Prof. François LE CHEVALIER
Prof. François LE CHEVALIER, Delft University of Technology/Thales Air Operations, France
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Biography:
François Le Chevalier is in charge of the Chair “Radar Systems Engineering” at Delft University of Technology (The Netherlands), and Scientific Director of Thales Air Operations Division in Rungis (94), France.
Mr. Le Chevalier began his career at the Office National d’Etudes et de Recherches Aérospatiales (Onera), where he initiated research on radar target and background signatures processing. In 1986, Mr. Le Chevalier joined Thomson-CSF (now Thales), where he pioneered French developments in adaptive digital beamforming and STAP radar systems demonstrations, and shared apertures and multisensor concepts design and validation. In 1998, he joined the Airborne Systems group, as Scientific Director, in charge of advanced research and developments coordination (airborne radars, electronic warfare, airborne mission systems). His current research activities include space-time coding for active antenna systems, and wideband unambiguous radar systems.
He has been active in- or chairing- the Technical Program Committees of most IEEE International Radar Conferences since Brest, 1999, has recently chaired the Technical Program Committee of EURAD 2012, Amsterdam, and will be the honorary Chair of SEE/IEEE International Radar Conference in France, 2014.
An author of many papers, tutorials, and patents in radar and electronic warfare, Prof. Le Chevalier, an Emerite member of the Société des Electriciens et des Electroniciens (SEE), is the author of a book on “Radar and Sonar Signal Processing Principles” published by Artech House in 2002, editor of “Non-Standard Antennas”, published by Wiley in 2010, and co-author of “Principles of Modern Radar: Advanced Techniques”, published by Scitech, IET Publishing, 2012.
Title: Wide Band - Wide Beam Motion Sensing
Abstract:
Objectives
The instantaneous bandwidth is a critical radar parameter, with direct influence on the performances, but also on the cost – this being especially true for active antenna systems, where multiple channels reception is generally implemented for taking full advantage of the flexibility. It is therefore important to consolidate an overall view of the expected benefits of an increased bandwidth, taking into account all possible effects.
In this keynote speech, we will analyze the relations between range, Doppler, and angle, – including simultaneous transmissions, or colocated MIMO – , for detection and location of moving targets. The idea is to contribute to a better understanding of the benefits of widening the bandwidth for detection of moving targets, focusing not only on waveform aspects, but also on the velocity and angular measurement consequences.
Wideband Waveforms: unambiguous detection and location of moving targets
Widening the bandwidth of a radar has significant influence on moving targets characteristics, as soon as fluctuating targets, and clutter limitations are considered. The global effect on clutter reduction is well-understood – decrease of clutter RCS, increase of fluctuations – but a reliable model for difficult situations is still missing. Taking into account target fluctuations has also been considered for many decades, but the consequences on detection performances are still debated: a simple model will be proposed in this keynote speech for radar design purposes.
Another consequence of range resolution improvement is less generally acknowledged – and might provide wider benefits: the removal of Doppler ambiguities (and associated blind velocities) for low prf radars: recent results for wideband clutter cancellation will be presented in this talk, and their consequences on system aspects (e.g. velocity resolution) will be outlined.
Finally, it will be shown that widening the bandwidth also improves the angular discrimination of extended targets – a significant gain when threat evaluation is required – , and the associated performance will be estimated.
Space-time coding: simultaneous transmissions for wide instantaneous angular coverage
The basic trade-offs governing focused beam and wide beam digital beamforming for multichannel coherent receiving systems are now well established, especially regarding the relation with Doppler resolution and ensuing clutter suppression. Taking also into account the possibility of simultaneous multiple transmission makes the problem more complex, since more degrees of freedom are available, but also provides significant benefits.
The exact added value, however, is not easily defined, and requires analysis of 3D ambiguity functions, for clarification of the existing trade-offs between spectral bandwidth occupancy and clutter cancellation, for different classes of space-time radar waveforms appropriate for specific operational scenarios.
Space-time waveform generation and coding will then be presented in detail, and illustrated with different basic examples. Special attention will be given to analyzing the consequences of space-time coding (fast-time or slow-time) on Doppler-range-angle performances, for different airborne and surface-based applications.
Taking into account the previous analysis of wideband waveforms, specific properties of wideband space-time waveforms will then be identified, with special attention to ambiguities and to clutter cancellation. This analysis will aim at identifying the additional benefits for small targets extraction, separation and classification in adverse environments, and estimating the cost of such added benefits.
Conclusion
Due to their wide range of operational and technical advantages, active antenna systems are now becoming a standard for high performance radar systems. However, this talk will show that widened bandwidths are also key to operational performance improvement: new architectures can be designed for future radar systems, where modern front-end capabilities taking full benefit from the available agility and diversity – through optimized signal generation and processing techniques – to improve detection of targets and threat analysis in difficult environments.
