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- Nader Engheta (8)
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Articles 31 - 60 of 92
Full-Text Articles in Engineering
Comparison Of Townsend Dielectric Barrier Discharge In N2, N2/O2 And N2/N2o: Behavior And Density Of Radicals, F. Massines, Et. Es-Sebbar, N. Gherardi, N. Naudé, D. Tsyganov, P. Ségur, S. Pancheshnyi
Comparison Of Townsend Dielectric Barrier Discharge In N2, N2/O2 And N2/N2o: Behavior And Density Of Radicals, F. Massines, Et. Es-Sebbar, N. Gherardi, N. Naudé, D. Tsyganov, P. Ségur, S. Pancheshnyi
Dr. Et-touhami Es-sebbar
No abstract provided.
Dual Beam Actuation Of Piezoelectric Aln Rf Mems Switches Integrated With Aln Contour-Mode Resonators, Nipun Sinha, Rashed Mahamameed, Chengjie Zuo, Marcelo B. Pisani, Carlos R. Perez, Gianluca Piazza
Dual Beam Actuation Of Piezoelectric Aln Rf Mems Switches Integrated With Aln Contour-Mode Resonators, Nipun Sinha, Rashed Mahamameed, Chengjie Zuo, Marcelo B. Pisani, Carlos R. Perez, Gianluca Piazza
Nipun Sinha
This work reports on piezoelectric Aluminum Nitride (AlN) based dual-beam RF MEMS switches that have been monolithically integrated with AlN contour-mode resonators. The dual-beam switch design presented in this paper intrinsically compensates for the residual stress in the deposited films, requires low actuation voltage (5-20 V), facilitates active pull-off to open the switch and fast switching times (1 to 2 µsec). This work also presents the combined response (cascaded S-parameters) of a resonator and a switch that were co-fabricated on the same substrate. The response shows that the resonator can be effectively turned on and off by the switch. A …
Dual Beam Actuation Of Piezoelectric Aln Rf Mems Switches Integrated With Aln Contour-Mode Resonators, Nipun Sinha, Rashed Mahamameed, Chengjie Zuo, Marcelo B. Pisani, Carlos R. Perez, Gianluca Piazza
Dual Beam Actuation Of Piezoelectric Aln Rf Mems Switches Integrated With Aln Contour-Mode Resonators, Nipun Sinha, Rashed Mahamameed, Chengjie Zuo, Marcelo B. Pisani, Carlos R. Perez, Gianluca Piazza
Marcelo B Pisani
This work reports on piezoelectric Aluminum Nitride (AlN) based dual-beam RF MEMS switches that have been monolithically integrated with AlN contour-mode resonators. The dual-beam switch design presented in this paper intrinsically compensates for the residual stress in the deposited films, requires low actuation voltage (5-20 V), facilitates active pull-off to open the switch and fast switching times (1 to 2 µsec). This work also presents the combined response (cascaded S-parameters) of a resonator and a switch that were co-fabricated on the same substrate. The response shows that the resonator can be effectively turned on and off by the switch. A …
Hybrid Ultra-Compact 4th Order Band-Pass Filters Based On Piezoelectric Aln Contour-Mode Mems Resonators, Chengjie Zuo, Nipun Sinha, Carlos R. Perez, Rashed Mahameed, Marcelo B. Pisani, Gianluca Piazza
Hybrid Ultra-Compact 4th Order Band-Pass Filters Based On Piezoelectric Aln Contour-Mode Mems Resonators, Chengjie Zuo, Nipun Sinha, Carlos R. Perez, Rashed Mahameed, Marcelo B. Pisani, Gianluca Piazza
Chengjie Zuo
This work reports on the design, fabrication and testing of a new class of hybrid (filter design using combined electrical and mechanical coupling techniques) ultra-compact (800×120 μm) 4th order band-pass filters based on piezoelectric Aluminum Nitride (AlN) contour-mode microelectromechanical (MEM) resonators. The demonstrated 110 MHz filter shows a low insertion loss of 5.2 dB in air, a high out-of-band rejection of 65 dB, a fractional bandwidth as high as 1.14% (hard to obtain when only conventional electrical coupling is used in the AlN contour-mode technology), and unprecedented 30 dB and 50 dB shape factors of 1.93 and 2.36, respectively. All …
