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Modern high-frequency electronic systems demand precise characterization and modeling techniques to ensure signal integrity and electromagnetic compatibility. This thesis presents three core studies focused on real-world challenges in high-speed and power electronics: EMI mitigation using 3D printed absorbers, wideband liquid dielectric charac- terization, and accurate transformer modeling. The first study demonstrates a targeted approach to mitigating electromagnetic in- terference (EMI) in a commercial router. By using holography imaging to identify radiation hotspots, custom absorber structures were designed with commercially available materials, fabricated via 3D printing, and applied directly to emission sources. Radiated emission tests in a reverberation chamber showed up to 9 dB reduction in EMI, validating the method’s effectiveness for practical applications. The second study proposes a wideband method (up to 30 GHz) to characterize liquid dielectrics using a differential microstrip line and the Djordjevic-Sarkar model. Dielectric constant (DK) and dissipation factor (Df) were extracted by comparing S-parameters of air and liquid-immersed conditions between measurement and simulation results. Experi- mental validation with PAO4 and DC-15 liquids showed strong agreement with traditional cavity resonance methods, with DK deviations under 1.5%. The third study addresses transformer modeling across 100 kHz to 30 MHz by developing an equivalent circuit model that accurately captures winding effects, parasitic capacitance, and leakage inductance. The approach incorporates an optimized coupling coefficient based on physical parameters. Validation with air-core inductors demonstrated high model accuracy, with an average relative error of 2.2%. 

This paper introduces a non-destructive and simple setup method for characterizing dielectric liquids over a broad frequency range (up to 30 GHz) using the Djordjevic-Sarkar model. By employing a differential microstrip line and comparing scattering parameters in air-filled and liquid-immersed scenarios, the proposed method achieves precise dielectric constant (DK) and dissipation factor (Df) extraction. 2 Liquid samples (PAO4 and DC-15) were tested using this method. Validation against the cavity resonance method demonstrates a strong agreement for the extracted DK values, with a relative error of less than 1.5 %, indicating high accuracy. However, the method is less sensitive to Df, particularly for low-loss dielectrics, with a relative error of 67 % at the cavity resonance frequency. Despite this limitation, the technique provides a practical approach for wideband dielectric characterization, particularly for applications in immersion cooling and high-frequency electronic systems. 

In automotive systems, a metal chassis protects the components against the external environment. However, the metal chassis is conductive, which results in unwanted conducted emission (CE) coupling to electric components. An inductor used for power factor correction (PFC) is one of the affected components. When the inductor is mated with the metal chassis, the impedance of the inductor changes. It is also hard to predict the CE coupling due to the structure-dependent characteristics. That is, the CE coupling is not negligible and hard to clarify. Therefore, this article proposes an efficient modeling method for the inductor, which is mated with the metal chassis. The proposed method includes the measurements and optimization algorithm. The measurement setups include an impedance analyzer (IA) and a vector network analyzer (VNA). The IA is used to measure the accurate inductance value of the inductor, and the VNA is used to measure the coupling to a chassis. The optimization algorithm includes simulated annealing (SA). The equivalent models for the inductor, the inductor with 2-D metal chassis, and the inductor with 3-D metal chassis are introduced, respectively. The introduced equivalent models are well-matched to the measurements up to 100 MHz. 

This study delves into the modeling of a transformer in the frequency range of 100 KHz to 30 MHZ. The coupling coefficient was considered as a function of leakage and self-inductance and incorporated in the optimization process of transformer modeling in the proposed method. The equivalent circuit focused on the critical aspects of leakage inductance, parasitic capacitance, and winding effects. At first, the winding effect of an air-core inductor over wide frequency range with both single-layer and double-layer windings was shown. Then an equivalent circuit was proposed to model a transformer over this frequency range. The comparison between the measured and proposed model demonstrates strong accuracy over the frequency range, with an average relative error of 2.2% on the primary side and 6% on the secondary side.