Research On Radio Frequency Transmission Characteristics Of Wireless Farmland Underground Sensor

Agricultural Internet of Things technology plays a unique and important role in the transition from traditional agriculture to modern agriculture in China.The use of intelligent information management technology has provided an unprecedented opportunity for the development of modern agriculture,and has become one of the hot spots of agricultural development in various developed countries.The use of wireless networks to detect physical quantity parameters such as temperature and humidity in the farmland environment can provide a scientific basis for the monitoring and control of crop growth environment.In this thesis,the RF transmission characteristics of the farmland underground sensor network are studied.The RF transmission model of the farmland underground sensor of the low-power Wide-Area Network(WAN)is improved.The main work is as follows:1.According to the distribution characteristics of wireless sensor networks in farmland environment,wireless ground and underground sensor distribution networks are established,and the transmission channels of Aboveground-Aboveground,Underground-Aboveground,Aboveground-Underground,Underground-Underground are given.The model and the corresponding energy transfer expressions give the attenuation characteristics of the channel transmission.2.A test scheme for radio frequency transmission performance of wireless farmland underground sensors based on low-power wide area network is built.APC300 and APC340 are selected as sensor nodes,and spectrum analyzer is selected as test equipment.Four kinds of communication are used in different buried positions and different antenna forms.The received power of the sensor node in the mode is collected and processed accordingly.3.For the signal power,node depth,node antenna height and horizontal distance parameter between farmland soils,curve fitting and multiple linear regression analysis are carried out for the four theoretical models and measured data.The Aboveground-Aboveground communication model conforms to the logarithmic path attenuation loss model and the received signal power on both sides of the transmitting end is basically symmetric.The theoretical models of the Underground-Aboveground,Aboveground-Underground,Underground-Underground modes are not applicable to the underground RF of the farmland.The three communication models are improved,and an improvedmodel of radio frequency transmission characteristics of wireless farmland is obtained.The improved correlation coefficients are 0.96,0.88,and 0.99,respectively.4.Test the transmission power of different sensor networks(common module and Lora module)and fit the data.The received signal power of the Lora module in Underground-Aboveground communication is about 30% higher than that of the ordinary module.The improved model is compared with the data measured by the common module,and the correlation coefficient between the two is 0.95.Comparing the transmission characteristics of the common module and the Lora module,the Lora module sensor network is more accurate in characterizing the wireless transmission characteristics in the farmland environment.