Transparent and flexible antenna with omnidirectional circular-polarization reconfigurability for on-body communications

Aiming at the requirements of on-body communications and complex on-body application scenarios in wireless body area network (WBAN), a transparent and flexible wearable antenna with omnidirectional circular polarization (CP) is developed, based on the dielectric resonator (DR) loaded with an equivalent current loop. And, the reconfiguration of CP is further implemented. Radiated electric field components of E_θ and E_φ are generated by the TM_01δ mode of the cylindrical DR and the loop current of the grounded L-shaped branches, respectively. Omnidirectional CPs are realized when the two components are equal in magnitude but differ in phase by 90\text° . The proposed antenna can be switched between left- and right-handed circularly polarized omnidirectional radiations through mechanical rotation, with –10-dB impedance bandwidth covering the 5.8 GHz Industrial, Scientific, and Medical (ISM) band. The 3-dB axial ratio (AR) bandwidths at 5.8 GHz of two states are 10.9% and 10.8%, respectively. The DR and grounded branches are constructed of polydimethylsiloxane (PDMS) and conductive mesh fabric, respectively. The radiation efficiencies of 59% and gains of 2.6 dBic are enabled, together with the advantages of comfort, transparency, and concealment. And, the 3-dB AR beamwidth in the θ = 50° plane achieves a full coverage of 360\text° . Antenna prototypes were fabricated with the aid of 3D printing technology and the proposed design was verified through tests.