500 



AUTOMATIC TRACKING CIRCUITS 



system with which the range tracking system must be integrated. The 

 operation of the range tracking system may be described in general terms 

 by considering the functions of each element — time discriminator, time 

 modulator, and transmission shaping unit — and the essential features of 

 their closed-loop operation. 



Time Modulator and Time Discriminator. ^o These units provide 

 a means for generating a range error signal. They accomplish this by 

 dividing the video signal to be tracked into an early part and a late part 

 and comparing the energies in each part to develop a voltage proportional 

 to range position error. Two methods commonly employed for these 



1. Original Video 



Signal 



2. Undelayed 



Gate 



3. Doubled" Video 

 Signal 



4. Delayed 

 Gate 



Fig. 9-15 Wave forms in a Time Discriminator: (a) Double Signal Type, 

 (b) Split Gate Type. 



A 



I 



Delay Line 



Fig. 9-16 Double Signal Time Discriminator. 

 20See Guidance, Par. 10-31, which forms the basis for this discussion. 



