bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave imaging in angular spectral domain based on the improved Newton's procedure
Authors: Park Cheon‐Seok , Park Seon‐Kyu , Ra Jung‐Woong
Published: July 2007

An iterative inversion in angular spectral domain based on the quasi Newton's procedure is presented. Angular spectral‐domain reconstruction is shown to be more insensitive to the noise in the scattered field than configuration domain reconstruction. It is also shown by closed‐form solution of a homogeneous circular cylinder that the local minima hindering this inversion process exist in the cost function. © 1994 John Wiley & Sons, Inc.
Analysis of a broadband hemispherical dielectric resonator antenna with a dielectric coating
Authors: Wong Kln‐Lu , Chen Nan‐Cheng
Published: July 2007

A probe‐fed hemispherical dielectric resonator antenna with a dielectric coating is investigated rigorously by using a Green's function formulation. Numerical results for the input impedance at TE111 mode are calculated. It is found that, by coating the dielectric resonator antenna with a dielectric material having a relative permittivity about half that of the dielectric resonator antenna, the impedance bandwidth of the antenna can be significantly improved. This dielectric coating here serves as a transition region between the wave inside the dielectric resonator antenna and the free‐space wave, and thus can increase the impedance bandwidth of the antenna. A broadband dielectric resonator antenna can thus be obtained. © 1994 John Wiley & Sons, Inc.
MOCVD growth and ultrafast photoluminescence in GaAs and InAs freestanding quantum whiskers—a review
Authors: Viswanath A. Kasi , Hiruma K. , Yazawa M. , Ogawa K. , Katsuyama T.
Published: July 2007

Nanometer‐size quantum whiskers of InAs and GaAs have been fabricated by low‐pressure MOCVD. Time‐integrated and time‐resolved photoluminescence of GaAs wires of diameters 200, 100, 70, and 50 nm have been studied. The temperature dependence of PL peak energy was found to follow the same variation as the bandgap of GaAs, and Varshni's theory has been used to explain the temperature dependence. The main channel of radiative recombination was found to be due to free excitons. The nonuniformity in diameter and lattice phonon interactions were considered to understand the origin of the linewidth. From the time‐resolved PL the surface recombination lifetimes were measured directly. Surface recombination velocities were evaluated and were correlated to wire diameter. The quantum‐size‐dependent spatial part of the electronic wave function was thought to be responsible for the variation of surface recombination velocity with diameter. Surface treatment with sulphur reduced the surface depletion layer, as evidenced from the time‐resolved and time‐integrated spectra. The carrier lifetime was in picosecond time scales at 7 K and increased with temperature, thus confirming the quantum confinement effects. The polarization experiments revealed the one‐dimensional nature of quantum whiskers. © 1994 John Wiley & Sons, Inc.
Theoretical calculation of optical gain and threshold current density in strained in1−XGaxAs/InP quantum‐well lasers using strain‐dependent conduction‐band and valence‐band structures (invited paper)
Authors: Sugawara Mitsuru , Yamazaki Susumu
Published: July 2007

We theoretically calculate the optical gain of In1−xGaxAs/InGaAsP strained quantum wells on (001) InP substrates based on strain‐dependent conduction‐band and valence‐band structures. Using the calculated gain, we estimate threshold current density of the strained quantum‐well lasers. We show that both biaxial compressive and tensile strains can lower the threshold current density by ½–⅓, and clarijv the mechanism for the reduction. © 1994 John Wiley & Sons. Inc.
A modification to a simple field model of the TE01δ mode of the parallel‐plate open dielectric resonator
Authors: Sheen Jyh , Bhalla A. S. , Cross L. E.
Published: July 2007

A modification to the field expressions on the simple Itoh and Rudokas model for the TE01δ mode of the parallel‐plate open dielectric resonator is given. This modification is justified by the dramatic improvement in the accuracy of resonant frequency prediction. © 1994 John Wiley & Sons, Inc.
Input impedance of a probe‐fed superstrate‐loaded cylindrical‐rectangular microstrip antenna
Authors: Ke Shyh‐Yeong , Wong Kin‐Lu
Published: July 2007

A probe‐fed superstrate‐loaded rectangular microstrip antenna mounted on a cylindrical body is investigated by using a full‐wave analysis and a moment‐method calculation. Numerical results for the input impedance are calculated and the numerical convergence of the moment‐method calculation is also shown. Variations of the input impedance with the superstrate thickness and curvature radius are presented and discussed. Both the HE01 and HE10 modes are studied. © 1994 John Wiley & Sons, Inc.
Structural impact on the below‐threshold spectral behavior of three‐phase‐shift (3PS) distributed feedback (DFB) lasers
Authors: Ghafouri‐Shiraz H. , Lo B. S. K.
Published: July 2007

The impacts of the values of phase shifts and the corresponding phase‐shift positions (PSP) on the spontaneous emission spectra of a three‐phase‐shift (3PS) distributed feedback (DFB) laser have been analyzed at below threshold. Side‐mode suppression of more than 25 dB is achieved with a proper selection of phase shifts and their positions. The use of the transfer matrix method (TMM) in the analysis reveals promising potential for improving and optimizing the structural design of the 3PS DFB lasers in both the below and lasing threshold applications. © 1994 John Wiley & Sons, Inc.
Ellipsoidal and hyperboloidal lens aperture functions for computation of fraunhofer diffraction patterns
Authors: Lazarus M. J.
Published: July 2007

