264 



TECHNIQUES FOR SIGNAL AND NOISE ANALYSIS 



frequencies), and has a power density equal to the product of 8 times the 

 signal power and D. The portion of the continuous spectrum corresponding 

 to (c) is triangular, with a width equal to that of the narrow band spectrum 

 and with a power density at zero frequency equal to the product of 8 times 

 the noise power and D. 



5-8 AN APPLICATION TO THE EVALUATION OF ANGLE 

 TRACKING NOISE 



In this paragraph, the techniques developed for tracing signals and noise 

 through radar systems will be illustrated by a discussion of the performance 

 of an angle tracking loop in a pulse radar as a function of the signal-to-noise 

 ratio. A block diagram showing the elements of the receiver composing this 

 angle tracking loop is given in Fig. 5-13. This diagram represents a pulse 



Scanning 

 Reference 



Fig. 5-13 Block Diagram of Angle Tracking Loop Employing Conical Scanning. 



radar with a pencil beam which is conically scanned to generate an angular 

 error signal. 



A signal received from a target which is being tracked will have the 

 following form: 



Received signal = a[\ -\- ke cos (ws/ + f)] cos Wct (pulse modulation) 

 where a = signal amplitude (5-82) 



k = modulation constant of the antenna 

 e = angular error magnitude 

 <p = angular error direction 

 Ws = scan frequency (rad/sec) 

 ojc = carrier frequency (RF or IF, rad/sec). 



