Some recent results from research conducted in the EMC group at Okayama Universiry are reviewed A scheme for power-bus modeling with an analytical method is introduced. A linear macro-model for ICdLSIs. called the LECCS model, has been developed for EM and EMS simulation. This model has a very simple structure and is suficiently accurate. Combining the LECCS model with analytical simulation techniques for power-bus resonance simulation provides a method for high-speed E M simulation and decoupling evaluation related to PCB and LSI design. A usefir explanation of the common-mode excitation mechanism, which utilizes the imbalancefactor of a transmission line, is also presented. Some of the results were investigated by implementingprototypes of a high-speed EM7 simulator, HISES.