The illumination profile functions of ellipsoidal and hyperboloidal dome refracting lenses are obtained in forms suitable for direct computation of diffraction patterns. The effects of anisotropic radiation from the primary source and intensity distortion on refraction are treated. The resultant Fraunhofer diffraction lobe structures are compared. © 1994 John Wiley & Sons, Inc.
Analysis and design of the class E amplifier with nonzero on resistance
Authors: Li Chi‐Hung , Yam Yu‐On
Published: July 2007

A modified method is derived to analyze the optimum performance of the Class E amplifier with nonzero ON resistance. The required circuit component values can be calculated directly by this method. No direct‐search optimization of the component value is required, so computation time is saved. In addition, nonzero ON resistance of the transistor can be used to estimate the power loss in the transistor, and thus the collector efficiency of the amplifier can be calculated more accurately. © 1994 John Wiley & Sons, Inc.
Characterization of crossing strips laid on a semiconducting substrate using the transverse resonance method
Authors: Saidi K. , Seguinot C. , Pribetich P. , Kennis P.
Published: July 2007

In this contribution we propose an original extension of the wellknown transverse resonance method to the analysis of crossing strips laid on semiconducting substrates. Our first results involve the resonance of one isolated strip on a homogeneous or multilayered semiconducting substrate. They demonstrate that low‐loss MMIC structures can be analyzed with the transverse resonance method. Further investigation is necessary in order to determine the validity of this method when determining the equivalent circuit of crossing strips laid on semiconductors. © 1994 John Wiley & Sons, Inc.
A numerical absorbing boundary condition for finite‐difference and finite‐element analysis of open structures
Authors: Boag Amir , Boag Alona , Mittra Raj , Leviatan Yehuda
Published: July 2007

In this article we present a novel approach to deriving local boundary conditions that can be employed in conjunction with the finite‐difference and finite‐element methods (FD/FEM) to solve electromagnetic scattering and radiation problems. The key step in this approach is to derive linear relationships that link the values of the field at the boundary grid points to those at the neighboring points. These linear relationships are satisfied, to within a certain tolerance, by all of the outgoing wave components. They can thus be used in lieu of the FD/FEM equations employing the usual absorbing boundary conditions for the boundary points. The present approach not only provides a simple way to derive an accurate boundary condition for mesh truncation, but also preserves the banded structure of the FD/FEM matrices. © 1994 John Wiley & Sons, Inc.
Comparison of insertion losses of s‐shaped optical waveguide bends
Authors: Yamauchi Junji , Saito Osamu , Ikegaya Morihiko , Sawamoto Takehito , Nakano Hisamatsu
Published: July 2007

The beam‐propagation method is used to analyze the insertion losses of S‐shaped dielectric slab bends. Two circular arcs, sine‐generated, and cosine‐generated curves are compared and discussed. Calculation shows that the S‐shaped bend composed of two circular arcs with constant curvature gives excellent performance, provided the core is properly offset. © 1994 John Wiley & Sons, Inc.
Full‐wave analysis of mutual coupling between cylindrical‐rectangular microstrip antennas
Authors: Ke Shyh‐Yeong , Wong Kin‐Lu
Published: July 2007

The mutual coupling between two probe‐fed cylindrical‐rectangular microstrip antennas is studied by using a full‐wave analysis and a moment‐method calculation. Numerical results of the E‐plane and H‐plane mutual coupling coefficients for the cylindrical microstrip antennas with different curvature radii are presented, and the curvature effect on the mutual coupling is studied. © 1994 John Wiley & Sons, Inc.
Radiation quality factor and resonant resistance of rectangular microstrip antennas
Authors: Güney K.
Published: July 2007

A new very simple radiation quality factor expression is presented for a rectangular microstrip antenna. The theoretical resonant resistance results obtained by using this new radiation quality factor expression are in very good agreement with the experimental results available in the literature. © 1994 John Wiley & Sons, Inc.
Transverse electric modes in shielded strip line
Authors: Tsitsos S. , Gibson A. A. P.
Published: July 2007

Triplate shielded strip line is an important low‐loss, high‐power transmission line geometry widely used in beam‐former arrays. Accurate design information on higher‐order mode onset frequencies is presented here using finite‐element techniques and an experimental cavity method. Field plots and some design recommendations are included for completeness. © 1994 John Wiley & Sons, Inc.
Low‐cost antennas for direct broadcast satellite radio
Authors: Wu T. K. , Huang J.
Published: July 2007

Two omnidirectional and circularly polarized low‐gain antennas (the crossed drooping dipole and the TM21‐mode circular patch antenna) are developed for direct broadcast satellite radio (DBSR) outdoor mobile terminal applications. Two medium‐gain circularly polarized microstrip patch arrays [one uses the conventional circular polarization (CP) feed and the other uses the sequentially arranged CP feed techniques] are also developed to provide at least 12–dBic peak gain for DBSR indoor fixed terminal applications. The sequentially arranged CP fed array has a better CP performance over a broader bandwidth than the conventionally fed array. All the antennas are small in size/mass and inexpensive in fabrication cost. The patch antennas also have a low profile. © 1994 John Wiley & Sons, Inc.
A finite‐element analysis of bending dielectric waveguides with reflection walls
Authors: Chung Shyh‐Jong
Published: July 2007

