IEC 61196-1-108:2025

Coaxial communication cables - Part 1-108: Electrical test methods - Test for phase, phase constant, phase and group delay, propagation velocity, electrical length, and mean characteristic impedance

IEC 61196-1-108:2025 applies to coaxial communications cables. It specifies test methods for determining the phase, phase constant, phase and group delay, propagation velocity, electrical length, and mean characteristic impedance of coaxial cables for use in communications systems.
A procedure to measure phase dispersion of coaxial cable is included as Annex A.
This third edition cancels and replaces the second edition published in 2011. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) Change of title, "phase and phase constant" was added.
b) Clause 6, "Preparation of test sample (TS)" was added.
c) Clause 7, "Test procedure" was added.
d) Clause 8, "Failure criterion" was added.
e) Clause 9, "Information to be given in the relevant specification" was added.

General Information

• Status: Published
• Publication Date: 08-Jan-2025
• ICS: 33.120.10 - Coaxial cables. Waveguides
• Technical Committee: SC 46A - Coaxial cables
• Drafting Committee: WG 3 - TC 46/SC 46A/WG 3
• Current Stage: PPUB - Publication issued
• Start Date: 09-Jan-2025
• Completion Date: 31-Jan-2025

Relations

• Revises: IEC 61196-1-108:2011 - Coaxial communication cables - Part 1-108: Electrical test methods - Test for characteristic impedance, phase and group delay, electrical length and propagation velocity
• Effective Date: 10-Nov-2023

Overview

IEC 61196-1-108:2025 is the 2025 third edition of an IEC standard for coaxial communication cables. It specifies electrical test methods to determine phase, phase constant, phase and group delay, propagation velocity, electrical length, and mean characteristic impedance of coaxial cables used in communications systems. Annex A provides an informative procedure to measure phase dispersion. This edition is a technical revision that replaces the 2011 edition and adds new clauses on sample preparation, test procedure, failure criteria and specification information.

Key topics and requirements

• Scope: Test methods for coaxial communication cables covering phase-related and impedance/velocity parameters.
• Parameters defined: Phase constant (β), phase and group delay, propagation velocity, electrical length and mean characteristic impedance - with relationships and formulas provided for conversions between them.
• Test equipment: Requires a capacitance meter/bridge (per IEC 61196-1-103) and a vector network analyser (VNA) capable of S21 and expanded phase measurements.
• Sample preparation: Two methods:
  • Method 1 (long cables): single sufficiently long cable assembly with connectors.
  • Method 2 (short cables): two assemblies of different lengths (typically one double the other) from the same product - or produce the short sample from the long one after testing.
• Test procedure: VNA-based expanded-phase measurements, calibration procedures and calculation methods for deriving phase constant, phase delay, group delay, propagation velocity, electrical length and characteristic impedance.
• Annex A: Measurement and interpretation of phase dispersion for cables with higher dispersive behavior.
• Quality controls: Clause on failure criterion and clause listing required information to be included in relevant product specifications and test reports.

Applications and users

This standard is practical for:

• Cable manufacturers validating product electrical performance and producing standardized test reports.
• Independent test laboratories performing compliance testing and acceptance checks.
• RF and telecom system integrators assessing cable suitability for high-frequency links (broadcast, mobile backhaul, microwave, satellite and RF test setups).
• Design engineers needing reliable data on delay, velocity and characteristic impedance for system timing, phase-matching and impedance-matching tasks.

Related standards

• IEC 61196-1:2005 - generic specification, definitions and requirements for coaxial communication cables.
• IEC 61196-1-103 - capacitance test methods referenced for sample preparation and impedance calculations.

Keywords: IEC 61196-1-108:2025, coaxial communication cables, phase constant, group delay, propagation velocity, electrical length, characteristic impedance, phase dispersion, VNA, cable testing.

