Design optimization of transmitting antennas for weakly coupled magnetic induction communication systems.

This work focuses on the design of transmitting coils in weakly coupled magnetic induction communication systems. We propose several optimization methods that reduce the active, reactive and apparent power consumption of the coil. These problems are formulated as minimization problems, in which the power consumed by the transmitting coil is minimized, under the constraint of providing a required magnetic field at the receiver location. We develop efficient numeric and analytic methods to solve the resulting problems, which are of high dimension, and in certain cases non-convex. For the objective of minimal reactive power an analytic solution for the optimal current distribution in flat disc transmitting coils is provided. This problem is extended to general three-dimensional coils, for which we develop an expression for the optimal current distribution. Considering the objective of minimal apparent power, a method is developed to reduce the computational complexity of the problem by transforming it to an equivalent problem of lower dimension, allowing a quick and accurate numeric solution. These results are verified experimentally by testing a number of coil geometries. The results obtained allow reduced power consumption and increased performances in magnetic induction communication systems. Specifically, for wideband systems, an optimal design of the transmitter coil reduces the peak instantaneous power provided by the transmitter circuitry, and thus reduces its size, complexity and cost

Maximum coupling coefficient of various coaxial coils as function of distance between them.

<p>Maximum coupling coefficient of various coaxial coils as function of distance between them.</p

Active and reactive power as function of wire radius.

<p>Legend entries: (aa) optimal multi-layer coil, (bb) optimal single layer solenoid coil, (cc) constant current multi-layer coil, (dd) constant current single layer solenoid coil, (ee) optimal flat coil, and (ff) constant current flat coil.</p

Energy benefit of optimal spiral flat coil over constant current single layer flat coil.

<p>Energy benefit of optimal spiral flat coil over constant current single layer flat coil.</p

Current distribution in optimal multi-layer solenoid coil.

<p>Current distribution in optimal multi-layer solenoid coil.</p

Current distribution in (a) the optimal single layer solenoid coil, and (b) the optimal spiral flat coil.

<p>Current distribution in (a) the optimal single layer solenoid coil, and (b) the optimal spiral flat coil.</p

Current distribution in optimal flat coil: wire radius: (a) 0.1 mm, (b) 0.5 mm.

<p>Current distribution in optimal flat coil: wire radius: (a) 0.1 mm, (b) 0.5 mm.</p

Optimal current comparison of the flat coil with (aa) the predefined current loop locations method with that of (bb) the non-predefined current loop locations method.

<p>Optimal current comparison of the flat coil with (aa) the predefined current loop locations method with that of (bb) the non-predefined current loop locations method.</p

An Example showing the effect of resonance capacitors in broadband magnetic communication.

<p>(a) Circuit schematic, (b) Current PSD, and (c) Corresponding voltage PSD resonant communication system.</p