This paper proposes a numerical model of soil ionization phenomena that can occur when earth electrodes are injected by high pulse transient currents, as the current associated with a direct lightning stroke. Based on finite difference time domain numerical scheme, this model ascribes the electrical breakdown in the soil to the process of discharge in the air. In fact, as soon as the local electric field overcomes the electrical strength, the air in the voids trapped among soil particles is ionized, and the current is conducted by ionized plasma paths locally grow. The dimension of these ionized air channels are strictly dependent upon the local temperature. Thus, a local heat balance is enforced in order to obtain the time variable conductivity profile of the medium. This model can be implemented both for concentrated and extended electrodes, since no hypothesis has to be enforced about the geometric shape of the ionized region. Validation of the proposed model is obtained by comparing simulation results with experimental data found in technical literature.

A through-wall imaging problem is tackled by means a linear inverse scattering approach described and numerically analyzed in previous works by the same authors. Here, such an approach is checked for against experimental data. To this end, a CW-SF ultrawideband radar system is used to take measurements in a controlled environment as well as for in situ experiments. Different types of scatterers and of obscuring walls are considered.

In this paper, we present a demodulation structure suitable for a reader receiver in a passive Radio Frequency IDentification (RFID) environment. In a passive RFID configuration, undesirable DC-offset phenomenon may appear in the baseband of the reader receiver. As a result, this DC-offset phenomenon can severely degrade the performance of the extraction of valid information from a received signal in the reader receiver. To mitigate the DC-offset phenomenon, we propose a demodulation structure to reconstruct a corrupted signal with the DC-offset phenomenon, by extracting useful transition information from the corrupted signal. It is shown that the proposed method can successfully detect valid data from a received signal, even when the received baseband signal is distorted with the DC-offset phenomenon.

The electromagnetic field produced by a horizontal electric dipole over a double negative (DNG) medium half space is discussed, and the analytical expressions of the field which are convenient for calculation are derived. It can be concluded that the dipole on the configuration composed of the double positive (DPS) medium and the DNG medium half space can effectively excite the surface wave. The propagation wave number of the surface wave is less than that in both of the mediums, so that this kind of surface wave is a slow wave. Considered both the mediums are lossless, the amplitude of the surface wave decreases with the radial distance as ρ^{1/2. The total field shows complicated interference because of the superposition of three kinds of wave modes.}

The relationship of permittivity tensor of anisotropic medium in principal coordinate system and laboratory coordinate system is given. The characteristic of permittivity tensor of uniaxial anisotropic medium in the laboratory coordinate system is discussed. The transverse permittivity of an anisotropic plate are reconstructed in laboratory coordinate system based on the resonance and polarization characteristics of back scattering radar cross section (RCS) in wide band. Then, a new scheme of reconstructing the principal axis direction for a uniaxial sample plate is proposed, subject to the principal axis is unknown. The back scattering characteristics of a sample plate are discussed when the electromagnetic (EM) wave of different polarization is incident perpendicularity to the sample plate. Three sample plates, which are cut perpendicularly to the x', y', and z' axis in the laboratory coordinate system, are required. A numerical reconstruction example is given to demonstrate the availability of presented scheme.

A microstrip-fed planar monopole antenna consisting of an inverted-L monopole and a square parasitic element extending from ground plane directly to obtain wideband operation covering Bluetooth/ISM, 2.5 GHz WiMAX, 3.5 GHz WiMAX and 5.2/5.8 GHz WLAN bands is presented. The proposed antenna employs a shorted parasitic element to improve the bandwidth. The return loss of the suggested antenna geometry was calculated by a commercial HFSS 9 simulator and the results are compared with measured return loss, which shows a good agreement between them. Details of the proposed antenna designs and experimental results of the constructed prototypes are presented.

In this paper we will explain thoroughly a 802.11a pulse-swallow integer-N frequency synthesizer. The whole circuit is designed on chip except the loop filter. The reference frequency is set to 10 MHz and a pulse-swallow counter is designed for the purpose of controlling the dual-modulus divider (÷8/9). The frequency tuning range varies from 4.98 GHz to 5.73 GHz meanwhile the output power of the voltage-controlled oscillator is -13.5 dBm, and the phase noise measured at 1MHz is -126 dBc/Hz. The settling time of the closed loop is about 20 us, the total power dissipation is 26.35 mW with 1.8 V supply voltage. The chip is fabricated under TSMC CMOS 0.18 um.

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.