Prediction of Electronic Board Radiated Emissions from Near Field Characterization

Abstract

This paper presents the post-processing methodology devoted to Near-Field Measurement (NFM) to provide assistance in the EMC design phases of complex electronics products. The major Airbus Defence and Space challenge for incoming year concerns the control of units radiated emissions (RE). High speed links induce more and more Radiated Emissions (RE) non-conformities for units in on-board receiver frequencies (ex: GPS Ll, GPS L2, S-band TCR …). Huge amount of non-conformances, additional test campaigns to recover acceptable levels and system level analysis require a dedicated NF extrapolation methodology to decrease the number of RE tests at unit level. Based on measurements of the two tangential components of magnetic fields $H_{x}$ and $H_{y}$ very close to the device, the proposed “NFS2RE” methodology allows: $\blacksquare$. The estimation of the four remaining components $H_{Z},E_{x}, E_{y}$ and $E_{z}$ in Near-Field (NF) region. (These sensitive components are more difficult to measure). $\blacksquare$. The extrapolation of EM fields for each frequency $f$ at a distance $d$ from the board ($d=lm$ for RE test). The methodology proposed in this paper is based on the Planar Wave Spectrum (PWS) representation of fields adapted to the EMC problematic. A focus on the sensitive parameters of the algorithm are discussed especially concerning spectrum and spatial resolution optimisation based on adaptive Zero Padding (ZP) technique. Two radiating electric and magnetic antennas are used to validate the proposed algorithm based on comparison with “3D” simulation results which overcome measurement environment problems. A microstrip line experimental test case is then measured in both NF and RE conditions to validate the extrapolation method.