We are thinking to use SERDES-IC[DS32EL0421SQ] of TI
in the www.ti.com/.../support , “Reach is 20 meters CAT6” is explained.
We understood the transmission frequency band width of CAT6 is 100MHz,
so that we would like to receive the technical reason why CAT6 cable can transmit 3.125 Gbps.
Hi Taka,
The transmission frequency bandwidth is not fixed for a specific cable type. The length of the cable also determines the frequency bandwidth.
The transmission frequency bandwidth of 100 MHz for CAT5 and 200 MHz for CAT6 is a common description for applications that use 100 meters of CAT cable. If the CAT cable length is reduced to be less than 100 meters, the transmission frequency bandwidth increases.
Below is an example of measurements taken for dB loss when using a 100m CAT cable:
In contrast, if you use a shorter cable, you will see significantly less attenuation loss. For example, below are measurements taken for a 5 meter CAT6 cable:
Comparing this graph with the 5-m CAT6 to the graph with 100-m CAT6, you can see that at 250 MHz, the 100-m CAT6 cable has ~37 dB loss. Meanwhile, the 5-m CAT6 cable only has ~3 dB loss at the same frequency. This means that the 5-m CAT6 cable can support transmission at higher frequencies until there comes a point at which the attenuation loss in the CAT cable becomes too excessive to support error-free transmission, even with the help of signal conditioning.
When testing, we determine the maximum amount of cable length that can be supported. Based on test data, the DS32EL0421 can support error-free transmission up to 20-m CAT6.
Regards,
Michael
