1、 STD-ITU-R RECMN bOO-1-ENGL L78b q55212 0528775 IT4 m Rec. 600-1 1 SECTION 10/11S-D: PLANNING AND SHARING RECOMMENDATION 600-1 STANDARDIZED SET OF TEST CONDITIONS AND MEASUREMENT PROCEDURES FOR THE SUBJECTIVE AND OBJECTIVE DETERMINATION OF PROTECTION RATIOS FOR TELEVISION IN THE TERRESTRIAL BROADCAS
2、TING AND THE BROADCASTING-SATELLITE SERVICES (Question 1/10 and 11, Study Programmes 1AlO and 11, 1C/10 and 11, 1D/10 and 11) (1982-1986) The CCIR, CONSIDERING that several experiments have been carried out for the determination of protection ratios for television; that some of these experiments hav
3、e been carried out using different test conditions and measurement (a) (b) procedures, so that the results cannot be readily interpreted and compared; (4 that the values of subjectively measured protection ratios depend on a large number of factors; (4 that it is desirable to establish a standardize
4、d set of test conditions and measurement procedures in order that the results of subjective measurements of protection ratios for television made by different administrations may be properly interpreted and applied, UNANIMOUSLY RECOMMENDS that the following set of test conditions and measurement pro
5、cedures described in Annex I should be used for the subjective and objective determination of protection ratios for television, whenever possible. ANNEX I 1. Introduction The protection ratio is the minimum value of the wanted-to-unwanted signal ratio, usually expressed in decibels, at the receiver
6、input determined under specified conditions such that a specified reception quality of the wanted signal is achieved at the receiver output (Note 1). The protection ratio is useful in planning and operations where multiple transmissions require frequency and orbit sharing between similar or dissimil
7、ar transmissions. Protection ratios for monochrome television systems and for colour television systems using vestigial sideband amplitude-modulation are found in Recommendation 655. For satellite broadcasting, a summary of results of protection ratio tests made by several administrations in cases w
8、here the wanted and unwanted signals are modulated by colour television signals or other transmissions such as multiple sound channels are found in Report 634 (see Note 2). The assessment of protection ratios for television signals is made following the method established in Recommendation 500 and t
9、aking into consideration Report 405. Procedures can entail absolute or comparative methods of assessment depending on the specific investigations being carried out. The test arrangements and measurement procedures presented next are recommended for use in tests for the determination of protection ra
10、tios for television CCIR, 1978-82a and b. Note 1 - This definition is in line with the definition of protection ratio found in Report 625 and in No. 164 of the Radio Regulations. Note 2 - Protection ratio data for interference between an amplitude-modulation, vestigial-sideband or a frequency- modul
11、ation television signal and the types of signals used in the fixed and mobile services will be found in Report 449. 2. 2.1 Reference case conditions Measurement procedure and laboratory assessment of protection ratios The values of subjectively measured protection ratios depend on a number of factor
12、s. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services- STDDITU-R RECMN bOO-L-ENGL 198b 4855212 052899b O30 W 2 Rec. 600-1 In order to allow that the results of subjective measurements of the protection ratio made by different administrat
13、ions may be properly interpreted and applied, tests should be performed under a set of reference case conditions for the factors affecting these subjective measurements (see Table I). COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services ST
14、D-ITU-R RECMN bOO-L-ENGL 178b i855212 0528777 T77 = Rec. 600-1 3 TABLE I - Factors affecting subjectively measuredprotection ratios and a set of reference case conditions for these factors Factor icture impairment assessment scale Number of levels Definition of levels (perceptibility, annoyance, qua
15、lity) Fraction of time interference effects are visible Impairment level for tests iewers Number Expertise !eceivers Number and types Performance parameters (selectivity, sensitivity, overload characteristics, etc.) liewing conditions Distance to screen Brightness of picture Brightness of background
16、 Vantecl signal characteristics Colour or monochrome Television standard (M, G, I, L, . . .) Colour system (NTSC, PAL, SECAM, . . .) Accompanying sound Line synchronization Picture type (still, moving) and content Amount of detail in picture Type of modulation (AMNSB, FM, digital) Modulation index P
17、re-emphasis characteristics for FM Energy dispersal characteristics Fading Unwanted signal characteristics Carrier frequency offset Frequency of operation Video signal-to-noise ratios Receiver noise Man-made noise Picture source noise %her interferences and sources of picture degradation Other inter
