EN 60244-8-1994 en Methods of Measurement for Radio Transmitters Part 8 Performance Characteristics of Vestigial-Sideband Demodulators Used for Testing Television Transmitters and .pdf
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1、CENELFC EN+b0244-8 94 = 3404583 OL582L 485 BRITISH STANDARD Methods of BS EN measurement for radio transmitters Part 8. Performance characteristics of vestigial-sideband demodulators used for testing television transmitters and transposers The European Standard EN 60244-8 : 1994 has the status of a
2、British Standard 60244-8 : 1995 IEC 244-8 : 1993 CENELEC EN*b244-8 94 3404.583 0358272 333 BS EN 60244-8 : 1995 Amd. No. Date O BSI 1995 Committees responsible for this British Standard Text affected The preparation of this British Standard was entrusted to Technical Committee EPL/lZ, Radiocommunica
3、tion, upon which the following bodies were represented : British Broadcasting Corporation British Radio and Electronic Equipment Manufacturers Association British Telecommunications plc Institution of Electrical Engineers Radio, Electrical and Television Retailers Association Radiocommunications Age
4、ncy The following aSI references relate to the work on this standard: Committee reference EPL/lZ Special announcement in BSI News March 1995 ISBN O 580 24869 8 CENELEC EN*b0244-8 94 m 3404583 0358273 258 m BS EN 60244-8 : 1995 Contents Committees responsible National foreword page Inside front cover
5、 11 Fore word Text of EN 60244-8 2 3 i CENELEC EN*b0244-8 94 m 3404583 0358274 194 m BS EN 60244-8 : 1995 National foreword This British Standard has been prepared by %chnical Committee EPL/12 and is the English language version of EN 60244-8 : 1994 Methods of measurement for radio transmitters Rtrt
6、 8: Per$ormance characteristics of vestigial-sideband demodulators used for testing television transmitters and tramposers, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC 244-8 : 1993, published by the International Electrotechnical Commi
7、ssion (IEC) and is part of a series describing recommended methods of measurement for assessing the performance of radio transmitters. This Part is intended to be used for type tests and acceptance or factory tests and can be used to check the performance characteristics of a VSB demodulator used fo
8、r measuring television transmitters and transposem. The measuring arrangement and method of measurement is, in most cases, identical with that described in BS EN 60244-5 Methods of measur- for radio transmitters Part 5 : 1995 Ry$mnce churacterzstics of television transmitters, provided that the tele
9、vision transmitter is replaced by a high-quality, double-sideband (DSB) modulator capable of delivering test signals suitable for measuring an instrument which is significantly better in performance than a television transmitter. Some other measurements, using RF generators to simulate vision and so
10、und carriers and sideband signais, are fully described. This Part is intended to be used in conjunction with BS EN 60244-5 : 1995. TO facilitate reproduction, some of the figures retain the French text. Other Farts of BS EN 60244 published to date are: Part 5 : 1995 Part 10 : 1993 Part 11 : 1993 Par
11、t 12 : Ry$rmunce characteristics of television transmitters Methods of meclsurement for television transmitters and transposers employing insertion test signals Transposers for FM sound broadcasting Guideline for drawing up descriptive lea - true synchronous and envelope detection, switchable; - in
12、the case of synchronous detection, a quadrature video output; - a switchable “sound trap“ and associated group delay correction filter (with the sound trap switched out, the phaselfrequency characteristic shall be linear); - independent (direct) sound demodulation, and intercarrier sound demodulatio
13、n may be used; - in the case of multiple sound channels, a suitable demodulator and decoder, and analogue or digital sound outputs depending on the system concerned. 3.2 See annex A of IEC 244-5. Description of the television systems and other relevant information 3.3 3.3.1 Output voltage The peak-t
14、o-peak voltage of the video output signal. Definitions relating to the demodulator output and input signals CENELEC EN*b0244-8 94 = 3404583 0358282 260 Page 7 EN 60244-8 : 1994 3.3.2 Reference output level An output voltage of 1 V between sync pulse level and white level. 3.3.3 Input voltage The vol
15、tage of the vision signal at the input of a demodulator for negative (or positive) modulation of the vision carrier is the r.m.s. voltage, expressed in mV or dB(mV), of a sinusoidal signal with an amplitude corresponding to the synchronizing pulse level (or white reference level) of that signal. 3.3
16、.4 Input voltage range The input voltage range of a demodulator is the range of input voltages within which the demodulator can deliver the reference output level within its performance specifications by adjusting the input aitenuator of the demodulator. 4 General conditions of operation and measure
17、ment The vestigial-sideband demodulator shall be tested under normal operating conditions. A sufficient warm-up time, in accordance with the demodulator specification, shall be allowed before commencing measurements. The power supply and environmental conditions shall be stated with the measurement
18、resu Its. If the sources of the demodulators input test signal have significant interaction between their generator outputs, it is recommended that circulators be inserted between the gener- ators and the combining network. If circulators are not available, attenuators of at least 10 dB shall be ins
19、erted at the output of each generator. The instruments used at the input of the demodulator, are connected to the input through a calibrated attenuator or directional coupler inserted in the connection between the input signal source and the demodulator. The impedance presented by the test equipment
20、 connected to the video and audio outputs of the demodulator shall have the nominal value as specified. Any video and audio output not used for the measurement shall be appropriately term i nated. In both cases the return loss of the termination shall be within the tolerances specified. If the sound
21、 trap of the demodulator is in circuit, the associated group delay precorrector in the modulator shall also be in circuit. CENELEC ENxb0244-8 74 3404583 0358283 IT7 Page 8 EN 60244-8 : 1994 All measurements, except those specifically related to one mode of demodulation only, shall be made in both mo
22、des, synchronous and envelope detection. .If the demodulator is fitted with both radio-frequency (RF) and intermediate frequency (IF) inputs, the demodulator specification may require that certain tests be repeated at the intermediate frequency input(s). 5 Measuring arrangements and standard video t
23、est signais Figure 1 gives the measuring arrangements built up from three radio-frequency gener- ators, simulating vision carrier, sideband signals and/or sound carrier(s). This arrangement is used for a limited number of measurements. Most of the measure- ments can be carried out using the arrangem
24、ents described in IEC 244-5. In such cases, the television transmitter should be replaced by the DSB test modulator. Some measurements need modulated sound signals. In these cases, a TV test transmitter should be used. Alternatively, one or two RF generators in combination with the DSB test modulato
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