1、BRITISH STANDARD Methods of measurement for radio transmitters - Part 15: Amplitude-modulated transmitters for sound broadcasting The European Standard EN 60244-152000 has the status of a British Standard IS EN i0244-15:2000 EC i0244-15:1999 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY C
2、OPYRIGHT LAW STD.BSI BS EN b0244-15-ENGL 2000 m 1624bb 0847459 643 direction of the Electrotechnical bd. No. Se tor Cornmittee, was published under the authonty of the Standards Committee and comes intn effect on 15 May LOO0 BS EN 60244-152000 Date Comments National foreword This British Standard is
3、 the official English language version of EN 60244-15:2OOO. It is identical with IEC 60244-15:1999. The UK participation in its preparation was entrusted to Technical Committee EPIJ103, lkmsmitting equipment for radiocommunication, which has the responsibility to: - aid enquirers to understand the t
4、ext; - present to the responsible intniational/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; - monitor related international and European developments and promulgate them in the UK A list of organizations represented on this comm
5、ittee can be obtained on request to its secretary. From 1 January 1997, all IEC publications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during the change over from one numbering system to the other, publications may
6、contain identifiers from both systems. Cross-references Attention is drawn to the fact that CEN and CENELEC Standards normally include an annex which lists normative references to international publications with their corresponding European publications. The British Standards which implement interna
7、tional or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “Intemational Standards Correspondence Index“, or by using the “Find“ facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include
8、 all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN t
9、itle page, pages 2 to 27 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. ISBN O 580 34693 5 STD-BSI BS EN b0244- 1,5:1 at frequencies of any measured unwanted frequency up to ten times the highest frequency of the designated broadcas
10、ting band. If the transmitter includes filters at the audiofrequency input to control the audiofrequency band transmitted, all characteristics shall be measured with the filters in circuit. O BSI 05-2000 STD-BSI BS EN 60244-15-ENGL 2000 Lb24669 0847465 947 = Page 6 EN 60244-15:2000 5 General conditi
11、ons of measurement 5.1 Input and output measurement arrangements For the purposes of measurement, the input and output signal arrangements are given in the form of diagrams. Where required, the impedance of the test equipment, of the transmitter under test and of all the connections between them sha
12、ll be appropriately matched. 5.2 Measuring equipment At the input: - the modulating signals for the transmitter under test shall be provided by one or two low- distortion low-frequency test signal generators covering frequencies up to 1 O kHz, or an ITU-R coloured noise generator; - if required, aux
13、iliary equipment for supplementary signals shall be used. At the output: the following measuring instruments may be used. a) For measurements within the radiofrequency domain: - RF oscilloscope; - RF spectrum analyser; - RF phase meter. b) For measurements within the audiofrequency domain using: - t
14、est demodulator; For SSB transmitters, synchronous detection shall be used. For DSB transmitters synchronous or envelope detection can be used. - AF spectrum analyser; - AF distortion meter NOTE 1 Because the results of the measurements are critically dependent on the performance of the test equipme
15、nt, it is desirable to check the test arrangement first by making measurements without the transmitter in circuit. NOTE 2 RF measurements carried out by an RF analyser may differ from those obtained by measuring at the output of an envelope detector, as the influence of the carrier phase variation d
16、ue to the modulation signal is not compensated for. The analyser cannot discriminate between amplitude and phase modulation sideband components located on the same sideband frequencies. 5.3 Modulation and output power conditions The modulation signal or signals for each measurement are stated in the
17、 clauses describing the method of measurement. The output power of the transmitter is dependent on the modulating signal(s) and on the transmission mode. The appropriate reference power level shall be used in accordance with ITU-R Recommendation 326. O BSI 05-2000 STD.BSI BS EN L0244-15-ENGL 2000 I
18、Lb24669 0847466 883 Page 7 EN 60244-15:2000 6 General characteristics The methods of measurement for the general characteristics of transmitters such as input impedance, output power and frequency stability are described in IEC 60244-1. Specific aspects related to the output power of AM sound broadc
