Why DFE?

The Decision-Feedback Equalizer (DFE) is one kind of equalizers in communication system. To provide an intuitive image, we went through other equalizers' limitation and emphasize the DFE's strength images such that everyone can follow the needs of DFE easily.

[po-yaohsu]

Really helpful！Since SerDes is a rare topic in school, it is hard for me to start from the begining. I've learned a lot through the videos, thx.

[madhooz]

Hi Sir, I am really fortunate to watch your videos for understanding the concepts in SERDES. Your videos are very simple to understand the blocks, their requirements and functionality. Thanks a lot for your videos.

[hanyueli]

Thanks for your video, I have a question for the eye diagram at 8:17. Is the green eye diagram what we want to have, such that at the clock rising edge, there are 4 different levels? But the input has only 2 levels, so I am confused why the green one is better than the red one. Thanks!

[MinhPham-jegt]

Thanks for the presentation.
I got one question: why is the DFE immune to noise and crosstalk. Noise and crosstalk will be present in the input of DFE, how could DFE know how to make the decision?

[Erichsu-em]

Hi Dr.Cheng, thanks for the great video.
I'd like to inquire one question which is the tap, can I take tap as a filter since if DFE have more taps, it means DFE can cancel more post-cursor ISI and if FFE has more tpas, it can cancel more pre-cursor ISI, and if we increase more tpas, it means we need more flip-flps, so it will increase the area. Please correct me if I'm wrong.
Thank you again.

[ams_designer_]

Just saying thanks for this, thank you so much

[sumanchowdhury]

Thanks for the video. I have a question. The minimum amount of Swing at the Slicer input is decided by "BER/Slicer input noise/Sensitivity/offset" ? What limits the max side? Can we have very High Swing at the Slicer input for both High and low frequency components of the signal?

@1:40 : You tell for less dynamic range, sampling accuracy be increased or clockJitter power requirement is reduced? Can you explain in some more detail?

[MangoLin]

Sir, if I have 4-tap DFE, may I just use 2nd, 3rd and 4th tap and turn off 1st tap?
In this situation, will this DFE work or not?

[ssayank]

Thank you very much for your great videos. Just a dull question, would you please explain, why a bumpy response would create a reflected waveform time domain? And why they are created in 3UI, 6UI and so on?

[顏擇敏]

Hi sir, thanks for the sharing amazing video. I'm wondering why DFE only cancel the post cursor(signal falling edge) due to at next bit may create nonzero value? No impact of pre cursor(signal rising edge) if the nonzero value is negative?

[zhenglai]

Very nicely put presentations and I learnt something new! At 6:40 you mentioned that propagation error is usually not a big issue. As the speed increases, closing the timing of the first tap could be difficult due to many number of taps being implemented at the summing node. I am wondering what's your thoughts about the error propagations due to the difficulties of closing the first tap at high speed design? Appreciate it. Thanks again!

[varsrcb]

Hi Chen, nice videos! could you please explain how FFE has noise amplification problem?

[hrachya_khachatryan]

Very good channel, liked and subscribed!
Two questions.
1) Is the DFE a FIR filter ? like TXFFE.
2) I imagine that DFE has a high pass frequency response but with bumps. While in your TXFFE video, frequency response of the TXFFE is more similar to CTLE (no bumps). This is surprising, because it seems to me that TXFFE and DFE are very similar to each other...
Thanks

[jimmyma]

Thanks for the video, I have a question about DFE error propagation. How do we ensure DFE error propagation doesn't make compliance test fail ? Is there any "simple" method to evaluate it?

[ZanZ-qiwz]

Hi Teacher, I have been enjoying your videos. Thanks! I have some question. It seems the DFE can reduce the ISI by suppressing the post cursor, where educing the ISI can improve the Voltage margin, that is the eye height, correct? Does DFE improves eye width? It seems to me both CTLE and DFE improves eye height only, Is there any receiver parameters can improve eye width especially the eye left and right are not equal/balance?

[initiate_si]

What is the meaning of taps in DFE? (1 tap, 2 tap, 3 tap etc)