1、 Recommendation ITU-R TF.686-3(12/2013)Glossary and definitions of time and frequency termsTF SeriesTime signals and frequency standards emissionsii Rec. ITU-R TF.686-3 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-
2、frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radi
3、ocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of
4、 patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommenda
5、tions (Also available online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and r
6、elated satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering T
7、F Time signals and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2014 ITU 2014 All rights reserved. No part of this publication may be reproduc
8、ed, by any means whatsoever, without written permission of ITU. Rec. ITU-R TF.686-3 1 RECOMMENDATION ITU-R TF.686-3* Glossary and definitions of time and frequency terms (1990-1997-2002-2013) Scope The terms listed in Annex 1 are taken from relevant ITU-R and ITU-T Recommendations, ITU-R Handbooks,
9、the International Vocabulary of basic and general terms in Metrology (VIM) published by International Organization for Standardization (ISO), the Glossary of Time and Frequency Terms of the National Institute of Standards and Technology (NIST), and other noted references. Annex 1 also includes a num
10、ber of related telecommunication terms in general usage in the field of frequency and time. Two types of terms are presented; those typically used within the standard-frequency and time-signal services and those in more general use, but specifically applicable to this field. The ITU Radiocommunicati
11、on Assembly, considering a) that it is essential for the work of the ITU that terms should be used in a clearly defined and uniform manner; b) that there is a need for a common terminology for the unambiguous specification and description of frequency and time standard systems; c) that there is a ne
12、ed to promote a consistent use of terminology across the growing community of users of frequency and time standard systems, recommends 1 that Annex 1 be used as a glossary and as definitions of time and frequency terms for the users of standard-frequency and time-signal services. References ITU-R Re
13、commendations TF.457: Use of the modified Julian date by the standard-frequency and time-signal services TF.460: Standard-frequency and time-signal emissions TF.538: Measures for random instabilities in frequency and time (phase) TF.768: Standard frequencies and time signals TF.1010: Relativistic ef
14、fects in a coordinate time system in the vicinity of the Earth TF.1153: The operational use of two-way satellite time and frequency transfer employing pseudorandom noise codes TF.2018: Relativistic time transfer in the vicinity of the Earth and in the solar system. *This Recommendation should be bro
15、ught to the attention of the Telecommunication Standardization Bureau (TSB) and the International Organization for Standardization (ISO). 2 Rec. ITU-R TF.686-3 ITU-R Handbooks Selection and use of precise frequency and time systems Satellite time and frequency transfer and dissemination. ITU Radio R
16、egulations ITU-T Recommendations G.810: Definitions and terminology for synchronization networks G.811: Timing characteristics of primary reference clocks. Other references IEV: International electrotechnical vocabulary ISO 8601: Representation of dates and times NIST: Glossary of Time and Frequency
17、 Terms NTP: Network time protocol (www.ntp.org) PTP: Precision time protocol IEEE 1588 Standard for a precision clock synchronization protocol for networked measurement and control systems ANSI: American National Standards Institute BIPM: VIM JCGM 200: 2012 BIPM: GUM Guide to the expression of uncer
18、tainty in measurement JCGM100: 2008 BIPM: SI Brochure. Annex 1 Glossary and definition of time and frequency terms accuracy; exactitude; exactitud Closeness of the agreement between the result of a measurement and the true value of the measurand. See GUM, VIM. active frequency standard; talon de frq
19、uence actif; patrn de frecuencia activo An atomic oscillator whose output signal is derived from the radiation emitted by the atomic species providing the atomic reference transition. The electronic system detects the transition, and servo controls the phase and frequency of a quartz oscillator on t
20、he received frequency. The most prominent example is the hydrogen maser. See Hydrogen Maser frequency standard. ageing; vieillissement; envejecimiento The systematic change in frequency with time due to internal changes in the oscillator. NOTE 1 It is the frequency change with time when factors exte
