Despite of US and South Vietnam forces had overwhelming superiority in number and maybe quality of aircraft, North Vietnamese combat aircraft also take part in combat since 1966. I wonder the US Air Defense units saw any combat in Vietnam and what weapons they had?

If you are referring to Air Defence Artillery/missle forces, I know that the USMC deployed Hawk missle batteries to RVN, in the Marble Mountain area, near Danang. As for pure Air Defence fighters, the USAF deployed F102 intercepters to Bien Hoa AB, near Saigon , but ended up using the for some ill conceived CAS type missions.

All that having been said, I don't think the North Vietnamese ever attempted to project airpower outside of their air defence zones in the Hanoi/ Haiphong region, even as late as 1975; although I recall hearing about an airborne feint/attack on the USN radar picket, Red Crown, one night in Nov 1972, in the northern Tonkin Gulf, never had an oppurtunity to research that though.

I have heard there were self-propelled tactical AA systems in Vietnam - M-163 `Vulcan` and M-42 `Duster`... Just wander did they saw any action against flying targets or were used only on ground targets?