bluuebunny/crossref_metadata_2025 huggingface dataset:
Reflection and transmission in second harmonic generation of light in KDP crystal
Authors: Bhanthumnavin V. , Lee Chi H.
Published: July 2007

The intensity of second harmonic light beams generated in potassium dihydrogen phosphate (KDP) crystals immersed in the optically denser fluid I‐bromonaphthalene has been observed as a function of the incident angle of the fundamental beam of the neodymium‐glass laser. The laser pulses are polarized in the [110] direction with respect to the KDP crystallographic axes. We observed for the first time that there is no transmitted second harmonic light at normal incidence when the nonlinear polarization PNLS(2w) lies in the direction [001] along the crystal face normal. Furthermore, the noncollinear phase‐matching condition where the two incident fundamental beams are on the opposite side of the face normal is demonstrated. The results agree well with the theory of Bloembergen and Pershan.
A statistical approach for calculating the concatenated connector loss in fiber‐optic links
Authors: Uhing Jim , Thomas Steve , Christodoulou C. G.
Published: July 2007

The insertion loss contribution of concatenated connectors in fiber‐optic links is analyzed. A statistical approach based on the loss distribution of single connectors with a method for numerical convolution is developed. The predicted insertion loss is less than the sum of the “worst case” connector loss values. An avionics short‐haul fiber‐optic example illustrates the new approach.
Cutoff frequencies of dielectric waveguides using the multifilament current model
Authors: Altman Z. , Cory H. , Leviatan Y.
Published: July 2007

A new approach for finding the cutoff frequencies of a dielectric waveguide based on the multifdament current model is presented. In this approach, the boundary conditions on the fields are taken in the cutoff limit. The method is applied to an elliptic dielectric waveguide.
On the various forms of the coupled‐mode theory for optical waveguides
Authors: Chang Hung‐Chun , Huang Horng Shou , Wang Yeong‐Cheng
Published: July 2007

We review the various forms of the coupled‐mode theory for optical waveguides. One subtle distinction between two different formulations of the conventional coupled‐mode theory is pointed out. Comparison of accuracy between them and the recently formulated new theory is conducted for the two‐ and three‐slab waveguide structures.
Anomalous acousto optic effects in acrylic plastics
Authors: Taalbi Mustapha , Ishii T. Koryu
Published: July 2007

An anomalous acoustic effect is observed when a laser beam is guided into an acrylic plastic plate and is modulated by acoustic waves. The laser beam spreads into various beams with the modulation frequency, the double frequency and the triple frequency, simultaneously.
The use of conical tips to improve the impedance matching of cassegrain subreflectors
Authors: Corkish Richard
Published: July 2007

Retrofitting cones to the vertex of a subreflector in a Cassegrain antenna is shown to give worthwhile improvements in impedance match with little or no decrease in efficiency. This is of particular interest for improving the axial ratio of existing dual circularly polarized antennas.
Total field evaluation near the edge shadow of an idealized inflected surface
Authors: Rahnavard M. H. , Rusch W. V. T.
Published: July 2007

The conventional Kouyoumjian transition function cannot be used to evaluate the diffracted field for a converging wave because its argument is imaginary, and the total field is not continuous at reflection and shadow boundaries. In order to find the diffracted field near the edge shadow of the inflected surface, Rusch's proposed edge‐diffraction transition function for a converging wave is used. The argument of this transition function is real and produces a continuous total field at the boundaries. The diffracted field is then added to the geometrical optics field and compared favorably with physical optics.
The bandwidth characteristics of ridged circular waveguides
Authors: Rong Yu
Published: July 2007

A numerical approach for investigating the bandwidth of ridged circular waveguides is described in this article. This approach is the combination of the boundary element method (BEM) and modifying the boundary, which is first proposed here. By this approach, high convergence of numerical solution and good agreement between experimental results and theoretical results can both be achieved.
Optical effects in hemts
Authors: de Sailes A. A.
Published: July 2007

The major photoeffects affecting the DC and RF performance of depletion mode Al0.3Ga0.7As/GaAs HEMTs are presented. When photons are absorbed only in the GaAs layer, an increase in the electron concentration of the 2‐DEG channel is estimated (photoconductive effect). When photons are also absorbed in the AlGaAs layer the gate junction photovoltage is calculated (photovoltaic effect).
Microwave circuit modeling for semiconductor lasers under large and small signal conditions
Authors: Elkadi H. , Vilcot J. P. , Maricot S. , Decoster D.
Published: July 2007

We present a new large/small signal equivalent circuit for semiconductor lasers, valid for above‐ as well as below‐threshold operating conditions, based on the monomode rate equations and a polynomial approximation of Fermi integral. The model is thus valid for conditions of large injection. Results obtained by this model match perfectly those obtained by numerical integration of the rate equations. The equivalent circuit is easy to implement and solve on a nonlinear circuit analysis software such as SPICE and consequently allows the study of the parasitic effects as well as the laser behavior in complex circuits. Comparison between this model and previously published models is presented. The model is applied to the study of various heterojunction laser diodes, the experimental results of which have been published elsewhere.
Graphical tools for designing low‐noise microwave amplifiers with requirements on the input VSWR
Authors: Macchiarella G. , Politi M.
Published: July 2007

