Introduction:

This paper mainly introduces the definition of CDN coupling decoupling network test equipment source, the main application is to test the CS conducted immunity, now there are many EMC standards proposed to use CDN to test CS, now we mainly on the IEC61000-4-6 definition of the CDN classification, the schematic diagram to expand the introduction. CDN test method is the international standard IEC61000-4-6 and GB/T 17262.6 proposed one of the test methods in the conducted immunity test system, the test purpose is to use high-frequency RF signal injected into the power line of the EUT and then observe the EUT test method. The CDN test method is one of the test methods in the conducted immunity test system proposed by the international standard IEC61000-4-6 and GB/T 17262.6. The test purpose of this method is to use high-frequency RF signals to inject into the power line of the EUT under test, and then observe whether the EUT's working status is affected.

Relevant EMC test standards:

  • There are a number of standards that can be tested using CDNs, including basic IEC standards, as well as industry-specific product standards.
  • Base standards include: IEC61000-4-6 / GB/T17626.6 / IEC61000-4-16;
  • In addition, many product and industry standards also mention the need to test conducted immunity, but they will refer to the above basic standard test methods to test, so as long as the purchase of coupling decoupling network in line with the requirements of the IEC61000-4-6 standard, the test laboratory can be in accordance with the standard requirements to test the conducted immunity of electronic products in many industries.

IEC61000-4-6 / GBT17626.6 requires conducted immunity testing of test equipment in the range of 150kHz to 80MHz, with a test frequency up to 230MHz.CDN can be used for conducted testing of the following electronic products, the test range includes power cables - unshielded balanced cables - audio cables - shielded cables - coaxial cables coupling and decoupling network of the electronics products. The CDN can be used for the following electronic products, the test scope includes electronic products power line - unshielded balanced line - audio line - shielded line - coaxial line coupling decoupling network;

Classification of CDNs according to IEC 61000-4-6:

CDNs are generally categorized into the following categories as required by the standards.

  • CDN M Sequence: Suitable for conducted immunity testing of products in DC, single-phase (2-wire/3-wire), and three-phase (4-wire/5-wire).
  • CDN S Sequence: Suitable for conducted immunity testing of coaxial cables, cables for LAN, USB interfaces and cables for audio systems.
  • CDN T Sequence: For conducted immunity testing of ISDN lines, telephone lines, CAT5 and other cables.
  • CDN AF Sequence: suitable for use when none of the above sequences can be tested.

Classification of CDNs according to IEC 61000-4-16:

IEC 61000-4-16 defines conducted immunity tests at DC - 150 kHz. The standard mentions and specifies that EMC testers need to use a coupling decoupling network as shown below and described below:

  • Power supply and input-output coupling network: use capacitor C = 1.0 μF, resistor R = 100 × nΩ, n is the number of wires
  • Coupling network for communication ports (T-type): use capacitor C = 4.7 μF and resistor R = 200 Ω
  • Typical utilization of coupled decoupling networks for CDNs is usually from 9 kHz - 150 kHz.
  • Decoupling Devices: Provide common mode attenuation in the 0-150kHz range, transformers and converters can be used.
  • Input-to-output and input/output-to-ground insulation withstand: 1kV, 50/60Hz, 60s
  • Common mode decoupling attenuation in the frequency range of 15Hz-150kHz: ≥60dB

EUTTEST provides standardized CDN conducted immunity test system, the following test configuration diagram will explain how to use CDN to build EMC-CS test system.

start testing

Diagram of the calibration configuration for the CDN test method:

The CDN method needs to be calibrated before testing can begin, and EUTTEST provides the following list of test equipment that needs to be used for test channel calibration:

After contacting EUTTEST to purchase the above equipment, connect the NSG4070 output to the input port of the CDN according to the following diagram, and record the displayed value of the NSG4070 to confirm the forward power output level Vout.

Calibrate CDN input level Vout using NSG4070

Calibrate CDN input level Vout using NSG4070

Repeat each test frequency from 150 kHz to 230 MHz as required by IEC 61000-4-6 and record the Vout value at each frequency.

Test configuration diagram for the CDN test method:

The equipment used for CDN test method testing is the same as for calibration, and there is no need to purchase additional equipment.

After completing the above calibration process, we get the output level Vout of the NSG4070, now use the configuration in the figure below to connect the DUT and the AE auxiliary equipment, and inject the Vout at different frequency points inside the CDN, at this point, we need to observe and record the EUT's operating status, and then record each Vout value and the EUT's operating status in the test report.

Test EUT using NSG4070 calibration result Vout

Test EUT using NSG4070 calibration result Vout

Test Summary:

Note: Coupled decoupled network CDNs haveCDN-M,CSN-S,CDN-T,CDN-AF Please select the correct CDN based on the test examples listed in the table below and the type of cable under test.

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Different types of CDNs

Different types of CDNs

The above is the IEC61000-4-6 conducted immunity test system CDN test method provided by EUTTEST, EMC testers only need to follow the above configuration to complete the standard requirements of RF field induction conducted immunity test needs, if you have any questions about the above test program, please contact EUTEST to purchase the above equipment and build the test system according to the above section after Contact our after-sales personnel for advice.