Investigation of sampling geometry for simultaneous emissions/immunity calibration of free space chambers

This paper investigates the sampling geometry for simultaneous calibration of free space chambers for radiated emissions and radiated immunity tests. The volumetric sampling geometry typical of emissions standards such as ANSI C63.4, CISPR 22, and prEN50147 part 3 is compared to the uniform plane method of IEC 61000-4-3 for radiated immunity measurements in the frequency range of 30 MHz-1 GHz. Since free space methods allow for the use of a single, fixed system of antenna, cabling, and chamber for both emissions and immunity tests, it is proposed that a single calibration procedure with expression of results in accordance with the ISO guidelines is appropriate. A harmonized calibration sampling geometry that can be applied to both types of tests is investigated experimentally and evaluated for a sample free space chamber. The experimental and analytical methods described permit direct expression of the measurement error and uncertainty of the facility and instrumentation in accordance with guidelines published by the ISO and are traceable to a national reference such as NIST through the instrumentation used.