Graceful Degradation An Airborne Surveillance Radar Perspective

  • Rajesh Ramachandran DRDO-Centre for Airborne Systems, Bengaluru - 560 037
  • Reena Sharma DRDO-Centre for Airborne Systems, Bengaluru - 560 037
  • Suma Varughese DRDO-Centre for Airborne Systems, Bengaluru - 560 037
Keywords: Graceful degradation, AESA, TR module, Random failure, SINR loss


Active electronically scanned antenna (AESA)-based radars imbibe the desirable feature of ‘graceful degradation’. Such radars use miniaturised transmit-receive (TR) modules and a failure of few modules does not lead to failure of the mission. For example, in AESA-based ground MTI radar, failure of a few modules does not affect the array performance. In such a case, the static ground clutter is centred on zero frequency does not have a motion dependent Doppler spread. However, in airborne AESA radars, the ground clutter has an angle dependent Doppler frequency due to the platform motion and clutter leaking in through antenna side-lobes. Hence, the antenna side lobe levels dictate the side lobe clutter against which target detection is to be performed. The detection performance is governed by the signal to interference plus noise ratio (SINR). For Airborne surveillance radar the effect of random and systematic failures of TR modules and their effect on SINR is characterised. It is shown that single channel processing does not effectively provide the graceful degradation feature as the SINR loss due to failures is significant. However, the effect of systematic failure on SINR loss is less as compared to random failures. An effective scheme for feeding the array is also proposed.

Author Biographies

Rajesh Ramachandran, DRDO-Centre for Airborne Systems, Bengaluru - 560 037

Dr R. Rajesh, Scientist ‘E’, received his BTech in ECE from National Institute of Technology, Calicut, India in 2002 and PhD from Electrical Communication Engineering department, Indian Institute of Science, Bangalore, India in 2009. Since December 2002, he is working as a Scientist with Centre for Airborne Systems, DRDO, Bangalore, India. His areas of interest include Information Theory, Wireless Communication, Radar Systems and System Engineering. He is a recipient of Laboratory Scientist of the year award in 2006, DRDO Young Scientist award in 2008 and Technology group award in 2013 and 2018. 

His contribution in this paper includes conceptualisation of the problem, mathematical formulation, analysis, simulation and preparation of the manuscript.

Reena Sharma, DRDO-Centre for Airborne Systems, Bengaluru - 560 037

Dr Reena Sharma, Scientist ‘G’, received her MTech in radar and communication from IIT Delhi and PhD in Microwave Engineering from Indian Institute of Science in 1997. She was a post doctoral fellow at Helsinki University of Technology (HUT), Finland during 1999-2000. Since 2000 she is working with Centre for Airborne Systems, DRDO, Bangalore, where she is heading airborne system projects. Her areas of interest include Electromagnetics, Chiral Materials, System Simulation for airborne surveillance and System Engineering. She is recipient of Laboratory Scientist of the year award for year 2011 and Technology group award in 2013. 

Her contributions in this paper include the overall architecture, guidance in the preparation of manuscript and in revision of the paper.

Suma Varughese, DRDO-Centre for Airborne Systems, Bengaluru - 560 037

Ms Suma Varughese, Scientist ‘H’, received her MSc (Comp. Sci.) in 1988 and MS (Engg) on Antenna measurement techniques from Institute of Science, Bangalore. She joined LRDE, DRDO in 1989. She moved to CABS, DRDO, Bangalore to join a prestigious airborne programme in 2004. She currently is an outstanding scientist at CABS heading various airborne system projects. Her areas of interest include active array antennas, antenna measurement techniques, multi-sensor data fusion and system engineering. She is a recipient of IETE J C Bose gold medal for best paper in 1993, NRDC national award for PNFM software in 1995, IETE NM Saha best paper award in 2013 and DRDO Agni award in 2013. 

Her contributions in this paper include the overall architecture, guidance in the preparation of manuscript and in revision of the paper.


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How to Cite
Ramachandran, R., Sharma, R., & Varughese, S. (2019). Graceful Degradation An Airborne Surveillance Radar Perspective. Defence Science Journal, 69(4), 389-395.
Electronics & Communication Systems

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