4K-9000 USER MANUAL V1.1
© 2018 Smart-e (UK) Ltd
www.smart-e.co.uk
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In the example above, we have a 10V envelope signal, -5V to +5V, 10V peak-to-peak (p-p). Five discrete voltage
levels exist in the PAM-5 modulation, -5V, -2.5V, 0V, +2.5V and +5V. These voltage levels are purely for example
but displays the principal in a clear way. When used for 1Gb Ethernet, 4 of the voltage levels are used to
transmit 2 bits of data and the fifth voltage level is utilised for forward error correction (FEC). The maths from
this can then be shown to prove the bandwidth is satisfied:
𝐶𝑎𝑡5𝑒 𝑟𝑎𝑤 𝑏𝑎𝑛𝑑𝑤𝑖𝑑𝑡ℎ = 125𝑀𝐻𝑧 𝑜𝑟 125,000 𝑠𝑦𝑚𝑏𝑜𝑙𝑠 𝑝𝑒𝑟 𝑠𝑒𝑐𝑜𝑛𝑑
2 𝑏𝑖𝑡𝑠 𝑝𝑒𝑟 𝑠𝑦𝑚𝑏𝑜𝑙: 125,000 𝑥 2 = 250,000 𝑏𝑖𝑡𝑠 𝑝𝑒𝑟 𝑠𝑒𝑐𝑜𝑛𝑑 𝑜𝑟 250𝑀𝑏𝑝𝑠
4 𝑡𝑤𝑖𝑠𝑡𝑒𝑑 𝑝𝑎𝑖𝑟𝑠: 250𝑀𝑏𝑝𝑠 𝑥 4 = 1000𝑀𝑏𝑝𝑠 𝑜𝑟 𝟏𝑮𝒃𝒑𝒔
A more typical voltage envelope for transmission would be 2Vp-p, -1V to +1V. A comparison of PAM-5 and
PAM-16 can be used to explain how more discrete voltage levels has an adverse effect on a systems resilience
to noise.
Summary of Contents for 4K-RX9000
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