The construction and comprehensive electromagnetic analysis of a novel class of WLAN layouts is presented in this paper. The main purpose is to construct a wireless system according to the 802.11 a/b/g standards, which enables significantly larger and more reliable data transfer rates, making use of a new largescale field prediction technique, based on the parabolic equation with finite differences. Thus, four distinct structures, based on two different operating systems and two different hardware architectures, are proposed and elaborately examined. On the other hand, for the prediction algorithm a 3D wide-angle parabolic equation scheme is devised and a recursive approximation of the forward wave equation is accomplished. Unlike existing methods that characterize obstacles by means of surface impedance boundary conditions, a more rigorous approach, by treating them as penetrable objects with known material features is utilized. In this manner, the "interface" problem is systematically formulated and high levels of accuracy are attained. Moreover, the proposed technique is proven to be sufficiently faster and numerically more efficient, as the lattice, so constructed, along with the numbering of degrees of freedom remain unchanged from a parabolic equation plane to another. Extensive results and measurements certify the aforementioned merits for various realistic exterior and interior configurations.

This paper presents the design of a tri-mode matched feed horn to remove the beam squinting effects in a circularly polarized offset parabolic reflector antenna. In a conical horn, three modes i.e., TE₁₁, TM₁₁ and TE₂₁ are combined in proper amplitude and phase proportion to obtain a tri-mode matched feed configuration. The proposed tri-mode horn is then used as a primary feed device to illuminate the circularly polarized offset parabolic reflector antenna. The simulated data on radiation characteristics of the offset reflector are used to estimate the magnitude of beam squinting and the results are compared with that of a conventional potter horn fed offset reflector. The experimental results on secondary radiation pattern are also incorporated in the paper.

This paper presents a novel compact "via-less" UWB filter derived from a quarter-wavelength short-circuited stubs model. In this compact "via-less" UWB filter, there is no connecting vias as short circuit elements. Unlike its previous model that has 5 short-circuited stubs, this novel shape consists of two pairs of stubs which are joint together to share on the same microstrip patch and thus reduces total size of the UWB filter itself making it more compact in nature. With proper width optimization, the microstrip patch is able to decouple and provides low impedance to the ground in the UWB frequencies range. The filter delivers 3.85 GHz to 10.44 GHz frequency range with 92.23% of fractional bandwidth. The magnitude of insertion loss is below than 0.53 dB and the return loss is lower than -14.8 dB in the passband frequencies. The -3 dB bandwidth is from 3.85 GHz to 10.44 GHz with 92.23% of fractional bandwidth. The group delay only varied by 0.47 ns in the passband, which makes it suitable for radio communication systems.

An objective of the present study is to make a physical insight into the radiation properties of an L-shaped wire antenna. More specifically, the study is focused on the effects of the antenna geometry over the characteristic radiation pattern of an L-shaped wire antenna. Regarding the basic equations for the radiated field, three main regions according to the length-height ratio of an L-shaped wire antenna have been determined. The said regions depict the geometrical boundaries where the L-shaped wire antenna loses its characteristic monopoletype radiation pattern. In this sense and relating to the aspect ratio of the L-shaped antenna, the said radiation properties can be easily varied in order to achieve a half isotropic radiation pattern or even, a patch-type radiation pattern. Thus, the method described herein demonstrates that simple modifications applied to the geometry of a basic structure, allow obtaining radiation properties associated to more complex structures.

In recent years, RFID solutions are finding an increasing number of applications in a wide variety of industries. There are some natural limitations when applying RFID technology in the steel industry, because the tags do not function well in metallic environments. Even though some commercial RFID metal tags are available in the market, they are found to be too expensive by steel companies. This paper proposes a useful and practical RFID tag design for management applications involving steel-bar and wirerod products manufactured by the steel industry. The dual-function metallic RFID tag, comprising of both an RFID code and a barcode, involves technology advancement in RFID design, and named Window-Tag (WinTag). The maximum read range of this tag can reach about 5.7m for the radiated power of 4.0W EIRP in free space. In the practical application, the maximum read ranges are about 2.3m and 5.0m for the worst and best case, respectively. The design methodology as well as simulation and measurement results of the WinTag are presented in this paper. The low profile and low cost features of the WinTag makes the RFID tag well suited for metallic type tag of labeling system that requires integration of RFID technology.

This study introduces the notion of 2-D and 3-D Phase Projection in our search for a simple and elegant solution to further reduce noise during InSAR post-processing steps with multiple baselines. Projection is a powerful tool to reduce noise in a system of more than two satellites. It does so by noting that the geometry of the satellite configuration restricts the range of values over which the wrapped phases can assume. Projection in general reduces noise in the system by utilizing the information provided by the configuration of the satellites to reduce the set of allowed phase points, thereby improving the robustness of the system in the presence of noise. Our results show that, for most cases, whether with the extremely small baseline distance or non-integer baseline ratios, using 3-D Projection gives better height inversion results.

