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2007-12-25
PIER Letters
Vol. 1, 263-273, 2008
download: 179
Tunnel Diode Integrated E-Shaped Patch Antenna for Broadband Operation
Jamshed Ansari and Ram Ram
A tunnel diode integrated E-shaped patch antenna is proposed and analyzed using equivalent circuit concept. It is found that bias voltage of tunnel diode controls the performance of the antenna. Various tunable frequency bands are obtained by selecting suitable bias voltage while antenna topology remains unchanged. Bandwidth of the tunnel diode integrated patch improves to 40.26% over the 32.58% bandwidth of the patch. The radiation pattern also varies with bias voltage and a considerable improvement in beamwidth is observed however radiated power remains almost same.
TUNNEL DIODE INTEGRATED E-SHAPED PATCH ANTENNA FOR BROADBAND OPERATION
2007-12-25
PIER Letters
Vol. 1, 255-261, 2008
download: 342
Wideband Omnidirectional Operation Monopole Antenna
Yung-Tao Liu and Che-Wei Su
This paper presents a square cylindrical monopole antenna easily fabricated using a cross-shaped metal plate for wideband omnidirectional operation. A prototype of the proposed antenna with a cross-sectional area of 8 × 8mm2 is implemented, and the antenna provides a wide operating bandwidth of about 7.5 GHz (1.8-9.4 GHz here), making it very promising for WMAN operation with the 802.16e standard in the 2 to 6 GHz. In addition, over the operating bandwidth, the antenna shows very good omnidirectional radiation patterns.
WIDEBAND OMNIDIRECTIONAL OPERATION MONOPOLE ANTENNA
2007-12-22
PIER Letters
Vol. 1, 245-254, 2008
download: 211
A Novel Design of Arbitrary Shaped Cells for Efficient Coverage from High Altitude Platforms
Yasser Albagory
This paper proposes a novel beamforming technique to form an arbitrary-shaped cell for the high altitude platforms (HAPs) mobile communications. The new technique is based on pattern summation of individual low-sidelobe narrow-beams which constitute the desired cell pattern weighted by an amplitude correcting function. The new cell pattern can be adapted to cover the main highways forming worm-shaped cells which may cover the highway for long distances up 100km and it will has an important role in reducing frequent handoffs and signaling traffic of location updating from moving users over the long highways.
A NOVEL DESIGN OF ARBITRARY SHAPED CELLS FOR EFFICIENT COVERAGE FROM HIGH ALTITUDE PLATFORMS
2007-12-21
PIER Letters
Vol. 1, 237-243, 2008
download: 235
Electronic Spectrum Study of Parabolic GaAs /Al_{X}Ga_{1-X}as Superlattices
Isaac Rodríguez-Vargas , O. Y. Sanchez-Barbosa , David Armando Contreras-Solorio and Stoyan Vlaev
The electronic structure of finite parabolic GaAs/AlxGa1-xAs superlattices is studied. A detailed analysis of the miniband formation is given and the importance of all system parameters is discussed. The dependence of the equidistant miniband separation on the superlattice size is revealed. A comparison with different theoretical methods and experimental data is presented. The calculations are conducted in the framework of the semi-empirical sp3s* tight-binding model including spin applying the Green function formalism and the Surface Green Function Matching Method (SGFM) method.
ELECTRONIC SPECTRUM STUDY OF PARABOLIC GAAS/AL_{X}GA_{1-X}AS SUPERLATTICES
2007-12-19
PIER Letters
Vol. 1, 221-235, 2008
download: 243
Scattering Field for the Ellipsoidal Targets Irradiated by an Electromagnetic Wave with Arbitrary Polarizing and Propagating Direction
Ying-Le Li , Ji-Ying Huang , Ming-Jun Wang and Jiatian Zhang
Obtaining scattering field for an ellipsoid irradiated by electromagnetic wave with arbitrary polarizing and propagating direction is a hard topic that has caused large attention in the world. Literatures relative to it are seldom found. In this paper, the scattering field for an ellipsoid is presented by utilizing the scales transformation of electromagnetic field and coordinate system rotation, as the incident wave irradiating the target with arbitrary polarizing and propagating direction. The result obtained is in good agreement with that in the reference when all the scale factors changes into 1. We take a conductor ellipsoid as an example, simulations both for ellipsoid and plant leaf are presented respectively by way of choosing the different scale factor. Results show that the scattering field is sensitively affected by polarization of the incident wave and varies not too greatly with the incident wave and changes with the observing point. At some points the scattering energy arrives to its maximum.
