IEC 60728-103:2026

• Abstract:

  IEC 60728-103:2026 specifies the measuring methods, performance requirements and data publication requirements for active wideband equipment of cable networks for television signals, sound signals and interactive services with digital signals only.; This document:; - applies to all amplifiers used in cable networks;; - covers the frequency range 5 MHz to 3 000 MHz;; NOTE The upper limit of 3 000 MHz is an example, but not a strict value.; - applies to one-way and two-way equipment;; - specifies the basic methods of measurement of the operational characteristics of the active equipment in order to assess the performance of this equipment;; - identifies the performance specifications to be published by the manufacturers;; - states the minimum performance requirements of certain parameters.; While IEC 60728-3:2017 has served as a basis for its development, this document describes the methods of measurement for digital modulated signals only. It also covers the Data Over Cable Service Interface Specification (DOCSIS) 4.0 requirements with additional digital modulation schemes as well as for the extended frequency ranges:; - up to 1 794 MHz for the forward path;; - up to 684 MHz for the return path.; IEC 60728-3:2017, fifth edition, has served as a basis for the development of this document.

• Status: Published
• Publication Date: 02-Nov-2026
• ICS: 33.060.40 - Cabled distribution systems
• ICS: 33.170 - Television and radio broadcasting
• Technical Committee: TA 5 - Cable networks for television signals, sound signals and interactive services
• Drafting Committee: WG 3 - TC 100/TA 5/WG 3
• Current Stage: PPUB - Publication issued
• Start Date: 03-Nov-2026
• Completion Date: 04-Dec-2026

IEC 60728-103 ®
Edition 1.0 2026-11
INTERNATIONAL
STANDARD
Cable networks for television signals, sound signals and interactive services -
Part 103: Active wideband equipment for cable networks with digital signals only
ICS 33.060.40; 33.170 ISBN 978-2-8327-1590-1

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CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, symbols and abbreviated terms . 8
3.1 Terms and definitions. 8
3.2 Symbols . 12
3.3 Abbreviated terms . 13
4 Methods of measurement . 13
4.1 General . 13
4.2 Linear distortion . 14
4.2.1 Return loss . 14
4.2.2 Group delay variation . 15
4.3 Non-linear distortion . 16
4.3.1 General . 16
4.3.2 Types of measurements. 16
4.3.3 Intermodulation . 16
4.3.4 Method of measurement of non-linearity for pure digital channel load for

channel loads up to 1 218 MHz . 19
4.3.5 Method of measurement of non-linearity for pure digital channel load for
channel loads up to 1 794 MHz . 24
4.3.6 Hum modulation of carrier. 28
4.4 Noise figure . 32
4.4.1 General . 32
4.4.2 Equipment required . 32
4.4.3 Connection of equipment . 32
4.4.4 Measurement procedure . 32
4.5 Crosstalk attenuation . 33
4.5.1 Crosstalk attenuation for loop-through ports . 33
4.5.2 Crosstalk attenuation for output ports . 33
4.6 Immunity to surge voltages . 35
4.6.1 General . 35
4.6.2 Equipment required . 36
4.6.3 Connection of equipment . 36
4.6.4 Measurement procedure . 36
5 Performance requirements . 36
5.1 General requirements . 36
5.2 Safety . 36
5.3 Electromagnetic compatibility (EMC) . 37
5.4 Frequency range . 37
5.5 Impedance and return loss . 37
5.6 Gain . 37
5.6.1 Minimum and maximum gain . 37
5.6.2 Gain control . 37
5.6.3 Slope and slope control . 37
5.7 Flatness . 37
5.8 Test points . 38
5.9 Noise figure . 38
5.10 Non-linear distortion . 38
5.10.1 General . 38
5.10.2 Second-order distortion . 38
5.10.3 Third order distortion . 38
5.10.4 Maximum operating level for pure digital channel load . 38
5.11 Hum modulation . 39
5.12 Power supply . 39
5.13 Environmental information . 39
5.13.1 General . 39
5.13.2 Transportation . 39
5.13.3 Installation or maintenance . 39
5.13.4 Operation . 40
5.14 Marking of ports . 40
5.15 Requirements for multi-switches . 40
5.15.1 Control signals for multi-switches . 40
5.15.2 Amplitude frequency response flatness . 40
5.15.3 Return loss . 40
5.15.4 Through loss. 40
5.15.5 Isolation. 40
5.15.6 Crosstalk attenuation . 41
5.15.7 Satellite IF to terrestrial signal isolation . 41
5.16 Immunity to surge voltages . 41
5.16.1 Degrees of testing levels . 41
5.16.2 Recommendation of testing level degree . 41
Annex A (normative) Test carriers, levels and intermodulation products . 42
A.1 General considerations on intermodulation products . 42
A.1.1 General . 42
A.1.2 Two signals. 42
A.1.3 Three signals . 43
A.2 Two signal tests for second- and third-order products . 43
A.2.1 Intermodulation products with test signals at frequencies f and f , see
a b
Table A.3 . 43
A.2.2 Signal levels . 44
A.3 Three signal tests for third order products – Intermodulation products with
test signals at frequencies f , f and f , see Table A.4 and Figure A.3 . 45
a b c
Annex B (informative) Measurement errors that occur due to mismatched equipment . 46
Annex C (informative) Examples of measurement channels . 47
C.1 Operating frequency range 110 MHz to 1 006 MHz . 47
C.2 Operating frequency range 258 MHz to 1 218 MHz . 47
C.3 Operating frequency range 258 MHz to 1 794 MHz . 47
Bibliography . 48

