Study On Propagation Characteristics Of Radio Wave In Communication Well And Design Of Special Antenna

With the advent of the “Internet plus” era,the concept of “smart city” came into being.The intelligence of urban municipal facilities monitoring alarm system is to use the wireless sensor node under various municipal well covers to sense the status information of the manhole cover and the interest parameters of the downhole,and upload it to the monitoring platform through the mobile communication network.However,due to the special underground environment and the shielding effect of the metal manhole cover,the quality of information transmission is terrible.This involves not only the grasp of the radio wave propagation characteristics in the underground scene,but also the design of the relevant antennas.Therefore,it is great significance to study the propagation characteristics of radio waves in downhole communication scenarios and the design methods of the related special antennas.In addition,the characteristic mode theory has very important guiding significance for the design of multi-band and wideband antenna.Therefore,this paper will use the characteristics mode theory as a design guide and based on the study of radio wave propagation characteristics in the underground communication environment to design three special antennas for downhole communication in different operating bands.The detailed contents are explicated as follows:Firstly,the cavity mode analysis method and the characteristic mode analysis method of the microstrip antenna are introduced.The characteristic parameters are calculated,and compared with the calculated values of cavity model theory,which lays the foundation for the design and analysis of the subsequent special antennas.Then,according to the scene in free space,electromagnetic simulation software is used to verify the correctness of the simulation method of the electromagnetic wave propagation characteristics.The distribution of field strength at different locations in the manhole with different frequencies of the transmitting antenna is analyzed,and the basic requirements for the design of underground monitoring antennas are summarized,which can provide a reference for the following antenna design.Then,a novel near-field UHF-RFID antenna is design for an engineering application.According to the process of antennas design and the characteristics of the downhole environment,a dedicated downhole monitoring antenna for the CDMA800 band is designed.It is proved that the antenna has broadband characteristics through the characteristic mode analysis.Finally,under the guidance of the characteristic mode theory,two downhole monitoring antennas working in CDMA800/GSM9000 dual bands and 2G/3G/4G multiple bands are designed.This paper gives detailed design ideas,analysis process and simulation and test results of the proposed antenna.The analysis results show that the proposed antenna has good potential for downhole engineering application.