1、 STDmBSI BS EN b0835- 3-b-ENGL 1777 LbZlrbbS 05757b3 LT7 BRITISH STANDARD Methods of measurement for equipment used in digital microwave radio transmission systems Part 3. Measurements on satellite earth stations Section 3.6 High-power amplifiers The European Standard EN 6OS53-6: 1996 has the status
2、 of a British Standard ICs 33.060.30 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN BS 7573 : Section 3.6 : 1997 1996 60835-3-6 : 1997 IEC 8353-6 BS EN 608363-6 : 1997 Amd. No. Date Committees responsible for this British Standard Text affected The preparation of this B
3、ritish Siamlard was entrusted by Technical Committee EPW12, Radio communication, to Subcommittee EPII12/5, Radio comunicaion systems, upon which the foliowing bodies were represented: British Broadcasting Cowration British Radio and Electronic Equipment Manufacturers Association British Telecommunid
4、ons pic ERATechnology Ltd. Institution of Electrical Engineers Radio, Electrical and Television Retailers Association Radiocommunicalions Agency This British Standard, having been prepared under the direction of the Eiectrotechnicai sector Board, was published under the authority of the Standards Bo
5、ard and comes inb effect on 15 January 1997 Q BSI 1997 I I The foiiowing BSI references relate to the work on this standard: Committee reference EPUlU5 Draft for comment 96/210490 DC IGBN O 680 26393 2 BS EN 6083634 : 1997 Contents Committees responsible Nalionai foreword page Inside front cover ii
6、Foreword Text of EN 6083536 2 3 Q BSI 1997 i STD-BSI BS EN b0835- 3-b-ENGL 1777 Lb24bbS 05757bll 70b BS EN 608353-6 : 1997 National foreword This British Standard has been prepared by Subcommittee EPU12/5 and is the English ianguage version of EN 6083536 : 1996 Methods of measurement for equipment u
7、sed in digital m.imnoaVe radio t?-ansrnhwn systems Part 3: M-vments on saWite ear semiconductor amplif iers normally include field-effect transistors (FET). Travelling-wave tubes (TWT) and GaAs-field-effect transistors (FET) are most frequently used in satellite earth stations. Power amplifiers shou
8、ld have a flat gain over the specified bandwidth to avoid altering the overall transfer characteristics of a system. They should also be as linear as possible to avoid generation of sidelobes in the power spectrum and to limit adjacent channel interference. Finally, low AM to PM conversion and low i
9、ntermodulation products are necessary to limit the degradation caused by non-linearities. . - STD-BSI BS EN b0835- 3-b-ENGL 1777 D lb24bb9 05757bA 551 Page 4 EN 60835-3-6 : 1996 METHODS OF MEASUREMENT FOR EQUIPMENT USED IN DIGITAL MICROWAVE RADIO TRANSMISSION SYSTEMS - Part 3: Measurements on satell
10、ite earth stations - Section 6: High-power amplifiers 1 Scope This section of IEC 835-3 defines and describes the measurements normally carried out on high-power amplifiers used in satellite earth station transmitters. 2 Normative references The following normative documents contain provisions which
11、, through reference in this text, constitute provisions of this section of IEC 835-3. At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this section of IEC 835-3 are encouraged to investigate the possibi
12、lity of applying the most recent editions of the normative documents indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IEC 835-1 -2: 1992, Methods of measurement for equipment used in digital microwave radio transmission systems - Part 7 : Measure
13、ments common to terrestrial radio-relay systems and satellite earth stations - Section 2: Basic characteristics IEC 835-1 -3: 1992, Methods of measurement for equipment used in digital microwave radio transmission systems - Part I: Measurements common to terrestrial radio-relay systems and satellite
14、 earth stations - Section 3: Transmission characteristics 3 Power gain and efficiency 3.1 Input and output power See IEC 835-1-2. Special care shall be taken to exclude from the measurement non-useful signals such as harmonics of the desired frequency. A low-pass filter of known insertion loss at th
15、e measurement frequency shall be connected between the power meter and the measurement point if not already included in the amplifier under test. NOTE - Some amplifiers are subject to damage if driven to excessive output power, therefore it may be necessary to limit the drive level during this measu
16、rement. * * v, STD-BSI BS EN b0835- 3-b-ENGL 1777 1b24bb7 05757b7 498 m Page 6 EN 60836-3-6 : 1996 3.2 Power gain See IEC 835-1-2. High-power amplifiers are usually operated in a non-linear power transfer characteristic region. For this reason, power gain values are given under at least two conditio
