RRSN Group

Research Areas

Filed in: ResearchActivity.ResearchAreas · Modified on : Tue, 01 Oct 13

Passive Coherent Location

In recent years the use of Passive Bistatic Radar (PBR) for surveillance purposes has received renewed interest. PBR exploits existing illuminators of opportunity to perform target detection which results in the exciting possibility of low cost surveillance, reduced pollution of the e.m. environment, etc. Among all the available emitters, broadcast transmitters represent some of the most attractive choices for long-range surveillance applications, owing to their excellent coverage. Fabiola Colone is involved in a number of research projects aimed at demonstrating the potentialities of PBR for long range surveillance applications. To this purpose she has looked at the use of analogue signals such as FM and HF radio, as well as digital transmissions such as DVB-T.

In addition she is also investigating the potential exploitation of the PBR principle in local area monitoring applications, aiming at the detection and localization of designated human beings or man-made objects within short ranges; in this case wider bandwidth signals of opportunity are exploited to achieve the required range resolution such as wireless Local Area Network (LAN) transmissions (WiFi signals), Metropolitan Area Network (MAN) transmissions (WiMAX), and GSM signals.

In the above applications, Dr. Colone has been involved in different activities devoted to: (i) signal and scenario computer simulation; (ii) design of innovative processing techniques for disturbance cancellation and target detection and localization; (iii) development of experimental PBR prototypes.

STAP for AEW Radar

The scientific framework of the research activity carried on by Fabiola Colone deals with the issues of clutter cancellation and moving target detection from Airborne Early Warning (AEW)multi-channel radar data. It is well known that, due to the platform motion, a discrimination based only on the Doppler frequency is not effective for the slow targets, since the clutter spectrum is widened and spreads over their Doppler frequencies. Using multiple antenna sub-apertures and a coherent pulses train allows to perform space-time clutter cancellation, with a much narrower notch than using Doppler information only, so that also slow targets can be detected.

Space-Time Adaptive Processing (STAP) for air- and space- borne MTI radar systems has seen a significant increment of interest during the last decades in the international radar community. The research activity of Fabiola Colone joins these trends. It is primarily focused on the development of advanced STAP techniques for ground slowly moving target detection and localization with application to AEW radar. The scientific activity is also supported by the analysis of some technical issues of the considered systems. Fabiola Colone works on these topics in projects funded by the Italian radar industry.

GMTI with Space-Borne Multi-Channel SAR

The research activity carried on by Fabiola Colone in this framework is focused on the issues of clutter cancellation and slowly moving target detection with space-borne multi-channel SAR systems for surveillance purpose. Fabiola Colone worked on these topics inside the project “MSAR2G: Multi-Beam SAR of Second Generation” funded by the Italian Space Agency (ASI). The Project aimed at designing the required modifications for the COSMO-SkyMed SAR of 1st generation (developed by Alenia Spazio) to obtain a multi-channel sensor by splitting the active phased array antenna in multiple sub-apertures. As Manager of the Work Package devoted to the MTI Multi-Beam application, Fabiola Colone co-ordinated and carried on all the activities required to assess the effectiveness of the modified sensor in such application. Moreover she was involved in the activities related to the system parameters and architecture design, which can strongly affect the MTI techniques performance. The key-points of her research activity in this framework are: (i) the antenna structure optimization to maximize the MTI performance; (ii) the definition of new operational Multi-Beam modes which exploit the potentialities of the different Multi-Beam techniques (MTI, ATI, MultiPol,..) and allow their coexistence; (iii) the preliminary design of the technological implementation of the modified sensor.

GMTI with Bistatic Air-/Space-Borne Radar

The research activity of Fabiola Colone in this framework is focused on the design of effective processing techniques for slowly moving target detection from air- or space- borne bistatic radar systems with multi-channel RX and co-operating TX. At its first stage the analysis aimed at demonstrating the effectiveness of STAP techniques in bistatic MTI radar systems; then ad hoc STAP strategies have been derived to cope with the severe clutter scenario typical of bistatic geometries. Bistatic radar systems must effectively cope with severe, spectrally diverse ground clutter returns due to the simultaneous transmitter (TX) and receiver (RX) motion which yields a non-stationary behavior of the clutter spectrum as a function of range. Many researchers view STAP as an enabling technology also for bistatic MTI radars. However the non-stationary nature of bistatic ground clutter limits the practical implementation of the standard STAP approach, which relies for covariance estimation on secondary data obtained from adjacent range cells. For this reason, STAP techniques developed for monostatic radar systems require modifications in the bistatic case. An effective approach to limit the effect of clutter range-dependence is the direct removal of the non-stationary characteristics of the 2D data spectrum (Angle, Doppler) from the bistatic data set by means of ad hoc compensation techniques, before estimating the clutter covariance matrix. Following this approach Fabiola Colone proposed a pre-processing strategy for the secondary data which allows not only to compensate for the Spectral Centers misalignment, but also for the clutter Doppler-Angle trajectory slope variability over range. This approach allows to further reduce the bistatic geometry-induced clutter dispersion, with respect to previous techniques, thus improving the performance achievable by the following STAP without increasing significantly the computational load.

Non-Linear Apodization Techniques

Radar imaging often requires sidelobe control; as well known both linear and non linear techniques can be used to reduce the sidelobe level. Linear techniques are based on the use of amplitude weighting function (frequency domain) before the final Fourier transform: in this case the reduction in sidelobe level is obtained at the expense of the mainlobe width with a loss in resolution. Apodization techniques are non linear techniques which have been proposed to reduce sidelobe level while preserving mainlobe resolution. This is of particular importance especially in range dimension where the high resolution is provided by the transmitted bandwidth, usually limited by technological or regulations constraints. Due to their non linear behavior, Fabiola Colone is interested in understanding the impact of the apodization techniques on the quality of SAR images in terms of capability of extracting information from apodized SAR images. The analysis of the statistical properties of the apodized SAR images allowed her to develop proper classification schemes in order to maintain the information extraction capabilities while at the same time reducing the sidelobe level and preserving the mainlobe resolution.

Adaptive Interference Rejection on GPS Receivers

In the framework of a project funded by the University of Rome “La Sapienza”, Fabiola Colone studied the possibility to reject the effect of intentional e.m. interferences on the GPS (Global Positioning System) signal by applying antenna-based ECCM techniques. These techniques allow to keep a null of the antenna pattern on the DOA of the interference whose characteristics are adaptively estimated from the received data. Fabiola Colone developed different techniques based on different constraints imposed on the antenna pattern (no constraints, maximum gain on the visible satellite directions, maximum gain on one satellite). The performance evaluation has been carried out for different operative conditions. Particular attention has been devoted to the trade-off between interference rejection capability, system complexity and degrees of freedom (depending on the number of array elements and on the number of imposed constraints in the maximization stage).

GPR Data Processing

The research activity of Fabiola Colone in this framework is focused on the assessment of the GPR (Ground Penetrating Radar) effectiveness as a non-invasive instrument for archaeological purpose. She was involved in the collaboration with the Archaeological Dept. of the University of Rome “La Sapienza” for the GPR prospection of archaeological sites in Western Sicily (funded by the University of Rome). In this framework she took part to the prospection campaigns in the island of Mozia (Sicily) and to the subsequent data processing.

Powered by PmWiki