Radiated Emission Measurements in Close Proximity to the Noise Floor

Abstract

Radiated Emission (RE) measurements in close proximity to the noise floor can lead to an overestimation of the measurement results, which may cause a failure situation when performing the limit check. This may be the case when this test is performed on an aerospace system because of the low electric field limits defined in certain frequency ranges to protect critical receiver bands and a high sensitivity of the measuring system is required. Standards define a requirement for the noise floor to be at least 6 dB below the applicable limit. This is not always feasible when measuring low limit frequency notches using the standard bandwidths and test setups. This paper focuses on the analysis of three different ways of decreasing the noise level and improving the sensitivity of the measuring system: the use of low noise preamplifiers, the use of high gain antennas and the narrowing of the measuring bandwidth.