Patch antenna fed by a 3 line system for dual orthogonal linear and circular polarisation

This paper describes a patch antenna excited by two slots suitable for state of the art multilayer integration. Instead of having two different ports feeding the slots, they form part of a 3-line-system able to guide an even- or odd-mode. It is shown that the even-mode excites a horizontal and the odd-mode a vertical polarisation. Taking into account that any circular polarisation can be composed from two orthogonal linear polarisations, the antenna is proved to be also excitable for left handed and right handed circular polarisation. Feeding the 3-line-system with a MMIC responsible for all amplitude and phase adjustments, thus saving space and cost, makes this antenna attractive for being used in large arrays. The particular antenna is designed for later use in a microwave imaging system centered at 75 GHz.