From the economist article posted above.

“Engineers at Lockheed Martin, a large American defence contractor, have designed a radar system called FOPEN, short for foliage penetration. It became operational in 2005, but still requires further development and is deployed on just one active American warplane so far. But Lockheed Martin’s FOPEN programme manager, Robert Robertson, says the radar “will see whatever man made” under a leafy triple canopy, or under netting designed to foil conventional radar systems”