Analysis Of Signal Integrity In The High-speed Circuit

With the development of modern electronic technology, the range of application is expanding increasingly for high speed circuit, and systematic clock frequency is increasing rapidly.With more quick risetime and the increase of integrated degree of circuit, the line's mutual link of printed circuit board and board layer's property have greater influence on the systematic electrical performance, and caused a lot of signal integrity problems.For the design of low frequency circuit, the mutual link relations can be regard as lumped parameters, and the influence of line's mutual link and board layer's property can be neglected.But the interconnects of the high speed circuit becomes a transmission line with distributed parameters, and the permittivity of the printed circuit board also influences the performance of circuit system. Therefore, a lot of signal integrity problems have appeared, such as reflection, crosstalk and simultaneous switching noise, etc., which cause serious consequences such as signal distortion, out-of-order timing, incorrect data and incorrect trigger of the system.The gradual improvements of the theories in signal integrity provided a theoretical basis for solving these problems, and the development of simulation software provided keen edge to circuit designers.With basic theory as guide and simulation software as tool, we can discover the hidden signal integrity problems earlier before the product made, and the probability of the failure caused by signal integrity problems is reduced at the lowest level. Then it is possible that products can be developed very successfully only one time, and the development period is shortened and the cost is reduced.This paper made a theoretical study and actual simulation as to the signal integrity problems in the design of high speed circuit. The basic contents are as follows:The fundamental theories of signal integrity were studied, including high speed circuit theory, electromagnetic field theory and transmission line theory. The mechanism in forming reflections were analyzed by modeling, and various termination measures for improving reflections were given. Capacitance matrix and inductance matrix were studied, which were used to describe crosstalk; The crosstalk principle was explained by coupling. Simulation software Hyperlynx and simulation models for this paper were introduced. On the basis of mastering Hyperlynx, some contents were simulated and analyzed, that is, various reflection phenomena, the influence on reflection by various parameters, solving capacitance matrix and inductance matrix, simulating coupled electromagnetic field, analyzing various crosstalks, etc. Theoretical analysis and actual simulation indicated that the effects of termination technology are very obvious on improving signal reflection of high-speed circuit; The proposed routing tactics for reducing crosstalks are feasible; crosstalk of coupled lines can be worked out from matrix. Accordingly, more integrated analysis tactics of reflection and crosstalk in high speed circuit were offered.