Study of Interference Voltage of an Implanted Pacemaker by Mobile Terminals

Electromagnetic interference (EMI) from mobile phones affecting implanted cardiac pacemakers has become a recent concern. In previous numerical computations of the EMI, a half-wavelength dipole antenna has been employed as a radiator of electromagnetic waves. However, current mobile phones are generally equipped with an internal antenna. Furthermore, recent mobile phone systems are operated at higher frequencies, i.e., 2 GHz, whereas lower frequencies around 900 MHz have been assumed in the previous studies. In this study, a mobile phone with an internal antenna was modeled with a planar inverted-F antenna (PIFA) mounted on a metallic case, in order to calculate the interference voltage induced at the pacemaker due to the internal antenna. The PIFA was then scanned in a plane parallel to the torso surface, in order to calculate the interference voltage at each position and to clarify the detailed relationship between the interference voltage and the position of the antenna. Moreover, the interference voltage was experimentally evaluated to validate the numerical calculations. It is shown that the PIFA has interference voltage characteristics, which differ from those of the half-wavelength dipole antenna. Comparing the calculation with the measurement, both results show the same tendency, especially around the position of maximum interference. Therefore, the measured results indicate the validity of the numerical results.