SCATTERING FIELD FOR THE ELLIPSOIDAL TARGETS IRRADIATED BY AN ELECTROMAGNETIC WAVE WITH ARBITRARY POLARIZING AND PROPAGATING DIRECTION
2007-12-19
PIER Letters
Vol. 1, 211-220, 2008
download: 533
Microstrip Antenna Using Ground-Cut Slots and Miniaturization Techniques with Low RCS
Yan Li , Ying Liu and Shu-Xi Gong
The techniques of ground-cut slots and miniaturization are applied in the design of microstrip antenna which reduces the resonance frequency and size of antenna and achieves the Radar Cross Section (RCS) reduction. Compared with the rectangular patch antenna working at the same frequency, the designed antenna realizes the RCS reduction in the whole frequency band of 2-8 GHz. And the RCS can be reduced 2-4 dB at its working frequency. The RCSp eaks are efficiently controlled to get a smooth curve while the gain loss is only approximately 0.9 dB, which assures the radiation performance. The measured results of radiation performance accord with the simulation results and it implies that this method is feasible.
MICROSTRIP ANTENNA USING GROUND-CUT SLOTS AND MINIATURIZATION TECHNIQUES WITH LOW RCS
2007-12-13
PIER Letters
Vol. 1, 205-210, 2008
download: 178
Numerical Method of Simulation of Material Influences in Mr Tomography
Miloslav Steinbauer , Radek Kubasek and Karel Bartusek
Generally all Magnetic Resonance Imaging (MRI) techniques are affected by magnetic and electric properties of measured materials, resulting in errors in MR image. Using numerical simulation we can solve the effect of changes in homogeneity of static and RF magnetic fields caused by specimen made from conductive and/or magnetic material in MR tomograph. This paper deals with numerical simulation of material susceptibility influence to magnetic field.
NUMERICAL METHOD OF SIMULATION OF MATERIAL INFLUENCES IN MR TOMOGRAPHY
2007-12-13
PIER Letters
Vol. 1, 197-204, 2008
download: 310
Latest Trends in Millimeter-Wave Imaging Technology
Soichi Oka , Hiroyoshi Togo , Naoya Kukutsu and Tadao Nagatsuma
This paper overviews the latest trends of millimeterwave (MMW) imaging technologies, focusing mainly on applications of and technical parameter variations for security surveillance and nondestructive inspections (NDI).We introduce a smart NDI tool using active W-band imaging, which is capable of detecting hidden surface cracks in concrete structures.
LATEST TRENDS IN MILLIMETER-WAVE IMAGING TECHNOLOGY
2007-12-12
PIER Letters
Vol. 1, 189-196, 2008
download: 376
Analysis of Capacitance Across Interconnects of Low-k Dielectric Used in a Deep Sub-Micron CMOS Technology
Sonanvane Avinash , Bhavana N. Joshi and Ashok Mahajan
The paper presents the detailed analysis of the interconnect capacitance, crosstalk time and peak crosstalk voltage. The dependency of the couple capacitance and fringe capacitance on the interconnect layer dimensions affects significantly to the interconnect capacitance. The peak crosstalk time obtained to be 13 femtoseconds for 9.6 femtoseconds of propagation delay, while the maximum crosstalk voltage obtained to be 178 mV.
