Performance of microstrip loop antenna arrays

A number of mobile satellite systems are proposed for service in the late 1990s. A study of concentric annular ring arrays is reported in which the rings are excited in various modes, resulting in toroidal beams pointing at different elevation angles. Switching between modes can provide a degree of beam steering. The gain of a single patch was 5-7 dB typically. However, this was found to be sensitive to the size of the ground plane on which it was mounted and this variation in gain has been investigated. A theoretical study is presented of a 4 element stacked array of concentric ring elements in which a degree of beam steering is attained by switching modes