Standards Content (Sample)

IEC 61196-1-108 ®
Edition 3.0 2025-01
INTERNATIONAL
STANDARD
colour
inside
Coaxial communication cables –
Part 1-108: Electrical test methods – Test for phase, phase constant, phase and
group delay, propagation velocity, electrical length, and mean characteristic
impedance
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IEC 61196-1-108 ®
Edition 3.0 2025-01
INTERNATIONAL
STANDARD
colour
inside
Coaxial communication cables –

Part 1-108: Electrical test methods – Test for phase, phase constant, phase and

group delay, propagation velocity, electrical length, and mean characteristic

impedance
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.120.10  ISBN 978-2-8327-0135-5

– 2 – IEC 61196-1-108:2025 © IEC 2025
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Parameters . 5
5 Test equipment . 7
6 Preparation of test sample (TS) . 7
6.1 General . 7
6.2 Method 1 – Long cables . 7
6.3 Method 2 – Short cables . 8
7 Test procedure . 8
7.1 Phase . 8
7.1.1 Method 1 – Long cables . 8
7.1.2 Method 2 – Short cables . 9
7.2 Phase constant . 9
7.3 Phase delay . 10
7.4 Propagation velocity . 10
7.5 Electrical length . 11
7.6 Group delay . 11
7.6.1 Method 1 – long cables . 11
7.6.2 Method 2 – Short cables . 12
7.7 Mean characteristic impedance . 12
8 Failure criterion . 13
9 Information to be given in the relevant specification . 13
10 Test report . 13
Annex A (informative) Phase dispersion measurement of coaxial cables . 14
A.1 Physical background of phase dispersion of coaxial cables . 14
A.2 Measurement of phase dispersion . 16
A.3 Example of 1/2" cable with deeply corrugated outer conductor and smooth
inner conductor wire . 17
Bibliography . 18

Figure 1 – Preparation of long cable . 7
Figure 2 – Preparation of short cables . 8
Figure A.1 – Phase dispersion of 1/2" cable with deeply corrugated outer conductor . 17

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
COAXIAL COMMUNICATION CABLES –

Part 1-108: Electrical test methods – Test for phase, phase constant,
phase and group delay, propagation velocity, electrical length,
and mean characteristic impedance

FOREWORD
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IEC 61196-1-108 has been prepared by subcommittee 46A: Coaxial cables, of IEC technical
committee 46: Cables, wires, waveguides, RF connectors, RF and microwave passive
components and accessories. It is an International Standard.
This third edition cancels and replaces the second edition published in 2011. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Change of title, "phase and phase constant" was added.
b) Clause 6, "Preparation of test sample (TS)" was added.

– 4 – IEC 61196-1-108:2025 © IEC 2025
c) Clause 7, "Test procedure" was added.
d) Clause 8, "Failure criterion" was added.
e) Clause 9, "Information to be given in the relevant specification" was added.
The text of this International Standard is based on the following documents:
Draft Report on voting
46A/1705/FDIS 46A/1717/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
This document is to be read in conjunction with IEC 61196-1:2005.
A list of all the parts in the IEC 61196 series, published under the general title Coaxial
communication cables, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
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COAXIAL COMMUNICATION CABLES –

Part 1-108: Electrical test methods – Test for phase, phase constant,
phase and group delay, propagation velocity, electrical length,
and mean characteristic impedance

1 Scope
This part of IEC 61196 applies to coaxial communications cables. It specifies test methods for
determining the phase, phase constant, phase and group delay, propagation velocity, electrical
length, and mean characteristic impedance of coaxial cables for use in communications systems.
A procedure to measure phase dispersion of coaxial cable is included as Annex A.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 61196-1:2005, Coaxial communication cables – Part 1: Generic specification – General,
definitions and requirements
IEC 61196-1-103, Coaxial communication cables – Part 1-103: Electrical test methods – Test
for capacitance of cable
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61196-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
4 Parameters
From the phase constant β of a cable, one can derive several parameters:
phase constant
πΦ
β × (1)
180° l
=
– 6 – IEC 61196-1-108:2025 © IEC 2025
group delay
dββ∆
τ ≈
(2)
g
dωω∆
phase delay
β
τ =
(3)
p
ω
propagation velocity
1 ω
v
(4)
τ β
p
relative propagation velocity
v 1 ω
v
(5)
r
c τ ××c βc
p
electrical length
l βc×
ll= =×τ×cl=×
(6)
e p
v ω
r
mean characteristic impedance
τ
β
p
Z (7)
c
ωC× C
where
β is the phase constant in radian/m;
Փ is the expanded phase in °;
l is the length of a cable in m;
Ω = 2πf is the angular frequency in radian/s;
τ is the group delay in s/m;
g
τ is the phase delay in s/m;
p
v is the propagation velocity in m/s;
==
= = =
==
=
v is the relative propagation velocity;
r
c is the propagation velocity in free space (3 × 10 m/s);
l is the electrical length in m;
e
Z is the characteristic impedance in Ω;
c
C is the capacitance in F/m.
Delay and vel
...