ANALYSIS OF CAPACITANCE ACROSS INTERCONNECTS OF LOW-K DIELECTRIC USED IN A  DEEP SUB-MICRON CMOS TECHNOLOGY
2007-12-12
PIER Letters
Vol. 1, 181-188, 2008
download: 199
3D Microstructuring of Glass by Femtosecond Laser Direct Writing and Application to Biophotonic Microchips
Koji Sugioka , Yasutaka Hanada and Katsumi Midorikawa
Three-dimensional (3D) microfabrication of photostructurable glass by femtosecond (fs) laser direct writing is demonstrated for manufacture of biophotonic microchips. The fs laser direct writing followed by annealing and successive wet etching can fabricate the hollow microstructures, achieving a variety of microfluidic components and microoptical components in a glass chip. One of the interesting and important applications of the 3D microfluidic structures fabricated by the present technique is inspection of living microorganisms. The microchips used for this application are referred to as nanoaquarium. Furthermore, the optical waveguide is written inside the glass by the fs laser direct writing without the annealing and the successive etching. It is revealed that integration of the microfluidic and microoptical components with the optical waveguides in a single glass chip is of great use for biochemical analysis and medical inspection based on optical sensing.
3D MICROSTRUCTURING OF GLASS BY FEMTOSECOND LASER DIRECT WRITING AND APPLICATION TO BIOPHOTONIC MICROCHIPS
2007-12-12
PIER Letters
Vol. 1, 173-179, 2008
download: 229
An Example of Holographic Radar Using at Restoration Works of Historical Building
Vladimir Razevig , Sergey Ivashov , Anton Sheyko , Igor Vasilyev and Andrey Zhuravlev
The former Senate building, Saint-Petersburg, Russia is being refitted for using it by the Constitutional court of Russian Federation. The team of Remote Sensing Laboratory was invited to participate in this work. The case is that the underfloor water heating system had been installed in the Senate building. The arrangement of pipes hasn't been precisely documented. Besides, there are power and communications cables as well as metal mesh under the concrete floor of the building. Workers were afraid of damaging pipes and cables during laying the parquet floor. Main purpose was to investigate the building floor and to define exact position of pipes and cables with the help of subsurface holographic radars developed by Remote Sensing Laboratory.
AN EXAMPLE OF HOLOGRAPHIC RADAR USING AT RESTORATION WORKS OF HISTORICAL BUILDING
2007-12-10
PIER Letters
Vol. 1, 167-172, 2008
download: 198
Enhancement of the Electronic Confinement Improves the Mobility in P-n -P Delta-Doped Quantum Wells in Si
Augusto Ariza-Flores and Isaac Rodríguez-Vargas
The electronic structure and mobility trends in a n-type delta-doped quantum well in Si, matched between p-type delta-doped barriers of the same material, is presented. The distance between the n-type well and p-type barriers is varied from 50A to 500A; and also the impurity density from 5 × 1012 cm-2 to 5 × 1013 cm-2, for both, donors and acceptors. An increase in the mobility by a factor of 1.6 at interwell distance of 50A with donor and acceptor concentrations of 5 × 1012 cm-2 and 5 × 1013 cm-2 compared with a single delta-doped well without p-type barriers is found. This improvement in mobility could be attributed to a better confinement of carriers, which favors excited levels with nodes in the donor plane. This trade-off between carrier concentration and mobility could be exploited in high-speed, high-power and high-frequency applications.
ENHANCEMENT OF THE ELECTRONIC CONFINEMENT IMPROVES THE MOBILITY IN P-N-P DELTA-DOPED QUANTUM WELLS IN SI
2007-12-10
PIER Letters
Vol. 1, 159-165, 2008
download: 182
Electron Subband Structure and Mobility Trends in P-n Delta-Doped Quantum Wells in Si
Augusto Ariza-Flores and Isaac Rodríguez-Vargas
We present the electronic spectrum of a n-type deltadoped quantum well in Si coupled to a p-type delta-doped barrier within the envelope function effective mass approximation. We applied the Thomas-Fermi approximation to derive an analytical expression for the confining potential, and thus, we obtain the electronic structure in a simple manner. We analyzed the electron subband structure varying the distance between the doping planes (l) as well as the impurity density in them (n2D, p2D). We also study the mobility trends through an empirical formula that is based on the electron levels, the electron wave functions and the Fermi level. We find a monotonic decrease in the mobility as the p-type barrier moves away from the n-type well, and optimum parameters, l = 70A and n2D = 5 × 1012 cm-2 and p2D = 5×1013 cm-2, for maximum mobility.
