What does common mode rejection mean -- Gigabyte network transformer factory

Ethernet interface network transformer

Network transformer is also known as Internet isolation transformer, Ethernet interface transformer and network filter. The products are divided into single port, double port, multi connector, 10 / 100base, 1000Base-TX and RJ45 socket integrated Internet isolation transformer. The products are mainly used in RJ45 network port, Ethernet switch, network router, ADSL, VDSL large digital machine equipment, EOC terminal equipment, EPON / GPON three network integration machine equipment, network set-top box, intelligent TV, network camera, SDH / atmsdh / ATM, PC main board interface, industrial main board and other machine equipment.

Each wire in the twisted pair shall be surrounded by each other in a double helix structure. The magnetic field caused by the current passing through each wire of the selected Ethernet filter price is controlled by the spiral shape. The current direction of each conductor in the twisted pair determines the noise level of each pair of conductors. The transmission level caused by the difference mode current and the common mode current on each pair of wires is different, and the noise transmission caused by the difference mode current is smaller, so the key of noise is decided by the common mode current.

1. Differential mode data signal in twisted pair

For differential mode data signal, its current on each wire is transmitted on a pair of wires in reverse direction. If this pair of wires are wound symmetrically, this reverse current will cause the same size and opposite direction of the electrode magnetic field, so that its output is opposite to each other.

2. Common mode data signal in twisted pair

Common mode current flows in the same direction in two wires. Choose the price of Ethernet RJ45 connector and return to the ground through parasitic capacitance CP. In such a case, the current causes a magnetic field of the same size and rotation, and their output cannot be matched with each other. The common mode current creates an electromagnetic field on the stranded surface, which works just like a wireless antenna.