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Design and Fabrication of Multi-finger Field Plate for Enhancement of AlGaN/GaN HEMT Breakdown Voltage
Get PDFThe design and fabrication of gate/source connected multi-finger field plate structures using TCAD ATLAS simulation software is presented. The designed field plate structures are fabricated on indigenous AlGaN/GaN HEMT devices. AlGaN/GaN HEMT devices with field plate structures exhibit about three times improvement in breakdown voltage of device and are in close agreement with the simulation results. Integration of field plates in device have resulted in higher VDS (drain to source voltage) operation and improvement in output power of AlGaN/GaN HEMT devices. Incorporation of field plates also decrease the reverse leakage current of HEMT devices
Bandwidth Enhancement of Substrate Integrated Waveguide Cavity-backed Bow-tie-complementary-ring-slot Antenna using a Shorted-via
Get PDFIn this study, a planar cavity-backed bow-tie-complementary-ring-slot antenna is proposed, and a new approach for bandwidth enhancement using a shorted-via is introduced. A shorted-via concept overcomes the narrow impedance bandwidth of a conventional substrate integrated waveguide cavity-backed antenna. By adjusting the location of the shorted-via (placed just above the centroid of the radiating slot), the individual bandwidth of the lower and higher order resonances has been tuned below -10 dB criterion, which results in the broadening of the bandwidth. Finally, the antenna is proficient to operate for an impedance bandwidth of 15.71 per cent, ranging from 12.02~14.07 GHz. The proposed antenna shows a gain of better than 4 dBi within the operating band with less than 0.5 dBi variation. Moreover, the antenna preserves good radiation characteristics, which is similar to that of the conventional metallic counterpart. To validate the simulated results, an antenna is fabricated and tested. The simulated results in terms of the reflection coefficient, gain, and radiation patterns are in good agreement with the measured results
A Motif-based Mission Planning Method for UAV Swarms Considering Dynamic Reconfiguration
Get PDFInfluenced by complex terrain conditions of combat environments and constrained by the level of communication technology, communication among unmanned aerial vehicles (UAV) is greatly restricted. In light of this situation, mission planning for UAV swarms under limited communication has become a difficult problem. This paper introduces motifs as the basic unit of configuration and proposes a motif-based mission planning method considering dynamic reconfiguration. This method uses multidimensional dynamic list scheduling algorithm to generate a mission planning scheme based on the motif-based swarm configuration solution. Then it incorporates order preserved operators with NSGA-III algorithm to find Pareto front solutions of all possible mission planning schemes. The feasibility of this mission planning method is validated through a case study
Development of a Full Mission Simulator for Pilot Training of Fighter Aircraft
Get PDFWith aircraft becoming more complex and avionics intensive and flight being almost autonomous based on waypoint navigation, software and displays becoming a significant component of the all glass cockpit of the modern day fighter aircraft, it is imperative that pilots are trained on missions using ground based full mission simulator (FMS) for routine flight as well as advanced missions. A flight simulator is as good as the real system only when it is able to mimic the physical system, both in terms of dynamics and layout so that the pilot gets the complete feel of the environment as encountered during actual sortie. The objective of this research paper is to provide a detailed insight into the various aspects of development of a FMS for pilot training with minimal maintenance operations for long hours of realistic flight training on ground. The approach followed by ADE in developing a FMS using a healthy mix of conventional flight simulation methodologies and novel approaches for various simulator sub-systems to tailor and meet the specific training needs, one presented. The FMS developed by ADE is presently being used by Indian Air Force for flight and mission critical training of squadron pilots
Countering UAVs – the Mover of Research in Military Technology
Get PDFUnmanned aerial vehicles (UAVs) are massively seeping into a wide range of human activities. Along with other remotely controlled or automatic devices, they have entered many aspects of human activities and industry. While the majority of researchers have been working on the construction, deployment and non-military use of UAVs, the protection against UAVs remained on the edge of their interest. Nowadays, the situation is rapidly changing. The risk of misuse of UAVs by criminals, guerrillas or terrorists has compelled authorities, scientists and defence industry to face this threat. Organisations have launched crucial infrastructure defence programs to cope with UAV threat. To solve this problem, it is necessary to develop disciplines improving the air space surveillance and UAVs elimination techniques. The substantial aspects of the UAVs detection and elimination were analysed, being supported by a number of conferences, workshops and journals articles. The contribution of the study in the Counter–UAV area consists particularly in generalisation and evaluation of the main technical issues. The aim of this paper is to emphasise the importance of developing new scientific fields for countering UAVs, and hence it is directed firstly on the scientific audience