ELECTRON SUBBAND STRUCTURE AND MOBILITY TRENDS IN P-N DELTA-DOPED QUANTUM WELLS IN SI
2007-12-08
PIER Letters
Vol. 1, 149-158, 2008
download: 193
An Analytic Formula of the Current Distribution for the VLF Horizontal Wire Antenna Above Lossy Half-Space
Hai Chen , Jian-Xin Luo and Da-Kui Zhang
An analytical formula of the current distribution for the VLF horizontal wire antenna located above the ground is presented in this paper. This formula is suitable for the VLF horizontal antenna which is fed at arbitrary position and with arbitrary loaded impedance at the end. In order to validate the analytical formula, a numerical code based on MoM is also developed. The comparison between the results obtained by two methods proves the validity of the analytical formula proposed in this paper.
AN ANALYTIC FORMULA OF THE CURRENT DISTRIBUTION FOR THE VLF HORIZONTAL WIRE ANTENNA ABOVE LOSSY HALF-SPACE
2007-12-08
PIER Letters
Vol. 1, 139-148, 2008
download: 202
Strong Geomagnetic Disturbances and Induced Currents on Earth Surface
Ana Elias and V. Silbergleit
Long-term variations in strong geomagnetic storms are analyzed and linked to electric fields induced on Earth. In fact, geomagnetic disturbances generate electric fields that drive currents in the Earth which may have significant effects on electrical systems and pipelines. The present study will be carried out using aa, AE and Dst index data to estimate long-term variations in strong geomagnetic disturbances. The results are extended then to the space weather topic through a rough assessment of the expected Earth electric field from measured horizontal components of the surface magnetic field, and also through a qualitative estimation of the consequent currents and voltages induced in a pipeline using the distributed source transmission line (DSTL) theory.
STRONG GEOMAGNETIC DISTURBANCES AND INDUCED CURRENTS ON EARTH SURFACE
2007-12-04
PIER Letters
Vol. 1, 129-138, 2008
download: 793
Improving the Performance of an Antenna Array by Using Radar Absorbing Cover
Abdelmonem Abdelaziz
Improving the performance of a microstrip antenna array has been considered based on the innovative use of an absorbing radar cover.Since the surface wave between antennas array elements plays a major role in mutual coupling and scattering behavior of array antenna. The main objective of this work is to reduce the effect of surface wave between array elements using radar absorbing cover.The absorbing cover has been designed with spatial configuration to get maximum performance at the resonant frequency of the fabricated microstrip antenna array.The measured results of the tested antenna array show a significant reduction of both mutual coupling between array patches and radar cross section of the tested antenna array with minimum side effects on the antenna parameters.
IMPROVING THE PERFORMANCE OF AN ANTENNA ARRAY
BY USING RADAR ABSORBING COVER
2007-12-02
PIER Letters
Vol. 1, 119-128, 2008
download: 275
Analysis of Wavefunction Distribution in Quantum Well Biased Laser Diode Using Transfer Matrix Method
Edmund Samuel and Dyneshwar Patil
The paper presents the faster, simpler, and accurate algorithm to solve time independent Schrodinger equation based on transfer matrix method. We can thus calculate all bound and quasi bound energy and the corresponding probability density. A central part of this paper deals with the solving of Schrodinger equation for quantum well structure. Our results show that the transfer matrix method is accurate, it is easier to implement. The increase in well width increases the FWHM from 5.4 nanometer to 9.4 nanometer, while the increase in the Aluminum concentration the FWHM decreases from 8.98 to 5.4.
