An implantable medical device comprising first and second coils each comprising one or more circular windings defining a diameter. Each of the first and second coils have a length, wherein the diameter of the one or more windings of the first coil are greater than the length of the first coil, and wherein the diameter of the one or more windings of the second coil are smaller than the length of the second coil, and wherein at least one of the one or more windings of the first coil is substantially orthogonal to at least one of the windings of the second coil.
