RADAR A NTENNA S 221 



Radar antennas are as numerous in kind as radars. The unique 

 character and particular functions of a radar are often most clearly 

 evident in the design of its antenna. Antennas must be designed for 

 viewing planes from the ground, the ground from planes and planes 

 from other planes. They must see ships from the shore, from the air, 

 from other ships, and from submarines. In modern warfare any 

 tactical situation may require one or several radars and each radar must 

 have one or more antennas. 



Radar waves are almost exclusively in the centimeter or microwave 

 region, yet even the basic microwave techniques are relatively new to 

 the radio art. Radar demanded antenna gains and directivities far 

 greater than those previously employed. Special military situations 

 required antennas with beam shapes and scanning characteristics never 

 imagined by communication engineers. 



It is natural that war should have turned our efforts so strongly in 

 the direction of radar. But that these efforts were so richly and quickly 

 rewarded was due in large part to the firm technical foundations that 

 had been laid in the period immediately preceeding the war. When, 

 for the common good, all privately held technical information was 

 poured into one pool, all ingredients of radar, and of radar antennas in 

 particular, were found to be present. 



A significant contribution of the Bell System to this fund of technical 

 knowledge was its familiarity with microwave techniques. Though 

 Hertz himself had performed radio experiments in the present micro- 

 wave region, continuous wave techniques remained for decades at longer 

 wavelengths. However, because of its interest in new communication 

 channels and broader bands the Bell System has throughout the past 

 thirty years vigorously pushed continuous wave techniques toward the 

 direction of shorter waves. By the middle nineteen-thirties members 

 of the Radio Research Department of the Bell Laboratories were work- 

 ing within the centimeter region. 



Several aspects of this research and development appear now as 

 particularly important. In the first place it is obvious that knowledge 

 of how to generate and transmit microwaves is an essential factor in 

 radar. Many lower frequency oscillator and transmission line tech- 

 niques are inapplicable in the microwave region. The Bell Laboratories 

 has been constantly concerned with the development of generators 

 which would work at higher and higher frequencies. Its broad famil- 

 iarity with coaxial cable problems and in particular its pioneering work 

 with waveguides provided the answers to many radar antenna problems. 



Another telling factor was the emphasis placed upon measurement. 

 Only through measurements can the planners and designers of equip- 