ANALYSIS OF WAVEFUNCTION DISTRIBUTION IN QUANTUM WELL BIASED LASER DIODE USING TRANSFER MATRIX METHOD
2007-12-02
PIER Letters
Vol. 1, 109-118, 2008
download: 515
The Classical Structure Model of Single Photon and Classical Point of View with Regard to Wave-Particle Duality of Photon
Dong-Lin Zu
The enigma of the wave-particle duality of photon has remained unimpressively explained for a century since Einstein presents the concept of the photon in 1905. This article establishes a classical geometric structure model of a single photon based on field matter, educes a formula for the size of a photon; assumes that there only are two kinds of photon of right hand and left hand circular polarized, and suggests the frequency ω of photon polarization rotated to be its spin frequency. It ascribes the wavelike of photon to its spin motion and the particle-like to its translation motion. From the point of photon particle instead of wave view to re-analyze Young's double-slit interference and polarizer experiments, gives reasonable mechanism. It defines the phase velocity and the group velocity of a photon. It gives a unified and consistent understanding of quantum particle of light and classical electromagnetic waves field. Evidently, such a precisely defined conceptual model is reasonable, objective and easy to accept for classical physicists.
THE CLASSICAL STRUCTURE MODEL OF SINGLE PHOTON AND CLASSICAL POINT OF VIEW WITH REGARD TO WAVE-PARTICLE DUALITY OF PHOTON
2007-11-28
PIER Letters
Vol. 1, 101-108, 2008
download: 265
A Novel Ultra-Wideband Bow-Tie Slot Antenna in Wireless Communication Systems
Yan-Lin Chen , Cheng-Li Ruan and Lin Peng
A novel ultra-wideband bow-tie slot antenna fed by CPW is proposed in this paper. This antenna has been demonstrated to provide an UWB with return loss less than -10 dB from 9.5 GHz to 22.4 GHz. The bandwidth is up to 80%, which is quite better than the traditional bow-tie slot antenna. Simulated and measured results are presented.
A NOVEL ULTRA-WIDEBAND BOW-TIE SLOT ANTENNA IN WIRELESS COMMUNICATION SYSTEMS
2007-11-28
PIER Letters
Vol. 1, 93-99, 2008
download: 417
Reflection and Transmission in the Ionosphere Considering Collisions in a First Approximation
Ali Yesil , Mehmet Aydogdu and Ana Elias
Reflection and transmission coefficients (R and T) of high frequency waves propagating in the ionosphere are studied taking collisions into account. This was done approximating the expression (1 + Z2)-1 in the refractive index using binomial expansion and neglecting terms of order higher than Z2, where Z is the ratio between the electron collision frequency and the wave frequency. R and T height profiles were assessed using the International Reference Ionosphere, IRI, to estimate the ionosphere plasma parameters. Although no significant differences are found between the estimation with and without collisions, the method employed to include collisions may be useful for other purposes where collisions should be taken into account.
REFLECTION AND TRANSMISSION IN THE IONOSPHERE CONSIDERING COLLISIONS IN A FIRST APPROXIMATION
2007-11-27
PIER Letters
Vol. 1, 85-92, 2008
download: 430
Analysis of Electrically Small Size Conical Antennas
Yu Yu Kyi and Jian-Ying Li
It has long been known that the conical antenna has broadband characteristics and good radiation efficiency. The design considerations in reducing the size of top loaded conical antenna by using posts with lumped resistive loading are presented. The resulting antenna can achieve a VSWR of better than 2.0 over 100-800MHz frequency range. Results indicate that the addition of posts and lumped resistive loading has significant role in designing broadband antennas which are in small size.
ANALYSIS OF ELECTRICALLY SMALL SIZE CONICAL ANTENNAS
2007-11-27
PIER Letters
Vol. 1, 77-83, 2008
download: 204
Design for PCS Antenna Based on Wibro-MIMO
Kyeong-Sik Min , Min-Seong Kim , Chul-Keun Park and Manh Vu
This paper presents a design of wireless broadband (WiBro)-multi-input multi-output (MIMO) and personal communication service (PCS) antenna for practical mobile phone. To decrease the mutual coupling of WiBro-MIMO antenna, it is considered on the projected ground structure. In addition, two type PCS antennas for multi-function mobile phone are designed. The proposed antennas are well resonated in each operating frequency band. The measured bandwidths of 3-dimensional (3D) and 2-dimensional (2D) PCS antennas are 110MHz and 130MHz below -10 dB, respectively. The isolations between WiBro-MIMO and two PCS antenna are below -15dB by 2D antenna type and -20dB by 3D antenna type, respectively. The printed IFA has shown a better performance than modified planner IFA with spiral and shorting strip.
