The scattering of visible light by hexagonal-shaped column containing densely packed inclusions is simulated by a combination of ray-tracing and Monte Carlo techniques. While the ray tracing program takes care of the individual reflection and refraction events at the outer boundary of the particle, the Monte Carlo routine simulates internal scattering processes. A dense-medium light-scattering theory based on the introduction of the static structure factor is used to calculate the phase function for densely packed inclusions. Numerical results of the phase function for a randomly oriented hexagonal-shaped ice crystal with multiple densely packed inclusions are evaluated.

Closed-form expressions for the input impedance of halfwavelength rectangular microstrip antennas fed by coaxial connectors of different sizes at any point on any one of the non-radiating edges and open-circuited at the other ends are derived. Good agreement between computed and measured data is obtained.

With the technological growth of broadband wireless technology like CDMA, OFDM and MIMO, a lots of development efforts towards wireless communication system and imaging radar system are well justified. It has been recently shown that multipleinput multiple-output (MIMO) antenna systems have the potential to dramatically improve the performance of communication systems over single antenna systems. Efforts are also being imparted towards a Convergence Technology. The convergence between a communication and radar technology which will result in ITS (Intelligent Transport System) and other applications. This motivates development of the present article. This is an effort in the direction to utilize or converge the communication technologies towards radar and to achieve the interference and clutter free quality remote images of targets.

In this paper, a high data rate Ultra-Wideband Differential Transmitted-Reference (UWB-DTR) system which is one of the best and simplest available TR scheme is analyzed over IEEE 802.15.3a Channel Model 1 (CM1). We show that these systems need equalization in high data rate mode of operation because in such a case harsh nonlinear inter symbol interference (ISI) exists and degrades performance severely. The performance of the DTR system in CM1 is derived both analytically and via simulations by taking into account noise, inter path/pulse interference (IPI), and ISI. Uniform approximation for ISI distribution is proposed for the first time which gives a closer approximation than Gaussian one. All simulation and analytical results are obtained for CM1 but generalization to other channel models is also possible.

A full-wave analysis of the scattering parameters of a straight-to-bent microstrip line coupling is performed using a FEM technique. The numerical results, showing the influence played by the geometrical parameters of the structure on the electromagnetic coupling, are then employed to derive an equivalent circuit useful to be employed in CAD tools. A third order polynomial approximant useful to compute the equivalent circuit elements is finally provided.

The Sub-Entire-Domain (SED) basis function method has been applied to solve electromagnetic problems of irrectangular periodic structures with finite sizes efficiently. Three typical irrectangular periodic structures such as parallelogrammic periodic structures, triangular periodic structures, and trapeziform periodic structures are investigated using the SED basis function method. Just as the SED basis functions for rectangular periodic structures, the new SED basis functions for irrectangular periodic structures are defined on the support of each single cell, and the corresponding dummy cells are introduced to obtain the new SED basis functions. Using the proposed SED basis function method, the original large-scale problem is decomposed into two small-size problems. One is the determination of new SED basis functions, and the other is to solve the whole problem using MoM and SED basis functions. Numerical examples are given to prove the validity and efficiency of the new method.

For a long time power pattern synthesis has been considered to produce shaped beam patterns due to the number of degrees of freedom when compared with field pattern synthesis. However, severaladv antages exist if synthesis techniques are based on field patterns, since the relationship between the array factor and the source distribution is a Fourier transform. In this case, quicker and efficient algorithms are obtained with the Fast Fourier Transform (FFT) to perform the calculations. Therefore, this work presents a new technique that synthesizes shaped beam patterns through the control of non-uniformly samples of the array factor, both in amplitude and phase. The sample phases increase the number of degrees of freedom. To produce complex patterns, the sample phases of the shaped beam region are used to create more oscillations in the ripple structure than the ones produced with the realpatterns. Not only this procedure yields a narrower transition region between the beam zone and the sidelobe zone but also smaller dynamic range ratios are obtained. Furthermore, it is described how to impose nulls in prescribed directions of the complex patterns. Some examples are presented to demonstrate the application of the synthesis technique.

In this paper, a Ku band fan beam reflector back array antenna is introduced. This is made up of two main parts that are planar array and main reflector. The proposed antenna has dimensions of 103.3×27.5×12mm³ including the reflector. This antenna with high gain for incorporating in Ku band radars at 13.4-14 GHz is described. The fan beam radiation patterns with monopolar characteristics i.e., the cross-polarization is at least 10 dB lower than the co-polarization and are obtained in the frequency band of interest. The maximum gain for proposed antenna is 16.6 dBi at 13.75 GHz and the peak gain generally >16 dBi throughout the frequency band of interest.

This paper presents a novel wideband bandpass filter making use of complementary split-ring resonator (CSRR) as the basic resonant unit. The resonant characteristic of CSRR is carefully studied through full wave analysis. The coupling of CSRR structure is very strong that can be used to realize wideband filter with small insertion loss. A filter with center frequency at 3.5 GHz, passband from 3.1 GHz to 3.8 GHz is designed and fabricated. The measured results are in good consistent with simulated results.

In this paper, using moment method in the spectral domain, full wave analysis of two orthogonal microstrip transmission lines in two layered PCB board is presented. First, using 1-dimensional spectral domain method, the propagation constants and the currents on each line are obtained, without considering of the other line. Then, using Galerkine's method in 2 dimensional spectral domain, the scattering parameters of the structure are calculated. The results of our analysis are compared by the quasi-TEM approach. Comparisons show good agreement between our results and quasi-TEM approach.

