Why Not DFE or Only-1tap Digital DFE in ADC-DSP RX?

[@parkerm6514]

Timing and Complexity, in conclusion.😮

[@circuitimage]

Hi PARKER, nice to meet you. Correct. :)

[@abhiruplahiri1]

Hi CC, why does the reference you shared additionally uses a 1tap DFE when 14tap FFE is used? Is the FFE not sufficient for equalisation?

[@circuitimage]

Hi Abhirup, thanks for the good question.
The 1tap DFE is not sufficient for equalization if there's no FFE.
On the other hand, 1tap DFE + 14tap FFE might be sufficient for equalization for a less discontinuity (or smooth) channel characteristic.
But, that should not be sufficient if the loss is > 40dB with lots of discontinuity. So, it depends. :)

[@abhiruplahiri1]

Thanks CC for the message. I gave it a thought and seems DFE can still help in not doing noise amplification while a FFE does noise amplification. So it seems to be a compromise between two types of equalisation, using FFE and DFE. Having long FFE and 1 tap DFE seems to be a very good idea!

[@circuitimage]

@@abhiruplahiri1 Hi Abhirup, thanks for the additional information & thoughts.
I agree with you that the 1-tap DFE without noise amplification and FFE could help other residual ISI & reflection, without adding too much noise amplification; therefore, that's a good compromise/optimization.