1、STD-CEPT CEPT/ERC/REC 54-01 E-ENGL 1948 232b4L4 OOL3YL2 OBT m CEPT/ERCREC 54-01 E Page 1 Distribution: B CEPT/ERC Recommendation ERC 54-01 E (Funchal 1998) METHOD OF MEASURING THE MAXIMUM FREQUENCY DEVIATION OF FM BROADCAST EMISSIONS IN THE BAND 87.5 MHz TO 108 MHz AT MONITORING STATIONS Recommendat
2、ion adopted by the Working Group Frequency Management (WGFM) INTRODUCTION The purpose of this Recommendation is to provide a common measurement method which will enable CEPT administrations to recognise measurement results relating to the frequency deviation of FM broadcast emissions on a mutual bas
3、is. “The European Conference of Postal and Telecommunications Administrations, considering that frequencies in the VHF band 87.5 - 108 MHz are assigned to an increasing number of FM broadcasting stations; that protection ratios for the planning of broadcasting transmitter frequencies are based on a
4、maximum frequency deviation of k75 kHz and a maximum power of the modulation signal which does not exceed the power of a sinusoidal tone which causes a k19 kHz frequency deviation; that various broadcast transmissions exceed the maximum frequency deviation owing to different types of programmes and
5、additional components of the composite signal (e.g. radio data system (RDS); that limitation of the peak frequency deviation is required to guarantee mutual protection of broadcast services (on adjacent channels); that monitoring of broadcast emissions is necessary to prevent transmissions from exce
6、eding the maximum frequency deviation; that common measurement procedures are necessary in order to achieve mutual acceptance of measurement results by the parties concerned, e.g. frequency managers, monitoring services and broadcasters; that the number of broadcasting stations using additional sign
7、als as RDS and high speed data signals is increasing and these systems are highly sensitive to interference from adjacent channels, recogn ising a) that the method described in Annex 1 is a simple “go - no go“ test based on a spectrum mask which cannot replace precise measurements of the frequency d
8、eviation, recommends 1 that the method described in Annex 1 may be used as a verification to indicate whether the frequency deviation of an FM broadcasting station exceeds the limits; 2 that the method described in Annex 2 is used when the values of the deviation and modulation power are required. S
9、TDmCEPT CEPT/ERC/REC 1 2 3 4 5 54-01 E-ENGL 1998 9 2326434 0013413 T1b 9 CEPT/ERC/REC 54-01 E Page 1 Annex 1 Annex 1 SIMPLE SPECTRUM MASK BASED METHOD TO INDICATE THE EXCEEDING OF FREQUENCY DEVIATION LIMITS REQUIREMENTS For this measurement any suitable spectrum analyser or test receiver with analys
10、er capabilities can be used. CONNECTION BETWEEN TRANSMITTER AND SPECTRUM ANALYSER With the aid of a measurement antenna. MEASUREMENT CONDITIONS a) During three measurements of five minutes each, the transmitter to be judged should be modulated with a representative programme material for that partic
11、ular transmitter. Additional measurements may be carried out to ensure that the programme material is truly representative; b) impulse interferences should not occur (for example interference from an ignition source); c) signal/interference+noise should be 250 dB. ADJUSTMENTS OF THE SPECTRUM ANALYSE
12、R The spectrum analyser should be adjusted as follows: - Centre frequency = f, (Carrier frequency of the transmitter) - RBW 10 kHz (IF filter) - VBW 10 kHz (Video filter) - Span 340 kHz - Sweeptime 340 ms (ImskHz) - max hold mode - Input attenuation is dependent on input level. Settings for DSP (dig
13、ital signal processor) analysers will be different but should provide equivalent results. MEASUREMENT INSTRUCTIONS a) Record the transmitter signal over a five minutes period; b) Observation of the analyser and acoustic controls at the receiver should be used as a means to ensure that no measurement
