Research On Signal Integrity Of High-speed Serial Link

There are many aspects which affect the performance of high-speed link, such as interconnect density, interconnect band width, signal integrity and power consumption. High bit rate, high density, low power consumption, low voltage and high current are the trends of today’s high-speed serial link. Higher bit rate, bigger challenge the design of signal integrity will face. How to design a reliably high-speed serial link is a hot topic for the whole industry and the colleagues.This dessertation gives a brief summary of signal integrity analysis. Based on the basic theory of the Maxwell equation, the introduction of the transmission line theory and scattering parameters are presented, then the three main links of system transmitter, channel, receiver system are analyzed, finally the timing jitter and the margin distribution are briefly introduced.A high-speed products system is designed which can support 6Gbps SAS2.0 serial link, and the simulation analysis and experimental testing has been separately completed to verify the signal integrity of this link system. Firstly, the methods of PCB trace modeling, impedance analysis, and crosstalk simulation is studied. Secondly, the 3D electromagnetic field modeling of a Via hole for linecard board is setuped, and the methods for insertion loss and return loss optimization is summarized. Then, based on a 20 inch PCB channel, some simulations of full serial link are done, and the effects of transmitter / receiver, signal coding, passive channel and some other factors are studied with signal integrity pespective. Finally, a complete link system for a real product is builted, and the requirements of SAS 2.0 standard for passive interconnect channel simulation is achieved through the press-fit holes impedance optimizing. In order to validate the accuracy of simulation and the robustness of the high speed link of the real product, the test fixture is designed and the corresponding producet boards are manufactured. The system operation pressure has been tested at room temperature, high temperature and varying temperature etc. conditions, the actual product service test environment measurement results are compared with the full link passive characteristics, then the results of simulation, further analysis of passive simulation method are tested to verify the accuracy, objectivity and reliability; By checking the bit error rate, whether the product system meets 6Gbps SAS2.0 high-speed serial link requirement can be determined.Because the simulation results for PCB traces and vias are in good agreement with the fixtue measuremet results, the modeling and simulation method has good accuracy and engineering value which can be widely used in the design of similar applications. SAS bus technology is widely used in enterprise-class high-performance disk products, but because of the huge challenges of high-speed serial link signal integrity design, local companies who can provide 6Gbps SAS 2.0 products are rare. This dissertation carries out a research on SAS2.0 high-speed serial link simulation method, and proposed a new idea for simulation of high-speed serial link basing on commercial ADS software.