Two novel kinds of circles on the Smith chart are introduced, which allow, in designing low‐noise microwave amplifiers, taking into account the level of the input match. Outlines of design procedures for using these circles are also given.
Solution of thin‐wire integral equations by nystrom methods
Authors: Kot John S.
Published: July 2007

Numerical solutions to the electric‐field integral equation (EFIE) for a thin wire are obtained by a Nystrom method. The singular EFIE is treated by subtraction of the singularity and a thin‐wire integral equation convenient for numerical solution is obtained. Solutions for exact and approximate EFIE kernels are compared.
On quasi‐static source models for wire dipole antennas
Authors: Rensburg Danieul J. Janse , McNamara Derek A.
Published: July 2007

The moment method computation of the input impedance of dipole antennas, obtained using numerically generated source models which are more closely related to the actual physical shape of the antenna feed region, are discussed.
Dispersion characteristics of optical dielectric waveguides
Authors: Cheng Yuehua , Lin Weigan
Published: July 2007

A new iteratively equivalent index method for the analysis of rectangular dielectric waveguide problems is presented. This analysis is found to be more accurate both than the effective index method and the modified effective index method. The results obtained by this method compare very favorably with those produced by the variational analysis, weighted index analysis, and numerical computation over a large range, but without the complexity of the latter.
Cutoff attenuator for azimuthally symmetric transverse magnetic mode in a cylindrical waveguide
Authors: Elaoud Moncef , Seshadri S. R.
Published: July 2007

A treatment of the cutoff attenuator for azimuthally symmetric lowest order transverse magnetic mode in a cylindrical waveguide is given. Some numerical results of the insertion loss as well as its frequency response are included.
A balanced optical interferometric sensor with a wavelength‐dependent offset
Authors: Bernard J. E. , Chrostowski J. , Wartak M. S.
Published: July 2007

A Mach‐Zehnder interferometer with dissimilar arms in the form of buried‐rib and ARROW waveguides is considered. The interferometer has a wavelength‐dependent offset because of diferent chromatic dispersion in the two arms. This feature makes it possible to build a balanced interferometric sensor with negligible temperature sensitivity but in which the offset due to an external stimulus can still be determined by varying the wavelength of the source. Dispersion calculations for this interferometer are presented with a possible construction design.
A simple and efficient formulation for the transmission characteristics of generalized suspended striplines
Authors: Rong Ao Shong
Published: July 2007

An efficient numerical procedure based on full‐wave analysis is formulated to compute the transmission characteristics of suspended striplines including the finite metallization thickness and substrate‐holding grooves. The formulation identifies the electric current sheets on the metallic strips and the magnetic current sheets at the apertures of the grooves, instead of the magnetic current sheets at the interfaces between adjacent media, as the unknown source quantities to be determined. The effect of the finite metallization thickness is taken into approximate account by the electric current sheets on the upper and lower surfaces of the metallic strips. This makes the final matrix equation be of the moderate order and calculated with the reasonable CPU time. The validity of the formulation is confirmed by comparing the present results with available data in the literature.
Propagation constant of microstrip leaky‐wave antennas
Authors: Abdallah E. A. F. , Mitkees A. A. , Hamdy S. A. , Elsohly A. A.
Published: July 2007

A microstrip leaky‐wave antenna is treated as a microwave network. A transverse resonance method with perturbation technique is applied to the resonance equation to get results in a simple and practical form. The aperture admittance is taken from that of a dielectric loaded parallel plate transmission line radiating into space. Good agreement is obtained between the theoretical and the experimental results.
Submillimeter heterodyne remote sensing of upper atmospheric gases
Authors: Waters Joe W.
Published: July 2007

Technology is now becoming available to develop submillimeter‐wavelength heterodyne radiometric experiments for remote sensing the upper atmosphere from space. Such experiments can provide many essential measurements for assessing and critically monitoring the depletion of stratospheric ozone by pollution from industrial products. A millimeter‐wavelength experiment for this purpose is now ready for launch on the NASA Upper Atmosphere Research Satellite (UARS). An enhanced version of the UARS experiment, which operates at submillimeter wavelengths, is under investigation for the future NASA Earth Observing System.
Aperture efficiency of integrated‐circuit horn antennas
Authors: Guo Yong , Lee Karen , Stimson Philip , Potter Kent , Rutledge David
Published: July 2007

We have improved the aperture efficiency of silicon integrated‐circuit horn antennas by optimizing the length of the dipole probes and by coating the entire horn walls with gold. To make these measurements, we developed a new thin‐film power‐density meter for measuring power density with accuracies better than 5%. The measured aperture efficiency improved from 44% to 72% at 93 GHz. This is sufficient for use in many applications which now use machined waveguide horns.
A planar dipole array antenna with an elliptical lens
Authors: Skalare A. , De Graauw Th. , van de Stadt H.
Published: July 2007

We describe a planar antenna structure consisting of two half‐wave dipoles, which are backed by a metallic reflector to create an image of two more elements. The array produces rather a wide main beam, and is therefore used with a dielectric lens. The far‐field pattern of the dipole liens antenna has cross‐pol better than −20 dB, and side lobes below −13 dB over an octave band. The impedance at the feedpoint of the antenna is approximately 70 ‐ j10 Ω at the center of the band.
Twin slot antenna structures integrated with microbolometer detectors for 94‐GHz imaging
Authors: Heston John G. , Lewis Jason M. , Wentworth Stuart M. , Neikirk Dean P.
Published: July 2007

The twin slot antenna on a dielectric stack should find application in the far‐infrared spectral region. We present measurements at 94 GHz which show that this antenna will be useful as an imaging element.