19、asting transmitters are described in 6.1 to 6.3. 6.1 Rated output power 6.1 .I Introduction The output power capability of a transmitter is given by its rated output power 6.2 DSB output power 6.2.1 Definition The rated output power of an amplitude-modulated DSB transmitter is defined by the level o
20、f its carrier power, when unmodulated (see figure 5). The rated power of a DCC transmitter is defined by its maximum carrier power level. The power levels at the RF output of a DSB transmitter are as follows. a) Without modulation: b) With full modulation: carrier power P, (rated power). Mean power
21、P, = 1,5 P,; Peak envelope power PEP = 4 P,. 6.2.2 Measuring arrangement Measuring arrangement A (see figure 1) shall be used with one test signal generator at the input. The test load measures the mean RF power. 6.2.3 Measuring procedure - Adjust the output of the unmodulated transmitter to its rat
22、ed power. - Establish a reference line on the oscilloscope - Modulate the transmitter with an 800 Hz or 1 O00 Hz audio signal to full modulation so that the peak envelope amplitude on the RF oscilloscope is twice the carrier reference amplitude. Note the voltage of the audio signal for the transmitt
23、er under test as the reference value for full modulation. - 6.2.4 Calculation and presentation of results The results may be presented as a table stating the rated output power of the transmitter and detailing the power levels measured, together with the modulating frequency used. 0 BSI 05-2000 STD-
24、BSI BS EN b02Qt-LS-ENGL 2000 E 3b24bb9 08474b7 7LT = Page 8 EN 60244-15:2000 6.3 SSB output power 6.3.1 Definition The rated output power of an SSB transmitter with reduced carrier is defined by the level of its peak envelope power when fully modulated. SSB transmitters for HF broadcasting are opera
25、ted with reduced carrier. The peak envelope power level of a fully modulated SSB transmitter depends on the degree of carrier reduction. In accordance with the decisions taken at WARC-79 and WARC-92, the degree of carrier reduction is 6 dB during a transition period of 20 years from 1987, and 12 dB
26、after that period (see figure 6). The power levels at the RF output of an SSB transmitter working with full modulation are as follows. a) With carrier reduction of 6 dB: peak envelope power PEP (rated power) carrier power Pc = 0,25 PEP mean power P, = 0,5 PEP b) With carrier reduction of 12 dB: peak
27、 envelope power PEP (rated power) carrier power Pc = 0,063 PEP mean power P, = 0,625 PEP FIOTE In accordancs with ITU-R Recommendation 640 concerning SSB transmission for broadcasting, the unwanted (lower) sideband and the intermodulation products in that part of the transmitter spectrum have to be
28、suppressed. The current level of suppression recommended by ITU-R is at least 35 dB and, wherever possible, greater than 40 dB, relative to the wanted sideband level. 6.3.2 Measuring arrangement Measuring arrangement A (see figure 1) shall be used with one test signal generator at the input. The tes
29、t load measures the mean RF power. 6.3.3 Measuring procedure - Adjust the output power of the unmodulated transmitter as follows. a) for an SSB transmitter with 6 dB carrier reduction: 0,25 times its rated power (peak envelope power for full modulation). b) for an SSB transmitter with 12 dB carrier
30、reduction: 0,063 times its rated power (peak envelope power for full modulation). - Establish a reference line on the oscilloscope. - Modulate the transmitter with a 800 Hz or 1 O00 Hz audio signal to full modulation so that: a) for an SSB transmitter with 6 dB carrier reduction, the peak envelope a
31、mplitude on the RF oscilloscope is twice the carrier reference amplitude; b) for an SSB transmitter with 12 dB carrier reduction, the peak envelope amplitude on the RF oscilloscope is four times the carrier reference amplitude. In the case of an SSB transmitter with 12 dB carrier reduction, check th
32、at the mean power of the transmitter modulated as above is 0,625 times its rated power (peak envelope power for fuliy rnoduiated transmitter). - O BSI 05-2000 STD.BSI BS EN 60244-15-ENGL 2000 M lb24bb9 08474b8 656 Page 9 EN 60244-15:2000 - Note the voltage of the audio signal for the transmitter und
33、er test as the reference value for full modulation. 6.3.4 Calculation and presentation of results The results may be presented as a table stating the rated output power of the transmitter and detailing the power levels measured, together with the modulating frequency used. State the measured referen
34、ce levels of the modulating signal for full modulation. 7 Transmission performance Characteristics The performance characteristics of the transmitter are determined by RF measurements, or by audio measurement after detection. For DSB transmitters, envelope detection is generally used. For SSB transm
