Organic Radar Absorbing Materials

6 January 2005

The Dockyard Laboratory Pacific, a section of DRDC Atlantic, with the support of Technology Investment Funding has been leading a project on the development of Radar absorbing material, RAM, and the reduction of Radar cross section, RCS. A multidisciplinary team of researchers have been involved in this three year study, including researchers at The Dockyard Laboratory Pacific, DRDC Ottawa, Concordia University and the University of Victoria.

Radar is an efficient and sensitive method for detecting the presence of ships and aircraft over long distances. The amount of signal that is reflected from a platform depends on the material from which the ship is made and its shape. Highly conductive materials, such as metals, reflect nearly all of the microwave energy incident on its surface, while flat sides and corners in the ships structure direct the electromagnetic energy back to the radar antenna.

DRDC Ottawa with Concordia University have been working on a software program to predict the RCS of a ship, based on its structure and position in relation to the radar antenna. The RCS is a parameter that indicates the detectability of an object by radar and as such provides a threat assessment indicator. The software code gives a colour indication of where hotspots exist in a ship’s structure. This information can be used during ship design, for the minimization of the RCS. It can also be used to highlight where RAM should be applied to reduce the RCS. The code has the capability to recalculate the RCS when RAM patches have been applied to hotspot areas.

RAM patches are materials that absorb microwave energy. Researchers at The Dockyard Laboratory Pacific have been making conducting polymers and processing them into usable forms. These materials have a finite resistance that converts electrical energy into heat. The electrical energy in the conductive polymer arises from electrical currents induced by the electromagnetic field of the microwave interacting with electrons in the conductor. The optical properties, permittivity and permeability, of the conductive polymers can be varied over a wide range depending on synthetic and processing methods.

Researchers in the Department of Electrical Engineering at the University of Victoria have developed a method for measuring the optical properties of the conductive materials. This information is needed so that synthetic-property relationships can be studied and for the calculation of the materials and structure needed to fabricate the best possible radar absorbing material. A materials measurement facility has now been established at The Dockyard Laboratory Pacific.

Another issue with conductive materials is their stability to environmental degradation. Researchers in the Chemistry Department at the University of Victoria have explored the synthesis of new conducting polymeric materials with the aim of enhancing their stability. Some promising results have been achieved with respect to stability and now the range of properties needs to be expanded.

Knowing the optical properties and how to fabricate materials with those properties are the first steps to developing a thin broadband radar absorbing material. Researchers at The Dockyard Laboratory Pacific have been working on a software program to optimise the structure and materials used in fabricating a multilayered absorber. The program is based on the genetic algorithm, which uses the principles of Darwin’s theory of evolution and genetics to iteratively improve a group of randomly created absorbers, based on the reflectivity over the widest bandwidth while also optimising for the thinnest absorber possible.

TIF funding for this work finished in March 2004. Research is still continuing to develop new and better materials while working towards producing optimized thin broadband microwave absorbers.