The finite‐element method together with the Green's‐function technique is employed to tackle the scattering problems of bending dielectric waveguides with reflection walls. The influences of the frequency, the ratio of waveguide widths, and the length of the reflection wall on the scattering characteristics of 90° and 120° bends are presented. © 1994 John Wiley & Sons, Inc.
Computation of the equivalent inductive circuit for an arbitrary number of e‐plane metal inserts in rectangular waveguides
Authors: Liu Ce
Published: July 2007

An explicit formula for computing the equivalent inductive circuit parameters of E‐plane metal inserts is derived. The number of inserts is arbitrary. The thickness of each insert is taken into account. An equivalent T network is used to model the E‐plane discontinuity. The dielectric constant between the metal inserts can be different. A mode‐matching method is used in the formulation. © 1994 John Wiley & Sons, Inc.
Reflection and transmission for planar structures of uniaxial chiro‐omega media
Authors: Wenyan Yin , Wengbing Wang
Published: July 2007

The generalized spectral‐domain‐exponential matrix technique is used for analyzing the reflection and transmission characteristics of a grounded and ungrounded uniaxial chiro‐omega slab, respectively. Parameter studies are performed to investigate the effects of changing the orientations of ω elements on the reflection and transmission coefficients. The potential applications of uniaxial chiro‐omega media for microwave and millimeter wave regimes are pointed out. © 1994 John Wiley & Sons, Inc.
Rapid approximation of conducting problems using a dual image approach
Authors: Kastner Raphael
Published: July 2007

Equivalent surface electric and magnetic sources can generate an approximate far field scattered off a conductor. These are exact (electric) and approximate (magnetic) images of the exciting equivalent sources. A physical‐optics‐type computation with improved accuracy, which also accommodates concave surfaces, is achieved. © 1994 John Wiley & Sons, Inc.
Microwave characterization of slot line and coplanar strip line on high‐resistivity silicon for a slot antenna feed network
Authors: Simons Rainee N. , Taub Susan R. , Lee Richard Q. , Young Paul G.
Published: July 2007

This article presents the effective dielectric constant (ϵeff) and attenuation constant (α) of an unshielded slot line and a coplanar strip line on a high‐resistivity (5000–10,000 ω‐cm) silicon wafer. The ϵeff(dc to 40 GHz) and α (dc to 26.5 GHz) in each case are determined from the measured resonant frequencies and insertion loss of a ring resonator. The measurements are carried out at room temperature. No dc bias is applied to the transmission lines. The attenuation for slot line and coplanar stripline on silicon are compared with microstrip line and coplanar waveguide on other semiconductor substrate materials. Lastly, a microstrip‐to‐slot‐line transition and its use in a feed network for linearly tapered slot antennas is demonstrated. © 1994 John Wiley & Sons, Inc.
Bandwidth of a resonant rectangular microstrip antenna
Authors: Güney K.
Published: July 2007

A new very simple curve‐fitting expression is presented for the bandwidth of resonant rectangular microstrip antennas. It is derived from numerical results available in the literature, and is useful for many engineering purposes. The results obtained by using this expression are in conformity with those reported elsewhere. © 1994 John Wiley & Sons, Inc.
Determination of the open‐end discontinuity and resonance frequency of a suspended microstrip using the slr technique
Authors: Verma A. K. , Hassani Sadr G.
Published: July 2007

This article presents a model, called the EKJK model, to determine the open‐end discontinuity of a suspended microstrip line. The accuracy of the model is confirmed within 2% compared to the computed resonance frequency by this model and by the SDA. The effects of the width of the line and top shield on the resonance frequency of the suspended line resonator are also reported. © 1994 John Wiley & Sons, Inc.
Linear constitutive relations for beltrami – maxwell postulates
Authors: Lakhtakia Akhlesh
Published: July 2007

Constitutive relations for a spatially local and nonhomogeneous, temporally causal, linear bianisotropic medium without memory are given for use with the Beltrami‐Maxwell postulates. © 1994 John Wiley & Sons, Inc.
Resonant frequency of a tunable rectangular microstrip patch antenna
Authors: Güney K.
Published: July 2007

The resonant frequency of a coaxial‐probe‐fed rectangular microstrip antenna tuned by a number of passive metallic posts suitably placed within the antenna's boundary is obtained by using the resonant frequency expression in the absence of the post. The resonant frequency in the absence of the post is calculated from the fringing field extension and effective relative permittivity expressions. The theoretical resonant frequency results of tunable rectangular patch antenna obtained by using this method are in good agreement with experimental results available in the literature. © 1994 John Wiley & Sons, Inc.
Frequency selective surface design for submillimetric demultiplexing
Authors: Cahill R. , Parker E. A.
Published: July 2007

Efficient diplexing of bands centered at 200 and 600 GHz has been achieved using two types of frequency selective surfaces. Computer and measured results are used to assess their suitability as beam splitters in a submillimeter‐wave quasioptical radiometer. © 1994 John Wiley & Sons, Inc.
Numerical analysis of an asymmetric nonlinear directional coupler
Authors: Yasumoto Kiyotoshi , Maeda Hiroshi
Published: July 2007

The power transfer characteristics of an asymmetric nonlinear directional coupler (NLDC), which consists of a nonlinear waveguide with a core of Ken‐like medium and a linear waveguide, are analyzed using the beam propagation method. The numerical results demonstrate that the asymmetric NLDC is useful for constructing an optical power filler. © 1994 John Wiley & Sons, Inc.
The limitation of the parameters of a one‐bit phase shifter based on s‐n transition in HIGH‐Tc superconductors
Authors: Vendik I. B.
Published: July 2007

