The induction coil arrangement 132 of this embodiment therefore comprises a laminate having a first layer (comprising the first flat spiral coil 31), a second layer (comprising the second flat spiral coil 32), and an intermediate third layer (the plate 33) between the first and second layers. The plate 33 thus spaces apart the first and second layers. As the plate 33 is made of non-electrically conductive material, the coils 31, 32 are electrically insulated from each other (other than for the electrically-conductive connector, discussed below). That is, the coils 31, 32 are out of contact with each other. In other embodiments, the coils 31, 32 may be electrically insulated from each other in a different way, such as by an air gap between the coils 31, 32. In some embodiments, the coils 31, 32 may be provided on the plate 33 in any other suitable way, such as by being pre-formed and then attached to the plate 33. In some embodiments, the plate 33 may be other than a layer of a PCB. For example, it may be a layer or sheet of material such as resin or adhesive, which may have dried, cured or solidified.

The use of coils formed from thin, printed electrically conductive material as discussed above obviates the need for Litz wire. Litz wire is comprised of many strands of extremely thin wire gathered in a braid, in order to overcome the effects of diminishing skin depth at higher excitation frequencies. As the tracks on a PCB are thin (typically around 38 um thick for 1 Oz Cu, and around 76 um thick for 2 Oz Cu), their performance at high frequencies can be comparable to the equivalent cross-sectional area of Litz wire, yet without problems arising in relation to brittleness, shaping the Litz wire, or connecting it to other components.