bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis and optimization of high‐performance antenna feed
Authors: Gupta G. S. , Nguyen D. N. , Huang C. C. 
Published: July 2007

AbstractHybrid‐mode feeds exhibit good axisymmetric copolar radiation patterns and low cross polarization. Practical design often relies on an empirical cut‐and‐try approach and is therefore time consuming and costly. A new computer‐aided design, based on an optimization routine, is proposed and presented in this paper. The analysis employs the mode matching technique at approximated step junctions, and the optimization procedure uses the minimax algorithm. Validation of this approach is supported by the excellent agreement between computed and measured data.
Differential detection of optical heterodyne dpsk communication systems with intersymbol interference
Authors: Zhang Xiupu , Jiang Peixuan 
Published: July 2007

AbstractThe system model for differential detection of optical heterodyne DPSK systems is set up, taking into account the effects of the IF filter and its production of ISI, the additive white Gaussian noise in the receiver and the quantum phase noise of lasers as well as the bandwidth‐time product (BT). We derive the probability distribution function of noise statistics for BT ≥ 1. The bit error rates (BER) are investigated in the presence of ISI. Numerical results for a 140‐Mbit /s system are presented for Gaussian IF filters. It is found that the laser linewidth requirement is the same as the system that does not consider the IF filter effect and the ISI it causes.
A UTD formula for H‐polarization plane wave diffraction by a wedge with impedance faces
Authors: Wang Bing‐Zhong , Lin Weigan 
Published: July 2007

AbstractIn this article, by using the surface reflection coefficients to describe the boundary conditions, a simple uniform geometrical theory of diffraction (UTD) formula for an impedance wedge is given by a rigorous analysis under the assumption that both faces of the wedge are illuminated by a H‐polarization plane wave.
Quasi‐tem analysis of a monolithic microwave GaAs phase shifter
Authors: Singh D. R. , Champlin K. S. 
Published: July 2007

AbstractA simple analytical model is developed for a slow‐wave monolithic microwave variable phase shifter. Propagation characteristics of the phase shifter were evaluated using this model and were found to be in excellent agreement with the experimental results of Neidert and Krowne. The model permits changing various parameters to optimize phase‐shifter performance with relative ease.
Harmonic generation in II‐VI compound semiconductors under hot electron condition
Authors: Dutta A. , Mukhopadhyay D. 
Published: July 2007

AbstractThe second harmonic generation efficiency has been calculated in a number of II‐VI‐compound semiconductors under high‐field condition by approximating the velocity‐field characteristics by a power‐series relation. It is found that the second harmonic generation efficiency is much higher in these materials than in the elemental or IIIV compound semiconductors. Also, because the carrier relaxation times are lower in these materials, they can be used for efficient harmonic power generation in the infrared‐ and millimeter‐wavelength ranges.
Nondiffracting wavefields in grin and free‐space
Authors: Ojeda‐Castañeda J. , Noyola‐Iglesias A. 
Published: July 2007

AbstractThe formal solution to Helmholtz equation is used for finding nondiffracting wavefields in generalized α‐power GRIN and free‐space Two novel solutions contain previously known nondiffracting beams.
High‐frequency resonant‐tunneling oscillators
Authors: Brown E. R. , Parker C. D. , Calawa A. R. , Manfra M. J. , Chen C. L. , Mahoney L. J. , Goodhue W. D. , Söderströom J. R. , McGill T. C. 
Published: July 2007

AbstractAdvances in high‐frequency resonant‐tunneling‐diode (RTD) oscillators are described. Oscillations up to a frequency of 420 GHz have been achieved in the GaAs/AlAs system. Recent results obtained with In0.53 Ga0.47As/AlAs and InAs/AlSb RTDs show a greatly increased power density and indicate the potential for fundamental oscillations up to about 1 THz. These results are consistent with a lumped‐element equivalent circuit model of the RTD. The model shows that the maximum oscillation frequency of the GaAs/AlAs RTDs is limited primarily by series resistance, and that the power density is limited by low peak‐to‐valley current ratio.
Capability of schottky‐diode multipliers as local oscillators at 1 THz
Authors: Räisänen Antti , Sironen Mikko 
Published: July 2007

