A resonant induction wireless power transfer coil assembly comprising: an enclosure; within the enclosure, a resonant induction wireless power transfer coil comprising: a dielectric (402, 403) having a first side and a second side; a first conductor pattern comprising a first plurality of conductors wound in a spiral on the first side of the dielectric; and a second conductor pattern comprising a second plurality of conductors wound in a spiral on the second side of the dielectric, the second conductor pattern being aligned with the first conductor pattern whereby the second conductor pattern reinforces magnetic flux generated by the first conductor pattern, wherein the first and second conductor patterns are placed relative to one another so as to provide flux transmission in a same direction, a ferrite layer (704, 705) adjacent the wireless power transfer coil; and an eddy current shield, wherein the wireless power transfer coil, ferrite layer (704, 705), and eddy current shield are disposed in parallel within the enclosure, characterised in that the ferrite layer (704, 705) has at least one of a spatial density or thickness that decreases towards a perimeter of the wireless power transfer coil. an enclosure; within the enclosure, a resonant induction wireless power transfer coil comprising: a dielectric (402, 403) having a first side and a second side; a first conductor pattern comprising a first plurality of conductors wound in a spiral on the first side of the dielectric; and a second conductor pattern comprising a second plurality of conductors wound in a spiral on the second side of the dielectric, the second conductor pattern being aligned with the first conductor pattern whereby the second conductor pattern reinforces magnetic flux generated by the first conductor pattern, wherein the first and second conductor patterns are placed relative to one another so as to provide flux transmission in a same direction, a ferrite layer (704, 705) adjacent the wireless power transfer coil; and an eddy current shield, wherein the wireless power transfer coil, ferrite layer (704, 705), and eddy current shield are disposed in parallel within the enclosure, characterised in that the ferrite layer (704, 705) has at least one of a spatial density or thickness that decreases towards a perimeter of the wireless power transfer coil. a dielectric (402, 403) having a first side and a second side; a first conductor pattern comprising a first plurality of conductors wound in a spiral on the first side of the dielectric; and a second conductor pattern comprising a second plurality of conductors wound in a spiral on the second side of the dielectric, the second conductor pattern being aligned with the first conductor pattern whereby the second conductor pattern reinforces magnetic flux generated by the first conductor pattern, wherein the first and second conductor patterns are placed relative to one another so as to provide flux transmission in a same direction, a ferrite layer (704, 705) adjacent the wireless power transfer coil; and an eddy current shield, wherein the wireless power transfer coil, ferrite layer (704, 705), and eddy current shield are disposed in parallel within the enclosure, characterised in that the ferrite layer (704, 705) has at least one of a spatial density or thickness that decreases towards a perimeter of the wireless power transfer coil.