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.

In this work, Support Vector Machine (SVM) formulation is worked out based upon ''L'' measured data for the resonant frequency, operation bandwidth, input impedance of a rectangular microstrip antenna. Results of the formulation are compared with the theoretical results obtained in literature, much better characterization is observed with greater accuracy. At the same time, Artificial Neural Network (ANN) is employed in generalization of the data on the resonant frequency, operation bandwidth, and input impedance of the antenna. Performances of the two advanced nonlinear learning machines are compared and superiority of the SVM is verified.

A new uniplanar electromagnetic bandgap (EBG) power/ground planes is proposed with broadband suppression of simultaneously switching noise (SSN) from 370MHz to 4.9 GHz. Meander line bridge is used to increase the inductance between the two neighboring units, which can make the proposed power/ground structure suppress the SSN at low frequencies effectively. Excellent SSN suppression performance is validated both numerically and experimentally. Good agreement is seen. The proposed uniplanar EBG power/ground planes structure can be widely used in high speed integrated circuits.

Research of antenna Radar Cross Section (RCS) is very important for low observable platform. Aperture coupled microstrip antenna is fit for the low RCS antenna design because the feed network produce less effect on scattering of microstrip patch. A novel aperture coupled microstrip antenna is proposed, which utilizes the chip-resistor load, ground slot and miniaturization, to realize RCS reduction. Aperture coupled antenna with rectangular patch is chosen as the reference antenna. Two antennas are simulated and measured. The measured results show that the designed antenna realizes only 0.5 dB gain loss while RCS are reduced in almost all the frequency band.

A thin internal planar antenna for GSM/DCS with a hollow shorting cylinder suitable for integration with an embedded digital camera for a mobile phone is presented. A small vertical ground plane electrically connected to the system ground plane of the mobile phone is used. The vertical ground plane can function as an effective shield wall between the antenna and the nearby electronic elements in the mobile phone. The method of moments is used to simulate the antenna structure and calculate the radiation characteristics of the antenna.

This paper proposes an improved adaptive approach involving Bacterial Foraging Algorithm (BFA) to optimize both the amplitude and phase of the weights of a linear array of antennas for maximum array factor at any desired direction and nulls in specific directions. The Bacteria Foraging Algorithm is made adaptive using principle of adaptive delta modulation. To show the improvement in making the algorithm adaptive, results for both adaptive and nonadaptive algorithms are given. It is found that Adaptive Bacteria Foraging Algorithm (ABFA) is capable of improving the speed of convergence as well as the precision in the desired result.

Magic tee is a widely used component in microwave systems; the four arms of a conventional magic tee direct at four different directions, which occupy much space and give inconveniences to the assemblage of a system. In this paper, a waveguide narrow-wall slot directional coupler and an E-plane dielectric loaded waveguide phase shifter are used to make up of a magic tee with four arms in the same H-plane. The narrow-wall slot directional coupler is analyzed with mode matching method and optimized with simulated annealing method, and the dielectric loaded waveguide phase shifter is designed with edge based finite element method. Numerical results of the magic tee are presented, which show that the performance of the designed magic tee is good.

This paper reports the miniaturization of a microstrip 90 degree coupler by substituting the quarter wave transmission lines employed in conventional 90 degree coupler with its equal circuits consisting of two oblique stubs and an inductor and capacitors. Reduction of the coupler to 27% its size is reported here. This coupler is designed at 1070MHz for using in even harmonic mixers of 3G mobile receivers. Furthermore, the coupler can accurately divide the input signal by two parts with the same power and 90 degree phase difference. Also, the reflection coefficient and the isolation are as good as conventional one and coupling procedure is better than it.

Finite-Difference Time Domain (FDTD) is used to calculate the input impedance of the cylindrical dielectric resonator (DRA) antenna with different dimensions. A lumped- element circuit model for the input impedance calculation is proposed. The genetic algorithm is used to calculate the elements of the equivalent circuit. The Model-Based Parameter Estimation (MBPE) technique is used to find the variation of each element in the equivalent circuit with varying the physical dimensions of the antenna. The use of this method reduces the time required for calculating the input impedance of the cylindrical DRA in eachv ariation of the antenna dimension.

This paper reports a high IIP3 even harmonic mixer with a new circuit configuration. This mixer employs an antiparallel diode pair, open and short circuited stubs and a radial stub as filters to separate RF input signal, Baseband output signal and LO Power. This mixer is used for down converting 3G Mobile downlink Signal at 2140MHz to BaseBand by using a local oscillator at 1070MHz in direct conversion configuration. This mixer must comply with the requirements specified by 3G UMTS: 3rd order Input Intercept Point = 14.466dBm ≥ 11 dBm, Noise Figure = 9 dB and Conversion Loss = 11 dB.

We consider the inverse problem of determining both the shape and the conductivity of an un-uniform conductivity scatterer buriedin a three-layer structure by the genetic algorithm. An ununiform conductivity scatterer of unknown shape and conductivity buriedin the secondla yer scatters the incident wave from the first layer or the thirdla yer. We measure the scatteredfieldin the first andthird layers. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulatedin to an optimization problem. The genetic algorithm is then employedto findout the global extreme solution of the object function. As a result, the shape andthe conductivity of the scatterer can be obtained. Numerical results are given to demonstrate that even in the presence of noise, good reconstruction has been obtained.