bluuebunny/crossref_metadata_2025 huggingface dataset:
Cutoff characteristics of composite optical fibers
Authors: Atsuki Kazuhiko , Kaewsuriyathumrong Santi , Yamashita Eikichi
Published: July 2007

This paper applies an improved version of the point‐matching method for estimating the cutoff frequencies of the dominant mode of a class of polarization‐maintaining composite optical fibers and shows an existence condition for nonzero cutoff frequencies of the dominant mode.
Study of mesfets on P‐substrates and on thin P‐layers
Authors: El‐Ghazaly Samir , Itoh Tatsuo , Salmer George
Published: July 2007

The effect of doping of the P‐substrate on the performance of the submicron‐gate MESFET is simulated using a two‐dimensional computer model. It is observed that though increasing the substrate doping results in a better carrier confinement to the active layer, it reduces the drain current. To overcome this problem, a thin fully depleted P‐layer can be introduced between the active layer and the semiinsulating substrate.
Control of millimeter wave devices by optical mixing
Authors: Fetterman Harold R. , Ni Davi D. C.
Published: July 2007

Coherent mixing of optical radiation from a tunable CW dye laser and a stabilized HeNe laser was used to generate broadband microwave signals beyond the Ka band in FETs, HEMTs, and the related devices. Comparing with direct modulation of the light signal, this technique enhances photoconductivity and frequency stability.
Gigahertz‐bandwidth optoelectronic differential amplifier
Authors: Choi Y. A. , Taylor H. F.
Published: July 2007

A wideband differential amplifier for electrical signals using modulated laser diodes and a novel optical receiver design shows better than 25‐dB common‐mode rejection ratio over a bandwidth of greater than 1 GHz.
Determination of the transverse propagation delays in single‐gate GaAs Mesfets
Authors: Goel A. K.
Published: July 2007

A computer‐efficient algorithm for the calculation of the transverse propagation delays in single‐gate GaAs MESFETs is presented. Electrode parasitic capacitances and the electrode contact and metallization resistances have been included in addition to the internal elements in the MESFET. The technique can be used for MESFETs with submicron gate lengths as well.
Contact effects in InP near‐micron transferred electron devices
Authors: Czekaj J. , Shaw M. P. , Grubin H. L.
Published: July 2007

We have performed an experimental and numerical investigation of near‐micron sized InP transferred electron devices having alloyed metal cathode “current‐limiting” contacts. Both a Boltzmann transport equation (BTE) and drift and diffusion analysis were used to simulate the dc and ac results. Both techniques were capable of predicting the dc and amplification characteristics, but only the BTE approach predicted the narrow large‐signal oscillatory bandwidth observed in the experiments. We found that: The devices behaved in a transit time oscillatory mode; subtle differences in contact conditions caused major change in device output frequency, power, and efficiency; the temperature dependence of the current‐voltage characteristic is a strong indicator of the potential device performance.
A versatile reflector antenna pattern computation method: Shooting and bouncing rays
Authors: Lee S. W. , Chou R.
Published: July 2007

Based on shooting and bouncing geometrical optics rays, this paper describes an aperture integration method for computing the secondary pattern of reflector antennas. The method is versatile and flexible. Within the geometricdl optics accuracy, there is virtually no restriction on the number of reflectors, the coating material, radome, or the feed configurations. Pattern computations are shown for an antenna with six reflectors, coated with dielectric material and covered by a spherical radome.
A three‐port microstrip impedance measurement system
Authors: Chang K. , Li M. , Sauter T.
Published: July 2007

A simple and low cost three‐port microstrip impedance measurement system has been developed. The impedance of an unknown load can be easily determined by measuring the coupling power levels at the three probes. The results agree very well with those obtained from an HP8510 automatic network analyzer.
An L‐band monolithic microwave receiver
Authors: Bharj Sarjit S. , Bayrun John , Dayal Har , Paradise Ronald
Published: July 2007

An L‐band receiver using gallium arsenide monolithic integrated technique has been developed for low‐cost manufacture. The front end receiver is comprised of an RF front‐end amplifier, a single‐pole‐double‐throw switch for antenna selection, a local oscillator buffer amplifier, phase splitters, and a double balanced mixer. This paper reports the design, fabrication, packaging, and testing of the complete receiver.
Real‐time optical processing of antenna array signals
Authors: Shamir Joseph , Caulfield H. John , Hendrickson Brian M.
Published: July 2007

Procedures are proposed for writing the phase and amplitude information received by an antenna array onto a coherent laser beam for optical processing.
Mode determination of planar coupled millimeter‐wave oscillators by quasioptical injection locking
Authors: Stephan Karl D. , Young Song‐Lin
Published: July 2007

In the development of planar oscillator arrays for quasioptical power combining, it is desirable to know the relative phase of the individual oscillator currents or voltages. We present a simple quasioptical injection‐locking measurement which is used to determine the operating mode of a two‐device Ka‐band Gunn‐diode oscillator system.
Three‐dimensional finite‐element formulation for deterministic waveguide problems
Authors: Picon O.
Published: July 2007