Based on these results, in combination with a new detector element, a two‐dimensional FIR imaging array is proposed.
Tunnel transit‐time (tunnett) devices for terahertz sources
Authors: Haddad G. I. , East J. R. , Kidner C.
Published: July 2007

The potential and capabilities of tunnel transit‐time (TUNNETT) devices for power generation in the 100‐1000 GHz range are presented. The basic properties of these devices and the important material parameters which determine their properties are discussed and criteria for designing such devices are presented. It is shown from a first‐order model that significant amounts of power can be obtained from these devices in the terahertz frequency range.
Planar doped barrier devices for subharmonic mixers
Authors: Lee T. H. , East J. R. , Haddad G. I.
Published: July 2007

Mixers are a critical component of most millimeter‐wave and terahertz systems. Often, the front‐end mixer performance determines the overall system performance. At higher millimeter‐wave and terahertz frequencies, mixer performance can be limited by the lack of low‐cost solid‐state sources. A subharmonic mixer with a pumping frequency at half the signal frequency would reduce the source power requirements at these higher frequencies. Typical subharmonic mixers use back‐to‐back Schottky barrier diodes. The resulting structures are difficult to fabricate. The performance can be degraded by unmatched diodes or by parasitics associated with the various connections. One possible solution is to use an integrated Schottky barrier structure. Another possible solution is to use a planar doped barrier (PDB) as a single‐device subharmonic mixer. This article presents an analysis of PDB subharmonic mixer performance.
Noise performance degradation in feedback oscillators with nonzero phase error
Authors: Cheng K. K. M. , Everard J. K. A.
Published: July 2007

The degradation in oscillator noise performance with nonzero phase error is described. Noise measurements on both bipolar and GaAs oscillators are presented. It is shown that phase error is an important parameter in the design of state‐of‐the‐art low‐noise oscillators.
Dual‐polarized microstrip array with high isolation and low cross‐polarization
Authors: Huang John
Published: July 2007

A 2 × 2 dual‐polarized microstrip array antenna with high isolation between the two input ports and low cross‐polarization level has been developed. The technical background for this achievement and antenna performance results are presented.
Improved correlation discrimination using joint fourier‐transform optical correlator
Authors: Alam Mohammad S. , Awwal Abdul Ahad S. , Karim Mohammad A.
Published: July 2007

Attempts are being made to investigate techniques to improve the cross‐correlation peak heights of a joint‐transform‐based correlator while reducing the corresponding dc peaks. Two such techniques, namely, preprocessing the reference image and postprocessing the joint Fourier‐transform image, are investigated, and the corresponding simulation results are compared.
Transmission‐line model to analyze a multistage polarizer rotator
Authors: Gimeno B. , Such V. , Garcia A. C. , Cruz J. L. , Navarro E.
Published: July 2007

A simple transmission‐line model to design a broadband system consisting of a multilayered polarization rotator that rotates the polarization plane of a linearly polarized electromagnetic wave is presented. A simulation program that permits the design of the rotator parameters was implemented, and a prototype was designed, manufactured, and tested. Comparisons between the theoretical results and measurements are given, and a good correspondence is found.
A method for designing microwave broadband amplifiers by using chebyshev filter theory to design the matching networks
Authors: Quirarte José Luis Ramos
Published: July 2007

A method for designing microwave broadband amplifiers is presented. In order to obtain broadband operation, the matching networks are designed using filters with Chebyshev characteristics. To make good use of the transistor, the reactive parts of its input and output impedances are used as part of the first resonator in the filters. The method is applied to the design of a low‐noise amplifier in a microstrip substrate operating at frequencies from 4‐6 GHz. The results show that the method is efficient in designing amplifiers having about 40% bandwidth.
Analysis of Unsymmetrical Waveguide Y‐junction circulators
Authors: Dou W. B. , Rong Y.
Published: July 2007

This article analyzes unsymmetrical waveguide Y‐junction circulators whose two arms are connected with H‐plane bends according to the electromagnetic field solutions given in [1, 2]. The scattering matrix and numerical results are given. The results show that the H‐plane waveguide bend has an influence on the performance of the waveguide Y‐junction circulators.
Aspsk with postdetection filtering: An accurate analysis
Authors: Betti S. , De Marchis G. , Iannone E. , Lazzaro P.
Published: July 2007

In this article antipodal Stokes parameters shift keying (ASPSK) performance is analyzed when a postdetection filter is used before decision. This baseband processing allows high insensitiveness to phase noise to be achieved, so that the system can work with a limited penalty even when the laser linewidth is comparable with the bit rate.
Further study on the rectangular coaxial line of simple symmetry
Authors: Lin Weigan
Published: July 2007

