Design of reducing mutual coupling in between two closely spaced dual-frequency antennas based on combined electromagnetic soft surfaces

In this paper, two closely spaced dual-frequency antennas are developed using the combined electromagnetic soft surfaces loading techniques for reducing their mutual coupling. The dual-frequencies antenna is designed and its return loss is less than − 10 dB at 4.1 GHz and 5.65 GHz. The electromagnetic soft surfaces are realized by metal strips with C-shaped slots, which have variable working frequency with unit size changing. The dual-band electromagnetic bandgap can be obtained by combined with two electromagnetic soft surfaces with various cell sizes. Experimental results are presented and compared to numerical simulations, and they demonstrated that the proposed electromagnetic soft surfaces loading advance excellent suppression of electromagnetic coupling and the coupling decrease about 16 dB and 19 dB near the working frequencies, respectively. Furthermore, the return loss of the dual-frequencies antennas with this technique is further reduced at its working frequency bands. Measured data show a reasonably good agreement between the simulation and experimental results.