Keysight Technologies Inc. introduced measurement application software designed to help engineers quickly and accurately measure and quantify PAM-4 (pulse amplitude modulation with four amplitude levels) signals. The software is used with the Keysight S-Series, 90000A, V-Series, 90000 X- and Z-Series real-time oscilloscope platforms and the 86100D DCA-X Infiniium sampling oscilloscope. The new Keysight N8836A PAM-4 analysis software (for S-Series, 90000A, V-Series, 90000 X- and Z-Series oscilloscopes) and the new N1085A PAM-4 analysis software (for 86100D oscilloscopes) provide comprehensive characterization of electrical PAM-4 signals based on the Optical Internetworking Forum’s Common Electrical Interface (OIF-CEI 4.0) proposed 56G interfaces, and the emerging IEEE 400 Gigabit Ethernet (P802.3bs) standard.
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, but excessive channel losses and crosstalk on 56 Gb/s NRZ links make this technology impractical for many applications. 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. However, there is not yet consensus within the governing bodies of communication standards as to how to measure PAM-4 signals for compliance.
“Our customers face new design and measurement challenges as they work to ensure their products are compliant with specifications that are incorporating PAM-4 signaling,” said Dave Cipriani, vice president and general manager of Keysight’s Oscilloscope and Protocol Division. “We’re working with industry leaders and standards organizations in these very early stages to help customers address these challenges and get to market quicker.”
The N8836A and N1085A PAM-4 measurement applications for S-Series, 90000A, V-Series, 90000 X- and Z-Series real-time oscilloscopes and 86100D DCA-X Series sampling oscilloscopes deliver measurements such as:
Linearity and output voltage measurements including level separation mismatch ratio (RLM)
- Eye width (EW) and eye height (EH)
- Jitter measurements including even-odd jitter and clock random jitter
- Differential and common mode return losses – performed using a Keysight time domain reflectometer (TDR) or vector network analyzer (VNA)
Multi-level signaling systems are particularly susceptible to noise, so Keysight’s V-Series, Z-Series and S-Series offer the industry’s lowest noise floors for wide-bandwidth, real-time oscilloscopes. For example, when using the 63 GHz Z-Series oscilloscope, designers can achieve accurate analysis of electrical PAM-4 signals to 32 GBaud and beyond. Additionally, engineers can perform offline analysis on stored PAM-4 signals using the N8900A Infiniium Offline oscilloscope analysis software installed on a PC.
The 86100D DCA-X combines low-noise, high-bandwidth receivers with an acquisition system that is particularly well suited for accurate characterization of PAM signals. The N1085A’s measurement capabilities are supported by a variety of DCA plug-in modules such as the 86108B 50-GHz precision waveform analyzer module, the N1045A 60-GHz module, or the N1055A 50-GHz TDR/TDT module. Engineers can use the N1045A and N1055A modules to analyze up to 16 PAM-4 channels simultaneously.