IEC 61196-1-114:2025

IEC 61196-1-114 ®
Edition 2.0 2025-11
INTERNATIONAL
STANDARD
REDLINE VERSION
Coaxial communication cables -
Part 1-114: Electrical test methods - Test for inductance
ICS 33.120.10 ISBN 978-2-8327-0871-2
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CONTENTS
FOREWORD . 2
1 Scope . 1
2 Normative references . 4
3 Terms, definitions and abbreviated terms . 4
3.1 Terms and definitions relative permittivity . 4
3.2 Abbreviated terms . 5
4 Procedure . 5
4.1 Equipment . 5
4.2 Test sample . 5
4.3 Calibration . 5
4.4 Test setup . 5
4.5 Measuring procedure . 5
5 Expression of test and results . 6
6 Test report . 6
Annex A (informative) The bending effect on coaxial cable inductance. 8
A.1 Background . 8
A.2 Principle . 8
A.2.1 Circuit model for impedance of cables with the bi-conductor structure at
low frequencies . 8
A.2.2 Line current model for the approximation of partial inductance. 9
A.2.3 Deviation of the inductances between bent and straightened cables . 9
A.3 Comparison between theoretical derivation and practical tests . 14
Bibliography . 16

Figure A.1 – Circuit model for inductance measurement configuration at low
frequencies . 8
Figure A.2 – Line current model for a straightened twinaxial cable . 10
Figure A.3 – Line current model for a bent twinaxial cable . 11
Figure A.4 – The relationships between l, θ and L for a twinaxial cable . 12
m Δ
Figure A.5 – Line current model for the coaxial cable . 13
Figure A.6 – The relationships between l, θ and L for a coaxial cable . 14
m Δ
Table A.1 – Inductance of the CUT at different bending angles . 15

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Coaxial communication cables -
Part 1-114: Electrical test methods - Test for inductance

FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes made
to the previous edition IEC 61196-1-114:2015. A vertical bar appears in the margin wherever a
change has been made. Additions are in green text, deletions are in strikethrough red text.

IEC 61196-1-114 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 2015. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the term "inductance" has been revised;
b) the necessary abbreviated term is added;
c) the length and layout of the test sample have been revised;
d) the measuring procedure has been revised;
e) the additional information for the bending effect on coaxial cable inductance test is provided
in Annex A.
The text of this International Standard is based on the following documents:
Draft Report on voting
46A/1735/FDIS 46A/1737/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.
A list of all parts in the IEC 61290 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.
1 Scope
This part of IEC 61196 specifies a test method to determine the inductance characteristics of
coaxial cables used in analogue and digital communication systems cables.
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, Coaxial communication cables - Part 1: Generic specification - General,
definitions and requirements
IEC 61196-1-101, Coaxial communication cables - Part 1-101: Electrical test methods - Test for
conductor DC resistance of cable
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions relative permittivity
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
3.1.1
inductance
L
effective inductance (L) of the cable as the sum of inductances of the inner conductor, the outer
conductor and the mutual inductance between the two conductors of the cable when signal is
transferred
Note 1 to entry: At any (low) frequency, the impedance of a cable can be represented by two components –
resistance (R) and reactance (X) – or as a polar function having magnitude (Z) and phase (θ). The impedance shall
be represented by a series circuit with
, and
R= Zcosθ
( )
X= Zsinθ
( )
where
Z = ;
R + X
X
;
tan(θ) =
R
X = 2πfL.
Note 2 to entry: Inductances are normally measured at low frequencies (f) (50 Hz, 800 Hz or 1 000 Hz) as required
in the relevant cable specification. For this case, the DC resistance (R) shall be measured as described in
IEC 61196-1-101. R is the DC-resistance of the inner and outer conductor (= loop resistance).
3.2 Abbreviated terms
CUT cable under test
4 Procedure
4.1 Equipment
The measurements can be performed using an impedance analyser (or alternatively a discrete
signal generator and receiver), an LCR-meter or an impedance-measuring-bridge (Wheatstone
bridge, Maxwell bridge).
The accuracy of measuring equipment should be less than or equal to 2 %.
4.2 Test sample
The test sample shall be straightened and have a length of 10 m up to 100 m. the test may be
performed at a delivery length, if the attenuation of the cable is small enough, but less than
1/20 of the wave length of the test signal for measurement with higher frequencies.
The minimum length of the CUT should be 10 m. In case of measuring at higher frequencies,
the test may also be performed at a delivery length if it is less than 1/20 of the wavelength of
the test signal.
The layout of the CUT may be straightened or be bent. When bending is applied, the bending
radius should be greater than the minimum bending radius of the CUT while it cannot form a
closed loop. Annex A provides further information for the bending effect on coaxial cable
inductance test.
4.3 Calibration
The influence of the connecting cables, used for connection of the CUT to the equipment, shall
be measured at the relevant frequency.
The calibration of the test set-up with the impedance analyser shall be done under open, short
and load conditions. The measurements shall be done over the whole specified frequency range.
The calibration data shall be saved, so that the results may can be corrected.
4.4 Test setup
The input impedance Z of the CUT shall be measured with the impedance analyser with a short