A finite‐element method for the analysis of 3D‐waveguide problems is formulated using a deterministic approach. The electric field is computed from the TE10excitation field by means of a variational formulation that satisfies divE= 0 even when field singularities exist.
Optimization of the charge distribution function on coupled microstrips by a dielectric layer
Authors: Lee Wei‐Yu , Wang Way‐Seen
Published: July 2007

In this article an optimization method is proposed in the determination of the charge distribution function of a variational expression for the line capacitance of coupled microstrips covered by a dielectric layer. The method is simple and easy for computer evaluation. Consistent results were obtained when compared with those of the previous work.
Error probability of optical PSK systems with nonlinear loop dynamics and postdetection filtering
Authors: Basch E. E. , Kearns R. F. , Brown T. G.
Published: July 2007

We describe a numerical approach to the problem of phase recovery in coherent optical communications systems corrupted by phase noise. Two advantages not present in previous treatments are the facts that the effects of the nonlinearity are treated exactly and a probability distribution for the filtered output is obtained without resorting to upper bounds. The results are applied to a sensitivity calculation for phase‐shift‐keyed systems.
Rf characteristics of a high‐temperature superconductive resonant strip in waveguide
Authors: Chang K. , Pandey R. K. , Skrehot M. K. , Li M. , Gilbert G. R.
Published: July 2007

A resonant strip made of high‐temperature YBa2Cu3O6.5 + x with x < 0.5 superconductor was designed and tested in a X‐band (8‐12 GHz) waveguide. At room temperature no significant resonance was observed. A resonance appeared near 10.68 GHz at low temperature. The loaded Q was measured to be 750, comparable to that of a copper strip.
A dual six‐port network analyzer
Authors: Yeo S. P. , Chu M. C.
Published: July 2007

A network analyzer consisting of two six‐port reflectometers was constructed for use over the WR90 bandwidth. Each six‐port reflectometer comprised a symmetrical five‐port junction and a directional coupler. Laboratory tests indicated that measurement accuracies of ± 0.01 in magnitude and ±2° in phase were obtainable for both reflection and transmission coefficients.
Local millimeter‐wave power transmitted through illuminated semiconductor panel scanned with strip of shadow
Authors: Rahnavard M. H.
Published: July 2007

Moving‐spot‐illuminated semiconductor panels are used in millimeter‐wave image convertors. In order to know the performance of this system, it is required to know the response of illuminated semiconductor panels. In this article local millimeter‐wave power transmitted through an illuminated semiconductor panel scanned with a strip of shadow as a function of scanning velocity, width of the shadow strip, time, etc., are studied.
A markov chain approach for static field analysis
Authors: Fusco V. F. , Linden P. A.
Published: July 2007

The calculation of the static field that exists in many distributed electromagnetic systems is of prime importance since it allows preliminary design at microwave frequencies to be initiated. This article demonstrates how an absorbing Markow chain can be used to solve the Dirichlet problem, thereby yielding useful results such as field potentials, stored energy, and characteristic impedance.

The theoretical basis for this method is developed, then applied to a shielded microstrip line in order to calculate line characteristic impedance. Some of the unique features of the absorbing Markov chain method will be discussed and its relationship to the probabilistic potential theory and finite‐difference techniques elaborated.

The technique of absorbing Markov chains as discussed in this article represents a supplementary solution method to those currently in use and offers the possibility of detailed behavioral studies based on the movement of charged particles.
Polarization insensitive coherent detection using orthogonally polarized optical fields
Authors: Hodgkinson T. G. , Cook A. R. J.
Published: July 2007

Recently reported polarization insensitive heterodyne detection schemes that use the properties of polarized light are all shown to be related to the basic concept of simultaneously using two different frequency, orthogonally polarized optical fields. The various system design options associated with this concept are compared in terms of receiver complexity.
Physically short linear impedance transformers
Authors: McGinn V. P. , Moran W. P.
Published: July 2007

Matching transmission lines of different characteristic impedances with two stratified transmission line sections in cascade are demonstrated. The characteristic impedances of each of these sections will be identical to the impedances to be matched. The overall length of this linear transformer is significantly shorter than one quarter wavelength.
Generalized coupled mode theory of curved multiwaveguide systems
Authors: Cheng Yue‐Hua , Lin Wei‐Gan
Published: July 2007

A generalized coupled mode theory has been developed to analyze curved multiwaveguides from the reciprocity theorem. A simple relationship between local coupling coefficients and local nonorthogonal coefficients is given. Our theory takes account of the field deformation due to waveguide bending, and the nonorthogonality and phase interference between local guided modes in different bent waveguides. It is noted that the generalized coupled mode theory satisfies the reciprocity theorem and power conservation.
Ray‐tube integration in shooting and bouncing ray method
Authors: Lee S. W. , Ling H. , Chou R.
Published: July 2007

Based on three formulations of the Huygen's principle, explicit expressions is given for the far field contribution from a small ray tube. This expression is useful in shooting and bouncing rays for solving complex scattering problems.
The analysis of the gain of brillouin optical fiber amplifier
Authors: Weijian Jiang , Liping Sun , Peida Ye
Published: July 2007

The Brillouin equations with strong nonlinearity are solved using a perturbation technique. The calculated results agree quite well with the published experimental results [1, 2]. In addition some new conclusions are obtained from our analysis.
An interpolation method for measuring the Q‐factor of a quasi‐optical open resonator
Authors: Arora Rajendra K.
Published: July 2007