Figure 1 – Basic arrangement of test equipment for evaluation of the ratio of signal to
intermodulation product . 17
Figure 2 – BER measurement test configuration . 20
Figure 3 – CINR measurement test setup. 26
Figure 4 – Plot of CINR in dB curve (forward path) as function of EUT channel output
signal level in dB(μV) . 28
Figure 5 – Carrier to hum ratio . 28
Figure 6 – Test set-up for local-powered objects . 29
Figure 7 – Test set-up for remote-powered objects . 30
Figure 8 – Spectrum analyser display . 30
Figure 9 – Measurement of noise figure . 32
Figure 10 – Measurement of crosstalk attenuation for loop-through ports of multi-
switches . 35
Figure 11 – Measurement set-up for surge immunity test . 36
Figure A.1 – An example showing products formed when 2f > f . 44
a b
Figure A.2 – An example showing products formed when 2f < f . 44
a b
Figure A.3 – Products of the form f ± f ± f . 45
a b c
Figure B.1 – Error concerning return loss measurement . 46
Figure B.2 – Maximum ripple . 46

Table 1 – Graphical symbols used in figures . 12
Table 2 – Measurement parameters for full channel load . 22
Table 3 – Common RF output profiles for characterization for the channel bandwidth
of 8 MHz . 24
Table 4 – Measurement parameters for full channel load . 25
Table 5 – Example of return loss requirements . 37
Table 6 – Parameters of surge voltages for different degrees of testing levels . 41
Table 7 – Recommendations for degree of testing levels . 41
Table A.1 – Intermodulation products with two signals . 42
Table A.2 – Intermodulation products with three signals. 43
Table A.3 – Intermodulation products with two signals . 43
Table A.4 – Intermodulation products with three signals. 45

