bluuebunny/crossref_metadata_2025 huggingface dataset:
Tribo‐investigation of PEEK‐short carbon fibre composites in severe testing conditions
Authors: Lal Babu , Mathur Gyanesh Narayan
Published: July 2007

A series of composites of polyetheretherketone (PEEK) containing short carbon fibre (CF) in the range of 0–30% (w/w) was developed. Their wear behaviour in low amplitude oscillating wear (LAOW) mode was studied under various operating parameters such as load and temperature. The LAOW mode was studied in ball‐on‐plate configuration against steel (100 Cr 6) at ambient temperature and at 100°C. In this mode, the coefficient of friction (µ), specific wear rate (Ko) and limiting loading pressure‐sliding speed (PV) values were investigated. It was observed that with increase in %CF, the wear performance and utility of PEEK (limiting PV value) improved significantly. Thirty percent CF was best performing composite in all aspects. The µ, however, was hardly influenced with the inclusion of CF or variation in operating parameters. The same composites were also evaluated in abrasive wear mode to study the influence of severe operating conditions on wear and friction performance. In this wear mode, the CF‐filled composites showed poorer wear resistance than did neat PEEK. The specific wear rate was correlated with strength properties and it was observed that these composites closely followed the predictions of the Ratner–Lancaster plot. Scanning electron microscopy was used to examine the microstructural features of worn surfaces. Copyright © 2007 John Wiley & Sons, Ltd.
Street markets as tourist attractions—Victoria Market, Auckland, New Zealand
Authors: Kikuchi Ayaka , Ryan Chris
Published: July 2007

The paper reports findings from a qualitative study of 25 respondents visiting Victoria Market, New Zealand as to their motives for visiting a market, and their perceptions of this specific market. Open‐ended questioning based on semi‐structured conversation created data analysed using the neural network program CATPAC. The findings note three forms of shopping, the role of cultural components in the market and an appreciation of the market's colourful ambience. However, visitors from Europe still tended to look for value for money when buying objects and had concerns over perceived ‘authenticity’ while Asian shoppers tended to value more the overall ambience. Copyright © 2007 John Wiley & Sons, Ltd.
The impact of the perception of risk on international travellers
Authors: Kozak Metin , Crotts John C. , Law Rob
Published: July 2007

The primary objective of this paper is twofold: (i) to investigate the impact of perceived risk on the tendency to travel internationally; and (ii) to explore if there is any difference in the perception of risky places among three clusters segmented based on the Hofstede's uncertainty avoidance index. The sample population of the study consists of 1180 international travellers visiting Hong Kong in the fall of 2003. The research findings show that the majority of travellers are more likely to change their travel plans to a destination that has elevated risk while the minority reports they are more unlikely. These findings suggest that international travellers appear to be sensitive towards the occurrence of any type of risk in their evoked destinations. Differences were also observed from one continent to another in terms of the influence of perceived risks. The final note is that travellers from different national cultures may have varying degrees of the perceived risk. Implications both for theory and practitioners are also discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Ignition and oxidation of 1‐hexene/toluene mixtures in a shock tube and a jet‐stirred reactor: Experimental and kinetic modeling study
Authors: Yahyaoui M. , Djebaïli‐Chaumeix N. , Dagaut P. , Paillard C.‐E. , Heyberger B. , Pengloan G.
Published: July 2007

The oxidation of several binary mixtures 1‐hexene/toluene has been investigated both in a shock tube and in a jet‐stirred reactor (JSR). The self‐ignition behavior of binary mixtures was compared to that of neat hydrocarbons studied under the same conditions. Furthermore, molecular species concentration profiles were measured by probe‐sampling and GC/MS, FID, TCD analyses for the oxidation of the mixtures in a JSR. Experiments were carried out over the temperature range 750–1860 K. Mixtures were examined under two pressures 0.2 and 1 MPa, with 0.1% initial concentration of fuel. The equivalence ratio was varied from 0.5 to 1.5. The experiments were modeled using a detailed chemical kinetic reaction mechanism. The modeling study showed that interactions between hydrocarbons submechanisms were not limited to small reactive radicals. Other types of interactions involving hydrocarbon fragments derived from the oxidation of the fuel components must be considered. These interactions mainly consist of hydrogen abstraction reactions. For example, benzyl radical that is the major radical produced from the oxidation of toluene at high temperature can abstract hydrogen from 1‐hexene and their products such as hexenyl radicals. Similarly, propyl, allyl, and hexenyl radicals that are the major radicals produced during 1‐hexene oxidation at high temperature can abstract hydrogen from toluene. Improved modeling was achieved when such interaction reactions were included in the model. Good agreement between experimental and calculated data was obtained using the proposed detailed chemical kinetic scheme. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 518–538, 2007
Price rigidity and market power in German retailing
Authors: Weber Sascha A. , Anders Sven M.
Published: July 2007

This paper presents empirical evidence on the interplay important topics of consumer price rigidity and market power in the German food retail industry. In particular, the analysis addresses the causal relationship between market structure—collusion—and pricing behaviour highlighted in the industrial organization literature. Extensive analysis of retail scanner data across beef and pork products reveals considerable differences in price rigidity across store types. Supermarket pricing behaviour is evaluated with respect to all price changes retail sales action and price adjustments indicating that food discounters exhibit the highest degree of rigid prices. Retail concentration, as an important explanatory factor of price stickiness is investigated via the analysis of retail market power employing a conjectural‐variation approach. The analysis of market conduct in the marketing of beef and pork products indicates simultaneous oligopolistic and oligopsonistic behaviour of retail firms. Copyright © 2007 John Wiley & Sons, Ltd.
Waveguide cavity perturbation method for measuring complex permittivity of water
Authors: Mathew K. T. , Raveendranath U.
Published: July 2007