AbstractExtensive studies on the theoretical performance of Schonky‐varactors and varistors as multipliers of a frequency around 100 GHz to the submillimeter region (400‐1200 GHz) in various direct and cascaded configurations have been carried out using harmonic balance analysis. Because of high circuit losses (≥10 dB) in a multiplier chain producing 1 THz, the output power seems to stay at or below 100 μW even in the best multiplier configurations when the available input power at 100 GHz is 50 mW.
Energy propagation with phase velocity in a waveguide
Authors: Giakos George C. , Ishii T. Koryu 
Published: July 2007

AbstractTransit‐time measurements of the leading edge of pulse‐modulated microwaves propagating in a waveguide have been performed in time domain. These measurements show that a part of the energy associated with the leading edge of the pulse propagates with a phase velocity exceeding the intrinsic velocity in free space. Calibration techniques and repeated measurements confirm this phenomenon.
Normal‐mode synthesis of N‐coupled coplanar stripline structures
Authors: Faria J. A. Brandão 
Published: July 2007

AbstractNormal modes of n‐coupled stripline structures can be constructed out of a set of generating modes. For coplanar structures a proper choice of the generating set may be based on tridiagonal symmetric Toeplitz L and C matrices. The relationship between the normal‐mode set and the generating‐mode set is established by resorting to standard first‐order perturbation theory results. A numerical example, involving a shielded coplanar five‐line structure (n = 5) is provided for demonstration purposes.
Thermal behavior of wavelength demultiplexers monolithically integrated on InGaAIAs/InP
Authors: Morasca S. , De Bernardi C. , Rigo C. , Stano A. , Croston I. R. 
Published: July 2007

AbstractAn experimental and theoretical analysis of the thermal behavior of wavelength demultiplexers, based on the two‐mode interference principle, integrated on InGaAlAs epitaxially grown by molecular beam epitaxy on InP, is presented. The tuning characteristics of these devices are determined by the superposition of two mechanisms: a pure thermo‐optic effect an an elasto‐optic effect, caused by induced stress. The former is responsible for a shift in the spectral characteristics of about 0.1 nm °−1, while the latter can lead to a much higher temperature sensitivity, up to 1 nm °−1 or more.
Identification of a target in presence of ground clutter using polarization
Authors: Bhattacharyya Asoke K. 
Published: July 2007

AbstractThis article examines the polarimetric method of identification of a target in the presence of ground clutter. The clutter is modeled as a two‐layer random medium. The complex scattering matrix for the clutter is obtained by using Born approximations carried to the second order to extract the crosspolarized scattered fields. The test target used is a loop of conducting wire oriented arbitrarily. It is found that the choice of polarization is one of the key factors if one has to identify targets in presence of clutter. This work does not take into account the mutual coupling between the target and the clutter sources. The important results are analyzed and discussed.
Conversion gain and stability of a resonant tunneling diode harmonic mixer
Authors: Krishnamurthi K. , Conn D. R. 
Published: July 2007

AbstractBased on the negative differential resistance (NDR) in the current‐voltage characteristic of the resonant tunneling device (RTD), various applications have been proposed. Circuit considerations are, in most cases, the limiting factors for high‐frequency applications. Stability criteria for the RTD subharmonically pumped mixer are investigated in this article. Improvements needed for the RTD devices in subharmonically pumped mixer applications are suggested.
III‐V monolithic resonant photoreceiver using local epitaxy and large lattice mismatch material
Authors: Aboulhouda S. , Vilcot J. P. , Razeghi M. , Decoster D. , Francois M. , Maricot S. , Aboudou A. 
Published: July 2007

AbstractIt is shown that local and large lattice mismatch epitaxies could be useful techniques for the fabrication of optoelectronic integrated circuits. As an example, we fabricated a monolithic resonant photoreceiver which associates a long‐wavelength metal‐semiconductor‐metal photodetector, a GaAs MESFET preamplifier, and an inductor. The GaAs/GalnAs heteroepitaxy needed for the photodetector was selectively grown using a SiO2 mask and the entire circuit was fabricated on a silicon substrate. Compared to a PIN photodiode loaded with a 50‐Ω resistor, more than 10 dB gain was measured at 7 GHz in a microwave optical link.
Evaluation of dispersions penalty in an optical coherent PSK transmission system
Authors: Tang XiongYan , Ye PeiDa 
Published: July 2007

