300 GENERIC TYPES OF RADAR SYSTEMS AND TECHNIQUES 



The signal-to-noise ratio of the target information is derived from various 

 modifications of the basic radar range equation (Equation 3-1). As the 

 examples in the following paragraphs will show, considerable care must be 

 taken in the derivation of an approximate expression for 6" /TV ratio to allow 

 for system losses and vagaries of the receiving system such as sweeping 

 gates, filter sampling times, and postdetection filters. Three factors are 

 basic in determining S jN ratio and these provide a convenient basis for 

 comparing S jN performance of different systems in the same situation (i.e. 

 same operating frequency, search volume, antenna size, and scan speed). 

 They are (1) average power, (2) type of integration (coherent or non- 

 coherent), and (3) effective integration time. 



Information Utilization. The end use of the radar information in a 

 given application constitutes the reference — knowledge of which must be 

 compiled to understand the operation of any given system. The end use 

 requirements for a given application are derived by analyses such as those 

 shown in Chapter 2. Those examples demonstrated a number of different 

 end-use possibilities such as (1) display of radar information for interpre- 

 tation by an operator, (2) coding and transmission to a remote location, 

 (3) weapon direction computation. Other possibilities include (1) storage 

 by photographic techniques, (2) correlation with information from other 

 sensors such as infrared (IR) and photographic, (3) navigation computa- 

 tions. 



The operation of any radar system can be judged only in terms of its 

 compatability with a set of end-use requirements. This fact is often 

 forgotten by people who like to categorize radar systems on an absolute 

 basis. Such people originate statements such as "Pulse radars have no 

 low-altitude capability" and "Doppler radars have excellent low-altitude 

 capability." At best, statements such as these are partial truths; at worst, 

 they are quite wrong in certain applications. The systems designer is well 

 advised to avoid generalizations of this sort and analyze radar systems with 

 respect to their applicability to specific problems. 



6-3 MONOPULSE ANGLE TRACKING TECHNIQUES 



Angle tracking requires measurement of two quantities in a manner that 

 is effectively continuous. These quantities are magnitude and sense of angle 

 tracking error. As shown in Chapter 5, Fig. 5-13, this is accomplished in 

 conventional conically scanning tracking radar by purposely generating 

 instantaneous tracking errors, but alternating the sign of the error, and 

 averaging to zero. The method is simple and effective, but suffers errors when 

 the signal fluctuates in amplitude in such a manner as to increase apparent 