Mira V: An Integrated System For Minimally Invasive Robot-Assisted Lung Brachytherapy, A. Trejos, A. Lin, S. Mohan, H. Bassan, C. Edirisinghe, R. Patel, C. Lewis, E. Yu, A. Fenster, R. Malthaner
Mira V: An Integrated System For Minimally Invasive Robot-Assisted Lung Brachytherapy, A. Trejos, A. Lin, S. Mohan, H. Bassan, C. Edirisinghe, R. Patel, C. Lewis, E. Yu, A. Fenster, R. Malthaner
Edward Yu
An integrated system for minimally invasive robot-assisted image-guided lung brachytherapy has been developed. The system incorporates an experimental setup for accurate radioactive seed placement with commercially available dosimetry planning software. The end result is a complete system that allows planning and executing a brachytherapy procedure with increased accuracy. The results of the in vitro seed placement evaluation show that seed misplacement has a significant effect on the volume receiving more than 200% of the dose (V200), and the minimum dosage received by 90% of the volume (D90).
Criteria On Utility Designing Of Convex Optimization In Fdma Networks, Zheng Sun, Wenjun Xu, Zhiqiang He, Kai Niu
Criteria On Utility Designing Of Convex Optimization In Fdma Networks, Zheng Sun, Wenjun Xu, Zhiqiang He, Kai Niu
Zheng Sun
In this paper, we investigate the network utility maximization problem in FDMA systems. We summarize with a suite of criteria on designing utility functions so as to achieve the global optimization convex. After proposing the general form of the utility functions, we present examples of commonly used utility function forms that are consistent with the criteria proposed in this paper, which include the well-known proportional fairness function and the sigmoidal-like functions. In the second part of this paper, we use numerical results to demonstrate a case study based on the criteria mentioned above, which deals with the subcarrier scheduling problem …
Coordinated Design Of Power System Stabilizers And Static Var Compensators In A Multimachine Power System Using Genetic Algorithms, Omar H. Abdalla, Wedad M. Refaey, Mohamed K. Saad, Gamal M. Sarhan
Coordinated Design Of Power System Stabilizers And Static Var Compensators In A Multimachine Power System Using Genetic Algorithms, Omar H. Abdalla, Wedad M. Refaey, Mohamed K. Saad, Gamal M. Sarhan
Omar H. Abdalla
This paper presents a procedure to coordinated design of PSSs and SVCs in a multimachine power system. The aims of the proposed method are to find the best location and the optimal parameters of these compensators in order to improve the steady state and transient performances and also to increase the system damping over a wide range of operating conditions. The objective function of the GA allows the selection of the PSSs and SVCs to shift critical closed loop eigenvalues to the left-hand side in the complex s-plane. The multimachine power system considered in this study consists of nine buses, …
Understanding The Role Of Noise In Stochastic Local Search: Analysis And Experiments, Ole J. Mengshoel
Understanding The Role Of Noise In Stochastic Local Search: Analysis And Experiments, Ole J. Mengshoel
Ole J Mengshoel
Stochastic local search (SLS) algorithms have recently been proven to be among the best approaches to solving computationally hard problems. SLS algorithms typically have a number of parameters, optimized empirically, that characterize and determine their performance. In this article, we focus on the noise parameter. The theoretical foundation of SLS, including an understanding of how to the optimal noise varies with problem difficulty, is lagging compared to the strong empirical results obtained using these algorithms. A purely empirical approach to understanding and optimizing SLS noise, as problem instances vary, can be very computationally intensive. To complement existing experimental results, we …
Cut Loss In Low-Voltage, Wideband Pin Attenuators, Chin-Leong Lim
Cut Loss In Low-Voltage, Wideband Pin Attenuators, Chin-Leong Lim
Chin-Leong Lim
