A secondary radar system is a cooperative target identification
system in which the interrogator transmits an encoded signal to
a target. The signal transmitted by the secondary radar
is intercepted and received by the target. The target has
a transponder on board that interprets the encoded signal and
transmits an encoded reply back to the interrogator. The secondary
radar system receives and interprets the target's encoded signal.
The
identification friend or foe (IFF) system is a good example
of a secondary radar system that is in wide
use in the military environment.
A great deal of valuable information
can be provided to the secondary radar by the
target's transponder. The transponder provides an identifying code to the
secondary radar that then uses the code and an
associated database system to look up aircraft origin and destination,
flight number, aircraft type, and even the numbers of personnel
on board. This type of information is clearly not available
from a primary radar system.
Secondary radar systems are also
known as secondary surveillance radar (SSR).
Other topics in our resources on Radar related to Secondary Radar include: