What is the “staggered PRF” operation?
Staggered PRF operation is used on many radars (almost all, in different forms). Staggered PRF are mainly used to cope with multiple-time-around echoes. In fact, as explained in radar basics, targets at ranges greater than Ru=c.T/2 (where T is the pulse repetition interval) appear as echoes of the following pulse at shorter range. Apparent range Ra = Rr-Ru where Rr is the real range. It is possible to remove this range ambiguity by changing the PRI during the time-on-target. With different PRIs, the target will appear at different ranges. Using a proper logic, it is possible to identify the echo as a second-time-around one, and assign to it the proper range. As a general rule, use of n different PRI allows to solve up to nth-time around echoes (normally, 3 or 4 are used). It is possible to change the PRI at each transmitted pulse, but, generally, in modern radars using “packet” processing, they are changed on a packet basis (some tens of pulses). Note that many modern air-search radars