A method is described by which the Q of a millimeter‐wave open resonator may be determined from the measurement of response at a discrete set of points in the neighborhood of resonance. The method is illustrated by application to a set of experimental data.
Simplified arithmetic for optical symbolic substitution
Authors: Cherri A. K. , Karim M. A.
Published: July 2007

Simplified arithmetic rules for optical symbolic substitution are identified. The proposed scheme involves only one single step and only four symbolic substitution rules for both addition and subtraction of binary numbers.
Numerical convergence in dichroic problems
Authors: Webb Kevin J. , Caroglanian Armen , Grounds Preston W. , Mittra Raj
Published: July 2007

The numerical convergence in the spectral domain formulation of dichroics is addressed using a specific example. The asymptotic forms of the inner products and the issue of relative convergence are discussed. Results from an experimental study are presented together with numerical data using two sets of basis functions.
Hard‐clipping joint transform correlator using a microchannel spatial light modulator
Authors: Yu F. T. S. , Song Q. W. , Suzuki Y. , Wu M.
Published: July 2007

A programmable real‐time optical joint transform correlator that generates sharper autocorrelation peaks is presented. A microchannel spatial light modulator is utilized as the threshold hard‐clipping square‐law device. A liquid crystal television is used to display the input target and reference image. The basic principle of the system and a preliminary experimental result are given.
Optically reconfigured active phased array antennas
Authors: Daryoush A. S. , Choe B.
Published: July 2007

Future generations of phased array antennas for space‐based and airborne platforms are designed based on a large number of active T / R modules. The constructed radiating beam is degraded in the event of modules failure. Simulation results indicate that the control of frequency, interelement spacing, and the individual radiating element pattern alongside the more conventional technique of amplitude and phase can be used to reconfigure the desired radiating beam in the event of the active T / R module failure.
A dynamic model for printed circuit crossover interconnects
Authors: Yang Hung‐Yu , Alexopoulos Nicolaos G.
Published: July 2007

Crossover printed conductors may be used as multilevel chip‐to‐chip interconnects for high‐frequency high‐speed circuits, in VLSI applications, microwave directional couplers, etc. A theoretical model for crossover interconnects is presented in this article. The model accounts for dispersion effects and radiation loss and it may be used for the design of maximum or minimum power transfer between interconnects.
Theory and design of stub tuned nonreciprocal stripline junctions and circulators
Authors: Xu Yansheng , Miao Jianyong
Published: July 2007

In this article a rigorous and effective analysis of microwave ferrite stub tuned stripline junctions and circulators is presented. By using the equivalent parallel plate waveguide and mode matching method, the eigenvalues and scattering parameters of the junction are calculated. A method of design of the stub tuned circulators is given, which is verified by the experimental results. Theoretical and experimental results show that this kind of circulator can be easily designed to have an octave bandwidth.
Beam transformation by defocused imaging lens
Authors: Chu T. S. , Gans M. J.
Published: July 2007

The effects of spherical aberration and beam truncation have been clarified in the beam transformation of laser radiation by a defocused imaging lens. Excellent agreement was obtained between calculated and measured patterns. Amplitude ripples of about 1 dB are primarily caused by interference between geometrical optic rays and edge diffraction rays.
Elastic multiple scattering by randomly distributed spherical scatterers
Authors: Wang Zhi‐Liang , Lin Wei‐Gan
Published: July 2007

From the basic integral equation for multiple scattered fields, the expansions of the fields in terms of vector spherical wave functions, and the translational addition theorems of the vector spherical wave functions, a set of coupled linear equations has been derived for the expansion coefficients of elastic scattering fields by randomly distributed spherical scatterers. Thus, a new theory for this kind of problem is developed. Different from the other theories, this theory gives the multiple elastically scattered fields in all regions.
Microwave response of a hemt photoconductive detector
Authors: Claspy P. C. , Bhasin K. B.
Published: July 2007

Interdigitated photoconductive detectors with 5‐μm geometry have been fabricated on HEMT material and their optical response characteristics at 820 nm have been examined at DC and in the frequency range of 2‐8 GHz. These have been compared with characteristics of similar 1‐μm devices on MESFET material. The shapes of the frequency responses were found to differ, but the useful bandwidth of both types of devices was found to be similar.
On the leaky modes of open microstrip lines
Authors: Michalski Krzysztof A. , Zheng Dalian
Published: July 2007

Dispersion characteristics and modal currents of an open microstrip line are computed using the mixed‐potential electric field integral equation. Particular attention is given to the correct determination of the radiating, leaky‐wave modes.
Matching, gain, and noise limits on linear amplifier four‐poles
Authors: Sierra Manuel
Published: July 2007

Equations showing the limits of gain, input and output matching, and noise behaviour for a linear four‐pole have been developed. Easier device evaluation and amplifier design can be done with these equations.
An exact method for analyzing boxed microstrips on lossy substrates
Authors: Marqués Ricardo , Horno Manuel
Published: July 2007

