Invited Speakers
Dr. Goutam Chattopadhyay
''Terahertz Radar for Imaging Applications ''
About the Speaker:
Goutam Chattopadhyay (S’93-M’99-SM’01-F’11) is a Senior Research Scientist at the NASA’s Jet Propulsion Laboratory, California Institute of Technology, and a Visiting Associate at the Division of Physics, Mathematics, and Astronomy at the California Institute of Technology, Pasadena, USA. He received the B.E. degree in electronics and telecommunication engineering from the Bengal Engineering College, Calcutta University, Calcutta, India, in 1987, the M.S. degree in electrical engineering from the University of Virginia, Charlottesville, in 1994, and the Ph.D. degree in electrical engineering from the California Institute of Technology (Caltech), Pasadena, in 1999. From 1987 until 1992, he was a Design Engineer with the Tata Institute of Fundamental Research (TIFR), Pune, India.
His research interests include microwave, millimeter-, and submillimeter- wave heterodyne and direct detector receivers, frequency sources and mixers in the terahertz region, antennas, SIS mixer technology, direct detector bolometer instruments; InP HEMT amplifiers, mixers, and multipliers; high frequency radars, and applications of nanotechnology at terahertz frequencies. He has more than 200 publications in international journals and conferences and holds more than fifteen patents. Among various awards and honors, he was the recipient of the Best Undergraduate Student Award from the University of Calcutta in 1987, the Jawaharlal Nehru Fellowship Award from the Government of India in 1992, and the IEEE MTT-S Graduate Fellowship Award in 1997. He was the recipient of the best journal paper award in 2013 by IEEE Transactions on Terahertz Science and Technology, and IETE Prof. S. N. Mitra Memorial Award in 2014. He also received more than 30 NASA technical achievement and new technology invention awards. He is a Fellow of IEEE (USA) and IETE (India) and an IEEE Distinguished Lecturer.G
Abstract:
One terahertz system with a potentially vast application space is radar, where there is a striking lack of systems operating above W‐band (75‐100 GHz), until optical frequencies are reached in lidar instruments. This terahertz radar gap is therefore an opportunity for imaginative scientific, commercial, and security applications.
Terahertz radars have several benefits over either shorter or longer wave bands: The wavelengths in this regime are short enough to provide high resolution with modest apertures, yet long enough to penetrate clothing. Huge absolute bandwidths can be attained with small fractional‐bandwidth components, leading to ultrahigh‐range resolution radars. There is appreciable penetration below about 1 THz through certain optically opaque substances such as clothing, dust, fog, and rain. Very small changes in target velocity can be detected using Doppler radar techniques but not so small that simultaneous range measurements over useful distances are precluded. Compared to lower frequencies, distributed imaging targets are less specular, leading to softer geometrical fading effects that stealth technology relies on for concealment. At the same time, significant challenges of terahertz radars remain, including the following: There is a very limited number of suppliers for sources and detectors and they are very expensive. Higher component costs are also driven by the tighter mechanical tolerances needed for devices, waveguide structures, and antennas. Strong atmospheric attenuation occurs above 300 GHz and it increases very rapidly with frequency (except for some windows below 1 THz). And finally, terahertz radiation has no ability to penetrate thick objects such as walls or substances with appreciable water content, including biological tissues.
Several groups around the world are working on the development of terahertz imagers for various applications. One option is to use passive imaging techniques, which were very successful at millimeter‐wave frequencies, by scaling in frequencies to terahertz range. However, the background sky is much warmer at terahertz frequencies due to high atmospheric absorption. Since passive imagers detect small differences in temperatures from the radiating object against the sky background, at these frequencies the passive imagers do not provide enough scene contrast for short integration times. On the other hand, in an active imager, the object is illuminated with a terahertz source and the resulting reflected/scattered radiation is detected to make an image. However, the glint from the background clutter in an active terahertz imager makes it hard to provide high fidelity images without a fortunate alignment between the imaging system and the target.
