1、 Copyright 2015 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue, White Plains, NY 10601 (914) 761-1100 Approved September 1, 2015 Table of Contents Page Foreword . 2 Intellectual Property 2 Introduction 2 1 Scope 3 2 Conformance Notation 3 3 Normative References 3 4 Definit
2、ions . 4 5 Common Guidelines for Indicating Device Specifications 5 6 Intrinsic and Output Jitter Measurement . 6 6.1 Oscilloscope Measurement by Means of Triggering on a Reference Signal 6 6.2 Jitter Measurement by Means of a Clock Extractor Reference Method 7 6.3 Jitter Measurement by Means of a D
3、igital Sampling Oscilloscope and a Software (SW) Based Clock Extractor 11 6.4 Phase Noise Measurement by Means of a Clock Extractor . 12 6.5 Jitter Measurement Using a Phase Demodulator . 13 6.6 Phase Demodulator Measurement with an Available Reference Signal 14 6.7 Jitter Measurement with a Bit Err
4、or Ratio Tester (BERT). 15 7 Jitter Tolerance Measurement . 15 8 Jitter Transfer Measurement 16 9 Jitter Measurements on Optical Systems (Informative) 17 Annex A Bibliography (Informative) . 18 Page 1 of 18 pages SMPTE RP 192:2015 Revision of RP 192-2003 SMPTE RECOMMENDED PRACTICE Jitter Measurement
5、 Procedures In Bit-Serial Digital Interfaces SMPTE RP 192:2015 Page 2 of 18 pages Foreword SMPTE (the Society of Motion Picture and Television Engineers) is an internationally-recognized standards developing organization. Headquartered and incorporated in the United States of America, SMPTE has memb
6、ers in over 80 countries on six continents. SMPTEs Engineering Documents, including Standards, Recommended Practices, and Engineering Guidelines, are prepared by SMPTEs Technology Committees. Participation in these Committees is open to all with a bona fide interest in their work. SMPTE cooperates c
7、losely with other standards-developing organizations, including ISO, IEC and ITU. SMPTE Engineering Documents are drafted in accordance with the rules given in its Standards Operations Manual. SMPTE RP 192 was prepared by Technology Committee 32NF. Intellectual Property At the time of publication no
8、 notice had been received by SMPTE claiming patent rights essential to the implementation of this Engineering Document. However, attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. SMPTE shall not be held responsible for identifying a
9、ny or all such patent rights. Introduction This section is entirely informative and does not form an integral part of this Engineering Document. Jitter is one of the most important parameters in the performance of serial digital transmission systems. It can cause errors in the transmission and recov
10、ery of digital data, and may degrade analog signal performance if the jitter is transferred through the digital-to-analog conversion process. Characterizing and measuring jitter are important for reliable and predictable serial digital system operation. SMPTE RP 192:2015 Page 3 of 18 pages 1 Scope T
11、his Recommended Practice describes methods for measuring jitter performance in bit-serial digital interfaces. The techniques are specifically suited for jitter specifications that follow the form described in SMPTE RP 184. 2 Conformance Notation Normative text is text that describes elements of the
12、design that are indispensable or contains the conformance language keywords: “shall“, “should“, or “may“. Informative text is text that is potentially helpful to the user, but not indispensable, and can be removed, changed, or added editorially without affecting interoperability. Informative text do
13、es not contain any conformance keywords. All text in this document is, by default, normative, except: the Introduction, any section explicitly labeled as “Informative“ or individual paragraphs that start with “Note:” The keywords “shall“ and “shall not“ indicate requirements strictly to be followed
14、in order to conform to the document and from which no deviation is permitted. The keywords, “should“ and “should not“ indicate that, among several possibilities, one is recommended as particularly suitable, without mentioning or excluding others; or that a certain course of action is preferred but n
15、ot necessarily required; or that (in the negative form) a certain possibility or course of action is deprecated but not prohibited. The keywords “may“ and “need not“ indicate courses of action permissible within the limits of the document. The keyword “reserved” indicates a provision that is not def
16、ined at this time, shall not be used, and may be defined in the future. The keyword “forbidden” indicates “reserved” and in addition indicates that the provision will never be defined in the future. A conformant implementation according to this document is one that includes all mandatory provisions
17、(“shall“) and, if implemented, all recommended provisions (“should“) as described. A conformant implementation need not implement optional provisions (“may“) and need not implement them as described. Unless otherwise specified, the order of precedence of the types of normative information in this do
18、cument shall be as follows: Normative prose shall be the authoritative definition; Tables shall be next; followed by formal languages; then figures; and then any other language forms. 3 Normative References The following document contains provisions which, through reference in this text, constitute
19、provisions of this recommended practice. At the time of publication, the edition indicated was valid. All documents are subject to revision, and parties to agreements based on this recommended practice are encouraged to investigate the possibility of applying the most recent edition of the document
20、indicated below. SMPTE RP 184:2015, Specification of Jitter in Bit-Serial Digital Systems SMPTE RP 192:2015 Page 4 of 18 pages 4 Definitions 4.1 Alignment jitter Variation in position of a signals transitions relative to those of a clock extracted from that signal. The bandwidth of the clock extract
21、ion process determines the low-frequency limit for alignment jitter. 4.2 BER Acronym for Bit Error Ratio. BER indicates the ratio of errors to total bits received. This is a measure of the integrity of the transmission link. 4.3 Clock extractor A device which is able to extract the serial data clock
22、 from a serial data stream, and outputs a clock-related trigger. It may also provide the serial digital data reclocked with the extracted clock. 4.4 DSO Acronym for digital storage oscilloscope. 4.5 DUT Acronym for device under test. 4.6 Error rate tester A device that quantifies the error rate of a
23、 serial digital signal. Two examples are the classic bit error ratio (BER) tester and the field rate CRC method (EDH) described in SMPTE RP 165. 4.7 Independent Samples For band-limited systems, samples are only independent if they are not over-sampled. By the Nyquist criteria this means that for a
24、given bandwidth in Hz, the maximum number of independent samples per second is approximately twice the bandwidth. Any higher rate of samples will be just giving more information about the same signal components. 4.8 Input jitter tolerance Peak-to-peak amplitude of sinusoidal jitter that, when applie
25、d to an equipment input, causes a specified degradation of error performance. 4.9 Intrinsic jitter Jitter at an equipment output in the absence of input jitter. 4.10 Jitter Variation of a digital signals transitions from their ideal positions in time. 4.11 Jitter generator A device that produces a s
26、erial digital signal containing sinusoidal jitter of adjustable amplitude and frequency. SMPTE RP 192:2015 Page 5 of 18 pages 4.12 Jitter receiver Demodulates and allows measurement of the jitter present on a serial signal. It commonly provides an output proportional to the demodulated jitter. 4.13
27、Jitter transfer Jitter on the output of equipment resulting from applied input jitter. 4.14 Jitter transfer function Ratio of the output jitter to the applied input jitter as a function of frequency. 4.15 Output jitter Jitter at the output of equipment that is embedded in a system network. It consis
28、ts of intrinsic jitter and the jitter transfer of jitter at the equipment input. 4.16 Phase demodulator A device that provides as its output a signal proportional to the phase difference of two input signals. 4.17 Probabilistic Peak-to-Peak Jitter (p-p-p, Stated as Jitter at 1 in 10x) This is an est
29、imate of the most likely p-p jitter in unit intervals when measured over 10x independent jitter samples. See SMPTE RP 184 for derivation. 4.18 SDI Acronym for Serial Digital Interface. 4.19 Timing jitter Variation in position of a signals transitions occurring at a rate greater than a specified freq
30、uency, typically 10 Hz or less. Variations occurring below this specified frequency are termed wander and are not addressed by this practice. 4.20 Unit interval (UI) Abbreviated “UI“, it is the period of one clock cycle. It corresponds to the nominal minimum time between transitions of the serial si
31、gnal. 5 Common Guidelines for Indicating Device Specifications For all the measurement types and methods in this Recommended Practice, the following guidelines should be observed for optimal results: 1) All high-speed signals, especially SDI signals, shall be terminated in the appropriate impedance.
