What is the difference between an Ethernet transformer and a network filter?
Time:2022-09-01
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What is the difference between an Ethernet transformer filter
Network transformers include T1/E1 isolation transformers; ISDN/ADSL interface transformers; VDSL high-pass/low-pass filter modules, interface transformers; T3/E3, SDH, 64KBPS interface transformers; 10/100BASE, 1000BASE-TX network filters; RJ45 Integrated transformer; special transformers can also be designed according to customer needs. The products are mainly used in: high-performance digital switches; SDH/ATM transmission equipment; ISDN, ADSL, VDSL, POE power receiving equipment integrated service digital equipment; FILT optical fiber loop equipment; Ethernet switches, etc., such as YL18-2050S of Yutai Electronics , YL18-3002S, etc. are more common!
The data pump is a device that is available on consumer-grade PCI network cards. The data pump is also called a network transformer or a network isolation transformer. It has two main functions on a network card. One is to transmit data. It couples and filters the differential signal sent by the PHY with a differential-mode coupled coil to enhance the signal, and couples it to different levels through the conversion of the electromagnetic field. Connect the other end of the network cable; one is to isolate the different levels between different network devices connected by the network cable to prevent the transmission of different voltages through the network cable from damaging the equipment. In addition, data mercury can also play a certain lightning protection role for the equipment.
network filter
Maybe the filter designed for the network is the network filter.
(1) According to the frequency band of the signal passed, it is divided into four types: low-pass, high-pass, band-pass and band-stop filters.
Low-pass filter: It allows low-frequency or DC components in the signal to pass, and suppresses high-frequency components or interference and noise.
High-pass filter: It allows high-frequency components in the signal to pass and suppresses low-frequency or DC components.
Band-pass filter: It allows signals in a certain frequency band to pass, and suppresses signals, interference and noise below or above the frequency band.
Band-stop filter: It suppresses signals within a certain frequency band and allows signals outside this frequency band to pass.
(2) Divided into analog filter and digital filter according to the processed signal.
(3) According to the components used, it is divided into passive and active filters.
Function: electrical isolation; common mode rejection; common mode, differential mode noise and its EMC
In Ethernet equipment, when connecting RJ45 through PHY, a network transformer will be added in the middle. Some transformers have their center tap connected to ground. And when the power supply is connected, the power supply value can be different, 3.3V, 2.5V, and 1.8V are available. The role of this transformer is analyzed as follows:
1. Why are some of the middle taps connected to the power supply? Some ground? This is mainly determined by the driving type of the UTP port of the PHY chip used. There are two types of driving, voltage driving and current driving. The voltage-driven one should be connected to the power supply; the current-driven one should be directly connected to a capacitor to the ground! Therefore, for different chips, the connection method of the center tap is closely related to the PHY. For details, please refer to the datasheet and reference design of the chip.
2. What is the function of this transformer, can it not be connected? In theory, it is possible to connect it directly to the RJ45 without the need for a transformer, and it can work normally. However, the transmission distance is very limited, and when it is connected to a different level network port, it will also have an impact. And the external interference to the chip is also very large. When connected to the network transformer, it is mainly used for signal level coupling. First, it can enhance the signal and make the transmission distance longer; second, the chip end is isolated from the outside, the anti-interference ability is greatly enhanced, and a great protection effect (such as lightning strike) is added to the chip; When it reaches the network ports of different levels (for example, some PHY chips are 2.5V, and some PHY chips are 3.3V), it will not affect each other‘s devices.
3. Why do you connect different voltages when connecting to the power supply? This is also determined by the UTP port level specified in the PHY chip data used. What level is decided, you have to connect the corresponding voltage. That is, if it is 2.5v, it will be pulled up to 2.5v, and if it is 3.3v, it will be pulled up to 3.3v.