DESIGN FOR PCS ANTENNA BASED ON WIBRO-MIMO
2007-11-26
PIER Letters
Vol. 1, 69-75, 2008
download: 236
On the Study of Left-Handed Coplanar Waveguide Coupler on Ferrite\R\Nsubstrate
Mahmoud Abdelrahman Abdalla and Zhirun Hu
This paper introduces a 3 dB tunable symmetric left handed coupled line coupler implemented on ferrite substrate. The proposed coupler is realized in LH coplanar waveguide configuration constructed using interdigital capacitors and meandered line inductors. The analytical analysis and the numerical verification of the proposed couple line coupler are presented. The full wave numerical simulation results for different DC magnetic bias indicate that a tunable left handed coupled line coupler propagation with transmission coefficient up to 3 dB and isolation level more than 25 dB over a wide bandwidth can be achieved.
ON THE STUDY OF LEFT-HANDED COPLANAR WAVEGUIDE COUPLER ON FERRITE\R\NSUBSTRATE
2007-11-26
PIER Letters
Vol. 1, 61-68, 2008
download: 689
Wideband Star-Shaped Microstrip Patch Antenna
M. Abbaspour and Hamid Reza Hassani
A new wideband and small size star shaped patch antenna fed capacitively by a small diamond shape patch is proposed. To enhance the impedance bandwidth, posts are incorporated under the patch antenna.HFSS high frequency simulator is employed to analyze the proposed antenna and simulated results on the return loss, the E and H-plane radiation patterns and Gain of the proposed antenna are presented at various frequencies.The antenna is able to achieve in the range of 4-8.8 GHz an impedance bandwidth of 81% for return loss of less than -10 dB.
WIDEBAND STAR-SHAPED MICROSTRIP PATCH ANTENNA
2007-11-26
PIER Letters
Vol. 1, 51-60, 2008
download: 245
Method of Largest Extended Circle for the Capacitance of Arbitrarily Shaped Conducting Plates
Chang-Hong Liang , Hao-Bo Yuan and Kang-Bo Tan
The most difficult step in the analysis of the capacitance of arbitrarily shaped conductingplates is the determination of the electric center, or the expansion point of the charge density. This paper presents the generalized Huygens' principle, which indicates that the charge distribution on a conducting plate of convex shape has a tendency to be a circle before approachingthe fringe. Therefore, the center of the largest extended circle can be taken as the electric center. The agreement with numerical methods is demonstrated.
METHOD OF LARGEST EXTENDED CIRCLE FOR THE CAPACITANCE OF ARBITRARILY SHAPED CONDUCTING PLATES
2007-11-26
PIER Letters
Vol. 1, 45-50, 2008
download: 801
Improving of Shielding Effectiveness of a Rectangular Metallic Enclosure with Aperture by Using Extra Wall
Mehdi Bahadorzadeh Ghandehari , Mohammad Naser-Moghadasi and Amir Attari
A new method for improving shielding effectiveness (SE) of a rectangular enclosure with multiple apertures has been proposed. In this method in order to compensate the effects of the apertures on reduction of (SE) parameter, instead of the one wall, two metallic walls containing apertures has been used. The numerical simulation uses a symmetric condensed node of TLM-TD (Transmission line Modeling Method-Time Domain) and subsequent Fourier Transform. The shielding effectiveness response to an electric field impulsive excitation is obtained. A study of the influence of the place of apertures in the walls and the distance between the two walls is presented.
