Design Of Processor-free LoRa Backscatter Communication System

In today's Internet of Things(Io T)applications,the high power consumption of the Io T always restricts the longterm deployment of largescale applications.In the end devices of the Internet of Things,the processors and wireless communication module are major power consumption that drains at the level of milliwatts.For the communication module,the lowpower passive communication method: backscatter communication brings a new solution to the power consumption problem,but its short communication distance greatly limits the scope of application.The LoRa backscatter communication system uses the LoRa signal chirp spread spectrum modulation technology to increase the communication distance of the backscatter,but its system requires a processor module for signal processing and control,and the power consumption is still high.In view of the high power consumption of the processor module in the LoRa backscatter system,this article abandons the processor module from the end devices,and the task originally performed by the processor floats to the gateway for processing,and proposes a processor-free LoRa backscatter Communication system design.The system realizes the ultra-low power consumption terminal design,and has the advantages of LoRa backscatter,and achieves a long communication distance,making largescale and long-term de-ployment applications possible.On the other hand,the processor free design reduces the production cost of the Los Ra backscatter terminal? since the terminal control and access are carried out through the gateway wireless communication,the sensor can be added and unloaded by plugging and unplugging,and it has the characteristics of easy reconstruction?The sensor replacement does not need to change the circuit design,which further reduces the maintenance cost in the later period.The work of this article is mainly divided into two parts:(1)The design of LoRa transceiver.Since the LoRa physical layer specification is proprietary and confidential,there is no official reference or protocol specification as the basis for open source implementation.According to the communication requirements of the processor free end devices,we implemented the LoRa physical layer(coding,mod-ulation,demodulation)modules and PIE modulation modules based on GNU Radio.So that the generated LoRa signal can directly control the end devices,and finally the compatibility experiment and accuracy experiment were carried out on the transceiver.(2)The design of processor free end devices.In the downlink communication,the conversion circuit from LoRa signal to baseband signal and baseband signal to bus signal is realized.In the uplink communication,according to the characteristics of the LoRa signal,a backscatter circuit that can reflect the complete LoRa data packet is realized,so that no special customized receiver is required.Then,the PCB board and FPGA board were used to verify and implement the system prototype.Through experiments and analysis,the communication distance of the downlink can reach 38 meters.When the distance between the transmitter and the terminal is 100 meters,the reflection device is located between the two Normal communication between.The overall power consumption of the design is49.965?W,and the power consumption of the backscatter modulation part is 32.683?W,we realizes a low-power processor free end device using LoRa signal as the excitation signal.