Slot-coupled back-to-back microstrip antenna with an omni- or a bi-directional radiation pattern

A new slot-coupled back-to-back microstrip antenna is proposed. Two rectangular patches are arranged relative to a slot on the ground plane. The proposed microstrip antenna has an omnidirectional or a bi-directional radiation pattern in the horizontal plane. The characteristics of the proposed antenna were clarified by experiments. The input impedances and radiation patterns were measured as a parameter of the length of various slots. Good input impedances and radiation patterns were obtained. The mechanism to realise these radiation patterns was clarified by using an electromagnetic simulator. The application of the proposed antenna to obtain a circularly polarised bi-directional radiation pattern is also described