Magnetic induction antenna arrays for MIMO and multiple-frequency communication systems

In magnetic induction communication systems, channel capacity is often a major bottleneck that limits the system performance. This paper proposes a method to increase the channel capacity in such systems by means of an antenna array. A central challenge in the design of magnetic antenna arrays is to achieve low intra-array coupling along with high gain. These two properties are essential for increasing the channel capacity in comparison to single antenna communication systems of comparable volume.The method proposed in this paper utilizes circular loop antennas to reduce the intra-array coupling using magnetic flux cancellation.The mathematic approach employed in this paper considers each coil as a system of coupled inductors, where each inductor is a single turn loop, and the total coil self and mutual inductances are computed by summing the appropriate single turn loop inductances. Volume efficient coil topologies are identified, and an optimization method is proposed to minimize the intra-array coupling, subject to a required inductance. The proposed method allows to design volume efficient, up to 3 × 3, array, or pyramidal shaped 4 × 4 arrays. The results are verified experimentally using the multiple-frequency communication mode.