The structure of the rectangular coaxial line is of simple symmetry: however, its exact analysis is difficult. Riblet solves this problem by making use of the degenerate Ryperelliptic integral [3]. Here we point out that his results break down when the inner conductor becomes a strip. We solve this latter case and offer the solution of the rectangular line with a general cross‐inner conductor.
Numerical analysis of an optical coupler composed of three‐channel waveguides with different core sizes
Authors: Kubo Hiroshi , Yasumoto Kiyotoshi
Published: July 2007

An optical coupler composed of three‐channel waveguides with different core sizes is analyzed numerically. Dispersion relations and field distributions are presented for the lowest three modes in the coupler. It is shown that the geometric parameter of the coupler can be optimized so as to satisfy the condition for a maximum power transfer efficiency.
Parametric studies of the linearly tapered slot antenna (LTSA)
Authors: Kooi P. S. , Yeo T. S. , Leong M. S.
Published: July 2007

The characteristics of linearly tapered slot antennas of flare angles 5°–30° were studied parametrically, and the frequency range within which they can be predicted using a discretized approach was investigated.
An accurate distributed model for MIM capacitors
Authors: Sadhir Virender K. , Bahl Inder J.
Published: July 2007

This article reports an accurate model for metal‐insulator‐metal (MIM) capacitors designed for monolithic microwave applications. The distributed nature of the model presented is valid for different substrate thicknesses. This model has been validated by comparing the simulated results with the measured data for several MIM capacitors on a 125‐μm‐thick GaAs substrate.
New receiver scheme for homodyne and intradyne satellite optical links
Authors: Betti S. , De Marchis G. , Iannone E. , Pietroselli M.
Published: July 2007

A new receiver scheme is presented for homodyne and intradyne satellite optical links. It is based on the property that the circular polarization of the transmitted optical signal, required in space communication for platform rotation insensitiveness, detected by a polarization diversity receiver provides in‐phase and in‐quadrature electrical signals.
Some experimental investigations on electromagnetically coupled microstrip antennas on two‐layer substrates
Authors: Roy J. S. , Shaw S. K. , Paul P. , Poddar D. R. , Chowdhury S. K.
Published: July 2007

The results of some experimental investigations on electromagnetically coupled microstrip antennas on two‐layer substrates are reported in this article. The variation of input impedance of electromagnetically coupled square and circular microstrip patches, with the degree of overlapping between the patch and feedline, is studied. Also presented is the percentage shift of resonance frequency due to the change of this overlapping. A method of increasing the 1:2 V.S.W.R. bandwidth of the patch antenna is also indicated.
The field distribution inside a tem cell with a cross of unequal arms as inner conductor
Authors: Lin Weigan
Published: July 2007

The field distribution of a new type of TEM cell with a cross of unequal‐length arms as the inner conductor is given here. The whole field of such a cell consists of a high‐field region and a uniform field region, useful in many applications.
Finite element analysis of semiconductor laser arrays
Authors: Zhao An Ping , Cvetkovic Srba R.
Published: July 2007

This article presents the analysis of semiconductor laser arrays based on the finite element method, with emphasis on nonuniform structures where the channel width and/or refractive index can vary across the array. The results show that the variation of channel width will have the same effect on the near‐field intensity profile as the variation of channel refractive index. Based on this finding, a laser array structure devised to achieve a highly desirable uniform intensity distribution for the lowest‐order mode is also presented.
Mutual coupling between skewed microstrip patch antennas
Authors: Wahid P. F. , Dunn G. L. , Dunn D. S.
Published: July 2007

This article considers mutual coupling as a function of the skew angle between rectangular microstrip patch antennas configured in a two‐element array. Reflection and transmission data for antenna arrays are presented with emphasis on the measured mutual coupling between the elements for varying skew angles.
Two models of optical waveguide modulators independent of polarization
Authors: Zhu Ning Hua , Lin Yi Kun
Published: July 2007

Two novel models of optical waveguide modulators with polarization‐independent operation are created in this article. The efficiencies and the fabricational tolerances of these devices using Z‐cut or Y‐cut LiNbO3 substrate are discussed in detail and the comparison between two models is made.
Accurate computation of mode characteristics for open‐layered circular cylindrical microstrip and slot lines
Authors: Nosich Alexander I. , Svezhentsev Alexander Ye.
Published: July 2007

The results of a highly effective numerical analysis of fundamental and higher‐order modes on open circular cylindrical microstrip and slot lines filled with layered dielectric are presented. The results could be used to optimize the bandwidth and mode‐purity characteristics of the lines.
BI‐isotropic constitutive relations
Authors: Sihvola Ari H. , Lindell Ismo V.
Published: July 2007

The constitutive relations of general bi‐isotropic media, requiring four material parameters, can be written in different ways to describe their electromagnetic behavior. This communication contains a two‐way “dictionary” between a proposed formulation of the constitutive relations with three other sets of relations, generalized from relations used for chiral materials.
Polarimetric scattering characteristics of simple radar targets using Hertz's vector potentials
Authors: Bhattacharyya Asoke K.
Published: July 2007

Hertz's vector potential is used to compute the co‐and cross‐polarized scattered fields due to simple targets like an arbitrarily oriented wire, an arbitrarily oriented loop of wire, and an infinite cylinder. The monostatic cross‐polarization properties of these targets are studied with different radar and target parameters. Important conclusions are summarized. It is found that under certain combinations of parameters, the cross‐polarization radiation is significant even for simple targets.
Polarization‐encoded optical shadow casting: An efficient multiplier design
Authors: Ahmed Jamal U. , Awwal Abdul Ahad S.
Published: July 2007

