# IEC 60027-2:2019

(Main)## Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics

## Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics

IEC 60027-2:2019 is applicable to telecommunications and electronics. It gives names and symbols for quantities and their units.

## Symboles littéraux à utiliser en électrotechnique - Partie 2: Télécommunications et électronique

IEC 60027-2:2019 s'applique aux télécommunications et à l'électronique. Elle donne les noms et symboles des grandeurs et unités.

### General Information

### Standards Content (sample)

IEC 60027-2

Edition 4.0 2019-01

INTERNATIONAL

STANDARD

NORME

INTERNATIONALE

Letter symbols to be used in electrical technology –

Part 2: Telecommunications and electronics

Symboles littéraux à utiliser en électrotechnique –

Partie 2: Télécommunications et électronique

IEC 60027-2:2019-01(en-fr)

---------------------- Page: 1 ----------------------

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---------------------- Page: 2 ----------------------

IEC 60027-2

Edition 4.0 2019-01

INTERNATIONAL

STANDARD

NORME

INTERNATIONALE

Letter symbols to be used in electrical technology –

Part 2: Telecommunications and electronics

Symboles littéraux à utiliser en électrotechnique –

Partie 2: Télécommunications et électronique

INTERNATIONAL

ELECTROTECHNICAL

COMMISSION

COMMISSION

ELECTROTECHNIQUE

INTERNATIONALE

ICS 01.060; 33.020 ISBN 978-2-8322-6346-4

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical CommissionMarque déposée de la Commission Electrotechnique Internationale

---------------------- Page: 3 ----------------------

– 2 – IEC 60027-2:2019 © IEC 2019

CONTENTS

FOREWORD ........................................................................................................................... 3

1 Scope .............................................................................................................................. 5

2 Normative references ...................................................................................................... 5

3 Terms and definitions ...................................................................................................... 5

4 Introduction to tables ....................................................................................................... 5

5 Quantities and units ......................................................................................................... 6

5.1 General concepts .................................................................................................... 6

5.2 Linear time-independent networks under sinusoidal conditions ............................. 20

5.2.1 General ......................................................................................................... 20

5.2.2 Two-port networks ......................................................................................... 20

5.2.3 n-port networks .............................................................................................. 28

5.3 Line transmission of signals and telephony ........................................................... 34

5.3.1 Quantities and units in line transmission ........................................................ 34

5.3.2 Subscripts for line transmission ..................................................................... 35

5.3.3 Quantities and units in telephony ................................................................... 36

5.3.4 Subscripts for telephony ................................................................................ 36

5.4 Waveguide propagation ........................................................................................ 37

5.4.1 Frequency and wavelength in a waveguide .................................................... 37

5.4.2 Characteristic and normalized impedance and admittance in general............. 38

5.4.3 Impedance and admittance at a point in a substance ..................................... 39

5.4.4 Impedance and admittance at a point in vacuum ............................................ 40

5.4.5 Impedance and admittance of a waveguide ................................................... 41

5.5 Radiocommunications ........................................................................................... 42

5.5.1 General and tropospheric propagation ........................................................... 42

5.5.2 Ionospheric propagation ................................................................................ 45

5.5.3 Antennas ....................................................................................................... 46

5.5.4 Radio links..................................................................................................... 51

5.6 Optical fibre communication .................................................................................. 53

5.7 Television ............................................................................................................. 59

5.8 Dependability ........................................................................................................ 61

5.9 Piezoelectric resonators ........................................................................................ 62

5.10 Semiconductor devices ......................................................................................... 68

5.11 Electroacoustics ................................................................................................... 68

Bibliography .......................................................................................................................... 73

Figure 1 – Conventions concerning signs in electric circuits .................................................. 20

Figure 2 – Conventions for n-port linear networks ................................................................. 28

Figure 3 – Equivalent circuits of a one-port piezoelectric resonator ....................................... 62

---------------------- Page: 4 ----------------------IEC 60027-2:2019 © IEC 2019 – 3 –

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________

LETTER SYMBOLS TO BE USED IN ELECTRICAL TECHNOLOGY –

Part 2: Telecommunications and electronics

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 in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC

Publication(s)"). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for 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

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.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) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60027-2 has been prepared by IEC technical committee 25:

Quantities and units.This fourth edition cancels and replaces the third edition published in 2005. This fourth edition

constitutes a technical revision.This edition includes the following significant changes with respect to the previous edition:

a) former Subclauses 3.8 and 3.9 are cancelled and replaced by IEC 80000-13:2008;

b) former Subclause 3.10, now 4.8, is revised in accordance with IEC 60050-192:2015;

c) former Subclause 3.11, now 4.9, is revised in accordance with IEC 60050-561:2014;

d) former Subclause 3.13, now 4.11, is revised in accordance with ISO 80000-8:2007,

IEC 60050-801:1994 and IEC 60050-802:2011;e) technical and editorial corrections have been carried out, mainly in Subclause 4.1.

f) tables are simplified, mainly by deleting useless columns.---------------------- Page: 5 ----------------------

– 4 – IEC 60027-2:2019 © IEC 2019

The text of this standard is based on the following documents:

FDIS Report on voting

25/635/FDIS 25/640/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 60027 series, published under the general title Letter symbols to

be used in electrical technology, 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 "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be• reconfirmed,

• withdrawn,

• replaced by a revised edition, or

• amended.

---------------------- Page: 6 ----------------------

IEC 60027-2:2019 © IEC 2019 – 5 –

LETTER SYMBOLS TO BE USED IN ELECTRICAL TECHNOLOGY –

Part 2: Telecommunications and electronics

1 Scope

This part of IEC 60027 is applicable to telecommunications and electronics. It gives names

and symbols for quantities and their units.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 60027-1:1992, Letter symbols to be used in electrical technology – Part 1: General

IEC 60027-1:1992/AMD1:1997IEC 60027-1:1992/AMD2:2005

3 Terms and definitions

No terms and definitions are listed in this document.

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

4 Introduction to tables

In this part of IEC 60027, complex quantities are in general denoted by underlining their

symbols. However, this does not constitute a compulsory rule in applications (see

IEC 60027-1).To avoid any ambiguity, some quantity names are followed by a specific use, enclosed in

angle brackets "<…>" after a comma.When several symbols are indicated for a given quantity, the first is the preferred symbol and

the others are reserve symbols, unless otherwise stated.When several units are indicated for a given quantity, the first is the coherent SI unit, unless

otherwise stated. For logarithmic ratios, the first mentioned unit is the decibel.

For quantities defined as a logarithm of the ratio of two power quantities or two root-power

quantities (also known as field quantities), the submultiple decibel (dB) of the bel (B) is

generally used, rather than the neper (Np). The bel is not explicitly mentioned in the tables.

See IEC 60027-3 and ISO 80000-1:2009, Annex C.---------------------- Page: 7 ----------------------

– 6 – IEC 60027-2:2019 © IEC 2019

5 Quantities and units

5.1 General concepts

Quantity Units

Item

Entry

number

number in Name Symbol Definition and remarks Name Symbol Remarks

IEC 60050

101 101-12-02 signal S A signal is any physical phenomenon whose presence, absence or variation is The unit depends on the

considered as representing information. In general, a signal is a quantity, one or kind of quantity

more parameters of which represent information. constituting the signal(electric current,

In this document, S and S are used for input and output signals respectively.

1 2

voltage, pressure, etc.).

See IEC 60027-1 for other suitable subscripts.

In cases where the type of signal quantity is known, for example, electric current,

voltage, pressure, etc., use the appropriate symbol.With respect to capital and lower-case letters, see IEC 60027-1:1992, 2.1.

102 signal power P "s" (lower case, upright) is used as subscript for "signal". watt W

P In signal theory, the term "instantaneous power" is by convention used for thesig

square of the instantaneous value of a signal. This square is proportional to a

physical power if the signal is a root-power quantity (or field quantity)

(see Note 1 to entry of IEC 60050-103:2009, 103-09-05).

In a physical system, a signal power is always a physical power.

103 signal level L decibel dB

S 1 S

L =10 lg dB= ln Np

L S 2 S neper Np

ref ref

sig

where S and S are two signals of the same kind, S being a reference signal.

ref ref

104 702-07-04 absolute L decibel dB

P 1 P

L =10 lg dB= ln Np

power level;

P 2 P neper Np

ref ref

power level

where P is a power and P is a reference power.

ref

105 702-07-06 absolute decibel dB

U U

L =20 lg dB=ln Np

voltage level;

U U neper Np

ref ref

voltage level

where U is a voltage and U is a reference voltage.

ref

The synonym "voltage level" may be used only where there is no ambiguity.

---------------------- Page: 8 ----------------------

IEC 60027-2:2019 © IEC 2019 – 7 –

Quantity Units

Item

Entry

number

number in

Name Symbol Definition and remarks Name Symbol Remarks

IEC 60050

106 702-07-05 relative decibel dB

L L = L −L

r,x r,x P,x P,0

power level

neper Np

where L and L are the absolute power levels (104) at the measuring point

P,x P,0

and at a reference point, respectively.