We have developed an ultra wideband radar based terahertz imaging system that addresses many of these issues and produces high resolution through‐clothes images at stand‐off distances. The system uses a 675 GHz solid‐state transmit/receive system in a frequency modulated continuous wave (FMCW) radar mode working at room temperature. The imager has sub‐centimeter range resolution by utilizing a 30 GHz bandwidth. It has comparable cross‐range resolution at a 25m stand‐off distance with a 1m aperture mirror. A fast rotating small secondary mirror rapidly steers the projected beam over a 50 x 50 cm target at range to produce images at frame rates exceeding 1 Hz. In this talk we will explain in detail the design and implementation of the terahertz imaging radar system. We will show how by using a time delay multiplexing of two beams, we achieved a two‐pixel imaging system using a single transmit/receive pair. Moreover, we will also show how we improved the signal to noise of the radar system by a factor of 4 by using a novel polarizing wire grid and grating reflector.
The research described herein was carried out at the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA, under contract with National Aeronautics and Space Administration.
Professor Les Novak
PhD, IEEE Fellow, Consultant, MIT Lincoln Lab (Retired)
''Interrupted SAR Image Reconstruction: Compressed Sensing Studies''
About the Speaker:
Les Novak worked at MIT Lincoln Laboratory from 1977 to 2003 where he held the position of Senior Technical Staff in the Sensor Exploitation Group. He collaborated on development and procurement of the Lincoln Laboratory 35 GHz Full Polarization Synthetic Aperture Radar. He developed the Polarization Whitening Filter (PWF algorithm) for combining multi-channel SAR data into visually clear minimum speckle imagery having enhanced image quality. He investigated the utility and benefits of full-polarization SAR data in detection and recognition of military ground targets – and developed polarization matched filtering for maximizing target-to-clutter ratio from full-polarization data. He developed full polarization change detection algorithms for the DARPA/Air Force foliage penetration program, resulting in DARPA funding the FOPEN program at MIT Lincoln Laboratory. In 2003 he joined AlphaTech/BAE as Consulting Scientist, developing and testing FOPEN SAR change detection algorithms for the foliage penetration program; algorithms performed successfully and were transitioned to military users. In 2006 he joined Scientific Systems Company as Senior Research Scientist where he was principle investigator of Air Force’s "Interrupted Synthetic Aperture Radar" program -- developed compressive sensing algorithms to mitigate effects of missing data (data gaps, etc.) on SAR image quality and to achieve reliable/robust coherent/non-coherent SAR change detection; also principle investigator on "Compressive Sensing for DCGS-N", investigating utility of compressive sensing to Navy’s airborne, ship, and ground station EO/Radar applications. Also, he supported the NATO SET-172 Lecture Series on "Radar Automatic Target Recognition (ATR) and Non-Cooperative Target Recognition (NCTR)" where he presented lectures on the “Effects of Image Quality on SAR Target Recognition” and “Advances in SAR Change.
Abstract:
An important advance in today’s radar technology is the development of systems that use active array antennas. Systems such as the APG-77 or F-35 JSF employ active arrays which allow the radar to accommodate multiple modes for search, track, target recognition, SAR/ISAR imaging, GMTI, etc. These radar modes may compete for radar resources, resulting in severe timeline demands due to multi-mode operational requirements. One critical radar function is the collection of data to form high-resolution SAR imagery. Since coherent integration time required to form such imagery may be several tens of seconds, the radar may not be able to dedicate an uninterrupted period of time of this magnitude solely for SAR data collection. Other high-priority radar modes must be performed in a timely manner, depending on the operational situation; thus it may be necessary to collect data randomly or periodically to perform other radar modes. Such interruptions will leave data-gaps in the coherent phase-history data which can significantly degrade the quality of the resulting SAR imagery. Thus, advanced image formation algorithms are required to mitigate the artifacts introduced into the SAR imagery as a result of interrupted SAR data collections.
We will demonstrate Compressed Sensing reconstructions of interrupted SAR data from phase-history data having arbitrary gapping patterns, including single contiguous gaps, periodic gaps, random gapping patterns and combinations of these gapping patterns. Among the CS-based reconstruction algorithms evaluated are Basis Pursuit Denoising (BPDN), Iterative Adaptive Algorithm (IAA), MAP iterative reconstruction, Burg gap filling, etc. BPDN image reconstructions are shown to have image quality sufficient for performing reliable SAR change detection (coherent and non-coherent), as well as for performing visual target recognition by image analysts or by computer-based algorithms. Image quality metrics are calculated by comparing the reconstructed image with the original, non-gapped image; IQ metrics include coherence, mean absolute phase error, phase error standard deviation and signal-to-noise ratio. Data used in these studies were gathered by the General Dynamics, 0,3x0.3m, X-band sensor. We also describe joint CS-processing of multi-pass SAR data and demonstrate addiional change detection performance gains.