An exact method for the hybrid mode analysis of shielded microstrip lines on anisotropic and lossy dielectric substrates is presented. The method is based on the MRCT and other modified Wiener‐Hopf techniques. Results are given in tabular and graphic form.
White‐light optical directional frequency false color coding—a new technique
Authors: Deekshatulu B. L. , Bajpai O. P. , Meenakshisundaram P.
Published: July 2007

A real‐time white‐light processing technique for directional frequency false color coding based on optical signal parallel processing is described. The output colors are derived directly from the white‐light source. The procedure to record an output either as a parallel or serial processor is detailed. Experimental results are highlighted.
General analysis of [3 × 3] optical‐fiber directional couplers
Authors: Liping Sun , Peida Ye
Published: July 2007

The general analytic expressions of [3 × 3] optical fiber output are obtained by solving three linear differential equations using Laplace transform techniques. It may prove useful in explaining, designing, and manufacturing of [3 × 3] optical fiber couplers.
Standing wave effects in a symmetrical three‐line microstrip coupler with short‐circuited side lines
Authors: Faria J. A. Brandão
Published: July 2007

The spectral domain analysis of microstrip couplers with lateral ground strips can be conducted following two different approaches: assuming the lateral strips are continuously short‐circuited to ground or discretely bonded to the reference ground conductor at the coupler ends. In this paper, the second approach is used: The wave number and the characteristic admittance of the central strip propagation made of a coplanar three‐conductor microstrip transmission line are determined and shown to depend critically on the coupler length. The spatial evolution of microstrip voltages and currents inside the coupler is also determined and discussed. The results show that noticeable standing wave effects are present when the coupler length comes close to an integer multiple of one‐half wavelength.
Elastic and inelastic scattering by an arbitrary body filled with active molecules: Method of eigenfunction expansion in integral equation
Authors: Wang Zhi‐Liang , Lin Wei‐Gan
Published: July 2007

The integral equation method in [1] is extended to analyze the elastic and inelastic scattering from an arbitrary particle filled with active molecules, and at the same time, the field's correction is taken into account as the field point and source point are at the same location. The electromagnetic fields are expanded in terms of vector spherical wave functions, and the expansion coefficients can be solved from a set of coupled linear equations. Some numerical results and conclusions are given.
A new electromagnetically coupled printed ring radiator
Authors: Sastry N. N. , Lakshminarayana M.
Published: July 2007

A new type of printed radiator has been designed, fabricated, and tested. This radiator is in the form of an annular ring with a narrow break in the form of a slot. The antenna is fed by a microstripline and has yielded a VSWR less than 2.0 over a 20% band width. Because of its low profile construction and large bandwidth, this antenna can find wide application as an element radiator in phased array antennas.
Thin‐film permanent magnet requirements for magnetic devices in MMIC
Authors: Stancil Daniel D.
Published: July 2007

The use of sputtered thin‐film permanent magnets for biasing microwave devices in planar geometries compatible with monolithic integration is considered. Possible geometries are presented for biasing a reciprocal microstrip phaser at 7 GHz, a stripline circulator at 15 GHz, and a magnetostatic wave delay line at 3 GHz. Yttrium iron garnet (YIG) is assumed to be the ferrite used in each of these devices. It is concluded that the in‐plane magnetization orientation is more useful than normal magnetization, and thick films (100‐150 μm) are needed with high magnetization ( > 16 kG) and moderate coercivity ( > 2 kOe). Below‐resonance devices are preferable because of their modest field requirements and tolerance to bias field inhomogeneities.
Low frequency nonlinear fabry‐perot resonator
Authors: Awwal Abdul Ahad S. , Karim Mohammad A.
Published: July 2007

An optical nonlinear Fabry‐Perot interferometer is simulated using a low frequency nonlinear transmission line circuit. The analog model may be used to study the phenomenon of bistability and harmonic frequency generation.
Correlation with a phase‐only matched filter made from outline feature
Authors: Minhua Liang , Min Yu , Liren Liu , Shudong Wu , Zhijiang Wang
Published: July 2007

To obtain a high correlation peak intensity, a high optical efficiency, and high rotation and scale sensitivities, a new method, which can be realized optically, is proposed. Computer simulation results show that this method will have a neater output and better sensitivities than phase‐only matched filter.
Theoretical analysis of the breakdown voltage in InP MISFETs
Authors: de Jaeger J. C. , Fellon P. , Kozlowski R. , Crosnier Y. , Salmer G.
Published: July 2007

The theoretical avalanche breakdown in InP MISFETs is described using a two‐dimensional numerical model based on the calculation of Poisson's equation and the current equation. The study investigates various structures with a full analysis of the potential shape and the electric field distribution which gives complete explanations of the breakdown behaviour of the device. The characteristics of the transistor are determined as a function of the geometry of the structure, and the effects of the main parameters are given: The gate‐drain distance, the insulator zone width, the channel thickness, the doping concentration of the active layer and the shape of the recess.
Scanning tunneling microscopy of thin film surfaces and film steps
Authors: Yue Lin , Xiangzhen Chen , Runwen Wang
Published: July 2007

A novel technique of scanning tunneling microscopy applied to optical surfaces has been analyzed both in theory and experiment in this paper. The profiles of Al, Mo coated film surfaces and multilayer film steps are measured with the scanning tunneling microscope and stylus instrament, whose experimental results are compared and analyzed.
High‐efficiency variable‐power class‐B dual‐gate power fets
Authors: Bahl Inder , Geissberger Art , Griffin Edward
Published: July 2007

