Antenna and electromagnetic shield disposed on a flexible circuit substrate
A wireless power transmitter includes a source coil and a planar short range communication antenna overlaying the source coil. The antenna further includes an antenna element disposed on a first surface of a flexible substrate and a plurality of parallel conductive traces disposed on a second surface of the substrate opposite the first surface. The plurality of parallel conductive traces extend across the substrate from a common shield ground bus located proximate an outer edge of the second surface and provide an electromagnetic shield for the antenna element.
1. A wireless power transmitter, comprising:
a source coil; and
a planar short range communication antenna overlaying the source coil, the antenna further comprising:
an antenna element disposed on a first surface of a flexible substrate, and
a plurality of parallel conductive traces disposed on a second surface of the substrate opposite the first surface, wherein the plurality of parallel conductive traces extends across the substrate from a common shield ground bus proximate an outer edge of the second surface and provide an electromagnetic shield for the antenna element, the substrate comprising a substantially round head portion on which the antenna element and the electromagnetic shield are disposed and an elongate tail portion containing an electrical connector and a plurality of consecutive traces connecting the electrical connector to the antenna element and the electromagnetic shield and the elongated tail portion being bent to locate the electrical connector on a bottom side of the wireless power transmitter.
2. The wireless power transmitter in accordance with claim 1 , wherein the antenna element forms several loops proximate to an outer edge of the first surface.
3. The wireless power transmitter in accordance with claim 2 , wherein the antenna element is a conductive trace arranged in a generally spiral shape.
4. The wireless power transmitter in accordance with claim 3 , wherein the conductive trace is formed of a copper film.
5. The wireless power transmitter in accordance with claim 3 , wherein a spacing between the spiral of the conductive trace is approximately equal to a width of the conductive trace.
6. The wireless power transmitter in accordance with claim 3 , wherein spacing between the spiral of the conductive trace is about 0.15 mm and a width of the conductive trace is about 0.15 mm.
7. The wireless power transmitter in accordance with claim 1 , wherein the plurality of parallel conductive traces is formed of a copper film.
8. The wireless power transmitter in accordance with claim 7 , wherein a spacing between each conductive trace in the plurality of parallel conductive traces is approximately equal to a width of each conductive trace in the plurality of parallel conductive traces.
9. The wireless power transmitter in accordance with claim 8 , wherein the spacing between each conductive trace in the plurality of parallel conductive traces is about 0.15 mm and the width of each conductive trace in the plurality of parallel conductive traces is about 0.15 mm.
10. The wireless power transmitter in accordance with claim 1 , wherein the substrate comprises a polyimide, polyethylene terephthalate lor polyester film.
11. The wireless power transmitter in accordance with claim 1 , wherein the substrate has a thickness of about 0.05 to 0.5 mm.
12. The wireless power transmitter in accordance with claim 1 , wherein the short range communication antenna further comprises at least one thermistor disposed on the substrate in a central region of the head portion which is connected to the electrical connector by at least a pair of dedicated conductive traces.
13. The wireless power transmitter in accordance with claim 1 , further comprising a circular array of magnets surrounding the short range communication antenna, wherein the planar short range communication antenna the circular array of magnets are arranged to be approximately coplanar.
14. The wireless power transmitter in accordance with claim 13 , wherein the magnets in the circular array of magnets are of alternating polarity.
15. A method of assembling a wireless power transmitter, comprising:
providing a source coil;
disposing an antenna element on a first surface of a flexible substrate and disposing a plurality of parallel conductive traces on a second surface of the substrate opposite the first surface to provide an electromagnetic shield for the antenna element, thereby forming a planar short range communication antenna;
forming the substrate to define a substantially round head portion on which the antenna element and electromagnetic shield are disposed and an elongate tail portion containing an electrical connector and a plurality of consecutive traces connecting the electrical connector to the antenna element and electromagnetic shield;
arranging the planar short range communication antenna to overlay the source coil; and
bending the elongated tail portion to locate the electrical connector on a bottom side of the wireless power transmitter.
16. The method in accordance with claim 15 , further comprising forming several loops in the antenna element near an outer edge of the first surface.
17. The method in accordance with claim 15 , further comprising forming the antenna element from a conductive trace arranged in a generally spiral shape.
18. The method in accordance with claim 15 , further comprising forming the substrate to define a substantially round head portion on which the antenna element and electromagnetic shield are disposed and an elongate tail portion containing an electrical connector and a plurality of consecutive traces connecting the electrical connector to the antenna element and electromagnetic shield.
19. The method in accordance with claim 18 , further comprising:
disposing at least one thermistor on the substrate in a central region of the head portion; and
connecting the at least one thermistor to the electrical connector by at least a pair of dedicated conductive traces.