Microstrip Linear Array for Polarisation-Agile Antenna Applications

A new configuration of the rampart line microstrip array is described that allows arbitrary polarisation to be obtained from the same basic geometry. The line consists of a periodic arrangement of right angle bends in a microstrip line, each period containing six bends. A first order design method is presented that allows both the required polarisation and power radiated per period to be synthesised. The increased design freedom provided by this configuration has allowed an array, polarised at 45°, with aperture tapering to reduce sidelobes, to be produced. A pair of these arrays is used to form a polarisation-agile linear array useful in radar applications where such agility allows enhanced signal to clutter or jamming ratios to be achieved. The performance obtained from this array is given for circular, vertical and horizontal polarisations, and it is concluded that reduced sidelobe levels may be possible at the expense of reduced efficiency.