Printed multi-band compound meta-loop antenna with hybrid-coupled SRRs

A novel printed loop antenna with hybrid-coupled split ring resonators (SRRs) is proposed to realise multi-band and impedance-enhanced performances. Design guidelines and a step-by-step derivation of the proposed antenna based on SRRs are given in detail. On the basis of a one-wavelength rectangular loop, by splitting the left-/right-hand sides of the loop, the input impedance of the loop antenna is reduced and an additional resonance can be generated. Four identical SRRs are then symmetrically placed inside the loop, which not only introduces a resonance by the electrically small SRRs array, but also forms multiple hybrid resonances at the high frequencies. To improve impedance matching, two parasitic strips are added besides the splits of SRRs. This antenna is numerically and experimentally studied. It is demonstrated that this antenna achieves three operating bands with improved impedance matching (i.e. two narrow-bands at 0.729 and 0.797 GHz and a wide band from 0.935 to 1.1 GHz), a loop-dipole-liked radiation pattern, a maximum realised gain with a value of 4.8 dBi and radiation efficiency above 72.5%.