An accurate method of measuring the complex permittivity of high‐loss liquids like water by use of a waveguide perturbation technique is presented. The sample taken in a thin capillary tube of low‐loss material is inserted in the S‐band waveguide cavity. Resonance frequency and frequency shift are measured with a H. P. network analyzer and the complex permittivity is calculated. This method is particularly useful in the case of high‐loss liquids. Another advantage of this method is that only a very small quantity of liquid is needed for the study. © 1993 John Wiley & sons, Inc.
Effects of absorbent materials on the RCS of a partially coated scatterer
Authors: Zhendong Shi , Chunsheng Ding , Yi Jia
Published: July 2007

An expression of the RCS of a partially coated scatterer to evaluate the effects of absorbent materials and the deviation from physical similarity between models and prototype for lack of requiring absorbent materials in model testing has been given. A comparison between theoretical and experimental values for a conducting cylinder partially coated with absorbent materials has shown good agreement. © 1993 John Wiley & sons, Inc.
Photodetector modeling for optical receivers integrated in a silicon process
Authors: Khalil R. , Roulston D. J. , Parker J. R. , Hamel J. S. , McGregor J. M.
Published: July 2007

A new photodiode model for circuit simulation has been developed for use in feasibility and performance studies on silicon integrated fiber‐optical detector systems. The model includes optical absorption and signal current generation from three regions: surface layer, space charge layer, and substrate. This article describes the diode model and includes simulation results for an integrated silicon fiberoptic detector system with ECL outputs, useful for optical interconnect applications such as on‐board clock distribution. Results are included for both the diode itself, showing its multipole response and the complete circuit. © 1993 John Wiley & sons, Inc.
The theory of multilayered spherical chirodome
Authors: Yin Wenyan , Li Pao
Published: July 2007

In this article, expressions of the dyadic Green's function (DGF) of an electric current located in a multilayered spherical chirodome are given using the method of scattering superposition. The radiated field and normalized radiation resistance for a dipole antenna placed at the center of spherical chirodome are studied. The results show that we can regulate the polarized state of radiated fields by choosing the chirodome's size and material parameters properly. © 1993 John Wiley & sons, Inc.
Novel propagation features of dielectric planar chirowaveguides due to nonreciprocity
Authors: Paiva Carlos R. , Topa António L. , Barbosa Afonso M.
Published: July 2007

The effect of a substrate's nonreciprocity on the surface modes of a grounded chiroslab guide is investigated. It is shown that, for any surface mode, a bound on the magnitude of the nonreciprocity parameter exists, beyond which the mode is at cutoff. Furthermore, in the nonreciprocal achiral limit, the slab guide can only support TE modes—whereas in the reciprocal achiral limit both TE and TM modes can propagate. © 1993 John Wiley & sons, Inc.
A technique to improve the accuracy of numerical inverse‐scattering solutions for dielectrics
Authors: Caorsi Salvatore , Ciaramella Stefano , Gragnani Gian Luigi , Pastorino Matteo
Published: July 2007

This article describes a technique to reduce the poor conditioning of linear systems to be solved for numerical inverse‐scattering solutions based on integral formulations and on the moment method. Some preliminary results are reported to show the improvement over a previously proposed approach. © 1993 John Wiley & sons, Inc.
Static image theory for BI‐isotropic media with plane parallel interfaces
Authors: Lindell Ismo V.
Published: July 2007

Image theory for an interface between two bi‐isotropic (BI) media is introduced for the electric and magnetic static source. It is seen that for an electric or magnetic source alone, the images for the reflected fields and the transmitted fields are in general combinations of electric and magnetic sources. The method can be generalized to problems of muttilayered bi‐isotropic media, for example, for the microstrip geometry with a chiral or bi‐isotropic layer. © 1993 John Wiley & sons, Inc.
Full‐wave analysis of finite large printed dipole arrays using the conjugate gradient— FFT method
Authors: Zhuang Yuan , Wu Keli , Wu Chen , Litva John
Published: July 2007

The full‐wave analysis of finite large printed dipole arrays is performed by the conjugate gradient‐FFT method with full‐wave discrete image technique. The CG‐FFT method has the merits of saving computer memory and computing time. So it is very suitable for the efficient analysis of large printed dipole arrays by combining with the discrete image technique which can convert the spectrum‐domain problem into the spatial domain without losing any full‐wave information. Several types of finite large printed dipole arrays are analyzed and discussions are made according to the numerical results. © 1993 John Wiley & sons, Inc.
Analysis of coupled cylindrical substrate microstrip lines by the method of lines
Authors: Rushan Chen , Dagang Fang , Xinguo Li
Published: July 2007

In this article analysis of the coupling between cylindrical substrate microstrip lines by using the method of lines (MOL) is given. Numerical examples are also given. The results are in good agreement with those obtained by the spectral‐domain approach (SDA). This fad supports the correctness and validity of this method. © 1993 John Wiley & sons, Inc.
Static characterization of offset asymmetric microstrip GAP discontinuities
Authors: Martel Jesus , Boix Rafael R. , Horno Manuel
Published: July 2007

