Optimum Excitations for a Dual-Band Microwatt Wake-Up Radio

To enable pervasive exploitation of wireless sensor networks (WSNs), semi-passive wake-up radios (WuR) are proposed to minimize the active time of the energy-hungry main communication radio. The most challenging feature is to enhance their sensitivity, the weakest activation signal the receiver is able to sense, that is limited by the minimum turn-on voltage of diode-based detector. In order to operate the detector at even lower power levels, a strategy to optimize the modulated WuR excitations is presented, exploiting high-peak intermittent continuous waves (ICW), while preserving the required average power per bit. The design and implementation of an ultra-low-power detector, fed by a dual-band antenna and loaded by the WuR back-end is presented: 2.45-GHz and 868-MHz operations of the same WuR are demonstrated, with added flexibility and interoperability among different communication bands. We show that a correct WuR activation is possible with an average power per bit as low as -63 dBm at 2.45 GHz and -65 dBm at 868 MHz. This is experimentally verified by a lab-level set-up and confirmed by a system implementation based on off-the-shelf components only.