Overview

In order to select an optimal method for EMF measurement in the near-field, it is first necessary to determine which quantities best characterize the field. These quanitites will then be the subject of the measurement.

From the point of view of antenna performance evaluation, it is essential to measure the strength of E or H components near the antenna, which then makes it possible to find the current or the charge distribution along the antenna. With this as a basis, it is possible to find the radiation pattern of the antenna and its input impedance. The measurement of E, H or S in the near-field (with the phase information conserved) permits, with some complex calculations, finding the antenna's radiation pattern in the far-field. From the point of view of shielding, absorbing, or EMF attenuating materials, investigations of the E, H and S measurements are sufficient.

If we are interested in protection against unwanted exposure to EMF, and in biomedical investigations in particular, the E, H and S measurements are not enough. This area of investigation requires more precise qualification of the parameters that should be a subject of the measurement. The proposals cited previously for the protection standards provide, as the basic criterion of the interaction of the EMF with biological media, the power or energy absorbed in the mass unit (Specific Absorption Rate (SAR) and Specific Absorption (SA) in Table 1). Sometimes the power absorbed in volume units is applied, and a widely accepted measurement is the temperature...