Radar for surveillance - progress report 2015

Authors:

  • Stefan Nilsson
  • Thord Andersson
  • Åsa Andersson
  • Magnus Gustavsson
  • Tommy Johansson
  • Jan Svedin

Publish date: 2016-02-17

Report number: FOI-R--4225--SE

Pages: 27

Written in: Swedish

Keywords:

  • Doppler radar
  • “see behind corners”
  • “see-through-the-wall”
  • wall penetrating radar
  • polarization
  • urban scenario
  • battlefield surveillance
  • MIMO
  • NLOS

Abstract

This progress report gives an account of the activities carried out, and the results produced in the first year of the three-year Swedish Armed Forces sponsored project Radar for Surveillance. The project involves a further development of the competence and technology platform established through previous efforts in the research areas of Wall Penetrating Radar and Radar for Seeing behind Corners. The project is focused on developing methods and system solutions primarily for Doppler radar system designed for urban environments. An important research task for the project is to investigate how a network of small radar sensors can work together to cope autonomous monitoring in various situations, where detection of small aerial vehicles (UAVs) represent an important case. During the year, literature studies have been conducted to increase knowledge of the research front and available commercial off-the-shelf hardware. The method used to detect and track an UAV is based on the ability to detect the Doppler signature of the rotor blades. As a first step, the radar cross section of the rotor blades of a quadrocopter as a function of its aspect angle, and radar frequency, has been calculated. The FOI-introduced method of using radar to detect moving objects behind the corner has been further studied, and a deeper analysis of the previous measurements have provided interesting new results. The analysis shows that several moving targets can be distinguished where the range resolution allows, and Doppler signal processing can in some cases be used to separate two moving objects in the same range bin. The ability to count and track targets have also been demonstrated. In a special analysis we also demonstrated that micro-Doppler signatures are preserved after the radar wave has undergone several wall reflections, and can thus be the basis for target classification. These new research findings have been published in a scientific paper. A combined analysis of detections, the Doppler spectrum and micro-Doppler spectrum should thus provide the conditions for the development of improved methods to detect, track and classify objects. The system concept, developed for positioning of objects around the corner, has in new simulations showed promising results. This system, or a similar concept that also utilizes multiple reflections to achieve robust positioning and tracking of moving objects around the corner, should be further developed aiming on a possible system solution, which also might be placed on a vehicle. In a small pilot study, we have investigated the possibility of detecting moving objects around the corner, using a radar located on a moving platform. The main question is whether it is possible to filter out the unwanted Doppler clutter from the stationary environment (e.g., house walls) which is created by the platforms own movement. The clutter will likely compete with the target's signature in the Doppler spectrum. A small literature study together with test calculations, shows that the problem is not unsolvable. Furthermore, a potential clutter compensation method has been identified, but it needs to be adapted to this application. During the year, two international surveys have been performed. The first is a survey of military and civilian wall penetrating radar systems available on the commercial market. The study shows that new development occurs primarily among smaller, simpler and cheaper systems with the ability to at most measure the distance to the target. The product development has been halted for the most advanced and costly systems, with ability to position the targets. The other survey summarizes the latest developments in the field of person scanning with high-resolution imaging radar system, where all known available commercial systems are reported. The development of electronic beam forming system has gained momentum and several such systems are now available. These systems operate in the frequency range of 25-80 GHz. The project finances the participation in the NATO Group Advancing Sensing Through the Walls Technologies (2009-). The group studies new improved methods to detect, track and image people behind walls. Results from the joint trial in Ottawa in 2013 with various nations' wall-penetrating systems, will be reported in the final report which will be published next year.