An isolation barrier for reducing coupling between a transmitting antenna on a platform and a receiving antenna on the same platform. The isolation barrier expands the isolation capabilities of radar absorbing material (RAM) to the low frequency region by integrating dielectric loaded corrugations with the RAM. The isolation barrier includes a plurality of corrugations, each including a channel with two conductive walls and a conductive base, having a depth greater than a quarter of the wavelength corresponding to the low-frequency limit of the shared operating frequency band of the transmitting antenna and the receiving antenna. A layer of radar absorbing material (RAM) covers the corrugations.