Noise suppression technologies/case study introduction (Automotive)

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles(Signal lines)

There are many kinds of problematic noise that are emitted from the devices installed in vehicles.
The examples of the actions taken to suppress noise described here deal with the noise that is radiated from the USB signal cables.

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles

※The EUT here is not a product intended to be installed in a vehicle, but as the noise conditions are similar, a device for general applications is used instead.
※The tests have been carried out in both the USB 2.0 and USB 3.0 modes.
EUT:Equipment Under Test

Details of noise suppression measures taken in USB 2.0 mode

When interfaces compliant with the USB 3.0 standard are to be operated as equivalent to the USB 2.0 standard, signal lines used for USB 2.0 are used. As USB 2.0 signal lines have both transmission (TX) and reception (RX) functions, common mode choke coils are inserted into these lines.

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles

Common mode choke coil in TX/RX line
DLM11SN900HZ2
or
DLW21SZ900HQ2
inserted

Click here for details of the measurement conditions.

Noise measurement results (for measures to suppress noise in USB 2.0 signal lines)

DLM11SN900HZ2 used

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles

By adding a common mode choke coil (DLM11SN900HZ2), the noise was successfully reduced(maximum reduction of approx. 37 dB at a vertically polarized wave frequency of 240 MHz).

DLW21SZ900HQ2 used

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles

By adding a common mode choke coil (DLW21SZ900HQ2), the noise was successfully reduced(maximum reduction of approx. 37 dB at a vertically polarized wave frequency of 240 MHz).

Verification of SI compatibility when filters are inserted

USB2.0 Eye Diagram near

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
short
Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
DLM11SN900HZ2
Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
DLW21SZ900HQ2

USB2.0 Eye Diagram far

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
short
Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
DLM11SN900HZ2
Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
DLW21SZ900HQ2

Details of noise suppression measures taken in USB 3.0 mode

In the USB 3.0 SuperSpeed mode, separate signal lines are used for TX and RX, unlike in the 2.0 mode.

Here, a common mode choke coil is inserted into the TX signal line.

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles

Common mode choke coil in TX signal line
DLM11SN900HZ2
or
DLW21SZ900HQ2
inserted

Click here for details of the measurement conditions.

Noise measurement results (for measures to suppress noise in USB 3.0 signal lines)

DLM11SN900HZ2 used

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles

By adding a common mode choke coil (DLM11SN900HZ2), the noise was successfully reduced.

DLW21SZ900HQ2 used

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles

By adding a common mode choke coil (DLW21SZ900HQ2), the noise was successfully reduced.

Verification of SI compatibility when filters are inserted

USB3.0 Non-Transition Eye Diagram

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
short
Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
DLM11SN900HZ2
Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
DLW21SZ900HQ2

USB3.0 Transition Eye Diagram

Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
short
Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
DLM11SN900HZ2
Examples of actions taken to comply with the CISPR25 standard governing radio emissions (noise emitted) from devices mounted in vehicles
DLW21SZ900HQ2

Summary of signal line noise suppression measures

Communication in the USB 2.0 and USB 3.0 modes was initiated between a PC and hard drive and, in an environment complying with the CISPR25 standard, the noise radiated from the USB cables was evaluated.

As a result, it was found under the condition of using no filters that noise was radiated from the USB cables during both USB 2.0 and USB 3.0 communication.
A high level of harmonic noise—approx. 57 dB (µV/m)—was found at a vertically polarized wave frequency of 240 MHz during USB 2.0 communication.

As a measure taken to suppress the noise, the following components were added to the signal lines:

DLM11SN900HZ2

DLW21SZ900HQ2

In this way, it was verified that the noise in both the USB 2.0 and USB 3.0 modes was successfully reduced.
In the USB 2.0 mode, the noise was successfully reduced by a maximum of approx. 37 dB (at a vertically polarized wave frequency of 240 MHz).

Selection chart for common mode choke coils

Selection chart for signal lines

For non automotive grade

For automotive grade

 

Selection chart for power lines

For non automotive grade

For automotive grade

 

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