Part II
Radar Location Systems
A key moment at arrangement of radar systems is a selection of processing principle
based on phase dependences of radiated and reflected radio signals. In this connection,
the coherent and non-coherent radars are distinguished.
Oscillations are called coherent during a certain time interval, if there is a functional relation of some part of oscillation with its any another part. Otherwise, the
oscillations are non-coherent. For two harmonic oscillations, coherence is achieved
in case if phase difference between them on a certain interval remains constant.
As for pulse radars—if initial phase of radio pulses in a sequence is constant or
is changed according to the known law, then such a sequence is coherent, and if a
variation law is random, then a sequence is none-coherent.