Application Of Genetic Optimization Algorithms To Lumped Circuit Modelling Of Coupled Planar Coils

In portable electronic devices, like smart phones, coupled planar coils are often used as common mode filters (CMF). The purpose of these CMF is to suppress electromagnetic interference (EMI) between wireless communications systems (e.g. WIFI) and digital high-speed interfaces (e.g. USB 3). A designer of such an electronic device usually carries out a signal integrity (SI) analysis, using models of the system components. There are two alternative ways of modelling the CMF: One is based on matrices (called S-parameters) that describe the behaviour in the frequency domain and are either derived from measurements or simulation tools. The other is using a representation based on lumped circuit networks. In this work, a lumped network is generated manually based on expert knowledge. The advantage of this approach is the reduced number of only passive network components compared to traditional methods that produce much larger networks comprising of many active and passive devices. On the other hand, suitable component values of the lumped network need to be found so that the network exhibits the same frequency response as the physical device. Since there are many interacting parameters to be tuned, this cannot be achieved manually. Hence, a genetic algorithm is applied to this optimisation problem. Two sets of experiments were carried out and a sensitivity analysis has been conducted. It has been shown that the proposed method is capable of finding near optimal solutions within reasonable computation time.