14、 results are evaluated which have been distorted by impulse interference. For the same reason the measurement is repeated twice; c Overlay the graphical measurement with the mask as described in paragraph 7; d) The centre of the x-axis of the mask shall correspond with the centre frequency (fo); e)
15、Adjust the reference level so that the maximum amplitude of the measurement corresponds to O dB; f) Determine whether the measurement is within the limits of the mask. CEPTERCREC 54-01 E Page 2 Annex 1 6 LIMITS If any of the measured spectra exceeds the mask the deviation of the transmitter is assum
16、ed not to meet the requirements. 7 MASK CONSTRUCTION a) The calibration of the mask should be consistent with the analyser settings; b) The centre of the X-axis is aligned to fo; c) The top of the Y-axis corresponds with the O dB reference level; 4 Straight lines connect the Co-ordinates: x-axis Y-a
17、xis fo- 74 fo- 107.5 fo- 124 -30 fo- 152.5 -40 The graphic display of the table is shown below. I X-axis I Y-axis I (kH4 fo+ 74 fo+ 107.5 fo+ 124 ffi+ 152.5 Shape of the Mask B (relative to peak) O -5 -10 -1 5 -20 -25 -30 -35 -40 -45 -152.5 -124 -07.5 -74 +74 +107.5 +I24 +52.5 frequency separation f
18、rom carrier (kHz1 STD=CEPT CEPT/ERC/REC 54-01 E-ENGL 1998 2326434 00334115 897 CEPT/ERC/REC 5461 E Page 1 Annex 2 Annex 2 METHOD OF MEASURING THE MAXIMUM FREQUENCY DEVIATION OF FM BROADCAST EMISSIONS AT MONITORING STATIONS 1 GENERAL 1.1 Definitions Frequency deviation: in the case of frequency modul
19、ation, the deviation of the frequency from the frequency of the unmodulated carrier fo. Instantaneous deviation: In the case of frequency modulation, the instantaneous deviation Af(t) is t difference between the unmodulated carrier frequency (fo) and the instantane frequency at any given time (t). T
20、he instantaneous frequency is: f(t) = fo + Af(t). Peak deviation: Composite signal: Modulation power: O dBr: In the case of frequency modulation, the peak deviation AF is the absolute maximum of the difference between the unmodulated carrier frequency (fo) and the instantaneous frequency f(t). In th
21、e case of frequency modulation with sinusoidal signals. The instantaneous frequency is: f(t) = fo + AF*sin(wt). This signal includes all stereo information (including the pilot tone) and may also include the traffic radio signal, the RDS signal and other additional signals. The relative power averag
22、ed over 60 s of the modulation signal according to the formula: modulation power = 10 log (2160 s) !(Af(t)/l9 kHz)* dt dBr is the average power of a signal equivalent to the power of a sinusoidal tone which causes a peak deviation of *19 kHz. 1.2 Introduction There are various reasons, such as a red
23、uction in the time required for the measurements, which make it seem sensible to carry out frequency deviation measurements in the field and not directly at the transmitter output. Compliance by the signal to be measured with the characteristics listed below is required in addition to compliance by
24、the measuring equipment with the requirements described in paragraph 3 in order to avoid measurement uncertainties. 1.3 Limits The protection ratios specified in Recommendation ITU-R BS.412 for the planning of FM sound broadcasting transmitters apply on the condition that a peak deviation of 3=75 kH
25、z is not exceeded and that the average modulation power over any interval of 60 s does not exceed that of a single sinusoidal tone which causes a peak deviation of *19 kHz. 1.4 Observation time The measurement should represent typical modulation of the programme material of the broadcasting station.
