Spectral and Dispersion Properties of Long Period Fiber Grating for Optical Communication Systems

Present work deals with the analytical study of spectral and dispersion properties of long period fiber grating (LPFG) under linear regime. The standard parameters in the understanding of the optical features of an LPFG have been analyzed using the linear coupling processes such that one can appreciate without going through the cumbersome mathematical treatment of coupled mode equations the basic characteristics of the grating. We have analyze transmittance, phase factor, group delay and group velocity dispersion (GVD) of the LPFG as functions of physical parameters like operating wavelength, grating length, induced index change, and detuning parameter. Special attention is paid to the study of GVD with second and third order dispersion contribution as well as the filter characteristics and delay response of the grating. In case of strong grating, we find that at a particular grating strength the resonance band splits into two bands. Negative group delay for certain values of coupling strength suggested that an LPFG can also be used as dispersion compensator in optical fiber communication

Design of High Gain Novel Dielectric Resonator Antenna Array for 24 GHz Short Range Radar Systems

in this work we present a 16x1 array’ elements of a high gain Novel shape designed Dielectric Resonator Antenna (NDRA), having a low dielectric constant value of 18, for wide band (WB) and narow band (NB) 24 GHz automotive Short Range Radar (SRR) applications. The proposed NDRA array is feed by an efficient microstrip network feeding mechanism and presents wide impedance bandwidth (426 MHz), high gain (20.9 dBi), high efficiency (96%) and directional radiation pattern at 24 GHz with narrow angular beam-width of 6.4°. Computed NDRA array results allow the proposed design to be practical for the next automotive radar generations. Parametric studies have been analyzed using the Finite Difference Time Domain (FDTD) method of the CST-MW time domain solver and results, of the optimal structure, have been validated by the Finite Element Method (FEM) used in HFSS electromagnetic (EM) simulator

Design of Non-Uniformly Spaced Circular Arrays of Parasitic Dipoles for Lower Side Lobe Level with Maximum Directivity

This paper presents a new approach for circular array of parasitic dipoles composed by one active dipole for reduction of side lobe level with maximum directivity including mutual coupling. The desired goal is obtained by changing the spacing between the parasitic elements and length of the parasitic elements while the position and length of driven element is fixed. In addition to it, reflection coefficient (RC) of the driven element is kept closer to the specified value. Matlab based method of moment code is used to evaluate the performance of circular antenna designs generated by QPSO algorithm. Two examples are presented to show the effectiveness of this proposed approach. &nbsp

Probabilistic Assessment of Lightning Related Risk of Transmission Lines Based on Frequency Dependent Modeling of Tower-Footing Grounding System

This paper presents a probabilistic evaluation, based on Monte-Carlo method, for the estimation of insulation risk of failure of overhead transmission lines (TLs). The proposed method takes into account the wide-band model of tower-footing grounding system. The wide-band model of grounding system in frequency domain is obtained by the method of moment solution to the governing electrical field integral equations. The electrical parameters of soil are considered to be either constant or frequency dependent. The time-domain representation of the grounding system is inferred through pole-zero characterization of its associated frequency response. The case of a typical 400-kV transmission line is modelled in EMTP_RV with the tower-footing grounding system integrated with the transmission line (TL) system. The results of the paper show that the failure risk of transmission lines is affected by the grounding system model. This effect is more pronounced when the soil electrical parameters are assumed to be frequency dependent

Statistical Moments and Scintillation Level of Scattered Electromagnetic Waves in the Magnetized plasma

Statistical characteristics of scattered ordinary and extraordinary electromagnetic waves in the magnetized plasma are considered using the smooth perturbation method. Diffraction effects and polarization coefficients are taken into account. Second order statistical moments of scattered radiation are obtained for arbitrary correlation function of electron density fluctuations. Broadening of the spatial power spectrum and displacement of its maximum, wave phase structure function and the angle-of-arrivals are obtained for three-dimensional spectral function containing anisotropic Gaussian and power-law spectral functions. Scintillation level of scattered radiation is analyzed for different parameters characterizing anisotropic plasma irregularities for the ionospheric F-region. The spectral widths (first and second moments) of the power spectrum and scintillation periods are calculated for “frozen-in” drifting elongated plasma irregularities using the experimental data

