On-body and off-body 2.45 GHz MIMO communications for hearing instrument applications

MIMO diversity antennas have been investigated for 2.45 GHz on-body and off-body hearing instrument communication links in an indoor environment. The 2 × 2 antenna setup consists of crossed, linearly polarized antennas. The measured results were treated as a four-branch diversity system. Diversity combining techniques are applied and the diversity gains are found at the 1% outage probability level. It was found that a diversity gain of 12 dB can be obtained for the on-body ear-to-ear link if both antennas at each side of the head are tangential to the surface of the head. If one of the antennas is orthogonal to the head, the subchannel between the orthogonal antennas is much stronger than the other subchannels. In this case, no diversity gain is obtained. In the off-body link between the hearing instrument receiver and a stationary transmitter, diversity gains of up to 7 dB and 8 dB can be obtained for line-of-sight and non-line-of-sight, respectively.