This paper presents an efficient approach for analyzing the longtime response of high-speed dispersive and lossy interconnects terminated with nonlinear loads. In this approach, a fast real-time convolution algorithm with computational cost st O(N log²N) is suggested to tackle the long-time analysis of the high-speed dispersive and lossy interconnects, which are modeled by S-parameters. In addition, the acquirement of the S-parameters is recommended to adopt wideband closed-form formulas. The time response of a microstrip line with a nonlinear load is shown as a practical example. The dominant parameters affecting the response of this microstrip line is observed and discussed in detail. The approach demonstrates its efficiency and accuracy in the analysis.

A novel electric small conical antenna working on a very broad band, 0.47-6 GHz, with the height of only 60 mm, is presented. A capacitive ring on the top of the cone and three oblique shorted lines are used to expanding the work band. By changing the width of the ring and the slope of the oblique line, the impedance of the antenna can be matched to 50-ohm feed line commendably. Simulations and experiments results demonstrate that this antenna provides very broadband and low-profile characters, which exhibits a 12.8:1 impedance bandwidth with voltage standing wave ratio (VSWR) below 2:1 (the impedance bandwidth is 11.9:1 with the VSWR below 1.5:1) and with the height only 0.094 wavelength associated to the lowest frequency.

The effect of soil properties on landmines detection using Microstrip antenna with corrugated ground between the two microstrip elements as a sensor has been investigated. The effect of the electrical properties of the soil as well as the shape of the soil surface on the detection capability of the sensor is studied. The Finite-Difference Time-Domain (FDTD) has been used to simulate the sensor for landmines detection.

The present study was conducted to evaluate the information leakage of the display image that can be reconstructed using the electromagnetic interference emitted from a computer. A reconstructed image was generated from the information signal that correlated with the switching of the RGB signals of the computer display. Based on this observation, a measurement method and system for the information signal was developed by displaying an image with vertical stripes. To check the validity of this measurement method and system, test measurements were carried out. The test result revealed that the information signal can be detected in the electromagnetic interference. In addition, the information signal was found to be contained in high volume between 300 and 600 MHz, depending on the receiving frequency band.

A model of the ring waveguide of a fixed cross-section and variable distribution of the surface impedance of waveguide's wall has been considered. For a class of circular hodographs of surface impedance the analytical solution of the corresponding boundary-value problem has been obtained. This solution has been used for simulating a 'cycle slipping' phenomenon, known from the observations of VLF signals propagating over long paths in the earth-ionosphere waveguide, with the goal of clarifying the cause for its initiation. Numerical experiments have shown that this phenomenon, in the context of the model in question, is a consequence of the interconversion of two dominant waveguide modes in circumstances where their propagation constants are close.

This paper develops a novel design method for synthesizing the multi-passband filter with high flexibility in various passband location and fractional bandwidth. Using the proposed compensation technology in the equivalent circuit of multi-passband resonator, the cutoff frequencies and matching property in passband regions can be improved. Triple- and quad-band bandpass filters operating in both wireless local area network (WLAN) 802.11 a/b/g and worldwide interoperability for microwave access (WiMAX) systems are presented to verify the design method. The lumped-element coplanar waveguide stub fabricated by the split-ring resonator is established to realize filter with compact size. All the measured, full-wave simulated and equivalent-circuit modeled results illustrate a good agreement among them, which validates the multi-passband design methodology and shows the advantages of DC elimination and deep rejection between each passband.

In this paper, we first review the Phase Extracted (PE) basis functions by recalling the derivation which shows that the induced current on a PEC surface has the propagating phase factor the same as the incident wave in a scattering problem. The wide band characteristic of this PE basis functions has been investigated by demonstrating that very wide band radar response from PEC objects can be simulated accurately by using PE bases, only based on a single coarse mesh grid. Besides, the resulted current coefficients are shown to vary slowly and smoothly with frequency changing and can be interpolated and extrapolated in very wide band easily. The piecewise cubic Hermite interpolation/extrapolation method with respect to the current coefficients is used to obtain the coefficients in the frequency band of interest. Numerical examples demonstrate very good accuracy and high efficiency in wide band radar response prediction in terms of the amplitude of the scattering field as well as its phase distribution.

