Development and characterization of a robust differential wake-up receiver for wireless sensor networks

The basic design of the traditional wake-up receiver implemented by different publications in the last few years is essentially based on a shared radio channel where a low frequency signal (which is modulated on a high frequency carrier, typically close to the 868 MHz ISM band) is transmitted. This signal is modulated using the OOK (On-Off Keying) scheme and later recovered by a passive demodulation circuit. Optionally, the signal may contain a variable length address in order to target selectively the goal nodes. In this new approach, a double wake-up channel is implemented instead of a single one. This is labeled as FSK (Frequency Shift Keying) wake-up receiver (FSK WuRx). Two complementary signals, modulated at different high frequency carriers are recovered and then conducted into a low power difference amplifier with adjustable gain. This component builds a differential wake-up signal that serves to stimulate an ultra-low-power wake-up IC. A proof of concept is carried out first using visible light communications. The resulting FSK WuRx was compared with published designs in the same field. Afterwards, a prototype of the FSK WuRx was constructed using off-the-shelf components. A sensitivity of -61 dBm was achieved by consuming approximately 11.7 μA. Interferer resilience analysis were also carried out and results were compared with an OOK WuRx. Values of the Carrier Interference Ratio (CIR) of -17 dB were achieved for in-band interferers and up to -39 dBm for interferes located in the middle of the two channels. Furthermore, a data rate of 8.1 kbps was obtained.