According to Aviation Week, the Pentagon is now developing active electronically scanned array (AESA) radars that could be used as weapons.
A bizarre historical twist to this story is that in 1934, a rumor was started to the effect that Nazi Germany had developed a death ray based on radar. Physicist Robert Watson-Watt was asked to check on the feasibility of such a weapon. He quickly determined that it was unlikely, but that using radio waves to locate incoming bombers might be a real possibility. By 1937, three stations were ready, with more to come; this was a key element in winning the Battle of Britain during WWII.
It was a British writer, H. G. Wells, who first suggested the idea of "death
(This Science Fiction in the News story used with permission from Technovelgy.com