The capacitances appearing in the equivalent circuit of the offset asymmetric microstrip gap discontinuity are determined in the case in which the metallizations of the discontinuity are embedded in a multilayered anisotropic substrate. The excess charge densities on the conducting strips of the discontinuity are obtained by using the Galerkin method in the spectral domain. A wide variety of results is provided to demonstrate the generality of the study carried out. © 1993 John Wiley & sons, Inc.
A compact slot loop antenna
Authors: Cai M. , Kool P. S. , Leong M. S.
Published: July 2007

A compact slot loop antenna is proposed and investigated experimentally. The antenna consists of a slot loop printed on a substrate, and is fed by a coaxial cable. The loop perimeter is about λ/2 and the area of the antenna is about 1/8 of that of a microstrip antenna with the same operating frequency. The operating bandwidth (defined by return loss less than or equal to ‐10 dB) of the antenna is quite large (22%). The gain is comparable with that of a λ/2 dipole. The antenna should find wide applications in TV reception, mobile communications, and satellite communications. © 1993 John Wiley & sons, Inc.
Effects of variance in the size of the scatterer on its radar cross section
Authors: Zhendong Shi , Qing Li
Published: July 2007

For scale‐model measurement of the RCS of a lossy target, it is difficult to meet all the requirements of physical similarity [1], especially in the constitutive parameters of the absorbent materials because of their frequency dependence. One often avoids this problem by keeping the wavelength of incident radiation fixed with the sizes of the target scaled down. In this case, the scale factor to evaluate the RCS of prototype from that of a scale model must be found. This article gives brief expressions of the RCS and the scale factors for simply shaped scatterers by means of a PO approximation and the method of stationary phase. It is found that the physical scale factor q2 is not always proportional to the geometrical scale factor p2, but to p to the powers of 2‐4 for a variety of shaped scatterers, respectively, provided their characteristic dimensions are much greater than the working wavelength. © 1993 John Wiley & sons, Inc.
Performance of two single‐layer frequency‐selective surfaces as spatial filters
Authors: Chandran Sathish , Vardaxoglou John C.
Published: July 2007

Two single‐layer FSSs are presented as radiation filters in conjunction with a conventional horn antenna. The amplitude of the transmitted wave to the variation of the incidence angle is studied with a view to designing a spatial filter array. It is demonstrated that these single‐layer arrays act as spatial filters, following a simple design of a regular plurality of slotted elements. © 1993 John Wiley & sons, Inc.
A novel type of compact coplanar waveguide antenna
Authors: Cai M. , Kool P. S. , Leong M. S.
Published: July 2007

A coplanar waveguide antenna (CWA) is proposed and investigated experimentally. The CWA consists of an open coplanar waveguide circuit and is fed by a coplanar waveguide with a characteristic impedance of 50 Ω. The measured return loss shows that the radiation mainly comes from the slot surrounding the open coplanar waveguide circuit. The area of the CWA is about 1/8 that of the corresponding microstrip antenna. © 1993 John Wiley & sons, Inc.
A simple method of calculating the capacitance of an insulated conductor
Authors: Zhou Xingling , Lin Weigan
Published: July 2007

This article will employ very simple mathematics to calculate the capacitance of an insulated conductor of arbitrary shape. Simple but accurate enough formulas are found. As examples, three cases are given in this article. © 1993 John Wiley & sons, Inc.
Butterworth‐like filters using a S‐shaped two‐coupler optical fiber ring resonator
Authors: Ja Y. H.
Published: July 2007

We propose that a S‐shaped two‐coupler optical fiber ring resonator be used to realize the periodic Butterworth‐like bandpassing and band‐locking filters. The dependence of the characteristics of the Butterworth‐like filter on major parameters of the fiber and the couplers are studied and presented as graphs. © 1993 John Wiley & sons, Inc.
Static image method for layered isotropic and BI‐isotropic cylinders
Authors: Lindell Ismo V.
Published: July 2007

Image principle to two‐dimensional static problems involving the cylinder geometry is introduced through a coordinate transformation which makes use of known image solutions developed for the corresponding planar problems. Because the method is not dependent on the medium, the image theory recently developed for bi‐isotropic planar problems can be transformed to be applicable to bi‐isotropic cylindrical problems. The image of a line charge outside of and parallel to a bi‐isotropic cylinder is seen to consist of a pair of electric and magnetic line charges which give the exact scattered field outside the cylinder. Extension to layered cylinders is straightforward. The method can be applied, for example, to quasistatic analysis of microstrips on a bi‐isotropic or chiral cylinder. © 1993 John Wiley & sons, Inc.
Input impedance of coaxially fed rectangular microstrip antenna on electrically thick substrate
Authors: Chen Wei , Lee Kai‐Fong , Lee R. Q.
Published: July 2007

Input‐impedance results for a probe‐fed rectangular patch antenna are presented, using a full‐wave spectral‐domain analysis. The source is modeled by a magnetic‐current frill and multiple modes are used in the probe surface current to account for axial and azimuthal variations. Several new features are noted. © 1993 John Wiley & sons, Inc.
On the use of the surface impedance approach in the quasi‐tem analysis of lossy and superconducting strip lines
Authors: Marques R. , Aguilera J. , Medina F. , Homo M.
Published: July 2007