17、ns: - small-signal output power; - rated output power, or saturated output power, where rated output power is not specified. In the case of TWT amplifiers, saturated output power is often defined as that level for which a 1 dB increase in input power results in a 0.1 dB increase in output power. For
18、 solid-state amplifiers, frequently the 1 dB compression point is used. The small-signal gain is the gain which is obtained when the amplifier operates in the lin- ear portion of the input power/output power characteristic. The transfer characteristic is considered to be linear when the input power
19、is sufficiently lower than that required to saturate the amplifier. If the high-power amplifier under test has gain control or level control the power gain shall be measured at specified control settings 3.3 Efficiency The efficiency of an amplifier is given by the rated output power divided by the
20、total primary power, including the power for heat exchangers or air-cooling equipment, if required, and is expressed as a percentage. 3.4 Gain stability 3.4.1 Definition The power gain stability of an amplifier is the variation in gain at a specified output power level and frequency over a specified
21、 period of time. It is convenient to distinguish between short-term stability (hours) and long-term stability (months). Gain stability is expressed in decibels. 3.4.2 Method of measurement A suitable measuring arrangement is sh wn in figure 1. After the amplifier under test has attained thermal stab
22、ility, a signal of specified level and frequency is applied to the input port and the output power is adjusted to the specified level. The parameters to be measured are recorded on a multi-track recorder for a speci- fied period of time. This helps to reveal possible correlations between gain change
23、s and parameter changes. STD.BSI BS EN b0835- 3-6-ENGL 1777 Lb2LibbS 0575770 LOT Page 6 EN 60835-3-6 : 1996 These parameters are: - RF output power level; - RF input power level; - primary power supply voltage(s); - ambient temperature or amplifier coolant temperature (whichever is applicable). 3.4.
24、3 Presentation of results The parameters given in the preceding subclause shall be continuously recorded during the specified time interval(s) and the results presented as multi-track XY recordings. 3.4.4 Details to be SpeCf8d The following items should be included, as required, in the detailed equi
25、pment specification: a) input test-signal frequency; b) input test-signal level; c) output power; d) environmental conditions; e) period of time during which measurements are to be made; 1) highest permitted gain fluctuations in the above time period. 4 Return loss See IEC 835-1-2. This measurement
26、is usually made under “cold“ conditions. This means that no electrode voltages are applied. 5 Spurious slgnals See IEC 835-1-2. 6 Amplitude/frequency characteristics See IEC 835-1-3. In some cases, a sweep-frequency method is recommended but care should be taken to ensure that when sweeping the freq
27、uency across the band of interest with constant input power, the output power does not exceed the values recommended for safe operation of the amplifier under test. Since high-power amplifiers are non-linear, the output power shall be specified. 7 Group-delay/frequency characteristic See IEC 835-1-3
28、. * * rL Page 7 EN 60835-3-6 : 1996 When the f.m. method is used, the measurement equipment typically operates at an inter- mediate frequency which has to be up-converted to the frequency of the high-power amplifier and the signal from its output converted back to the intermediate frequency. With so
29、me types of amplifiers, the measurement equipment is liable to introduce a group delay of the same order as that to be measured. It is essential, therefore, to make the measure- ment with and without the high-power amplifier in circuit in the test arrangement, and to calculate the difference between
30、 the two measurements. The phase shift through high-power amplifiers is dependent upon the r.f. drive level and it is important, therefore, that the drive level be kept constant over the sweep-frequency range. 8 Amplitude modulatlonlphase modulation conversion factor See IEC 835-1-3. This parameter
31、is important for modulation involving carrier amplitude changes (e.g. QAM). 9 Intermodulation products See IEC 835-1-2. The intermodulation products due to multicarrier amplification may vary across the operat- ing frequency range of the amplifier under test, so the test should therefore be repeated
32、 for several pairs of frequencies. The third order intermodulation product level varies by 3 dB for a 1 dB change in drive power when the amplifier is operated well below saturation. Figure 2 shows the measurement arrangement. In many cases it is convenient to specify the non-linear characteristics
