A Helmet-Based Hemispherical-Conformal Wearable Array Antenna with Broad Bandwidth, Wide-Angle Coverage and Reconfigurable Dual Circular Polarizations for WBAN Applications

This paper presents a helmet-based hemispherical-conformal wearable array antenna with broad bandwidth, wide-angle coverage and reconfigurable dual circular polarizations (CPs) that is suitable for wireless body area network (WBAN) applications. First, a broadband and polarization-reconfigurable conformal radiating element is designed, which features a single-feed reconfigurable crossed dipole incorporated with parasitic patches above a ground plane for attaining unidirectional radiations. By integrating four PIN diodes on four arms of the crossed dipole, the element can flexibly switch its polarization states among two orthogonal CP modes. Four sector-shaped parasitic patches placed in four quadrants of the crossed dipole help to expand the operating bandwidth. Furthermore, we design a 12-element helmet-based hemispherical-conformal polarization-reconfigurable wearable array that is arranged in special configuration for increasing the gain, coverage range and orientation flexibility for WBAN systems. The measured results show the proposed conformal wearable array exhibits an overlapped 3-dB axial-ratio bandwidth of up to 29.6% and -10-dB impedance bandwidth of 69.8% at around 3 GHz for two reconfigurable CP modes. Besides, it has a relatively wide beam coverage range of 110° × 360 ° and a peak measured gain of more than 8 dBi for both polarization modes.