In this article we propose a mixed quasi‐TEM surface‐impedance (SI) approach for the analysis of metallic losses in MMICs and of superconductivity effects in microstrip lines. Our results show that the quasi‐TEM‐SI technique is a very interesting choice to compute these effects. © 1993 John Wiley & Sons, Inc.
Estimation of the Q values of the dielectric material of the TE:16 dielectric resonator shielded by a metal case
Authors: Konishi Yoshihiro
Published: July 2007

The measurement of the Q values of the dielectric resonator is described, where the dielectric loss and the conductive loss are separately estimated. The experimental results are also shown together with the known data for several materials. © 1993 John Wiley & Sons, Inc.
Full‐wave calculation of the radiation impedance of microstrip‐excited magnetic surface waves
Authors: Lee Jae‐Hyun , Ra Jung‐Woong
Published: July 2007

The radiation impedance of a microstrip having ferrite film and its dependence on the width of the microstrip and the height of the ferrite film are calculated by the full‐wave moment analysis. Full‐wave calculations closely predict the measured radiation resistance, while the magnetostatic approximation deviates in the higher‐frequency region. © 1993 John Wiley & Sons, Inc.
Plane‐wave propagation in a transversely bianisotropic uniaxial medium
Authors: Lindell Ismo V. , Viitanen Ari J. , Kolvisto Paivi K.
Published: July 2007

The transversely bianisotropic uniaxial medium considered in the present article can be obtained, e.g., by mixing metal helices with an isotropic base medium in such a way that the axes of the helices are randomly oriented but perpendicular to a fixed direction in space. The medium is a generalization of the well‐studied chiral medium, and is somewhat similar to the recently studied axially bianisotropic uniaxial medium, which has interesting polarization properties. Plane‐wave propagation in the medium is studied and the solution for the dispersion equation is given. Numerical examples for the wave numbers corresponding to the two eigenwaves of the medium are displayed. It is seen that, unlike in the axially bianisotropic uniaxial medium, there are no optical axes in the present medium, in general. © 1993 John Wiley & Sons, Inc.
An equivalent circuit model of the optical probe in electro‐optical sampling systems
Authors: Song Jian , Conn David , Wu Xiaohua , Nickerson Kent
Published: July 2007

An equivalent circuit approach to modeling of the electro‐optic sampling structure is proposed for the first time. The influence of the optical probe to S parameters of the coplanar waveguide test structure is modeled by an equivalent circuit consisting of the analytic approximations and lumped circuit elements. The model coefficients are optimized by fitting the full‐wave field simulation results. The model is dependent on the test structure geometry and material parameters.
Improved scattering model for weak broad‐wall slots
Authors: Rengarajan Sembiam R. , Derneryd Anders
Published: July 2007

Scattering properties of resonant broad‐wall slots cut in rectangular waveguides for radiation and coupling applications are generally computed from a method‐of‐moments solution of pertinent integral equations. For weak slots, characterized by small values of offsets and tilts, there is a discrepancy between theory and experiment, because of simplifying assumptions made in theory. We present an improved scattering model for such slots with a correction term obtained from experimental measurement. © 1993 John Wiley & Sons, Inc.
Stokes‐parameter detection experimental results for polarization modulation coherent systems with low bit‐rate‐to‐linewidth ratio
Authors: Betti S. , Curti F. , de Marchis G. , Iannone E. , Trifiletti A.
Published: July 2007

A BER measurement has been performed relative to each Stokes parameter in an ASPSK system using laser sources such that the beating signal linewidth exceeds the bit rate (about 200%). Under such severe conditions a sensitivity of about 155 photons/bit has been achieved at a BER of 10−9, with a penalty of about 6 dB with respect to the quantum limit of an ASPSK system. © 1993 John Wiley & Sons, Inc.
A novel frame phase extraction technique for optical‐fiber digital PPM
Authors: Elmirghani Jaafar M. H. , Cryan Robert A. , Clayton F. M.
Published: July 2007

The problems of achieving slot synchronization and the proper frame frequency in optical fiber digital PPM were previously studied. Self‐synchronization of the PPM format is completed here by considering the extraction of the frame phase directly from the incoming data. An original novel technique that utilizes naturally occurring sequences has been devised and used to extract the frame phase in optical‐fiber digital PPM. Original results are reported that identify two classes of naturally occurring PPM sequences. An original mathematical model is developed and used to predict the spectral properties of these sequences. A generalization of the analysis and implementation techniques is carried out that results in synchronizers that can cope with large PPM word sizes. The improvement in the spectral discrete components per extra tracked sequence is shown to be 6 dB. Original practical results are given and shown to be in agreement with the theoretical results. © 1993 John Wiley & Sons, Inc.
Fabrication of optical fabryperot interferometer in LiNbO3 waveguide
Authors: Liang Jia Yi
Published: July 2007

This Letter presents a simple repeatable technique for fabricating a Fabry‐Perot interferometer in a LiNbO3 waveguide. The main contribution to the optical losses of the waveguide resonator due to the wedge angles is theoretically analyzed for the first time. A waveguide Fabry‐Perot interferometer was fabricated in the waveguide with wedge angles of less than 0.01° achieved. © 1993 John Wiley & Sons inc.
Biconjugate gradient method for bistatic scattering calculations
Authors: Wandzura Stephen
Published: July 2007

