EN 60835-1-3-1995 en Methods of Measurement for Equipment Used in Digital Microwave Radio Transmission Systems Part 1 Measurements Common to Terrestrial Radio-Relay Systems and Sat.pdf

1、STDmBSI BS EN bO35-1-3-ENGL 1997 Lb24bb9 Ob4473b 209 BRITISH STANDARD Methods of measurement for equipment used in digital microwave radio transmission systems Part 1. Measurements common to terrestrial radio-relay systems and satellite earth stations Section 1.3 Transmission characteristics The Eur

2、opean Standaxd EN 608351-3 : 1995, together with its amendment Al : 1995, has the status of a British Standard ICs 33.060.30 NO COPYING WITHOUT ES1 PERMISSION EXCEPT AS PERMITTED BY COPYRIGRT LAW BS EN BS 7573 : Section 1.3 : 1993 1992 60835-1-3 : 1997 IEC 835-1-3 : Incorporating Amendment No. 1 to

3、BS 7573 : Sectwn 1.3 : 1993 (renumbers BS as 1997) and Amendment No. 1 to 1997 BS EN 60835- 1-3 : BS EN 60835-1-3 : BS EN 60835-1-3 : 1997 Issue 2, September 1997 Amd. No. Date 9599 Septeniber 1997 c Text affected indicated by a sideline in the niargin Committees responsible for this British Standar

4、d The preparation of this British Standard was entrusted by the Electronic Equipment Standards Policy Committee (EEL/-) to Technical Committee EEL25, upon which the following bodies were represented: British Broadcasting Corporation Hritish Radio and Electronic Equipment Manufacturers Association Br

5、itish Telecommunications plc Institution of Electrical Engineers Radio, Electrical and Television Retaileis Association Radiocommunicat.ions Agency The following body was also represented in the drafting of the standard, through subcommittees and panels: ERA Technology Ltd. This British Standard, ha

6、ving been prepared under the direction of the Electronic Equipment Standards Policy Committee, was published under the authority of the Standards hard and coines inro effect on 15 April 1993 O BSI 1997 The following BSI references relaw to the work on this standard: Coinmittee reference EEL, 25 Ihft

7、 for coininent !%L;iY(i95 I)( ISBN O 580 217%3 7 x x cn Front cover Inside front cover b i EN front cover iib iii iv 1 2 3 4 5 6 7 a 11 STD-BSI BS EN bO835-1-3-ENGL 1997 Lb24bb9 Ob44738 081 Issue 1, September 1997 BS EN 60835-13 : 1997 2 8 2 2 Sa 1 1 8b 1 blank 9 Original 2 10 original 2 11 original

8、 1 12 original 1 13 original Original 14 Original blank 15 original Original 15a 1 Original 15b 1 Original 15c 1 Original 15d 1 Original 16 original Original Back cover 2 Original Inside back cover blank Summary of pages The foliowing table identifies the current issue of each page. Issue 1 indicate

9、s that a page has been introduced for the first time by amendment. Subsequent issue numbers indicate an updated page. Vertical sidelining on replacement pages indicates the most recent changes (amendment, addition, deletion). Page I issue II Page I issue Change of identifier Wherever BS 7573 : Secti

10、on 1.3 : 1993 appears in this standard, it should be read as BS EN 608351-3 : 1997 O BSI 1997 a Issue 2, September 1997 BS EN 60836-1-3 : 1997 Contents page Committees responsible Inside front cover National foreword n Foreword iib Introduction 111 Method . 1 Scope 1 2 Amplitudeifrequency characteri

11、stic 1 3 Groupdelay/frequency characteristic 2 4 AM.-t0-p.m. conversion and am. compression 5 6 Differential gain and phase 8 1 6 Delay difference between two transmission paths 8 A (informative) Bibliography 17 Annex Figures 1 2 3 4 6 6 7 Is (9 I 10 I I 13 Simplified arrangement for measuring the i

12、f. amplitude/frequency characteristic, the group delay/frequency characteristic and am.-to-p.m. conversion Example of oscilloscope display of an amplituddfrequency characteristic Example of an oscilloscope display of a group/delay frequency chasacteristic Arrangement for measuring am.-to-p.m. conver

13、sion factor and amplitude compression Example of spectnim analyser display when measuring am.-to-p.m. Conversion Curves for determining the am.-to-p.m. conversion factor Kp Curves for determining the amplitude compression coefficient G Example of space diversity receiving system where delay differen

14、ce could be a problem Arrangement for measuring delay difference between two branches of a diversity system Delay difference measurement CRT display for a synchronized switch Delay difference measurement: CRT display for a non-synchronized switch Arrangement for measuring the switch+ver characterist

