{"id":2311,"date":"2015-04-16T10:25:15","date_gmt":"2015-04-16T08:25:15","guid":{"rendered":"http:\/\/www.electronic.se\/2015\/04\/16\/methodology-for-destructive-hpm-testing-2\/"},"modified":"2015-04-16T10:25:15","modified_gmt":"2015-04-16T08:25:15","slug":"methodology-for-destructive-hpm-testing","status":"publish","type":"post","link":"https:\/\/www.electronic.se\/en\/2015\/04\/16\/methodology-for-destructive-hpm-testing\/","title":{"rendered":"Methodology for destructive HPM testing"},"content":{"rendered":"

Electromagnetic interference (EMI) with electronic equipment and systems can be caused by natural phenomena as lightning and static electricity, but also unintentionally by switching surges or electric loads influencing the power quality. In addition to the unintentional EMI, interference can occur intentionally. Intentional EMI (IEMI) is a manmade interference with the objective to disturb or destroy electronic equipment.<\/p>\n

The IEMI is common in the military context, where it in its broadest sense is called electronic attack (EA), which is one constituent in electronic warfare (EW). EA spans from jamming of electronic signals to the destruction of electronic hardware, see Figure 1. For the destruction of electronic components and equipment, powerful high-power microwave (HPM) generators are required.<\/p>\n

\"1\"<\/p>\n

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The development of HPM generators [2] [3] has reached a sufficient maturity for weaponization and for taking the step from the laboratory into the tactical arena [4][5].<\/p>\n

Another indication of the actuality of the threat is that high-power electromagnetic environments and their effects have been introduced in various standards, such as the\u00a0IEC 61000-series [6] and US Department of Defense MIL-standards, e.g. [7].<\/p>\n

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When studying effects of EMI disturbance and jamming, low-level tests can be performed since the system responses are linear. However, when studying destructive effects, the system response becomes non-linear and scaling from low-level tests will not be possible. To be able to perform tests in the destructive, non-linear regime, FOI is developing a relevant test methodology and appropriate facilities.<\/p>\n

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Test methodology<\/h3>\n

In general, susceptibility testing of electronic equipment is demanding since the electromagnetic coupling into an object is strongly dependent on frequency, polarization and direction of incidence [8]. Thus, during an HPM test, the device under test (DUT) must be irradiated in a broad frequency interval (at least the S-band, 2-4 GHz), from all directions and with at least two polarizations.<\/p>\n

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Destructive HPM testing of electronic equipment requires that the DUT is subjected to very high power densities, usually on the order of several hundred kW\/m\u00b2, or over 10 kV\/m [9]. Such a high power density can be achieved using an HPM-generator, which typically is a free electron vacuum device that delivers a few tens of megawatts up to several gigawatts of microwave power.<\/p>\n

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However, these generators are not generally frequency-tunable, meaning that a separate HPM-source must be used for each frequency to be tested. A consequence of this is that destructive, or interfering, HPM-testing of electronic equipment is usually performed only at one or a few, preset, discrete frequencies [10]. It is possible to design a low level (megawatt) type of HPM-generator that is able to produce threat levels at the small distances required for testing purposes and that can be frequency-tuned by changing the geometrical dimensions inside the generator.<\/p>\n

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But this kind of frequency tuning usually includes breaking the vacuum and exchanging the physical parts that determine the operating frequency. This is especially true if the\u00a0frequency needs to be changed more than about 10 %. Smaller frequency adjustments\u00a0(<10 %) can sometimes be obtained by external control of the interior geometry. Hence, direct HPM-testing at more than one single frequency will be extremely time-consuming.<\/p>\n

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In order to cover a wide frequency span and to be able to test at many frequencies in this band, destructive testing can be divided into two phases. The first phase will consist\u00a0of high level testing in a reverberation chamber (RC), where very high power densities are relatively easy to obtain with a limited amount of input power [11]. The RC-test will give information on at which power densities and frequencies the DUT breaks. With this information it is then possible to use a small, megawatt class, HPM generator that is tuned to the desired frequency and irradiate the DUT directly in an anechoic chamber. This step will give the needed additional information regarding the angular sensitivity of the DUT.<\/p>\n

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In summary, the proposed test method consists of the following two test phases:<\/p>\n