Analytical equations for compact dual frequency microstrip antenna

Design equations are presented for calculating the resonance frequencies for a compact dual frequency arrow‐shaped microstrip antenna. This provides a fast and simple way to predict the resonant frequencies of the antenna. The antenna is also analyzed using the IE3D simulation package. The theoretical predictions are found to be very close to the IE3D results and thus establish the validity of the design formulae. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 477–482, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10048     

Burrows–Wheeler compression with variable length integer codes

The final coder in Burrows–Wheeler compression is usually either an adaptive Huffman coder (for speed) or a complex of arithmetic coders for better compression. This article describes the use of conventional pre‐defined variable length codes or universal codes and shows that they too can give excellent compression. The paper also describes a ‘sticky Move‐to‐Front’ modification which gives a useful improvement in compression for most files. Copyright © 2002 John Wiley & Sons, Ltd.     

Analysis of line to line coupled coplanar waveguides with W‐shaped conductor backing using conformal mapping method

A W‐shaped microshield coupled parallel coplanar waveguide (CP CPW), which is a new type of CP CPW, is proposed. Closed‐form expressions are presented for calculating the quasistatic parameters of this coupled structure by using conformal mapping techniques. The effect of the W‐shaped conductor backing on the coupling between CPWs is also discussed. Comparisons are made between the present numerical results and the results available in the microwave literature for CPW V‐shaped microshield coupled lines (CWVMCLs) and CP CPWs with a flat conductor backing. In addition, the coupling coefficient of the coupled CPWs is shown to be significantly lower than that of the CWVMCLs in the literature. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 354–359, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce10035     

Deadlock detection in MPI programs

The Message‐Passing Interface (MPI) is commonly used to write parallel programs for distributed memory parallel computers. MPI‐CHECK is a tool developed to aid in the debugging of MPI programs that are written in free or fixed format Fortran 90 and Fortran 77. This paper presents the methods used in MPI‐CHECK 2.0 to detect many situations where actual and potential deadlocks occur when using blocking and non‐blocking point‐to‐point routines as well as when using collective routines. Copyright © 2002 John Wiley & Sons, Ltd.     

Coplanar waveguide gyroelectric circulator

A three‐port coplanar waveguide semiconductor circulator is analyzed. A theoretical 60‐GHz N‐type indium antimonide design at an operating temperature of 77 K is presented with a 20‐dB isolation bandwidth of approximately 25%. A six‐port microstrip ferrite circulator is also designed to provide a validity check using the ANSOFT^TM High Frequency Structure Simulator. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 367–374, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce10036     

Output regulation of general discrete‐time linear systems with saturation nonlinearities

This paper studies the classical problem of output regulation for linear discrete‐time systems subject to actuator saturation and extends the recent results on continuous‐time systems to discrete‐time systems. The asymptotically regulatable region, the set of all initial conditions of the plant and the exosystem for which the asymptotic output regulation is possible, is characterized in terms of the null controllable region of the anti‐stable subsystem of the plant. Feedback laws are constructed that achieve regulation on the asymptotically regulatable region. Copyright © 2002 John Wiley & Sons, Ltd.     

Experimental testing of a discrete‐time sliding mode controller for trajectory tracking of a wheeled mobile robot in the presence of skidding effects

This article addresses the trajectory tracking problem for a wheeled mobile base, considering the presence of disturbances that violate the nonholonomic constraint, and using an approximated discrete‐time model for the vehicle. The proposed solution is based on discrete‐time sliding mode control, in order to ensure that the controller is both robust and implementable. The asymptotic boundedness of the discrete‐time tracking errors is theoretically proved, and experimental results are reported, showing the effectiveness of the proposed control law. © 2002 Wiley Periodicals, Inc.     

Continuously varying coupled transmission lines applied to design band‐pass filters

This article presents a technique to analyze and optimize Continuously Varying Transmission Lines (CVTL's), used to design microwave band‐pass filters in planar technology. For millimeters waves, radiation losses can increase quickly, especially for sharp discontinuities in planar circuits. In this approach, rather than taking account of this effect in a full‐wave analysis, we generate structures without discontinuities. Moreover, the line shape is optimized to reduce spurious responses out of the band‐pass. For several filters, measurements are compared with simulation results. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 288–295, 2002.     

High‐quality texture reconstruction from multiple views

This paper presents a method to automatically calculate texture maps for a given three‐dimensional object out of a sequence of images. It is used in our image‐based modeling approach after the registration of the images and the geometric modeling is done. We show that the presented method uses the information from all images by implicitly applying a weighting function. Using this approach the consideration of modeled occlusions as well as the detection and removal of non‐modeled occlusions is accomplished. The final resolution of the texture maps can be adjusted on a pixel/cm basis. Copyright © 2002 John Wiley & Sons, Ltd.     

Automatic form generation

The Acuity project, in support of a collaborative brain‐tumor research effort, provides WWW‐based input forms implemented as Java applets for updating a WWW‐accessible database. The continuing need to develop new, but closely related, input forms motivated the design and implementation of the Acuity Form Generator (AFG), an automatic form‐generation tool. This paper documents the AFG technology. Copyright © 2002 John Wiley & Sons, Ltd.     

