Flexible Fractal Electromagnetic Bandgap for Millimeter-Wave Wearable Antennas

This letter presents a novel design of a uniplanar compact electromagnetic bandgap (EBG) for millimeter-wave wearable antennas. The unit cell of the EBG has a flexible fractal design with self-similar window-like structure, which can be easily fabricated at millimeter scale. The fabricated EBG is a 3 x 3 cell array laser-cut from adhesive copper foil on polyester fabric substrate. Results show that the gain and -10 dB bandwidth of a wearable coplanar waveguide (CPW) antenna backed by the proposed EBG are improved by 3 dB and 40%, respectively, across the frequency range from 20 to 40 GHz. Backward radiation is also decreased by 15 dB, significantly reducing the potential health risk posed by the radiating antenna to the human wearer. Furthermore, on-body measurements show that the CPW-EBG antenna performances are not highly sensitive to human body proximity.