The most important requirement for any design is to have data transmitted between receiver and transmitter without any issues. The channel between the driver and receiver must be error less. One of the parameter to consider in this scenario is bit error rate (BER).
Bit Error Rate occurs due to the Inter Symbol Interference (ISI) in the channel. ISI is common problem experienced by engineers working on high speed designs. When ISI occurs, the major problem is that receiver cannot distinguish the data bits (as HIGH or LOW). For the ISI to occur, specific bit sent at a time must be interfering with the next bit. One of the reasons why this happens is due to the degradation of the rise time which is a major signal integrity issue.
When a signal travels from driver to receiver, it has to travel over a PCB trace. The PCB traces start acting as transmission lines beyond a certain signal frequency. The problem with the high frequency signals is that the characteristics of the signal vary as per frequency. High frequency signals get attenuated more than the low frequency signals which causes the rise time degradation. Higher rise time degradation further causes Inter symbol interference.
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