By Teresa Crompton
Hasan Mir, Associate Professor in the Department of Electrical Engineering, CEN, was awarded a Faculty Research Travel Grant in 2012.
How did you use the grant?
The funds were used for a collaborative visit with Dr. Kainam Wong at the Hong Kong Polytechnic University (HKPU). Dr. Wong is a recognized authority in many areas related to ISR (Information, Surveillance and Reconnaissance) technology. Prior to joining AUS, I was with MIT Lincoln Laboratory, where I researched a variety of aspects related to radar technology.
What was the goal of the project?
The goal of this project was to further research in high-performance radar applications. This includes the problem of how to schedule tasks in a multifunction radar in a limited time horizon, as well as alternative high-resolution radar processing paradigms.
How did the grant aid your research?
I very much appreciate the support of the Office of Research and Graduate Studies (ORGS), since the Faculty Research (FRG3) grant has been instrumental in allowing me to maintain a research thrust in modern radar technology. As with my previous FRG3 funded visit (from which three IEEE Transaction publications were generated), this subsequent visit was also immensely beneficial, and has again resulted in several publications related to radar technology. These were:
1) H. Mir and A. Guitouni, “Variable Dwell Time Task Scheduling for Multifunction Radar,” accepted in IEEE Transactions on Automation Science and Engineering.
2) H. Mir and K. Wong, “A Low-Rate Sampling Technique for Range-Windowed Radar/Sonar Using Nonlinear Frequency Modulation,” accepted in IEEE Transactions on Aerospace and Electronic Systems.
The first article benefited from Dr. Wong’s mathematical expertise along with the usage of optimization software in his laboratory that was needed to complete simulation studies. The second article was based on his suggestion of investigating non-linear modulation schemes that allow for reduced sampling rates while maintaining low-sidelobes without the need for tapering (and hence preserving resolution). Another paper directly resulting from the collaboration is currently under preparation. Additionally, the ideas gained from the visit have been used to assist a Masters student in his related work, and will also help in the preparation of a grant submission to the ICT Fund.
What were your main findings?
In many surveillance related applications, only a particular range window may be of interest. For instance, in target identification, only a narrow range window commensurate with the physical size of the target needs to be examined. In order to obtain high resolution range profiles, it is required that the illuminating signal should have an extremely wide bandwidth. This poses technical challenges with the digital receiver, since the time-sampling must be carried out at a very high rate. To circumvent this problem, linear frequency modulated waveforms are often used for transmission. However, linear frequency modulation suffers from the drawback of relatively high range sidelobe levels, which are undesirable as they could be mistaken for a target, or could result in a weak target being obscured by a stronger target.
The standard approach to dealing with elevated range sidelobe levels is to use tapering, which has several objectionable side-effects. We developed a generalized radar processing architecture that is capable of exploiting the much wider class of nonlinear frequency modulated waveforms. This new architecture significantly reduces the time-sampling rate, while lowering the range sidelobes without the need for tapering. For example, we demonstrated that our processing architecture can reduce the conventional sampling rate by a factor of five while simultaneously reducing the range sidelobes from the conventional -13 dB to -40 dB.
Hong Kong Polytechnic University (red buildings).
Did anything surprise you?
A previous radar hardware-related research project I was involved with at AUS progressed very rapidly thanks to the heavy contribution and involvement of my brilliant colleague, Dr. Lutfi Albasha. Similarly, I was able to leverage the expertise of Dr. Wong during my visit with him to quickly develop various aspects of our proposed processing architecture. In both cases, I was pleasantly surprised at the speed with which we were able to make progress.
What are your future research plans?
In the short term, a more in-depth analysis to characterize the behavior and performance of our proposed processing architecture should be performed. This will greatly assist my long-term goal of implementing this scheme on a testbed platform.
Teresa Compton is a Grants Writer at the Office of Research and Graduate Studies at American University of Sharjah.