Anew wideband and compact bandstop filter using one dimensional (1-D) mushroom-like electromagnetic bandgap (EBG) structures is proposed in this paper. Although the proposed structure can not be fabricated as easy as defected ground structure (DGS) filters, it has several winning features such as more compactness, better characteristics and no backward radiation. A5-cell 1-D mushroomlike EBG filter is compared with 5-cell and 9-cell circular DGS filters. The 1-D mushroom-like EBG filter is found to be more compact as it requires fewer cells for the same characteristics and also as it has 0.44 times shorter cell length. The proposed EBG filter has a 10-dB bandwidth of 39% while the 5-cell and 9-cell DGS filters have 10-dB bandwidth of 20% and 27%, respectively. Also, the 1-D mushroom-like EBG filter is studied for various number of cells and compared with a two dimensional (2-D) structure. The simulated and measured results are found to be in good agreement.

A novel technique to increase the bandwidth of the conventional planar triangular monopole antenna (PTMA) is presented. With two symmetrical corrugations extended from the flat ground plane, a significant improvement on the impedance bandwidth up to about 4:1 can be achieved. The proposed antenna design is a modification from the conventional volcano smoke antenna (VSA) and can be more compact and easily fabricated. The HFSS 3-D EM solver is employed for design simulation. The effects of the ridged ground plane on the impedance bandwidth are studied. A printed PTMA is fabricated on the FR-4 PCB substrate. Measured VSWR of the printed PTMA with the ridged ground plane is less than 2 from 3 to 12 GHz which covers the UWB frequency band. The measured antenna patterns also show the monopole-type omni-directional radiation patterns from 3 to about 10 GHz.

A new technique is proposed to increase the bandwidth (BW) of slot antenna operated at 2.4 GHz and 5 GHz, over the industrial-scientific-medical (ISM) bands and the Hiperlan2 bands. By splitting two side slots of the Z-like slot antenna into two or three fingers, several additional resonances can be created. By properly arranging the geometry of the feeding structure in the multi-slot region, the double-slot and triple-slot antennas have respectively 2.0 and 3.2 times wider bandwidth than the single Z-slot antenna. According to the results, the proposedtriple-slot antenna can provide two separated impedance bandwidths of 672 Hz (about 28.3% centered at 2.4 GHz band) and 2752 MHz (about 53.5% centered at 5.2 GHz band), making it easily cover the required bandwidths for WLAN operation in the 2.4 GHz bandand 5.2/5.8 GHz bands.

In this paper, a novel stochastic approach, i.e., the electromagnetism-like (EM-like) algorithm, is applied to phase-only syntheses of antenna arrays. The goal is to minimize the pattern sidelobe under null-steering constraints by phase-only adjusting. The mechanism of EM-like algorithm results from the Coulomb's Law of Electromagnetics. It does not require gradient calculations, and can automatically converge at a good solution through the virtual charge of each particle. Simulation results show that the EM-like algorithm can well treat the phase-only optimization of antenna arrays. Although the null-steering constraints will affect the optimization in sidelobe reduction, it can be easily included in the EM-like based optimization scheme. The EM-like algorithm can be applied not only to problems of antenna arrays, but also to many other nonlinear optimization problems in electromagnetic waves.

A very small patch type RFID tag antenna (UHF band) using ceramic material and proximity coupled feeding structure mountable on metallic objects is presented. The proposed tag size is 25×25×3 mm. Both of the radiating part and the feeding part of the proposed antenna is located in the same plate for easy implementation. The resistive and reactive components of the input impedance of the antenna can be easily matched to the tag chip impedance from the size of the feed loop and the distance between feed loop and radiating patch. The antenna satisfactorily operates on metal plates, so it is applicable in many applications. The proposed design is verified by simulation and measurements which show good agreement.

A compact ultra-wideband (UWB) band-pass filter (BPF) with highly rejected notched band is proposed in this paper. The proposed UWB BPF is composed of two cascaded interdigital hairpin resonator units. Interdigital hairpin resonator unit with different coupling is theoretically analyzed. The working frequency of the proposed UWB BPF is 3.1-10.6 GHz and notched band is 5.7-5.8 GHz. Finally, measured results are presented, which are in good agreement with the simulation results.

