Dual function strap for resonating elements and ultra high frequency antennas
A combined EAS and RFID circuit includes an HF coil antenna, a UHF tuning loop, and an RFID chip coupled to a strap that includes a first coupling area and a second coupling area. The coil ends of the HF coil antenna are configured to capacitively and/or conductively couple to one or both of the first coupling area or second coupling area of the strap. The HF coil antenna can include a gap between turns for non-interfering placement of the UHF tuning loop. The EAS circuit can be deactivating upon application of a field at the resonant frequency of sufficient intensity to cause the breakdown voltage to be exceeded between a coil end and coupling area. The threshold breakdown voltage between a coil end and a coupling area can be reduced by laser ablation treatment of a conductive surface of one or both of the coil end or coupling area.
1. A device, comprising:
a Radio Frequency Identification (RFID) chip;
an ultra high frequency (UHF) tuning loop conductively coupled to the RFID chip;
a first coupling pad conductively coupled to the RFID chip and the UHF tuning loop;
a second coupling pad conductively coupled to the RFID chip and the UHF tuning loop; and
a high frequency (HF) coil antenna including a first coil end configured to couple with the first coupling pad and a second coil end configured to couple with the second coupling pad and the HF coil antenna includes a plurality of turns and wherein the HF coil antenna includes a gap between a first turn and a second turn for placement of the UHF tuning loop between the first turn and the second turn.
2. The device of claim 1 , further comprising:
a UHF antenna coupled to exactly one of the first coupling pad or the second coupling pad.
3. The device of claim 1 , wherein placement of the UHF tuning loop in the gap is configured to reduce electromagnetic interference between the HF coil antenna and the UHF tuning loop.
4. The device of claim 1 , wherein the first coil end is conductively coupled to the first coupling pad, and wherein the second coil end is conductively coupled to the second coupling pad.
5. The device of claim 1 , wherein the first coil end is capacitively coupled to the first coupling pad, and wherein the second coil end is capacitively coupled to the second coupling pad.
6. The device of claim 5 , wherein at least one of the capacitively coupled coil end and the associated coupling pad are configured to open circuit upon application of a field, at a resonant frequency, with intensity sufficient to exceed a threshold capacitive breakdown voltage of the at least one of the capacitively coupled coil end and the associated coupling pad.
7. The device of claim 5 , wherein one or more of the capacitively coupled coil end or the associated coupling pad includes a conductive surface treated by laser ablation.
8. The device of claim 7 , wherein the conductive surface treated by laser ablation is configured to reduce a threshold capacitive breakdown voltage between the one or more of the capacitively coupled coil end and the associated coupling pad.
9. The device of claim 5 , further comprising:
a dielectric adhesive configured to join at least one of the capacitively coupled coil end and the associated coupling pad.
10. The device of claim 5 , further comprising:
a substrate configured to fold along a fold line, and join at least one coil end and one associated coupling pad when folded, and
wherein the RFID chip and the associated coupling pad are displaced only on one side of the fold line of the substrate, and
wherein at least a portion of the HF coil antenna is on the other side of the fold line.
11. The device of claim 1 , wherein the first coil end is capacitively coupled to the first coupling pad with a first capacitance C 1 , wherein the second coil end is capacitively coupled to the second coupling pad with a second capacitance C 2 , and wherein C 1 and C 2 are not equal.
12. The device of claim 11 , wherein C 1 and C 2 are different due, at least in part, to differences in geometries of the first coil end and the second coil end.
13. The device of claim 11 , wherein C 1 and C 2 are different due, at least in part, to differences in an overlapping area of the first coil end and the first coupling pad compared to an overlapping area of the second coil end and the second coupling pad.
14. The device of claim 11 , wherein the dielectric adhesive used to couple the coil end to the coupling pads is formulated to undergo a dielectric breakdown at a threshold breakdown voltage that is lower than a voltage presented at C 1 but higher than a voltage presented at C 2 .