An efficient multiplier has been designed using a polarization‐encoded optical shadow casting scheme. The design algorithm for identifying the source patterns, input patterns, and ouput mask is also presented.
Application of the Green's function technique in microstrip patch antenna analysis
Authors: Lehtola Antero , Nikoskinen Keijo I. , Lindell Ismo V.
Published: July 2007

Microstrip structures are now widely used in microwave systems because of their geometrical simplicity, small size, and ease of fabrication. The microstrip structure is inhomogeneous along several directions, which makes the accurate analysis of the electromagnetic fields very difficult. Hence, the design of microstrip devices is mostly done with approximative and empirical methods of limited accuracy. In this report the Green's function technique is used to analyze rectangular microstrip patches. Scalar Green's functions corresponding to the microstrip geometry were derived earlier by the authors. With the aid of these functions, surface currents and resonance frequencies of a patch located in the air/dielectric interface can be computed using the method of moments (MoM). To make the implementation of MoM as simple as possible, numerical approximations for scalar Green's functions are developed. These approximations are functions of permittivity, the frequency, and the thickness of the substrate. Examples of computed results for resonance frequencies of a microstrip patch are given in the present article.
Full‐wave analysis of superconducting microstrip for MMIC applications
Authors: Paleczny E. , Legier J. F. , Kennis P. , Pribetich P.
Published: July 2007

In this article we take into account the influence of the superconducting nature of the strip in order to study the behavior of the superconducting microstrip line by means of two numerical methods. The first one is the spectral domain approach modified by the surface impedance concept and the second one is the modified mode‐matching technique. This last one allows more accurate simulation of the presence of the superconducting strip without using surface impedance approximation. In a second step we present the corrections brought to the modified SDA in order to obtain accurate results by this more versatile numerical method, which consumes small amounts of CPU time.
Role of complex modes in coplanar‐waveguide‐to‐coplanar‐waveguide discontinuity calculations
Authors: Kooi P. S. , Leong M. S. , Widjojo Benny , Yeo T. S.
Published: July 2007

The existence of complex modes in the lossless symmetrical shielded coplanar waveguide is demonstrated. Complex modes are found to occur only within a range of frequency and structural parameters. It is shown that exclusion of these modes in the analysis of coplanar waveguide discontinuities can cause the imput reflection and transmission coefficients to converge to incorrect values, thus highlighting their importance in such problems.
Polarization agile microstrip array antenna element
Authors: Sangster A. J.
Published: July 2007

A new microstrip antenna element is described which exhibits polarization agility. This is achieved by employing a T‐slot radiator which is driven by the edge fields of a balanced microstrip line. The balanced line can support two propagating modes, namely, an even mode and an odd mode, and by switching between these modes, the orthogonal arms of the T‐slot radiator are separately excited thus forming orthogonally polarized radiated fields. A microstrip patch antenna, which displays polarization agility using the same mechanism, is also described.
Vector potential green's function for a radially directed line dipole in open space
Authors: Butler Chalmers M.
Published: July 2007

A vector potential Green's function for a radially directed line dipole (Figure 1) is derived. Methods for obtaining two‐dimensional Green's functions are available for the z‐directed line current and for the OS‐directed line dipole. With the results of this article available, the set of Green's functions for two‐dimensional sources in cylindrical coordinates is complete.
Design of ergodic electromagnetic cavities
Authors: Booske J. H. , Meng B.
Published: July 2007

Cavity Q's and reflection coefficients for cavities excited by single “ergodic” eigenmodes are quantitatively calculated based on the available expressions derived from the Hamiltonian formulation. The results are compared with those obtained for multimode excitation in large, “untuned” resonant cavities. Applications relevant to the microwave and millimeter‐wave regime are discussed. In addition to absorption spectroscopy and materials processing, ergodic cavities may used as radiation‐beam dumps for high‐power testing of millimeter‐wave sources.
A wide‐band class‐b amplifier using tapered interdigital power combiners
Authors: Tsai M. C.
Published: July 2007

A tapered interdigital equal‐split coupler has been designed and fabricated in a planar structure. Multioctave bandwidths of equal power splits and 0° and 180° phase differences were obtained. Over 20‐dB improvement of the second harmonics generated from a Class‐B GaAs amplifier using this coupler as a combiner was demonstrated. This approach has potential applications for GaAs MMIC amplifiers and mixers.
Microwave measurement of complex permittivity of dielectric ring resonators using higher‐order resonant modes
Authors: Kim Jeong Phill , Park Wee Sang
Published: July 2007

A theory and measurement technique to determine the complex permittivity of microwave dielectric ring resonators placed between two conducting plates is presented. The resonant frequencies and unloaded quality factors for higher‐order modes, and physical dimensions of the resonator are used to expand the measurement frequency span.
Vectorial analysis of triple rib guide heterostructures as wavelength duplexers
Authors: Stuwe Peter , Unger Hans‐Georg
Published: July 2007

