loose-electron
Senior Fellow
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Best Design Tool = Capable Designers
Posts: 1638
San Diego California
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Stability in a DFE system is non-linear in nature. As well, it is a sampled time system, so a conventional linear systems feedback system model is not applicable.
As well, the feedback amplitude is fixed in nature (make a decision and feed it back) so a "gain/phase around the loop" does not apply.
What is the DFE getting used for? I spent 2 years doing these things for disk drives and they do not work reliably. When you start adding in noise, signal input amplitude variance, timing dispersion, etc, etc, to the input signal, the DFE architecture starts to have a lot of problems. When you get that down into a chip and add process variance onto all of the above, it totally falls apart.
The concept is simple, and the math model looks good, but when you add the details of real world signals, and semiconductor limitations, there are a lot of problems.
Jerry
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