Power Electronics

Pulse Amplitude Modulation (PAM-4) Analysis Capability for Real-Time Oscilloscopes

Keysight Technologies, Inc. introduced measurement software designed to help engineers quickly and accurately characterize PAM-4 (pulse amplitude modulation with four amplitude levels) signals using the Keysight V-Series, Z-Series, and S-Series real-time oscilloscope platforms. The Keysight N8827A PAM-4 analysis software (for V- and Z-Series oscilloscopes) and N8827B PAM-4 analysis software (for S-Series oscilloscopes) provides comprehensive analysis of electrical PAM-4 signals.

Mobile computing applications are demanding more of the underlying computer Internet infrastructure. To enable increases in Internet and server-farm performance, higher-speed connectivity among server systems is required. Conventional communication techniques often relied upon NRZ (non-return-to-zero) encoding. Industry experts contend NRZ will not work in a 56-GBit/s environment. One way to overcome this challenge is to change the modulation technique from NRZ to pulse amplitude modulation. This allows engineers to dramatically increase the amount of data they can send across high-speed digital communication links.

Several industry standards bodies are actively promoting PAM-4 technology to enable the next-generation speed class and push higher data rates for a given channel compared to traditional NRZ signaling. While PAM-4 technology leverages some traditional NRZ measurement algorithms for PAM-4 signals, to fully analyze system performance, unique PAM-4 measurements and parameters are required.

N8827A/B PAM-4 analysis software offers measurements such as:

  • Eye width, eye height and eye skew
  • Level amplitude, level noise and level skew
  • Amplitude level linearity

Engineers can combine the N8827A/B PAM-4 option with existing Infiniium real-time oscilloscope software tools to provide even more powerful analysis capability:

  • PAM-4 equalizers (LFE, CTLE) using the N5461A InfiniiSim serial data equalization software
  • Embedding/de-embedding of PAM-4 channels using the N5465A InfiniiSim waveform transformation toolset
  • Jitter and amplitude analysis on IEEE JP03 patterns using the N8813A EZJIT Complete software tool

Multilevel signaling systems are particularly susceptible to noise, so the V-Series, Z-Series and S-Series real time oscilloscopes offer the industry's lowest noise floors for wide bandwidth real-time oscilloscopes. When using the 63 GHz Z-Series oscilloscope, for example, designers can achieve accurate analysis of electrical PAM-4 signals to 32 Gbaud. Additionally, engineers can perform offline analysis on stored PAM-4 signals using the N8900A Infiniium Offline oscilloscope analysis software installed on a PC.

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