hi,this is fani from india
radars for detecting moving targets only employs delay lines, b'coz the radar should cancel the information receving from clutters(stationary targets)
this can be done in two ways
1)butterfly method
2)delay line cancellors
1st method is not suitable for ppi scopes so we use delay line cancellation
---> the simple working of a delayline based radar is the data from receiver is delayed for one time period and applied to a subtractor circuit to which the other input is actual data with no delay.
---.since the clutter information is constant eventhough it is delayed so it cancels out,so RADAR only detects moving targets
Sorry for the lengthy answer,if u have any doubts in this u can post me:lol: