IEC 61196-1-112:2025

IEC 61196-1-112 ®
Edition 2.0 2025-01
INTERNATIONAL
STANDARD
colour
inside
Coaxial communication cables –
Part 1-112: Electrical test methods – Test for return loss and voltage standing
wave ratio
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IEC 61196-1-112 ®
Edition 2.0 2025-01
INTERNATIONAL
STANDARD
colour
inside
Coaxial communication cables –

Part 1-112: Electrical test methods – Test for return loss and voltage standing

wave ratio
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.120.10  ISBN 978-2-8327-0125-6

– 2 – IEC 61196-1-112:2025 © IEC 2025
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 6
5 Test equipment . 7
6 Preparation of test sample (TS) . 7
7 Number of measuring points . 8
8 Test procedure . 9
8.1 General . 9
8.2 Two-port measurement . 10
8.3 One-port measurement . 10
9 Failure criterion . 10
10 Information to be given in the relevant specification . 11
11 Test report . 11
Annex A (informative) Requirement on the frequency spacing for the measurement of
return loss (RL) of RF cables . 12
A.1 General . 12
A.2 Physical basics . 13
A.2.1 General . 13
A.2.2 Return-loss model . 13
A.3 Comparison between the theoretical and practical results . 19
Annex B (informative) An example of dividing a specified frequency range to be
measured into several frequency subintervals to measure return loss (RL) or voltage
standing wave ratio (VSWR) of RF cables . 21
Bibliography . 22

Figure 1 – S-parameter representing transmission and reflection characteristics . 6
Figure 2 – preparation of the test sample . 7
Figure A.1 – Reflection model . 13
Figure A.2 – Resonance peak . 18
Figure A.3 – Comparison of theoretical and measured 3 dB bandwidths of resonance
peaks . 19

Table B.1 – An example of dividing a specified frequency range to be measured into
several frequency subintervals to measure return loss (RL) or voltage standing wave
ratio (VSWR) of for 50-141 type semi-flexible cables . 21

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
COAXIAL COMMUNICATION CABLES –

Part 1-112: Electrical test methods –
Test for return loss and voltage standing wave ratio

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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IEC 61196-1-112 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 second edition cancels and replaces the first edition published in 2006. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) added "voltage standing wave ratio" in the title;
b) added 3.1 voltage standing wave ratio (VSWR) and 3.2 return loss (RL);
c) revised Clause 4 "Principle";

– 4 – IEC 61196-1-112:2025 © IEC 2025
d) added Figure 1 and Figure 2;
e) revised Clause 7 "Number of measuring points";
f) added Clause 8 "Test procedure";
g) added Clause 10 "Information to be given in the relevant specification";
h) added Annex B.
The text of this International Standard is based on the following documents:
Draft Report on voting
46A/1704/FDIS 46A/1715/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 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.
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of its contents. Users should therefore print this document using a colour printer.

COAXIAL COMMUNICATION CABLES –

Part 1-112: Electrical test methods –
Test for return loss and voltage standing wave ratio

1 Scope
This part of IEC 61196 applies to coaxial communications cables. It specifies test methods for
determining return loss (RL) and voltage standing wave ratio (VSWR) of coaxial cables for use
in communications systems.
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61196-1 and the
following 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
3.1
voltage standing wave ratio
VSWR
ratio, along a transmission line, of a maximum of the voltage to an adjacent minimum magnitude
of the voltage of a standing wave, expressed as the following:
V VV+
max ir
VSWR
(1)
V VV−
min i r
where
VSWR is the voltage standing wave ratio;
V is the maximum magnitude of the voltage;
max
V is the minimum magnitude of the voltage;
min
V is the voltage of incident wave;
i
V is the voltage of reflected wave.
r
==
– 6 – IEC 61196-1-112:2025 © IEC 2025
3.2
return loss
RL
ratio of the power of the reflected wave to the power of the incident wave at a specified port or
transverse cross-section of a transmission line, expressed as follows:
P ZZ− VSWR−1
r TR
RL=−=10log −20log =−20log (2)
10 10 10
P Z ++Z VSWR 1
i T R
where
RL is the return loss;
P is the power of incident wave;
i
P is the power of reflected wave;
r
Z is the measured complex impedance, in ohms (Ω), obtained from terminated cable
t
;
measurements where the distant end is terminated in Z
R
Z is the reference impedance of a transmission line, in ohms (Ω), (50 Ω, 75 Ω, or as
R
appropriate);
VSWR is the voltage standing wave ratio.
4 Principle
At lower frequencies, physical length of the test sample is less than λ/10, where λ is the
wavelength, and the test values of the voltage/current on the test sample are independent of
the test position. At higher frequencies, physical length of the test sample is bigger than λ/10,
and the characteristic impedance reflects its transmission characteristics. The voltage/current
on the test sample differs at different positions.
It is assuming that the shielding effect of the test sample is good enough with no interference
from outside and no signal leaking out. The input signal a of the test sample will transmit one
part of signal b to the load and also a portion of the signal b ; a is reflected back at both the
2 1 2
input port 1 and the output load port 2 respectively, as shown in Figure 1.
The signal transmission and reflection characteristics in test sample can be represented by the
S-parameter in Figure 1.
Figure 1 – S-parameter representing transmission and reflection characteristics

The definition of S-parameter is based on the signal voltages which are vectors, where:
b aS+ a S
(3)
1 1 11 2 12
b aS+ a S
(4)
2 1 21 2 22
When the end of test sample is terminated on a precision load, a = 0 and the input reflection
coefficient can be calculated as Formula (5):
b
S =
(5)
a
5 Test equipment
A vector network analyser (VNA) capable of performing S /S measurements and a calibration
11 22
kit with calibration standards (open, short, load).
6 Preparation of test sample (TS)
Test sample to allow direct connection to either the VNA or terminating load, or both. A cable
is connected to a pair of precision test connectors with small inherent reflections to form a cable
assembly as a test sample (TS) as shown in Figure 2.

Figure 2 – preparation of the test sample
The change in return loss for small frequency deviations from the resonance frequency of
reflection peaks does not depend on the cable length. However, the maximum value of the peak
is length-dependent. With decreasing test length, the return loss increases. The change is
described by ∆a as shown in Formula (6). Therefore, the length of the TS shall be stated in
r,L
the test report.
−2αL
1
1− e
a aL aL 20log
∆= ( )− ( ) 
(6)
r,L r 2 r 1 10
−2αL
1− e

where
L is the length of the test sample, in m;
∆a is the return loss for the test sample with length L;
r,L
α is the cable attenuation at the measured frequency, in Np/m.
NOTE 1 Np ≈ 8,686 dB, and 1 dB ≈ 0,1151 Np.
=
=
=
– 8 – IEC 61196-1-112:2025 © IEC 2025
7 Number of measuring points
VNAs measure at discrete frequency points. In order to get the correct measurement for
narrowband peaks in the return loss, the frequency spacing between two neighbouring
measurement frequencies shall not be too large.
The bandwidth of reflection peaks is dependent on the cable attenuation. The higher the
attenuation, the larger the bandwidth, and consequently the larger could be the frequency
spacing between two measurement points. The cable attenuation for RF cables is frequency-
dependent and increases with frequency. Thus, finally, the maximum permitted frequency
spacing between two measuring points increases with the measurement frequency [1] [2].
The frequency spacing ∆f between any two measuring points shall be:
∆α
r,f
300× v
r (7)
∆f≤ 1,4× ×αf × 10 −1
( )
868,6×π
where
∆f is the maximum permitted frequency spacing between two measurement points, in
MHz;
α(f) is the cable attenuation at the measured frequency, in dB/100 m;
v is the relative velocity of the cable;
r
∆a is the maximum permitted error which can be caused by the frequency spacing, in dB;
r,f
1,4 is the factor which takes into account the difference between theoretical and practical
investigations [3].
If not specified otherwise, the maximum permitted error caused by the frequency spacing shall
be ∆a ≤ 1 dB.
r,f
NOTE For the requirement on the frequency spacing for the measurement of return loss (RL) of RF cables, see
Annex A.
The number of measuring points shall meet the requirements of Formula (8).
ff−
max min
n≥+1
(8)
∆f
where
n is the number of measuring frequency points;
f is the highest frequency to be measured, in MHz;
max
f is the lowest frequency to be meas
...