Low-profile circularly polarised loop antenna assisted with an effective PMC bandwidth

Proposed is an ultra-low-profile loop antenna backed by an electromagnetic bandgap (EBG) surface reflector, where the EBG surface can effectively exhibit the property of a perfect magnetic conductor (PMC) inside a deliberately designed bandwidth. It is shown that, assisted by the effective PMC bandwidth, while the proposed antenna is with a 0.07-λ spacing between the loops and the EBG reflector, its axial ratio (AR) and voltage standing wave ratio (VSWR) performances are significantly improved. Experimental measurements show that the prototype antenna has a 3 dB AR bandwidth of 17% with an input VSWR less than 1.6. The proposed approach can find a wide range of low-profile circularly polarised (CP) antenna applications.