15、ic as a function of delay difference Measurement of absolute delay of an i.f. comDonent or subassembly 9 10 11 12 13 14 15 15a 15b 15b 15b 1% 15d Q BSI 1997 i STD-BSI BS EN b0835-1-3-ENGL 1997 D 1b24bb9 Ob44740 73T H BS EN 60835-13 : 1997 Issue 2, September 1997 National foreword This Section of BS

16、EN 60835 has been prepared by Technical Committee EPU102 (formerly EEy25), and is the English language version of EN 60835-1-3 : 1995, Method7 of measurement for equipment used in digital microwave dio tramission. systems -Part 1: Measurements common to terrestrial radio-relay systems and sateUite m

17、rh stations - Section 3: Tanmnission chracWtics, including amendment Al : 1995, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC 8351-3 : 1992, including amendment No. 1 : 1995, published by the International Electrotechnica Committee (IEC)

18、. Compliance with a British Standard does not of itself confer immunity from legal obligations. ii O BSI 1997 STD-BSI BS EN b0835-1-3-ENGL 1777 1b24bb7 0b44742 b7b * * rn EUROPW STANDARD NORME EUROPENNE EUROP theretore the a.g.c. should be disconnected before making the measurement. 2.2 Methods oi m

19、easurement Measurements may be made using either point-by-point or swept-frequency methods. For the latter case, an example of the measurement arrangement is shown in figure 1. When using the sweep-frequency method, the repetition rate of the sweep-frequency within the generator is normally in the r

20、ange of 10 Hz to 100 Hz with a sinusoidal wave- form. The centre frequency and sweep deviation should be adjusted to the nominal values. The test arrangement in figure 1 may also be used for end-to-end measurements, and the sweep voltage for the X-deflection of the display can be obtained from the r

21、eceiver part. lhe i.f. bandwidth of the i.f. envelope detector should be at least 50 to 100 times the chosen sweep rate. The Y-axis should be calibrated in decibels in different fanges from only a few decibels for measurements in the pass-band, up to some tens of decibels for filter measurements in

22、the stop-band. These features are normally to be found in test equipment of the link analyser type. STD-BSI BS 835-1-3 IEC - EN b35-L-3-ENGL 1797 Lb24bb9 Ob44745 211 With a constant input level, the output level is determined as a function of the frequency. The measurements may be repeated for a res

23、tricted number of different input levels within the normal range of input levels specified for the equipment under test. The measurement may be extended to include frequencies on either side of the pass- band. In such cases, the signal will be appreciably attenuated and it will be necessary therefor

24、e to use a selective voltmeter or selective level-meter to avoid errors caused by harmonics. 2.3 Presentation of results 2.3.1 Amplitude/frequency characteristic The results of the measurements should be presented, preferably, as an XY-record or photograph of the oscilloscope display as shown in fig

25、ure 2. Both the horizontal and the vertical scales of the oscilloscope display should be calibrated. When the results of the measurements are not presented graphically, they should be given as in the following example for an i.f. sub-system: Amplitude/frequency characteristic is within -0,2 dB to +0

26、,1 dB with reference to 70 MHz, from 60 MHz to 80 MHz. 2.3.2 Ripple components When ripple components are easily identifiable from the measured characteristic, they should be expressed in decibels. peak-to-peak and the ripple frequency should be stated. 2.4 Details to be specified The following item

27、s should be included as required in the detailed equipment specification: a) permitted limits of amplitude variation; b) frequency limits; c) reference frequency; d) input levels; e) peak-to-peak amplitude and frequency of ripple components, if applicable. 3 Group-delay/frequency characteristic 3. I

28、 Definition and general considerations The group-delay/frequency characteristic of a network is the first derivative of the phase/angular frequency characteristic and is expressed in seconds. It js usual to measure group-delay variation, which is the difference between the group- delay as stated abo

29、ve and the group-delay at a reference frequency. 2 STD.BSI BS EN b0835-L-3-fNGL 1777 Lb24bb7 Ob4474b 158 835-1-3 IEC The significance of the measurement when made on linear equipment is different from that made on equipment incorporating non-linear devices. When the equipment incorporates a limiter

30、exhibiting amplitude modulation/phase modulation conversion effects, “coupled“ or “indirect“ distortion will be introduced: for example amplitude/frequency variation prior to such a limiter will result in an apparent change of group-delay. 3.2 Method of measurement In the preferred method shown in f

31、igure 1, a sweep-signal having a frequency f, between 10 Hz and 100 Hr and a baseband test-signal having a frequency It (below 1 MHz but higher than fs), are fed to the baseband input(s) of a high-quality (test) modulator which generates a frequency-modulated i.f. signal at a high modulation index b

32、y the sweep- signal, and at a low modulation index by the baseband test signal. The modulated i.f. signal is fed to the equipment under test and is then demodulated by a high-quality (test) demodulator which recovers the baseband test-signal (f,). As the i.f. signal is swept over the i.f. bandwidth,