18、fering signals Multipath Receiver distortion Reference case condition Terrestrial (See Rec. 500) 5 Impairment Continuous Note 14 (See Rec. 500) 10-20 minimum Note 1 Note 2a (See Rec. 500) Note 3 Variable Variable Note 4a Note 5 Note 6 Note 6 Variable, Note 7 - - - Nil Note 9 Note 14 Note 11 Note 12
19、Note 13 Satellite (See Rec. 500) 5 Impairment Continuous 4.5 (See Rec. 500) 10-20 minimum Note 1 Note 2b (See Rec. 500) Note 3 Variable Variable Note 4b Note 5 Note 6 Note 6 Variable, Note 7 Note 8 Rec. 405 Nil Nil Note 9 Note 10 Note Note 1 2 Note 13 Note 1 - Both expert and non-expert viewers may
20、be used. Tests with non-expert viewers are representative of the general population but tend to be quite lengthy. A great number of variables can be examined by using a small group of expert viewers. For the particular interference being examined, the relationship between expert and non-expert opini
21、on should be investigated. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTD-ITU-R RECMN bUO-L-ENGL 178b = Li855212 0528778 903 4 Rec. 600-1 Note 2a - The receivers used in the test should represent equipment which is fairly sensitiv
22、e to the type of impairment being investigated. Full account should be taken of the performance of domestic receivers, and measurements of the RFIIF response characteristics should be made to assist in the interpretation of the results. Account should also be taken of the type of receiver which may
23、be used at re-broadcast relay stations. Note 2b -The receivers used in the test should represent equipment which is fairly sensitive to the particular type of impairment being investigated. Account should be taken of domestic receivers, and the type of receivers which may be used at re-broadcast rel
24、ay stations. It is important to indicate the type of discriminator used (staggered-circuit or phase-locked loop) as well as the bandwidth characteristics of the receiver (IF filter characteristics or equivalent characteristics in the case of a loop discriminator). Measurement of RF and IF filter cha
25、racteristics should be made to assist in the interpretation of the results obtained when there are frequency offsets between the wanted and unwanted signals. As far as possible, filter characteristics should be adjusted to the standards applicable to the wanted signal. Baseband output frequencies sh
26、ould be limited to the minimum required for the television standard used for the wanted signal. Excessive filter bandwidths permit the observation of noise and interferences that would not be encountered with properly adjusted receivers. Note 3 - Subjective tests should be based on colour pictures,
27、unless there is reason to suppose that monochrome pictures would result in more stringent requirements. Note 4a - If applicable standards exist for the accompanying sound channel(s), those standards should be used and the modulation characteristics noted, If no existing standards are applicable, ful
28、l details of the characteristics of any sound signal(s) present should be given. Note 46 - If applicable standards exist for the accompanying sound channel(s), those standards should be used and the main carrier deviation caused by the sound sub-carrier(s) should be noted. If no standards exist one
29、should additionally indicate the sound sub- carrier frequency(ies) and the deviation of the sound sub-carrier(s). Note 5 - The timing of the vertical and horizontal synchronization of the unwanted television signal should be such that when interference is visible, the interfering vertical and horizo
30、ntal synchronizing bars are near the centre of the wanted picture. 4 The synchronizing signal of the wanted signal should be locked to the synchronizing signal of the unwanted signal, but with fields displaced so that sync bars from the unwanted signal are visible as interference on the wanted pictu
31、re. Greatly different sync frequencies cause flicker in the picture and produce subjectively more noticeable interference. Note 6 - The test pictures used should be reasonably critical still pictures, as they may occur fairly frequently in practice. The scenes should contain bright, saturated colour
32、s. Slides suggested for tests are described in 0 2.2. Colour bar modulation is often used as the unwanted signal. Note 7 - If applicable standards exist for the characteristics of either the wanted or unwanted signals, those standards should be used. If no standards exist, as for a frequency-modulat
33、ion television signal for broadcasting, then the succeeding entries in Table I should be used. The sense of modulation should be such that a black-to-white transition corresponds to an increase in the instantaneous frequency. Note 8 - A peak-to-peak frequency deviation sensitivity of 12 MHfl should