SAR Evaluation of Metallic Loop-like Accessory Effect of Broadband Wearable Planar Monopole Textile Antenna

This paper presents the investigation influence of the common metallic loop like accessory on Specific Absorption Rate (SAR) averaged over 10g and 1 g tissue.The simulations were made by means CST Microwave Studio software at frequencies 2.45GHz and 2.6GHz. Numerical analysis conducted using broadband textile monopole antenna (TM) with variations of orientation and distance showed that the SAR value increased when the antenna horizontally polarized.This is up to 80% more than vertically polarized TM placed closest item to 2mm

Multi-port Pattern diversity antenna for K and Ka-band application

A compact coplanar waveguide (CPW) fed reconfigurable antenna with pattern diversity using multi-port excitation is designed. The basic antenna consists of a circular patch of radius 2.5mm which is fed by four ports independently. By exciting the patch with each individual port, the direction of the radiation pattern changes by 900. With the use of CPW feed technique, a very wide impedance bandwidth of around 12GHz (21.65 – 33.87 GHz) covering the K-band and Ka-band is achieved. The proposed antenna can be used for different satellite communication applications like earth exploration, radio navigation and location, mobile satellite communications which comes under K-band and Ka-band. The measured return loss and pattern characteristic results are in good agreement with simulated ones

A Triple-band Suspended Microstrip Antenna with Symmetrical USlots for WLAN/WiMax Applications

In this study, a triple-band suspended microstrip antenna with symmetrical U-slots is proposed for modern wireless communication systems. The antenna is specifically designed to acquire application in WLAN and WiMAX communication. Symmetrical U-slots in the radiator patch increase the number of resonances and improve the gain response. An appropriate air height was maintained between the ground plane and the radiator patch layer for improving bandwidth operation. The impedance characteristics of the antenna are enhanced using probe feeding techniques. The proposed compact antenna is designed on a single dielectric substrate of (30×25×1.56) mm3 . Parametric analysis of the proposed structure has been realized using IE3D software. This prototype exhibits maximum impedance bandwidth of 750 MHz and gain response of 7.28 dBi. The performance of the structure at three resonating bands i.e., at 3.3 GHz, 3.78 GHz and 5.3 GHz facilitate it to be applicable for WLAN/WiMAX systems

Jamming Efficacy of Variable Altitude GPS Jammer against Airborne GPS Receiver, Theoretical Study and Parametric Simulation

Satellite-based navigation systems, as one of the key infrastructure of development in manned and unmanned guidance systems, is vulnerable against the simplest form of attack in Electronic Warfare environments. This led us to investigate the described vulnerability of an airborne GPS receiver against jammers which are located at various altitude above the targeted point. To do that and to avoid encountering with unavailability of classified information about military-class missiles, some simplification was done and the problem was investigated in “Worst Case” conditions. Finally, the flight profile and radiation pattern of the antenna of the GPS receiver were theoretically modeled. Considering some assumptions, the other parameters were derived from them. At the end, a simulation software was developed and some results were extracted. The data was represented figuratively and the dependency of efficacy of jamming operation to the jammer’s altitude and flight profile of the missile were discussed

A Triband Planar Inverted-F Antenna with Quadratic Koch Fractal Shaped Slit Along with a Shorted Parasitic Strip

In this paper, a novel compact tri-band planar inverted-F antenna (PIFA) for mobile communication application is proposed. The antenna is capable to cover GSM 900 MHz, DCS 1.8 GHz and WLAN (IEEE 802.11b) 2.45 GHz bands. The proposed PIFA is composed of a quadratic Koch shape slit and a parasitic strip. The PIFA with the fractal shaped slit contributes to the first and second resonance while the shorted strip brings forth the third band. The impedance bandwidths of 84 MHz, 132 MHz and 81 MHz for GSM 900, DCS 1800 and WLAN (IEEE 802.11b) 2450, respectively are achieved. A realized gain of 2.44 dBi, 4.48 dBi and 3.86 dBi is obtained at 0.9 GHz, 1.8 GHz and 2.45 GHz, respectively. The proposed antenna is fabricated and |S11| dB is measured. Reasonable agreement between simulated results as well as measured results is obtained