Evaluation of the limiting characteristics of one‐bit reflection‐type phase shifters based on the S‐N transition in high‐Tc superconducting (HTSC) films is done, taking into account real parameters of the HTSC films. The results can be used for the design and optimization of digital phase shifters. © 1994 John Wiley & Sons, Inc.
A quasistatic method for the characterization of stratified dielectric materials using an open‐ended coaxial probe
Authors: Misra Devendra K. , McKelvey Jeffrey A.
Published: July 2007

An open‐ended coaxial probe method has been investigated for the characterization of a stratified dielectric medium. A static formulation for its aperture capacitance is employed for this purpose. This approach is found to be fairly accurate in the frequency range of 500 MHz‐2 GHz. It can be applied for monitoring the delamination or other defects in sheet materials by measuring the permittivity profile of the dielectric samples. © 1994 John Wiley & Sons, Inc.
On polarizability properties of bianisotropic spheres with noncomplete magnetoelectric dyadics
Authors: Sihvola Ari H.
Published: July 2007

The polarizability expressions for bianisotropic scatterers are often complicated expressions of the material parameters. This communication treats the question of how the dyadic inversion operations needed in the expressions can be carried out such that they perform well. The particular polarizabilities of the biaxial chiral sphere are shown in component form. © 1994 John Wiley & Sons, Inc.
Reflection and mutual coupling in a special kind of parallelplate phased antenna arrays
Authors: Janssen J. M. W. M. , Jeuken M. E. J.
Published: July 2007

An infinite phased antenna array of plane parallel plate structures, where every other structure is short circuited at a distance t from the aperture, has been investigated. In the analysis, a modal matching technique has been applied. It can be concluded that both reflection and mutual coupling can be reduced considerably by properly selecting the choke depth t and the material inside the plane parallel plate structures and the chokes (er). © 1994 John Wiley & Sons, Inc.
A finite‐difference time‐domain method using whitney elements
Authors: Chan C. H. , Sangani H. , Yee K. S. , Elson J. T.
Published: July 2007

A new finite‐difference time‐domain method is proposed. The key feature of this method is the use of Whitney‐element interpolation functions so that field values can be updated explicitly either by the differential or the integral form of Maxwell's equations. Numerical results are given for a 2D parallel‐plate waveguide. © 1994 John Wiley & Sons, Inc.
A novel broadband rectangular microstrip antenna element
Authors: Kara Mehmet
Published: July 2007

The design, fabrication, testing, and analysis of a new broadband rectangular microstrip antenna element resonating at 7.200 GHz is introduced and discussed. Measured data on the performance characteristics of the new antenna element are presented and compared with the characteristics of a conventional microstrip antenna element having the same dimensions. © 1994 John Wiley & Sons, Inc.
Broadband cylindrical‐rectangular microstrip antennas using gap‐coupled parasitic patches
Authors: Ke Shyh‐Yeong , Wong Kin‐Lu
Published: July 2007

A broadband cylindrical‐rectangular microstrip antenna using two parasitic patches gap coupled to its radiating edges is studied by using a full‐wave analysis and a Galerkin's moment‐method calculation. Results indicate that, with parasitic patches, an antenna bandwidth greater than two times that of a single cylindrical‐rectangular patch antenna can be obtained. Details of the numerical results for different curvature radii and gap spacings are presented. © 1994 John Wiley & Sons, Inc.
MMIC broadband braided microstrip coupler
Authors: Willems David A.
Published: July 2007

This article presents a broadband quadrature coupler realized using a novel braided microstrip structure that consists of 64 air‐bridge crossovers. The test results of the 2.5–8‐GHz single‐section coupler fabricated on a 125‐μm‐thick GaAs substrate are presented. This coupler achieved better than 17‐dB return loss, 11 dB of isolation and ±0.75 of amplitude variation over the almost 2‐octave bandwidth. This bandwidth and performance are the best reported for a braided microstrip coupler. © 1994 John Wiley & Sons, Inc.
Automatic mesh generator based on self‐organizing finite‐element tessellation for three‐dimensional electromagnetic field problems
Authors: Jeong Bong‐Sik , Lee Soo‐Yound
Published: July 2007

A three‐dimensional SOFT (self‐organizing finite‐element tessellation) mesh generator, based on self‐organizing topology‐preserving feature maps, is developed for electromagnetic field problems. A user‐supplied probability function controls the density of the graded mesh, and local mesh refinements are easily incorporated. © 1994 John Wiley & Sons, Inc.
Analysis of dielectric‐covered radiating slots in the ground plane of a microstrip line
Authors: Wong Kin‐Lu , Su Hsin‐Cheng
Published: July 2007

The dielectric overlay effects on the impedance properties of a radiating slot in the ground plane of a microstrip line are studied by using the reciprocity theorem and a moment‐method calculation. The Green's functions for the dielectric‐covered microstrip line‐fed radiating slot are given, and the expression for the slot impedance is shown. Numerical convergence of the moment‐method calculation using, respectively, piece‐wise sinusoidal basis functions and rooftop basis functions is discussed. Numerical results for the slot impedance as a function of overlay thickness and permittivity are presented and discussed. © 1994 John Wiley & Sons, Inc.
Fast multipole method solution using parametric geometry
Authors: Song J. M. , Chew W. C.
Published: July 2007

