Ultra-low Power LoRa Wake-up Mechanism Based on Analog Spread Spectrum Signal Processing

‍ ‍In a large-scale IoT system based on LoRa （Long Range Radio）， in order to reduce the communication delay with low power consumption while being close to the communication distance of the LoRa system， a LoRa wake-up mechanism based on low-power down-conversion and an analog dechirp mechanism is proposed. Firstly， a standard LoRa preamble sequence and a single-tone carrier with a certain frequency are sent out using the transmitter. Secondly， after the antenna of the receiver receives both the preamble sequence and the carrier wave， the non-linear effect of the Schottky diode is used to complete the mixing of the two signals， i.e.， the single-tone carrier wave acts as the local oscillation signal and achieves the down-conversion of the LoRa signal. Then the on/off timing of the RF switch is controlled to complete the demodulation of the received signal. Finally， baseband processing is performed on the demodulated signal to reduce the SER（Symbol Error Rate） using two quadrature signals. Theoretical analysis and simulation results show that the ultra-low power wake-up mechanism based on analog spread spectrum signal processing proposed in this paper is feasible in LoRa systems， with a reception sensitivity of -136 dBm and an overall power consumption of only 137 μW.