针对电路板互连结构的信号完整性问题,为了提高仿真效率,采用了时域宏模型与电路仿真相结合的混合方法.该方法在全波电磁场(FDTD)仿真的基础上计算了互连结构的端口散射参数(S参数),在将全波仿真结果嵌入电路仿真环境时,以矢量匹配法(VFM)结合有理函数逼近构造网络函数的宏模型,进而导出模型的等效电路.由于VFM很好地解决了随着逼近阶数的增加而出现的矩阵病态问题,同时利用同一组极点及迭代过程完成所有端口间参数的有理函数逼近,因而方便了复杂结构的分割处理与分别建模.实例分析表明,分割处理的建模时间约为整体建模的50%,同时,实例的仿真和S参数的测试对比检验了该混合方法的正确性.
To analyze the signal integrity of interconnects on printed circuit board more efficiently, a hybrid method combining time-domain macromodeling with circuit simulation is developed. The finite-difference time-domain method (FDTD) is chosen to calculate the S-parameters on the terminals of interconnects. Embedding the above simulation results into circuit simulator, the vector fitting method (VFM) is adopted combining rational function approximation to construct the interconnect macromodel. Because VFM enables to perform the approximation with the same series of starting poles and iteration cycles steadily, it is efficient to construct the sub-models romodel respectively when dealing with complex structure, which is validated by the S-parameters measurement in the case of multi-submodel connection, and CPU time is about 50% of the consumed in the full structure simulation.