The fast multipole method is used to solve the electromagnetic scattering from three‐dimensional conducting bodies of arbitrary shape. The electric field integral equation is discretized by the method of moments. Instead of directly computing the matrix‐vector multiplication, which needs N2multiplications, this approach reduces the complexity to O(N1.5). © 1994 John Wiley & Sons, Inc.
A new face‐centered‐cubic photonic crystal for microwave and millimeter‐wave applications
Authors: Brown E. R. , Agl K. , Dill C. , Parker C. D. , Malloy K. J.
Published: July 2007

Three‐dimensional photonic crystals are fabricated that consist of a face‐centered‐cubic lattice of air atoms embedded in a synthetic dielectric matrix. The crystals are formed by stacking triangular arrays of cylindrical atoms in a close‐packed arrangement. The fabrication technique is much simpler than previous methods and is well suited to producing photonic band gaps in the microwave and millimeter‐wave regions. Microwave measurements provide strong evidence for a photonic band gap between approximately 17 and 18 GHz in a crystal having a volumetric air fraction of 60%. © 1994 John Wiley & Sons, Inc.
Multilevel evaluation of electromagnetic fields for the rapid solution of scattering problems
Authors: Michielssen Eric , Boag Amir
Published: July 2007

A multilevel algorithm is presented for evaluating fields generated by given distributions of electric current. The algorithm can be used to accelerate the solution of scattering problems using the method of moments and/or boundary element methods. The algorithm exploits the limited number of degrees of freedom that characterize a field observed over a domain that is well separated from a source domain. Both the memory requirements and the computational complexity of the algorithm are O(Nslog(Ns)), where Nsis the common number of sources and observation points. The multilevel algorithm can easily be incorporated into existing method‐of‐moments (MoM) programs. A simple physical interpretation of the algorithm is provided. © 1994 John Wiley & Sons, Inc.
A kinoform for the spatial distribution of a gaussian beam at millimeter wavelengths
Authors: Delgado Guillermo F. , Bengtsson Jörgen
Published: July 2007

A kinoform to produce an array of 4 × 4 equal‐intensity Gaussian beams from a single Gaussian beam has been designed, manufactured, and evaluated at 100 GHz. The kinoform was fabricated by milling a Teflon plate, and symmetry of the amplitude distribution and a binary phase control were used to obtain a simple phase relief surface. The measured diffraction efficiency is about 95%. © 1994 John Wiley & Sons, Inc.
Analysis of superconductive interconnects by the finite‐difference‐time‐domain method
Authors: Wang Bing‐Zhong
Published: July 2007

A methodology is described for the analysis on superconductive interconnects. First, the time‐domain impedance boundary condition (TDIBC) of a superconductor is obtained from its frequency‐domain counterpart. Next, discretization of the TDIBC is presented in the context of the finite‐difference—time‐domain (FDTD) technique. The FDTD solutions for a superconductive parallel‐plate transmission line are in good agreement with the exact solutions. Finally, the transmission property of a superconductive via is analyzed by the FDTD method. © 1994 John Wiley & Sons, Inc.
Microstrip‐slot and coplanar waveguide‐slot lines with very high dielectric constant substrates for application in high‐speed optoelectronics
Authors: Carvalho M. C. R. , Margulis W. , Souza J. R.
Published: July 2007

This article shows that the microstrip‐slot line and the novel coplanar waveguide‐slot line printed on substrates with very high dielectric constant (εr = 38 and ε = 80) are ideal for the construction of the microwave circuitry within packages of optoelectronics components. These combined transmission lines allow the realization of impedance levels not achieved with conventional structures on such substrates, due to small, unfeasible transversal dimensions. The spectral domain approach is used in the analysis of the transmission lines. The adequacy of the analysis is confirmed experimentally. © 1994 John Wiley & Sons, Inc.
Slow‐wave characteristics of coplanar meander transmission lines with dielectric substrate
Authors: Görür A. , Karpuz C.
Published: July 2007

We report the reduction factor in velocity of a meander coplanar transmission line on dielectric substrates. A simple analysis of this device that can be used to reduce the size of microwave integrated circuits has been carried out by using CAD packages. A size‐reduction factor of approximately 4–5 has been obtained. © 1994 John Wiley & Sons, Inc.
A new approach to broadband matching for P‐I‐N photodiodes
Authors: Zhu Zhimin , Gillon Renaud , Vorst André Vander
Published: July 2007

Microwave transmission‐line theory has been applied to calculate p‐i‐n photodiode systems in which the carrier transit time, the geometric configuration, and the transmission‐line characteristics were considered. The thickness of the intrinsic layer has been optimized to obtain a wide 3‐dB bandwidth and a maximum gain‐bandwidth product. A simulated result of 40‐GHz bandwidth has been obtained for a device with a 20 × 20 μm2 p‐i‐n area.
Modal cutoff conditions for a chirowaveguide with a chiral core of large annular cross section bounded by dielectric media
Authors: Ganguly Sonali , Singh Kh. S. , Ojha S. P. , Khastgir P.
Published: July 2007

A chirowaveguide with an annular cross section where the chiral region is bounded by dielectric media has been analytically studied for cutoff conditions. The annular guiding region can be looked upon as a bent slab waveguide with a circular curvature. The origin of this curvature may be deliberate or the result of warping due to fabricating defects. The effect of changing chiral admittance on the cutoff conditions is also discussed.
A first‐order, hybrid FEM/MoM approach for the analysis of two‐dimensional structures
Authors: Pekel Ü. , Mittra R.
Published: July 2007

There exist various hybrid techniques that combine the finite element method (FEM) and surface integral equation‐type (SIE) techniques to solve Maxwell's equations for objects located in unbounded regions. In this article a novel first‐order hybrid approach is considered, which combines the conventional FEM and MoM techniques in two distinct phases by using the field solution initially obtained by FEM to modify the incident field expression of the subsequent MoM analysis part.
Scattering from a periodic inhomogeneous medium with a rough interface
Authors: Freni A.
Published: July 2007

A hybrid technique that utilizes the finite‐element method (FEM) and an analytic solution is presented for the analysis of the scattering of a plane wave from a periodic inhomogeneous medium, having arbitrary geometry and material properties. This medium is overlaid with a homogeneous one that presents a rough interface with the space from which the incident plane wave originates. The rough interface is studied with a perturbative method, whereas the inhomogeneous medium is examined with the finite‐element procedure. The two methods are matched imposing the continuity of the fields into the homogeneous medium.
A sparse‐matrix canonical‐grid method for scattering by many scatterers
Authors: Chan C. H. , Tsang L.
Published: July 2007

A new efficient algorithm based on the decomposition of strong and weak interactions among scatterers is proposed. The weak interactions, which account for the majority of the required CPU time and memory, are calculated using a canonical grid with a translation addition theorem. This facilitates the use of FFT and results in an N log N‐type efficiency for CPU and O(N) for memory.
Design of a matrix amplifier using FET‐gate‐width tapering
Authors: d'agostinos Stefano , Paoloni Claudio
Published: July 2007

A MMIC matrix amplifier design based on FETs with tapered gate width is proposed. The Tschebyscheff filter theory is applied to each of the artificial transmission lines composing the matrix amplifier. The improvement of the input and output reflection coefficient and the reduction of the FET's width in comparison to a conventional matrix amplifier with equivalent performance demonstrates the effectiveness of the presented approach.
Analysis of the microstrip yagi antenna by an iterative MPIE formulation
Authors: Bokhari S. A. , Costache G. I.
Published: July 2007

The Letter presents a method for the rigorous analysis of the microstrip Yagi antenna. Using the mixed potential integral equation (MPIE) for patch antennas, the FFT algorithm and the biconjugate gradient iterative method, the solution for the unknown current distribution on the patch is obtained in an efficient manner without requiring the storage of large matrices that typically arise in moment‐method computations. Consequently, the scheme can deal with patches of arbitrary shapes and can handle a very large number of unknowns. Numerical results of input impedance and radiation patterns are compared with measured results.
A technique for solving 2D method‐of‐moments problems involving large scatterers
Authors: Mittra Raj , Varadarajan V.
Published: July 2007

The article demonstrates that a Method‐of‐Moments solution for large, smooth, two‐dimensional scatterers, requiring matrices that are several hundreds to several thousands in size, can be constructed efficiently by using a combination of transformations based upon FFT and partial QR decomposition of off‐diagonal blocks. The primary contribution of the article is to demonstrate that these techniques, applied in tandem, can typically reduce the active RAM requirements by a factor of 60‐100 for moderately large problems, and by as much as 225 (estimated) for matrix sizes around 100,000. It is also estimated that an effective flop rate of about 8‐35 N2 In N to 0.01N3 can be achieved via this transformation. The reduction factors for RAM requirements and the accuracy of the solution are demonstrated for the problem of a 2D elliptic cylinder with a large aspect ratio, requiring matrix sizes up to 10,000.
Sensitivity analysis of the nonorthogonal fdtd method applied to the study of square coaxial waveguide structures
Authors: Navarro Enrique A. , Wu Chen , Chung Paul Y. , Litva John
Published: July 2007

The nonorthogonal finite‐difference‐time‐domain method is applied to the analysis of structures in a square coaxial waveguide to demonstrate the influence of the mesh on the results. The analysis presented provides insight on how best to discretize the computational domain when modeling discontinuities with this method. Three structures, described as 90°, 120°, and 170° bends, are used as examples in our analysis. A comparison is made with results obtained using the FEM method for the 90° bend. The comparison shows good agreement between these two techniques.
A theoretical analysis of a planar, elliptically shaped 3‐dB quadrature coupler
Authors: Bialkowski M. E. , Jellett S. T.
Published: July 2007

A planar 3‐dB quadrature coupler in the form of an eight‐port elliptical disc is investigated. The hybrid consists of additional arbitrarily loaded reactive stubs and impedance steps for tuning purposes. A contour‐integral method of analysis is used to obtain the electric parameters of the structure.
Standing waves in scan impedance of finite scanned arrays
Authors: Hansen R. C. , Gammon Daniel
Published: July 2007

Scan impedance of elements, especially near the edge of a finite array, differs from that of an element in an infinite array. A numerical experiment shows the standing‐wave behavior of scan impedance over the finite array, for a range of scan angles. The standing wave exists even for a broadside beam. © 1995 John Wiley & Sons. Inc.
Studies of stacked electromagnetically coupled patch antennas
Authors: Lee Kai‐Fong , Chen Wei , Lee R. Q.
Published: July 2007

Theoretical results illustrating the behavior of stacked electromagnetically coupled patch antennas are presented, using a recently developed rigorous model for probe‐fed microstrip antennas. Examples of design guides are given and the need for comprehensive design guides is noted. © 1995 John Wiley & Sons. Inc.
Modeling of waveguide structures using the nonorthogonal FDTD method with a PML absorbing boundary
Authors: Wu Chen , Navarro Enrique A. , Chung Paul Y. , Litva John
Published: July 2007

In this letter, we combine the nonorthogonal FDTD method with a perfectly matched layer (PML) absorbing boundary condition to analyze waveguide structures. This combination provides a very useful numerical tool for modeling complex waveguide structures. The PML absorbing boundary condition is tested by simulation of propagation in a WR‐75 rectangular waveguide. It easily gives lower than −60‐dB return loss in the frequency band of interest. An E‐plane, U‐bend waveguide transmission line is modeled to demonstrate the usefulness of this technique. © 1995 John Wiley & Sons. Inc.
Coherent optical processor for inverse filter generation
Authors: Abushagur Mustafa A. G. , Riasati Vahid R.
Published: July 2007

A new algorithm and system architecture for inverse filter generation using a coherent iterative optical processor is presented. This processor avoids the singularity problem usually faced in inverse filter generation. The algorithm convergence is analyzed and a convergence condition is derived. Computer simulation of the algorithm performance is presented, and the results confirm the theoretical predictions for the convergence. Two optical architectures for the implementation of this algorithm are also introduced, based on space‐ and time‐domain utilization. © 1995 John Wiley & Sons. Inc.
Fast far‐field approximation for calculating the RCS of large objects
Authors: Lu Cai‐Cheng , Chew Weng Cho
Published: July 2007

A fast far‐field approximation (FAFFA) is developed to estimate the RCS of conducting scatterers. This method accounts for the interaction between subscatterers in two ways, depending on the electrical distance between the subscatterers. The interactions of subscatterers separated by a large electrical distance are computed in three stages: (1) aggregation, which computes the total field at a group center due to the subscatterers of the group; (2) translation, which translates the field from one group center to another; and (3) disaggregation, which distributes the field in a group center to each subscatterer in the group. Two strategies are employed to accelerate the computation in the above three stages. One is the use of far‐field approximation to simplify the computation in the translation stage; the other is the use of interpolation and smoothing techniques, which reduces the complexity of aggregation and disaggregation. The overall computational complexity for a matrix‐vector multiplication is of the order of N1.33, and the memory requirement is of order N. Numerical results show that this method can predict a RCS that is very close to exact solution, and that the method can be applied to objects with very large electrical sizes. © 1995 John Wiley & Sons. Inc.
Full‐wave analysis of microstrip Yagi array antennas
Authors: Ke Shyh‐Yeong , Wong Kin‐Lu
Published: July 2007

This article presents a rigorous analysis of microstrip Yagi array antennas using a full‐wave method and a moment‐method calculation. The input impedance of a microstrip Yagi array antenna is formulated and calculated. The obtained input impedance is found to be significantly altered as compared to that of a single driven microstrip patch, due to strong coupling between the driven and parasitic patches. Radiation patterns of the microstrip Yagi array antenna are also calculated and discussed. Both the E‐ and H‐plane coupling cases are considered. © 1995 John Wiley & Sons. Inc.
Microwave model of an optically controlled GaAS mesfet
Authors: Chakrabarti P. , Mishra B. K. , Kumar K. Satish , Shrestha S. K.
Published: July 2007

The effects of optical illumination on the microwave characteristics of a conventional MESFET have been studied theoretically. The effect of the changes in the intrinsic parameters of the device under illumination has been utilized to calculate the Y parameters of the device at microwave frequencies. The small‐signal equivalent circuit of the device in the illuminated condition has been obtained with the various components determined from the Y parameters. The attractive feature of the present model is that it is fully compatible with commonly used circuit simulation packages like SPICE. © 1995 John Wiley & Sons. Inc.
New technology to realize printed radiating elements
Authors: Tarot A. C. , Sharaiha A. , Terret C. , Ganier Y.
Published: July 2007

A plating process for low‐cost dielectric substrates (like polypropylene or foam) has been developed by the CNET (Centre National d'Etudes des Télécommunications) in collaboration with LAM (Laboratoire Antennes et Microélectronique). This process allows the realization of printed radiating elements like microstrip antennas. An example of a multilayered printed antenna realized with this technology is presented with its performance. © 1995 John Wiley & Sons, Inc.
Efficient space‐domain analysis of microstrip lines using wavelet transform
Authors: Kunasani Subba R. , Nguyen Cam
Published: July 2007

An efficient method of analyzing microstrip transmission lines is presented. The technique is based on solving coupled integral equations in the space domain using wavelet‐like basis functions. The unique feature of this approach is very fast computation, obtained due to the sparsity of the resultant matrix realized under a two‐dimensional wavelet transform. In the shielded single‐layer microstrip line considered, the computational time is reduced by approximately 40% when compared to the spectral‐domain approach. The computational advantage is expected to be much more pronounced when the dimensions of the matrix are large, a situation that is encountered in complex structures involving multiple layers and strips. The characteristic impedance and effective dielectric constant calculated using this approach are found to be very accurate, as they agree well with those obtained via the spectral‐domain method. © 1995 John Wiley & Sons, Inc.
An energy‐efficient free‐space optical interconnection for clock distribution
Authors: Tamil Lakshman S. , Hsia Kangmin
Published: July 2007

