Csrrs for Efficient Reduction of the Electromagnetic Interferences and Mutual Coupling in Microstrip Circuits

This paper proposes an efficient microstrip isolator filter which suppresses the surface and lateral waves (SW and LW) in planar antenna arrays. The structure consists in a double or triple row of periodic and flipped array of subwavelength Complementary Split Ring Resonators (CSRRs). The array of CSRRs is etched on a dielectric substrate backed by a metallic ground plane. These structures can both block the electromagnetic (EM) energy in one direction and guide it along the other transverse direction. In particular, the flipped array of CSRRs presents wider bandgap characteristic (stopband ≥20%) than periodic array of CSRRs (~16%) and conventional array of SRRs (≥12%). Then, the metamaterial filter is inserted between two 6.1 GHz probe-fed patch antenna elements separated by a distance of 0.8 λ. Excellent agreements between the simulated and the experimental results are obtained. In fact, a significant reduction of the EM mutual coupling is achieved, more than 24 dB, over a wide frequency bandwidth. Moreover, the proposed CSRR structures are compact, low complex and, as printed antennas, are very easy to manufacture. They have numerous applications in MIMO systems and directive phased arrays.