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【 Cable testing 101 question-and-answer series 】 — — Far end crosstalk and near end crosstalk

by:FOT     2020-07-17
【 Cable testing 101 question-and-answer series 】 — — Far end crosstalk and near end crosstalk test if you are very familiar with copper, it is likely heard of crosstalk - — A couple or a channel on the transmission of signal adverse impact on another pair or a channel. Crosstalk to concrete formed a pair of wires or the whole cable interference, cause error or cannot transfer data. For example, did you ever hear someone else on the phone? This is the mutual interference between adjacent lines. But you understand test balance copper network wiring system near end crosstalk and far end crosstalk parameters between the difference? As part of our 'cable test 101 asked' series, we think that is worth in-depth understanding of it. Proximal near end crosstalk, abbreviated as NEXT, is to measure a single link/channel performance parameters, measured from a pair of line coupled to the other a pair of signal lines. Cause interference lines to referred to as 'line on the', and the influence of crosstalk line to be called 'by interference lines'. NEXT to db ( dB) For the unit, said changes over transmission frequency, high frequency interference. The dB value, the greater the crosstalk interference link/channel by the smaller. For example, can carry up to 100 MHz category 5 e cables, at 20 MHz in the NEXT value may be 45. 8 dB, but in the NEXT value may be 35 of 100 MHz. 3 dB, the low frequency when the NEXT performance is better. Measurement results are referred to as 'near end crosstalk is because measurement link at the end of the signal source/channel crosstalk. Twisted-pair cable is conducive to offset the NEXT - — Each pair of different online for heave rate can prevent the line from the adjacent line to pick up the signal. So ensure the line on the ground near the terminals as far as possible is very important. Each type of line to ground rate also in view of the crosstalk performance optimization, and to improve the isolation. So, for six kinds of cable support 250 Mhz, 100 Mhz at the time of the NEXT value is 44. 3 dB, and 5 e class line at the same frequency of the NEXT value is 35. 3 dB。 Power and near end crosstalk, abbreviated PSNEXT, are all simple summation of measurement value of adjacent line to the NEXT. NEXT said cable in 4 of line 3 to line respectively in another 1 crosstalk caused by online. PSNEXT is the sum of all three pairs of adjacent line of crosstalk, said the network all 4 of line in the transmission signal ( For example base - 1000 T) , the impact on line 1. After a little more, is also very important, near end crosstalk test including PSACRN - — Near end crosstalk and attenuation ratio (power Called PSACR before, but in order to distinguish it from below introduction PSACRF, changed the name) 。 Using the PSNEXT and insertion loss value ( See 'cable test 101 asked' about the content of the insertion loss of the series) Calculated, that each pair of lines of attenuation and from the other three on line receiving the combination of crosstalk between different. Purpose is to ensure that the received signal is compared with the noise of the cable is strong enough. The higher the PSACRN value, the better the performance. The remote far end crosstalk abbreviated FEXT, also measured within a channel. Far end crosstalk and NEXT there are many similarities, but in the remote measurement of channel. FEXT itself, however, don't tell the attenuation of signal within a certain distance. To provide more information as a result, the attenuation ( Insertion loss) Remove from the FEXT results, referred to as the equivalent far-end crosstalk. In recent years, more, TIA will be renamed the parameters of the remote attenuation crosstalk ratio, ACRF for short. And NEXT, the three interference lines ACRF measurement result sum of each pair of power and ACRF ( PSACRF) 。 TIA before modifying the parameter name, past refers to power and ELFEXT PSACRF parameters ( PSELFEXT) 。 What about external crosstalk? In order to support gbase - 10 T application and upgrade to a higher frequency of 6 a after class, we must now concern not just between cable crosstalk within the cable. In the next 101 q series, we will explore external crosstalk parameters ( Remind: there are multiple arguments) 。 If you have any questions or problems, you are welcome to contact us at any time
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