This paper presents a general method for studying the mechanical properties of a ferrofluid seal by using a three-dimensional analytical approach based on the coulombian model of a magnet. The fundamental Maxwell's equations lead us to define the concept of magnetic energy of the ferrofluid seal by using only the threedimensional equations of the magnetic field created by ring permanent magnets radially magnetized. Our study corresponds to the specific case when the ferrofluid is submitted to a very high magnetic field. Under these conditions, we assume that the mechanical properties of the ferrofluid depend only on the magnetic field created by the permanent magnets. Throughout this paper, the remanence polarization J of the magnets used is higher than 1T. The magnetic field we use in order to align the magnetic particles is very intense, greater than 400 kA/m. Consequently, the magnetic particles are assumed to be saturated and the magnetic field they create can be omitted. In this paper, a cylindrical structure consisting of two outer ring permanent magnets radially magnetized and an inner nonmagnetic cylinder is considered. In addition, a ferrofluid seal is placed between them. The calculation of the magnetic pressure of the ferrofluid seal has been analytically established in three dimensions in order to determine its shape. Moreover, the geometrical evolution of the ferrofluid seal shape is presented when the inner non-magnetic cylinder crushes the ferrofluid seal. The radial stiffness of the ferrofluid seal is determined in three dimensions when the inner cylinder is decentered. Furthermore, a way of obtaining the ferrofluid seal static capacity is discussed.

A simple approach for evaluation of the reciprocity of materials using raw scattering parameter measurements is proposed. This approach not only reduces the overall measurement time but also eliminates the need for calibrating the measurement system since it uses calibration-independent measurements. We have derived a metric function for reflecting and nonreflecting cells, which are used to house the sample under test. This function does not depend on electrical properties of materials and their lengths, and whether the cell is reflecting. We have also investigated the effects of the sample length and air pockets between sample external surfaces and cell inner walls on the performance of the evaluation of sample reciprocity.

A compact composite ultra wide-band elliptic-function low-pass filter is introduced by combining in cascade a microstrip stepped-impedance resonator using interdigital capacitor and an admittance inverter. A triple cascade low-pass filter is designed, analyzed and tested with this technique accompanied by its equivalent circuit model. This composition acts similar to composite filter with desire attenuation and matching properties in order to obtain wide bandwidth and broad stop-band. The proposed low-pass filter features the sharpness of cut off frequency, low insertion-loss, enhancement of bandwidth up to X-band frequencies and very compact size.

The transmission characteristics of a high frequency circulator using coplanar wave guide have been designed and studied. To miniaturize the device, we have dramatically reduced the thickness of the YIG ferrite layer (Yttrium Iron Garnet). The circulator has an hexagonal shape with dimensions of 10*10 mm², the width of the central line (LINE) is 400 ?m, the space between LINE-to-GND is 130 ?m and the thickness of ferrite film (YIG) is 10 ?m. this compact circulator operates at 10 GHz. The insertion loss is 3.14 dB, the return loss is 18.57 dB and the isolation is greater than 20 dB.

In this paper, a novel algorithm for computing Physical Optics (PO) integrals is introduced. In this method, the integration problem is converted to an inverse problem by Levin's integration algorithm. Furthermore, the singularities, that are possible to occur in the applications of Levin's method, are handled by employing trapezoidal rule together with Levin's method. Finally, the computational accuracy of this new method is checked for some radar cross section (RCS) estimation problems performed on flat, singly-curved and doubly-curved PEC plates which are modeled by 8-noded isoparametric quadrilaterals. The results are compared with those obtained by analytical and brute force integration.

A promising microwave method has been proposed to accurately determine the complex permittivity of thin materials. The method uses amplitude-only scattering parameter measurements at one frequency for this purpose. It resolves the problems arising from any offset of the sample inside its cell in complex reflection scattering parameter measurements and from any uncertainty in sample thickness in transmission scattering parameter measurements. The method determines unique permittivity since, for thin samples, multi-valued trigonometric terms can be linearized. It uses higher order approximations to extract highly accurate permittivity values. It works very well in limited frequency-band applications or for dispersive materials since it is based upon point-bypoint or (frequency-by-frequency) measurements. For validation of the method, we measured the complex permittivity of two thin polytetrafluoro-ethylene (PTFE) samples.

Deterministic propagation models are typically validated by performing comparisons between real and simulated E-field envelope distributions. These distributions correspond to straight spatial segments and, occasionally, also surfaces. This approach is correct to study large scale fading for relatively large distances. However, in a real environment and shorter distances, there are too many details to consider. As a result, it is almost impossible to reach a point by point match in a minimally realistic experiment. There are two ways to deal with this problem. The first one is to model every minor detail everywhere around us, keeping the point by point metric. The second one is to change that metric in order to admit, at least in part, that we can not take into account of all the details. If uncertainty can not be eliminated, we should learn to take advantage of it by using a statistical metric like the one proposed here. This paper uses such a kind of metric to validate several structural and geometrical simplifications of a model for the transition between outdoor and indoor propagation that has been recently published. Furthermore, we demonstrate that this metric has helped us to improve and understand better this model, while revealing unexpected model properties at the same time.