An energy‐efficient free‐space clock‐distribution scheme for intrachip and chip‐to‐chip application is proposed here. The scheme involves two aspheric mirrors in confocal configuration. The length between the mirrors should be equal to the length traversed by an optical ray in one or an integer multiple of the clock period for ghost‐free clock reception. The proposed method reuses the unused optical energy of a clock pulse scattered over the nonphotodetector area of the chip by synchronously combining with the optical energy of the successive clock pulses. Zero clock skew can be achieved by this method. © 1995 John Wiley & Sons, Inc.
Simplified closed‐form expressions for computing the generalized fresnel integral and their application to vertex diffraction
Authors: Capolino F. , Maci S.
Published: July 2007

The generalized Fresnel integral serves as a canonical function for the uniform ray field representation of several high‐frequency diffraction mechanisms. In this article, an example of application of this canonical function is examined, which is concerned with the diffraction at a plane angular sector with soft boundary conditions on its faces. Closed‐form expressions for computing this canonical function are presented, and it is shown that the approximate formulation adopted herein is accurate and very fast to calculate. © 1995 John Wiley & Sons, Inc.
Polarization behavior of spun fiber versus conventional fiber under strong slight twisting
Authors: Hung‐chia Huang , Ying‐chun He
Published: July 2007

In this article, the authors attempt to treat both strong twisting and slight twisting of fiber via a consistent asymptotic approach to the coupled‐mode theory. In strong twisting, an admirably simple and useful asymptotic equation is derived in the form R2τ = const., which relates the minimum required twist rate τ with the minimum allowable radius of curvature R. In slight twisting, an oscillatory pattern of the polarization behavior clearly reveals the advantageous feature of a twist‐spun fiber, which is made by a prior spinning of the fiber before a twisting. © 1995 John Wiley & Sons, Inc.
Complex permittivity and permeability measurements for high‐loss material in a waveguide
Authors: Jiang Cao , Yang Chongfong
Published: July 2007

A partially filled waveguide is presented to measure complex permittivity and permeability simultaneously at microwave frequency in this article. The mode‐matching method is used to analyze the higher‐order modes in the waveguide. Experimental results agree well with theoretical results. © 1995 John Wiley & Sons, Inc.
Traveling‐wave semiconductor laser amplifier induced intermodulation distortion for different digital modulation schemes in a subcarrier multiplexing system
Authors: Lee Yang‐Han , Tsai Chao‐Nan , Lee San‐Liang , Wu Jingshown
Published: July 2007

We analyze the intermodulation distcrtion (IMD) induced by four‐wave mixing in traveling‐wave semiconductor laser amplifiers (TWSLA) for different digital modulation schemes in a subcarrier multiplexing (SCM) system, and compare these results with the transmission of pure tones. We find that the IMDs are reduced in the digital modulation system, because the modulated signals disturb the homogeneous property of amplitude (ASK, FSK) or phase (PSK). We conclude that PSK has better performance, and the worst case is the transmission of pure tones. © 1995 John Wiley & Sons, Inc.
TE/TM decomposition of electromagnetic sources in uniaxial anisotropic media
Authors: Lindell Ismo V.
Published: July 2007

Decomposition of electromagnetic sources in two parts giving transverse electric (TE) and transverse magnetic (TM) fields with respect to a given direction, previously introduced to isotropic media, is extended to problems involving media with uniaxial anisotropic permittivity and permeability. The decomposition is made with respect to the axial direction of the medium. The fields radiated by the two decomposed sources see the medium as two affine‐isotropic media, which can be transformed to two isotropic media through two affine transformations. The decomposition method can be applied to simplify problems involving boundaries and structures that do not couple the decomposed fields. © 1995 John Wiley & Sons, Inc.
Cavity‐model analysis of a slot‐coupled cylindrical‐rectangular microstrip antenna
Authors: Wong Kin‐Lu , Chen Jin‐Sen
Published: July 2007

An equivalent circuit of a slot‐coupled cylindrical‐rectangular microstrip antenna is constructed by describing the patch admittance seen at the slot position using the cavity‐model method and calculating the slot self‐admittance simply from a short‐circuited slot line. An impedance transformer is also introduced in the circuit to transform the patch admittance and the slot self‐admittance into a series load as seen by the feed line. The input impedance of the antenna is then readily obtained. Typical numerical results of the input impedance are presented and discussed. © 1995 John Wiley & Sons, Inc.
A reed‐solomon coded optically preamplified PPM system
Authors: Cryan R. A.
Published: July 2007

A Reed‐Solomon coded optically preamplified pulse‐position modulation system is analyzed. Results are presented at a bit rate of 622 Mbit/s and a wavelength of 1.537 μm, comparing the system with an equivalent on‐off nonreturn‐to‐zero (OOK NRZ) system. The theoretical results demonstrate that the system offers a potential sensitivity of 7 photons/bit, which represents an improvement of 7.5 dB over the equivalent OOK system and is comparable with that of the best coherent systems reported to date. © 1995 John Wiley & Sons, Inc.
Microstrip antennas with multidielectric layers
Authors: Lee K. F. , Chen W. , Lee R. Q. , Luk K. M. , Tong K. F.
Published: July 2007

Results based on spectral‐domain full‐wave analysis are presented for several microstrip antennas with multidielectric layers. The geometries include (a) rectangular patch with two superstrates, (b) rectangular patch with a superstrate and an unwanted air space, and (c) rectangular patch with a superstrate and two substrates. Comparison with measurement is given. © 1995 John Wiley & Sons, Inc.