Their views: the core component, Ethernet PHY chip should be near the interface card
Reason: Ethernet PHY chip to the board core device go agreements are generally RGMII, GMII is single side walk the line, but PHY chip to the transformer is the differential line, differential line strong anti-jamming capability, single-ended is weak, so the core component, Ethernet PHY chip should be near the interface card
CodePudding user response:
According to the analog circuit to analyze, transformer from PHY, near and far from the RJ45, PHY from the MAC/CPU chip, has no impact on the electrical signal is, but in fact still have bigger difference,PHY is parallel digital signal into a high-speed serial difference signal for long distance transmission,
Parallel digital signal transmission is limited by many in the PCB, frequency, noise, attenuation and so on, is much less than the difference line on the PCB transmission distance, high frequency,
Parallel digital signal transmission on the PCB, the biggest problem of anti-interference ability is poor, line interference, especially the characteristics of the differential signal is strong anti-interference ability, but because of the difference signal frequency is generally greater than the parallel digital signal and high frequency attenuation is the main reason influencing difference line transmission distance,
Ethernet device of network transmission distance (Ethernet) 100 meters, the need to control strictly the impedance matching, small line attenuation, strong anti-interference ability to 100 meters, with five types of twisted pair, for instance six kind of twisted pair,
PCB line width, the base material loss at high frequency is greater than 5 kind of twisted pair by numerous, in gigabit networks, reduce the length of the cables on the PCB is very important for the 100 m network transmission technology,
PCB board of electromagnetic interference than twisted-pair (good twisted-pair and shielding), reduce the high frequency line go line length can reduce the circuit board on the interference of high frequency line,
Adopt high-frequency PCB, of course, the ideal control PCB copper thick line width reduction go line loss at high frequency, the cost is high, also can walk long distances line on the PCB,
In some of the network interconnection equipment cabinets cabinets, regardless of the transmission distance, also can walk long distances line on the PCB,
Transformer is still has an important role in isolation, cable and PCB components through the circular physical isolation, to improve the reliability of the products, you can think like this, Internet was struck by lightning, the equipment can not damage, requires that the distance between the transformer and the RJ45 as small as possible,
CodePudding user response:
You found the reason have to trust their own judgment, conformity of articles online