Research On Modeling And Transmission Characteristics Of Interlayer Transmission Lines In Multilayer Circuit Boards

With the rapid development of electronic technology and the increasing maturity of highly integrated chip technology,the trend of miniaturization of the circuit began taking shape,followed by the prominent issue of electromagnetic compatibility.In order to meet the requirements of the PCB substrate design and achieve miniaturization,the electro magnetic compatibility(EMC)and signal integrity(SI)have become an inevitable issue.Aiming at achieving miniaturization,the design of multi-layer boards(multi-layer PCBs)in which two-panel structures are vertically stacked in a PCB design has gradually become a mainstream approach.For example,four to eight layers of PCBs are often used on the motherboard of a computer;as opposed to some complicated communication devices,which may even need more than 40 layers.The presence of multi-layer PCB also brings about many problems.Different from the ordinary stripline whose upper and lower substrates are both GND between PCB boards,in the microstrip circuit,one layer of the multi-layer PCB board is often employed as the GND layer while the other is the power layer.The problem is that the potential difference between the upper and lower sides will create an electric field between the two parallel plates,thus making the entire system become a resonant cavity.In this context,the microstrip line in the middle will be problematic accordingly.This thesis intends to study the double parallel plates above.By using the current of the input signal as an incentive,the electric field generated between the parallel plates can be calculated.Afterwards,the electromagnetic field generated by the resonance of the parallel plate is considered to be the external electromagnetic field to the strip line.Through transforming and solving the telegraph equation,the transfer matrix of the whole system can be calculated,the transfer matrix will be transformed to get the scattering matrix,so that the transfer characteristic of the transmission line can be known.Then the theoretical calculation results will be compared with simulation results and physical test results to verify its effectiveness.This thesis innovatively proposes the telegraph equation under the influence of the external electromagnetic field.Based on the expression of the electric field between parallel plates,the equation of the transmission matrix of the inter-layer transmission line is deduced and the height of the transmission line is added,so that different heights of the transmission line can be calculated to deal with the calculation of multi-layer circuit boards.In addition,the algorithm above will also be applied to occasions where the single transmission line and multiple transmission lines between the power layer and the GND layer,differential transmission lines and single / multiple transmission lines coexist,which is close to the practical application,hence verifying the accuracy of the algorithm.At the same time,this thesis will also put forward a series of suggestions on how to design the PCB circuit to reduce the interference between the transmission lines.Therefore,the conclusion of this thesis may exert significant influence on the application of PCB in practical engineering.