An integrated optical duplexer with three rib waveguides is investigated theoretically by a two‐dimensional mode‐matching technique with modal fields obtained by the method of lines. The results are compared with those of a one‐dimensional analysis and show the range of applicability of the effective index method. An optimized duplexer for separation of the 1.3‐μm band from the 1.55‐μm band is only 290 μm long and has a 1‐dB bandwidth of 0.15 μm. A complete one‐dimensional mode expansion shows that radiation has no significant influence on the duplexer characteristics. They are also nearly independent of polarization.
Gaussian beams and the poincare sphere
Authors: Sauter Elmar G.
Published: July 2007

Via a stereographic projection we map the transformation law for complex q parameters onto the unit sphere. The bilinear transformations correspond to rotations on the sphere.
Combined perturbation and wiener‐hopf analysis of the diffraction by a finite sinusoidal grating
Authors: Kobayashi Kazuya
Published: July 2007

Plane‐wave diffraction by a finite sinusoidal grating is analyzed approximately using the Wiener‐Hopf technique combined with the perturbation method. Scattered far field is derived with the aid of the saddle‐point method and scattering characteristics of the grating are discussed via numerical computations of the far‐field patterns.
Quasi‐tem and full‐wave approaches for coplanar multistrip lines including gyromagnetic media longitudinally magnetized
Authors: Mesa F. , Horno M.
Published: July 2007

The quasi‐TEM and full‐wave algorithms developed in this article enable us to deal with a coplanar transmission line including an arbitrary number of conductors and lossy magnetic and/or dielectric layers. The quasi‐TEM and the full‐wave approaches are compared in order to establish reliable criteria concerning the validity range of the quasi‐TEM analysis. The exact knowledge of this range permits us to study new MIC or MMIC configurations combining gyromagnetic, ferrimagnetic‐semiconductor, and dielectric layers by means of the simple quasi‐TEM model.
The recurrence matrix technique for the arbitrary millimeter‐wave and microwave planar transmission lines
Authors: Qiu C. M. , Ren W. , Lin W.
Published: July 2007

The analysis of the APTL has been completed by using a new, general recurrence matrix technique based on the method of lines. This new technique has laid the foundations for the analysis of the new type of planar structures. Numerical results for three complicated structures show that the developed CAD software is accurate, practical, and general.
Investigations on arrays of nonidentical radiators
Authors: Raju G. S. N. , Rao P. M. , Gottumukkala K. R. , Chakraborty Ajoy
Published: July 2007

The narrow beams with very low sidelobes are generated from an array of nonidentical elements. The array considered in the present work is found to be more advantageous than the array of identical elements in terms of main beamwidth and side‐lobe levels, excitation levels being uniform in both cases.
Novel rotational characteristics of radiation patterns of chirostrip dipole antennas
Authors: Pelet Philippe , Engheta Nader
Published: July 2007

We present certain novel characteristics of the radiation pattern of a chirostrip dipole antenna which consists of a short horizontal dipole antenna on a grounded chiral substrate. Chiral materials are characterized by constitutive relations D = ϵeE + iϵcB and H = B/μc + iϵeE. In our theoretical analysis we show that the radiation pattern of a simple chirostrip horizontal dipole undergoes a rotation around the axis normal to the substrate and that this rotation depends on the value of the chirality iϵe. Applications of this novel antenna are mentioned.
On the harmonic balance analysis of almost‐periodic autonomous nonlinear circuits with dynamic nonlinear characteristics
Authors: Camacho‐Peñalosa C. , Martin‐Funke E.
Published: July 2007

Analytical expressions for the efficient computation of sensitivities with respect to fundamental periods in dynamic nonlinear characteristics under multitone excitation are presented. Almost‐periodic oscillations in the forced Van der Pol oscillator are computed to illustrate the capability and efficiency of the resulting harmonic balance technique.
Wavelength dependence of the optical control of a hemt oscillator
Authors: Romero M. A. , Bangert A. , Zhang X. , Herczfeld P. R.
Published: July 2007

The direct optical control, tuning, FM modulation, and injection locking of a 2–GHz HEMT oscillator using a semiconductor laser (α = 0.85 μm) is reported. An optical tuning range of 4.3 MHz and an optical injection locking range of more than 0.55 MHz at fundamental frequency were achieved. For the first time an experimental study relating the photoresponse mechanisms in the HEMT to the wavelength of the incident light is presented. It is shown that for the 0.85–μ‐wavelength illumination the photoconductive effect dominates the optical response of the device, while for 0.633–μm illumination the photovoltaic effect prevails [1]. The photoconductive mechanism, which is smaller but faster, is more suitable for high frequency applications such as direct optical injection locking.
Proposal of a high‐capacity all‐optical tdma network
Authors: Matera F. , Romagnoli M. , Settembre M. , Tamburrini M.
Published: July 2007

A scheme of an all‐optical synchronous TDMA network is proposed with the demultiplexing process obtained by means of an optical gate based on the second harmonic generation process and pulse propagation in the soliton regime. Such a network would present a maximum throughput of 125 Gbls.
Electromagnetic coupling between coplanar waveguide and microstrip antennas
Authors: Simons Ralnee N. , Lee Richard Q. , Lindamood Glenn R.
Published: July 2007