AbstractA transmission system model suitable for analyzing both chromatic dispersion and polarization dispersion effects on any coherent optical transmission systems is proposed. Applying this model, the waveform distortion due to both dispersions is calculated for a coherent PSK signal. The dispersions penalty in a coherent PSK system and in a coherent CPFSK system is compared.
Analysis of broadside coupled cylindrical suspended microstrip lines using conformal mapping techniques
Authors: Reddy C. Jagadeswara 
Published: July 2007

AbstractCylindrical striplines and microstrip lines have recently been investigated due to their applications as feed networks of patch antennas on curved surfaces. This letter analyzes the broadside coupled cylindrical suspended microstrip lines using conformal mapping technique. Closed‐form expressions for even‐ and odd‐mode characteristic impedances are obtained. This analysis can also be extended to warped broadside coupled suspended cylindrical microstrip lines.
AIGaAs/GaAs power MISFET with 0.5 W/mm at 30 GHz
Authors: Bonte B. , Amairi A. , Crosnier Y. , Salmer G. 
Published: July 2007

AbstractThis article deals with the application of the AlGaAs‐GaAs DMT principle to the millimeter wave range. It is based on two technological realizations and related characterizations. An Idss of 700 mA/mm and a 10‐12‐V breakdown voltage are demonstrated. Power measurements indicate an output‐power capability of about 0.5 W/mm at 30 GHz.
Far‐field radiation from step junctions in biaxially anisotropic slab waveguides
Authors: Ho T. Q. , Beker B. 
Published: July 2007

AbstractIn this article far‐field radiation properties of step discontinuities on biaxially anisotropic slab waveguides are examined. The stationary phase method is applied to obtain the asymptotic form of the far‐field expressions, which are derived based on the transmission coefficient of the radiation mode. The analysis yields data that agree well with those previously published for special cases of isotropic slabs. The newly calculated results for far‐field radiation patterns of step junctions between biaxially anisotropic waveguides are presented for several combinations of tensor element parameters.
Simple and efficient analysis for a slot‐coupled patch antenna with a microstrip line feed
Authors: Yang Rugui , Lo Y T. , Aksun M. I. , Chuang S. L. 
Published: July 2007

AbstractIn this paper, a simple and eficient analysis f o r slot‐coupled microstrip antennas with a microstrip line feed is developed, using the cavity‐model theory. The computed results are found in excellent agreement with the experimental data.
Numerical analysis of brillouin amplifiers for use in self‐homodyne detection
Authors: Ronghui Feng , Peida Ye 
Published: July 2007

AbstractAn analysis of Brillouin amplifiers (BA) for use in self‐homodyne detection is given considering the pump depletion and the frequency dependence terms. Numerical calculated results shows that operating a BA in the saturated region will give better performance than in the linear region, and the most economic fiber length and pump power can be selected to obtain optimum characteristics of BA.
The effect of spatial hole burning on FM response in DFB laser diodes
Authors: Jianping Zhang 
Published: July 2007

AbstractIn this article, the factors of aP and δP are introduced to describe the effects of all optical field longitudinal nonuniformity on the threshold condition. The rate equation model, including spatial hole burning, is established. The two factors are calculated from the rate and coupled mode equations and analytical expressions of FM responses are derived. FM responses of DFB laser diodes are also analyzed numerically.
High‐power, low‐recovery‐time switched pin diode duplexer at Ku band
Authors: Sarkar B. K. , Prasadh S. S. , Gupta S. 
Published: July 2007

AbstractHigh‐power duplexer consisting of a four‐port ferrite junction circulator and two‐stage switched PIN diode limiter with appropriate driver circuit is designed and developed for a low‐recovery‐time requirement. Insertion loss of 1.5 dB, isolation of 70 dB and recovery time of 40 ns are achieved at a 10‐KW peak, 200‐ns pulsewidth at Ku band.
Investigation of radiation and surface‐wave losses at compensated microstrip T junctions and bends at near‐millimeter‐wave frequencies
Authors: Lin C. C. 
Published: July 2007

AbstractThis article presents the results of an experimental investigation on the radiation and surface‐wave losses at the microstrip discontinuities such as compensated symmetrical T junctions and bends at near‐millimeter‐wave frequencies. Reflection and transmission losses of samples containing those discontinuities with fine geometrical differences have been measured. The reduction of those losses with the use of smooth T junctions and bends is demonstrated.
Wide‐band printed dipole antenna
Authors: Dey Supriyo , Aanandan C. K. , Jose K. A. , Monahan P. , Nair K. G. 
Published: July 2007