Geometrical analyses of basic equations of electromagnetics waves propagation in anisotropic dielectric materials with magnetic isotropy are presented in two complementary papers (Part I and Part II). In the present one, analysis arises from quadrics associated with relative dielectric tensor (ε) compatible with conical surfaces that represent the general plane wave equation (relation of dispersion). This study systematizes rays propagation in left-handed materials (LHMs) exhibiting dielectric anisotropy and magnetic isotropy. In particular, indefinite dielectric media where dielectric permittivities are not all the same sign, have been investigated. Graphical alternative procedures for ray tracing in these media are presented.

Asymptotic techniques have been successfully applied to compute electromagnetic wave radiation in various high-frequency engineering domains. Recent approaches based on Gaussian beams for tracking fields may overcome some problems inherent to the ray methods such as caustics. The efficiency of these methods is based on the ability to expand surface fields into a superposition of Gaussian beams. However, some difficulties may arise when the surface is curved. In this paper, we propose a new efficient way to expand fields on a curved surface into Gaussian beams. For this purpose, a new beam formulation called Conformal Gaussian Beam (CGB) is used. The CGBs have been developed to overcome the limitation of the expansion into paraxial Gaussian Beams. The analytical Plane-Wave Spectrum and far-field of a CGB are derived and compared with numerical calculations. A brief parameter analysis of the CGBs is realised.

Geometrical analysis of basic equations of electromagnetics waves propagation in anisotropic dielectric materials with magnetic isotropy are presented in two complementary papers (Part I and Part II). In this paper, analysis arises from local properties of dielectric permittivity tensor and Mohr's plane graphical construction compatible with circumferences that represent general plane wave equation. This theoretical study allows to know how rays propagate in left-handed metamaterials (LHMs) exhibiting dielectric anisotropy and magnetic isotropy. Geometrical analysis yields plane graphical procedures for ray tracing, that are extremely easy. In particular, indefinite dielectric media, where dielectric permittivities are not all the same sign, has been investigated and a joint study of materials having the same eigenvalues of ε, but with opposite values of μ_r is performed. The opposite sense of propagation of rays in "opposite media" (media with opposite values of ε_i and μ_r) has been also shown. It must be pointed out that the presented method always allows graphical plane constructions, even when dealing with biaxial media.

A hybrid empirical-neural (HEN) model, to account for a loading effect of arbitrary raised dielectric slab in a microwave cylindrical metallic cavity, is presented. It is based on combination of an approximate model, as a rough empirical knowledge holder, and multi-layer perceptrons (MLP) neural network. In comparison with the model based only on MLP network, more accurate and efficient resonant frequencies calculation is achieved.

It is proposed that the application of defected ground structures (DGS) and electromagnetic bandgap (EBG) reduce the phase velocity, increase effective permittivity of microstrips and reduce the effective the wavelength which eventually lead to the reduction of overall length of Wilkinson power dividers. Furthermore, the adjacent strip lines may approach each other, which cause coupling problems. The undesired coupling maybe cancelled by connecting a capacitance in parallel with the isolation resistor of Wilkinson power divider. Application of DGS and EBG will not only reduce the dimensions of the divider, but also improves its scattering parameters.

Cyclic delay diversity (CDD) is a simple approach to increase the frequency selectivity of the channel in an orthogonal frequency division multiplexing (OFDM) based transmission scheme. However, CDD can cause serious degradation in the performance of channel and frequency estimation in the frequency domain. This paper suggests a post-FFT frequency estimation scheme suitable for arbitrary cyclic delays in the CDD-OFDM system. By partitioning uncorrelated pilot subcarriers into subsets to be flat, and performing frequency estimation for each pilot subset, a robust integer frequency offset estimation scheme is derived.

