Characterization of EMC sensors in a spherical near-field facility

This paper is devoted to the characterization of electromagnetic sensors. More particularly, it addresses the case of field measurements at frequencies around and above 1 GHz. At such frequencies, parasitic effects resulting from the close instrumentation associated to the sensor need to be identified and possibly compensated to maintain acceptable accuracy. While such effects are negligible at lower frequencies, they are significantly aggravated by the frequency growth up. In this paper, the key idea is to consider that the sensor and its close instrumentation constitute an equivalent antenna, which can be fully characterized by its impedance and vector receiving pattern. While impedances can be classically measured by means of network analysers, far-field patterns can be very conveniently obtained from near field techniques. The spherical geometry is shown to be more particularly convenient for obtaining a 4π steradians coverage. Examples are provided to illustrate the convenience of the near field approach for characterizing home made or commercial electromagnetic sensors and for quantitatively assessing the effects of parasitic interactions