Research On Key Subassemblies Modeling Of High-speed Circuits

Nowadays,with the rapid update cycle of high-speed electronic products and the increasingly strict quality control requirements,designers are usually required to consider circuit performances at the very beginning of the circuit design and to guarantee the success without any reworks.Moreover,due to the continuous increase of the speed in high-speed interconnects,the design of high-speed circuits becomes extremely complicated.If the signal integrity(SI)and electromagnetic compatibility(EMC)related characteristics are not rigorously considered at the beginning of the circuit design,the rectification process will be extremely complicated.Therefore,rapid and accurate modeling,simulation and analyzing its related characteristics have become the preferred way for the high-speed interconnect circuit design.It is difficult to model and simulate a whole high-speed circuit board due to the vast compute resources consuming.Therefore,it is often necessary to model some key structures or characteristics of high-speed circuit board.In view of these contents,this paper studies the modeling of three key structures,namely,the via structure,the slotting structure and the transmission line structure in the high-speed circuit.The main research contents are as follows:(1)An improved partial element equivalent circuit(PEEC)based via model was studied.By redefining the reference ground of the equivalent circuit,the traditional partial element equivalent circuit model is improved in the via modeling.This equivalent circuit model can be used to model various types of vias,especially the differential vias with irregularly shaped anti-pads.The thesis continues to study the connection method of the via model and the plate pair circuit.The model can accurately simulate vias and the circuit board including some vias to 50GHz.(2)An equivalent circuit model of a strip line crossing a slotted ground structure was studied.By using the equivalent principle,the structure of stripline with slotted ground can be consider as the problem of a cavity excited by the surface electric current at the stripline and the surface magnetic current at the slot area.Combined with the mixed potential integral equation(MPIE)and cavity green's function,an equivalent circuit model is proposed in this thesis,which can efficiently and accurately model and the SI and EMC characteristics of the stripline with slotted ground structure.(3)Based on the causality analyzing of a transmission line,a causal RLGC model of the transmission line was studied.In this thesis,the causality of a RLGC model was analyzed for the first time in the industry.Furthermore,an improved practical equivalent model of transmission line with rough conductors was presented.The transformation relations between the ideal transmission line RLGC model and the rough transmission line RLGC model were also presented.(4)The concept of dielectric surface roughness was first proposed and its influence on high-speed transmission lines was studied.Through theoretical analysis,the definition of the dielectric surface roughness constant is given,and then the frequency independence of the constant is verified by 2D full-wave simulation.Through simple equivalence,the thesis gives the approximate calculation method of dielectric surface roughness constant,and further improves the RLGC model of rough transmission lines.(5)Based on the physical model of transmission line loss and the binary search algorithm,a fast and accurate fitting method for the transmission line loss was studied.The proposed binary fitting method can efficiently and accurately eliminate the large error data segment,so as to give the optimal fitting results.Through this method,more accurate measurement results of losses can be obtained,the quality of measurement results can be evaluated,and the confidence interval of measurement results can also be given,further,more accurate parameters or references for the design and modeling of high-speed circuits can be provided.All of these studies are verified by experiments or simulations.