It has recently been observed that the symmetric case of the biconjugate gradient method renders a variational formula for the monostatic scattering amplitude stationary in the available Krylov subspace at each iteration. In this Letter I point out that the general biconjugate gradient method makes stationary the analogous variational formula for a bistatic scattering amplitude and suggest likely practical benefits accruing from this property. © 1993 John Wiley & Sons, Inc.
On the modal analysis of multiple and asymmetrical irises in a rectangular waveguide
Authors: Yeo T. S. , Leong M. S. , Kool P. S. , Lee Y. K.
Published: July 2007

A new interpretation based on matrix condition number is introduced for the accurate determination of the desired break‐knee points in Mastermann's break‐point analysis of waveguide discontinuity junctions. The modified technique is favorably tested on multiple and asymmetrical iris problems. © 1993 John Wiley & Sons, Inc.
The focal points of radially stratified spherical chirolenses
Authors: Wenyan Yin , Pao Li
Published: July 2007

The electromagnetic properties of radially stratified spherical chirolenses are examined using the dyadic Green's function, and a general formulation is presented for determining the focal points of in‐homogeneous spherical chirolenses. Also, the focal points of Luneberg chirolenses are calculated. It is shown that chirality admittance has strong influence on the location of focal points. © 1993 John Wiley & Sons, Inc.
Using inductive series feedback to stabilize a microwave distributed amplifier with high gain fets: A new design approach
Authors: Paixato Oswaldo P. , Souza Rui F. , Kretly Luiz C.
Published: July 2007

Numerical results are presented to show how series inductive feedback between the source of the FET and ground, in a common‐source configuration, can stabilize a hybrid distributed amplifier. This kind of feedback is useful when using high transconductance FETs. Finally, for a 0.3 × 200‐μm HEMT (NEC 321) in chip form, an unconditionally stable four‐section distributed amplifier is designed using the suggested feedback, without compromising the gain‐bandwidth product. © 1993 John Wiley & Sons, Inc.
An approximative analysis of the output power of a resonant tunneling diode oscillator
Authors: Nilsen Svein M. , Lundgren Lennart
Published: July 2007

A simplified theory for describing the maximum available output power versus oscillation frequency and calculated dc series resistance of resonant tunneling devices is presented. The method uses an approximation of the measured dc current versus voltage characteristic. Results can easily be used for comparisons of measured and calculated maximum output power for a particular device at different oscillation frequencies. © 1993 John Wiley & Sons, Inc.
Overcoming passive coupling excess loss in fiber‐optic networks by using a collective interface
Authors: Georgopoulos Voula C.
Published: July 2007

When using passive coupling in a single‐mode fiber‐optic network, all interfaces are not allowed to tap into the fiber because there will be a significant power loss at every tap, at least for current technology. In this Letter, a systolic array collective interface is presented which alleviates the above problem due to its inherent property of parallel processing. © 1993 John Wiley & Sons, Inc.
The effects of crossing interconnections on signal propagation on the GaAs‐based integrated circuits
Authors: Goel A. K. , Prabhakaran P. J.
Published: July 2007

We have analyzed the effects of embedded crossing interconnections on signal propagation in the top‐level driven interconnection on GaAs‐based integrated circuits. The algorithm has been used to study the dependences of the cross talk and propagation delays on the various crossing interconnection parameters. Results can be utilized for optimization of the high‐speed circuits. © 1993 John Wiley & Sons, Inc.
High‐power, low‐loss, broadband, spdt switch for VHF applications
Authors: Agarwal Arvind
Published: July 2007

This Letter discusses the design and development of high power, low‐loss SPDT switch using SPDT vacuum relays from dc to VHF range. One unit of SPDT switch was developed and subjected to 120.0‐KW peak power at 53 MHz with no trace of breakdown. © 1993 John Wiley & Sons, Inc.
The effect of dielectric truncation on the radiation of a microstrip ring antenna operated at higher‐order modes
Authors: Iyer S. M. Vaitheeswaran , Karekar R. N.
Published: July 2007

Surface wave effects on the radiation of microstrip ring antennas are studied theoretically using the full‐wave solution based on reflection matrices for a microstrip ring antenna when they are operated at higher‐order modes. The effects on the radiation due to changes in the radius of the truncated dielectric substrate, the thickness, and the permittivity are examined. A choice between TM11 at ϵr = 9.8 or TM12 at ϵr = 2.2 is suggested. © 1993 John Wiley & Sons, Inc.
On the design and analysis of ultrabroadband antenna windows
Authors: Prasad R. V. Hara , Lakshminarayana D.
Published: July 2007

The design, analysis, and the results obtained on two ultrabroad‐band antenna windows, operating over 2‐18 GHz, one in A‐sandwich and the other in C‐sandwich construction are presented. Curves are given for theoretical and practical power transmission coefficients. The maximum transmission loss measured in the A‐sandwich window is <1.5 dB and that of the C‐sandwich window is <1.5 dB over the complete band. © 1993 John Wiley & Sons, Inc.
Evolution of signals in long‐haul fiber links
Authors: Matera F. , Mecozzi A. , Romagnoli M. , Settembre M.
Published: July 2007

