Low profile pattern switchable multiband antenna for on/off body communication

A low profile, a multifrequency microstrip patch antenna with pattern reconfiguration is reported in this paper. The proposed antenna provides both omnidirectional and directional radiation characteristics suitable for Wireless Body Area Network (WBAN). Pattern switching is achieved using PIN diodes. The antenna is designed to operate at multiple frequencies, viz. 0.915 GHz (Industrial Scientific & Medical band), 2.38 GHz (Medical body area network), 3.5 GHz (Wireless Interoperability for Microwave Access), and 5.8 GHz (Wireless Local Area Network/Industrial Scientific & Medical band). The percentage bandwidths obtained are 2.89, 1.68, 2.85, 2.16 at the operating frequencies 0.915, 2.38, 3.5, 5.8 GHz, respectively. The peak gain and total efficiencies obtained for OFF mode are 3.22/4.27/4.65/4.82 dBi, 82/85/87/89%, and in ON mode are 1.12/1.80/2.44/2.68 dBi, 65/67/71/74% at the said operating bands, respectively. The path loss model is evaluated by measuring the transmission link between the antennas on the human body. The LOS path ranges from 30 to 45 dB and the NLOS ranges from 50 to 80 dB ensuring it satisfactory for WBAN application. Then human body loading characteristics are also studied. The SAR analysis is performed and it is found to be less than 1.6 W/Kg.