224 BELL S YSTEM TECH NIC A L JOURNA L 



sometimes paraboloids similar to those used in searchlights (Fig. 3). 

 Sometimes they were parabolic cylinders as in the Mark III, an early 

 shipl)orne fire control radar developed at the Whippany Radio Labora- 

 tory. 



From these relatively simple roots, the communication antenna, the 

 electromagnetic horn and the optical reflector, radar antennas were 

 developed tremendously during the war. That this development in 

 the Bell Laboratories was so well able to meet demands placed on it was 

 due in large part to the solid foundation of experience possessed by the 

 Research and Development groups of the Laboratories. Free inter- 

 change of individuals and information between the Laboratories and 

 other groups, both in the United States and Great Britain, also con- 

 tributed greatly to the success of radar antenna development. 



Because of its accelerated wartime expansion the present radar an- 

 tenna field is immense. It is still growing. It would be impossible 

 for any single individual or group to master all details of this field, yet 

 its broad outline can be grasped without "difficulty. 



The purpose of this paper is two-fold, both to provide a general dis- 

 cussion of radar antennas and to summarize the results of radar antenna 

 research and development at the Bell Laboratories. Part I is a dis- 

 cussion of the basic electrical principles which concern radar antennas. 

 In Part II we will outline the most common methods of radar antenna 

 construction. Practical military antennas developed by the Bell 

 Laboratories will be described in Part III. 



The reader who is interested in general familiarity with the over all re- 

 sult rather than with technical features of design may proceed directly 

 from this part to Part III. 



PART I 



ELECTRICAL PRINCIPLES 



1. General 



Radar antenna design depends basically on the same broad principles 

 which underlie any other engineering design. The radar antenna designer 

 can afford to neglect no aspect of his problem which has a bearing on the 

 final product. Mechanical, chemical, and manufacturing considerations 

 are among those which must be taken into account. 



It is the electrical character of the antenna, however, which is connected 

 most directly with the radar performance. In addition it is through atten- 

 tion to the electrical design problems that the greatest number of novel 

 antennas have been introduced and it is from the electrical viewpoint that 

 the new techniques can best be understood. 



An antenna is an electromagnetic device and as such can be understood 



