Development of a practical electro-magnetic interference (EMI) simulation in high speed optical transceivers

The growing bandwidth of optical communication systems has made great improvements to information technology infrastructures. However, electro-magnetic compatibility becomes an issue due to the high frequency of the components. EMI problems occur due to the miniaturization and high density of the (PCB) mounted on the system. Generally, electro-magnetic radiation is generated by the circuit elements. For example, switching in the LSI raises the voltage swing between the power source and ground which is known as ldquoground bouncerdquo. EMI problems related to the ground and power source are linked to the power integrity, and is influenced by the structure of the patch antenna parasitically existing between the power source and ground. That is to say, most of the time this problem can be solved by utilizing the appropriate power source and ground pattern layout at the PCB design stage. However, high speed digital signals measuring at more than 10 Gigabit per second (Gbit/s) typically have high frequency components in excess of 40 GHz. There is little feasible knowledge available that illustrates guidelines for the perfect layout method to prevent the emission on the PCB for such a high frequency application. Therefore, we focused on the finite element method used in the 3D electromagnetic field analysis simulator so that we could solve the emission within the frequency domain. We first correlated both qualitatively and quantitatively the actual measurements and the simulation results. Then we investigated the countermeasure for the emission intensity (EMI level) from the 10 Gbit/s optical transceiver by simulation and then verified it.