26、 The observation time should be at least 15 minutes or in some cases one hour may be required to be sure to measure representative programme material. STD.CEPT CEPTIERCIREC 54-01 E-ENGL 1998 W 2326434 OOL341b 725 CEPTIERCIREC 54-01 E Page 2 Annex 2 2 REQUIRED CONDITIONS FOR MEASUREMENTS 2.1 Required
27、 wanted-to-unwanted RF signal level ratio EJE, at the measurement equipment This ratio depends on the characteristics of the equipment used for the measurements and on the required accuracy. The measurement equipment shall have a sufficient IF bandwidth to enable the measurement of frequency deviati
28、on according to the requirements given in Section 3. In the case of equipment which meets the “Characteristics of FM sound broadcasting receivers for planning purposes“ as specified in Recommendation ITU-R BS.704, the EnEs ratio given in Recommendation ITU-R BS.412, Figure 1, Curve SI is considered
29、to be sufficient for these measurements and for frequency separations 2200 kHz. Owing to the necessary IF bandwidth and the required accuracy, the EJE, for Co-channel and adjacent channel interference shall be at least 15 dB above the given values. 2.2 Multipath propagation Delayed signals shall be
30、small enough to ensure that measurement results are not influenced by the effects of multipath propagation. It is considered to be sufficient if the product of delay time and amplitude ratio is: where U, is the amplitude of the reflected signal; Ud is the amplitude of the direct signal; T is the tim
31、e delay. This product is proportional to the maximum gradient of the dependence of RF amplitude on RF frequency caused by multipath propagation which is easily measurable (even when there is more than one delayed signal). The corresponding gradient for stereophonic reception is: 2.3 Wanted signal le
32、vel at the receiver input To ensure a sufficient AF signal-to-noise ratio, the wanted signal input level for the receiver should be at least 43 dBpW.* 3 CHARACTERISTICS OF SUITABLE MEASURING EQUIPMENT To ensure that all the peaks of the frequency deviations are captured, the equipment must be able t
33、o detect the deviation caused by the highest component of the base band signal or composite signal, For this reason, if digital measuring equipment is used, it must have a sampling rate of 200 kHz or higher depending on the maximum composite signal frequency. 3.1 Frequency deviation measurements The
34、 measuring equipment used should be able to measure deviations of 100 kHz or higher. In addition the measuring equipment must possess such characteristics that take into account the required measurement bandwidth, filter shape factor, etc. to ensure that nonlinearity and distortion do not lead to an
35、 inaccuracy greater than specified in Table 1. * This corresponds to a field strength of about 68 dBpV/m using an antenna as recommended in Recommendation ITU-R 83.599, Figure 1, Curve B (12 dB front-to-back ratio). CEPTIERCIREC 54-01 E Page 3 Annex 2 Modulation power 3 dRr TABLE 1 required accuracy
36、 *0.4 dB *0.2 dB M.4 dB Instrument accuracy for deviation measurements I Instantaneous deviation I required accuracy 1 IS0 kHz i h2kHz SO kHz l*5% 3.2 Modulation power measurements The modulation power is specified in dBr according to Section 1.1. The measuring equipment shall be able to measure mod
37、ulation power in the range from -6 dBr to +6 dBr. The instrument accuracy shall at least meet the values specified in Table 2. TABLE 2 Instrument accuracv for modulation Dower measurements 4 PRESENTATION OF MEASUREMENT RESULTS 4.1 Modulation power The modulation power shall be presented as a functio
38、n of time during the measurement interval. 4.2 Frequency deviation To provide more information the deviation is better represented by histograms and as a function of time rather than only displaying the highest value in a “Max Hold“ mode over a certain period of time. Histograms of frequency deviati
39、on are processed as follows: a) Obtain N peak hold values of the deviation each taken during a measuring time of 50ms. The measuring time has influence on the distribution plot and hence must be standardised in order to ensure repeatability. The 50 ms ensures that the peak values of the deviation ar
40、e captured even at modulating frequencies as low as 20 Hz; b) Divide the range of frequency deviation of interest (Le. 150 kHz) into the desired resolution (for example 1 kHz) to give the number of bins (in this case 150 bins); c) For each bin, count the number of samples which have a value within t
41、he bin. The result is a distribution plot of the deviation as shown in Figure 1; d) Add counts in each bin from left to right and normalise by N. The result is a plot of the accumulated distribution as shown in Figure 2 which starts with a probability of 100% from the left side and will finish with
42、a probability of 0% at the right side; e) Additionally the N peak hold values of the frequency deviation shall be presented as a function of time during the measurement interval. CEPTERCIREC 5401 E Page 4 Annex 2 FIGURE 1 Distribution plot of deviation l 400 c Em - I - LI k “c, 1 1 1 oc A dp O 10 20 SO 40 50 60 70 80 W 100 110 120 I50 140 IS0 deviation 0-150 kHz 150 ciilea FIGURE 2 Accumulated distribution plot of deviation 10 30 -. - - 40 50 -T-r-ri 7 I I I I I I 7 22 % 75 kHz 12 % z 80 kHz 8% 85kHz 60 70 80 90 100 110 120 130 i40 is0
