1、STD-BSI BS EN b3580-2-ENGL 1777 m lbZLIbb9 0587382 BRITISH STANDARD _I Methods of measurement for waveguides Part 2. Level of intermodulation products The European Standard EN 61580-2 : 1996 has the status of a British Standard II17 m BS EN 61580-2 : 1997 IEC 1580-2 11996 SI PERMISSION EXCEPT AS PER
2、MITTED BY COPYRIGHT LAW therefore, the measurement of these signals characterise the WUT in a sufficient way. However, the test Set-ups given in this procedure are also suitable for measuring intermodulation products of higher order. 3 Set-up Two different test Set-ups are described. Both of them al
3、low the measurement of inter- modulation signals of more than 100 dB below carrier level. The set-up on figure 1 may be assembled from standard microwave radio link hardware selected for this particular application. There are two critical components in this configuration which must be carefully chec
4、ked for lowest self-intermodulation generation: the summing device and the circulator used for the decoupling of the intermodulation signals. The set-up on figure 2 allows the combination of current laboratory signal generating devices with one power amplifier only. The self-intermodulation free mea
5、surement dynamic range depends only on the quality of the filter diplexer used for the decoupling of the intermodulation signals. NOTE - The results of measured intermodulation levels of WUT, with mora than one flange generating intermodulation products. can be falsified by super-position. To verify
6、 a reproducible measurement Set-up, knocking the flanges with a screwdriver could be helpful. Experience shows that devices containing magnetic materials (circulators, isolators, etc.) can be prominent sources for intermodulation signal generation. 3.1 Set-up 1 Two or more high power signal sources
7、or signal generators with power amplifiers are required to reach the specified sum power. The summing device may be a circulator, hybrid junction, coupler or filter network provided that the self-intermodulation generated is at least 10 dB below the level to be measured on the WUT. The WUT shall be
8、terminated by a load for the specified power if necessary. The receiving band-pass filter, tuned for the desired intermodulation signal is followed by a low-noise amplifier (if required) and a receiver. 3.2 Test equipment In order to reach level differences of 100 . 150 dB between the carrier leve)
9、and the intermodulation signals, high-performance test equipment is required. All components must be carefully chosen for lowest levels of self-intermodulation generation (see note 4 in 3.3). The Set-up illustrated in figure 1 consists of: signal generators, power output to produce the specified sum
10、 power: frequency stability to match the requirements of the measuring receiver; low-pass filters; isolators; power combiner (see note 1 in 3.3); circulator (see note 2 in 3.3); load; band-pass filter: low-noise amplifier; measuring receiver (see note 3 in 3.3); signal generator for level calibratio
11、n. 3.3 Set-up2 The set-up in figure 2 consists of two or more frequency stabilised signal generators combined with a power-combiner or hybrid. NOTES 1 Alternatively, circulator(s), directional coupler(s). hybrid junctions or fllter networks may be used. 2 The circulator may be replaced by a filter d
12、iplexer. 3 The measuring receiver may be replaced by a spectrum analyser. 4 The interface flanges to the WUT are best constructed as A-type (choke) flanges for minimum intermodulation. For the combined signal, only one power amplifier allowing for the sum power specified for the intermodulation test
13、 is necessary. The high-pass filter at the amplifier output suppresses all intermodulation signals (2Fp - Fs, etc.) below Fp and also the broadband noise, generated by the power amplifier. Furthermore, it acts as a diplexer system together with the receiving band filter. For this Set-up, the low-pad
14、band-pass combination must be designed and selected for a self-intermodulation level of at least 10 dB below the level to be measured on the WUT. STD-BSI SbL58O-2-ENGL 1777 1b24bb70587171 1F1-m Page 6 EN 61580-2 : 1996 The receiving band-pass filter, tuned for the lowest intermodulation signal as de
15、scribed, is followed by a low-noise amplifier (if required) and a receiver. As an alternative, high power generators or generators with individual power amplifiers can be combined to provide the necessary power level. Care must be taken that the high power levels do not produce excessive intermodula
16、tion products in the summing devices. 3.4 Test equipment In order to reach level differences of 100 . 150 dB between the carrier level(s) and the intermodulation signals, high-performance test equipment is required. All components must be carefully chosen for lowest levels of self-intermodulation (s
17、ee note 4). The Set-up illustrated in figure 2 consists of: - signal generators; - frequency stability to match the requirements of the measuring receiver; - signal combiner (see note 1); - power amplifier for the specified sum power; - filter diplexer formed by a waveguide below cut-off and a band-
18、pass filter (see note 2); - load; - low-noise amplifier; - measuring receiver (see note 3); - signal generator for level calibration. NOTES 1 2 intermodulation product(s) possible. For proper diplexing function, the distance between the two filters shall be chosen carefully. 3 The measuring receiver
19、 may be replaced by a spectrum analyser. 4 The interface flanges to the WUT are best constructed as A-type (choke) flanges for minimum intermodulation. Alternatively, circulator(s). directional coupler(s), hybrid junctlons or filter networks may be used. A waveguide below cut-off filter is preferred
20、 because of the very high suppression of the unwanted 4 Preparation of test specimen The WUT shall. be carefully checked for proper power handling range, cleanliness and correct flange interconnection dimensions. STD.BS1 BS EN bL580-2-ENGL 1777 162qbb 0587172 Ob8 Page 7 EN 61580-2 : 1996 5 Procedure
21、 The set-up used shall first be calibrated for correct signal levels transmitted to the WUT. Then, the receiver shall be calibrated for correct level indication using a calibrated signal source. A load with the necessary power rating is then connected to the test pori and the level of self-intermodu
22、lation generated by the different components in the Set-up is recorded. The level of self-intermodulation should be at least 10 dB below the specified value for WUT. Then, the WUT is inserted and terminated with the same load as used for the calibration procedure. The level of intermodulation from t
23、he WUT is read on the receiver. 6 Expression of results The results are expressed as intermodulation free range, for a given power level for the transmitted signal in the WUT. 7 Requirements Compliance with specifications. Page 8 EN 61580-2 : 1996 Genera torIGnrateur FP n Isolateur W=-l F Generator
24、lor kvel calibration Gnrateur pour calibrer les nweaux Circulator Circula teur Charge Band pass tt U Generatorlnrateur Fr Passe bande 2Fp-Fq orlou 2Fq-Fp Low noise amplilier Amplificateur laible bruit Receiver IEC 41496 Figure 1 - Montage 1 Set-up 1 _ STDmBSI BS EN blt580-2-ENGL 1977 m Lb24bb9 05871
25、94 930 m Page 9 EN 61580-2 : 1996 GeneratorIGnrateur p1 Combiner Mlangeur Passe haut Generator for level calibraton Gnrateur Dour calibrer les niveaux I+ I Charge l0)i GeneratorlGnrateur Fa Generatorffinrateur Fn Band pass FQ+FP Passe bande % PF-Fq Low noise amplifier Amplificateur faible bruit Rece
26、iver Rcepteur J * * cn Figure 2 - Montage 2 Set-up 2 IEC 415196 - STD-BSI BS EN b3580-2-ENGL 3997 3b2Libb7 0587375 877 B BS EN 61580-2 : 1997 IEC 1580-2 : 1996 BSI 389 Chiswick Hi Fax: O181 996 7400. BSI offers members an individual updating service called PLUS which ensures that subscriberc automat
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