Altera JNEye Manual do Utilizador descarregar pdf (Página 188)

• The first figure (top left) is a hybrid eye diagram that includes deterministic jitter and probability

density function (PDF) because of unbounded jitter and noise sources.

• The second figure (top right) contains the cumulative distribution (CDF) eye diagram with BER

bathtub curves (for both width and height in the eye diagram opening).

• The third plot (lower left) is a BER contour plot that shows the eye diagram opening area at various

BER targets.

• The fourth plot shows Q-Factor curves, which are another representation of BER bathtub curve using

Q-factor by assuming the noise/jitter is Gaussian.

With the Gaussian random jitter injected into the link, the BER bathtub and Q-Factor plots clearly show

the effects where this unbounded jitter narrows the eye diagram width as the BER target reduces.

Figure 4-10: TP1 Hybrid Eye Diagrams and BER Analysis Measured with Ideal Clock

The second set of TX outputs are measured with the golden CDR, which has a loop bandwidth of 1/1667

of the data rate. This set of outputs reflects the common lab scope measurement. With the golden CDR in

place, the low frequency jitter (such as the 1 MHz sinusoidal jitter) and noise, which are included in phase

noise and spurs, are tracked.

When you enable a PLL in a transmitter, the reference clock’s phase noise is shaped and filtered with the

PLL’s response. For a demonstration of PLL and transmitter reference clock phase noise, refer to the

JNEye Tutorial: PCI Express 8GT.

UG-1146

2015.05.04

Analysis

4-11

Tutorial: 28 Gbps OIF VSR Link with Arria 10 GT

Altera Corporation

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Altera JNEye Manual do Utilizador Página 188