9-9] 



ANGLE TRACKING LOOP MECHANIZATION 



497 



Transfer Function 



Pk> i o , 



- s2CjC2RiR^+.(C2Ri+C2R,+ Ci/!j) + i where R^= Ro(l+Kj 



Frequency Characteristic 



Design Formulas 



Let Ro= 1 (Resulting Values May be Adjusted to Any 

 Impedance Level) 



Flow Diagram 



Then: C,= 7j- + ,- 



'^1 cJcJ^ co.icj) 

 <^r R,c,co,u, 



Fig. 9-13 Active RC Tracking Network. 



General Design Considerations. In general, considerable care must 

 be used in designing the track loop circuits. Proper grounding and shielding 

 must be utilized to minimize ground loops and induced noise. Attenuation 

 and transfer function modifications due to impedance loading must be 

 considered, especially in the summing networks where the gyro rate signal 

 is added to the track loop. Adequate dynamic range must be provided in 

 the amplifier to minimize the possibility of producing grid current and 

 saturation due to large signal and noise inputs, especially during transient 

 operation. It may be necessary to place Zener diodes across large capacitors 

 to prevent voltages from accumulating at times when large step inputs are 

 applied. At the stabilization summing point, a voltage sufficient to balance 

 the large gyro voltage resulting from maximum antenna rates must be 

 available from the angle track circuits. 



Finally, the tracking loop must be constructed and evaluated. This 

 cannot be done satisfactorily until the actual antenna is constructed and 

 used in the loop; ideally the measured antenna characteristics should be 

 available in the initial design stages of the stabilization loop. After con- 

 struction, the antenna performance, essentially its tracking accuracy, must 

 be measured. Usually, as the result of preliminary measurements on the 

 component parts of the system, the design may have to be modified to 

 obtain the transfer functions desired. In airborne equipment it is important 

 to measure the track loop performance over wide ranges of environment — 

 pressure, temperature, and vibration. 



The physical design problems associated with each high-performance 

 antenna tracking loop, including its stabilization loop, vary with different 



