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Drivers and passengers can now enjoy in-premise entertainment activities, such as music and video streaming, right in the comfort of their cars. This is made possible due to the advancement of car Ethernet. To ensure a faster and stable transmission, the Open (One-Pair Ether-Net) Alliance has released conformance requirements, including TC2-100 Base and TC9-1000, for the radio frequency validations of cables and connectors on the physical layer. In this article, we are going to introduce the test details of TC9 (Frequency within 1~600MHz) and the type of testing instruments used in the validations.
Car Ethernet- The 3 Test Cases for TC9 Test Scope: Cables, Connectors, Communication Channels
Connector (SCC Context)
Cable and Channel (SCC Context)
Whole Communication Channel (SCC Context)
The Impact of Interference on Signal Strength
Environment System Context
When operating in a complex environment, the quality of signal strength does not only depend on the features of channels, as different signals might interfere with each other and cause signal distortions. As for multi-lane products, in addition to the validation of standalone communication channels, the interference of the environment system should also be taken into account.
| Types | Item |
| Connectors | PSANEXT Loss(Sdd31, Sddyx)PSAFEXT Loss (Sdd41, Sddyx)
AFEXTDC Loss(Sdc41 , Sdcyx) AFEXTDS Loss(Sds45 , Sdsyx) |
| Cable and Channel- Informative | ANEXT Loss(Sdd31 , Sddyx)AFEXT Loss(Sdd41 , Sddyx)
AFEXTDC Loss(Sdc41 , Sdcyx) AFEXTDS Loss(Sds45 , Sdsyx) |
| Whole Communication Channel | PSANEXT Loss(Sdd31, Sddyx)PSAACRF (Sdd41, Sddyx)
AFEXTDC Loss(Sdc41 , Sdcyx) AFEXTDS Loss(Sds45 , Sdsyx) |
For accurate measurements, the testing environment or fixture is required to meet certain standards. The length of cables should not exceed 15 meters with a maximum of 4 connectors. Improper rolling or placement of DUTs or even conductive platforms may cause interference and distort measurement accuracy. It is important to use platforms or conductive drums to hold the DUTs while testing.
Image by Allion Labs
Source: Adapted from IEEE 100BASE-T1 Definitions for Communication Channel.
The key to choosing Test Tools & Fixtures for TC9 tests
Fixture Requirements: low insertion loss rate, the symmetry of differential signal, and high impedance
The impedance requirements are higher than commercial products:
| Impedance | Tolerance | Condition |
| 100 Ω | ±5% | 50 ps |
| ±10% |
Source: Adapted from Channel and Components Requirements for 1000BASE-T1 Link Segment Type A.
Fixtures measurements require the differential trace to be less than< 30mm, the test parameter of symmetry of differential signal is determined as LCL (Sdc11)
Image by Allion Labs.
Source: Adopted from Channel and Components Requirements for 1000BASE-T1 Link Segment Type A.
Since Ethernet cables can reach 15 meters and the limitations of cable placements, regular conductive tables will not be suitable for Ethernet validations. Instead, we use the conductive drum to minimize the area of measurements. For more information on Conductive Drum, contact us at service@allion.com
A seamless product testing journey
Generally speaking, after the calibration of equipment, we need to verify whether the environment meets the testing requirements, and we do so by utilizing mode conversion and return losses. The noises of testing instruments will cause distortions and affect the accuracy of measurements.
Verification of VNA calibration accuracy- Return Loss
Image by Allion Labs.
Verification of VNA calibration accuracy- LCL
Image by Allion Labs.
Verification of VNA calibration accuracy- LCTL
Image by Allion Labs.
Technologies are driving the automotive industry forward, and the ecosystem of car Ethernet is getting more complex with various technologies like CAN, LIN, and MOST. This diversity brings great challenges to auto designers and car electronic manufacturers. Experts at Allion know what troubles developers the most when it comes to the validation of car Ethernet. We will assist you at different developmental stages and ensure your products deliver the best experiences to users.