GB1174315A - Improvement relating to Electronic-Scanning Antennas - Google Patents

Abstract

1,174,315. Aerials. THOMSON-CSF. 8 Sept., 1967 [21 Sept., 1966], No. 41228/67. Heading H4A. In a scanning aerial array a plurality of radiating elements are distributed over a spherically-shaped surface and are connected to the nodal points of a network formed by two intersecting groups of lossy feeders. The electrical length of a section of feeder between any two adjacent radiating elements is approximately a whole multiple (k) of the operating wavelength (#) of the aerial. A switching system allows any one of a predetermined group of the radiating elements to be connected to a source, i.e., a transmitter or a receiver. As described, radiating elements 1À1, 1À2 ... 8À3, 8À4, &c., Fig. 1, are disposed at the intersections of the meridians and parallels of latitude of a sphere, and are connected by lossy feeders 1001, 1002 &c., of a first group and 2001, 2002 &c., of a second group. When an element is excited by direct connection to the source, energy is also fed through the lossy feeders to surrounding elements, but because of attentuation in those feeders radiation is negligible except for elements in the immediate vicinity of the directly excited element. A small area of radius a, Fig. 2, on the spherical surface is thus activated, and the elements therein function as a sub-array radiating along the radius X. In order to compensate for the displacement of elements away from the centre O of the tangent plane yy<SP>1</SP>, and thereby reduce side lobes in the radiation diagram, the electrical lengths of sections of feeders between consecutive elements may be made equal to k#-#, where 8 is a quantity small relative to #, and for which a formula is given. A two-stage switching system is described in which the source is first connected by a main switching unit to one of a plurality of subsidiary switching units, each of the latter units being associated with the radiating elements distributed along a particular meridional feeder (Fig. 4, not shown). Switching units comprise cascade arrangements of two-way switches, which may be switching diodes (Fig. 5, not shown).