Electrically small shorted patch antenna array with switchable radiation patterns for indoor messaging system

A planar antenna array with switchable radiation patterns is presented for an indoor messaging system (IMES) transmitter. The antenna array comprises four electrically small shorted patch antennas, and can switch the radiation patterns between vertical and horizontal modes. The antenna properties were examined by performing theoretical calculations and experiments. A fabricated antenna array on a printed circuit board is as small as 124 mm by 124 mm, and the measurements demonstrate that two radiation patterns of vertical and horizontal modes are obtainable. We believe that the antenna array should improve the usability of the IMES transmitter.