We report state‐of‐the‐art measured performance of class‐B dual‐gate GaAs power FETs fabricated using a highly manufacturable SAG technology. The class‐B devices use selective co‐implantation for FET channel formation and demonstrate 640 mW / mm (for 2.5 mm FETs) of power at C‐band with 45% PAE and 11.4‐dB gain.
Near‐field diffraction pattern by an underground void of circular cylinder
Authors: Lee Taek‐Kyung , Park Seong‐Ook , Ra Jung‐Woong , Kim Se‐Yun
Published: July 2007

Amplitude patterns of the electromagnetic field scattered by a circular air cylinder embedded in a dielectric medium are analyzed. Twenty five decibel double dip patterns measured by the scale‐down experiment are presented. Theoretical analysis shows that these double dips become double nulls in the near‐field region. This phenomenon is useful in locating high‐contrast geological anomalies.
Propagation coefficient of the transverse electric mode in a rectangular waveguide with sinusoidally varying width
Authors: Li Guifang , Seshadri S. R.
Published: July 2007

An analytical expression is deduced for the propagation coefficient of the transverse electric mode in a rectangular waveguide with sinusoidally corrugated sidewalls by a perturbation procedure. The accuracy of the present treatment is of the same order as that of the previously obtained numerical results.
Magnitude and phase of the electric field of infinite‐strip, unstable optical resonators using different techniques
Authors: Rahnavard M. H.
Published: July 2007

We calculate the magnitude and phase of the electric field (eigenfunctions) in infinite‐strip, unstable optical resonators which are used in medium‐to‐high power lasers. In this paper physical optics (PO), scalar theory of diffraction (STD), physical theory of diffraction (PTD), approximate physical optics (POA), and geometrical theory of diffraction plus geometrical optics (GTD + GO) methods are used to compute the magnitude and phase of the electric field in infinite‐strip, unstable optical resonators. The results of these different methods are compared. The calculated power loss using eigenvalues corresponding to the calculated electric field (eigenfunctions) are in agreement with previously published calculations.
Band‐pass distributed amplifiers
Authors: Prasad S. N. , Beyer J. B.
Published: July 2007

A novel band‐pass distributed amplifier design concept is presented. The amplifier can be realized in monolithic form using GaAs FETs. The amplifier has excellent wideband gain and phase response characteristics. It shows promise for applications in the millimeter wave region. In this paper the results of analytical modelling as well as computer simulations are discussed.
Analysis of an electrically long, all‐dielectric, fiber‐optic electric‐field sensor
Authors: Atkinson Leonard A. , Kruppa Walter
Published: July 2007

An electrically short fiber‐optic electric‐field sensor has a sensitivity that is proportional to the fiber length. In this paper an analysis is presented for a sensor with an electrically long fiber. The result indicates that zeros will occur in the frequency response. A sensitivity tapering technique is presented which prevents these zeros from occurring.
All‐optical cutoff modulation in gallium arsenide ridge waveguides
Authors: McWright G. , Ross B.
Published: July 2007

We discuss all‐optical cutoff modulation in gallium arsenide integrated optical ridge waveguides for a guide wavelength of 1.3 μ.m. These modulators use the change in refractive index due to electron‐hole pair generation to bring the waveguide to cutoff.
Mutual interaction of the first‐order soliton multipulse series in optical fibers
Authors: Guo Qi , Zhou Guosheng , Lin Weigan
Published: July 2007

It is pointed out that the split step method and the propagating beam method are equivalent and numerically calculated by the method that the initial equal separation first‐order multipulse series propagates in an optical fiber. A possible scheme to increase the bandwidth of an optical soliton communication system is proposed.
A 32 × 32 array for satellite reception
Authors: Russo P. , Ruggieri M.
Published: July 2007

The possible use of microstrip arrays for 12 GHz satellite reception has been evaluated. In particular a 32 × 32 element array has been synthesized that considers both a broadside solution and a beam‐steered approach.

The interesting results that have been achieved show the great promise of planar arrays for end‐user applications.
Large deviation fsk baseband receiver using an optical multiport device
Authors: Betti S. , Curti F. , de Marchis G. , Iannone E.
Published: July 2007

A new large deviation FSK baseband receiver is presented. It is based on an eight port optical multiport that provides phase‐quadrature detection so as to avoid aliasing when the input signal is baseband translated. The multiport device also provides insensitivity to laser intensity noise and suppresses channel intermodulation in FDM systems.
Fabrication of waveguide ‐ fiber array couplers using laser‐machined V‐groove techniques in perspex substrates
Authors: Chung P. S. , Hung W. Y. , Chan H. P.
Published: July 2007

We report an inexpensive and versatile technique for coupling multichannel waveguides to a fiber array using V‐grooves in perspex substrates that are accurately machined by a computer‐controlled CO2 laser system. An excess loss of less than 1 dB could be achieved for coupling between 1 × 2, 1 × 3, and 1 × 4 branching circuits and an array of N‐port fibers.
A phase quadrature square patch microwave coupler
Authors: Merugu L. N. , Fusco V. F. , Stewart J. A. C.
Published: July 2007

