E1 coaxial cable and method for shielding electromagnetic interference when connecting to E1 interface

Abstract

This invention discloses an E1 coaxial cable, which includes the coaxial outer signal backflow layer, the insulating layer and insulating jacket outside the backflow layer, the character of which is that the there also includes a metal shielding layer between the jacket and the insulating layer. This invention also discloses an electromagnetic shielding method when the cable connects with the E1 interface, the steps includes: electric connecting the metal shielding layer 406 with the earthing metal casing and the metal board at the place where the coaxial cable is imported into the subframe and the metal board of E1 veneer; or electric connecting the metal shielding layer 406 with the earthing metal casing, the subframe metal casing and the metal board.

Description

technical field [0001] The invention relates to a network equipment structure technology in the communication field, in particular to a structure of an E1 coaxial cable and a method for shielding electromagnetic interference when it is connected with an E1 interface. Background technique [0002] The International Telecommunication Union pointed out in ITU.TG.703 (2001, 11) "Physical / electrical characteristics of hierarchical digital interfaces" on the physical characteristics of the electrical interface of the synchronous data system: It is recommended to use the 75 ohm E1 coaxial cable at the receiving and sending ports The outer metal layer (outerconductor) is grounded; at the same time, it is also pointed out that when both the receiving and sending ends are grounded, the ground potential difference between the receiving and sending ends may lead to the existence of ground circulation, which may cause transmission errors (errors) or even permanent failure of the port ( p...

AI Technical Summary

Problems solved by technology

But because the receiving end cannot be grounded, the complete shielding layer of the E1 metal panel is destroyed by the insulating layer 405 (or the insulating layer 403 or the insulation distance of the air), and the electromagnetic interference on both sides of the panel will invade each other along the E1 line and cannot be isolated; The position where the E1 interface enters and exits the subrack and the rack. The insulating layer 405 destroys the shielding interface of the subrack and the rack. The electromagnetic interference inside and outside the subrack and inside and outside the rack will invade each other along the E1 line and cannot be isolated.

[0005] At present, there are two ways to solve this problem. One is to ground the receiving port through a small capacitor. The role of the small capacitor is to eliminate high-frequency interference. The other method is to install a core-through capacitor filter for signals on the interface. , the commonality of these two methods is that filtering needs to be performed on each receiving port, and it is difficult to implement when the number of ports is large and the equipment space is limited, and both methods only consider the EMC problem of the E1 interface itself, and do not consider the E1 interface is installed, the E1 line couples other interference in the subrack and the rack and takes it out of the rack, or the E1 line couples the interference outside the rack to the E1 line, and enters the rack and subrack along the cable (see image 3 )

Among the two methods, the cost of the former is lower, but the filtering effect is poor, and the high voltage withstand capability of the capacitor must be considered, while the cost of the latter is quite high