an antenna substrate having a first major surface and a second major surface facing away from the first major surface;

a first antenna pattern formed on the first major surface and comprising an inner conductive coil and an outer conductive coil surrounding the inner conductive coil, wherein the first major surface comprises a first central area surrounded by the inner conductive coil;

a second antenna pattern formed on the second major surface and comprising an inner pattern, an outer pattern, and an extension pattern, wherein the second major surface comprises a second central area surrounded by the inner pattern;

the inner pattern comprising a plurality of curved conductive lines and defining a radially-extending inner channel, wherein the plurality of curved conductive lines of the inner pattern does not extend into the radially-extending inner channel, wherein at least part of the curved conductive lines of the inner pattern overlaps the inner conductive coil formed on the first major surface and is electrically connected to the inner conductive coil through vias;

the outer pattern comprising a plurality of curved conductive lines and defining a radially-extending outer channel, wherein the plurality of curved conductive lines of the outer pattern does not extend into the radially-extending outer channel, wherein at least part of the curved conductive lines of the outer pattern overlaps the outer conductive coil formed on the first major surface and is electrically connected to the outer conductive coil through vias; and

the extension pattern provided in the radially-extending inner channel and the radially-extending outer channel, wherein the extension pattern is connected to the inner pattern and the outer pattern to make the inner conductive coil and the outer conductive coil electrically connected in parallel for a wireless power transfer antenna.