Car Ethernet – An introduction to TC9

Allion Labs / Maroco Fan & Ken Yan

Data transmissions, video streaming, drivers, and passengers can now enjoy these in-premise entertainment activities right in their cars, all possible because of the advancing 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 radiofrequency 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 Interferences 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 interferences 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 interferences and distort measurement accuracy. It is important to use platforms or conductive drums to hold the DUTs while testing.

The key to choosing Test Tools & Fixtures for TC9 tests

1. Measurement Fixtures
Fixture Requirements: low insertion loss rate, the symmetry of differential signal, and high impedance

2.  Impedance and Termination
The impedance requirements are higher than commercial products:

Impedance	Tolerance	Condition
100 Ω	±5%	50 ps
	±10%	5 % limit is exceeded no longer than 120 ps round trip time

3. Balance

Fixtures measurements require the differential trace to be less than< 30mm, the test parameter of symmetry of differential signal is determined as LCL (Sdc11)

4. Conductive Drum

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.

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.

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