Exposure to the near Field of an RF Plastic Sealer

A procedure for evaluating exposure to the near-field of an RF plastic sealer is proposed. The sealer examined was of a sewing-machine-type operating at a frequency of 40 MHz. The field distribution of this sealer was measured with near-field strength monitors. The distribution was found to be approximately the same as that produced by a combination of electric and magnetic dipoles, the moments of which could be determined by a single-point measurement of electric and magnetic fields and the configuration of RF feed. For this dipole source model the specific absorption rate (SAR) of a human model was calculated using the Method of Moments. It may be concluded that the SAR distribution in a human model can be evaluated using an equivalent source model, at least for a sewing-machine-type RF sealer. A similar procedure may be applied to the fields generated by other types of sealers.