482 



AUTOMATIC TRACKING CIRCUITS 



The last part of Fig. 9-2, (c), represents the system discussed most often 

 in this text. In this system, the antenna is automatically directed toward 

 the target by the radar error signal, and the aircraft is flown toward the 

 future target position with commands computed from the measured 

 antenna position and velocity. 



The design of each is developed from primary system error requirements 

 and knowledge of the inputs such as those discussed in Paragraph 9-3. 



To illustrate the design considerations, a system similar to Fig. 9-2(c) 

 with a conical scan radar and rate gyro feedback will be discussed.^ 



Control System Diagram. It is necessary to obtain the required 

 functions of antenna angular position and sight line space rates in two axes 

 since the antenna motion is to be controlled mechanically in two orthogonal 

 axes. This necessitates two separate control channels. Fig. 9-3 is a block 



A IS 



?iilh 



ft 



Radar . , . , 



f -• I NpI Att 



^ 



u 



Fig. 9-3 General Block Diagram of Angle Tracking Configuration, One-Channel. 



diagram of a typical control system for one channel. The two channels 

 have duplicate components with the possible exceptions of Kr and K^y 

 the radar and demodulator^, which are usually common to the two channels. 

 Because of the similarity between the two channels, only one channel will 

 be described. 



As discussed previously, the radar signal contains space error information 

 for both channels; it may be obtained from a rotating antenna feedhorn. 

 It appears as suppressed carrier modulation at the output of Kr, the radar 

 receiver. The rest of the diagram can be subdivided into three loops: 

 (a) search loop, {^) stabilization loop with a rate gyro, and (c) track loop. 



The search loop has been described in Paragraph 8-26, but is included 

 here to show that some of the track circuits not in use during the search 



gn principles could be applied to any of the configurations shown 



''Actually, many of th 

 in Fig. 9-2'. 



^In many systems a different demodulator is used in the search loop 

 later is shown in this figure. 



A common demodu- 



