Development Of CFGS For Electric Field Probe Calibration

The E-field probe can be used to measure the electric field after calibration,the recommended equipment to produce standard electromagnetic field in IEEE Std 1309-2013 has TEM cell,GTEM cell,horn antenna,etc.But none of them can meet the probe calibration of wide-band and strong electric field.In order to achieve the calibration of wide-band and strong electric field,this paper developed a new calibration device for electric field probe calibration——Co-conial Field Generation System,called CFGS.This paper introduced the basic structure of CFGS and its working principle at first,deduce the formula for calculating the impedance and internal field strength of CFGS.Combined with the characteristic impedance,field strength and VSWR parameters,the primary design of CFGS is carried out.The performance of CFGS is mainly related to the design of connector and terminal structure,so the design of connector and terminal is the focus of this paper.The connector has high precision and can directly affect the high frequency performance of CFGS,therefore,it is necessary to design the material,size and capacitance compensation for dielectric support,ensure the continuity of characteristic impedance.The connector structure of CFGS is optimized by CST-MWS.Terminal use terminal short circuit and terminal connect matched load two scheme.Terminal short circuit reduce the reflection of electromagnetic wave by absorbing material,Terminal connect matched load is used to reduce the reflection of electromagnetic wave in two ways:impedance match and electromagnetic wave absorption.After the completed the processing,rectify and reform the connector and terminal structure.By testing the TDR curves,identify the location of the abnormal impedance of the connector after rectification.The VSWR of CFGS in different terminal structure is tested.And then simulate the electric field inside CFGS,The electric field distribution in CFGS is obtained.A position in the uniform region of CFGS field is selected as the calibration point of the probe,and the field intensity of the point is measured in different frequency bands,calibration can be accomplished by using transfer standards traceable to national standards laboratories.Through the connector and terminal debugging of CFGS,the VSWR of CFGS in the frequency range of 200MHz-18GHz is less than 2,the characteristic impedance of CFGS remained stable,The value of electric field of CFGS is given,and the calibration of the field probe is realized.