The orthogonal mode of an aperture coupled rectangular microstrip ante
nna can be coupled to the aperture-excited mode with coplanar microstr
ip lines to provide a compact circularly polarised element with a Sing
le aperture feed. An equivalent circuit model was developed for the an
alysis and design of this element, and a working version was used to d
emonstrate the concept. The features of this antenna are compared with
several other circularly polarised microstrip antennas.