An object‐oriented interface for the dynamic memory management of sparse discrete mathematical operators in numerical scientific applications

This paper describes an object‐oriented interface for the memory management of sparse discrete mathematical operators in numerical scientific applications. The basic data structure we propose is intended to implement and cope with mathematical vectors in sparse format. This structure allows an effective implementation of more complex data structures, such as matrix and matrix‐like objects, to represent the discrete version of differential operators in numerical application codes. A research example concerning adaptive wavelet algorithms illustrates the possible applications.Copyright © 2002 John Wiley & Sons, Ltd.     

Frequency dependence on image reconstruction for a buried imperfectly conducting cylinder

Frequency dependence on image reconstruction for a buried imperfectly conducting cylinder is investigated. A conducting cylinder of unknown shape and conductivity is buried in one half‐space and the incident wave is scattered from another half‐space. By using measured scattered field, the image problem is reformulated into an optimization problem and solved by the genetic algorithm. Frequency dependence on image reconstruction is investigated and numerical results show that the reconstruction is well in the resonant frequency range. On the contrary, if the frequency is too high or too low, then the reconstruction becomes bad. This work provides both comparative and quantitative information. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 144–147, 2002.     

Non‐diagonal controllers in MIMO quantitative feedback design

This paper discusses multivariable quantitative feedback design through the use of controllers with off‐diagonal elements. Controller design for multivariable plants with significant uncertainty is simpler and potentially less conservative if some sort of dominance is achieved (by reducing the interaction effect of off‐diagonal plant elements) before a diagonal (decentralized) controller design is attempted. Traditional approaches for achieving dominance are not applicable when plant uncertainty must be considered. This paper discusses parallel and series implementations and for the latter, a pseudo‐Gauss elimination approach to the design has been developed. The interaction is measured using the Perron–Frobenius root of an interaction matrix. In some applications, it is possible to trade off individual plant cases against each other in order to reduce to the worst‐case interaction over the entire plant set. Copyright © 2002 John Wiley & Sons, Ltd.     

Recent advances in microwave active filter design. Part 1: Low‐frequency techniques and noise optimization

This two‐part article presents a representative sample of recent advances in microwave active filter design. In part one, we discuss design techniques based on both analog and digital low‐frequency methods that have been adapted to microwaves. From circuits with analog origins, we present simulated results, with some experimental verification, for a frequency‐dependent negative resistance (FDNR) and active‐inductance MMIC bandpass filters. From circuits with digital origins, we present experimental results for recursive filters, including MMIC bandpass and bandstop structures as well as higher‐order cascaded sections. Part one concludes with a discussion of the noise‐wave formalism and experimental results for active‐recursive and tunable ring‐resonator filters with minimum noise figure. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 159–176, 2002.     

Characteristic analysis of reverse‐L‐shaped microstrip‐fed large‐bandwidth printed slot antenna

The characteristics of a reverse‐L‐shaped microstrip‐fed structure is analyzed using the finite difference time domain method, and the characteristics of the proposed antenna are compared with a conventional antenna. The return loss, radiation resistance, and voltage–standing wave ratio in the frequency domain are calculated by Fourier transforming the time domain results. When the proposed feed structure is used, the bandwidth is extended in proportion to the slot width and the radiation resistance has the low value. When the slot width is 16 mm, the experimental bandwidth is approximately 50% (?10 dB ≥ S₁₁) at the center frequency of 2.3 GHz. In addition, the experimental data for the impedance and radiation pattern of the antenna are described. They are in good agreement with the calculated results. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 496–502, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10055     

Taming access control security: extending capabilities using the views relationship

The ‘views’ relationship indicates how an object‐oriented design can be clearly separated into objects and their corresponding interface. This paper uses the concept of ‘views’ in order to achieve full separation between the application and the security policy in the design and implementation. The result is achieved by providing a model for capabilities using ‘views’ that is richer than the traditional capability model. In addition, a distributed access control model is shown to be effective through the use of Secure Object Communication Channels (SOCCs) to allow for secure connections at the abstract object level. This security is applicable in the e‐commerce application domain, bringing security directly to the application abstraction level. Copyright © 2002 John Wiley & Sons, Ltd.     

Comparison of distributed and lumped element models for analysis of filtering properties of nonlinear transmission lines

The filtering properties of periodic loaded lossy transmission lines are studied from the point of view of microwave network theory. Under the condition that the per‐section capacitance of the line is small compared to that of the loading capacitors, it is shown that the distributed circuit can be described accurately by means of a lumped element ladder network. The effects of transmission line losses on this approximation are also analyzed. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 503–507, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10050     

Efficient method for heterojunction bipolar transistor model parameter extraction based on correlation between extrinsic and intrinsic elements

A simple and efficient way of extracting the small‐signal model parameters of the heterojunction bipolar transistor (HBT) is proposed. This novel approach provides a new insight into the strong correlation between the extrinsic and intrinsic HBT model parameters and raises the optimization efficiency by drastically reducing the search space. For the first time in HBT modeling, an explicit equation on the total extrinsic elements is derived, which results in a reduction of the number of optimization variables. The simulation results are presented and it is shown that this new method can yield a good fit between measured and simulated S parameters. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 311–319, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10001     

Fault estimation—a standard problem approach

This paper presents a range of optimization based approaches to fault diagnosis. A variety of fault diagnosis problems are reformulated in the so‐called standard problem set‐up introduced in the literature on robust control. Once the standard problem formulations are given, the fault diagnosis problems can be solved by standard optimization techniques. The proposed methods include (1) fault diagnosis (fault estimation, (FE)) for systems with model uncertainties; FE for systems with parametric faults, and FE for a class of nonlinear systems. Copyright © 2002 John Wiley & Sons, Ltd.