GB1002843A - A linear array antenna - Google Patents

Abstract

1,002,843. Aerials. STANDARD TELEPHONES & CABLES Ltd. Oct. 19, 1962 [Oct. 23, 1961], No. 39657/62. Heading H4A. A directional rectilinear array of N unequally spaced elements fed with the same amount of power and producing a radiation pattern with (x + 1) nulls at angles of # 0 , # 1 , # 2 . . . O x to the normal to the line of the array (x being an integer) is built up by setting up two elements numbered 1 and 2 with a spacing So =#/2 sin # 0 which produces -a pattern with a null in the direction # 0 , adding a first set of two elements numbered 3 and 4 each element of which is spaced in the same sense from a corresponding element (γ-2) of the initial elements by a distance S 1 = #/2 sin # 1 = So/K 2 , where y is the serial number of the element being added and K 2 = sin # 1 /sin # 0 , K 2 being a particular value of the parameter K = sin #/sin # 0 , adding a second set of four elements numbered 5, 6, 7, 8 each element of which is spaced from a corresponding element (γ - 4) by a distance S 2 = #/2 sin # 2 = So/K 3 and so on so that the xth set of additional elements comprises 2<SP>x</SP> elements each of which is spaced from a corresponding element of number (y - 2<SP>x</SP>) by a distance Sx = #/2 sin #x = So/Kx + 1 where K x + 1 = sin #x/sin # 0 . The total number N of elements in the final array is thus 2<SP>x</SP> + 1. If the co-ordinates of the elements numbered 1, 2, 3 . . . are denoted by normalised quantities N 1 , N 2 , N 3 such that N 1 = 0 and N 2 = S 0 sin # 0 /# = ¢ = 1/2K 1 (since K 1 = sin # 0 /sin # 0 = 1) then the relationship between the co-ordinates is given by the following table. Examples of arrays with 16, 32, 16 and 64 elements are given respectively in Fig. 2a and Figs. 6, 8 and 10 (not shown) and the corresponding values of K and the co-ordinates of the elements are listed in tables I, II, III, and IV in the Specification, the resultant radiation patterns being plotted in rectangular coordinates in Fig. 3 and Figs. 4, 7, 9, 11 and 12 (not shown) in the form of intensity versus # or K. In these tables and in Figs. 2a, 6, 8 and 10 the co-ordinates are expressed in normalized electrical degrees such that N 1 = o and N 2 = S 0 sin # 0 /# . 360 degrees = 180 degrees. In tables I and II and Figs. 2a and 6 the elements are numbered in serial order, i.e. the order in which the elements are added, but in tables III and IV and Figs. 8 and 10 the elements are numbered consecutively in accordance with the final positions in the array, such co-ordinates being denoted by P 1 , P 2 , &c. In all cases the resultant arrays are symmetrical about a central point and additional nulls occur at every odd integral multiple of the chosen values of K 1 , K 2 . . . , such additional nulls being indicated in Fig. 3 by dotted circles. Radiation patterns having desired characteristics can be obtained by suitable choice of the values of K 1 , K 2 . . . A two-dimensional symmetrical square array may be formed by arranging a plurality of identical linear arrays parallel to each other, Figs. 5a and 13 (not shown), the spacing between the linear arrays being the same as the spacing between the elements of each linear array. The elements of the array may comprise dipoles or horns, each element may be fed through a separate amplifier, e.g. a travelling wave tube, Fig. 5b (not shown), and the directivity may be varied by varying the relative phases of the signals applied to or derived from the elements.