Switchable ON-/OFF-Body Antenna for 2.45 GHz WBAN Applications

Abstract

A switchable ON-/OFF-body antenna operating at the same frequency of 2.45 GHz industrial, scientific, and medical (ISM) band for wireless body area network (WBAN) applications is presented. P-i-n diodes are chosen to act as the switches between ON-body and OFF-body modes with the forward or reverse direct current (dc) voltage. To achieve the same operating frequency at ON-body and OFF-body modes, suitable slots are cut on the radiator to have size reduction at OFF-body mode, and it will have less effect at ON-body mode. Bias circuit is integrated in the antenna. Total size of the antenna is $\pi \times 24^{2}\times 3.2$ mm3. Specific absorption rate (SAR) value is also analyzed in this communication. Then, the antenna is fabricated to validate the design concept. Measured radiation pattern of ON-body mode is omni-direction with vertical polarization and OFF-body mode is with broadside, respectively. Communication links of ON-body mode, which assessed by $\vert S_{21}\vert $ and the performance at OFF-body mode, are also studied in this communication.