RCS measurement of IHF-Boat

Radar Cross Section (abbr. RCS) is a measurement quantity for the power of an electromagnetic wave scattered by an object. It can be interpreted as a measure of visibility of an object to a radar system. Besides the characteristics of the radar system itself the RCS of a radar target affects the maximum distance at which the target can be detected unambiguously.

However, the RCS of an object can be maximized or minimized by altering shape and/or surface of objects. This effect can be utilized for fulfilling specific requirements on radar targets, e.g. for designing aircrafts and ships with stealth properties to avoid their detection by conventional radar systems. Also the construction of reflectors with remarkably high RCS becomes possible.

For the purpose of radar cross section measurement and evaluation RCS measurement ranges are used. Typical chamber types are outdoor, farfield and compact ranges. These ranges should meet a variety of specific requirements, such as:

  • An appropriate design of the measurement chamber which guarantees the generation of a plane wave at the radar target
  • A support structure for the radar target which has both a high mechanical load capacity and a low RCS
  • A high dynamic range of the receiver
  • Precise calibration standards
  • Extensive postprocessing of measurement data
  • Skilled range operators

Research activities at IHF

The RCS measurement range of the institute of high frequency technology fulfills the aforementioned requirements and is able to perform full polarimetric RCS measurements of targets up to 100 kg in a frequency range from 2 GHz to 24 GHz at any time. Various cooperations with manufacturers of RF measurement equipment allow us to cover frequencies up to 95 GHz on demand.

Additionally, our institute has implemented a toolchain for optimization of the RCS of arbitrary objects. This includes:

  • Development of the required geometry
  • Simulation with suitable simulation tools (MoM, Raytracing)
  • Assembly of radar target in our machine shop
  • Measurement within RCS measurement range
  • Analysis of measurement data
  • Generation of measurement reports

References

Peters+Bey Development of a naval reflector fulfilling ISO-Standard 8729-1:2010(E) in cooperation with Peters + Bey. A new reflector geometry was developed, simulated, built, measured, certified and registered for patent protection. For a while this was the only passive reflector geometry approved for the aforementioned standard.
Continental Measurement and characterization of a reference target used for calibration at 77 GHz for Continental, Division Chassis and Safety. The measurement setup was realized with equipment of Anritsu.

Radar imaging

Since the invention of pulsed radar it is possible to determine the distance of objects lying in the propagation path of the transmitted pulse. If the radar system is additionally moved along an axis orthogonal to the propagation direction of the pulse, it is possible to generate a two-dimensional image of the scene. Since the resolution of the radar image depends on the size of the antenna footprint, the resolution of these images is typically low. By processing the images with common focussing algorithms afterwards, the resolution can be increased significantly. These algorithms are typically used in air- and spaceborne radar systems for remote sensing and in measurement ranges for the examination of scattering mechanisms.

Research activities at IHF

Radar image of octaeder reflector

Besides recording and postprocessing RCS measurement data, we use radar imaging algorithms for the visualization of scattering centers of radar targets at our institute. Therefore full polarimetric measurements of radar targets for the generation and analysis of polarization dependent radar images can be performed.

Besides the compact range the planar near field chamber of our institute can be used for the implementation and testing of near field imaging algorithms.

Additionally, polarimetric methods which enable the analysis of scattering mechanisms occurring in the radar target are investigated.

Current student projects on this topic complete our research activities in this area.

IHF-Boat

To be able to demonstrate the performance of new algorithms and research results in the area of inverse synthetic aperture radar (ISAR) imaging and radar-cross section measurements, a comparison standard is needed. Such reference targets should not only allow a comprehensive comparison of measurement results, but also show the applicability of new ideas to real-world problems. Therefore we designed a reference target with the shape of a ship following a previously developed requirements catalogue. By performing measurements of the radar cross-section and applying ISAR imaging, we could demonstrate that the target fulfills the requirements.

To make the IHF-Boat available to everyone who wants to build such a reference target, we released all documentation and technical drawings under Creative Commons license and made the files available here.

IHF-Boat: Front view
IHF-Boat: Rear view
IHF-Boat: Radar cross-section of VV component at 10 GHz
IHF-Boat: Radar image of VV component

Polarimetric radar imaging

Not only the position of scattering centers in a radar image is of interest for the analysis of radar targets, but also the scattering mechanism occurring at these points. For example, reflections at wire-like structures are strongly frequency dependent and can be recognized within large angular ranges. This is not the case for reflections occurring at flat or slightly bended surfaces. Thus these mechanisms must be handled differently depending on the goal of the target's design process. For the identification of different mechanisms polarimetric decomposition methods can be used. At the institute of high frequency technology these decomposition methods are developed and investigated.

IHF-Boat: Radar image of all single reflections
IHF-Boat: Radar image of all double reflections
IHF-Boat: Radar image of all polarizing reflections (edges, wires and wire antennas)