Ultra-thin EBG backed flexible antenna for 24 GHz ISM band WBAN

An ultra-thin, electromagnetic bandgap (EBG) backed antenna is presented for 24 GHz ISM band wearable applications. The antenna is a slotted bow-tie, with an overall dimension of 0.91λ
0
× 0.84 λ
0
× 0.01 λ
0
, backed by a 5 × 5 element 0.01λ
0
thick EBG structure; it is manufactured on a flexible substrate (ε
r
= 2.2). The performance of the EBG-backed antenna in terms of reflection coefficient and free-space radiation patterns is investigated in scenarios with and without structural bending. It is shown that the integration of the EBG enhances the antenna’s front-lobe gain by 2.6 dB, decreases back-lobe radiation by 12.2 dB, and decreases the specific absorption rate (SAR (1 g)) from > 28 W/kg to <1.93 W/kg, significantly reducing potential harm to the human body. Furthermore, the results show the performance of the EBG-backed antenna is highly insensitive to body proximity, and that its performance is preserved when bent along either axis.