33、of the amplifier with one single number, the third order intercept point (ICp3). This is a fictitious power level, expressed in dBm. and denotes the intercept point of two straight lines in a plot of output level versus input level (dBm) (see figure 3). One of the lines is the relationship between t
34、he fundamental of the output power to the input power. In lhe plot this line is extended linearly beyond saturation. It has a slope of 1 dB per dB. The second straight line characterizes the relationship between the third order inter- modulation products (as measured in an arrangement according to f
35、igure 3) to the input level. This line has a slope of 3 dB (output) per 1 dB (input). This line is extended (from values well below saturation) linearly to its interception with the “fundamental“ line. The third order intercept point (ICp3) is characterized by: ICp3 = P, + 112 I, where P, (single-ca
36、rrier level) is the output power level (dBm) of one of the two (equal) carriers used in the arrangement, and lM3 is the difference (dB) of levels between P, and one of the intermodulation products. NOTE - The frequencies of the two carriers and of the intermodulation products should be within the tr
37、ansmission bandwidth of the amplifier under test. STD-BSI BS EN b0835- 3-b-ENGL 1777 1b24bb7 0575772 TA2 Page 8 EN 60835-3-6 : 1996 10 Unwanted radiation (leakage) 1 O. 1 Unwanted radiation or cabinet radiation is the r.f. radiation emanating from the cabinet or any other enclosure of the high-power
38、 amplifier which is not absorbed by the r.f. load connected to the port of the amplifier. Definition and general considerations This measurement is carried out to determine radiation hazards and interference levels. National standards for the permissible levels of unwanted r.f. radiation vary but ar
39、e generally in the range up to 10 mW/cm2. 10.2 Method of measurement A suitable measurement arrangement is shown in figure 4. A test signal of sufficient level to drive the amplifier under test into saturation is swept across the pass-band of the amplifier. A test antenna connected to a synchronized
40、 swept- frequency receiver is passed over all areas of the amplifier which are accessible during operation. The receiver and oscilloscope display are calibrated to read r.f. power level over the band to be measured. NOTE - Any alteration of the environment may cause changes in the radiation pattern.
41、 In such cases, the measurement needs to be repeated for all conditions which might be encountered during use of the equipment. 1 O, 3 Presentation of results Any significant radiation levels, .e. those approaching the maximum specified level, shall be recorded together with the signal frequencies a
42、nd the precise location of the test antenna. The power density of the radiation is expressed in mW/cm2 and is given by the power level at the output of the antenna divided by the effective area of the antenna. 10.4 Details to be specified The following shall be included in the detailed equipment spe
43、cification: - permitted highest level of unwanted r.f. radiation expressed in mW/cm2; - frequency range within which measurements are to be made; - distance between the test antenna and the equipment under test. Page 9 EN 60835-3-6 : 1996 - Matched coupler coupler Driver Am di fier RF signal D. Coup
44、ler :O x= Power meter I lr 11 71 t Frequency meter Power meter a Attenuator Attenuator 4 Figure 1 - Arrangement for gain stability measurement Multi-track recorder Primary power supply voltage monitor I STD-BSI BS EN b0835- 3-b-ENGL 1777 1b24bb7 0575774 855 = A RF generator .- Ob !I 1I Page 10 EN 60
45、835-3-6 : 1996 7r RF generator h Amdifier 1 input I I Spectrum I I output 1 power meter analyser power meter Flgure 2 - Arrangement for Intermodulation products measurement t Single-carrier output level (dBm) I / ICPJ PSCL I ._-.-. / ._._. I /i / intermodulation I I I e Singlecarrier input level (dB
46、m) product Flgure 3 - Illustratlon of intercept point Page 11 EN 60835-3-6 : 1996 - Matched coupler - w RF sweep Driver Amdifier Flgure 4 - Arrangement for unwanted r.f. radlatlon measurements STD-BSI ES EN b0835- 3-b-ENGL 1777 Lb24bb7 057577b b2 Page 12 EN 60835-3-6 : 1996 Annex ZA (normative) Norm
47、ative references to international publications with their corresponding European publications This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are lis
48、ted hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). NOTE
49、. When the international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies. IEC publication Year Title ENMD Year EC 8351-2 1992 Methods of measurement for equipment used an EN 60835-1-2 1993 digital microwave dio transmission systems Past 1: Measurements common to terrestrial dio-relay systems and sateUite earth staftions Section 2: Basic chractetics IEC 835-1-3 1992 Section 3: Transmission characteristics EN 60835-1-3 1995 O BSI 1997 STD-BSI BS EN b0835- 3-b-ENGL 1777