Dr. Ignacio Montiel-Sánchez
"European Defense Agency and the Challenges faced by Modern Radar
Technology"
About the Speaker:
Dr. Ignacio Montiel-Sánchez holds a doctorate in Telecommunications Engineering and is a Telecommunications Engineer from the Spanish Universidad Politécnica de Madrid. With over 20 years of professional experience in the Instituto Nacional de Técnica Aeroespacial (INTA) in Madrid, Dr. Montiel-Sánchez started working in the fields of antennae and RCS measurements; was responsible for the creation of the Detectability Laboratory; as well as being Head of the Communications, Navigation and Radar Unit. In 2009, he was seconded to the European Commission as a Policy Officer in the Security R&D Unit of DG Enterprise. He currently works for the European Defence Agency where he has held the position of Project Officer Radio Frequency Sensors Technologies since June 2011.
Abstract:
Whenever experts try to assess which could be the most promising and influential trends for radar in the next years, it has to be taken into account the complexity of defence requirements and operations together with some interrelated and synergistic concepts affecting their implementation and future use. It is needed to analyse the impact on radar of different technologies coming from new and evolving information and telecommunication advancements able to provide endless volumes of information. The radar sensors are evolving into multifunction RF systems integrated in mobile autonomous platforms. And those will be part of a wide net of infinite heterogeneous sensors that will have to be protected as vulnerabilities exponentially increase and where spectrum will be a limiting factor. The advance experimented by machine learning instantiated by Deep learning techniques will enhance the performance of sensors and be supported by knowledge based radar techniques. The way to deal with all these conditionings and requirements and the need of specific frameworks will be discussed in this presentation.
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Dr. Thayananthan ThayaparanPhD, Defence Scientist, DGSTCO, Ottawa Research Centre Defence Research and Development Canada / Government of Canada ''HF over-the-horizon-radar (OTHR) in Canada'' |
About the Speaker:
Thayananthan Thayaparan is a Defense Scientist with the Defence R&D Canada - Ottawa. He holds a BSc Honors in physics from the University of Jaffna in Srilanka, an MSc in physics from the University of Oslo in Norway, and a PhD in atmospheric physics at the University of Western Ontario in Canada. His interests are synthetic aperture radar (SAR), inverse SAR (ISAR), over-the-horizon radar (OTHR) applications, time-frequency analysis for radar imaging and signal analysis, and radar micro-Doppler analysis. He is a Fellow of the IET (Institute of Engineering & Technology). He serves on the editorial board of IET Signal Processing. He wrote four editorials for the international journals IET Signal Processing and IET Radar, Sonar and Navigation. He coauthored a Text Book entitled, ‘Time-Frequency Signal Analysis with Applications’, Artech House Inc., ISBN: 978-1-60807-651-2. He was the recipient of the IET Premium Award for Signal Processing for the best paper published in 2009–2010. He has published over 220 in journals, proceedings, and internal distribution reports.
Abstract:
Today, many countries require the over-the-horizon radar (OTHR) to provide a long-range, wide area surveillance capability due to modern day terrorists, smugglers and the need to monitor one’s economic zone and off-shore resources. OTHR systems operate in the high-frequency (HF) band 3-30 MHz and use either surface-wave propagation or sky-wave propagation. Sky-wave OTHR systems are installed inland and make use of the ionospheric refraction of the radio waves several hundred kilometers above the Earth’s surface to overcome the line-of-sight limitation caused by the Earth’s curvature. Surface-wave systems operate in the lower part of the HF spectrum and are installed on the coastlines to make use of the electromagnetic coupling of the emitted radio waves to the sea surface allowing propagation to extend over the horizon. The significant difference between sky-wave and surface-wave radars is that sky-wave radars have large detection ranges beyond the horizon, up to 2000 nautical miles (nmi), while surface-wave radars’ detection range is limited to about 100 nmi. The reason for the extended detection range for the sky-wave propagation in the ionosphere is that the losses caused by the ionization and absorption in the ionosphere are much less than the surface-wave diffraction loss. Ionospheric effects such as multipath and Doppler spreading are also significant. In this talk, we examine sky-wave and surface-wave OTHR concept including the characteristics of the ionosphere on the propagation of the radio waves.