Propagation of nonsoliton and soliton signals in long‐haul fiber links is numerically investigated in the presence of chromatic dispersion, the Kerr effect, and noise of erbium amplifiers. Conditions for propagation of a nonsoliton signal with good system performances are found when an anomalous dispersion region is used. A comparison with systems based on such signals and soliton systems are also presented. © 1993 John Wiley & Sons, Inc.
A millimeter‐wave total power radiometer
Authors: Lyons B. N. , Vizard D. R. , Pike J. P. , Kelly W. M.
Published: July 2007

The design of a multichannel millimeter‐wave total power radiometer with frequent calibration is described. The radiometer has seven channels ranging in frequency from 20 to 183 GHz. The radiometer combines a quasioptical front end with subharmonic mixers and integrated calibration loads to yield a compact low‐cost radiometer package. Measured results are presented. © 1993 John Wiley & Sons, Inc.
The analysis of propagation characteristics in planar gyrotropic chirowaveguides
Authors: Wenyan Yin , Pao Li
Published: July 2007

We analyze the coupled‐mode propagation in planar gyrotropic chirowaveguides. At first, the transverse components of electric and magnetic fields in such waveguides are expressed in terms of the longitudinal components of Ē and H̄. Dispersion diagrams for the parallel metallic‐plate gyrotropic chirowaveguides are shown, and their novel features are pointed out. The effects of chirality admittances on the cutoff wavelengths of propagating modes in the grounded planar and parallel metallic‐plate gyrotropic chirowaveguides are taken into consideration. © 1993 John Wiley & Sons, Inc.
Performance evaluation of moment‐method codes on an intel iPSC/860 hypercube computer
Authors: Klimkowski Kenneth , Ling Hao
Published: July 2007

The performance of a moment‐method code on a parallel computer is analyzed and evaluated. Algorithmic complexity costs are discussed in terms of matrix size and a parameter of matrix partitioning, subblock size. The measured computational times of the matrix fill operation and LU solver are analyzed in terms of scaled efficiencies. © 1993 John Wiley & Sons, Inc.
A spectral‐domain‐eigenfunction method for radiation by a cavity‐backed planar structure
Authors: Ronghong Jin , Yuanheng Qiu
Published: July 2007

A planar structure backed with a cavity is analyzed by a spectral‐domain‐eigenfunction method. An appropriate basis function and an appropriate weighting function have been chosen, which greatly simplifies the process of the solution. Finally, the calculated radiation fields of the antenna are compared with the measured results. © 1993 John Wiley & Sons, Inc.
Eigenwaves in uniaxial chiral omega media
Authors: Tretyakov Sergei A. , Sochava Alexander A.
Published: July 2007

Eigenwaves in novel materials which have properties of chiral composites and omega structures are considered. The materials can be modeled by uniaxial bianisotropic constitutive relations. Both chiral and omega composites possess promising features, for and one may expect still more interesting effects in more general media. © 1993 John Wiley & Sons, Inc.
Input impedance of rectangular microstrip antennas for different feed sizes
Authors: Dan S. , Chauhan B. , Maggo G. , Bhattacharya A. , Thakur A. , Bhattacharjee A. K.
Published: July 2007

Closed‐form expressions for the input impedance of half‐wavelength rectangular microstrip antennas fed by coaxial connectors of different sizes at the center of one of the radiating edges and open circuited at one of the ends are derived. Good agreement between computed and measured data is obtained. © 1993 John Wiley & Sons, Inc.
Design analysis and fabrication of lumped‐distributed branch‐line couplers for coplanar waveguide mmics
Authors: Gillick M. , Robertson I. D. , Joshi J. S.
Published: July 2007

An analysis of lumped‐distributed coplanar waveguide (CPW) branch‐line couplers suitable for GaAs MMIC designs is presented. This investigation takes into account the degree of coupling, impedance transformation, and levels of miniaturization in order to provide a greater design flexibility for integration with uniplanar monolithic circuits. Synthesis techniques and design graphs are given for these couplers and a monolithic 50‐15‐OM version has been fabricated and tested. The coupler's measured results show an amplitude balance of 4.7 × 0.3 dB, input and output return losses of better than 12 and 15 dB, respectively, and an isolation of better than 20 dB over the range 14–16 GHz. This new method of designing miniaturized couplers demonstrates their suitability for balanced amplifiers, especially when they are incorporated into CPW MMICs. © 1993 John Wiley & Sons, Inc.
Measurement of the current‐density distribution in high‐temperature superconducting microstrip by means of kinetic‐inductance photoresponse (invited paper)
Authors: Newman Harvey S. , Culbertson James C.
Published: July 2007

We report a technique for measuring the spatial profile of microwave‐frequency currents in resonant thin‐film superconducting microstrip devices operated near resonance. We probe the patterned superconducting device as a function of position by scanning a modulated light beam across the region to be probed. With the light focused to a spot size much smaller than the microstrip width, we have measured the current density distribution as a function of position across the width of the strip. Using an elementary model for the superconducting current density distribution, we fit an effective penetration depth at the edge of the microstrip. © 1993 John Wiley & Sons, Inc.
Demonstration of A 3‐GHz‐bandwidth real‐time spectral‐analysis receiver based on a high‐Tc superconductive chirp filter (invited paper)
Authors: Lyons W. G. , Seaver M. M. , Arsenault D. R. , Boisvert R. R. , Sollner T. C. L. G.
Published: July 2007

