Undesired conversion between common-mode (CM) and differential-mode (DM) noise often occurs in modern electronic and electrical systems, posing challenges in terms of Electromagnetic Compatibility (EMC). Modal analysis represents a crucial tool in EMC investigation and provides insight into the mechanism underlying mode conversion. By inspecting CM and DM behaviors and their interconversion, it allows for understanding of conducted emission propagation mechanisms, drives electromagnetic interference (EMI) filter design towards optimal/tailored solutions, and enables the possibility to identify the main contributors to the radiated emission phenomenon. This paper offers a comprehensive review of mathematical methodologies and modelling strategies for EMC-oriented modal analysis, with particular emphasis on mode conversion phenomena. To this end, modal decomposition techniques and standard parameters for quantifying mode conversion are summarized and compared. Additionally, the paper provides an overview and in-depth discussion of different scenarios and test cases in which mode conversion occurs, with the final goal to achieve a systematic comprehension of its root causes and consequences within power and communication systems. Eventually, a survey of circuit modelling approaches for mode conversion is presented, offering insights into addressing this phenomenon effectively.

Flexible flat cables (FFCs) are a typical form of interconnect in modern electrical and electronic systems that facilitate signal transmission between components while minimizing harness volume. FFCs offer a practical connectivity solution in energy management applications, where sensors and displays are essential for monitoring power consumption and performing advanced digital control. In FFCs, signal lines run parallel to each other, and the proximity between lines can cause interference among adjacent signals. Therefore, the arrangement of signals along different lines can significantly influence the overall transmission performance. In this paper, the order of signals within the FFC is optimized to ensure optimal transmission performance, avoiding electromagnetic compatibility (EMC) and signal integrity (SI) issues. The problem is tackled by implementing a multi-objective optimization (MOO) approach, whose aim is to minimize near-end and far-end crosstalk, namely NEXT and FEXT. The effectiveness of the proposed approach is verified by considering a minimized interconnection system involving an FFC. The Pareto-optimal solutions are identified, and worst-case and best-case conditions are highlighted. The results show improvements in EMC and SI, underlining the relevance of the proposed optimization strategy. The proposed strategy provides a valuable tool for designing high-performance interconnections in electrical and electronic systems.

Bob Smith (BS) termination is usually adopted to terminate twisted wired pairs in order to reduce common mode (CM) interference, as suggested by Ethernet board design guidelines compliant with the 100BASE-TX standard. However, there is not a robust proof of the effectiveness of the specific component values for this termination. This article proposes a detailed analysis and design technique for the termination components that allow for effectively suppressing CM disturbance at the Ethernet board transmission driver ports. The focus is on the analysis of the CM reflection and differential-to- CM conversion. To this end, an equivalent circuit of the system is derived and characterized at the transmission ports by a suitably-reduced mixed-mode S -parameters matrix. Parametric analysis and multiobjective optimization are used to optimize resistance value efficiently. The final results indicate the necessity of identifying a ground path for CM currents, and confirm the effectiveness of BS termination. Regarding the value of the involved resistors, it is proven that it should be defined based on the specific system configuration and application requirements, i.e., there is not a single optimal value applicable to all configurations. Accordingly, instead of a specific value, a range of optimal resistance values is proposed.

This work presents a frequency-domain and modal-domain model to analyze how the length of a three-phase power cable influences conducted emission (CE) voltages measured through a line impedance stabilization network (LISN). The measurement setup considered consists of an equipment under test (EUT) connected to the LISN via a power cable whose cross-section is defined in this study as quadrilateral, namely, four conductors arranged at the corners of a quadrilateral: typically the three phases and the protective earth or neutral conductor. The cable is modeled as a multiconductor transmission line (MTL). To evaluate the system performance both with and without the cable, the concept of voltage insertion ratio (IR) is introduced, defined as the reciprocal of the typical insertion loss. Closed-form expressions are derived for both common mode (CM) and differential mode (DM) emissions. The objective is twofold: to understand under which conditions the LISN measurements overestimate or underestimate the actual emissions at the EUT terminals, and to provide a predictive tool to assess the impact of electrically long cables on CE measurements. The model is validated through numerical simulations of quadrilateral cable configurations considering both a homogeneous and inhomogeneous cross-section, highlighting the need to account for cable length in system design and EMC test interpretation.