CDNs - Coupling Decoupling Networks

A Coupling Decoupling Network (CDN) is a specialised device used in conducted immunity testing to inject RF interference directly into a product’s cables while simultaneously protecting the auxiliary equipment (like power supplies or signal generators) from that same interference. It ensures that the test signal goes exactly where it is intended—into the Device Under Test (DUT).

Why Choose a CDN?

Standardized Impedance: CDNs provide the precise $150 Omega$ common-mode impedance required by international standards (such as IEC 61000-4-6), ensuring that test results are repeatable and legally valid.

Effective Isolation: The "Decoupling" part of the network prevents the high-power RF test signal from traveling back into the local power grid or damaging sensitive laboratory equipment.

High Measurement Accuracy: Because the CDN defines the circuit parameters, it eliminates the unpredictable variables of the laboratory's own wiring, leading to much more stable and accurate "pass/fail" data.

Versatile Connectivity: They are available in specific configurations for almost any type of cable, including 3-phase power, unscreened twisted pairs (UTP), and even high-speed Ethernet or USB lines.

Core Applications

IEC 61000-4-6 Compliance Testing: This is the primary tool for testing a product's "Immunity to Conducted Disturbances," simulating the RF interference that might be picked up by long cables in an industrial environment.

Power Line Immunity: Injecting noise into AC or DC power input ports to ensure that voltage fluctuations or high-frequency spikes don't cause the device to crash or reset.

Signal and Data Line Testing: Verifying that communication over data cables (like RS-232 or LAN) remains error-free even when subjected to intense electromagnetic fields.

Automotive Electronics Testing: Used to simulate the harsh electrical environment of a vehicle, where the ignition system and motors create constant conducted "hash" on the wiring harness.

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