Overview
IEC 61196-1-125:2022 defines an electrical test method to determine the equivalent relative permittivity (εe) and equivalent dissipation factor (tanδe) of the dielectric in finished coaxial communication cables. The standard is intended to provide reliable dielectric properties for real cable assemblies rather than for isolated materials, enabling accurate prediction of propagation velocity and dielectric losses in practical RF and microwave applications.
Key topics and requirements
- Scope: Measurement of equivalent relative permittivity and equivalent dissipation factor of dielectric for finished coaxial cables.
- Specimen preparation: Cables must be assembled with connectors providing uniform characteristic impedance. For ultra-low-loss cables the round‑trip loss should be > 40 dB; if lower, connector insertion loss must be compensated (per IEC 61169-1-2).
- Equipment: A calibrated Vector Network Analyzer (VNA) and appropriate mechanical or electronic calibration kits covering the test frequency range.
- Calibration: Calibrate test setup attenuation and phase over the whole frequency range. The phase delay measurement resolution must meet the minimum-point requirement based on frequency and cable length.
- Measurements:
- Measure phase constant (β(f)) to compute phase delay τ(f) and propagation velocity v(f) → used to derive equivalent relative permittivity εe.
- Measure attenuation constant α(f) to evaluate losses → used to derive equivalent dissipation factor tanδe.
- Data processing: Attenuation is form‑fitted to separate conductor and dielectric loss components (coefficients A, B, C, D); dielectric loss coefficient B and εe are used to compute tanδe (standard provides the relationship used to calculate tanδe).
- Test report: Required information includes sample length, test temperature and the test parameters/results.
Practical applications
- Characterising dielectric behavior of finished coaxial cables for RF design, link budgeting and simulation.
- Supporting cable quality control and production acceptance testing.
- Informing material selection and cable design decisions to optimise propagation velocity and minimize dielectric loss.
- Ensuring consistent performance in telecommunications, broadcast, satellite, aerospace and other RF-sensitive systems.
Who uses this standard
- Cable manufacturers and R&D teams
- Independent test laboratories and compliance facilities
- RF/microwave design engineers and system integrators
- Quality assurance and product certification bodies
Related standards
Keywords: IEC 61196-1-125:2022, coaxial communication cables, equivalent relative permittivity, equivalent dissipation factor, dielectric test methods, VNA, attenuation constant, phase delay.