Eons ago, I was in the group that was studying on-orbit self defense for satellites. One option we looked at was basically a flying bomb rack that would co-orbit with a critical satellite and fire interceptors at ASATs closing in.
Our interceptors would have conventional explosives, but we looked at using a radar altimeter from nuclear bombs to trigger our warhead. Big problem is that said radar was designed to activate based on an Earth-sized mass getting close, while our postulated targets were a wee bit smaller.
Ron Wanttaja