distances to boundary and target aggregation degree; finally gains the detection results using improved Cell Averaging-Constant False Alarm Rate (CA-CFAR). Detections with real SAR image data show that this algorithm can effectively improve target detection rate and reduce false alarms compared with conventional CA-CFAR.

2013-08-21 PIER Vol. 142, 107-121, 2013. doi:10.2528/PIER13071106

A Hybrid Deterministic/Metaheuristic Synthesis Technique for Non-Uniformly Spaced Linear Printed Antenna Arrays

Diego Caratelli, Maria Carolina Vigano, Giovanni Toso, Piero Angeletti, Alexander A. Shibelgut, and Renato Cicchetti

A novel hybrid approach to the synthesis of non-uniformly spaced linear arrays of printed antennas is presented and thoroughly discussed in this paper. In order to account for parasitic mutual coupling between array elements, a dedicated optimization procedure in combination with a multiport network approach is adopted. Selected examples are included in order to assess the effectiveness and versatility of the proposed technique.

2013-08-20 PIER Vol. 142, 75-105, 2013. doi:10.2528/PIER13061709

Attenuation Constants of Radio Waves in Lossy-Walled Rectangular Waveguides

Chenming Zhou, Joseph Waynert, Timothy Plass, and Ronald Jacksha

At the ultra-high frequencies (UHF) common to portable radios, the mine tunnel acts as a dielectric waveguide, directing and absorbing energy as a radio signal propagates. Understanding radio propagation behavior in a dielectric waveguide is critical for designing reliable, optimized communication systems in an underground mine. One of the major parameters used to predict the power attenuation in lossy waveguides is the attenuation constant. In this paper, we theoretically and experimentally investigate the attenuation constants for a rectangular waveguide with dielectric walls. We provide a new derivation of the attenuation constant based on the classic Fresnel reflection coefficients. The new derivation takes advantage of ray representation of plane waves and provides more insight into understanding radio attenuation in tunnels. We also investigate the impact of different parameters on the attenuation constant, including the tunnel transverse dimensions, permittivity, conductivity, frequency, and polarization, with an aim to find their theoretical optimal values that result in the minimum power loss. Additionally, measurements of the attenuation constants of the dominant mode at different frequencies (455, 915, 2450, and 5800 MHz) for a straight concrete tunnel are presented and compared to theoretical predictions. It is shown that the analytical results match the measured results very well at all four frequencies.

2013-08-20 PIER Vol. 142, 57-74, 2013. doi:10.2528/PIER13061008

Fast Parameter Estimation Algorithm for Cubic Phase Signal Based on Quantifying Effects of Doppler Frequency Shift

Jibin Zheng, Tao Su, Qing Huo Liu, Long Zhang, and Wentao Zhu

For the chirp rate and its change rate estimation of cubic phase signal (CPS), conventional algorithms cannot achieve a trade-off between low computational cost and high performance. In this paper, by utilizing the numerical computational method (NCM), effects of Doppler frequency shift are quantified, and the relationships of the optimal signal length with the chirp rate and change rate of chirp rate are obtained. Then a fast parameter estimation algorithm (DMNUFFT), based on dechirp method (DM) and nonuniform fast Fourier transform (NUFFT), is proposed. Compared with existing algorithms, DMNUFFT can achieve high performance with relatively low computational cost. The performance analyses and an application to inverse synthetic aperture radar (ISAR) imaging are shown to validate the effectiveness of DMNUFFT.

2013-08-20 PIER Vol. 142, 41-55, 2013. doi:10.2528/PIER13070405

A Novel Technique for Broadband Circular Polarized PIFA and Diversity PIFA Systems

Xiao-Zheng Lai, Ze-Ming Xie, Xuan-Liang Cen, and Zhiyong Zheng

In this paper, a novel technique for planar inverted-F antenna (PIFA) with broadband circular polarization and pattern diversity is proposed. A defeated ground structure (DGS) has achieved broadband circular polarized (CP) PIFA by using a square branch at the ground corner with arrow-shaped slot. The pattern diversity PIFA system consists of two CP PIFAs placed symmetrically on the diagonal of DGS. Furthermore, the DGS improves port-to-port isolation by using another smaller square branch at the opposite ground corner. Finally, a prototype is fabricated and measured. The measured results agree well with simulation, and show 10-dB matching bandwidth of 16.3% (825-986 MHz), 3-dB axial ratio (AR) bandwidth of 15.5% (830-982 MHz), and 25-dB isolation bandwidth of 12.4% (848-968 MHz), which shows suitability for radio-frequency-identification (RFID) application.

2013-08-16 PIER Vol. 142, 31-40, 2013. doi:10.2528/PIER13060506

Three-Dimensional Polyhedral Invisible Cloak Consisting of Homogeneous Materials

Yihao Yang, Shi Sheng Lin, Zuo Jia Wang, Hongsheng Chen, Huaping Wang, and Erping Li

Invisible cloak with its amazing functions has been turned into reality due to the advent of transformation optics during the past few years. However, the inhomogeneity and singularity of electromagnetic parameters in cloak are still the main bottlenecks for practical realization. In this paper, we propose a scheme of three-dimensional polyhedral invisible cloak to overcome these shortcomings by using a linear homogeneous transformation method. The constitutive parameters of the polyhedral cloak are homogeneous and anisotropic, which are relatively easy for realization. Numerical simulations demonstrate that good invisibility performance can be achieved for any polarization wave. Our work provides a novel approach to simplify three-dimensional cloak in practice.

2013-08-16 PIER Vol. 142, 15-30, 2013. doi:10.2528/PIER13060706

A Spectral Volume Integral Method Using Geometrically Conforming Normal-Vector Fields

Teis J. Coenen and Martijn Constant van Beurden

Scattering characteristics of periodic dielectric gratings can be accurately and efficiently computed via a spectral volume integral equation combined with normal-vector fields defined on the grating geometry. We study the impact of the geometrical discretization on the convergence rate of the scattering characteristics for two-dimensional gratings in both TE and TM polarization and compare these with an independent semi-analytical reference for circular cylinders. We demonstrate that geometrically conforming normal vector fields lead to substantially faster convergence and shorter computation times, as opposed to the commonly applied staircasing or slicing.

2013-08-16 PIER Vol. 142, 1-14, 2013. doi:10.2528/PIER13062701

Contribution to the Development of Flat Fresnel Reflectors in W Band for New Imaging Applications

Kaoutar Zeljami, Juan Vassal'lo, Antonio Tazón, Tomas Fernandez, Angel Mediavilla Sanchez, and Angel Vegas

This work presents an experimental study in W band about the behavior of a plane Fresnel reflector when the feeder changes its position on the surface of a sphere whose centre is the same of the Fresnel plate zones. For this purpose, an experimental system based on seven Fresnel plate zones and two different levels has been developed. The center frequency of the reflector is 96 GHz, the focal length is 100 mm and height between levels is 0.78 mm. Based on this Fresnel reflector, an experimental set up has been developed. The horn antenna feeder is fixed and situated in far field and the receiver is also a horn antenna located at the Fresnel focal distance. Both the reflector and the receiving antenna have some rotation capability to enable measurements from different angles. The experimental results show a good, stable behavior in gain versus the angular position of the feeder. This special property of Fresnel reflectors is impossible in parabolic reflectors and consequently, Fresnel reflectors could be used in new applications as radar imaging, increasing the radar field of view or improving the resolution by means of several squint feeders working simultaneously on the same lens or reflector. Therefore, the main objective of this paper is to analyze the behavior of this experimental set up for developing new Fresnel reflector-based applications.