circuit at the far end of the end of the CUT.
4.5 Measuring procedure
The test sample shall be connected to the terminals of the measuring devices and the
impedance Z shall be measured with a short circuit at the far end of the CUT.
Impedance analysers or LCR-meters will show the value of measured inductance L directly.
m
In other cases, the equation given in 3.1 can be used to calculate the inductance with other
instrumentation. In high frequency, Formula (1) can be used to obtain L by measuring the
m
dimensions of the CUT according to IEC 60811-1-1 [1] .
___________
Numbers in square brackets refer to the Bibliography.
μr
d o1
L L+ LL+ ⋅×l 1000≅ L ⋅ l×=1000 ln ⋅×l 1000
( ) (1)
m di o d
2πr
i
where
L is the measured inductance, expressed in mH;
m
l is the length of the sample, expressed in m;
L is the per-unit-length inductance of which the magnetic field energy is stored in the
d
dielectric, expressed in H/m;
L is the per-unit-length inductance of which the magnetic field energy is stored in the
i
inner conductor, expressed in H/m;
L is the per-unit-length inductance of which the magnetic field energy is stored in the
o
outer conductor, expressed in H/m;
μ is the absolute permeability of the dielectric, for non-ferromagnetic material; it equals
d
−7
4π 10 H/m;
r is the inner radius of the outer conductor, expressed in mm;
o1
r is the radius of the inner conductor, expressed in mm.
i
5 Expression of test and results
The test results shall be normalized to the reference length of 1 km.
L = (L /Length) × 1 000 (mH/km)
m
where
L is the inductance of the reference length;
L is the measured inductance in millihenrys;
m
Length is the length of sample in metres.
L
m
L ×1000
(2)

l

where
L is the inductance of the reference length, expressed in mH/km;
l is the length of the sample.
6 Test report
The test report shall give the following test conditions and record the corrected values for the
reference length:
– temperature;
– test frequency;
– sample length;
=
=
– normalized values for the reference length;
– type equipment used.
Annex A
(informative)
The bending effect on coaxial cable inductance
A.1 Background
Cable bending has been considered influential in measurement of the inductance, and cables
are therefore required to be straightened for accurate measurement results of the inductance.
However, in respect to cables with the length over 10 m, it is often inconvenient to measure
their inductance in straightened layouts due to the space constraint of a laboratory. Thus, it is
necessary to figure the precise deviation of inductance between a bent cable (non coiled) and
a straightened one, allowing for possible corrections of the inductance results obtained by a
bending layout.
Annex A investigates the bending effect on the inductance of twinaxial and coaxial cables with
the line current model, indicating that the bending effect on inductance of relatively long cables
at low frequency is neglectable.
Further information about analysis of multiconductor transmission lines and circuit oriented
electromagnetic modelling can be found in [2] and [3].
A.2 Principle
A.2.1 Circuit model for impedance of cables with the bi-conductor structure at low
frequencies
At low frequencies, i.e., the capacitance between cable conductors is neglectable, the circuit
model for a cable with the bi-conductor structure in the inductance measurement configuration
is shown in Figure A.1, where one end of the cable is connected to the LCR-meter and the other
is short. R and R are the resistances of the two conductors; L and L are the partial self-
1 2 1 2
inductances of the conductors; M is the mutual inductance between the conductors.
Key
L partial self-inductance
L partial self-inductance
M mutual inductance between the conductors
resistance of one conductor
R
R resistance of one conductor
Figure A.1 – Circuit model for inductance measurement
configuration at low frequencies
The inductance L can be expressed as in Formula (A.1):

LL= +−L 2M
(A.1)
1 2 12
If each conductor has a uniform cross-section and no ambient permeability magnetic material
exists, those partial inductances can be calculated by the integrals of Formula (A.2):

μ tt⋅
0 mn
L = dAAd ddl l
mn n m n m
∫∫∫∫ (A.2)
4πS S r
m n mn
l lA A
mn m n
where
L is the partial inductance, expressed in H;
mn
−7
μ is the absolute permeability of vacuum, and equals 4π 10 H/m in SI;
S , S are the areas of the conductor cross-sections, expressed in m ;
m n
l , l are the one-dimensional integration regions along the axes, expressed in m;
m n
A , A are the two-dimensional integration regions in the cross-sections, expressed in
m n
m ;
t , t are the unit tangent vectors of l and l , no unit;
m n m n
r is the distance between the integration cells in the two regions, expressed in m.
mn
NOTE 1 m and n are the integration region indices, and both belong to {1, 2}.
NOTE 2 L = L , L = L , and L = L = M
11 1 22 2 12 21 12.
A.2.2 Line current model for the approximation of partial inductance
The six-fold integral in Formula (A.2) is sophisticated and extremely hard for analytical solution.
Hence, it is approximated that the integral kernel keeps constant in the integration cross-
sections, which in fact ignores the cross-section shapes and converts the two conductors into
line current models. Then, the simplified integral reads as in Formula (A.3):

μ tt⋅
0 mn
L = ddll
mn n m
∫∫ (A.3)
4π r
mn
ll
mn
The calculation complexity of the partial inductances is reduced drastically from six-fold
integrals to double integrals. In fact, though the application of Formula (A.3) to the calculation
of self-inductances (m = n) leads to divergent results, the deviation of the inductances between
bent and straightened cables can be obtained.
A.2.3 Deviation of the inductances between bent and straightened cables
A.2.3.1 General
A.2.3 solves partial inductances and the total inductance deviation using Formula (A.3). A
simple twinaxial cable case is first considered, and the results are applied to coaxial cable.
A.2.3.2 Twinaxial cable inductance deviation
In respect to a straightened twinaxial cable in the length of l, the line current model in Figure A.2
can be used to calculate partial inductances, as in Formula (A.4) and Formula (A.5).
xl x l
μ 1
L L dx dx
11 22 2 1 (A.4)
∫ ∫
x 00x
4π x − x
μ xl x l 1
L L dx dx
12 21 2 1
∫ ∫
(A.5)
x 00x
4π 2
12 2
x −+x d
( )
where
d is the distance between the conductors, expressed in m.

Figure A.2 – Line current model for a straightened twinaxial cable
The integration results read Formula (A.6) and Formula (A.7):
μl
L Il+−2ln 2lnδ2x− (A.6)
( )
11 0 1
4π
μ
22 22
L lln l+ l+ d+ d− l+ d− llnd
 (A.7)

2π
where
I is a divergent integral in the expression of the self inductance, as in Formula (A.8):
xx+δx 1
21 1
I = dx
(A.8)
∫
xx−δx
21 1 x − x
where
δx > 0 is the half interval length to separate the divergent interval.
It is worth noting that the divergence of I is caused by the line current model and can be
convergent in a three-dimensional model.
=
=
=
=
==
==
==
==
==
==
According to Formula (A.1), the inductance for the straightened cable is as showed in Formula
(A.9):
22
μl 22l + d d
22

L I+ 2ln ld+ − 2ln l+ l+ d− 2lnδ2x−−
( ) (A.9)

s0 1
2πll

Then, regarding a cable with the same length l and conductor distance d, it is bent into an arc
with the radius of r in m and the angle of θ in rad (0 < θ < 2π).
b m m
The partial inductances can be calculated using the line current model in Figure A.3
(Figure A.3 a) showing the front view and Figure A.3 b) showing the top view), as showed in
Formula (A.10) and Formula (A.11):
θθ θ θ cosθθ−
μr ( )
0b 1m 2 m
LL dθdθ
11 22 ∫∫ 2 1
θθ00
8π θθ− (A.10)
sin
cosθθ−
μr θθ θ θ ( )
0b 1m 2 m 21
L L dθdθ
12 21 ∫∫ 2 1 (A.11)
θθ00
4π 2 2 2
2RR− 2 cosθθ−+d
( )
a) Front view b) Top view
Figure A.3 – Line current model for a bent twinaxial cable
==
==
==
==
==
==
=
With the similar treatments as the straightened case, the inductance for the bent cable is
obtained as showed in Formula (A.12):
μl θ θθ= θθδ
82   
1m
0 m 11
Ld=sin+−ln tan θ 2ln tan
b1   
∫
θ=0
2π2θθ 1 4 4
  
 mm
(A.12)