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Cable networks for television signals,
sound signals and interactive services -
Part 103: Active wideband equipment for cable networks
with digital signals only
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
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the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 60728-103 has been prepared by IEC technical committee 100: Audio, video and
multimedia systems and equipment. It is an International Standard.
IEC 60728-3:2017, fifth edition, has served as a basis for the development of this document.
The text of this International Standard is based on the following documents:
Draft Report on voting
100/4567/FDIS 100/4617/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.
The list of all the parts of the IEC 60728 series, published under the general title Cable networks
for television signals, sound signals and interactive services, can be found on the IEC website.
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.
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.
INTRODUCTION
International Standards and other deliverables of the IEC 60728 series deal with cable networks,
including equipment and associated methods of measurement for headend reception,
processing and distribution of television and sound signals and for processing, interfacing and
transmitting all kinds of data signals for interactive services using all applicable transmission
media. These signals are typically transmitted in networks by frequency-multiplexing techniques.
This includes for instance:
– regional and local broadband cable networks,
– extended satellite and terrestrial television distribution systems,
– individual satellite and terrestrial television receiving systems,
and all kinds of equipment, systems and installations used in such cable networks, distribution
and receiving systems.
The extent of this standardization work is from the antennas and/or special signal source inputs
to the headend or other interface points to the network up to the terminal input of the customer
premises equipment.
The standardization work considers coexistence with users of the radio frequency (RF)
spectrum in wired and wireless transmission systems.
The standardization of any user terminals (i.e. tuners, receivers, decoders, multimedia
terminals, etc.) as well as of any coaxial, balanced and optical cables and accessories thereof
is excluded.
1 Scope
This part of IEC 60728 specifies the measuring methods, performance requirements and data
publication requirements for active wideband equipment of cable networks for television signals,
sound signals and interactive services with digital signals only.
This document:
– applies to all amplifiers used in cable networks;
– covers the frequency range 5 MHz to 3 000 MHz;
NOTE The upper limit of 3 000 MHz is an example, but not a strict value.
– applies to one-way and two-way equipment;
– specifies the basic methods of measurement of the operational characteristics of the active
equipment in order to assess the performance of this equipment;
– identifies the performance specifications to be published by the manufacturers;
– states the minimum performance requirements of certain parameters.
While IEC 60728-3:2017 has served as a basis for its development, this document describes
the methods of measurement for digital modulated signals only. It also covers the Data Over
Cable Service Interface Specification (DOCSIS) 4.0 requirements with additional digital
modulation schemes as well as for the extended frequency ranges:
– up to 1 794 MHz for the forward path;
– up to 684 MHz for the return path.
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 60068-1, Environmental testing - Part 1: General and guidance
IEC 60068-2-1, Environmental testing - Part 2-1: Tests - Tests A: Cold
IEC 60068-2-2, Environmental testing - Part 2-2: Tests - Tests B: Dry heat
IEC 60068-2-6, Environmental testing - Part 2-6: Tests - Test Fc: Vibration (sinusoidal)
IEC 60068-2-14, Environmental testing - Part 2-14: Tests - Test N: Change of temperature
IEC 60068-2-27, Environmental testing - Part 2-27: Tests - Test Ea and guidance: Shock
IEC 60068-2-30, Environmental testing - Part 2-30: Tests - Test dB: Damp heat, cyclic
(12 h + 12 h cycle)
IEC 60068-2-31, Environmental testing - Part 2-31: Tests - Test Ec: Rough handling shocks,
primarily for equipment-type specimens
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60728-2, Cable networks for television signals, sound signals and interactive services -
Part 2: Electromagnetic compatibility for equipment
IEC 60728-4, Cable networks for television signals, sound signals and interactive services -
Part 4: Passive wideband equipment for coaxial cable networks
IEC 60728-11, Cable networks for television signals, sound signals and interactive services -
Part 11: Safety
IEC 61000-4-5, Electromagnetic compatibility (EMC) - Part 4-5: Testing and measurement
techniques - Surge immunity test
IEC 61319-1, Interconnections of satellite receiving equipment - Part 1: Europe
IEC 61319-2, Interconnections of satellite receiving equipment - Part 2: Japan
IEC 62368-1, Audio/video, information and communication technology equipment - Part 1:
Safety requirements
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the following terms, definitions, symbols and abbreviated
terms apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
– IEC Electropedia: available at http://www.electropedia.org/
– ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions
3.1.1
amplitude frequency response
gain or loss of equipment or system plotted against frequency
3.1.2
attenuation
ratio of the input power to the output power of equipment or system, usually expressed in
decibels
3.1.3
carrier-to-noise ratio
difference in decibels between the vision or sound carrier level at a given point in equipment or
system and the noise level at that point (measured within a bandwidth appropriate to the
television or radio system in use)
3.1.4
CIN
composite intermodulation noise
sum of noise and intermodulation products from digital modulated signals
3.1.5
CINR
composite intermodulation and noise ratio
ratio of the signal level and the CIN level
3.1.6
CCN
carrier to composite noise
component which is the summation of thermal noise and intermodulation noise (i.e. noise-like
intermodulation distortion products)
Note 1 to entry: The composite noise produced by the amplifier CCN in this document is CINR in accordance with
ANSI-SCTE 279.
[SOURCE: ANSI/SCTE 279:2022, 7.2.8.1, modified – reference to amplifier omitted from
definition. Reproduced with the permission of SCTE.]
3.1.7
crosstalk attenuation
ratio of the wanted signal power to the unwanted signal power, which is caused by
electromagnetic coupling between two leads, while equal signal powers are applied to the leads
Note 1 to entry: Crosstalk attenuation is usually expressed in decibels.
3.1.8
equaliser
device designed to compensate over a certain frequency range for the amplitude/frequency
distortion or phase/frequency distortion introduced by feeders or equipment
Note 1 to entry: This device is for the compensation of linear distortions only.
3.1.9
feeder
transmission path forming part of a cable network
Note 1 to entry: Such a path may consist of a metallic cable, optical fibre, waveguide or any combination of them.
By extension, the term is also applied to paths containing one or more radio links.
3.1.10
gain
ratio of the output power to the input power, usually expressed in decibels
3.1.11
thermal noise
noise generated in a resistive component due to the thermal agitation of electrons
Note 1 to entry: The thermal power generated is given by

