6-6] 



PULSED-DOPPLER RADAR SYSTEMS 



321 



and time-duplexing properties of a pulse radar. For applications requiring 

 heavy ground clutter rejection, a common transmitting and receiving 

 antenna, and accurate range measurement, a pulsed-doppler type of system 

 represents the best known technical approach to the problem. However, 

 the pulsed-doppler type of system also has certain drawbacks: principal 

 among these are limited target-handling capacity (when compared with a 

 pulse radar) and a high order of electronic system complexity. 



Basic Principles of Operation. A simple pulsed-doppler system is 

 shown in Fig. 6-20. It differs from the CW system of Fig. 6-14 only by the 



Fig. 6-20 Simple Pulsed-Doppler System. 



introduction of a pulsed coherent transmitter in place of a CW coherent 

 transmitter; and a duplexer which turns off the receiver during a pulse 

 period and isolates the receiver from the transmitter during the interval 

 between pulses. A master frequency control is utilized to control the carrier 



\^T^ 



^ f^l/fo 



Vfr ^ 



(a) 



-^frr 



fn-lA 



(b) 



Frequency 



Fig. 6-21 Transmitted Pulsed-Doppler Signals. 