Many RF applications, including Cable and Satellite TV (CATV / SATV) networks, rely on voltage-variable attenuators (VVAs) for gain adjustment. VVAs consisting of PIN diodes arranged as a PI network are popular in CATV / SATV service owing to their constant impedance, high linearity, multi-decade bandwidth, low part count and compactness. When fabricated from thick bulk PIN diodes for high linearity, the PI VVA configuration typically requires a 0-15V control range. But modern equipment typically operates at 5V or less. Capping the control voltage at 5V adversely raises the VVA's minimum attenuation. To enable low voltage operation without degrading the …
Proceedings From Scientific Conference On Green Energy And It, Dr. Erik Dahlquist
Proceedings From Scientific Conference On Green Energy And It, Dr. Erik Dahlquist
Dr. Erik Dahlquist
This conference is part of the annual Energitinget, a national arena for energy in Sweden, with some 2500 participants. The focus with this session is to give a forum for researchers to present scientific results, and also to discuss these with other researchers. It contains papers in the area of Energy and IT as well as Green energy generally
Quranic Verse Recitation Feature Extraction Using Mel-Frequency Cepstral Coefficient (Mfcc), Noor Jamaliah Ibrahim, Zaidi Razak, Emran Mohd Tamil, Mohd Yamani Idna Idris, Zulkifli Mohd Yusoff
Quranic Verse Recitation Feature Extraction Using Mel-Frequency Cepstral Coefficient (Mfcc), Noor Jamaliah Ibrahim, Zaidi Razak, Emran Mohd Tamil, Mohd Yamani Idna Idris, Zulkifli Mohd Yusoff
Noor Jamaliah Ibrahim
Each person’s voice is different. Thus, the Quran sound, which had been recited by most of recitors will probably tend to differ a lot from one person to another. Although those Quranic sentence were particularly taken from the same verse, but the way of the sentence in Al-Quran been recited or delivered may be different. It may produce the difference sounds for the different recitors. Those same combinations of letters may be pronounced differently due to the use of harakates. This paper explores the viability of Mel-Frequency Cepstral Coefficient (MFCC) technique to extract features from Quranic verse recitation. Features extraction …
In Vivo Ultrasonic Attenuation Slope Estimates For Detecting Cervical Ripening In Rats: Preliminary Results, Timothy A. Bigelow, Barbara L. Mcfarlin, William D. O'Brien Jr., Michael L. Oelze
In Vivo Ultrasonic Attenuation Slope Estimates For Detecting Cervical Ripening In Rats: Preliminary Results, Timothy A. Bigelow, Barbara L. Mcfarlin, William D. O'Brien Jr., Michael L. Oelze
Timothy A. Bigelow
To effectively postpone preterm birth, cervical ripening needs to be detected and delayed. As the cervix ripens, the spacing between the collagen fibers increases and fills with water, hyaluronan, decorin, and enzymes suggesting that the ultrasonic attenuation of the cervix should decrease. The decrease in ultrasonic attenuation may be detectable, leading to an effective means of detecting cervical ripening. Herein, the traditional attenuation slope-estimation algorithm based on measuring the downshift in center frequency of the ultrasonic backscattered signal with propagation depth was modified and applied to the cervix of rats. The modified algorithm was verified using computer simulations and an …
Laboratory Experiments As Support To The Built Up Of Titan’S Theoretical Models And Interpretation Of Cassini-Huygens Data, M-C. Gazeau, Y Benilan, Et. Es-Sebbar, T. Ferradaz, E. Hébrard, A. Jolly, F. Raulin, C. Romanzin, J-C. Guillemin, C. Berteloite, A. Canosa, S. D. Le Picard, Ian R. Sims
Laboratory Experiments As Support To The Built Up Of Titan’S Theoretical Models And Interpretation Of Cassini-Huygens Data, M-C. Gazeau, Y Benilan, Et. Es-Sebbar, T. Ferradaz, E. Hébrard, A. Jolly, F. Raulin, C. Romanzin, J-C. Guillemin, C. Berteloite, A. Canosa, S. D. Le Picard, Ian R. Sims
Dr. Et-touhami Es-sebbar
No abstract provided.
Sensor Validation Using Bayesian Networks, Ole J. Mengshoel, Adnan Darwiche, Serdar Uckun
Sensor Validation Using Bayesian Networks, Ole J. Mengshoel, Adnan Darwiche, Serdar Uckun
Ole J Mengshoel
One of NASA’s key mission requirements is robust state estimation. Sensing, using a wide range of sensors and sensor fusion approaches, plays a central role in robust state estimation, and there is a need to diagnose sensor failure as well as component failure. Sensor validation techniques address this problem: given a vector of sensor readings, decide whether sensors have failed, therefore producing bad data. We take in this paper a probabilistic approach, using Bayesian networks, to diagnosis and sensor validation, and investigate several relevant but slightly different Bayesian network queries. We emphasize that onboard inference can be performed on a …
Linear Current-Mode Active Pixel Sensor, Ralf M. Philipp, David Orr, Viktor Gruev, Jan Van Der Spiegel, Ralph Etienne-Cummings
Linear Current-Mode Active Pixel Sensor, Ralf M. Philipp, David Orr, Viktor Gruev, Jan Van Der Spiegel, Ralph Etienne-Cummings
Jan Van der Spiegel
A current mode CMOS active pixel sensor (APS) providing linear light-to-current conversion with inherently low fixed pattern noise (FPN) is presented. The pixel features adjustable-gain current output using a pMOS readout transistor in the linear region of operation. This paper discusses the pixel’s design and operation, and presents an analysis of the pixel’s temporal noise and FPN. Results for zero and first-order pixel mismatch are presented. The pixel was implemented in a both a 3.3 V 0.35 µm and a 1.8 V 0.18 µm CMOS process. The 0.35 µm process pixel had an uncorrected FPN of 1.4%/0.7% with/without column readout …
A Fully Integrated Cmos Phase-Locked Loop With 30mhz To 2ghz Locking Range And ±35 Ps Jitter, Chao Xu, Winslow Sargeant, Kenneth R. Laker, Jan Van Der Spiegel
A Fully Integrated Cmos Phase-Locked Loop With 30mhz To 2ghz Locking Range And ±35 Ps Jitter, Chao Xu, Winslow Sargeant, Kenneth R. Laker, Jan Van Der Spiegel
Jan Van der Spiegel
A fully integrated phase-locked loop (PLL) fabricated in a 0.24μm, 2.5v digital CMOS technology is described. The PLL is intended for use in multi-gigabit-per-second clock recovery circuits in fiber-optic communication chips. This PLL first time achieved a very large locking range measured to be from 30MHz up to 2GHz in 0.24μm CMOS technologies. Also it has very low peak-to-peak jitter less than ±35ps at 1.25GHz output frequency.
Analytical And Experimental Studies Of Thermal Noise In Mosfet's, Suharli Tedja, Jan Van Der Spiegel, Hugh H. Williams
Analytical And Experimental Studies Of Thermal Noise In Mosfet's, Suharli Tedja, Jan Van Der Spiegel, Hugh H. Williams
Jan Van der Spiegel
An analysis of the channel thermal noise in MOSFET's, based on the one-dimensional charge sheet model, is presented. The analytical expression is valid in the strong, moderate, and weak inversion regions. The body effect on the device parameters relevant to the thermal noise is discussed. A measurement technique as well as experimental results of P- and N-MOSFET's of a 1.2 µm radiation hard CMOS process are presented. The calculated channel thermal noise coefficient gamma as in id2/Δf=4kT γ gdo agrees well with experimental data for effective device channel length as short as 1.7µm.
Background Digital Error Correction Technique For Pipelined Analog-Digital Converters, Sameer R. Sonkusale, Jan Van Der Spiegel, K. Nagaraj
Background Digital Error Correction Technique For Pipelined Analog-Digital Converters, Sameer R. Sonkusale, Jan Van Der Spiegel, K. Nagaraj
Jan Van der Spiegel
This paper describes a technique for digital error correction in pipelined analog-digital converters. It makes use of a slow, high resolution ADC in conjunction with an LMS algorithm to perform error correction in the background during normal conversion. The algorithm will be shown to correct for errors due to capacitor ratio mismatch, finite amplifier gain and charge injection within the same framework.
Fully Integrated Cmos Phase-Locked Loop With 30mhz To 2ghz Locking Range And +-35ps Jitter, Chao Xu, Winslow Sargeant, Kenneth R. Laker, Jan Van Der Spiegel
Fully Integrated Cmos Phase-Locked Loop With 30mhz To 2ghz Locking Range And +-35ps Jitter, Chao Xu, Winslow Sargeant, Kenneth R. Laker, Jan Van Der Spiegel
Jan Van der Spiegel
A fully integrated phase-locked loop (PLL) fabricated in a 0.24 micrometer, 2.5v digital CMOS technology is described. The PLL is intended for use in multi-gigabit-per-second clock recovery circuits in fiber-optic communication chip. This PLL first time achieved a very large locking range measured to be from 30MHz up to 2GHz in 0.24 micrometer CMOS technology. Also it has very low peak-to-peak jitter less than +-35ps at 1.25GHz output frequency.
Gbopcad: A Synthesis Tool For High-Performance Gain-Boosted Opamp Design, Jie Yuan, Nabil H. Farhat, Jan Van Der Spiegel
Gbopcad: A Synthesis Tool For High-Performance Gain-Boosted Opamp Design, Jie Yuan, Nabil H. Farhat, Jan Van Der Spiegel
Jan Van der Spiegel
A systematic design methodology for high-performance gain-boosted opamps (GBOs) is presented. The methodology allows the optimization of the GBO in terms of ac response and settling performance and is incorporated into an automatic computer-aided design (CAD) tool, called GBOPCAD. Analytic equations and heuristics are first used by GBOPCAD to obtain a sizing solution close to the global optimum. Then, simulated annealings are used by GBOPCAD to find the global optimum. A sample opamp is designed by this tool in a 0.6-μm CMOS process. It achieves a dc gain of 80 dB, a unity-gain bandwidth of 836 MHz with 60o phase …
Human Behavior Models For Agents In Simulators And Games: Part Ii Gamebot Engineering With Pmfserv, Barry G. Silverman, Gnana K. Bharathy, Kevin O'Brien, Jason Cornwell
Human Behavior Models For Agents In Simulators And Games: Part Ii Gamebot Engineering With Pmfserv, Barry G. Silverman, Gnana K. Bharathy, Kevin O'Brien, Jason Cornwell
Barry G Silverman
Many producers and consumers of legacy training simulator and game environments are beginning to envision a new era where psycho-socio-physiologic models could be interoperated to enhance their environments' simulation of human agents. This paper explores whether we could embed our behavior modeling framework (described in the companion paper, Part 1) behind a legacy first person shooter 3D game environment to recreate portions of the Black Hawk Down scenario. Section 1 amplifies the interoperability needs and challenges confronting the field, presents the questions that are examined, and describes the test scenario. Sections 2 and 3 review the software and knowledge engineering …
Human Behavior Models For Agents In Simulators And Games: Part I: Enabling Science With Pmfserv, Barry G. Silverman, Michael Johns, Jason Cornwell, Kevin O'Brien
Human Behavior Models For Agents In Simulators And Games: Part I: Enabling Science With Pmfserv, Barry G. Silverman, Michael Johns, Jason Cornwell, Kevin O'Brien
Barry G Silverman
