The Design Of Filter Used In Electric Field Probe

With the wide application of modern communication equipment,the construction of 2G,3G,4G and the upcoming 5G communication and various civil radar transmitting stations is becoming more and more intensive.While the means of communication bring convenience,the EMR in space is increasing,which aggravates the impact on human body and modern precision instruments and equipment.In order to provide a healthy living environment and ensure the normal operation of the equipment,precise EMR detection equipment is needed to monitor the surrounding environment.As a common equipment for electromagnetic radiation detection,electromagnetic radiation probe is developing towards miniaturization,specialization,high precision and high performance.In order to analyze the source of radiation,it is necessary to design the electric field probe in professional application scenario.As one of the important components of the professional probe,the filter determines the measurement frequency band,accuracy,bandwidth and out-of-band suppression performance of the electromagnetic radiation probe.Therefore,this paper mainly focuses on the filter module of professional electromagnetic radiation probe.The main work of this paper is as follows:The basic requirements of filters in professional electromagnetic radiation probes and the design methods of modern microwave filters are studied.Based on the principle of filter design,a dual-band filter in 2G band of mobile communication is designed by using modern microwave filter methods such as microstrip resonant ring and open-circuit branch loading.The high-order harmonics of the resonant ring are removed by drilling holes in the open-circuit resonant ring.On the basis of these theories,a single-band filter in 3G band and a dual-band filter in 4G band are designed.Based on the frequency conversion method of dual-band filter and SIR branch loading theory,the simulation model of 5G band filter for mobile communication is established.The parameters of filter S₁₁ and S₂₁ are optimized by simulation.A new type of three-band band-pass filter for 5G mobile communication is designed.The simulation models of 2G（GSM1800）,3G and 4G band-pass and band-stop filters are established by using defective ground structure（DGS） and folded resonant ring structure.The transmission coefficient and reflection coefficient of the filter are optimized by simulation.Broadband band-pass and band-stop filters with combined frequency bands are designed.The size of the filter is reduced effectively,the pass band of the filter is increased,and the performance of the filter is improved.Finally,the simulation filter is made and the S parameters of the designed filter are measured by vector network analyzer.The measurement results show that these filters can meet the requirements of mobile communication frequency band measured by electromagnetic radiation probe and S band miniaturization,multi-band,low insertion loss and high out-band suppression.