In this paper, the region of interest consists of a perfect conductor, coated with the two layer dielectrics under the air. The completed analytical formulas have been derived for the electromagnetic field due to a vertical electric dipole in the four-layered region when both the source point and observation point are located in the upper dielectric layer. Similar to the three-layered case, the trapped surface wave, which is contributed by the sums of residues of the poles, can also be excited efficiently by a vertical electric dipole in the four-layered region. The lateral wave is determined by the integrations along the branch cuts.

Copper-cobalt ferrites with general chemical formula Cu_xCo_1-xFe₂O₄ (with x = 0.0, 0.4, 0.6 & 1.0) were prepared by ceramic method. The solid state reaction was confirmed by XRD patterns. DC conductivity was measured by two probe method. Electrical resistivity is found to increase on lowering of sintering temperature and time. At x = 1.0, the conduction is mainly due to hopping of electrons leading to n-type conductivity while at x = 0.0, conduction is due to holes leading to P-type conductivity. The lowest conduction at x = 0.4 is attributed to the electron hole compensation. SEM micrographs were obtained from JEOL scanning electron microscope. The micrographs reveal that an average grain size increases with sintering temperature and time as a result of decrease in porosity. This leads to the decrease in resistivity with sintering temperature and time. One of the factors for higher conductivity in ferrites is an increase in average grain size and decrease in pore concentration during the heat treatment.

An effective method for improving the characteristics of the microstrip parallel coupled line coupler is proposed. Some grooves are oriented parallel to the strips and just next to them. It can be shown that an appropriate depth of the grooves can be used for equalizing the even- and odd-mode phase velocity in a coupled microstrip lines with proper geometrical dimensions. Sets of design graphs are derived for various depths of grooves as a parameter and with curves that implies phase velocity equalization curves. The simulated scattering parameters for couplers in conventional and proposed topology show the efficacy of the new grooved substrates.

By properly exciting higher order modes at an aperture it is possible to achieve higher aperture efficiencies. High efficiency antennas are mandatory in many applications, as discrete lenses, since the single element efficiency deeply affects the efficiency of the whole lens. In this contribution a genetic algorithm is applied to the mode matching analysis of square horns to achieve high radiation efficiency over a relatively wide band.

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.