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A Compact Reconfigurable Multi-mode Resonator-based Multi-band Band Pass Filter for Intelligent Transportation Systems Applications
Get PDFA compact wide band reconfigurable bandpass filter (BPF) which utilises a hemi-circular flower shaped multimode resonator (MMR) is presented. The proposed MMR provides three resonant modes which fall within the broad frequency spectra. Among these, two modes are even and one is odd. These modes are optimised by varying the dimensions so as to obtain the desired frequency response. The fractional bandwidth is more than 96 per cent. The filter can be operated as multi-band BPF. In OFF condition of ‘Pin’ diode, the centre frequencies are 2.43 GHz, 3.5 GHz, and 5.9 GHz in ON condition of ‘Pin’ diode centre frequencies are 2.43 GHz, 3.5 GHz, 5.9 GHz, 6.5 GHz, and 8.8 GHz which are used for vehicular, WiMAX, intelligent transportation systems and satellite communication respectively. Microstrip filter structures are integrated with ‘Pin’ diodes. Appropriate biasing has been provided by choosing lumped components with precise values. The insertion loss in OFF condition are 0.5 dB, 0.67 dB, and 0.8 dB and in ON condition 0.5 dB, 0.7 dB, 1.2 dB, and 1.9 dB. The measured results agree well with the full-wave simulated results
Study of Wavefront Tilt Variance with Various Telescope Apertures in Indoor Convective Turbulence
Get PDFTurbulent atmosphere produces random wavefront tilt in the propagating laser beam and the dynamics of turbulence is largely depend on the receiving optics aperture size. In this paper, wavefront tilt variance is studied with various telescope aperture sizes in indoor convective turbulence. A simple experimental setup is described for simulating the near ground atmospheric turbulence by generating different strengths of convective turbulence in the laboratory. A laser beam is made to propagate through the turbulence subsequently induced wavefront tilt variances are experimentally measured and analyzed statistically. The wavefront tilt variance is used to estimate the temporal characteristics using Fourier transform by varying aperture sizes and turbulence strengths (i.e. ambient, weak and moderate). The Hurst exponent, the Fried parameter and the wavefront tilt frequencies for the different turbulence strengths are calculated. The power dependence of the wavefront tilt variance on the telescope aperture size is studied and a deviation from the classical D-1/3 dependence is reported
Comfort Level Refinement of Military Tracked Vehicle Crew through Optimal Control Study
Get PDFMilitary tracked vehicle and crew are modelled together in this paper as integrated man-machine lumped parameter model, by integrating the simplified 5 degrees of freedom (DoF) tracked vehicle model, including seat and 4 DoF human bio-dynamic model, thus resulting in a 9 DoF simplified vehicle-occupant model. Then the natural frequency of major mass segment namely the chassis mass is obtained through simulation study, for a known road input. The value obtained is compared with that of an earlier research work, for validation of said man-machine model. Then focusing our study locally at crew seat location, parameters of crew seat suspension for ride comfort are optimised using the optimal digital state space controller designed for this purpose by implementing it in a 2 DoF occupant - seat suspension model and its Simulink model constructed. Simulation results illustrate the attainment of the goal by meeting the controller design requirements
Range Performance Modelling of Thermal Imaging System based on Single Parameter Characterised by Ambient Temperature and Relative Humidity
Get PDFRange performance of a thermal imaging system is characterised by the prevailing atmospheric condition present at that time. There are two dominant parameters that limit the range performance of any thermal imaging systems i.e. ambient temperature and relative humidity. In the present work, comparative study of acquisition range performance of thermal imaging system operating in LWIR and MWIR spectral bands has been presented as a function of absolute humidity (AH) which is responsible for attenuation of IR radiation due to water vapour molecules present in path length. Presentation of acquisition range as function of AH leads to a single range performance table/graph for thermal imaging system under consideration for predefined visibility (V), target size, ambient temperature (T), target to background temperature difference (ΔT) and relative humidity (RH). This table/graph can be used to predict detection, recognition and identification ranges for any set of combination of air temperature (T) and relative humidity (RH). The approach presented in this paper is versatile and has been illustrated through comparative performance analysis of LWIR and MWIR thermal imaging systems based on 640X512 staring focal plane array (FPA) having identical design parameters in terms of resolution (IFOV). It has been shown that MWIR performance is superior to LWIR beyond a crossover value of AH(T) even though MRTD of MWIR sensor is inferior to that of LWIR sensor at all spatial frequencies. Study has been carried out both for clear atmosphere and hazy conditions
A Hybrid Approach to Cognition in Radars
Get PDFIn many engineering domains, cognition is emerging to play vital role. Cognition will play crucial role in radar engineering as well for the development of next generation radars. In this paper, a cognitive architecture for radars is introduced, based on hybrid cognitive architectures. The paper proposes deep learning applications for integrated target classification based on high-resolution radar range profile measurements and target revisit time calculation as case studies. The proposed architecture is based on the artificial cognitive systems concepts and provides a basis for addressing cognition in radars, which is inadequately explored for radar systems. Initial experimental studies on the applicability of deep learning techniques under this approach provided promising results
