Overview
IEC 61196-1-108:2011 specifies electrical test methods for coaxial communication cables used in telecommunications networks. The standard defines procedures to measure and calculate key transmission parameters including characteristic impedance, phase and group delay, electrical length, and propagation velocity. Edition 2 (2011) updates the 2005 edition by incorporating Annex A as a normative description of phase dispersion measurement.
Keywords: IEC 61196-1-108, coaxial communication cables, characteristic impedance, phase delay, group delay, propagation velocity, electrical length, phase dispersion, VNA.
Key topics and technical requirements
- Scope: Test methods for coaxial cables intended for telecom networks; applies alongside IEC 61196-1 (generic specification).
- Measured parameters: Phase constant (β), phase delay (τp), group delay (τg), propagation velocity and relative velocity, electrical length, and mean characteristic impedance.
- Measurement equipment:
- Vector Network Analyzer (VNA) for S-parameter and phase measurements.
- Capacitance meter/bridge in accordance with IEC 61196-1-103.
- Procedure essentials:
- Acquire S21 or S12 phase data and convert ("unwrap") the VNA phase (normally limited to –π to +π) to a monotonic phase function to compute β.
- Ensure sufficient frequency point density to detect all phase turns.
- Observe sample-length constraints to avoid hidden phase ambiguity at low frequency.
- Record ambient temperature and test conditions.
- Data processing: Formulas in the standard derive delay, velocity and impedance from β and capacitance; group delay typically requires differential evaluation across frequency points.
- Annex A (normative): Detailed background and method for measuring phase dispersion, useful for lossy or highly dispersive cables.
Applications and practical value
- Quality control and acceptance testing for coaxial cable manufacturing.
- Performance verification for cables used in RF, broadcast, mobile backhaul, and other telecommunications links.
- Design validation and R&D for cable materials and geometries (e.g., corrugated outer conductors that affect dispersion).
- Troubleshooting and characterization in test laboratories using VNAs and precision capacitance measurement.
Who should use this standard
- Cable manufacturers and suppliers
- Accredited test laboratories and QA/QC engineers
- Telecom operators and system integrators validating cable performance
- R&D engineers developing RF/coaxial cable products
Related standards
- IEC 61196-1: Generic specification for coaxial communication cables
- IEC 61196-1-103: Electrical test methods - Test for capacitance of cable
This standard provides reproducible, internationally harmonized test procedures to ensure accurate measurement of coaxial cable transmission properties critical for reliable telecommunications systems.
Open preview (PDF)Coaxial communication cables - Part 1-108: Electrical test methods - Test for characteristic impedance, phase and group delay, electrical length and propagation velocity
