14-17] 



SYSTEM CONSIDERATIONS 



775 



the problems of atmospheric attenuation (see Chapter 4) and the generation 

 of large amounts of power become increasingly difficult. The maximum 

 size of the antenna obviously will be limited for airborne installations. 



Range resolution may be improved by decreasing the pulse length. Here 

 again there is a minimum limit, since the average power transmitted is a 

 direct function of pulse length. Also to be considered in this connection is 

 the altitude at which the system will operate, since the length of the pulse, 

 as projected on the ground, is a function of the radar altitude as shown in 

 Fig. 14-18. The packet dimensions for a typical beamwidth and pulse 



350 



en 250 



200 



Q 150 



o 100 

 < 



Fig. 14-18 Pulse Packet Dimensions. 



RADAR ALTITUDE 



50 



I J_ ^ ^ ^ ' . 



5 10 15 20 25 30 35 40 45 50 55 



SLANT RANGE, 1000 ft 

 Fig. 14-19 — 3-db Packet Dimensions vs. Slant Range. 



