The AN/SPY-3 is an X-band, active phased array radar which has been developed by Raytheon for the US Navy to be used for both blue-water and littoral operations. It can combine the functions of up to five radars and ten antennas. AN/SPY-3 is the first US shipboard Active Electronically Scanned Array (AESA) system which operates in both the X-band and S-band of radar frequencies. The SPY-3 radar was designed for the Navy's newest amphibious warfare ships, the next generation aircraft carrier, CVN-77 and the DD(X) class of surface combatant ships. MFR was initially planned for introduction in CVN-77 and next-generation CVNX aircraft carriers and the now-refocused DDX surface warship programs.
While the AN/SPY-3 is capable of performing most functions in either frequency band, for functions such as horizon search (anti-sea skimmer) and precision track (for fire control), the band can be selected for current atmospheric, target characteristics, and other factors such as anomalous and multipath propagation. It has a single 6-faced antenna that can share the bands when, for example, the electronics in one band are controlling a maximum number of missiles. X-band functionality, in the 7 to 12.5 GHz frequency range, is optimal for low-altitude propagation effects, narrow beam width for best tracking accuracy, wide frequency bandwidth for effective target discrimination, and the target illumination for SM-2 and Evolved Sea Sparrow Missiles (ESSM). Using the S-band is advantageous for search, operation in all forms of weather, and a narrow beam width for target tracking and resolution.