Electromagnetic coupling between coplanar waveguides (CPW) and microstrip patch antennas has been investigated for two feed configurations: (1) direct aperture‐coupled feeding of a patch antenna by a CPW feed, and (2) proximity‐coupled feeding of a patch antenna by a microstrip line which is aperture coupled to a CPW feed. Results indicate that both feeding approaches are feasible and yield high coupling efficiency.
Further study on the characteristics of a rectangular line with off‐centered strip inner conductor
Authors: Lin Weigan
Published: July 2007

In 1979 Riblet gave an excellent treatment of this rectangular line with an off‐center strip inner conductor [1]; however this work may not be very useful to those not very familiar with elliptical integrals. Here we will try to reformulate Riblet's results with some comments.
Dipole radiation in the presence of a grounded chiral slab
Authors: Cheng Dajun , Xue Liangjin
Published: July 2007

Radiation of an electric dipole located along an arbitrary direction in the presence of a grounded chiral slab is investigated using matrix analysis in conjunction with Fourier‐transform techniques. Numerical results of the radiation pattern of such a structure are plotted both for vertical and parallel cases.
Optoelectronic chip implementation of a bipolar quadratic associative memory
Authors: Lin Senmao , Chen Caisheng
Published: July 2007

The optoelectronic chip implementation of a bipolar quadratic associative memory is reported. A new version of the bipolar quadratic neural network is proposed and an optoelectronic system based on two inner‐product multipliers is used. The quadratic associative memory described in this article has a larger storage capacity and a higher error‐correction capability than those of the unipolar one. Experimental results are also given.
A new identity in jacobian function and its application
Authors: Lin Weigan
Published: July 2007

A new identity in Jacobian function is derived and an example of its application is given.
Theoretical and experimental study on the linear microstrip patch antenna array technique using e‐plane gap coupling
Authors: Cho Young Ki , Hwang Oon Ha , Lee Kwang Eok
Published: July 2007

The purpose of this article is to present a theoretical method for analyzing an E‐plane gap‐coupled rectangular microstrip array antenna which consists of one center‐fed patch and several parasitic elements by use of the transmission‐line model and the equivalent circuit parameters for the capacitive gap between microstrip patch and the open end of the patch. Antenna characteristics such as radiation pattern and return loss are computed theoretically and compared with experimental results for illustrating the usefulness of this method.
Perforated dielectric lens
Authors: Lee C. S. , Lee S. W. , Davis R. , Tsui J.
Published: July 2007

The dielectric lens for an ideal focusing effect requires a continuously varying dielectric constant. In this article, the varying dielectric constant is simulated by drilling holes in the lens. The gain improves significantly (˜3 dB) by placing holes in the lens when the lens diameter is much larger than the wavelength (>10 λ) but the hole size is small (<0.25 λ).
Non‐gaussian beams in direct coupling from laser diodes into optical waveguides via small gaps
Authors: Lee Keh‐Yi , Wang Way‐Seen
Published: July 2007

In a direct coupling from a laser diode into an optical waveguide, some mathematical models about field profile, spot size, and phase variation of the optical beam within the small diode‐waveguide gap can be used to fit the experimental data much better than those of the Gaussian beam. These models are expected to be useful in the numerical simulation of the losses of the diode‐to‐waveguide or diode‐to‐fiber coupling.
A novel mesfet‐compatible gaas optoelectronic switch
Authors: Riesz Ferenc , Szentpáli B. , Gottwald P. , Németh‐Sallay M.
Published: July 2007

Photoconductive optoelectronic pulse‐forming switches have been fabricated from vapor‐phase epitaxially grown GaAs‐based layer structures. The fabrication process is compatible with the MESFET/MMIC technology. The light‐absorbing region is thinned by chemical etching, thus changing the actual carrier lifetime in this region. The switches showed off/on resistance ratios of about 500 even at about 0.1‐mW incident optical power. The pulse response of the devices is limited by the lifetime of charge carriers.
Electromagnetically coupled patch antenna—theoretical and experimental investigations
Authors: Karmakar Nemal C. , Bhattacharyya A.
Published: July 2007

Equivalent circuit of an electromagnetically coupled (EMC) rectangular patch antenna is obtained using reciprocity. Theoretical results for the return loss are in good agreement with the experimental data. The model is simple both conceptually and computationally, and can be used to predict the performance of EMC antennas.
Input impedance of rectangular microstrip antennas with a dielectric cover
Authors: Fan Zhibo , Lee Kai‐Fong
Published: July 2007

A theoretical and numerical analysis of the rectangular microstrip antenna with a dielectric cover is presented. Numerical results on input impedance are given, showing that the main effect of the dielectric cover is to reduce the resonant frequency, with only minor changes in the resonant resistance and the impedance bandwidth.
Image reconstruction for computer tomography using the bimodal optical computer
Authors: Habli M. A. , Leonik K.
Published: July 2007

Image reconstruction for computer tomography using an optical computer is proposed and tested. The computer simulation results are reported.
Comparative study of the galerkin and the least‐squares boundary residuals (lsbr) methods for the analysis of microwave integrated circuits (MICs)
Authors: Essaaidi M. , Boussouis M.
Published: July 2007

In this article a comparative study of the least‐squares boundary residuals (LSBR) and the Galerkin methods is presented. The study shows that both methods are relatively and rapidly convergent. A criterion of relative convergence is developed for the LSBR method. In addition, this method is shown not to yield spurious solutions, which are normally encountered with the Galerkin method. A systematic modes identification technique is also provided for the Galerkin method.
A recursive algorithm to compute the wave‐scattering solution of a finite‐strip array using an efficient plane‐wave basis
Authors: Chew W. C. , Lu C.
Published: July 2007

