Electromagnetic ion cyclotron (EMIC) waves have been studied in the presence of AC electric field perpendicular to ambient magnetic field in the ionosphere with observed superthermal electrons. The presence of 4 eV-50 eV superthermal electrons have been recently seen by Indian SROSS-C2 satellite, Lorentzian Kappa distribution has been used to derive dispersion relation and growth rate using method of characteristics and kinetic approach. The free energy source like anisotropy in temperature, AC electric field and presence of superthermal electrons affect the growth rate. Lorentzian kappa distribution plays important role in giving the wide spectrum range of emitted frequencies.
To design less costly and time consuming Photonic Crystal Fibers it is better to use Empirical Relations Method instead of Scalar Effective Index Method. If we compare both empirical relations method and scalar effective index method by accurate and powerful methods like Full-Vector Finite Element Method, we find that empirical relations method has less error than scalar effective index method in calculating PCF parameters such as nfsm, neff , and the second order dispersion. According to the investigations, we concluded, the inherent error of scalar effective index method approximately increases when pitch decreases. In large pitches the calculation of dispersion by scalar effective index method reveals less error in low wavelengths than high wavelengths and finally we calculated the third order dispersion which is important in some applications.
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.
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.
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.
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.
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.
A time reversal method is studied and adapted to through-the-wall detection and localization of moving targets. Tests are realised on experimental data in a synthetic aperture radar configuration. The efficiency of the method to extract a moving target from a cluttered environment is proved on experimental data.
Diffraction of a plane wave from a geometry which contains an infinite slit in a perfect electric conducting (PEC) plane and a perfectly electromagnetic conductor (PEMC) cylinder is presented. The method is based on the extension of Clemmow, Karp and Russek solution for the diffraction by a wide slit. The results are compared with the published work and agreement is fairly good.
This paper presents a new frequency-sweep approach for the efficient calculation of S-parameters of planar microwave structures. The approach is based on approximating the frequency dependence of the real and imaginary parts of the S-parameters using neural networks. Due to its superior performance, radial basis functions neural network (RBF-NN) is adopted. A limited number of frequency samples are used to train the RBF-NN. Then, the trained RBF-NN is capable of providing a smooth frequency response with very high accuracy in a fraction of a second. The proposed method is applied to a number of planar microwave structures such as: Patch antenna with an inset feed, band-rejection filter, and branch-line coupler. According to the presented results, a speed factor of at least 10 is measured, and a maximum percentage error of 3.29% is recorded.
This paper considers the influence of interchannel crosstalk on pulse timing shift and optical power due to the propagation of optical pulse through a nonlinear dispersive fiber. The numerical results are shown. An influencing parameter of the pulse distortion through the fiber is the eye opening penalty.
Feature extraction is a challenging problem in radar target identification. In this paper we attempt to exploit the sparse property of the scattering signature with a undercomplete dictionary for target identification, and establish a feature extraction scheme based on the undercomplete dictionary. Furthermore, as an application, we present a feature vector, named as the atom dictionary feature, which is extracted from the scattering signatures over a wide-angle sector. Numerical simulation results show that the proposed atom dictionary feature can improve the performance of radar target identification due to the exploitation of the sparse property of the scattering signature.