for ATC systems i did a search on yahoo on cns/atm which gave a whole lot of sites that may or may not help you. Use it don't use it.
Anyway in case you were wondering CNS/ATM means
Comunication, Navigation, Surrveilance/Air Traffic Management
which is the buzz words that all the hevs use constantly.
Just at a glance the raytheon site looks like it has lots of info
www.raytheon.com/products/cnsatm/