We use cookies to improve your online experience. By continuing browsing this website, we assume you agree our use of cookies.

What are the functions of network transformers?

Views : 120
Author : CETUS INTL
Update time : 2023-08-17 11:43:14
Why use a network transformer? What are the functions of network transformers? This article will answer them one by one.

1.Features of Network Transformer
To send data, it uses a filter to improve the signal. Then, it connects the improved signal to the other end of the network cable. Electromagnetic field conversion makes this connection.

2. Electrical isolation Lightning protection
When a CMOS chip is working, it always creates a signal level higher than 0V, based on its process and design. The PHY output signal will lose its DC component if it is sent over 100 meters or more. This loss is significant. If you connect the network cable directly to the chip, thunder and static electricity can easily damage the chip.

The equipment's grounding method differs, and the varied grid environment leads to inconsistent 0V levels between the two units. When A transmits a signal to B, the disparity in their 0V levels can significantly influence the outcome. Electrical current flows from a device with a higher potential to one with a lower potential.

The network transformer improves the signal sent by the PHY. It does this by using a filter.

After improving the signal, the network transformer sends it through the network cable. It does this by converting it into an electromagnetic field. In this way, the network cable and PHY do not have a physical connection. The signal transfers without the DC component, enabling data transmission in devices with different 0V levels.

The network transformer can withstand the voltage of 2KV~3KV. Also played a role in lightning protection.

Thunderstorms can easily burn out some friends' network equipment. Unreasonable PCB design causes most of them, and they burn the interface of the equipment. The transformer protects and prevents a few chips from burning.

Isolation transformers can satisfy the insulation standards of IEEE802.3, but they are incapable of suppressing EMI.

3. Rejection of Common Mode
Every wire in a twisted pair coils around the other in a double helix formation. This spiral shape confines the magnetic field produced by the current passing through each wire.

The direction of the current in the wires dictates the amount of noise produced by each wire pair. The amount of noise caused by the current flowing on each pair of wires is different.

The noise caused by the current flowing on each pair of wires varies. The differential mode current causes minimal noise. Therefore, the main factor that determines the noise is the common mode current.



Twisted Pair's Differential Mode Signal
Differential mode signals convey the current in contrasting directions on each wire within a wire pair. If you wound the wires evenly, the currents would create equal but opposite magnetic fields. These magnetic fields cancel each other out, resulting in the cancellation of their outputs.

Common mode signal in twisted pair
The current flows in the same direction on both wires and goes back to the ground through Cp's capacitance. In this situation, the currents generate magnetic fields of the same size and direction, and they cannot nullify their effects. 

Understanding Common Mode, Differential Mode Noise and their EMC
There exist two classifications of noise in cables: radiated noise and conducted noise, which originate from power and signal cables. Further subdivisions include common mode noise and differential mode noise.

Internal noise voltage in electronic devices causes differential mode conduction noise. It flows in the same path as the signal or power supply current.

To reduce noise, you can connect the signal line and power line in a few different ways. One option is to use choke coils, capacitors, or a low-pass filter made of capacitors and inductors. By doing this, you can effectively decrease high-frequency noise. This helps to decrease high-frequency noise.

The electric field strength decreases as the distance from the cable to the observation point increases. It also increases with the square of the frequency. Additionally, it increases with the current and the size of the current loop.

It also increases with the square of the frequency, and with the current and the size of the current loop. To reduce radiation, you can add an LC low-pass filter at the signal input. This filter will stop noise current from going into the cable.

In short, the network transformer performs these functions and we still need to use one.