220 BELL S YS TEM TECH NIC A L JO URN A L 



1 1 . Lobing 274 



11.1 Lobe Switching 275 



11.2 Conical Lolling 276 



12. Rapid Scanning 276 



12.1 Mechanical Scanning 277 



12.2 .\rray Scanning 278 



12.3 Optical Scanning 282 



Part III — Military Radar Antennas Developed by the Bell Laboratories 284 



13. General .' 284 



14. Naval Shipborne Radar Antennas 286 



14. 1 The SE Antenna 286 



14.2 The SL .\ntenna 286 



14.3 The SJ Submarine Radar Antenna 291 



14.4 The Modified SJ/Mark 27 Radar Antenna 294 



14.5 The SH and Mark 16 Radar Antennas 294 



14.6 Antennas for Early Fire Control Radars 297 



14. 7 \ Shipborne .\nti-Aircraft Eire Control Antenna 298 



14.8 The Polyrod Eire Control Antenna '. . 300 



14.9 The Rocking Horse Eire Control Antenna 301 



14. 10 The Mark 19 Radar Antenna 302 



14. 1 1 The Mark 28 Radar Antenna 305 



14. 12 A 3 cm Anti-.\ircraft Radar Antenna 307 



15. Land Based Radar Antennas 307 



15. 1 The SCR-545 Radar " Search" and "Track" Antennas 307 



15.2 The AN/TPS-IA Portable Search Antenna 309 



16. Airborne Radar Antennas 312 



16. 1 The AN/APS-4 Antenna 312 



16.2 The SCR-520, SCR-717 and SCR-720 .Antennas 313 



16.3 The AN/APQ-7 Radar Bombsight Antenna 315 



Introduction 



"O ADAR proved to be one of the most important technical achieve- 

 -'-^ ments of World War II. It has many sources, some as far back 

 as the nineteenth century, yet its rapid wartime growth was the result 

 of military necessity. This development will continue, for radar has 

 increasing applications in a peacetime world. 



In this paper we will discuss an indispensable part of radar — the 

 antenna. In a radar system the antenna function is two-fold. It 

 both projects into space each transmitted radar pulse, and collects from 

 space each received reflected signal. Usually but not always a single 

 antenna performs both functions. 



The effectiveness of a radar is influenced decisively by the nature and 

 quality of its antenna. The greatest range at which the radar can de- 

 tect a target, the accuracy with which the direction to the target can be 

 determined and the degree with which the target can be discriminated 

 from its background or other targets all depend to a large e.xtent on 

 electrical properties of the antenna. The angular sector which the 

 antenna can mechanically or electrically scan is the sector from which 

 the radar can provide information. The scanning rate determines the 

 frequency with which a tactical or navigational situation can be ex- 

 amined. 



