Although conductive coupling can be divided into resistive coupling, inductive coupling and capacitive coupling, in fact they often exist at the same time and are connected to each other.
1. Resistive coupling
2. Capacitive coupling
When the conductors in two circuits are very close and there is a potential difference, the electric field of the conductor in one circuit will induce the conductor in the other circuit; vice versa. The two interact and influence each other to change their electric fields. This kind of cross-linking is called electric field coupling.
The degree of field coupling in the two conductors depends on the distributed capacitance of the two conductors, that is, depends on the shape, size, relative position of the conductors and the properties of the surrounding medium.
Explanation: ①The voltage on the receiving circuit is proportional to the frequency. The higher the interference frequency, the more obvious the capacitive coupling. ②In the radio frequency circuit, a cable often contains multiple wires, and the interference on one wire can be coupled to all other wires, so the signal wire must be shielded. ③In the high-frequency amplifying transistor, the pins are most likely to produce distributed capacitive coupling, so the lead length of the pins should be shortened as much as possible.
3. Inductive coupling
Inductive coupling is mainly caused by electromagnetic induction. When a changing current flows in a loop, a changing magnetic field is generated in the surrounding space. This change and the magnetic field generates an induced voltage in the adjacent loop, so that an interference voltage is coupled to the receiving circuit.
4. Common ground impedance coupling
The common ground wire includes chassis ground wire, machine frame bonding wire, metal ground wire, ground network and ground bus.
5. Common power coupling
Common power supply coupling is conduction coupling caused by the internal resistance of the power supply, and common power supply coupling and interference always exist.
6. Ground wire impedance calculation and power supply internal resistance measurement