107 702-08-03 noise A noise is any variable physical phenomenon, generally a quantity, apparently The unit depends on the

not conveying information and which can be superimposed on, or combined with, kind of quantity

n a wanted signal. constituting the noise(electric current,

Concerning upper and lower-case letters, see IEC 60027-1:1992, 2.1.

n voltage, pressure, etc.).

"n" (lower case, upright) is used as subscript for "noise".

In cases where the type of noise quantity is known, use the appropriate symbol

(for example, I, i for electric current) with n as subscript (e.g. I , i ).

n n

108 103-09-05 power w(f) watt per W/Hz

spectral hertz

P = wf( )d f

density,

or noise>

where f is the frequency and P is the total power.

In signal theory, the term "instantaneous power" is by convention used for the

square of the instantaneous value of a signal or noise. This square is

proportional to a physical power if the signal or the noise is a root-power (or field

quantity). See Note 1 to entry of 103-09-05 in IEC 60050-103:2009.In a physical system, the power spectral density is always a physical power

spectral density.

109 power N The power spectral density (108) is frequency-independent: watt per W/Hz

spectral w(f) = N hertzdensity of

white noise

110 702-08-51 equivalent U Applies to a one-port network. volt V

noise

U is an RMS voltage.

voltage n

---------------------- Page: 9 ----------------------

– 8 – IEC 60027-2:2019 © IEC 2019

Quantity Units

Item

Entry

number

number in

Name Symbol Definition and remarks Name Symbol Remarks

IEC 60050

111 702-08-52 equivalent Applies to a one-port network. ohm Ω

noise

resistance; U

R =

4 kT ∆f

ref

noise

resistance

is the equivalent noise voltage (110), k is the Boltzmann constant, T

where U

n ref

is a reference temperature and ∆f is the frequency bandwidth (154) considered.

The synonym "noise resistance" may be used only where there is no ambiguity.

112 702-08-54 spot noise T(f) Applies to a one-port network. kelvin K

temperature f is frequency.

113 702-08-55 mean noise Applies to a one-port network. kelvin K

temperature

114 702-08-56 equivalent Applies to a two-port network. kelvin K

T ( f )

spot noise f is frequency.

temperature

115 702-08-58 mean Applies to a two-port network. kelvin K

equivalent

The synonym "mean noise temperature" may be used only where there is no

noise

ambiguity.

temperature;

mean noise

temperature

116 702-08-57 spot noise Applies to a two-port network. one 1

Ff()

factor The noise factor is the ratio of the exchangeable power spectral density (108) of

output noise to the power spectral density that would be present at the output if

the only source of noise were input thermal noise at a reference temperatureref

Tf()

Ff() 1+

ref

where T ( f ) is the equivalent spot noise temperature (114).

For exchangeable power, see IEC 60050-702:1992, 702-07-11.

---------------------- Page: 10 ----------------------

IEC 60027-2:2019 © IEC 2019 – 9 –

Quantity Units

Item

Entry

number

number in

Name Symbol Definition and remarks Name Symbol Remarks

IEC 60050

117 702-08-57 spot noise decibel dB

F ( f ) 1

F f = 10 lg Ff dB = ln Ff Np

figure ( ) ( ) ( )

neper Np

F ()f

where is the spot noise factor (116).

In English, "noise factor" is generally used for the arithmetic expression and

"noise figure" is used for the logarithmic expression. See IEC 60050-702:1992,

702-08-57, Note 2.

In French, "facteur de bruit" is generally used in both cases.

118 702-08-59 mean noise Applies to a two-port network. one 1

factor;

F 1+

noise factor

ref

where T is the mean equivalent noise temperature (115) and T is a reference

ref

temperature.

The synonym "noise factor" may be used only where there is no ambiguity.

119 702-08-59 mean noise decibel dB

F 1

FF10 lg dB ln F Np

figure;

neper Np

noise figure

where F is the mean noise factor (118).

In English, "noise factor" is generally used for the arithmetic expression and

"noise figure" is used for the logarithmic expression. See IEC 60050-702:1992,

702-08-59, Note 2.

In French, "facteur de bruit" is generally used in both cases and the adjective

"logarithmique" is omitted in practice.

The synonym "noise figure" may be used only where there is no ambiguity.

120 702-08-61 signal-to- k Signal power (102) divided by noise power. one 1

noise ratio;

In practice, the symbol S/N is generally used.

SNR

---------------------- Page: 11 ----------------------

– 10 – IEC 60027-2:2019 © IEC 2019

Quantity Units

Item

Entry

number

number in

Name Symbol Definition and remarks Name Symbol Remarks

IEC 60050

121 702-08-61 signal-to- K decibel dB

Kk= 10 lg dB = ln k Np

noise

SN SN SN

neper Np

logarithmic

ratio

where k is the signal-to-noise ratio (120).

