34 ELEMENTS OF AIRBORNE RADAR SYSTEMS DESIGN PROBLEM 



to the previously established requirements. Often, it is found that the 

 requirements are not compatible with realizable radar systems. This 

 discrepancy may be corrected in some cases by using the interrelation- 

 ships of the radar and the overall system derived in the previous phase to 

 find a different balance of radar requirements that will still permit mission 

 accomplishment. In other cases, a known degradation in performance — 

 relative to the initial weapons system goal — may have to be accepted. 

 A somewhat happier situation arises when it is found that a realizable radar 

 system can provide greater capabilities than those required by the initial 

 weapons system concept and operational requirement. In this case, the 

 initial system concept could be enlarged and improved or, conversely, the 

 development objectives could be revised with a resulting economy of design. 

 The indicated processes of evaluation and feedback are shown in Fig. 

 1-24. The flexibility achieved by the feedback process is the real strength 

 of the systems approach. There are few weapons systems that cannot 

 benefit from modification of the originally established concepts and tech- 

 nical requirements. Circumstances change — often in a highly unpre- 

 dictable manner — over the five-to-ten-year development period of a 

 weapons system. That is why the radar designer must continue to treat 

 this problem on an overall weapons system basis throughout the life of 

 the project. 



Equipment Development, Evaluation, and Use. Similar com- 

 ments concerning the value of the systems approach apply to the vitally 

 important task of building, evaluating, and using the equipment in accord- 

 ance with the requirements derived in the first three phases. The problems 

 in the latter phases can be formidable. For some perverse reason the actual 

 equipment in certain critical areas may not perform in the manner pre- 

 dicted, particularly with respect to reliability. A vital part of the system 

 approach is the process of rapid isolation and correction of system deficien- 

 cies in these phases and the anticipation of potentially critical areas. 

 Since it is often difficult to distinguish between a genuine system deficiency 

 and a temporary bottleneck, the judgment and experience of radar systems 

 engineers who have also participated in the requirements derivation phase 

 is most important. There are so many problems in these phases that it 

 is easy to concentrate effort on the wrong ones. 



One problem — reliability — dominates these last phases. This is the 

 most vexing, most difficult, and most important problem in the design of a 

 radar system. Radar systems have never been simple; in the future, their 

 complexity may be expected to increase. The most common failure of the 

 systems approach to the radar design problem has been the tendency to 

 maximize system capability by specifying unnecessarily exotic radar 

 requirements which lead to reliability problems in the mechanization phases. 



