Radar for surveillance in an urban environment – Final report

Authors:

  • Stefan Nilsson
  • Åsa Andersson
  • Tomas Boman
  • Magnus Gustavsson
  • Tommy Johansson
  • Mikael Karlsson
  • Ain Sume
  • Anders Örbom

Publish date: 2014-12-31

Report number: FOI-R--3970--SE

Pages: 33

Written in: Swedish

Keywords:

  • “see-through-the-wall”
  • wall penetrating radar
  • Doppler radar
  • see behind corners
  • polarimetry
  • polarization
  • urban scenario
  • battlefield surveillance
  • SAR
  • ISAR
  • MIMO.

Abstract

This final report gives an account of the activities carried out and the results produced in the three-year Swedish Armed Forces' project Battlefield Surveillance Radar. The project has involved a further development of the competence and technique platform established by FOI through previous efforts established in the research areas of Wall Penetrating Radar and Radar for Seeing behind Corners. The project has focused on the phenomenological and technical study, evaluation and development of methods, signal processing and system solutions for both Doppler-based and imaging wall-penetrating radar systems adapted for the urban scenario. The project has participated in the NATO group Advancing Sensing through the Walls Technologies (2009-2014). The group studies methods and techniques that increase the ability to detect, track and image primarily humans behind walls. A common field test carried out at DRDC in Ottawa in 2013 with various wall-penetrating systems has been analysed and evaluated this year. The results will be reported in the forthcoming final report. In order to improve detection performance with human targets behind the wall we have investigated the possibility to use polarimetric waveforms. A certain human-to-background contrast enhancement has been produced by means of polarimetric optimization but the effect is not pronounced enough to motivate further research efforts. We have also investigated methods to reduce the effects of wall interaction in imaging wall-penetrating measurements. The purpose is to create better imaging of stationary objects close to the wall. A simple method for wall reduction has been tested and found to give improved detectability. The method requires no prior knowledge of the wall properties. The method introduced by FOI to detect human movement behind corners by radar has been developed further. An urban see-behind-corners trial has been performed at a mock-up town on the Swedish Armed Forces' training ground Kvarn. The aim was to investigate the potential of the method and to evaluate it from an operative perspective. The measured scenes included persons walking, cycling, and driving cars, moving individually or together along pre-defined paths. The data analysis shows that detection of moving targets behind corners is possible in a realistic environment. Multiple targets can be singly distinguished when allowed by the range resolution. With suitable antenna positioning large parts of the street can be surveyed, making it difficult for persons or vehicles to move unnoticed on the street. Our method of analysis is robust with respect to different measurement situations and together with Doppler analysis it should be possible to develop methods for better detection, tracking and classification of objects. A specific micro-Doppler analysis has shown that the micro-Doppler signature is preserved after several wall reflections. This positive quality can hopefully be used for classification of various objects, e.g. for distinguishing a walking person from a vehicle. Also the analysis of conventional Doppler signatures indicates a potential for distinguishing between closely spaced targets. We have shown in simulations that a system solution with narrow scanning antenna beams can be used for positioning of a moving target just by utilization of multiple reflections. However, the concept assumes good knowledge of the geometry of the environment. The radar measurement equipment Lilla Gåra has been physically integrated this year with an existing 2D array antenna, developed at FOI. The purpose is to enable electronic control of the antenna beam, e.g. to achieve target tracking or to be able to generate 3D-images. Performed test measurements show that the integrated system works.