432 REGULATORY CIRCUITS 



transformations. These will be discussed later in the example of a detailed 

 search stabilization design for an AI radar. 



Tracking Stabilization. During tracking, information from the 

 target can be employed to position the antenna. As described in Chapter 6, 

 various techniques such as conical scan or monopulse can be used to create 

 an error signal which indicates the amount of error between the line-or-sight 

 and the antenna pointing direction. Generally, however, the stabilization 

 provided by the radar angle tracking control is not sufficient: a faster, 

 tighter inner stabilization-control loop must be used to provide the neces- 

 sary isolation from aircraft motions. 



A basic tracking radar stabilization system is shown in Fig. 8-25. ^^ Xhe 

 outer control loop represents the generation of the automatic angle tracking 



Aircraft Disturbance 

 Inputs 



Antenna 

 Drive 



G2 



An 



G,h- 



Aircraft 



Maneuvering 



Inputs 



^''-[^g,g,\g,g^P'\i + 



Gi Go+ Go G 



Fig. 8-25 Basic Tracking Radar Stabilization System. Jls = sight target line; 

 Et = angular error signal; Jtl = stabilization feedback; G3 = rate-measuring 



device (gyro). 



error signal. The design considerations for such control loops are covered 

 in Chapter 9. Stabilization is provided by measuring the space angular rate, 

 Atl, of the antenna and feeding this signal into the antenna drive as shown 

 in Fig. 8-25. This arrangement yields the interrelations among antenna 

 pointing direction line-or-sight inputs and aircraft motions, shown. 



If the gain of the control loops, the products of G1G2 and G2G3, are much 

 greater than unity for frequencies greater than those inherent in the line- 

 of-sight angle Jls and the aircraft space angle Ja, the equation in Fig. 8-25, 



Atl 

 becomes 



r GjG 



+ G2G, 



^h.s + 



1 + G1G2 + G2G; 



•^TL 



(gttg;) '^''' 



l^Variations of this system are discussed 



GolG, + G3) 



Paragraph 8-31. 



.^.., 



^..1 (8-25) 



(8-26) 



