GB1423063A - Scannable antenna array - Google Patents

Abstract

1423063 Aerials NATIONAL AERONAUTICS & SPACE ADMINISTRATION 13 June 1973 [15 June 1972] 28231/73 Heading H4A A system for scanning a ring-shaped array of aerial elements in which a segment of elements is energized and elements are switched into the leading edge of said segment while elements are switched out of the trailing edge, comprises means for gradually introducing power into an element on the leading edge while gradually removing power from an element on the trailing edge. In an embodiment, a spin-stabilized space satellite 40, Fig. 1, has a cylindrical aerial array 41 disposed about its axis, a beam from which is electronically despun so as to remain directed at the earth. The array comprises 32 panels each containing a four-unit sub-array. Each unit has two parallel folded active dipoles and two directors, which are mounted on a mast disposed perpendicularly to the panel surface (Fig. 2, not shown). Said surface acts as a ground plane, and the four units of each sub-array are connected together for feeding in common. The satellite spins at 100 r.p.m. and a segment of five sub-arrays is energized. The angle between adjacent sub-arrays is 11“ degrees and as each advances towards the plane containing the satellite and earth axes, it is switched in when 28# degrees therefrom. Simultaneously, another sub-array, which is 28# degrees from said plane on the other side, is switched out. Power is then uniformly increased in the advancing sub-array from 0 to 5 watts over 11“ degrees. Simultaneously, power is uniformly reduced from 5 to 0 watts in a corresponding array on the receding side (Figs. 3, 4, not shown). A transmitter 50, Fig. 5, supplies power to selected sub-arrays through a four-way divider 51, amplifiers 52 to 55, and diplexers 56 to 59, to variable power dividers 60 to 63, each of the latter being associated with a respective two of eight single-pole four-throw (SP4T) switches 65 to 71. Each power divider has two outputs and its input may be shared between them in any proportion. The power dividers and the switches are controlled by attitude determination and aerial control circuits 72. The SP4T switches each comprise four PIN diodes which are connected in parallel to a common input, and which have separate outputs. The diodes are normally non-conductive, but can be individually biased to be conductive (Fig. 6, not shown). In the variable power dividers, two varactor diodes couple two hybrids. By appropriately biasing the varactor diodes an input to one hybrid appears in desired proportions at two outputs at the other hybrid (Fig. 7, not shown). Application to sonar scanning is mentioned.