Spectroscopic Evaluation of Optical Parameters of a Transition Metal Salt Filled Polymer Material
Get PDFTransition metal salt, manganese chloride was incorporated into polyvinyl alcohol (PVA) to prepare metal salt filled polymer material (M-PVA) and their optical properties were evaluated. XRD, UV-vis, and FTIR analyses reveal that there is strong interaction between PVA and the manganese chloride salt. From XRD analysis, the inter-chain separation in pristine PVA and M-PVA was found to be 5.62 Ǻ and 4.70 Ǻ, respectively; thus indicating that the packing of polymer chains is more compact under the influence of manganese chloride. Optical band gap of PVA was found as 5.06 eV but such band gap was reduced on incorporation of manganese chloride into the PVA matrix system with corresponding increase in optical conductivity. Spectral evaluation indicates that refractive index of M-PVA decreases faster than that of PVA in the visible range. Abbe Number was found to have decreased on incorporation of manganese chloride into the PVA matrix system indicating increase in optical dispersion in conformity with the trend of increase in dispersion energy (Ed). The average interband oscillator wavelength was found close to the respective values of absorption edges
Analysis and Parameter Identification of Automatic Cannon Carriages
Get PDFExperimental procedures for the research of vibrations in automatic weapons mounted on combat vehicles is introduced. Experiment preparation procedures, experience and examples of evaluation of measured results in direct fire from a tracked combat vehicle are explained on BMP-2 IFV example. The result is the movements of the turret and the hull of a combat vehicle in single shot firing, and short and long burst firing. In addition to time domain analysis, methods of correlation and spectral analysis are used. Live firing experiments are complemented by laboratory experiments and are used to determine model parameters for calculations such as stiffness and damping in the suspensions of the hull, elevation parts, clearance in the elevating gear, and the natural vibration frequency of the hull and elevation parts
Robust Stabilised Visual Tracker for Vehicle Tracking
Get PDFVisual tracking is performed in a stabilised video. If the input video to the tracker algorithm is itself destabilised, incorrect motion vectors will cause a serious drift in tracking. Therefore video stabilisation is must before tracking. A novel algorithm is developed which simultaneously takes care of video stabilisation and target tracking. Target templates in just previous frame are stored in positive and negative repositories followed by Affine mapping. Then optimised affine parameters are used to stabilise the video. Target of interest in the next frame is approximated using linear combinations of previous target templates. Proposed modified L1 minimisation method is used to solve sparse representation of target in the target template subspace. Occlusion problem is minimised using the inherent energy of coefficients. Accurate tracking results have been obtained in destabilised videos
Frustum Shaped Conformal Antenna for Spinning Aerial Platform
Get PDFA novel approach to design and develop frustum shaped conformal antenna for transmission of telemetry data from a missile like spinning aerial platform is described. The requirement necessitates for an omni directional radiation pattern in the roll plane. However, the criteria is not feasible to achieve by using a monopole or a dipole as the omni coverage due to these antennas are restricted only in yaw or azimuth plane of the aerial platform. A conformal antenna appropriately wrapped on to the surface provides potential solution and accordingly has been configured for meeting the requirements of a practical application. The antenna artwork has been designed to conform to the exterior geometry of the intended portion of conical surface and printed on a microwave substrate which is essentially thin and flexible. A corporate feed distribution scheme has been designed and tailored to match with the impedance of the microstrip radiator at multiple locations and also printed along with it making the frustum antenna very compact and of aerodynamic supportive form. The antenna produces required omni coverage in the plane normal to the roll axis. A step-wise method for the design and development of the frustum conformal antenna through simulation and experiment approach has been discussed
Effect of Yttrium Oxide Dispersion on the Microstructure and Properties of Tungsten Heavy Alloys
Get PDFTungsten heavy alloys are considered as two phase composites with 88 to 97 wt% tungsten interspersed in a matrix of relatively low melting elements such as nickel, iron and cobalt. The mechanical properties of these alloys are greatly influenced by the microstructural features such as tungsten grain size, tungsten-tungsten contiguity and matrix volume fraction. Oxide dispersion strengthening (ODS), refinement of tungsten grain size, cyclic heat treatment, addition of alloying elements like Cr, Mo, and Co are some of the methods investigated to improve the microstructural features and thereby the mechanical properties of tungsten heavy alloys. Among these methods ODS has been considered as a promising processing technique since the tungsten grain size observed in ODS alloys is finer compared to the conventional alloys and more importantly the dynamic fracture mode changes from adiabatic shear band to brittle fracture. The present study is mainly focused on investigating the effect of 0.3 wt% yttrium oxide (Y2O3) dispersion on the microstructure and consequently the tensile properties of 90W-6Ni-2Fe-2Co alloy. With 0.3 wt%Y2O3, the ODS alloy (89.7W-6Ni-2Fe-2Co-0.3Y2O3) is processed by two-stage sintering with subsequent thermo-mechanical treatment which includes vacuum heat treatment and swaging. ODS alloy and the conventional alloy (without oxides) are compared based on the microstructures and tensile properties obtained after liquid phase sintering and after final processing