Microcontroller-Based LoRa Scatter Communication

Long-Range (LoRa) scatter communication has wide coverage, long communication distance, low power consumption, low cost, and a wide application prospect in the field of Internet of things. The key to realizing LoRa scattering communication is to generate a square or sine wave with continuously changing frequency with time as the baseband signal. The existing technical solution is to control the voltage-controlled oscillator (VCO) using an analog-to-digital converter to generate a sine wave with continuously varying frequency. On the one hand, the aforementioned solution is sensitive to environmental changes, such as temperature. On the other hand, the power consumption is relatively large, and meeting the power requirements of passive communication is difficult. Based on the idea of direct digital frequency synthesis, this study proposes a method for generating square wave signals with continuous frequency variation with time using a microcontroller with high frequency stability and low system power consumption. Test results show that the device can realize LoRa scattering communication at any position between the base station and the receiving terminal, which are 210 meters apart, and is compatible with the existing commercial LoRa radio chipset. The standby current at the scattering end is 0.39 μA, and the continuous current during transmission is 140 μA, which reduces the power consumption of the existing active LoRa by three orders of magnitude.