Theoretical and experimental results are presented for a square microstrip patch employed as a coupler at 13.2 GHz. The square patch exhibits equal power‐split in phase quadrature over a 7% bandwidth, 5.0 dB coupling, and 17 dB isolation. The effect of packaging on the performance is investigated.
Effective dielectric parameter method — A new method for analyzing propagation characteristics of dielectric waveguides
Authors: Zhendong Shi , Jiang Li
Published: July 2007

The effective dielectric constant method is known for analyzing propagation characteristics of dielectric waveguides. In this paper we discuss the substance of this method. Further, an effective dielectric parameter method having higher accuracy is introduced. The agreement between experimental values and the values calculated by this method is shown to be quite good.
Photoelectrically enhanced microwave imaging
Authors: McGinn Vincent P.
Published: July 2007

An experimental high resolution radar imaging technique is described, which permits magnitude determination of currents and local fields established on an around complex bodies irradiated with microwave energy. This highly useful information reveals radar cross section contributions from constituent parts of larger systems.
Microstrip bandstop and passband filters using gap discontinuities and shorted terminals
Authors: Faria J. A. Brandão
Published: July 2007

This paper presents an analysis of a transversally symmetric three‐line microstrip structure whose side lines have discontinuities. The device is shown to behave as a bandstop or as a passband filter depending on an asymmetry coefficient characterizing the discontinuity localization. Formulas for the filter parameters (attenuation, bandwidth, phase and group velocities, and characteristic wave impedance) are established and design examples are provided to illustrate the analysis results.
Simulation of nonlinear circuits using modified harmonic balance techniques
Authors: El‐Rabaie S.
Published: July 2007

This paper shows a comparative study for two main different approaches of modified harmonic balance techniques. The first modification is based on a broadband sampling theorem and uses simple modifications to the DFT algorithm (called MDFT). The second method is based on a bandpass sampling theorem and is called the controlled aliasing technique.
Error effects on the processing of adaptive array data using the BOC
Authors: Abushagur Mustafa A. G.
Published: July 2007

The Bimodal Optical Computer (BOC) is considered for Adaptive Phase Array Radar (APAR) data processing. The effect of the errors in the BOC and the number of iterations on the optimum weight calculations for the interference cancelling are studied. Computer simulations for five‐and nine‐element APARs are presented.
Restoration of blurred images due to linear motion using a joint transform processor
Authors: Cheng Feng , Xu Xin , Wu Shudong , Yu Francis T. S. , Gregory Don A.
Published: July 2007

In this paper we shall show that blurred photographic images due to linear motion can be restored with a joint transform processor (JTP). The deconvolution function for the image deblurring can be directly implemented at the input plane of a JTP. The bipolarity of the deconvolution function can be accomplished by encoding with a ±‐shifted grating structure. Computer simulations to test the feasibility of the scheme are given.
Mechanical displacement measurement by single‐mode fiber optic and moving mirror
Authors: Bakalidis George N. , Georgopoulos Chris J.
Published: July 2007

In this paper a theoretical model of a mechanical displacement sensor based on the theory of the optical Gaussian beam emerging from an optical single mode and the recoupling through a multimode optical fiber is presented. The developed model presents a dynamic region of measurements from 0 to 130 μm.
Radiation and surface waves of a microstrip antenna covered with a dielectric layer
Authors: Hoorfar Ahmad , Gupta K. C. , Chang D. C.
Published: July 2007

The effects of a thick cover layer on the radiation characteristics of a microstrip patch antenna are investigated. A magnetic line source model has been used to derive explicit expressions for the far field, radiated power, directivity, and surface wave of the antenna. Numerical results are presented to show the effects of a lossless as well as a lossy dielectric cover layer on the surface waves and the radiated power.
Experimental determination of the resonance frequencies of suspended‐substrate microstrip antennas
Authors: Lin C. C.
Published: July 2007

A simple experimental method is presented which enables the determination of the resonance frequencies of suspended‐substrate microstrip antennas. Resonance frequencies have been measured in L‐band for square patch‐antennas in “suspended‐substrate” as well as in “inverted” configurations. The relationship between the above measured resonance frequencies and the input impedances of the corresponding patches is also shown.
Calculations on the increased sensitivity of dielectric constant measurements using open‐end coaxial line with a hemispherical center conductor extension
Authors: Xu Yansheng , Bosisio Renato G.
Published: July 2007

In this paper, the method of measurement of dielectric constant by using open‐ended coaxial lines with a hemispherical center conductor extension is examined in great detail. Calculation results show that this method can considerably improve the sensitivity of measurement while retaining the advantages of a simple mechanical construction. Such a probe is conveniently used with any material that can intimately embrace the hemispherical tip of the probe (e.g., liquids, fine powders, etc.).
Characteristic impedance for double‐sided slotlines
Authors: Coetzee Jacob C. , Malherbe Johannes A. G.
Published: July 2007