P= 4· B · kT·
where
P is the noise power, in Watts;
B is the bandwidth, in Hertz;
-23
k is the Boltzmann constant = 1,38 × 10 J/K;
T is the absolute temperature, in Kelvin.
It follows that
U
= 4· B · kT·
R
and
U= 4 ···R B kT·
where
U is the noise voltage, in Volts (e.m.f.);
R is the resistance, in Ω.
In practice, it is normal for the source to be terminated with a load equal to the internal resistance value, the noise
voltage at the input is then U/2.
3.1.12
level
decibel ratio of any power P to the standard reference power P , i.e.
1 0
P
10lg
P
decibel ratio of any voltage U to the standard reference voltage U , i.e.
1 0
U
20lg
U
Note 1 to entry: The power level may be expressed in decibels relative to P = (U /R) = (1/75) pW, i.e. in dB(P ),
0 0 0
taking into account that the level of P corresponds to 0 dB(P ) or, as more usually, in dB(pW), taking into account
0 0
that the level of P corresponds to -18,75 dB(pW). The voltage level is expressed in decibels relative to 1 µV (across
75 Ω), i.e. in dB(µV).
3.1.13
MER
modulation error ratio
sum of the squares of the magnitudes of the ideal symbol vectors is divided by the sum of the
squares of the magnitudes of the symbol error vectors of a sequence of symbols, the result
being expressed as a power ratio in dB
N

IQ+
( )
∑ jj
j=1
R = 10 lg in dB

ME
N
δI +δQ
∑ ( j j)
j=1

3.1.14
multi-switch
equipment used in distribution systems for signals that are received from satellites and
converted to a suitable IF
Note 1 to entry: The IF signals that are received from different polarisations, frequency bands and orbital positions
are input signals to the multi-switch. Subscriber feeders are connected to the multi-switch output ports. Each output
port is switched to one of the input ports, depending on control signals that are transmitted from the subscriber
equipment to the multi-switch. Besides a splitter for each input port and a switch for each output port, a multi-switch
can contain amplifiers to compensate for distribution or cable losses.
3.1.15
multi-switch loop-through port
one or more ports to loop through the input signals through a multi-switch
Note 1 to entry: This enables larger networks with multiple multi-switches, each one installed close to a group of
subscribers. The multi-switches are connected in a loop-through manner. The IF signals that are received by an
outdoor unit from different polarisations, frequency bands and orbital positions are input signals to a first multi-switch.
Cables connect the loop-through ports of this multi-switch to the input ports of a second multi-switch and so on.
3.1.16
slope
difference in gain or attenuation at two specified frequencies between any two points in an
equipment or system
Note 1 to entry: The slope sign is considered
a) negative when the attenuation increases with frequency (cables) or the gain (amplifiers) decreases with
frequency,
b) positive when the gain (amplifiers) increases with frequency (compensating slope).
3.1.17
surge voltage
surge which is produced by a direct or indirect lightning stroke
3.1.18
symbol rate
mega symbols per second, expressed as Msymb/s
3.2 Symbols
The following graphical symbols in Table 1 are used in the figures of this document. These
symbols are either listed in IEC 60617, are modifications of symbols defined in IEC 60617 or
are composite symbols made up of more than one symbol defined in IEC 60617.
Table 1 – Graphical symbols used in figures
Symbols Terms Symbols Terms
Voltmeter
Ampere meter
[IEC 60617-S00913 (1996-05),
[IEC 60617-S00910 (1996-05),
modified – grey background
modified – letter "A" added]
added.]
Equipment under test
Power meter
[IEC 60617-S00059 (1996-05),
modified – "EUT" text added, and [IEC 60617-S00910 (1996-05),

thick black line and grey border modified – letter "W" added.]
added to box.]
Signal generator
Noise generator
[IEC 60617-S00899 (1996-05),
[IEC 60617-S01230 (2002-07)]
IEC 60617-S01403 (2001-09)]
Surge generator Variable signal generator
[IEC 60617-S01228 (1996-05), [IEC 60617-S01229 (1996-05,
modified – thick black line and grey modified – letter "f" and

border added to box.] connection line omitted.]
Low-pass filter High-pass filter
[IEC 60617-S01248 (1996-05)] [IEC 60617-S01247 (1996-05)]