AbstractThe design and development of an L‐band printed dipole antenna, optimized for wide‐band applications near first resonance, is reported. This design has achieved more than 48% impedance bandwidth (VSWR 2:1), without degrading its overall radiation efficiency.
Linear analysis of sheet beam planar grating and dielectric cerenkov maser amplifiers
Authors: Joe J. , Chang S. F. , Scharer J. E. , Booske J. H. 
Published: July 2007

AbstractWe consider a planar grating and partially filled dielectric as slow wave structures for a low‐voltage electron sheet beam, moderate power Cerenkov amplifier. The small signal growth rate for both slow wave structures with partially filled sheet beams are evaluated. The results are compared at 35 and 60 GHz. We find that both configurations offer attractive and comparable gain at relatively low beam voltages and can be developed as moderate power sheet beam sources.
Self‐trapping of vibrational energy
Authors: Scott Alwyn C. 
Published: July 2007

AbstractThe current status of Davydov's soliton mechanism for the storage and transport of vibrational energy in biomolecules is reviewed. It is concluded that this mechanism should be viable under normal physiological conditions. Davydov's analysis is extended to the discrete self‐trapping (DST) system which is a convenient model for exploring the relations between classical anharmonic effects (solitons, local modes, chaos, etc.) and their quantum descriptions.
Stability and soliton via modified nonlinear schrödinger equation
Authors: Li Guifang , Seshadri S. R. 
Published: July 2007

AbstractThe evolution of nonlinear dispersive waves in weakly and cubically nonlinear media is shown to be governed by a modified nonlinear Schrödinger equation. The linear stability of the plane‐wave solution and the soliton solution are investigated using the modified governing equation. The height of the new soliton is a function of both its width and velocity.
Crystal‐clad fiberoptic polarizer
Authors: Wang Zi Hua , Wang Dao Gang , Seshadri S. R. 
Published: July 2007

AbstractTheoretical analysis, design considerations, and manufacturing techniques of a fiber‐optic polarizer made of crystal‐clad single‐mode fiber are discussed. The measured extinction ratio exceeds 30 dB over a wide bandwidth and is 37 dB at 1.53‐μm wavelength. The excess loss is less than 1 dB. The device is 3x3x20 mm in size.
The implementation of a high accuracy optical measurement technique of particular interest to miniature optics
Authors: Ghafouri‐Shiraz H. , Mcloughlin Ian Vince 
Published: July 2007

AbstractThis letter details an implementation of optical coherence domain reflectometry (OCDR) which is capable of resolving distances of less than 10μ. Simulated and experimental data have been used to evaluate the effects of different parameters on a future system, allowing the prediction of OCDR capabilities under different arrangements, and the determination of its suitability in different application areas.
Thermal analysis of etched‐well surface‐emitting diode lasers
Authors: Nakwaski Wlodzimierz , Osiński Marek 
Published: July 2007

AbstractA new self‐consistent thermal‐electrical model of etched‐well GaAs/ AlGaAs vertical‐cavity surface‐emitting lasers is developed. The model features a realistic distribution of heat sources and two‐dimensional current‐ and heat‐flux spreading. It is shown that the P‐AlGaAs layer represents a major source of Joule heating that may easily exceed the active‐region heating. A moderate increase of the P‐AlGaAs layer doping is shown to be very effective in reducing the excessive heating.
Field approximations at thin‐wire junctions for the finite‐difference time‐domain method
Authors: Boonzaaler J. J. , Pistorius C. W. I. 
Published: July 2007

AbstractApproximations for the circumferential magnetic fields at right‐angled junctions are derived and validated by computing the radiation patterns of a square‐loop antenna by means of the finite‐difference time‐domain (FD‐TD) method. The radiated time‐domain fields are transformed to the frequency domain and then compared to the frequency domain results obtained from the method of moments.
Radiated fields of microstrip patches at arbitrary angular positions
Authors: Wahid P. F. , Christodoulou C. G. , Rutkowski K. A. 
Published: July 2007

AbstractThis article investigates the radiation characteristics of microstrip patch antennas located at arbitrary angular positions. The aperture method was employed to determine the radiated far field of the patch. A circular arrangement of the patch antennas was studied. The effect of the array configuration on the radiation characteristics are presented and analyzed.
Analysis of second harmonic generation in organic crystal‐cored fibers for various cladding materials
Authors: Ghafouri Shiraz H. , Ozsoy S. 
Published: July 2007

