Optimization Design Of GTEM Cell

With the development of modern technologies such as communication and automation,the radio frequency performance of various electronic devices have been paid more and more attention,and electromagnetic compatibility has therefore become an increasingly active discipline.The concept of gigahertz transverse electromagnetic cell(GTEM cell)was proposed in the development of electromagnetic compatibility testing,it has higher maximum operation frequency and larger test space than traditional transverse electromagnetic wave cell(TEM cell).GTEM cell can be used as an substitution test site for open area test site(OATS),anechoic chamber and semi-anechoic chamber.GTEM cell has been widely used for its lower cost and smaller volume.With the increase of the service time,some design errors or mechanical deformation can cause degradation of the GTEM cell's performance,which affects the impedance matching and limits the upper limit of the operating frequency and changes the space of the effective test area.In order to improve the performance of the GTEM cell,this paper establishes an electromagnetic simulation model and analyzes the influence of mechanical structure design on its performance.Firstly,the characteristic impedance of the GTEM cell is analyzed and characteristic impedance is calculated by using quasi-static three-dimensional algorithm.The accuracy of the calculated result is verified through simulation.Test methods of the main performance parameters and the overall structure design of GTEM cell are introduced.Secondly,an ideal electromagnetic model of the GTEM cell is established,and the finite difference time domain(FDTD)method is used to simulate S parameters of the port,field distribution and field uniformity of the GTEM cell.The feasibility of the research scheme is verified by simulation results.Then,we focused on the mechanical structure that affect the performance of the GTEM cell,including integration of the strengthening board,structural deformation and size change of the core board,these factors are analyzed individually through simulation method.The frequency band of the simulation is below 3GHz due to hardware limit.The simulation result indicates that the voltage standing wave ratio(VSWR)of the GTEM cell increased by 0.17 around the extreme frequency after integrated the strengthening board,and the uniformity of field distribution also declined;the curvature of the core board shows a more severe degradation of field uniformity with frequency increasing;and the peak value of VSWR rises by 0.03 after the core board is widened.Finally,the integrated model is established which includes various factors.For voltage standing wave ratio,the simulation result matches the test data very well,and the maximum difference between 0-3GHz is about 0.5.Time-domain S-parameters simulation result is calculated,the distance of the strengthening board corresponding to the maximum reflection point has a relative error of about 8% compared to experiment result.Main factors affecting the performance of the GTEM cell is judged by experiment result,and the correctness of the research scheme is also verified.The improvement directions are given according to the characteristics of each part of the structure,and a simple and feasible optimization method is proposed.