Band-pass filter Band-stop filter
[IEC 60617-S01249 (1996-05)] [IEC 60617-S01250 (1996-05)]

Spectrum analyser (electrical) Attenuator
[IEC 60617-S00910 (1996-05), [IEC 60617-S01244 (1996-05),

modified] modified]
Variable attenuator Amplifier
[IEC 60617-S01245 (1996-05)] [IEC 60617-S01239 (1996-05)]

Combiner
Variable resistor
[IEC 60617-S00059 (1996-05),
[IEC 60617-S00557 (1996-06)]
modified]
Functional equipotential bonding RF choke

[IEC 60617-S01410 (2001-11), [IEC 60617-S00583 (1996-06),

modified] modified]
Capacitor
Resistor
[IEC 60617-S00567 (1996-06),
[IEC 60617-S00555 (1996-06)]
modified]
3.3 Abbreviated terms
AC alternating current
AM amplitude modulation
ANSI American National Standards Institute
BER bit error ratio
CATV community antenna television (system)
CCN carrier to composite noise
CIN composite intermodulation noise
CINR composite intermodulation and noise ratio
CW continuous wave
DC direct current
DVB-C digital video broadcasting baseline system for digital cable television
(ETSI EN 300 429)
EMC electromagnetic compatibility
EUT equipment under test
HP high pass
IF intermediate frequency
LF low frequency
LP low pass
MER modulation error ratio
OFDM orthogonal frequency-division multiplexing
QAM quadrature amplitude modulation
RF radio frequency
RMS root mean square
TCP total composite power
SCTE Society of Cable Telecommunications Engineers
TV television
4 Methods of measurement
4.1 General
This Clause 4 defines basic methods of measurement. Ensure that all test equipment is
calibrated and all connectors, leads, and terminations have an adequate quality in order to not
affect the test results.
Unless otherwise specified by the manufacturer, all measurements shall be carried out with
0 dB plug-in attenuators and equalisers. The position of variable controls used during the
measurements shall be published.
A network can be used to distribute terrestrial signals in addition to the signals received from
satellites. The terrestrial antennas are connected to an optional terrestrial input port of a
multi-switch. On each output port, the terrestrial signals are available in addition to the satellite
IF signals. Since the normal frequency ranges for terrestrial signals and satellite IF signals do
not overlap, both can be carried on the same cable.
For large networks with loop-through connected multi-switches, two possibilities exist to carry
the terrestrial signals from one multi-switch to another multi-switch:
– to use a specialised cable for the terrestrial signal, in addition to the cables used for the
satellite IF signals and then, on each output port the terrestrial signal is combined with the
selected satellite IF signal;
– to combine the terrestrial signal with each satellite IF signal before the first multi-switch in
order to minimise the number of cables between multi-switches.
The signal coming from an outdoor unit for satellite reception can contain unwanted signal-
components with frequencies below the foreseen satellite IF frequency range. These signal-
components overlap with the frequency range of terrestrial signals. For example, an outdoor
unit that converts the frequency band 11,7 GHz to 12,75 GHz to the satellite IF frequency range
can convert signals in the 10,7 GHz to 11,7 GHz band to frequencies below the satellite IF
frequency range. These frequencies have to be sufficiently filtered out to avoid interference
with terrestrial signals on the same cable.
For measurements on multi-switches, it is necessary that control signals be fed to the output
ports that are involved in the measurement. Therefore, a bias-tee shall be connected between
the multi-switch output port and the measurement set. The DC port of the bias-tee is connected
to a standard receiver that generates the required control signals. Ensure that the influence of
the bias-tee on the measurement result is insignificant. This can be achieved by including it into
the calibration or using a network analyser with a built-in bias-tee.
4.2 Linear distortion
4.2.1 Return loss
4.2.1.1 General
Return loss is the ratio of the reflected power to the incident power in dB. The method described
is applicable to the measurement of the return loss of equipment operating in the frequency
range 5 MHz to 3 000 MHz.
All input and output ports of the unit shall meet the specification under all conditions of
automatic and manual gain controls and with any combination of plug-in equalisers and
attenuators fitted.
4.2.1.2 Equipment required
A network analyser covering the frequency range of the equipment to be tested is required.
4.2.1.3 Measurement procedure
All coaxial input and output ports, other than those under test, shall be terminated in 75 Ω.
Ensure that there is no supply voltage on the port being measured as this could damage the