This article focuses on challenges to improving the realism of socially intelligent agents and attempts to reflect the state of the art in human behavior modeling with particular attention to the impact of personality/cultural values and affect as well as biology/stress upon individual coping and group decision-making. The first section offers an assessment of the state of the practice and of the need to integrate valid human performance moderator functions (PMFs) from traditionally separated sub-fields of the behavioral literature. The second section pursues this goal by postulating a unifying architecture and principles for integrating existing PMF theories and models. It …
Achieving Transparency With Plasmonic And Metamaterial Coatings, Andrea Alù, Nader Engheta
Achieving Transparency With Plasmonic And Metamaterial Coatings, Andrea Alù, Nader Engheta
Nader Engheta
The possibility of using plasmonic and metamaterial covers to drastically reduce the total scattering cross section of spherical and cylindrical objects is discussed. While it is intuitively expected that increasing the physical size of an object may lead to an increase in its overall scattering cross section, here we see how a proper design of these lossless metamaterial covers near their plasma resonance may induce a dramatic drop in the scattering cross section, making these objects nearly “invisible” or “transparent” to an outside observer—a phenomenon with obvious applications for low-observability and noninvasive probe design. Physical insights into this phenomenon and …
Guided Modes In A Waveguide Filled With A Pair Of Single-Negative (Sng), Double-Negative (Dng), And/Or Double-Positive (Dps) Layers, Andrea Alù, Nader Engheta
Guided Modes In A Waveguide Filled With A Pair Of Single-Negative (Sng), Double-Negative (Dng), And/Or Double-Positive (Dps) Layers, Andrea Alù, Nader Engheta
Nader Engheta
Here we present the results of our theoretical analysis for guided modes in parallel-plate waveguides filled with pairs of parallel layers made of any two of the following materials: 1) a material with negative real permittivity, but positive real permeability (epsilon-negative); 2) a material with negative real permeability, but positive real permittivity (mu-negative); 3) a material with both negative real permittivity and permeability (double-negative); and 4) a conventional material with both positive real permittivity and permeability (double-positive) in a given range of frequency. Salient properties of these guided modes are studied in terms of how these materials and their parameters …
Electromagnetic Wave Propagation In The Wire Medium: A Complex Medium With Long Thin Inclusions, Charles Anthony Moses, Nader Engheta
Electromagnetic Wave Propagation In The Wire Medium: A Complex Medium With Long Thin Inclusions, Charles Anthony Moses, Nader Engheta
Nader Engheta
The wire medium is a type of complex artificial material we conceptually envision as many identical finite-length, parallel, thin wire inclusions embedded within a host medium. It is representative of a class of novel artificial materials characterized by long thin inclusions. Unlike some conventional artificial material, the inclusions of this class are not necessarily electrically short. Here, we present our theoretical analysis for wire media and by studying certain salient features of plane-wave propagation through these media, introduce equivalent medium parameters that depend, among other parameters, on the direction of wave propagation. The approach we use separates the artificial material …
Theory And Simulations Of A Conformal Omni-Directional Sub-Wavelength Metamaterial Leaky-Wave Antenna, Andrea Alù, Filiberto Bilotti, Nader Engheta, Lucio Vegni
Theory And Simulations Of A Conformal Omni-Directional Sub-Wavelength Metamaterial Leaky-Wave Antenna, Andrea Alù, Filiberto Bilotti, Nader Engheta, Lucio Vegni
Nader Engheta
The detailed theory of a single subwavelength conformal radiator that exploits the resonant properties of thin cylindrical metamaterial shells supporting leaky waves is presented. It is shown and reviewed analytically and numerically how a circularly symmetric resonant leaky mode may be supported by a properly designed subwavelength homogenous cylindrical shell of low negative permittivity. Some physical insights are provided and numerical simulations with a feed point, considering also the finiteness of the antenna in the longitudinal direction, are presented and discussed. Moreover, possibilities and limitations of a practical realization of this setup are mentioned, considering in details the possible anisotropies …
