Here is how you figure out the US Army/Navy code designations. http://www.milspec.ca/radcodes/ancodes.html
So if you wanted to break down AN/SPY-1D(V)4:
AN/ indicates it uses the JETDS.
S: where it is installed (surface ships).
P: Type of equipment (radar).
Y: Purpose of the equipment (surveillance and control).
1: Is the model number.
D: Is the modification letter.
(V)4: Is the 4th variant of the SPY-1D family.