Generate PAM4 signals for receiver compliance testing: Page 3 of 5

September 26, 2016 //By Alexander Katsman, Adsantec
56 Gbit/s links are moving to PAM4 signalling as a way to overcome channel bandwidth issues. As this modulation technique takes hold, you'll need to generate variety of signals to test receivers under varying distortion conditions. Stress testing a receiver can help you understand a receiver’s weaknesses and measure its tolerance to various signal impairments.

Additionally, SJ (sinusoidal jitter) can be added to one or both of the bits of the PAM4 test signal to further decrease the eye opening. Figure 4 shows a 25 Gbit/s PAM4 signal without any added SJ. Figure 5 shows 0.2 UI (unit interval) of SJ at 10 MHz added to both the MSB and LSB simultaneously.


Figure 4: A 25Gbit/s PAM4 signal with no added SJ shows relatively clean eyes.

 

Figure 5: 25 Gbit/s PAM4 signal with 0.2 UI of added SJ at 10 MHz shows smaller eye openings that seen in Figure 4.

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