Daughter board antenna for compact polarization diversity on MIMO devices

Orthogonal linear polarizations offer a practical and compact approach to antenna diversity, but for wireless devices realized on small printed circuit boards (PCBs), the cross-polarized antennas are spaced apart as well, in order to increase the isolation. An approach is presented here that uses a daughter board to support an element which is essentially co-located with a standard antenna printed in the PCB. The advantage is the high isolation in a compact space. It also offers a third polarization component for PCBs that already support two orthogonal elements. It can therefore be used as a retrofit to an existing PCB wireless system, in order to deploy diversity/MIMO, or deploy an increased order of diversity/MIMO.