θx− cosθ
2l θθ= ( )
1m m1

+Id−−4 θ
∫
θ=0
2 2 22 
θ 1
m
2l −+2l cosθ dθ
1m

where there are two integrals without closed-form solutions, which can be reached through
simple one-dimensional numerical integration.
The deviation of the inductances between the straightened and bent cables is as showed in
Formula (A.13):
L θ ,ld, L−L
( )
Δ m bs
 θθ=
μl 82θ θ 2d
0 1m 22
m1
sin+ ln tan dθ+ 2ln l+ l+d++ 4ln2

  1
∫
θ=0
2π2θθ 1 4  l

 mm
(A.13)

θθ− cosθ
22l θθ= ( ) l + d
1m m1 1

− dθ − −−2lndθ2ln − 2
1m
∫
θ=0
2 2 22 
θl1
m
2l −+2l cosθ dθ
1m

where no more divergent integral I or separating length δx is included.
0 1
If l >> d and 0 < θ < 2π, L < 0 in Formula (A.13) decreases with θ but increases with l, among
m Δ m
which the relationships at some configurations are illustrated in Figure A.4 a) and b). It can be
seen that the deviation of inductance between a straightened twin axial cable and a bent one
is less than 0,2 nH with the length greater than 10 m.

a) 0 < θ < 11π/6, d = 0,01 m, l = 1 m b) 1 m < l < 100 m, d = 0,01 m, θ = 11π/6
m m
Figure A.4 – The relationships between l, θ and L for a twinaxial cable
m Δ
=
=
A.2.3.3 Coaxial cable inductance deviation
The inductance of a coaxial cable can also be depicted by the line current model, whereas the
outer conductor should be modelled by uniformly distributed line currents, as shown in
Figure A.5 to be distinguished from the inner conductor. The outer conductor can be
represented by n line currents, of which each carries 1/n opposite current intensity to the
oc oc
inner conductor. Taking into account the mutual inductances among the outer line currents, the
self inductance of the outer conductor becomes:
n −1
oc
L
L' + M (A.14)
22 ∑ ock
n n
oc oc
k=1
where
M is the mutual inductance between the two line currents with k/n circumference distance
ock oc
in the outer conductor.
The inductance reads:
L=L+−L' 2M
11 22 12
n −1
oc
(A.15)
= (L+−LM2 )− (22LM− )
11 22 12 ∑ 22 ock
2n
oc
k=1
Figure A.5 – Line current model for the coaxial cable
Estimating M for line currents at different positions in bent layouts with Formula (A.11), the
ock
deviation of the inductances between the straightened and bent coaxial cables is as showed in
Formula (A.16):
n −1
oc
L' L − L (A.16)
ΔΔ ∑ Δ
dr dd
oc ock
2n
oc
k=1
==
=
=
where
L is the deviation of the inductances between the straightened and bent cables for
Δ
twinaxial cables as in Formula (A.13), expressed in H;
r is the efficient radius of the outer conductor, expressed in m;
oc
d is the distance between the two points with k/n circumference in the outer conductor
ock oc
expressed in m.
The distance d can be calculated as:
ock
kπ
dr= 2 sin
(A.17)
oc oc
k
n
oc
Though a larger n is supposed to yield a more precise L ', the result achieves a satisfactory
oc Δ
convergence when n = 10.
oc
The relationships between l, θ and L ' at some configurations are illustrated in Figure A.6.
m Δ
Accordingly, it can be seen that the deviation of inductance between a straightened coaxial
cable and a bent one with the length greater than 10 m is less than 0,02 nH, which is less than
the accuracy of most inductance measurement instrument.

a) 0 < θ < 11π/6, r = 0,01 m, l = 1 m b) 1 m <
...