A truncated, nonuniform, finite array of strips does not have a closed‐form solution. Using translational symmetry, a recursive algorithm that calculates the scattering solution with N log2 N computational complexity is described. The current distribution for the Hz polarization shows small‐length‐scale oscillations not present in the Ez polarization.
Refractive index control on the polarization sensitivities of semiconductor traveling‐wave laser amplifiers
Authors: Ghafouri Shiraz H. , Chu C. Y. J.
Published: July 2007

We have found that the polarization sensitivity of buried heterostructure traveling‐wave laser amplifiers can be minimized further by controlling the refractive index profile in its transverse plane, in addition to increasing the active layer thickness.
Influence of the drawing ratio and the relative index difference on propagation characteristics in single‐mode fibers with arbitrary refractive index profile
Authors: Gao Yangsheng
Published: July 2007

Simple formulas are derived for the sensitivity of dispersion, mode field radii, and cutoff wavelengths in single‐mode fibers due to arbitrary variations of the drawing ratio and the relative index difference simultaneously. For calculations only the propagation characteristic spectrum of the ideal fiber is required. Some applications are given.
Microwave complex permittivity of rainwater in the 26–40‐ghz band
Authors: Kooi P. S. , Tran V. N. , Leong M. S. , Yeo T. S.
Published: July 2007

The complex permittivity of rainwater, which is required for the modeling of rain‐induced attenuation of electromagnetic waves, has been measured at Q band (26–40 GHz) using the infinite line impedance technique. The results obtained were found to differ slightly from those of distilled water.
The accurate variational analysis for the measurement of the complex dielectric constant of a sample rod inserted in a cavity
Authors: Liang C. H. , Xie Y. J.
Published: July 2007

This article derives a Lindell formulation based on a generalized variational principle. A complex dielectric constant measurement of a small‐loss dielectric rod using the Rayleigh—Ritz method gives accurate variational analysis. The concept of complex frequency ω is introduced in general, and the stability of the solution is discussed. When compared with the results of perturbation, it is concluded that the deviation of the algorithm is worthy of more attention.
Compact optically triggered microwave pulse generator
Authors: Riaziat M. L. , Nishimoto C. K.
Published: July 2007

The design process and experimental results are presented for a compact microwave injection wave pulse generator using high‐speed optical switches. This device generates a few cycles of 12‐GHz radiation, and has dimensions of 2.1 × 2.2 millimeters.
Photoconductors as dynamic memory elements
Authors: McGinn V. P. , Smith B. C.
Published: July 2007

Industrial photoconductors are doped for large quantum yields. The resulting improvement in resistive dynamic range is accompanied by photocarrier traps. These traps enhance device hysterisis (or memory). The reduction in response speed mimics electrical reactance effects. This light history may be exploited in the construction of low‐frequency filters and oscillators.
A parallel‐series‐fed microstrip array with high efficiency and low cross‐polarization
Authors: Huang John
Published: July 2007

A linearly polarized traveling‐wave microstrip array antenna is parallel and series fed by microstrip transmission lines. Excellent antenna efficiency is achieved by having proper impedance matching throughout the array and by properly utilizing the reflected power from the end of the array. Very low cross‐polarization radiation is achieved by exciting the patches and transmission lines with antiphase technique.
Laser ablated yba2cu3o7‐x high temperature superconductor coplanar waveguide resonator
Authors: Valco G. J. , Blemker A. R. , Bhasin K. B.
Published: July 2007

We have fabricated and tested several 8.8‐GHz coplanar waveguide resonators made from laser ablated YBa2Cu3O7‐b thin films on LaAlO3 substrates. A quality factor of 1250 at 77 K was measured. A correlation between the microwave performance of the resonators and the critical temperature and morphology of the films was observed.
Dual circularly polarized sequentially rotated microstrip array with high isolation
Authors: Hall P. S.
Published: July 2007

Sequentially rotated feeding improves the axial ratio and input VSWR bandwidths of circularly polarized arrays. However, when dual polarization is wanted, the method is shown not to improve isolation, as is the case for dual linearly polarized arrays. This deficiency is overcome by squinting the beam. Measured results for a small array confirm this and computations for large arrays indicate performance capabilities.
Broadband millimeter‐wave detector using dielectric image line
Authors: Kikuchi Kazuo
Published: July 2007

The broadband millimeter‐wave detector using a dielectric image line is presented. The detector mount is fabricated by a hot carrier diode and a triangular unipole antenna with tapered angle of 16 degree, 39‐degree flare angle and 3.4 mm length. A broadband millimeter‐wave 32–50‐GHz detector is obtained.
S‐band medium‐power mesfet amplifier with high stability
Authors: Samuel M. , Nawarange A. , Mahapatra S.
Published: July 2007

In this Letter a novel technique to design a FET amplifier with potentially unstable FETs is reported. A two‐stage FET amplifier with small signal gain of 20.4 ± 0.2 dB and power output of 23 dBm over the frequency band of 2.3–3.1 GHz is reported. Measured output/input VSWR are also reported.