Amirkabir International Journal of Electrical & Electronics Engineering
Volume:46 Issue: 2, Summer - Autumn 2014

Polarimetric Synthetic Aperture Radar (Pol.-SAR) allows us to implement the recognition and classification of radar targets. This article investigates the arrangement of scatterers by SAR data and proposes a new Look-up Table of Region (LTR). This look-up table is based on the combination of (entropy H/Anisotropy A) and (Anisotropy A/scattering mechanism α), which has not been reported up now. First of all, the color coded images of each of the quantities of H, A and αare extracted and then having the matrix associated with each image and evaluating its histogram, we could obtain the image parameter values corresponding to each interval related to each color code. Then in the output the combination of parameters and the sharing of their images of each frame are extracted and compared with optical images and the extracted satellite map of scattered fields. Results for unconventional targets such as random rough surfaces has indicated that mechanism of scattering irregularities and improper alignment can be used for different purposes in different parts of the frame with fixed values that can be a new method for identifying targets. To make a look up table it is essentially required to evaluate the target parameters and classification of radar images. The method of the extraction of these parameters and applying them on imaging radar systems is exclusive. To validate our work, Pol. SAR data sets are used.

Metallic nanoparticles can exhibit very large optical extinction in the visible spectrum due to localized surface plasmon resonance. Spherical plasmonic nanoparticles have been the subject of numerous studies in recent years due to the fact that the scattering response of spheres can be analytically evaluated using Mie theory. However a major disadvantage of metallic spherical nanoparticles is that their resonance wavelength is independent of the particle dimensions. In this paper, plasmonic resonance of spheroidal metallic nanoparticles is studied. Using the quasi-static approximation, the resonance condition for localized surface plasmon of spheroidal nanoparticles is derived. It is shown that unlike spherical nanoparticles in which the resonance wavelength is independent of the particle dimensions, the additional degree of freedom in spheroids allows for tuning the resonant wavelength. Additionally a formal approach to tune the surface plasmonic resonance of nano-spheroids to a wavelength of interest is presented. The results are confirmed by performing full-wave simulation for gold nanoparticles.

An important property of electromagnetic fields, which arises from the interaction between fields and chiral molecules, is called optical chirality. By enhancing this field property, while maintaining constant input power, we are able to increase absorption of circularly polarized light by chiral molecules of a certain handedness. This enhancement is achieved through the use of achiral plasmonic nano-particles in conjunction with the twisted metamaterials. Optical chirality enhancement (OCE) has an important application in sensing enantiomers of chiral molecules. Here, we present a preliminary scheme to measure enantiomeric excess in mixtures of chiral molecules using OCE boosted by twisted metamaterials. This scheme does not require measurement of a frequency shift in the circular dichroism response.

The importance of constructing the appropriate Green function to solve a wide range of problems inelectromagnetics and partial differential equations is well-recognized by those dealing with classical electrodynamics and related fields. Although the subject of obtaining the Green function for certain geometries has been extensively studied and addressed in numerous sources, in this paper a systematic method using the Method of Separation of Variables has been employed to scrutinize the Green function with Dirichlet boundary condition for the interior region of a closed cylinder. With further rigorous elaboration, we have demonstrated clearly the path through which the Green function can be accomplished. Additional verifications both in analytical and computer-simulating problems have also been performed to demonstrate the validity of our analysis.

In this work, time domain analysis is used to solve Adler’s equation in order to obtain the required time, for an oscillator under external injection, reaching the steady-state condition. Mathematical approach has been applied to fully describe the transient of frequency acquisition in injection-locked LC and Ring oscillators considering their time-varying nature. Then, the analysis is verified by simulations of a ring as well as a typical RF-LC oscillator. Likewise, the effect of initial phase difference of injection signal on locking time and phase noise is theoretically studied. For Ring oscillators, a delay-based time–domain and perturbation analysis are used to reveal the dependency of circuit parameters to the locking time. Finally, the design insights are deduced which enable the designers to evaluate and minimize the timing budget required to achieve injection locking in designing a fast locking oscillator. The mathematical consequences in this work explain why there is no transient behavior while ring oscillator signal propagates from a stage to another, or why the initial phase shift of injection signal has no effect on the phase noise of oscillator.

Variation of frequency and voltage by load changes in a microgrid is a challenge in droop control method. Centralized restoration frequency or voltage in a microgrid requires communication link and therefore affects the advantage of decentralized droop control such as reliability, simplicity and inexpensiveness. This paper proposes a decentralized method that restores the frequency of a microgrid without any communication link and maintains these advantages. The method detects signal changing by wavelet transform (WT) to synchronize distributed energy resource (DER) that interfaced by converter to microgrid. Its operation principle and control method are explained and analyzed. The simulation results are presented to validate the effectiveness of the proposed method.

Model predictive controller is widely used in industrial plants. Uncertainty is one of the critical issues in real systems. In this paper, the direct adaptive Simplified Model Predictive Control (SMPC) is proposed for unknown or time varying plants with uncertainties. By estimating the plant step response in each sample, the controller is designed and the controller coefficients are directly calculated. The proposed method is validated via simulations for both slow and fast time varying systems. Simulation results indicate the controller ability for tracking references in the presence of plant’s time varying parameters. In addition, an analytical tuning method for adjusting prediction horizon is proposed based on optimization of the objective function. It leads to a simple formula including the model parameters, and an indirect adaptive controller can be designed based on the analytical formula. Simulation results indicate a better performance for the tuned controller. Finally, experimental tests are performed to show the effectiveness of the proposed methodologies.