34、be used, if applicable. When other values are used, the peak-to-peak deviation should be indicated. Note 9 - In most cases the unwanted signal has the same characteristics as the wanted signal. There is, however, also a need for the determination of protection ratios between dissimilar systems. In t
35、hese cases the unwanted signal can have characteristics different from the wanted signal or can be another type of transmission such as multiple sound channels. Note 10 - For co-channel protection ratio measurements there is no carrier frequency offset: carrier frequency offset is defined as the dif
36、ference between the unmodulated carrier frequencies of the unwanted and wanted signals, -fu,wa,ted), if the same type of modulator is used in both channels. However, if the interference is sensitive to particular offset frequencies, these should be identified by the testing programme. For adjacent-c
37、hannel protection ratios, a series of measurements should be made for frequencies of the unwanted signal varying approximately I30 MHz from the wanted signal. Note 11 - Tests may be conducted at either radio - or intermediate - frequencies. Protection ratios between wanted and unwanted signals are a
38、ffected by the types of signal, their frequency separations, and other factors which do not depend on the frequency range used. Note 12 -As far as possible, the only noise which should be present on the picture when assessing protection ratios is that of thermal noise in the receiver. The protection
39、 ratios should be measured for pictures having a signal-to-unweighted-noise ratio of not less than 36 dB, in order that system performance should not be limited by possible masking of interference by noise. Note 13 - No account should be taken of other sources of interference, etc. (except thermal n
40、oise, as mentioned above), when assessing the protection ratio. Note 14 - For 625-line systems, the reference impairment levels are those which correspond to wanted-to-unwanted signal-to-noise ratios of 30 dB and 40 dB with a frequency offset between vision carriers of two-thirds of the line frequen
41、cy but adjusted within a plus and minus 25 Hz range to produce maximum impairment, the precise frequency difference being 10.416 kHz. These conditions are approximate to mean impairment grades 3 and 4 and are respectively applicable to short-term (tropospheric) and continuous interference. COPYRIGHT
42、 International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTD-ITU-R RECMN bOO-L-ENGL L78b 4855232 0528777 BqT W Rec. 600-1 5 2.2 Test pictures The test pictures used (see Recommendation 500) should be chosen from a set available to all administrations, s
43、o as to allow comparisons of results. Not only is the subjective evaluation of the interference dependent upon the test picture, but also the amount of baseband interference is dependent upon the modulated spectral densities of both signals, and the spectral densities depend on the video content. Te
44、st slides generally available are those of the Society of Motion Picture and Television Engineers (SMPTE) subjective colour reference slide series and the Philips test slides for colour television. The test slides from the SMPTE series are selected stills from the SMPTE reference test film. Two slid
45、es from each series are recommended for the wanted signal during tests on the impairments caused by interference. These are: I. SMPTE II. PHILIPS Colour television test slides Slides Cat. TV CS-3 No. 1 Beachscene No. 14Girl in green dress Colour television test slides No. 8 Basket of fruit No.14 Mak
46、e-up scene The means used to provide the television picture signal (which might include the use of a frame-store synchronizer or similar technique) should ensure that the picture displayed in the absence of interference is of high quality; in particular any impairment should be insignificant compare
47、d with the grade of impairment used for determining the protection ratio. 2.3 Other conditions In performing television protection ratio measurements, highest priority should be given to tests at the “reference case” conditions given in 0 2.1. If other test conditions and parameters must be used, th
48、ey should be defined and correction factors given so that results applicable to the reference test conditions may be deduced. When the use of a video tape recorder will not add to the interference present or will not diminish or mask those interferences, and where the experiment design allows repeti
49、tive signals and sequences, it is recommended that presentations to viewers be made from video tapes. The use of video tape permits presentation to large numbers of viewers with comparative ease, guarantees duplication of test conditions and accompanying commentary, and permits post-test verification of the conditions shown. For protection ratio measurements, interference should be evaluated on the five grade impairment scale given in Recommendation 500 using the viewing conditions and presentation in 0 2.4 and 2.5 of that Recommendation. Wherever possible, informat