AbstractThe second harmonic power generation efficiency (SHPGE) obtained under phase‐matching conditions in organic crystal‐cored fibers having different cladding materials have been investigated. It has been found that a very high SHGPE can be obtained under certain conditions.
Analysis of waveguide‐to‐microstrip transition
Authors: Li Dawei , Wang Rongjie 
Published: July 2007

AbstractThe analysis method for the antipodal finline waveguide‐to‐micro‐strip transition is presented in the article. The revised empirical expressions for the transition from nonoverlapped antipodal finline to overlapped one are given. We design a Ka‐band broadband waveguide‐to‐microstrip transition using this method. The experimental results have a good agreement with the theoretical ones.
Characteristic features of a leaky‐wave microstrip antenna on cylindrical surfaces
Authors: Mitkees A. A. , Abdallah E. A. , Hamdy S. M. , Elsohly A. A. 
Published: July 2007

AbstractAntenna parameters of microstrip leaky‐wave antennas are highly affected by the complex nature of the propagation factor. Beam direction, beamwidth, gain, side‐lobe level, efficency, and input impedence for different lengths and linewidths are investigated. The antenna showed good performance and promising features. Efficiency up to 90%, – 18‐dB side‐lobe level, 9‐dB gain, and 20° beamwidth can be obtained.
How does atmospheric turbulence affect threshold detection in optical channels?
Authors: Fares Doaa A. 
Published: July 2007

AbstractOptical communication through the earth's atmosphere offers a great contribution in increasing our data transmission capability. In addition to background radiation and photodetector random gain, the performance of such a channel is highly affected by atmospheric turbulence along its propagation path. In this article, threshold detection for this channel is studied under different turbulence levels, concluding the optimum threshold setting for different alphabet sizes.
Signal power requirements in indoor directive and diffuse infrared communication channels
Authors: Georgopoulos Chris J. , Prentzas Lampros K. 
Published: July 2007

AbstractThis article deals with the calculation of the minimum required emitting infrared (IR) signal power at the presence of background ambient light, taking into account thermal noise and receiver input amplifier noise. A baseband PCM wireless IR system is assumed and results are obtained for both directive and diffuse IR transmission channels.
Measurements of the minimum reflection signature of pmma fiber splices
Authors: Lawson C. M. , Michael R. R. , Finn G. M. , Dressel E. M. , Harmony D. W. 
Published: July 2007

AbstractThe minimum reflection signature of polished plastic fiber splices has been measured using time domain reflectrometry. Predominant splice reflection sources due to surface roughness, inexact index matching, and fiber core misalignment were eliminated. An intrinsic reflection signature on top of the Rayleigh floor is clearly observable in all tested fibers.
A broadband dual slant strip grating for elimination of specular reflection of em waves
Authors: Wilson Gomez L. , Ajaikumar V. , Jose K. A. , Mohanan P. , Nair K. G. 
Published: July 2007

AbstractConventional corrugated surfaces and strip gratings are used for eliminating specular reflections from a conducting surface for TE or TM polarization waves. This article presents the development of a dual slant strip grating for the elimination of specular reflections from conducting surfaces for both TE and TM polarizations, with an enhancement in bandwidth. Perfect blazing for n= ‐1 spectral order is also provided by the system.
Microwave bandpass filters using series‐cascaded sections of microstrip line
Authors: Bernhard Jennifer Truman , Joines William T. 
Published: July 2007

AbstractA quarter‐wavelength‐coupled filter with prescribed frequency response is presented which uses a novel configuration of series‐cascaded microstrip lines as its resonating components. Design equations are obtained from ABCD parameters, with approximations taken to account for the double resonance characteristics of the filter's constituent networks. Experimental and theoretical results agree closely.
Simulation of the erbium‐doped fiber amplifier characteristics
Authors: Ghafouri‐Shiraz H. , Shum P. 
Published: July 2007

AbstractThe dependence of the erbium‐doped optical amplifier gain upon the fiber length, output signal, and pump power have been theoretically investigated for two pumping wavelengths of 0.98 and 1.48 μm. The analytical results are in fairly good agreement with the reported measured data.