Computed results on the characteristic impedance of double‐sided slot‐lines on low‐permittivity substrates are presented. Curves for ϵr= 2.22, 3.0, and 3.8 are included. A spectral Galerkin method is employed to calculate the slotline wave number and the slot electric field. The characteristic impedance is then calculated in the spectral domain from the slot field.
Near field radiation from four coaxial line fed structures
Authors: Nevels Robert D. , Ed Wheeler J.
Published: July 2007

Near field time‐average power distribution and radiation direction patterns are presented for a coaxial line flush‐mounted on an infinite ground plane and terminated with (a) an infinite homogeneous half space, (b) a hemispherical extended center conductor, (c) a hemispherical dielectric cover, and (d) a hemispherical extended center conductor with a dielectric coating. Expressions are given for the electric and magnetic fields and Green's functions for the dielectric coaled conducting hemisphere case, from which the fields and Green's functions for the other three cases can be constructed. Each of the four structures described here is either in use or has potential applications as an antenna or as a component in an external medium dielectric constant measurement system.
Scattering of a tem wave from a time varying surface
Authors: Elcrat Alan R. , Harder T. Mark , Stonebraker John T.
Published: July 2007

A solution is given for reflection of a plane wave with TEM polarization from a planar surface with time varying properties. These properties are given in terms of the currents on the surface. The solution is obtained by numerically solving a system of differential‐delay equations in the time domain.
A variable‐gain constant‐phase dual‐gate amplifier with series feedback
Authors: Willems David , Bahl Inder , Pollman Mike , Coluzzi Michael , Tantod Shukdev , Andricos C.
Published: July 2007

This paper presents series feedback used in a variable‐gain constant‐phase dual‐gate amplifier for T / R module applications. The inductive series feedback element shifts the input match of the dual gate FET to an impedance that is much easier to match 50 ohms. This allows the amplifier to have a much broader bandwidth and increased gain while maintaining constant phase in the different gain states. This amplifier was fabricated as a MMIC chip using the ITT MSAG process, and we obtained excellent performance: variable gain range of 13 dB, VSWR better than 2.0:1, phase variation less than ±2°, and gain flatness of ±0.4 dB over the 4.5‐6‐GHz frequency range.
An improved all‐fiber 90° optical hybrid
Authors: Kejian Guan , Yizun Wu
Published: July 2007

In this letter, an improved all‐fiber 90° optical hybrid is reported. The experimental unit has the following characteristics: low insertion loss, high stability, wide operation bandwidth, and simple fabrication process of all functional components. The unit will find applications in phase diversity coherent optical communication systems and interferometric sensing systems.
Characteristic modes for nonconducting bodies having mutually orthogonal symmetry planes
Authors: Vescovo Roberto , Corzani Tullio
Published: July 2007

We consider the characteristic modes of lossy or loss‐free dielectric and / or magnetic bodies symmetric with respect to mutually orthogonal symmetry planes. For such cases, we show that the moment method can be applied to the eigenvalue equation defining the modes, transforming it into a matrix eigenvalue equation involving matrices partitioned into diagonal blocks.
Green's function for the poisson equation in the domains bounded by two intersecting spheres
Authors: Lin Weigan , Jin Hang
Published: July 2007

The Green's functions for the Poisson equation in the domains bounded by two intersecting spheres with Dirichlet boundary conditions is presented. As an illustration of the application, the perturbation of a thick wall conducting spherical cavity with a circular aperature in a uniform static field is treated.
On phase‐shift position and linewidth of λ/4‐shifted DFB laser diodes
Authors: Ghafouri‐Shiraz H. , Chu C. Y. J.
Published: July 2007

The phase‐shift position (PSP) of a λ/4‐shifted distributed feedback (DFB) laser diode affects many characteristics of the laser. In particular, the effects of PSP on stability and external differential quantum efficiency for single longitudinal mode (SLM) operation of the laser were investigated previously by many authors. In this letter, a theoretical analysis of the effect of PSP on the spectral linewidth of the laser is presented. The results revealed the necessity of trade‐off in optimizing the PSP for a laser diode with a narrow linewidth while maintaining a sufficient stability and efficiency.
Monte carlo simulations of scattering of waves by a random rough surface with the finite element method and the finite difference method
Authors: Lou S. H. , Tsang L. , Chan C. H. , Ishimaru A.
Published: July 2007

The finite element and the finite difference methods are applied to Monte Carlo simulations of random rough surface scattering. The advantages of these methods are the banded nature of matrix and the reduction of computer time. These results are also compared with those of Kirchhoff approximation and those of small perturbation theory when applicable.
Approximate formulae for the surface wave numbers in a grounded dielectric structure
Authors: Bhattacharyya Arun K.
Published: July 2007

Approximate formulae for the radial wave numbers of the surface wave modes in a grounded dielectric structure are presented. These were obtained by using the concept of successive approximation iteration scheme. Numerical results compare well with the actual values of the surface wave number.
Theory and design of wideband 3‐dB suspended microstrip couplers with floating conductor
Authors: Karam Michel , Demers Yves , Xu Yansheng , Bosisio Renato G.
Published: July 2007

