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MAY 2025 I DESIGN007 MAGAZINE 67 ever there are changes in field patterns. For outer traces (microstrip), most of the electro- magnetic field is contained within the dielec- tric material, while a smaller portion is in the air. e part of the field in the air travels more quickly, which causes the leading edge of the signal to spread out. is stretching of the sig- nal impacts the characteristics of the crosstalk. Crosstalk is caused by capacitive and induc- tive coupling (Figure 3). Capacitive coupling causes signal voltages to couple into nearby nets, also referred to as forward or far-end crosstalk (FEXT). Capacitive coupling can lead to unintended interference in the affected conductor, typically observed as noise or sig- nal distortion. High-frequency signals are par- ticularly susceptible to capacitive coupling due to the stronger and more dynamic electric fields they generate. Inductive coupling also causes signal cur- rents to couple into nearby nets, a process referred to as backward or near-end cross- talk (NEXT). e magnetic component of cross-coupling can distort signals, especially in high-speed circuits where rapid changes in current produce stronger and more dynamic magnetic fields. ese distortions can mani- fest as noise or unintended signal deviations in nearby conductors. Factors Influencing Capacitive Coupling • Proximity: e closer the conductors are, the higher the capacitance between them, leading to stronger coupling. • Voltage levels: Higher voltages on the source conductor create stronger electric fields, increasing coupling. Factors Influencing Magnetic Coupling • Proximity of conductors: e closer the conductors are to each other, the stronger the magnetic coupling due to increased mutual inductance. • Current variations: Rapid changes in cur- rent generate dynamic magnetic fields that can intensify coupling effects. • Orientation and geometry: e layout and relative orientation of the conductors impact the direction and strength of the magnetic field, influencing how coupling occurs. • Frequency: Higher frequency signals tend to generate stronger magnetic fields, increasing the likelihood and intensity of coupling. Mitigation Techniques • Spacing: Increasing the distance between conductors. Alternatively, if real estate is of concern, decrease the trace-to-plane spacing. Figure 3: The mutual inductance and mutual capacitance coupling in parallel transmission lines.