35、itters, synchronous detection is necessary. Where necessary, the special detection mode is given with the measurements. 7.1 Modulation 7.1.1 Introduction In amplitude-modulated transmission, the output signal has an amplitude determined by the instantaneous amplitude of the modulating signal. The de
36、viation of the envelope amplitude from the unmodulated carrier amplitude is a function of the depth of the modulation. In the case of double side-band transmission with full carrier, the depth of modulation is expressed as “modulation factor“. The modulation factor is the ratio of (1) the deviation
37、from the average of the envelope to (2) the average of the envelope. However, the concept of modulation factor is not appropriate for dynamic controlled or reduced carrier DSB systems, nor is it appropriate for SSB systems with or without carrier reduction. For these systems, the depth of modulation
38、 is expressed as “utilization factor“. The appropriate definitions of depth of modulation for the various systems of AM transmission used in broadcasting are given in 7.2 to 7.4. 7.2 DSB modulation 7.2.1 Definition For DSB modulation the term “modulation factor“ is used. Modulation factor is defined
39、 as the ratio of (I) the deviation from the average of the envelope to (2) the average of the envelope. The positive (negative) modulation factor may be distinguished by measuring the positive (negative) peak of the envelope referred to the carrier (see figure 1). NOTE The r.m.s. value of the modula
40、tion factor is defined as the ratio of (1) the r.m s. value of the a.c. component of the envelope amplitude multiplied by 1.41, to (2) the d.c. amplitude of the modulated signal. 8 BSI 05-2000 STD-BSI BS EN b0244-15-ENGL 2000 9 Lb24bh7 08474b9 592 Page 10 EN 60244-15:2000 A sinusoidal modulation m =
41、 100 % represents an r.m.s. modulation factor rn, = 100 %. General rule: a non-sinusoidal modulation with an r.m.s. modulation factor mrmc represents the same power in an a.c. component of the envelope as a sinusoidal modulation with rn = mrms. 7.2.2 Measuring arrangement Measuring arrangement B (se
42、e figure 1) with an envelope detector shall be used. 7.2.3 Measuring procedure - Modulate the transmitter by a sinusoidal measuring signal of 800 Hz or 1 O00 Hz. - Determine the average d.c. value aaverage of the demodulated signal with an instrument responding to the d.c. component of the envelope.
43、 - Determine the positive peak value max and the negative peak value ami, of the a.c. component of the demodulated signal. - Or determine the r.m.s. value A, exclusively of the a.c. component of the demodulated signal (excluding the d.c. component). 7.2.4 Calculation and presentation of results The
44、modulation factor rn is calculated from the formulae: m+ = (amax - aaverage) 1 aaverage x 100, in per cent m- = (aaverage - amin) 1 aaverage x 100, in per cent “- i7i = (amax - min; i (amax + i,) mrms = (A, x 1,41) / aaverage x 100, in per cent The modulation factor corresponds to the modulation dep
45、th and is given in per cent. The modulation frequency shall be stated. 100, in per cent, if m+ = m- 7.3 DCC modulation 7.3.1 Definition In the case of DCC transmission, the depth of modulation is expressed as “utilization factor“. The utilization factor is the ratio of (1) the deviation from the ave
46、rage of the envelope to (2) the maximum achievable average of the envelope. For this system of transmission, it is meaningless to take the controlled carrier amplitude as a reference level for modulation depth. However, the same input signal as in 7.2.3 above shall be used but the results shall be e
47、xpressed as “utilization factor“ (see 7.3.4). 7.3.2 Measuring arrangement Measuring arrangement B (see figure 1) with an envelope detector shall be used. 7.3.3 Measuring procedure - Modulate the transmitter with a sinusoidal measuring signal of 800 Hz or 1 O00 Hz. - Determine the average d.c. value
48、aaverage of the demodulated signal with an instrument responding to the d.c. component of the envelope. O BSI 05-2000 STD.BSI BS EN 60244-15-ENGL 2000 111 1624669 0647470 204 Page 11 EN 60244-15:2000 - Determine the positive peak value amax and the negative peak value min of the a.c. component of th
49、e demodulated signal. - Or determine the r.m.s. value Arms exclusively of the a.c. component of the demodulated signal. 7.3.4 Calculation and presentation of results The utilization factor u is calculated from the formulae: The utilization factor corresponds to the modulation depth and is given in per cent. The modulation frequency shall be stated. 7.4 SSB modulation 7.4.1 Definition For SSB modulation, the depth of modulation is measured as “utilization factor“ u as defined by the following formula and is given in per cent. u = (A - A,) / (A, - A,) x 100 where A A, A, i
