IEC 62037-1 pdf download

IEC 62037-1 pdf download.Passive RF and microwave devices, intermodulation level measurement – Part 1: General requirements and measuring methods
1 Scope
This part of IEC 62037 deals with the general requirements and measuring methods for intermodulation (IM) level measurement of passive RF and microwave components, which can be caused by the presence of two or more transmitting signals. The test procedures given in this standard give the general requirements and measurement methods required to characterize the level of unwanted IM signals using two transmitting signals. The standards in this series address the measurement of PIM, but do not cover the long term reliability of a product with reference to its performance. This standard is to be used in conjunction with other appropriate part(s) of IEC 62037.
4 Characteristics of intermodulation products
PIM interference is caused by sources of non-linearity of mostly unknown nature, location and behaviour. A few examples are inter-metallic contacts, choice of materials, corrosion products, dirt, etc. Most of these effects are subject to changes over time due to mechanical stress, temperature changes, variations in material characteristics (cold flow, etc.) and climatic changes, etc. The generation of intermodulation products originates from point-sources inside a DUT and propagate equally in all available directions. The generation of passive intermodulation products (PIM) does not necessarily follow the law of the usual non-linear equation of quadratic form. Therefore, accurate calculation to other power levels causing the intermodulation is not possible and PIM comparisons should be made at the same power level. Furthermore, PIM generation can be frequency-dependent. When PIM generation is frequency- dependant, the PIM performance shall be investigated over the specified frequency band.
5 Principle of test procedure
Test signals of frequencies f 1 and f 2 with equal specified test port power levels are combined and fed to the DUT. The test signals should contain at least 1 0 dB less harmonic or self- intermodulation signal level than the expected level generated in the DUT. The PIM is measured over the specified frequency range. The intermodulation products of order (2f 1 ± f 2 ), (2f 2 ± f 1 ) etc. are measured. In most cases, the third order intermodulation signals represent the worst case condition of unwanted signals generated; therefore, the measurement of these signals characterizes the DUT in a sufficient way. However, the test set-ups given in Clause 6 are suitable for measuring other intermodulation products. In other systems (such as CATV), the 3 rd order may not be as applicable in characterizing the DUT. Intermodulation can be measured in reverse and forward direction. Reverse and forward is referred to the direction of propagation of the most powerful carrier.
6 Test set-up
6.1 General Experience shows that the generation of intermodulation products originates from point- sources inside a device under test (DUT) and propagates equally in all available directions. Therefore, either the reverse (reflected) or the forward (transmitted) intermodulation signal can be measured. Two different test set-ups are described in Figure 1 and Figure 2 and are for reference only. Other topologies are possible. Set-up 1 is for measuring the reverse (reflected) intermodulation signal only, and set-up 2 is for measuring the forward (transmitted) intermodulation signal. The measurement method (reverse or forward) is dependent upon the DUT. The set-ups may be assembled from standard microwave or radio link hardware selected for this particular application. All components shall be checked for lowest self-intermodulation generation. Experience shows that devices containing magnetic materials (circulators, isolators, etc.) can be prominent sources of intermodulation signal generation. See Annex B for additional set-up considerations. 6.2 Test equipment 6.2.1 General Two signal sources or signal generators with power amplifiers are required to reach the specified test port power. The combining and diplexing device may comprise a circulator, hybrid junction, coupler or filter network. The test set-up self-intermodulation generated (including contribution of the load) should be at least 1 0 dB below the level to be measured on the DUT. The associated error may be obtained from the graph in Figure 3.