Browsing by Author "Vagias, Ioannis"

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    A game of hide and seek
    (Trident Publications Limited, 2016-03-01) Vagias, Ioannis
    Anti-ship missiles have evolved more rapidly than most navies’ electronic warfare and ship protection systems, which gives vessels very little time to respond in the event of an attack. Remaining undetected against a more complex threat requires electronic warfare systems with the capability to detect, recognise, identify and assess low-power, wideband emissions.
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    Impact of channel number on architecture and performance of advanced processing techniques for highly channelised multichannel systems
    (2020-07) McKelvey, Anthony Martin; Vagias, Ioannis; Richardson, Mark A.; May, Andrew
    The effect of varying the number of digitised channels on a radar systems performance is analysed through modelling several spatial processing techniques and determining the effect of varying design. Performance is measured using several metrics with scan rate, minimum detectable velocity, and robustness to jamming being key. Modelling is carried out for a number of different operational scenarios and channel architectures. Through this modelling effort the effects of varying channel number on performance in different operational environments is determined. These outputs are weighed against limitations introduced by increasing channel number (e.g. increased computational complexity). These results are used to form conclusion on what number of channels provides the best overall performance gain. In the case of the radar system model in this thesis N=32 and N=16 channels have been determined to offer the best performance whilst minimising limiting factors.
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    A trade-off analysis between lateral/directional stability and radar cross section requirements of an air-to-air combat airframe
    (Elsevier, 2023-05-09) Bacci, David; Vagias, Ioannis
    Numerical aerodynamic and radar analyses were conducted on 3 low-radar cross-section airframes, derived from the AVT-183 diamond wing. The geometries were developed by adding different configurations of vertical stabilators, to improve lateral and directional characteristics at high angles of attack whilst minimising the deterioration of radar signature characteristics. The analyses were conducted at a Mach number of 0.30, with angle of attack varying between 0 deg to 30 deg and angle of sideslip varying from 0 deg to 6 deg. Monostatic radar cross-section analysis was conducted in L and X bands. The study explored the trade-off between radar signature control (RCS) and the spin/departure requirements typical of a modern combat aircraft designed for air-superiority. Several of the proposed configuration were shown to improve both lateral and directional stability, whilst maintaining acceptable RCS.
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    UAV Susceptibility and self-protection measures
    (Cranfield University, 2016-12-15 09:59) Vagias, Ioannis
    Poster presentation at the 2016 Defence and Security Doctoral Symposium. The use of Unmanned Aerial Vehicles (UAV) has proliferated in the defence, security and scientific communities. Although still immature, the UAV market is the fastest growing sector of the defence industry, as senior and junior tactical military commanders request frequently both Intelligence Surveillance and Reconnaissance (ISR) and Close Air Support from unmanned aerial platforms. This increased dependence on UAVs, the associated attrition rate due to hostile fire and the high cost of sensors, communication equipment and weaponry will drive the requirement for UAV survivability. There is a need to develop background on the potential for UAVs to be equipped with self-protection systems. The aims of the research are to:· Investigate the threats to High and Medium Altitude Long Endurance (HALE and ALE) UAS and the spectrum, under which they operate.· Study where such protection systems can be installed and under which restrictions.·  Research payload capability, dispenser installation as well as countermeasure ejection geometry, to understand how the UAS can be better asked.· Run simulation of individual and sophisticated scenarios where UAS will employ self-protection dispensing and non-dispensing techniques against threats. · Extract practical and feasible techniques for UAS protection.