Created some drawing to help you understand, that modern SAM missiles are rather an endgame (semi active) guided ballistic missiles, than anything else.
Here are some classic SAM designs...
... and here are the modern SAM's. (Patriot/S-300/-400)
the upper one is a SCUD ballistic missile.
Usual flight path of the Patriot/S-300/-400 missiles is a ballistic one:
Hpasp Free SAM Simulator, "Realistic to the Switch" (U-2 over Sverdlovsk, B-52's over Hanoi, F-4 Phantoms over the Sinai, F-16's and the F-117A Stealth bomber over the Balkans.) http://sites.google.com/site/samsimulator1972/home