Development of a GUI for EMI Filter Insertion Loss and Transfer Function Modeling

Electromagnetic compatibility (EMC) is one of the biggest problems in modern electrical devices, while the size of the electronic component is getting smaller and the clock speed is increasing. The clock frequencies have exceeded gigahertz in many applications. These conditions cause electronic devices to interact more with each other, and the signals required for their operation are perceived as noise by other circuits. The common and the most effective method to suppress electromagnetic noise is to use electromagnetic interference (EMI) filter, especially for conducted emission noise. The characteristics of filters are defined by their attenuation, also known as insertion loss (IL), which is function of frequency and expressed in decibels (dB). Most filter manufacturers provide graphs showing the frequency response of the insertion loss for matched source and load condition, 50 Ω. But, in reality, the source and load impedances are mismatched. In this study, for different kinds of EMI filters like RL Low-Pass, RC High-Pass, LC Band-Pass, and LC Band-Stop, analytic expressions of IL have been obtained in mismatched source/load impedances, and a graphic user interface has been designed to enable the analysis of the different impedance values observed in real-world applications. Other important parameters for EMI filters are the transfer function and bode diagram which supply phase and magnitude characteristics depending on the frequency. The transfer function and bode diagram for related EMI filters have been included on the GUI, as well. The designed GUI enable the user to change dynamically component values of the EMI filter in mismatched source/load impedances and to see the characteristics of the filter in these specific conditions.