Directional Modulation from a Wrist-Wearable Compact Antenna

This work proposes compact multiport antennas for directional modulation (DM) on wrist-wearable devices to improve the secrecy and privacy of the transmitted data. The DM performance is investigated using the antenna in free-space and with a human forearm-phantom. The system achieves a low Bit Error Rate (BER) < 10⁻¹ with 44° beamwidth, in a unique steerable secure direction over the entire azimuth plane. Full-wave simulations including the phantom at 5 GHz show realized gains of up to 4.26 dBi. The specific absorption rate is below the standard limits, with maximum values of 0.487 W/kg and 1.42 W/kg for the wrist-worn and next-to-mouth conditions, respectively.