GB/T 31723.413-2021

Metallic communication cable test methods—Part 4-13: Electromagnetic compatibility (EMC)—Coupling attenuation of links and channels(laboratory conditions)—Absorbing clamp method (English Version)

Standard No.

GB/T 31723.413-2021

Language

Chinese, Available in English version

Release Date

2021

Published By

General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China

Latest

GB/T 31723.413-2021

Scope

This part of GB/T 31723 describes laboratory test methods for coupling attenuation of links and channels used in analog and digital communication systems.

Introduction

Interpretation of the core content of the standard

This standard is equivalent to IEC 62153-4-13:2009, which specifies the laboratory method for measuring the coupling attenuation of metal communication links and channels by the absorption clamp method in the frequency range of 30MHz~1GHz. It focuses on solving the surface wave interference problem in electromagnetic compatibility (EMC) testing.

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Key Technical Requirements

Test Elements	Technical Requirements	Allowable Deviation
Balanced-Unbalanced Converter	Output Balance ≥50dB(30-100MHz)	±3dB
Extended Cable Length	Near End 100cm/Total Length 10m	±10cm/±0.5m
Effective Test Length	600cm	±10cm
Measurement Sensitivity	Better than the measured value by 6dB	—

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Key components of the test device

Core equipment includes:

• Absorption clamp: impedance Z3, 50±10mm from the connector surface
• Balanced-unbalanced converter: working attenuation ≤10dB
• Ferrite absorber: insertion loss>10dB
• Extension cable: insertion loss<2dB@highest frequency

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Sample preparation specifications

Symmetrical link termination example: For a 100Ω cable, R1=50Ω, R2=0Ω, the common mode impedance is 25Ω. Shielded cables need to connect the center line to the shield layer, and the terminal resistor should be shielded.

Multi-conductor/coaxial link: It is still under research, and the standard has not yet given a specific test plan.

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Key points of measurement procedure

1. Prioritize the cable section with connector
2. The position of the absorbing clamp should be ≥50mm from the connector surface
3. The link defined by ISO/IEC 11801 needs to be measured in three stages:
   a) Measurement on the wall socket side
   b) Measurement on the collection point
   c) Measurement on the cross connection side

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Result evaluation method

Boundary curve method is used for symmetrical link:
30-100MHz: A=A_result
100-1000MHz: A=A_result-20×log₁₀(f/100)

Typical value range:
? Shielded channel: ≥57dB
? Unshielded channel: ≥43dB

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Recommendations for standard implementation

1. Equipment selection: Coaxial cable assemblies that comply with IEC 61196-1 are preferred

2. Environmental control: Ensure that there are no metal interferences within 60cm of the test area

3. Method verification: Before formal testing, a verification cable must be used to confirm the sensitivity of the device

4. Data recording: The frequency point and attenuation corresponding to the worst valley value must be recorded

GB/T 31723.413-2021 Referenced Document

• GB/T 31723.405-2015 Metallic communication cable test methods.Part 4-5:Electromagnetic compatibility (EMC).Coupling or screening attenuation.Absorbing clamp method
• IEC 61196-1 Coaxial communication cables - Part 1: Generic specification - General, definitions and requirements
• ISO/IEC 11801 Corrigendum 3 - Information technology - Generic cabling for customer premises*， 2025-04-21 Update

GB/T 31723.413-2021 history

• 2021 GB/T 31723.413-2021 Metallic communication cable test methods—Part 4-13: Electromagnetic compatibility (EMC)—Coupling attenuation of links and channels(laboratory conditions)—Absorbing clamp method

GB/T 31723.413-2021 -All Parts