21、rnal to the oscillator (environment, power supply, etc.) are kept constant. Rec. ITU-R TF.686-3 3 Allan variance (AVAR)/Allan deviation (ADEV); variance dAllan (AVAR)/cart type dAllan (ADEV); varianza/desviacin tpica de Allan (AVAR/ADEV) A standard method of characterizing the frequency instability
22、of oscillators in the time domain, both short term and long term. See “two-sample deviation/variance”. all-in-view GNSS time transfer; transfert de signaux horaires partir de tous les satellites GNSS visibles; transferencia de seales horarias de todos los GNSS a la vista In this technique, data is c
23、ollected from all GNSS satellites in view during a specified time interval to establish the offset of a local clock to each of the observed satellite clocks. The local clock offset to IGST can then be computed by using IGS precise satellite orbits and clock offset products. Then any two local clocks
24、 can be compared at any distance by a simple difference, with an uncertainty which is largely independent of the distance. This technique provides significant improvement in measurement precision over common view time transfer in case of baselines 1 000 km. atomic clock/frequency standard; talon de
25、frquence/horloge atomique; reloj atmico/patrn de frecuencia An atomic clock keeps time using an oscillator based on an electronic transition frequency in the microwave, optical or ultraviolet region of the electromagnetic spectrum of atoms. atomic time-scale; chelle de temps atomique; escala de tiem
26、po atmico A time-scale based on atomic or molecular resonance phenomena. Elapsed time is measured by counting cycles of a frequency locked to an atomic or molecular transition. bandwidth; largeur de bande; anchura de banda Absolute value of the difference between the limiting frequencies of a freque
27、ncy band. beat frequency; frquence de battement; frecuencia de batido The interference between two different frequencies that results in a periodic variation in frequency whose rate is the difference between the two input frequencies. bias; biais; error sistemtico Estimate of a systematic measuremen
28、t error/uncertainty. See GUM. Caesium beam frequency standard; talon de frquence jet de csium; patrn de frecuencia de haz de cesio An atomic frequency standard that is based on the ground state hyperfine transition in Cs133 atoms. It is a prominent example of a passive frequency standard. calibratio
29、n; talonnage; calibracin The process of identifying and measuring offsets between the indicated value and the value of a reference standard used as the test object to some determined level of uncertainty. NOTE 1 In many cases, e.g. in a frequency generator, the calibration is related to the stabilit
30、y of the device and therefore its result is a function of time and of the measurement averaging time. carrier frequency; frquence porteuse; frecuencia portadora The frequency of a signal upon which information (modulation) is impressed. carrier phase measurements; mesures de phase de la porteuse; me
31、diciones de la fase de la portadora GNSS systems provide two types of direct measurements code based pseudorange and the carrier phase. Due to their low noise, carrier phase measurements can be used for smoothing pseudoranges and in high precision positioning applications. Carrier phase measurements
32、 are ambiguous by an 4 Rec. ITU-R TF.686-3 unknown integer number of cycles presenting a problem that requires additional time and processing to solve. clock; horloge; reloj A device for time measurement and/or time display. clock ensemble; ensemble dhorloge, conjunto de relojes A collection of cloc
33、ks, not necessarily in the same physical location, operated together in a coordinated way either for mutual control of their individual properties or to maximize the performance (time accuracy and frequency stability) and availability of a time-scale derived from the ensemble. clock time difference;
34、 diffrence entre temps dhorloge; diferencia de tiempo de reloj The difference between the readings of two clocks at the same instant. NOTE 1 To avoid confusion in sign, algebraic quantities should be given, applying the following convention. At a time T of a reference time-scale, let a denote the re
35、ading of clock A, and b the reading of clock B. The clock time difference is expressed by A B = a b at the instant T. There is no universally accepted convention for the significance of the sign. If A B is measured electrically, a positive value usually implies that a given tick from clock A arrives
