By PURPLELEC | 06 December 2024 | 0 Comments
How to test USB4
Testing USB4 involves multiple aspects, including transmitter testing, receiver testing, and overall system compatibility testing. The following is a detailed test guide:
I. Transmitter testing
The transmitter test mainly verifies the quality and consistency of the signal sent by the USB4 device. The test content includes signal integrity, jitter index, eye diagram, etc.
1. Test equipment:
High-performance oscilloscope: used to capture and analyze the signal sent by the transmitter.
USB4 Microcontroller: used to control the device under test to generate the corresponding test pattern.
Test fixture, low-loss phase-matched cable and other auxiliary equipment.
2. Test steps:
Connect the test equipment, including oscilloscope, USB4 Microcontroller and device under test.
Run USB4ETT software on the control PC and control the device under test to generate test pattern through USB4 Microcontroller.
The oscilloscope captures and analyzes the signal sent by the transmitter, including signal integrity, jitter index, eye diagram, etc.
According to the test results, adjust the parameters of the device under test to meet the specification requirements of USB4.
3. Notes:
It is necessary to support two application scenarios, active cable and passive cable, and perform near-end test and far-end test respectively.
When performing far-end test, it is necessary to consider the influence of passive cable and use the algorithm of software to simulate the reference link.

II. Receiver test
The receiver test mainly verifies the performance of USB4 device when receiving pressure signal, including bit error rate, burst bit error rate, frequency deviation, return loss and other indicators.
1. Test equipment:
High-speed bit error meter: used to generate and calibrate pressure signal and measure bit error rate.
High-bandwidth oscilloscope: used to calibrate pressure signal and monitor receiving end signal.
Network analyzer: used to test the return loss of receiving end.
2. Test steps:
Use the pattern generator of high-speed bit error meter to generate pressure signal with pre-emphasis, sinusoidal jitter, random jitter, spread spectrum clock and common mode noise.
Use high-bandwidth oscilloscope to calibrate pressure signal to ensure the accuracy and consistency of signal.
Inject the calibrated stress signal into the receiving end of the device under test.
Measure the bit error rate, burst bit error rate and other indicators of the receiving end, and record the test results.
Use a network analyzer to test the return loss of the receiving end to ensure that it meets the specification requirements.
3. Notes:
Two scenarios need to be tested: no USB cable plugged in and USB cable plugged in (simulating the maximum and minimum link loss).
Before injecting the stress signal for bit error rate testing, it is necessary to ensure that the pre-emphasis of the pattern generator is in the optimal state.
III. Compatibility test
The compatibility test mainly verifies the compatibility of USB4 devices with other USB devices and systems.
1. Test equipment:
Various USB4 devices, USB3.x devices, Thunderbolt devices, etc.
USB4 switch or hub: used to connect multiple devices for testing.
Test software and driver: used to control the device under test and collect test results.
2. Test steps:
Connect various USB4 devices and other USB devices to the USB4 switch or hub.
Run the test software to perform test items such as data transmission, power management, and device identification.
Record the test results and check whether there are compatibility issues or errors.
According to the test results, adjust the parameters or drivers of the device under test to improve compatibility.
3. Notes:
It is necessary to ensure the stability of the test environment and test equipment to avoid interference and errors.
It is necessary to test a variety of devices and scenarios to ensure that all possible compatibility issues are fully covered.
In summary, testing USB4 involves multiple aspects and complex steps. In order to ensure the accuracy and reliability of the test, it is necessary to use professional test equipment and software and follow standardized test processes and methods.
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