33、 the demodulated baseband test signal undergoes amplitude and phase variations. The signal from the phase detector is proportional to the i.f. group-delay. For testing r.f. equipment, up-and-down convertors with negligible inherent distortion are used between the i.f. ports of the measuring equipmen

34、t and the r.f. port of the equipment under test. The following conditions should apply: a) The modulation index and test signal frequency (f,) should be small enough to ensure that the corresponding spectrum occupies a bandwidth within which the group- delay characteristics of the network under test

35、 can be approximated by a straight line. b) Synchronous amplitude modulation generated by the modulator should be negligible in order to avoid amplitude to phase conversion effects. The demodulator should be insensitive to synchronous amplitude modulation and demodulators of the frequency- following

36、 type are well suited to this purpose. c) The phase detector should be insensitive to amplitude modulation which is synchronous with the sweep frequency and should not require a reference phase input signal. d) The measurement frequency-modulator and the measurement frequency- demodulator shown in f

37、igure 1 should be designed for a sufficiently constant group- delay response. When the above conditions are fulfilled, the output voltage (v) from the phase detector (figure 1) is related to the group-delay z (o) of the network under test as follows: where k is a constant representing the phase-dete

38、ctor slope (in Wad) and 3 STD-BSI BS EN b0835-1-3-ENGL 1777 Lb24bbS Ob44747 O74 835-1-3 IEC NOTES 1 The phase detector (figure 1) may be used to measure the phase difference (pt) in addition to group- delay variation (?). If a test frequency of 0,277778 MHz is used, the output voltage from the detec

39、tor for a lo phase difference will be the same as that for group-delay variation of 10 ns. Other test frequencies satisfying condition a) above are acceptable for r( but very low values (ag. 10 kHr) should not be used in order to avoid the effects of excessive noise. 2 In large capacity systems (see

40、 Annex A: Bibliography). the group-delay characteristics may be consid- erably influenced by the amplitude modulationlphase modulation conversion of non-linear networks such as travelling-wave tube amplifiers. limiters and converters. 3.3 Presentation of results 3.3.1 Group-delay/frequency character

41、is tic The group-delaylf requency characteristic should be presented preferably as a repro- duction of an oscilloscope display with frequency on the abscissa as shown in figure 3 for an i.f. equipment under test. When the results are not presented graphically, they should be given as in the followin

42、g example: Total group-delay variation is 2,5 ns in the frequency band 60 MHz to 80 MHz. The test signal frequency (f,) and the corresponding modulation index should be given. 3.3.2 Ripple components When ripple components are identifiable from the measured characteristic, the amplitude should be ex

43、pressed in nanoseconds, peak-to-peak and the ripple frequencies should be stated. 3.3.3 Power-series components If a limited series (generally three terms) is considered to represent with sufficient accuracy the group-delaylfrequency characteristic about the carrier frequency, then the terms of the

44、power-series expansion may be given to represent the displayed character- istic. The first-order term of the series is usually referred to as the “linear“ component and the second-order term as the “parabolic“ component. The coefficients of these terms may be calculated from the displayed response a

45、nd usually are expressed as ns/MHz, ns/MHz2, etc. 3.4 Details to be SpeCifi8d The following items should be included as required in the detailed equipment specification: a) test-signal frequency (fJ; b) the i.f. or ref. swept bandwidth; 4 STD-BSI BS EN b0835-1-3-ENGL 1997 Lb2LibbS Obq4748 TZ0 J35-1-

46、3 IEC c) permitted group-delay variation; d) peak-to-peak amplitude and frequency of ripple components, if applicable; e) power series coefficients. if applicable. 4 A.M.-to-p.m. conversion and a.m. compression 4.1 Definition and general considerations The a.m.-to-p.m. conversion coefficient is give

47、n by: ATO e=- AY where Ag, AV, is the phase deviation in radians or degrees at the output of the equipment under test is the relative amplitude change in per cent or decibels at the input of the equipment under test. The conversion coefficient is expressed in radians/per cent or in degrees/decibel.

48、The a.m. compression C is given by: where AV, A Vi is the relative amplitude change at the output of the equipment under test in numerical units is the relative amplitude change at the input of the equipment under test in numerical units Both definitions are valid for small input level changes. With

49、in digital microwave systems modulation methods are also used in which part of the information is contained in terms of amplitude values, e.g. 16AM. This means that ampli- tude compression and amplitude-to-phase conversion can degrade the signal and give rise to higher BER values. Such non-linear effects sometimes occur in high-power amplifiers, limiters and mixers. Limiters are of course only used in the case of phase modulation such as 4-PSK, but it should be remembered that linear distortion within the passband of the modulated carrier produces a.m and if this a.m.