In practice, the term "signal-to-noise ratio" and the symbol S/N are generally

used.

122 103-07-17 growth Example: decibel dB/s

coefficient per

Np/s

σ t

second

ut = u e sin ω t

( )

neper

where u(t) is a sinusoidal function of time t, with angular frequency ω and per

second

amplitude .

123 103-05-24 damping δ =−σ decibel dB/s

coefficient per

Np/s

where is the growth coefficient (122).

second

neper

per

second

124 103-07-16 complex s second s Special units are only

s =σ + jjω =−+δω

angular to the used when the real and

power imaginary parts are

frequency;

where is the angular frequency, is the growth coefficient (122) and δ is

ω σ

of treated separately.

complex

the damping coefficient (123).

minus

frequency

one

---------------------- Page: 12 ----------------------

IEC 60027-2:2019 © IEC 2019 – 11 –

Quantity Units

Item

Entry

number

number in

Name Symbol Definition and remarks Name Symbol Remarks

IEC 60050

125 131-15-20 transfer H The unit of the quantity

Ss()

function H is the quotient of the

Hs() =

unit of s (t) by the unit

Ss()

of s (t).

and S , respectively, are the complex representations of the input and

where S

1 2

output signals, respectively, as functions of the complex angular frequency s

(124).

The complex quantities are generally the Laplace transforms of the time-varying

quantities:

Lst()

H =

Lst()

where Ls (t) and Ls (t) are the Laplace transforms of the signals s (t) and s (t)

1 2 1 2and t is time.

126 transfer gain The unit is the same as

G()ω

GH(ωω) = (j )

for H.

where H (σω+ j ) is the transfer function (125).

127 transfer The unit is the

A()ω AG()ωω= 1 / ()

attenuation reciprocal of the unit of

G(ω)

where is the transfer gain (126).

128 transfer If the transfer function H (125) is of dimension one (see IEC 60050-112:2010, one 1 Special units are only

exponent 112-01-13): used when the real andimaginary parts are

HG(jωω) ( )exp[−=jB(ω)] exp[Γ (ω)]

treated separately.

Γ AB− j (see 129 and 130).

See also image transfer coefficient (IEC 60050-131:2002, 131-15-25).

129 logarithmic A decibel dB

A 20 (lg e) Re ()ΓΓdB Re () Np

transfer

neper Np

attenuation

where Γ is the transfer exponent (128) and e is the base of the natural

logarithm.

In practice, "transfer attenuation" is used.

---------------------- Page: 13 ----------------------

– 12 – IEC 60027-2:2019 © IEC 2019

Quantity Units

Item

Entry

number

number in

Name Symbol Definition and remarks Name Symbol Remarks

IEC 60050

130 phase radian rad

B(ωω) = Im(ΓH) = − arg (j )

change; 1° = rad

degree

ϕ 180

where is the transfer function (125) and Γ is the transfer exponent

H (σω+ j )

phase shift

(128).

131 voltage one 1

a =

attenuation U

factor

where U and U are two voltages. Subscripts 1 and 2 can for example designate

1 1

the input port and the output port, respectively, of a two-port network. The

inverse of the voltage attenuation factor is the voltage gain factor (133).

In practice, "voltage attenuation" is used.

132 logarithmic

decibel dB

A A =20 lg a dB=ln a Np

U U U U

voltage

neper Np

attenuation

where is voltage attenuation factor (131). When the logarithmic voltage

attenuation is negative, its absolute value is the logarithmic voltage gain (134).

In practice, "voltage attenuation" is used.133 voltage gain one 1

g U

U 2

g =

factor

where U and U are two voltages. Subscripts 1 and 2 can, for example,

1 1

designate the input port and the output port, respectively, of a two-port network.

The inverse of the voltage gain factor is the voltage attenuation factor (131).In practice, "voltage gain" is used.

134 logarithmic decibel dB

G G =20 lg g dB=ln g Np

U U U U

voltage gain

neper Np

where g is the voltage gain factor (133). When the logarithmic voltage gain is

negative, its absolute value is the logarithmic voltage attenuation (132).

In practice, "voltage gain" is used.

---------------------- Page: 14 ----------------------

IEC 60027-2:2019 © IEC 2019 – 13 –

Quantity Units

Item

Entry

number

number in

Name Symbol Definition and remarks Name Symbol Remarks

IEC 60050

135 702-02-10 power loss S instead of P in the case of apparent powers. one 1

Use subscript

factor;

power a =

attenuation 2

factor

Subscripts 1 and 2 are used to designate the power of a signal at two points, for

example, input and output of a two-port network, or th**...**

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