Chassis wavemode effects on hearing aid compatibility at 900 MHz

In this paper, we investigate the effects of the chassis wavemodes on the near-field electromagnetic field intensities that contribute to a hearing aid compatibility test at 900 MHz. It was found that the chassis wavemodes have a significant effect on the antenna near-field performance. We show that the optimum near-field antenna performance is achieved when the antenna´s resonant frequency is aligned with the chassis resonant frequency. With this, a decrease of about 50% can be achieved in the peak magnetic field intensity and a 30% reduction in the peak electric field intensity. Hence, a much better possibility in passing the HAC compliance tests.