network analyser. If it is necessary to use a voltage blocking device, use one with a good return
loss (10 dB above the expected test result). Return loss shall be measured at all RF signal ports
of the EUT. Take into account the impact of test equipment mismatch as detailed in Annex B
and adjust the results accordingly.
4.2.1.4 Presentation of the results
The value of the return loss (in dB) and the frequency value (in MHz) of the measurement shall
be stated with the results.
4.2.2 Group delay variation
4.2.2.1 General
The group delay (G ) is a parameter affected by the physical length and propagation velocity
D
in the passive and active circuits involved, where frequency-selective components, such as L-C
filters, e.g. diplexers, and amplifiers, are present.
G is defined as the negative derivative of phase with respect to frequency, and is expressed
D
in Formula (1)
= -(dφ/dΩ)
G
(1)
D
The G value is measured in time units and usually expressed in nanoseconds.
D
The group delay variation (G ), also called group delay distortion, is the absolute value of the
DV
difference between the maximum and minimum group delay within a specified frequency interval,
i.e. between one frequency and another in a circuit, device, or system. The group delay variation
(G ) is calculated using Formula (2).
DV
G = │- (dφ /dΩ ) │- │- (dφ /dΩ ) │
(2)
DV 1 1 2 2
The frequency interval is defined by the given specifications for the equipment under test or
can be derived from the specification of the transmission system. In cascaded systems, group
delay variation of each (cascaded) device accumulates and simple summation is assumed.
NOTE 1 Example for G derivation of cascaded systems:
DV
If the system allows a G of 120 ns, a maximum number of 6 devices, with a G of 20 ns for each device, can be
DV DV
cascaded.
NOTE 2 The term 'group delay' is wrongly used in some documents instead of group delay variation.
4.2.2.2 Equipment required
The following equipment is required: a vector network analyzer covering the frequency range
of the equipment to be tested and with features to measure transmission group delay (G ) and
D
frequency response at the specified frequencies.
4.2.2.3 Measurement procedure
The measurement procedure is as follows:
a) Calibrate and align the vector network analyser in the same manner as for linear distortion
measurements.
b) Set frequency markers in frequency steps according to the specified frequency interval.
NOTE Examples of typical frequency intervals (bandwidths) can be found in IEC 60728-101:2016, Annex C.
c) The frequency interval over which the G measurement is made shall be recorded.
D
d) Set the smoothing function in the network analyser according to the recommendations of
the manual of the test equipment manufacturer to get the optimum reading of the values.
e) Plot the G curve versus the specified frequency interval and record it.
D
f) Read the G values for frequency 1 (Ω ) and frequency 2 (Ω ), calculate the difference
D 1 2
(G ) between the two values and record the result.
DV
4.2.2.4 Presentation of the results
Present the group delay variation results (G ) and the specified frequency interval.
DV
4.3 Non-linear distortion
4.3.1 General
In a non-linear device, the expression for the output signal will, in general, have an infinity of
terms, each generated from one or more of the (assumed sinusoidal) terms in the input, and
particularly by the interaction of two or more terms.
4.3.2 Types of measurements
Measurements related to the following phenomena are described:
– intermodulation between two or three single frequency signals;
– intermodulation between digital modulated signals.
The specification shall include at least the following details:
a) the particular effect that is measured;
b) the required signal to distortion ratio.
The result of the measurement shall be given as the worst-case maximum signal level at the
equipment output that allows the required signal to distortion ratio to be met. If the output level
is sloped with frequency, this shall be defined.
The effect shall be defined as being of a particular order (e.g. "third-order intermodulation").
4.3.3 Intermodulation
4.3.3.1 General
The two equal carrier and the three equal carrier methods specified are applicable to the
measurement of the ratio of the carrier to a single intermodulation product at a specified point
within the cable network. The methods can also be used to determine the intermodulation
performance of individual items of equipment.
Examples of second-order and third-order intermodulation products are given in Annex A.
Second-order products are encountered only in wideband equipment and systems, covering
more than one octave, and shall be measured using
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