Crosstalk Combinations — Lesson 2

This lesson covers the concept of crosstalk or near field coupling, focusing on capacitive and inductive coupling. It explains the interaction between two circuits, the source circuit and the victim circuit, and how the coupling capacitors play a role in this interaction. The lesson further delves into the nodal analysis of the circuit, the character of capacitor coupling, and how to simplify the analysis. It also discusses how to model capacitive coupling and methods to reduce it. The lesson then shifts to inductive coupling, explaining how to model it and methods to reduce it. For instance, the use of twisted pair cables to minimize both inductive and capacitive coupling is discussed.

Video Highlights

00:12 - Capacitive coupling between two circuits
05:52 - Gauss’s law and current injection
11:32 - Inductive coupling and how it is modelled as a mutual coupling
19:34 - How to reduce inductive coupling
22:36 - Use of twisted pair cable to minimize both inductive and capacitive coupling
26:59 - Review of mitigation techniques

Key Takeaways

- Capacitive and inductive coupling occur between two circuits, the source circuit and the victim circuit.
- Capacitive crosstalk increases with frequency or fast-changing voltages and is more dominant in high impedance circuits.
- Inductive coupling is more dominant in low impedance circuits where there is the possibility of driving larger currents.
- Capacitive coupling can be modelled as a current injection, while inductive coupling can be modelled as a series voltage source.
- Methods to reduce capacitive crosstalk include reducing the surface area of conductors, increasing the distance between conductors, and introducing a ground plane close to the parallel conductors.
- Methods to reduce inductive coupling include reducing the mutual inductance, reducing the loop area of the circuits, and orienting the loops in such a way that one loop surface is normal to the other.