Using the spectral domain method, theoretical analysis of the characteristics of coupled suspended microstrip lines with floating conductor is presented in detail. The distributions of electrical charges on the coupled microstrip lines and floating conductor are studied, and a set of basis functions used in the calculation is obtained. Detailed numerical results and design curves are presented, and an experimental wideband 2.5‐dB coupler is designed and measured. The test results are in agreement with theoretical values. This type of coupler is simple in construction and capable of realizing tight coupling (3 dB or higher) in microwave integrated circuits (MIC) with high directivity.
High‐efficiency diffraction modulation of light by strain‐optic effect of piezoelectrically induced standing acoustic waves in bulk LiNbO3 crystal
Authors: Kuti Cs. , Turi I. , Yan Li , Lee Chi H.
Published: July 2007

100% modulation of light was achieved by the strain‐optic effect of the piezoelectrically induced standing acoustic waves in a bulk LiNbO3 crystal. The modulation index as high as 4 was attained. As a result, in a single pass a continuous wave light has been modulated resulting in transmission peaks of width less than 2 ns at a repetition rate of 100 MHz.
Analysis of arbitrarily shaped COAX‐FED microstrip antennas—a hybrid mixed‐potential integral equation approach
Authors: Zheng Dalian , Michalski Krzysztof A.
Published: July 2007

Arbitrarily shaped coax‐fed microstrip patch antennas on thick substrates are studied using a hybrid mixed‐potential integral equation approach, which incorporates a triangle‐element model of the patch and a simplified treatment of the probe‐to‐patch junction. Computed input impedance data are shown to agree well with measured results.
Microwave characterization of high‐temperature superconducting thin films using stripline resonators
Authors: Macdonald Alan D. , Long Stuart A. , Williams Jeffery T. , Jackson David R. , Lichtenberg Christopher L. , Davis Matthew L. , Wosik Jaroslaw L. , Wolfe John C.
Published: July 2007

A method was derived for the extraction of the surface resistivity (Rs) of high Tc superconducting (HTS) thin films at microwave frequencies using a stripline resonator circuit. Surface resistivity values were calculated by measuring the difference in Q‐values of a stripline resonator configuration when an HTS thin film was substituted for one of the metallic ground planes. Cryogenic tests were completed for several stripline resonator structures, yielding accurate predictions of the HTS thin‐film performance at frequencies between 3 and 26 GHz (in harmonics of approximately 3 GHz). These results were then used to illustrate the dependence of HTS surface resistivity on frequency and temperature in the microwave frequency band.
Measurements of signal transmission to 20 GHz and crosstalk to 10 GHz on small copper microstrips embedded in polyimide dielectric
Authors: Loos J. S. , Engvik A. H. , Lin M. S. , Lin‐Hendel C. G.
Published: July 2007

Multi‐GHz measurements of signal propagation and crosstalk are reported for small, somewhat resistive, copper microstrips (20‐30 μm width and 2‐3 μm thickness) that are embedded in polyimide dielectric and fabricated on a silicon substrate. The transmission, reflection, signal velocity, and crosstalk on 50‐Ω terminated microstrips are well behaved and, moreover, are well described by standard transmission line theory when resistive losses (corrected for the skin effect) are included.
Optoelectronic implementation of local cellular logic with polarization coding
Authors: Zhang Li , Liu Liren
Published: July 2007

An optoelectronic architecture is suggested to perform local cellular logic. A polarization coding technique along with the electronic substraction and thresholding techniques are developed to complete the operations with both positive and negative interconnections. Experimental results of the Laplacian operator for edge enhancement and their numerical simulations are given.
A method for optimizing efficiency and power dissipations in high power microwave/ millimeter‐wave amplifiers
Authors: Larose Robert , Ghannouchi Fadhel M. , Bosisio Renato G.
Published: July 2007

An alternative method for large signal characterization of microwave / millimeter‐wave power transistors suitable for high power amplifier design is presented. Constant output power contours, constant added‐power efficiency contours, and constant power dissipation contours over the full Smith chart are obtained for a NEC 71083 MESFET.
A note on the use of a beam‐waveguide feed system as a phase shifter for high power microwave dual‐reflector antennas
Authors: Knop C. M.
Published: July 2007

A diffraction analysis and associated computations of the transmission loss of a typical BWFS (beam‐waveguide feed system) used to excite an HPM (high power microwave) DRA (dual‐reflector antenna) are reported and show that the use of a BWFS as a phase shifter, as proposed by Hansen and Palaith in early 1989 [1], is reasonable since this phase‐shift action increases this loss by an acceptably low amount.
Analysis of microstrip‐like transmission lines with finite metallization thickness
Authors: Tan Chung‐Hsing , Chang The‐Nan
Published: July 2007

The transverse modal analysis (TMA) method is used for deriving the dispersion characteristics of microstrip‐like transmission lines with finite metallization thickness. Instead of using strip currents as source quantities, the aperture fields are employed for applying the Galerkin method. Numerical results show that the metallization thickness will decrease the propagation constant of both shielded microstrips and suspended strip lines. To verify the accuracy of the present method, the results are also compared with those obtained by other methods.
Ka‐band monolithic GaAs mesfet amplifier design
Authors: Rollman J. A. , Wahid P. F.
Published: July 2007

Three designs, a single‐stage, a parallel‐stage, and a two‐stage amplifier, for medium power monolithic GaAs MESFET amplifiers at Ka‐band are presented. The results obtained are consistent with other performances reported at these frequencies.