Advanced Millimeter-Wave Radar Absorbing Materials

The EMA team possesses the skills and experiences uniquely aligned to investigating current absorber performance, identifying key candidates for improvement, developing a path forward, and ultimately delivering alternatives and upgrades to existing absorber solutions. The impact of clutter drives the need for absorber improvements. Our experience in computational electromagnetic (CEM) modeling, RF absorber materials, RCS ranges, and electromagnetic theory are the resources needed for a successful investigation. The EMA team consists of Spann Consulting Services, PPG Cumming Microwave, ETS Lindgren, Compass Technology, Georgia Tech Research Institute (GTRI), NAVAIR Point Mugu, and Electro Magnetic Applications, Inc.  During the Phase I effort, our team studied three primary types of absorbers per the direction provided by our Air Force TPOC. The three types were Rug RAM, pyramidal, and convoluted. Rug RAM is a type of carpet absorber with loaded fibers sewed into a rubber mat, which is also likely loaded. The Air Force uses Rug RAM for their outdoor measurement range. The Air Force desires to have a replacement product for Rug RAM that has equivalent or better performance in terms of reflectivity, flexibility, and ability to stand up to the environment and working conditions. The EMA team has a plan for developing and delivering a replacement Rug RAM product by working with GTRI and PPG Cumming Microwave to develop an alternative solution with equal or better performance. During the Phase I, pyramidal absorber performance was studied extensively with CEM simulations to understand the scattering centers associated with this type of absorber and to explore ways to improve the performance through shaping and material property modifications. The results of these studies showed great promise for significantly improving pyramidal absorber performance by changing the tip design, modifying the shape of the sides of the absorber, and coating the absorber with a low loss material to bend more of the incident energy into the absorber. During the Phase II, the EMA team will work with ETS Lindgren to produce samples of new pyramidal absorber designs for X-, Ka- and W-bands that incorporate the most promising results from the Phase I. RCS measurements will be performed for the new pyramidal absorber designs and compared with baseline solutions to demonstrate performance improvements.The Phase I studies of convoluted absorber were less extensive than the pyramidal absorber studies. Nonetheless, the results of these studies matched expectations that the RCS of convoluted absorber is strongly dependent on aspect and elevation angles. A major goal for the Phase II effort is to explore ways to ruggedize convoluted absorbers to meet the environmental and operational requirements for the outdoor ranges at Eglin AFB.