A 3‐GHz‐bandwidth real‐time spectral‐analysis receiver has been demonstrated. The fully integrated compressive receiver is based on the chirp‐transform algorithm and uses a high‐Tc superconductive (HTS) tapped‐delay‐line chirp filter with a time‐bandwidth product of 40. The 3‐GHz bandwidth of the HTS chirp filter is unobtainable using other technologies such as surface acoustic waves. This prototype receiver, a combination of an HTS passive microwave component and conventional semiconductor circuits, demonstrates a microwave system that could not be built without the unique HTS component. © 1993 John Wiley & Sons, Inc.
Superconducting multiport antenna arrays (invited paper)
Authors: Chaloupka H.
Published: July 2007

Applications of HTS to radiating elements and beam‐forming networks of multibeam and/or multifrequency arrays are discussed. This includes radiating elements which meet special requirements with respect to size and frequency response. Realized versions of both a three‐port HTS array and a April × 4 Butler matrix are presented. © 1993 John Wiley & Sons, Inc.
Wide hts microbridge series array transmission line
Authors: Jackson Charles M. , Kobayashi June H. , Wire M. S. , Heflinger Lee O. , Lee Alfred , Pettiette‐Hall Claire , Hu Roger , Burch John F.
Published: July 2007

Experiments are performed on an HTS transmission line fabricated with a series array of Josephson junctions. We have determined the phase shift mechanism and have measured the magnitude of the phase shift of wide junctions. A qualitative model of the phase shift mechanism has been developed which explains the effects of applied magnetic fields. © 1993 John Wiley & Sons, Inc.
Double serial amplified recirculating delay line
Authors: Vizoso B. , Civera R. , López‐Amo M.
Published: July 2007

Theoretical results on a double serial amplified recirculating delay line are presented. Its application as filter is emphasized, showing a wide flexibility of design by appropriate choices of its main parameters: loop length, gain, and coupling ratio of the couplers. © 1993 John Wiley & Sons, Inc.
The scan performance of the fresnel‐zone plate antenna: A comparison with the parabolic reflector antenna
Authors: Baggen L. C. J. , Jeronimus C. J. J. , Herben M. H. A. J.
Published: July 2007

Using Kirchhoffs diffraction theory, scalar field analyses of two off‐axis focused antenna systems, the Fresnel‐zone plate antenna (FZPA) and parabolic reflector antenna, are presented. Expressions which describe the gain patterns of both antennas are derived and used to examine the scan properties of the two systems and to reveal and discuss similarities and differences between them. The results of the analysis give good insight into future applications of the FZPA as a multibeam antenna. © 1993 John Wiley & Sons, Inc.
Optical‐fiber multiple PPM frame synchronization
Authors: Elmirghani Jaafar M. H. , Cryan Robert A. , Clayton F. M.
Published: July 2007

At high data rates and gigabit schemes, orthogonal optical‐fiber pulse position modulation (PPM) prematurely exhausts the available pulse width resources. Multiple PPM (MPPM) offers improved throughput while preserving the PPM sensitivity attraction. The multiple pulse positions per pulse width place a high demand on the synchronization subsystem. We propose MPPM for the optical fiber channel, then investigate the synchronization requirements at the chip, symbol, and frame rates. An original spectral characterization is presented for the format, illustrating that symbol and chip synchronization are achievable from the data stream. Frame synchronization is examined and a novel technique based on natural sequences is proposed and demonstrated, resulting in the extraction of both the frame frequency and the frame phase. Data pattern dependency is eliminated through an original technique, and a practical implementation is given. Practical results are presented for the synchronizers and shown to correlate with the developed models. © 1993 John Wiley & Sons, Inc.
New design techniques for high‐order narrow‐band microwave filters derived from low‐frequency recursive concepts
Authors: Billonnet L. , Jarry B. , Guillon P.
Published: July 2007

We show how high‐order narrow‐band microwave filters can be built with the help of various unitary first‐order recursive cells in strict accordance to low‐frequency principles. We illustrate our approach with the simulated results for a third‐order filter in the 2.25–8.4‐GHz frequency range. © 1993 John Wiley & Sons, Inc.
Effects of initial chirp of control pulse on soliton‐dragging logic gates
Authors: Tang Xiongyan , Ye Peida
Published: July 2007

The effects of the initial chirp of the control soliton pulse on the time shift of the soliton‐dragging logic gate (SDLG) is investigated numerically in this article. We find that the positive initial chirp increases the time shift and the negative initial chirp decreases the time shift. The physical interpretation for this phenomenon is presented. © 1993 John Wiley & Sons, Inc.
An S‐shaped optical fiber loop resonator using a 3 × 3 nonplanar fiber coupler
Authors: Ja Y. H. , Dai X.
Published: July 2007

The first demonstration of a new S‐shaped single‐mode fiber loop resonator is presented. The S‐shaped fiber loop resonator is made with a nonplanar 3 × 3 fiber directional coupler and two fiber delay lines. Expressions for the circulating (resonant) fields and the transmitted and reflected output fields are derived. Theoretical and experimental results show that this fiber loop resonator may have potential applications as a spectral filter and a closely spaced two‐channel wavelength division multi/demultiplexer.
Monolithic Ka‐band coplanar waveguide amplifier design in MMIC
Authors: Bayar Esen , Robertson Ian D. , Aghvami A. Hamid
Published: July 2007

