Low Mutual Coupling Between Monopole Antennas by Using Two $\lambda /2$ Slots

A simple structure for achieving low mutual coupling between two monopole antennas at 2.45 GHz center frequency is studied. The structure has two half-wavelength slots cut into the ground plane between the monopoles. The lowest mutual coupling is between -54 and -35 dB, depending on the studied structure. In comparison, mutual coupling using the reference ground planes is between -15 and 7 dB. The improvement in measured total efficiencies with the slotted ground plane against the reference ground planes is between 2.8 and 24.3%.