SER Jitter Bathtub
The SER Bathtub graph plots TJ data and dual-Dirac SER values across an entire symbol period, which is labeled as the unit interval (UI) on the horizontal axis. The dual-Dirac SER values are calculated using DJ (δ-δ) and RJ and are used to extrapolate to low SER levels. In general, the dual-Dirac values will differ from the measured TJ values at high probabilities, but the two should converge at low probabilities. The SER value that is used for calculating TJ can be changed from its default value of 1E-12. You can also toggle the graph between SER or Q-Scale values. Use selections in the Advanced tab located on the Configure Jitter Measurements dialog to configure these settings. The graph title changes depending on the scale selection: SER Bathtub or Q-Scale Bathtub.
For a PAM waveform, on the graph repeatedly click the Cycle Eye button to cycle through the waveform eye on which the histogram is based. For NRZ waveforms, which only have one eye defined by two levels, there is no selection. To globally specify the PAM eye for all affected graphs:
- Click Measure > Configure Jitter Mode Measurements to open the dialog.
- In the dialog, select the Jitter Measurements tab.
- In the Show Graphs Based on field, select the desired eye.
The global setting effects all Time graphs except RJ/PJ and Aliased Jitter Spectrum.
