Mutual Coupling Suppression Between Two Patch Antennas Using the Common/Differential Mode Theory

An enhanced decoupling technique between two patch antennas is proposed in this letter based on the common-mode (CM) and differential mode (DM) theory. Two symmetrical antennas theoretically proved that if the impedances of CM and DM are the same, the mutual coupling effect between the separate antennas can be eliminated. Two parasitic patches are located above two identical patches spacing with 0.231 λ₀, making the operating bandwidth cover the Sub-6 GHz n78 band (λ₀ is the free space wavelength of 3.5 GHz). By embedding two decoupling strips and etching one slot on the ground, the CM and DM curves in the Smith chart can be independently controlled and finally overlap. The designed antenna has a relatively low profile of 0.135 λ₀. The experimental results show that the impedance bandwidth of -10 dB is 3.28–3.83 GHz (15.47%), the port-to-port isolation is more than 38.9 dB, and the peak realized gain is 7.69 dBi. Therefore, the measured results agree with the simulated, and the fabricated prototype is a promising candidate for the 5G New Radio n78 communication terminals.