Radiation Characteristics Of Microstrip Dipole Antennas Over A High-Impedance Metamaterial Surface Made Of Hilbert Inclusions, John Mcvay, Ahmad Hoorfar, Nader Engheta
Radiation Characteristics Of Microstrip Dipole Antennas Over A High-Impedance Metamaterial Surface Made Of Hilbert Inclusions, John Mcvay, Ahmad Hoorfar, Nader Engheta
Nader Engheta
We analyze numerically the radiation characteristics of center-fed microstrip short dipoles and half-wave dipoles near a high-impedance surface made of Hilbert shape flat inclusions. We study the input impedance, pattern and gain of such radiating structures. We show that the radiation resistance of a microstrip dipole increases noticeably at certain frequencies near the resonant frequency of the Hilbert surface. Moreover, antenna gain enhancement at certain frequencies is observed for all dipole sizes we have analyzed.
Far-Field Subdiffraction Optical Microscopy Using Metamaterial Crystals: Theory And Simulations, Alessandro Salandrino, Nader Engheta
Far-Field Subdiffraction Optical Microscopy Using Metamaterial Crystals: Theory And Simulations, Alessandro Salandrino, Nader Engheta
Nader Engheta
Here we suggest and explore theoretically an idea for a far-field scanless optical microscopy with a subdiffraction resolution. We exploit the special dispersion characteristics of an anisotropic metamaterial crystal that is obliquely cut at its output plane, or has a curved output surface, in order to map the input field distribution onto the crystal’s output surface with a compressed angular spectrum, resulting in a "magnified" image. This can provide a far-field imaging system with a resolution beyond the diffraction limits while no scanning is needed.
Subwavelength, Compact, Resonant Patch Antennas Loaded With Metamaterials, Andrea Alù, Filiberto Bilotti, Nader Engheta, Lucio Vegni
Subwavelength, Compact, Resonant Patch Antennas Loaded With Metamaterials, Andrea Alù, Filiberto Bilotti, Nader Engheta, Lucio Vegni
Nader Engheta
We analyze the matching and radiation properties of subwavelength resonant patch antennas filled with double-negative, double-positive, and/or single-negative metamaterial blocks. Analyzing the theoretical limits inherently present when loading such common radiators with metamaterials, we show how these configurations may exhibit in principle an arbitrarily low resonant frequency for a fixed dimension, but they may not necessarily radiate efficiently when their size is electrically small. However, interesting possibilities are suggested to overcome these limitations by employing circular or more complex patch geometries in order to select specific modes that, when appropriate loading ratios between the filling materials are chosen, also ensure …
Bandwidth, Cross-Polarization, And Feed-Point Characteristics Of Matched Hilbert Antennas, Jinhui Zhu, Ahmad Hoorfar, Nader Engheta
Bandwidth, Cross-Polarization, And Feed-Point Characteristics Of Matched Hilbert Antennas, Jinhui Zhu, Ahmad Hoorfar, Nader Engheta
Nader Engheta
In this work, we have applied a moment-method-based simulation code to perform a detailed parametric study of the bandwidth, cross-polarization level, and the feed location characteristics of the matched Hilbert antenna. It is shown that a properly chosen off-center near-the-end feed point may provide an approximate 50-Ω real input impedance at the fundamental resonant frequency. The role of different iteration order for Hilbert antennas, approximately matched to 50-Ω line, on the bandwidth and cross-polarization level of such antennas are investigated numerically. As was shown by Vinoy et al. the radiation patterns resemble those of a linear dipole and for a …