DIRECTIVE DIAGRAMS OF ANTENNA ARRAYS 293 



These early suggestions have been followed by a number of more 

 complicated arrangements proposed by Braun,'' Bellini,^ and others.^ 



Most books on radio communication contain one or more directive 

 diagrams showing the variation of either the amplitude or the energy 

 for systems of two, three, or four antennae which are separated by 

 given fractions of the wave-length and with currents which have 

 assigned amplitude and phase relations. Bellini,^ Koerts,^ and 

 7enneck ^ each give about a dozen such diagrams. Recently, Green ^^ 

 and Friis " have published directive diagrams for a pair of loops; the 

 latter gives a curve obtained experimentally which agrees very well 

 with the theoretical curve. Of the published diagrams, one of the 

 most extended and systematic sets appears to have been that of 

 Walter.^^ He showed a total of 21 diagrams for arrays of two an- 

 tennae, with the three separations of 1/10, 1/4, and 1/2 wave-length 

 and the seven phase differences of 0, 1/12, 1/6, 1/4, 1/3, 5/12, and 

 1/2 period. 



In the present paper an effort has been made to present a more 

 systematic and comprehensive collection of directive diagrams for 

 arrays consisting of 2 and of 16 antennae, respectively, spaced at 

 equal distances along a straight line or axis, with currents of equal 

 amplitude in all the antennae, and with equal phase differences in- 

 troduced between the currents in adjacent antennae. These diagrams 

 are polar diagrams showing the relative amplitude of the field of the 

 radiation at a great distance in a plane through the array, assuming 

 that each antenna radiates equally in all directions in this plane. 

 The unit circle shown in each diagram represents the amplitude of the 

 radiation if all the antennae were made coincident in space and in 

 phase. 



These directive diagrams may be used to obtain the directive 

 diagram in any plane through an array made up of antennae which 



^F. Braun, Electrician, 57, pages 222-224, 244-248, 1906. 



5 E. Bellini, Electrician, 74, pages 352-354, 1914. 



" For extensive bibliographies see L. H. Walter, Directive Wireless Telegraphy, 

 London, 1921, pages 119-121; H. H. Beverage, C. W. Rice, and E. W. Kellogg, 

 Journal of the A. I. E. E., 42, pages 736-738, 1923; A. Koerts, Atmosphiirische 

 Storungen in der drahtlosen Nachrichtenubermittlung, Berlin, 1924, pages 149, 

 150; J. Zenneck and H. Rukop, Drahtlose Telegraphic, fifth edition, Stuttgart, 

 1925, Chapter XIII. 



^ E. Bellini, Jahrbuch der drahtlosen Telegraphic und Telephonic, 2, pages 381- 

 396, 1909. 



8 A. Koerts, loc. cit., pages 101, 102, 104, 105, 110, 111, 130, 131, 133. 



9 J. Zenneck and H. Rukop, loc. cit., pages 412-415, 419, 421, 423, 428, 432. 



10 E. Green, Experimental Wireless, 2, pages 828-837, 1925. 



11 H. T. Friis, Proceedings of the I. R. E., 13, pages 685-707, 1925. 

 1-^ I.. H. Walter, Electrician, 64, pages 790-792, 1910. 