In this article an effective design approach which realizes high‐frequency MMIC networks in grounded coplanar waveguide (CPWG) transmission media is demonstrated. Topological features which effect electrical characteristics are highlighted and a layout topology which minimizes secondary circuit parameters is illustrated. A method is described which enables these features to be implemented while minimizing discontinuity effects, and a practical application is demonstrated with a 23‐GHz CPWG amplifier design.
Image reconstruction for computer tomography with missing projections using the bimodal optical computer
Authors: Habli M. A. , Leonik K.
Published: July 2007

Image reconstruction for computer tomography with missing projections using the bimodal optical computer (BOC) is studied. The computer simulation results are reported. Two real‐time processing algorithms for image enhancement are used.
Low cost L‐band mobile terminal antennas for helicopters
Authors: Wu Te‐Kao
Published: July 2007

The feasibility of using a low‐gain antenna (LGA) as a mobile terminal antenna for helicopers is described in this article. The objectives are (a) to select the lowest cost antenna system which can be easily mounted on a helicopter and capable of communicating with a satellite, and (b) to determine the best antenna position on the helicopter to mitigate the signal blockage due to rotor blades and the multipath effect from the ehlicopter's body. The omnidirectional low gain antenna (LGA) is selected because it is simple, reliable, and low cost. The helix antenna is selected among the many LGAs because it is the most economical and has the widest elevation beam‐width. Both two‐ and four‐arm helices are studied experimentally to determine the antenna's performance and the scattering effects from the helicopter's body. It is found that the LGA should be located near the tail section and at least 8 in. above the helicopter.
Resonance in a spherical annular‐ring microstrip structure
Authors: Wong Kin‐Lu , Chen Horng‐Dean
Published: July 2007

The resonance problem of a spherical annular‐ring microstrip structure is investigated rigorously by using a Green's function formulation in the spectral domain. Numerical results of the complex resonant frequencies are obtained by using Galerkin's moment method. The convergence of the numerical calculation using different numbers of basis functions is also discussed. Typical numerical results of the resonant frequency and the quality factor, obtained from the real and imaginary parts of complex resonant frequency, for the microstrip structure used as a resonator element at TM11 mode and as an efficient radiator at TM12 mode are presented. Effects of the curvature on the resonant frequency and the quality factor of the structure are also analyzed and discussed.
Integrated active slot dipole antenna amplifier
Authors: Wu Xiao‐Dong , Chang Kai
Published: July 2007

This article presents the design and performance of a slop dipole antenna integrated directly with an FET amplifier. The measured radiation patterns of the antenna are linear with cross‐polarization levels of 11 dB down in E plane and 17.5 dB down in H plane. The measured gain of the antenna is 10 dB at 7.1 GHz. Compared with a passive antenna, the active antenna has an extra gain of 7 dB.
Single and double square‐loop frequency‐selective surfaces with thick metallization
Authors: Webb David B. , Michielssen Eric , Mittra Raj
Published: July 2007

Single and double square‐loop frequency‐selective surfaces (FSSs) are investigated to determine the effects of metallization thickness on the scattering characteristics. Results presented are computed via a spatial‐domain method of moments technique using triangular patch basis functions. To isolate the effects of metallization thickness, freestanding screens of infinite extent are considered.
Conformal absorbing boundary conditions for the vector wave equation
Authors: Chatterjee A. , Volakis J. L.
Published: July 2007

An absorbing boundary condition of second order is derived for mesh terminations conformal to the shape of the radiator or scatterer. The boundary condition is expressed entirely in terms of the principal curvatures of the termination surface and results in a symmetric system of equations when incorporated into the finite‐element functional.
New types of TEM cells with shaped inner and outer conductors
Authors: Costamagna Eugenio , Fanni Alessandra
Published: July 2007

Numerical algorithms are utilized to design nontraditional transversal sections of TEM cells, leading to large areas of almost uniform electric field within small dimensions. Numerical inversion of the Schwarz‐Christoffel formula and predictor‐corrector mapping of equipotential lines are, utilized. © 1994 John Wiley & Sons, Inc.
Analytic solutions for the finite‐difference time‐domain and transmission‐line‐matrix methods
Authors: Chen Zhizhang , Silvester Peter P.
Published: July 2007

Eigenmodal decomposition formulations are given for numerical solutions of the finite‐difference time‐domain (FDTD) and the transmission‐line‐matrix (TLM) methods. Instead of direct simulation with these time‐recursive schemes, the analysis involves two steps: (1) solving an eigenvalue problem, and (2) analytically constructing the numerical solutions in terms of the eigenvalues and eigenvectors. The numerical solution at any time step can be obtained with only O(N) computation once the corresponding eigenvalue problem has been solved. The main advantage of this technique is that the eigenvalues and eigenvectors for a problem can be stored, the numerical solutions then quickly processed with the stored data. In addition, high‐frequency numerical noise can be reduced simply by discarding the related high‐frequency modes. © 1994 John Wiley & Sons, Inc.
Time‐domain modeling of the impedance boundary condition for an oblique incident parallel‐polarization plane wave
Authors: Wang Bing‐Zhong , Xiao Qun
Published: July 2007

In this article, the time‐domain impedance boundary condition (TDIBC) used for a thin layer coating over perfect conductors is obtained for the case of an oblique incident parallel‐polarization plane wave. Discretization of the TDIBC to efficiently handle the thin‐layer coating is presented in the context of the time‐domain finite‐difference (TDFD) technique. The TDFD solutions using our TDIBC are in good agreement with the analytical results. © 1994 John Wiley & Sons, Inc.