32、 For SDI signals this means to terminate in 75 ohms with return loss that meets the relevant SMPTE specification. 2) All SDI measurement inputs shall have sufficient bandwidth to prevent a significant degradation in the signal. For the time domain methods, the measuring device shall cause no more th
33、an a 20% increase in the risetime relative to a measurement with unlimited bandwidth. For frequency domain methods the measuring device shall be able to display signals up to the serial rate plus the jitter frequency limit f4 in order to observe the jitter sidebands. SMPTE RP 192:2015 Page 6 of 18 p
34、ages 3) For the time-domain methods, the horizontal and/or trigger bandwidth of the indicating device shall not attenuate the observed jitter. The trigger bandwidth shall be at least f3. 4) For the time-domain methods, the indicating device shall not create inter-symbol interference at the zero-cros
35、sing point. This requires a vertical system step response that transitions and settles in less than 1 UI. 5) The indicating device shall acquire sufficient samples so that peak-to-peak jitter can be determined. This requires sampling until the shape of the jitter distribution is known. If the jitter
36、 specification includes a measurement time, this shall be the minimum acquisition time. The maximum acquisition time will depend on the device sample rate and the type of jitter distribution. For example, a sinusoidal distribution will typically be determined with fewer samples than will a Gaussian-
37、like distribution. If the jitter specification includes a sample size or probability at which the jitter must be satisfied then the indicating device shall collect samples to meet those specifications. If a probability is specified then the indicating device shall indicate if the jitter measurement
38、at that probability is directly measured or extrapolated from a smaller sample set. 6) The minimum measurement time “tm” shall be as specified in SMPTE RP 184. Depending on the type of indicating device, the actual measurement time may be significantly longer than the minimum in order to collect req
39、uired number of samples or p-p-p threshold. 7) If the indicating device is an oscilloscope, the jitter measurement is usually made at the eye crossing. A digital storage oscilloscope with infinite persistence is recommended. 6 Intrinsic and Output Jitter Measurement Seven methods are described and e
40、ach of these methods has advantages and disadvantages. The particular characteristics of each method are discussed in the individual sections. The implementer can choose the method which is most appropriate for a particular application. The method described in Section 6.2 is considered the preferred
41、 reference method. The first of the seven methods uses an available reference clock to trigger an oscilloscope; the second and third use a clock extractor with defined characteristics to trigger the oscilloscope; the fourth uses a spectrum analyzer; the fifth and sixth are based on a phase demodulat
42、or method jitter receiver; the seventh method uses a clock extractor and a Bit Error Ratio Tester (BERT). 6.1 Oscilloscope Measurement by Means of Triggering on a Reference Signal If a reference signal is available, a basic jitter measurement can be done (see Figure 1). The oscilloscope is directly
43、triggered by the reference signal. This reference signal could also be a serial digital signal with high stability. The digital data signal is connected to the suitably terminated vertical channel of the oscilloscope and an eye measurement is done. The jitter is typically measured at the eye crossin
44、g. Presentation of measurement results: The test signal, the jitter amplitude, the parameters of the oscilloscope (bandwidth, etc.), and the measurement time should be indicated. Background information: This measurement procedure provides a coarse survey of jitter in an SDI signal. The measurement r
45、esult depends on the stability of the reference signal (its jitter sets the measurement floor), the type of oscilloscope, and the measurement time (e.g., when a DSO is used in persistence mode). All of these parameters influence the measurement result and contribute to variability in the result as c
46、onditions vary. This method does not allow bandwidth restriction as generally required in jitter specification. This method is not recommended if other jitter measurement methods are available. The frequency of the reference should not be closely related to the word rate. This will avoid masking wor
47、d rate jitter. For example, the reference frequency should not be the serial rate divided by 10 or 20. SMPTE RP 192:2015 Page 7 of 18 pages Figure 1 Jitter measurement by means of an external reference signal 6.2 Jitter Measurement by Means of a Clock Extractor Reference Method The jitter in a signa
48、l output can be measured by using a device to extract a clock and then trigger an oscilloscope or other indicating device. The exact connection necessary depends on the amount of jitter in the signal to be measured. Whenever possible, the connection in Figure 2 should be used. If the jitter is great
49、er than 1 UI, then the connection of Figure 2 no longer works, so the connection in Figure 5 is recommended. With the Figure 5 connection, the upper bandwidth of the jitter measurement is typically limited to less than the f4 value. These methods are explained in detail in Section 6.2.1 for timing jitter and Section 6.2.2 for alignment jitter. SMPTE RP 192:2015 Page 8 of 18 pages Seri al Source Cl ock Ex tr actor Ve rt ica l Ch ann el T ri gg er E xtrac ted Clock Passive L oo p - throu gh or Power Split te r Figure 2 J itt e r me as
