Optimal dimensions of two microstrip patch antennas for low mutual coupling at 5.8 GHz

This paper presents a patch antenna structure with low mutual coupling and good impedance matching characteristics at a 5.8 GHz centre frequency. The structure itself is very simple and contains only two patch antennas on a substrate above a ground plane. Low mutual coupling is achieved by optimizing the dimensions of the patches. The measured -10 dB impedance bandwidth related to the 5.8 GHz centre frequency is 640 MHz and equals a 11.7 % relative bandwidth. Mutual coupling at the aforementioned bandwidth is less than -21 dB. The bandwidth when mutual coupling is less than -20 dB is 950 MHz, corresponding to a 16.4 % relative bandwidth. S11 of the two microstrip patch antenna at the centre frequency is -23.7 dB when mutual coupling is -27 dB. The maximum gain of one microstrip patch antenna in the YZ cut is 10.9 dBi at the measured 5.8 GHz centre frequency. The effect of the ground plane was also studied with simulations to see if it changes the performance of the proposed structure.