A technique for natural frequency extraction without a prior knowledge of the number of natural frequencies is proposed. The proposed scheme is based on the GPOF method with the overestimated number of natural frequencies, and it has been shown from simulation result that the proposed method is superior to the GPOF method. The method is applied to the extraction of the natural frequencies of the thin wires whose exact natural frequencies are known. While the absence of the true natural frequency has much effect on the transient response reconstruction, the absence of the spurious natural frequency has little effect on the transient response reconstruction. Using the above property, true natural frequencies and spurious natural frequencies can be discriminated.

Current driven electrostatic ion cyclotron instability has been studied for parallel flowv elocity shear with perpendicular a.c. electric field to the ambient magnetic field for bi-Maxwellian density drift distribution function. The method adopted for expression for dispersion relation and growth rate is kinetic approach and method of characteristic solution for ionospheric plasma. The effect of a.c. frequency, density gradient, and velocity shear scale length has been discussed.

A 2×2 quasi-Yagi antenna array fed by a novel orthogonal T junction is presented. The orthogonal T junction is constructed with a traditional microstrip T junction, two planar microstrip to CPW transitions and two orthogonal microstrip to CPW transitions. The orthogonal T junction can be integrated with the quasi-Yagi array element directly. A 2×2 prototype operated from 7.6 GHz to 12 GHz is fabricated and measured.

Turbo equalization is applied to microwave channel in this paper, and we bring forward an improved Turbo equalization algorithm named Max-Log-Map. A simulation based on a given microwave fading channel has been made. The results show that performances are close to each other between improved TE-Max-Log-Map and Log-Map, and the coding gain is 1 dB at 10^-4 of BER compared with Max-Log- Map. The improved Max-Log-Map method improves the reliability of microwave communication.

There are various techniques for the deposition of SiO₂ films on silicon. Flame Hydrolysis Deposition (FHD) techniques is the most economical technique for the deposition of SiO₂ films. In this technique the SiO₂ films are deposited by hydrolysis of SiCl₄ in a high temperature H₂-O₂ flame. In the present study we present the growth of SiO₂ films by indigenously developed FHD system and organic compound Tetraethoxyorthosiliate/Tetraethoxysilane TEOS as source of silicon. The films deposited by the FHD system are porous and need annealing at higher temperatures for the densification. We present here for the first time direct dense glassy transparent SiO₂ films deposited by our FHD system. The optical properties of the deposited films were studied by ellipsometery. FTIR spectroscopy was carried out to study the various characteristic peaks of SiO₂ bonds. The peaks corresponding to Si-O-Si stretching, bending and rocking modes are observed at 1090 cm^-1, 812 cm^-1 and 463 cm^-1 respectively. The absence of peaks corresponding to the OH bond in the deposited film reveals that the deposited films are most suitable for the photonic devices application. The surface analysis was carried out using SEM. The EDAX of the deposited film confirms the composition of the Si and O in the deposited film.

In this paper, a compact design and construction of microstrip Ultra Wide Band (UWB) antenna is proposed. The proposed antenna has the capability ofop erating between 4.1 GHz to 10 GHz. The antenna parameter in frequency domain analysis have been investigated to show its capability as an effective radiating element. Furthermore, time domain Gaussian pulse excitation analysis in UWB systems is also demonstrated in this paper. As a result, the simulation results demonstrated reasonable agreement with the measurement results and good ultra-wideband linear transmission performance has also been achieved in time domain.

In this paper, we present a new domain decomposition technique which considers the effect of multiple reflections between the subdomains. This method has the ability to simulate accurately large electromagnetic problems that are difficult to handle using the direct application of the FDTD method. The results for the test examples considered in this paper compare well with the direct FDTD solution, and serve to validate the proposed scheme.

A class of linear derivative constraints, which provides robustness to the conventional narrowband uniform linear array configuration so as to handle broadband and moving jammer sources problem is presented. The robust modification of linear constrained minimum variance (LCMV) algorithm is given to broaden the null widths in the jammer directions. Numerical results show that the proposed algorithm has a better performance in broadband and moving jammer scenarios in terms of maintaining beamwidth broadening and capability of rejecting interferences.