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Balasubramanian U.,Aeronautical Development Agency ADA | Pacharne P.R.,Indian Defence Institute of Advanced Technology | Radhakrishna P.,Indian Defence Institute of Advanced Technology | Naik K.K.,Indian Defence Institute of Advanced Technology | Bhattacharya C.,Indian Defence Institute of Advanced Technology
Proceedings of the 2012 International Conference on Communications, Devices and Intelligent Systems, CODIS 2012

Bandwidth restrictions for flight test operations have led the designers world over to graduate from analog telemetry schemes to more compact digital telemetry schemes. Proper precoding and pulse shaping of non-return to zero (NRZ) waveforms are necessary prior to digital modulation for limiting the bandwidth of power spectrum of the NRZ pulses. The most common pulse shapes used are Gaussian filter for Gaussian minimum shift keying (GMSK), raised cosine filters, etc. Recently shaped offset quadrature phase shift keying (SOQPSK) is introduced as a bandwidth efficient modulation technique. In this paper, we report the bandwidth efficiency of SOQPSK for S-band airborne data links working at 4 Mbps rate [1]. Our results show that the SOQPSK-TG is the more bandwidth efficient modulation scheme than GMSK for telemetry applications. © 2012 IEEE. Source

Vasantharaju C.,Hindustan Aeronautics Ltd HAL | Ashok B.,Aeronautical Development Agency ADA | Naiju C.D.,Vellore Institute of Technology
International Journal of Product Lifecycle Management

To enhance performance effectiveness, the design of aircraft system and components must incorporate the radical technologies in all specialisations. As the technology advances, the corresponding complexity also advances. Hence, there is a need to design the aircraft systems and subsystems with components in such a manner to accommodate futuristic technologies and compress the design cycle times. In the present scenario, the aircraft parts are complex and have high interdependencies which make it difficult to identify and incorporate the technological advances in scheduled time line. Different management and model-based techniques such as PERT, CPM, multi-disciplinary optimisation (MDO), FEM, etc., were used for cycle time reduction. Markov process is a stochastic approach which is explored for the objectives of knowing the strength and weakness of the organisation and to reach the futuristic goals with available resources, thereby anticipating the futuristic technological changes and trying to fulfil mission requirements at design stage itself. In this paper, Markov chain approach is illustrated for cycle time reduction with a typical case study for military aircraft sub assembly. Copyright © 2015 Inderscience Enterprises Ltd. Source

Vasantharaju C.,Hindustan Aeronautics Ltd HAL | Ashok B.,Aeronautical Development Agency ADA | Naiju C.D.,Vellore Institute of Technology
ARPN Journal of Engineering and Applied Sciences

The design of Aircraft and especially the fighter Aircraft is increasingly getting complex. Added to the complexities of the design and need to integrate several disciplines, there is an added challenge of working with technologies that are still in drawing boards to be incorporated in future design. Needless to add, validation and testing of entire system / subsystem is a pain point. Hence there is a clear need to design the aircraft in such a manner to accommodate for futuristic technologies and compress the design cycle times. On an average, design and development of a Military aircraft either for developed countries or developing countries requires a minimum of 13 years from the launch of project to the first flight. As the years get passed on new technologies and advancement also develops and it will become difficult to identify and incorporate to the ongoing projects. A novel approach of using Markov process for achieving these objectives is explored. Markov based approach as a stochastic approach normally used to predict future states on the basis they have no link to the past is explored. A step by step approach by taking a typical design life cycle process of a particular component/assembly of aircraft is discussed. In this, design is split in to sequential stages, based on our prior design experience a probability is assigned to all foreseeable possibilities, and then that is converted to transition probability. Using a simple concept that any probability less than 1.0 leads to extended design life cycle, suitable cost and time factors. © 2006-2014 Asian Research Publishing Network (ARPN). Source

Umashankar B.,Aeronautical Development Agency ADA | Aswathy S.,Aeronautical Development Agency ADA | Nishad F.,Aeronautical Development Agency ADA | Anantha K.P.,Aeronautical Development Agency ADA
Proceedings of the International Telemetering Conference

Typical aeronautical telemetry instrumentation for a fighter aircraft comprises of multiple antennas on the aircraft, with typical placement of one antenna on the spine of the aircraft and the other on the aircraft belly. Complimentary to the aircraft instrumentation, is the fixed ground station equipped with a tracking antenna. Air to ground channel for this telemetry link is considered as line of sight propagation. But there is a link loss observed at the ground station for a certain instant of time. Possible causes of link loss/attenuation in the case are due to aircraft manoeuvring. The main objective of this paper is to study and analyze masking patterns of the aircraft instrumentation scheme. Polarization diversity combining at the RF receiver and frequency diversity combining at the tracking receiver were explored at the ground station to mitigate the effect of RF fading due to antenna masking. The RF signal levels at the ground station are analyzed with respect to different aircraft attitudes. This paper also brings out the possible causes of the RF level drop and the solutions which can be explored to overcome it. Source

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