IMPROVING OF SHIELDING EFFECTIVENESS OF A RECTANGULAR METALLIC ENCLOSURE WITH APERTURE BY USING EXTRA WALL
2007-11-23
PIER Letters
Vol. 1, 35-44, 2008
download: 213
Wide-Angle Absorption by the Use of a Metamaterial Plate
Andrey Lagarkov , Vladimir N. Kisel and V. Semenenko
The problem regarding top possible (hopefully, total) field suppression of a filamentary source placed above nonuniform impedance plane is discussed. New designs of the electromagnetic field absorbers and resonators are suggested which may be engineered with the use of metamaterials.
WIDE-ANGLE ABSORPTION BY THE USE OF A METAMATERIAL PLATE
2007-11-21
PIER Letters
Vol. 1, 27-33, 2008
download: 181
The Electrostatic Potential Associated to Interface Phonon Modes in Nitride Single Heterostructures
Miguel Mora-Ramos , Rolando Perez-Alvarez and Victor Velasco
The electrostatic potential associated to the interface oscillation modes in nitride-based heterostructure is calculated with the use of a complete phenomenological electroelastic continuum approach for the long wave optical oscillations, and the Surface Green Function Matching technique. The crystalline symmetries of zincblende and - isotropically averaged - wurtzite are both considered in the sets of input bulk frequencies and dielectric constants.
THE ELECTROSTATIC POTENTIAL ASSOCIATED TO INTERFACE PHONON MODES IN NITRIDE SINGLE HETEROSTRUCTURES
2007-11-18
PIER Letters
Vol. 1, 19-25, 2008
download: 281
Circular Fractal Monopole Antenna for Low Vswr UWB Applications
Salman Khan , Jun Hu , Jiang Xiong and Sailing He
A new circular ultra-wideband fractal monopole antenna based on descartes circle theorem (DCT) with elliptical iterations is presented. The proposed fractal design is optimized for return loss below -15 dB. The basic structure is slightly modified to ensure an overall smooth current distribution limited by the junction point nature of the fractal geometries. The measured return loss of the proposed design is below -15 dB within its impedance bandwidth along with omni-directional radiation pattern. Moreover due to the fractal shape, the proposed design has less weight and wind loading effect.
CIRCULAR FRACTAL MONOPOLE ANTENNA FOR LOW VSWR UWB APPLICATIONS
2007-11-16
PIER Letters
Vol. 1, 9-18, 2008
download: 299
Genetic Algorithms and Method of Moments for the Design of PIFAs
Dao Yi Su , De-Min Fu and Ding Yu
This paper presents a novel technique for efficiently combining genetic algorithms (GA's) with method of moments (MOM) for planar inverted-F antennas (PIFAs). MOM is applied to analyze rectangular patches fed by a coaxial probe and shorted with a shorted pin. The impedance matrix of such a mother structure is, then manipulated by a GA optimization procedure in order to detect the optimal patch shape matching the required frequency properties. GA adoption enables optimal shape detection among all possible shapes allowed by the mother structure dimensions. The design example of dual-band antenna is presented, and measurement result is compared to numerical results. Excellent agreement between numerical and measured results is observed.
GENETIC ALGORITHMS AND METHOD OF MOMENTS FOR THE DESIGN OF PIFAS
2007-11-16
PIER Letters
Vol. 1, 1-8, 2008
download: 237
A Novel Technique for Improving the Performance of Salisbury Screen
Abdelmonem Abdelaziz
The most common and simple structure to reduce the level of the reflected power from a metallic surface is the single layer structure known as Salisbury screen which is a sheet of porous material impregnated with graphite and spaced a quarter-wavelength off a metallic backing plate. The main disadvantage of this mechanism is the narrow frequency bandwidth. Many techniques have been reported to improve the working frequency bandwidth but with some degradation in the other technical properties of the overall structure. In this paper a novel technique has been introduced based on a spatial kind of material called circuit analog screen. Theoretical analysis shows that the bandwidth of the reflected power will be improved if the graphite sheet of Salisbury screen has been loaded by circuit analog screen with spatial geometry with spatial parameters.
A NOVEL TECHNIQUE FOR IMPROVING THE PERFORMANCE OF SALISBURY SCREEN