## Care with eye diagrams

#### Eye diagrams are a very powerful tool for visual diagnosis of the degree of distortion and noise introduced by the channel (including TX and RX processing) and of any errors in symbol timing recovery.

#### Often, however, it is not possible to observe the eye diagram at the correct point in the circuit, namely after any receiver filtering where the full (hopefully) Nyquist response should be seen, as this may be buried within an IC implementation. Under these circumstances it is necessary to duplicate any filtering following the observation point within the test hardware itself so that a representative eye diagram is obtained. |

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