Internet of Things Controlled Reconfigurable Antenna for RF Harvesting
Get PDFInternet of Things (IoT) controlled a reconfigurable antenna with PIN diode switch for modern wireless communication is designed and implemented. Direct contact of biasing network with the antenna is eliminated and the switching unit is manipulated through IoT method. The proposed antenna has ring structures, in which the outer ring connects the inner ring structure through a PIN diode switch. The dimension of the proposed antenna is reported as 50 mm × 50 mm and its prototype has been made-up on epoxy-Fr4 substrate with 1.6 mm thickness. This antenna setup is made to reconfigurable in four bands (4.5 GHz, 3.5 GHz, 2.4 GHz, and 1.8 GHz) through switching provided by IoT device (NodeMCU). The antenna has a good return loss greater than -10dB.In switching state 2 the antenna has a return loss of -30 dB peak is attained at 3.4 GHz of operating frequency. Similarly the gain response of antenna is good in its operating bands of all switching states and obtained a maximum gain of 2.7 dB in 3.5 GHz. Bidirectional radiation pattern is obtained in all switching states of the antenna
Experimental and Numerical Investigation of Engine Foundation for Vibration Reduction
Get PDFThe purpose of this study is to minimise frequency response of engine foundation using topology optimisation. The study involves vibration response estimation of an existing marine engine foundation, validation of estimations with measurements and estimation of reduction in vibration response after optimisation. Initially, solid model of baseline model is generated using dimensions of the existing foundation measured by a laser line probe coordinate measuring machine. Harmonic analysis is used to find the vibration response of the foundation. These results are experimentally validated by the measurements on the foundation using the vibration testing. Frequency response topology optimisation is then carried out on the baseline model to reduce vibration response with specified constraints and objective function. Subsequently, harmonic analysis is performed on the topology optimised design to verify the reduction in vibration response. From these results, it is observed that considerable frequency response is reduced with modified design compared to baseline model
Relay based Coupling Scheme of High Speed Communication data, High voltage DC And High Power Pulsed AC for Coaxial Cable
Get PDFCoaxial cable telemetry is most commonly used in the field of underwater applications like data logging in oil rigs, underwater wireless modem, underwater acoustic measurements, borehole measurements, deep sea telemetry for sediment analysis, airborne sonars, imaging sonars etc. In all the above applications coaxial multicore cables are used. The design and development of relay based coupling scheme which helps to replace the multi core cable with a single core coaxial cable for telemetry application is described. Single core cable is suitable for long distance data communication. Multi core cables are generally heavy and due to the size, may not meet space constraints in complex systems. They are not economical too. The relay based coupling scheme is used to mix or separate the high speed bi-directional communication data, high voltage DC and high power pulsed AC. In single relay scheme one relay is used to switch the centre core of single core coaxial cable. Here the ground is common for both high power AC transmission and high speed bi-directional data path. A dual relay scheme is discussed where two relays are used to switch both the centre core and ground of the single core coaxial cable. This provides more ground isolation and can avoid ground lifting issues while high power AC transmission occurs. The simulation of the coupling scheme was done using PSpice®. A prototype of the coupling scheme was also made for analysis. Filter responses were analysed for each coupling path. The DC coupling filter has 85 Hz cut-off frequency at -3 dB. The cut-off frequency of high speed data coupler is 500 KHz at -3 dB. A 4.3KV peak to peak of 3 KHz and 7 KHz AC signals were transmitted and measurements were taken to analyse the effect of high voltage over different coupling paths. The 3 KHz signal has a peak of 61.88 dB and that of 7 KHz signal, the peak is 62.50 dB. The signal components of 3 KHz signal in the DC path has a voltage level of 9.375 dB and that of 7 KHz signal is 25.63 dB
Application of Water Cumulative Charges as a Water Spouts for Intensive Flame Extinguishing
Get PDFShape cumulative charge is a set of explosive components that uses directional energy accumulation. The water cumulative charges are filled with water, which forms a water-directed beam that has the ability to effectively counteract the intense flame that is induced by gaseous flammable gas or liquid from the damaged gas duct and extinguishes it. Study contains description of the experimentally constructed cumulative charge as well as the analysis of results of experiments carried out in real conditions. Based on the facts gained from the experiments we can conclude that the cumulative water charge has a significant potential and possibilities to extinguish an intense flame