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.

In this paper we formalizes a new discrete time model of digital array based MIMO radar in which the combined effects of the transmit filter, physical MIMO multi-path channel fading, and receive filter. It has the same sampling period as that of the MIMO receiver. Apart from this, SNR value and target detection are different in compared to the continuous domain nature. Orthogonality is introduced using OSTBC (orthogonal space time coding) including interelement spacing at the transmitter is greater than the target beam width coverage. For space and temporal diversity we have considered distributed source model. and modulation schemes respectively. Frequency diversity is achieved using N point IFFT (N = 32, 64, 256, 1024) at the base band. Thus, three dimensional analysis with respect to diversity and selective nature of fading channel in digital array based MIMO radar are now used for performance analysis based on probability of detection, symbol error rate, model error, power spectral density at the receiver and SNR value at the detector.

Planar multilayer structures have found several applications in electromagnetics. In this paper, an equivalent model based on the bi-characteristic-impedance transmission line (BCITL) is employed to model planar multilayer structures effectively for both lossless and lossy cases. It is found that the equivalent BCITL model provides identical results, for both perpendicular and parallel polarizations, as those obtained from the propagation matrix approach.

A fast analysis of aperture-coupled reflectarrays is presented in this work in terms of transmission line model. The circuital approach is adopted to derive the phase design curve as a function of the current flowing on the equivalent impedance of the single radiating element. Computational costs are drastically reduced with respect to standard full-wave methods. Numerical and experimental validations are discussed on slot-coupled reflectarray configurations working at different operating frequencies.

This paper presents microstrip transmission lines for designing a microstrip open loop resonator bandpass filter and a novel dual band transmitter. Microstrip open loop resonator bandpass filter with the dumbbell DGS under feed lines enhances the harmonic suppressed at the center frequency of 2.44 GHz. An asymmetric dumbbell DGS-integrated microstrip line is applied to the dual band transmitter which performs as a frequency doubler at 6.8 GHz or a power amplifier at 2.4 GHz. For the proposed bandpass filter,it has a wide stopband characteristic with attenuation -25 dB up to 8 GHz and has an -1.25 dB insertion loss by using two dumbbell DGS. Measurements of the dual band transmitter show that in frequency double mode,fundamen tal suppression and maximum output are -41 dBc and 7.8 dBm. And in amplifier mode,second harmonic suppression,P1 dB and gain achieve -52.6 dBc,13.7 dBm and 16.5 dB, respectively.

A numerical method is presented for determining the static charge distribution and capacitance of a round disk capacitor. Based on equivalent surface charge distributions, an integral equation subject to the boundary conditions is transformed into an algebraic equation by using the method of moments. In the proposed scheme to eliminate the discretizing errors often encountered in other techniques, annular patch subdomains are introduced, not only to improve the accuracy of solutions, but also to reduce the matrix size of the resultant equation. By solving the transformed algebraic equation, the charges per unit area on the interfaces are numerically determined. With use of the free charge on plates obtained by using annular patches, the capacitance is more accurately calculated. The equipotential lines around a round disk capacitor are also calculated. In order to show the usefulness of this method, the employed scheme is applied to a single circular disk with an exact solution, and to the dielectric filled capacitor partially covered by plates. Those results are examined and discussions are also made to support the validity of the presented scheme.

Design of a compact dual frequency microstrip antenna is presented. The structure consists of a slotted circular patch with a dielectric superstrate. The superstrate, not only acts as a radome, but improves the bandwidth and lowers the resonant frequency also. The proposed design provides an overall size reduction of about 60% compared to an unslotted patch along with good efficiency, gain and bandwidth. The polarization planes at the two resonances are orthogonal and can be simultaneously excited using a coaxial feed. Parametric study of this configuration showed that the frequency ratio of the two resonances can be varied from 1.17 to 1.7 enabling its applications in the major wireless communication bands like AWS, DECT, PHS, Wi.Bro, ISM, and DMB. Design equations are also deduced for the proposed antenna and validated.

Simultaneous multiple beam generation by phased array antennas have great importance in recent time, e.g., multiple access satellite communication systems, MIMO (multiple input and multiple output), target tracking radars etc. Here in this article a novel yet simple wideband multiple beam formation network (BFN) has been proposed. Unlike the conventional phase shifter based system, this scheme is based on true time-delay units which is potential for wideband application.

A method of moment based analysis of the co-channel interference at waveguide joints has been presented using Multi Cavity Modeling Technique (MCMT). The proposed analysis has good agreement with the theoretical; CST microwave studio and HFSS simulated data.

A new antenna structure comprising a semicircular microstrip patch alongside a small rectangular shape ground proximity fed by a microstrip line is proposed. On a thin substrate this antenna achieves in the range of 5.8-12.9 GHz an impedance bandwidth of almost 75%. Details of the antenna design, simulation and measured results on the return loss and the E and H-plane radiation pattern of the proposed antenna are presented.

