TP5 –

High-frequency wire harness

Extension of the standard to high-frequency applications

DESIGN RULES FOR HIGH-FREQUENCY WIRE HARNESSES

Extension of the standard to high-frequency applications

In the first edition, DIN 72036 was limited to the use of low-voltage wiring harnesses with unshielded cables. However, a large number of applications are served in a vehicle, which in turn require specific components and cables.

In the context of high-frequency applications, this includes, for example, the coax cables for antennas and connections for high data rates. In the past, there was only one antenna cable for the radio antenna in a vehicle, but in today's vehicles there are additional cables for mobile communications and navigation, among other things. In addition, more and more connections are required for high data rates, for example for high-resolution camera systems in driver assistance systems.

 

Initial situation and motivation

Today's vehicles contain more and more sensors and actuators that support the driver with improved and new assistance systems through to autonomous driving. Camera systems in particular generate very large amounts of data and therefore require special connections for high data rates for data transmission to the processing system. The zone control units used in the zone architecture also require high-performance data connections between these high-performance computers.

What all these connections have in common is the requirement for high signal integrity. Therefore, these connections are always designed as shielded point-to-point connections. The cables used are either coaxial cables or differential transmission with twisted cables. What all cables have in common is screen/shielding to prevent unwanted radiation and interference. A few standards have established themselves as connectors, for example FAKRA and screwed or plugged coax connectors.

In contrast to the other wire harnesses in the vehicle, high-frequency wire harnesses are already predominantly manufactured automatically by specialized assembly companies. Therefore, the focus in this TP is initially on examining the applicability of the already established design rules to high-frequency wire harnesses. Here too, optimizing the variety of parts and processes can increase the cost-effectiveness of automated production and pave the way towards full automation.

 

Current focus of work

In the first step, all low-voltage design guidelines are reviewed and evaluated for their direct applicability to high-frequency wire harnesses. There are four different evaluations.

  • The design rule is applicable without restriction and without amendment.
  • The design rule is applicable with few changes.
  • The design rule is transferable with comprehensive revision.
  • The design rule is not relevant for high-frequency wire harnesses.

This assessment results in a worklist that will be included in one of the next updates of the standard. The design rules that require few to no changes are the easiest to implement. Here, either only the application level is added or a few changes are made to the content. Ideally, the design rule can remain valid for LV despite these few changes.

In the event of major changes, a new design rule is derived and drawn up. This requires intensive coordination within the TP as well as with other TPs, as the applicability of new design rules to low voltage and high voltage wire harnesses must be clarified.

 

Outlook

There are still many possible versions of the new Automotive Ethernet transmission protocol, not all of which have yet been equally optimized for automated production. An upcoming edition of the standard can promote this optimization for fully automated production.