How is any of that relevant when the target is above the horizon? Radar wave hit target. Radar wave come back and hit missile. Shouldn't that be all that matters? Why the hell would they design a missile that can't see a target in this regime?

And furthermore, how is the relative speed zero? The radar waves would still be getting red shifted by a fleeing target regardless of your airspeed. Or are you saying that the waves are slightly blue shifted because of your forward speed, and then the resulting red shift makes the missile filter it? But once again, if that's the case, how the hell did they not think of that? They obviously did given the fact the on board radar's receiver can maintain lock. Why would they not implement that same logic into their missiles?