Design And Application Of Space Electromagnetic Sensing System Equipment

The rapid development of wireless communication has promoted the increasing use of frequency bands below 6 GHz.Except the currently commonly used 3G and 4G communication network systems,domestic 5G communication network systems have been commercially trialed in two frequency bands below 6GHz,3300 ? 3600 MHz and 4800 ? 5000 MHz.The domestic drone working frequency band,the WIFI working frequency band is 2.4GHz and 5.8GHz,and the use of many frequency bands such as various radio station working frequency bands,resulting in a more intense spectrum below 6GHz.As the frequency band of spectrum usage is becoming wider and wider,in order to effectively promote the development of the radio spectrum,it is necessary to use and allocate spectrum resources reasonably.However,in practice,the influx of a large number of illegal radio equipment occupies a part of the frequency band of the legal spectrum,which not only causes mutual interference between signals,but also reduces the utilization rate of the spectrum,resulting in crowded spectrum usage and increasing demand for spectrum monitoring.The monitoring of the radio frequency spectrum is a prerequisite for maintaining the order of air radio waves,increasing the utilization of spectrum resources,improving the positioning accuracy of illegal radio equipment,and strengthening the effective management of radio equipment.Based on this,in view of the demand for spectrum monitoring,this paper combines the Xi'an science and technology project "Electromagnetic Space Spectrum Sensing Device Design and Development",a space electromagnetic spectrum sensing device is studied and designed,whose spectrum sensing range is 20 MHz ? 6GHz,covering common civilian frequency band,it can effectively monitor the radio frequency signals existing in the environment,and can also locate and find illegal radio equipment or signals of interest.The main work of this article is as follows:(1)First,the background of cognitive radio and the current research situation at home and abroad are summarized.Combined with the actual project,it is necessary to conduct in-depth research on the technology involved in the subject and put forward the overall design plan of the system.(2)Space electromagnetic spectrum sensing equipment hardware is designed and manufactured,including radio frequency receiving unit,GPS real-time timing unit,network relay unit and network transmission unit,the main circuit of each unit and the production of hardware are described in detail.Among them,the radio frequency receiving unit solves the technical difficulties such as the interference caused by the image frequency components of the broadband radio frequency receiver and the number of required filters.The two-level superheterodyne receiving structure with two-level mixing and the reasonable division of the 20 MHz ? 6GHz frequency band is mainly studied.The GPS timing unit designed with the LTE-6T module scheme not only improves the positioning accuracy of the space electromagnetic spectrum sensing device itself,but also provides high-precision moments for the collected spectrum.(3)The software of space electromagnetic spectrum sensing equipment is designed.For the software design of the GPS real-time timing unit,the software design of the network relay unit and the communication design of the radio frequency receiving unit and the industrial computer,implement the Fourier transform algorithm and time difference(TDOA)positioning algorithm.(4)Perform functional tests on each unit and the overall system,successfully applied to the 2019 college entrance examination security,and conducted TDOA positioning tests in Lintong District,Xi'an City,Shaanxi Province and Chengdu City,Sichuan Province.First,the indicators of each unit of the system equipment are tested and analyzed.The highest accuracy of the GPS real-time timing unit output can reach 0.1Hz@10MHz.The software and hardware of the system were tested for joint adjustment,and the maximum attenuation was 2d Bm in 20 ? 1000 MHz,and the linear attenuation was basically maintained in the frequency range of 1000 ? 6000 MHz,that is,1d Bm / @ 1GHz,which met the project accuracy requirements.The equipment was tested for TDOA positioning in Lintong District of Xi'an City in Shaanxi Province and Chengdu City in Sichuan Province.The near-field test and far-field test were conducted respectively.The test results show that the maximum circle error of the 3 km near-field positioning test does not exceed 27 meters;The maximum circle error of the far-field positioning test in kilometers is not more than 200 meters.