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Emission and Immunity Testing: Test Object Electrical Size and its Implication



Perry F. Wilson


As the electrical size of a test object increases so does the complexity of its antenna pattern. The antenna pattern complexity affects the number of orientations necessary to determine minimum immunity and maximum emission. This has implications for electromagnetic compatibility (EMC) standards. If the true minimum immunity or maximum emission is to be found, then a sufficient number of samples (test object orientations) over the test object antenna pattern need to be taken. If fewer samples are used in an immunity or emission test (e.g., the four orientations presently recommended by International Electrotechncial Commission (IEC) standard 61000-4-3 [1]), then the difference between the estimate based on the low sample number and desired true value needs to be recognized and, if possible, quantified. Examples here suggest that for modest sized test objects (an example of a test object 50 cm in major dimension is considered) maximum coupling may be underestimated by up to 4 dB for present immunity test methods (e.g., IEC 61000-4-3 with an upper frequency limit of 1 GHz). The underestimation increases to 6 dB if the upper frequency were extended to 5 GHz. This result suggests that present immunity and emission standards should consider including the effect of test object size on pass/fail limits.
Proceedings Title
2004 IEEE International Symposium on EMC
Conference Dates
August 9-13, 2004
Conference Location
Santa Clara, CA


antenna pattern, electrical size, emission test, immunity test, pattern sampling


Wilson, P. (2004), Emission and Immunity Testing: Test Object Electrical Size and its Implication, 2004 IEEE International Symposium on EMC, Santa Clara, CA (Accessed April 24, 2024)
Created August 9, 2004, Updated February 19, 2017