36、 before the corresponding tick from clock B, whereas, the reverse is usually true if A and B are calendar dates read from the two clocks. NOTE 2 In some situations relativistic effects can be significant and must be accounted for. See Recommendation ITU-R TF.2018. coherence of frequency; cohrence de
37、 frquence; coherencia de frecuencia Same as coherence of phase (phase coherence). coherence of phase; cohrence de phase; coherencia de fase See “phase coherence”. common-view (CV) time-transfer; transfert de signaux horaires partir de vues simultanes; transferencia con visin comn (VC) de seales hora
38、rias Allows the direct comparison of two clocks at remote locations. In this technique, two stations, A and B, receive simultaneous one-way signals simultaneously from a single GNSS satellite and measure the time difference between the satellite clock and their own local clock. The time difference b
39、etween clocks A and B is calculated by taking the difference between the simultaneous clock difference measurements, in which any error in the satellite clock is cancelled. In addition, some error sources such as orbit error and ionospheric error that are correlated with link geometry are reduced in
40、 CV time transfer. The CV technique thus performs quite well when the two stations are separated by short distances but the uncertainty gets larger as the distance increases (less cancellation of errors, less common visibility) until the point where common view observation is no longer possible. coo
41、rdinated clock; horloge coordonne; reloj coordinado A clock synchronized within stated limits to a reference clock that is spatially separated. coordinate time; temps-coordonne; tiempo-coordenada The concept of time in a specific coordinate frame, valid over a spatial region with varying gravitation
42、al potential. NOTE 1 TAI is a coordinate time-scale defined in a geocentric reference frame. See International atomic time and terrestrial time. Rec. ITU-R TF.686-3 5 coordinated time-scale; chelle de temps coordonne; escala de tiempo coordinada A time-scale synchronized within stated limits to a re
43、ference time-scale. Coordinated Universal Time (UTC); temps universel coordonn (UTC); Tiempo Universal Coordinado (UTC) The time-scale maintained by the Bureau International des Poids et Mesures (BIPM) and the International Earth Rotation and Reference Systems Service (IERS), which forms the basis o
44、f a coordinated dissemination of standard frequencies and time signals. See Recommendation ITU-R TF.460. It corresponds exactly in rate with TAI, but differs from it by an integer number of seconds. The UTC scale is adjusted by the insertion or deletion of seconds (positive or negative leap seconds)
45、 to ensure approximate agreement with UT1. See “universal time” and Recommendation ITU-R TF.460. date; date; fecha The reading of a specified time-scale, usually a calendar. NOTE 1 The date can be conventionally expressed in years, months, days, hours, minutes, seconds and fractions thereof. discipl
46、ined oscillator; oscillateur asservi; oscilador controlado An oscillator whose output is controlled to agree with signals obtained from a more accurate and/or stable source (e.g. GNSS broadcasts). Doppler shift; dcalage Doppler; desplazamiento Doppler The apparent shift in frequency of an electromag
47、netic signal directly related to the relative speed between a transmitter and a receiver. drift (frequency); drive; deriva See “frequency drift”. DUT1; DUT1; DUT1 The value of the predicted difference UT1 UTC, as disseminated with the time signals. DUT1 may be regarded as a correction to be added to
48、 UTC to obtain a better approximation to UT1. The values of DUT1 are given by the International Earth Rotation and Reference Systems Service (IERS) in multiples of 0.1 s. See “universal time”. Earth rotation angle; angle de rotation de la Terre; ngulo de rotacin de la Tierra A measure of the angle t
49、hrough which the Earth has turned in a given period of time. This angle refers to the angular difference between the 0 meridian on the Earth and an astronomically defined point in space. See UT1. ephemeris time; temps des phmrides; tiempo de efemrides An astronomical time-scale based on the orbital motion of the Earth around the sun. It was used to define the SI second between 1960 and 1967, and continued in use for astronomical applications until 1977 when it was replaced by terrestrial dynamical time (TDT). T