The generation of the picture out of the SAR raw data is a computational intensive task. Both range compression and azimuth compression utilized Fast Fourier Transform (FFT) algorithms and Inverse Fast Fourier Transform (IFFT) in order to perform convolution with respective reference signal. Thus FFT and IFFT occupied about 70% of the total computation operation in SAR image formation. In this paper a modified algorithm based on conventional FFT is proposed to optimize the computation performance. It is shown that the proposed algorithm can essentially achieve better performance with minimum computational burden compare to conventional FFT.

In this paper, miniature planar UWB filters with circular slots in ground is presented and we are using a new technique by etching a wideband circular-shape slot resonator in the ground plane of the filters. The proposed filters have compact size of 15 × 12.4mm². Two filters are introduced and the final design achieves flat insertion loss and linear phase of S₁₂ throughout the passband (3.14-8.28 GHz) but occasional slight ripple occurs. Two different results are shown and the minimum insertion loss is less than 0.13 dB for both of presented filters.

Corrugated elliptic waveguide in actually extensive application is analyzed by using the mode matching method and Mathieu function. Considering space harmonics in the interior and higher order modes in the slot region of the corrugated elliptic waveguide, the dispersion equation of even TM modes is derived. The dispersion and attenuation characteristics as well as the influence of passband and stopband properties with the changes of structural parameter are investigated in detail. The calculated results in good agreement with ones in the relevant references are of very important values in theoretical studies and actual applications of corrugated elliptic waveguide for microwave engineering.

Scattering of a spherical wave by a finite PEC and a finite impedance cylinder is studied theoretically. Source of excitation is spherical wave is produced by a dipole with arbitrary orientation. First we derive surface fields induced on an infinite cylinder when it is illuminated by an arbitrary oriented dipole. By the use of the currents on the infinite cylinder excited by an arbitrarily oriented dipole, approximate expressions for two components of the far-zone scattered electric field of a finite PEC and a finite impedance cylinder are derived. The validity of the approximation depends on the conditions that the cylinder must be long compared to the wavelength. The theoretical results are compared to the available results in the literature.

We present a generally symmetrical circuit model to describe all kinds of metamaterials with effective permittivity and permeability. The model is composed of periodic structures whose unit cell is a general T-type circuit. Using the effective medium theory, we derive analytical formulations for the effective permittivity and effective permeability of the circuit model, which are quite different from the published formulas [1, 2]. Rigorous study shows that such a generally symmetrical model can represent right-handed materials, left-handed materials, pure electric plasmas, pure magnetic plasmas, electric-type and magnetic-type crystal bandgap materials at different frequency regimes, with corresponding effective medium parameters. Circuit simulations of real periodic structures and theoretical results of effective medium models in this paper and in [1] and [2] are presented. The comparison of such results shows that the proposed medium model is much more accurate than the published medium model [1, 2] in the whole frequency band.

An optimal beamformer attempts to increase SNR at the array output by adapting its pattern to minimize some cost function. This is to say that, the cost function is inversely associated with the quality of the signal. Therefore by minimizing the cost function we can maximize signal at the array output. The primary optimal beamforming technique discussed in this paper will be MMSE, LMS, Frequency Domain LMS for GPS multipath reduction. In case of a GPS satellite, the DOA of the desired signal is mathematically known because the position of a satellite in an orbit is fixed at a particular time instant. So in some particular adaptive antenna algorithm the DOA of the desired signal is directly given as input.

A new method of choosing the regularization parameter, originally developed for a general class of discrete ill-posed problems, is investigated for electromagnetic inverse scattering problems that are formulated using a penalty method. This so-called Normalized Cumulative Periodogram (NCP) parameter-choice method uses more than just the norm of the residual to determine the regularization parameter, and attempts to choose the largest regularization parameter that makes the residual resemble white noise. This is done by calculating the NCP of the residual vector for each choice of the regularization parameter, starting from large values and stopping at the first parameter which puts the NCP inside the Kolmogorov- Smirnov limits. The main advantage of this method, as compared, for example, to the L-curve and Generalized Cross Validation (GCV) techniques, is that it is computationally inexpensive and therefore makes it an appropriate technique for large-scale problems arising in inverse imaging. In this paper, we apply this technique, with some modification, to the Tikhonov-regularized functional arising in the 2-D Transverse Magnetic (TM) inverse electromagnetic problem, which is formulated via an integral equation and solved using the Born iterative method (BIM).

This paper presents a modification for Bluetooth frame structure to improve its performance over both Additive White Gaussian Noise (AWGN) and fading channels. The paper investigates the effect of using different block codes on the performance of the Bluetooth system. Both Hamming and BCH codes with different lengths are studied as error control codes for the Bluetooth frame. Experimental results reveal that shorter Hamming codes have a better performance in AWGN channels. Also, the BCH (15, 7) code has a better performance for interleaved channels. All this work is devoted to Bluetooth 1.1 version.

Tunability of fiber Bragg grating (FBG) in transition region is used to implement wavelength-selective optical intensity modulator, which superimposes a secondary low-speed data on the transit high-speed payload optical signal. Theoretical model of the device is developed and verified by measurements in the linear and nonlinear slopes of the FBG. Experiments with strong and relatively weak gratings confirm the wavelength-selectivity and stability of modulation. The fiber-based modulator is employed for optically tagging or labeling individual wavelength channels using baseband and amplitude-shift keying (ASK) modulated signals. The wavelengthselective channel labeling scheme is useful for the control and management of the optical circuits and services in WDM networks.

Ray tracing has been successfully usedin prediction of wave propagation models in recent years. Although this method has its own obvious benefits, it suffers from a big problem: slow performance. In this paper, novel methods are proposed in which the main focus is on reducing the number of ray-facet intersections. First a preprocessing methodis proposed which reduces the number of ray-facet intersection tests dramatically. Later this method is combined with a volume bounding algorithm to make improvements in the speed of ray-tracing simulations, even more.