Design And Implemention Of USB3.0 Test Fixture Based On Plane EBG Structure

USB3.0 test fixture,as a tool for testing USB3.0 chip,In the process of designing USB3.0 test fixture and the actual circuit,there will be different line length,etching change and other differential line asymmetry problems,resulting in common mode noise,which will affect the results.Therefore,it is very important to design a planar EBG structure that has deep common mode noise suppression depth and wide suppression bandwidth for the differential line,Single C-type planar EBG structure is widely used because of its simple structure,small size and good effect in suppressing common-mode noise of differential line.In this thesis,the effect on the performance of suppression of common mode noise by the key parameters of the single C-type planar EBG structure was deeply analyzed.the optimized design of single C-plane EBG structure was made.The analysis shows that there is a negative correlation between the groove length of the single C-type planar EBG structure and the center frequency of the common mode suppression stop band.,two single C-type planar EBG structures with different groove lengths were designed by adjusting the groove length in this thesis.A structure with a long groove length produces a low frequency common mode resonance,and a structure with a short groove length produces a high frequency common mode resonance.Then the cascading technology was used to cascade the two single C-type planar EBG structures into a double C-type planar EBG structure,so that the common mode rejection frequency range is within a specified frequency range and the common mode rejection bandwidth is broadened.On this basis,this thesis applies the double C-type planar EBG structure to the USB3.0 test fixture.In the design process,the HFSS electromagnetic simulation software was used to optimize and improve the planar EBG structure,and the frequency domain performance of the USB3.0 test fixture is simulated and analyzed.Finally,the USB3.0 test fixture based on the planar EBG structure was fabricated into a physical object and tested using a vector network analyzer.The area of plane EBG structure designed in this thesis is 19.5mm × 6mm and the measured results show that the USB3.0 test fixture loaded with plane EBG structure has a good common mode noise suppression performance,The common mode suppression depth is below-10 dB in the frequency range of 2.64GHZ-7.43 GHZ,the common mode suppression bandwidth is 4.79 GHz,and the differential signal can be well transmitted.