A semi-analytic method, based on scattering approach is applied to analyze the finite size photonic crystal cavities surrounded by cylindrical dielectric rods.The resonant frequency and the quality factor (Q) are determined by this method.Also, with a source at the center of the cavity, field and energy distribution can be obtained at different frequencies.The algorithm is simple to simulate on PCs. There is no need for absorbing boundary conditions which are required in most numerical methods.Using the symmetry of the structure the computational cost is reduced to 1/8 and 1/12 those of the square and hexagonal lattices respectively.Since the computational time is very low (in the order of one minute) the variation in size and dielectric constant of the rods can be examined easily.It is shown as an example that by varying the radius of the rods according to their distance from the center of the cavity, the Q factor is increased considerably in comparison with that of uniform structures.

A novel design approach for erbium-doped fiber amplifiers is proposed based on particle swarm optimization algorithm. The main six parameters of the EDFAs including: pumping wavelength, input signal power, fiber numerical aperture, erbium-doped area radius, erbium concentration, and the fiber length are optimized utilizing a fast and efficient method called particle swarm optimization algorithm. In this paper, a combination of fiber amplifier bandwidth, gain, and flatness are taken into account as objective function and the results are presented for different pump powers. Our investigation shows that particle swarm optimization algorithm outperforms genetic algorithm in convergence speed, straightforwardness, and coping with highdimensional spaces, when the parameters of EDFA are to be optimized. It has been shown that the required time for the optimization of the fiber amplifier parameters is reduced four times by using particle swarm optimization algorithm, compared to genetic algorithm method.

Hemispherical dielectric resonator (HDR) antenna excited with a thick slot at the short circuited end of waveguide is analyzed theoretically and verified experimentally. The problems are formulated using the Green's function approach; with unknown slot currents solved using the method of moments (MOM). The HDR is modeled using exact magnetic field Green's function due to the equivalent magnetic current in the slot. The field inside the waveguide is expressed in terms of model vectors and modal functions. Thickness of the slot is analyzed using cavity approach. For the analysis of HDR antenna part, the modal series is represented as a sum of particular and homogeneous solutions. The particular solution is computed efficiently using spectral domain approach. In order to determine the effects of varying design parameters on bandwidth and matching, sensitivity analysis is carried out using the code developed. Measurements were carried out to verify the theory, and reasonable agreement between them is obtained.

A magnetized thin layer mounted on a PEC surface is considered as an alternative for an absorbing layer. The magnetic material is modeled with the Landau-Lifshitz-Gilbert equation, with a lateral static magnetization having a periodic variation along one lateral direction. The scattering problem is solved by means of an expansion into Floquet-modes, a propagator formalism and wavesplitting. Numerical results are presented, and for parameter values close to the typical values for ferro- or ferrimagnetic media, reflection coefficients below -20 dB can be achieved for the fundamental mode over the frequency range 1-4 GHz, for both polarizations. It is found that the periodicity of the medium makes the reflection properties for the fundamental mode almost independent of the azimuthal direction of incidence, for both normally and obliquely incident waves.

In this paper, equations are derived for solving the important geometrical parameters of the ring-focus antenna with a variable focal distance for forming an elliptic beam, a simple and efficient method for this antenna is presented, and measured and calculated patterns are given. This antenna can form a high-efficiency elliptic beam.

We study the influence of atmospheric turbulence on satellite communication by the theoretical analysis of propagation characteristics of electromagnetic waves through inhomogeneous random media. The analysis is done by using the moment of wave fields given on the basis of a multiple scattering method. We numerically analyze the degree of the spatial coherence (DOC) of electromagnetic waves on a receiving antenna and the bit error rate (BER) of the Geostationary Earth Orbit (GEO) satellite communication in Ka-band at low elevation angles on the assumption that the spatial coherence of received waves decreases and spot dancing only occurs. In this analysis, we consider the Gaussian and the Kolmogorov models for the correlation function of inhomogeneous random media. From the numerical analysis, we find that the increase in BER for the uplinkcomm unication is caused by the decrease in the average intensity due to spot dancing of received beam waves and that the increase in BER for the downlinkcomm unication is caused by the decrease in DOC of received beam waves. Furthermore, we find that the decrease in DOC of received waves and the increase in BER becomes much more in the Kolmogorov model than in the Gaussian model.

Maximum likelihood (ML) direction-of-arrival (DOA) estimation is essentially an optimization of multivariable nonlinear cost function. Since the final estimate is highly dependent on the initial estimate, an initialization is critical in nonlinear optimization. Alternating Projection (AP) initialization has been proposed as computationally efficient method for the initialization of the ML DOA cost function. In this paper, we propose a multi-dimensional (M-D) search scheme of uniform exhaustive search and improved exhaustive search. Improved exhaustive search is used to reduce the computational load of uniform exhaustive search. In the improved exhaustive search algorithm, the two-step procedure is applied to reduce the computational load of the uniform exhaustive search initialization scheme. In numerical results, it is shown that the performance of the proposed scheme is better than that of AP initialization.