Technical Insights

Testing solutions for USB4 - Universal Serial Bus 4

2020-08-20  |  3 min read 


The USB Implementers Forum (USB-IF) announced USB4 in March 2019 and released the specification in September 2019. Based on the Thunderbolt 3 protocol, USB4 uses a Type-C connector, which enables bonding of two independent 20 Gb/s links into one logical 40 Gb/s link. USB4 supports other standards through ALT mode. The host implements USB 3.2 at 5G / 10G, USB 2.0, and DisplayPort (DP) and can tunnel USB, DP, and PCIe®. Keysight offers a suite of hardware and software tools to help you design and implement USB4.  

Figure 1. Typical USB4 implementation requirements, per USB-IF USB-IF



USB4 has seen significant changes compared with USB 3.2. These are some of the testing differences in the USB4 implementation: 

return loss Tx and Rx retimer-specific measurements
calibration required for transmitter equalization cross-talk generation
calibration required for receiver equalization  new jitter measurements
doubling of PHY bit rate from 10 Gb/s to 20 Gb/s new phase and slew rate measurements
signaling on all four Type-C high-speed pairs added skew measurements
de-embedding of test cables common mode interference
new link loss budgets for 10G / 20G separate jitter cocktails for 10G / 20G / TP2 / TP3
link optimization prior to bit error ratio test built-in error detector


Figure 2 provides a comprehensive overview of hardware and software needed to complete transmitter and receiver tests for USB4 Type-C. 

Figure 2. Keysight USB4 Type-C solution matrix
Figure 2. Keysight USB4 Type-C solution matrix


The USB4 Type-C solutions matrix uses the following tools:



Keysight offers a suite of testing solutions that will help you implement your USB4 design, including testing all supported technologies: 

•    protocol
•    USB power delivery
•    channel characterization
•    sideband testing
•    Thunderbolt
•    DisplayPort

As described, Keysight offers instrumentation, software, and fixtures for testing and characterizing the entire USB4 Type-C ecosystem.