Shielded Cavity Backed Slot Decoupled RFID TAGS
A shielded decoupled RFID tag having a three dimensional cavity formed by conductive material walls and at least one slot in a conductive material wall that creates a main passage for RF communication signals at the operating frequency of the RFID tag to pass into and/or out of the three dimensional cavity.
1 . A shielded decoupled RFID tag comprising:
a decoupler including a three dimensional cavity having conductive material walls;
a tag located in the three dimensional cavity; and
at least one slot in the conductive material wall that creates a passage for RF communication signals to pass into and/or out of the three dimensional cavity.
2 . The shielded decoupled RIFD tag of claim 1 wherein the at least one slot is a single slot.
3 . The shielded decoupled RFID tag of claim 1 wherein the tag includes an IC chip and antenna.
4 . The shielded decoupled RFID tag of claim 1 wherein the tag is the combination of an IC chip and resonator.
5 . The shielded decoupled RFID tag of claim 1 wherein the tag is positioned with respect to the slot such that a coupled field from the slot to the antenna powers the IC.
6 . The shielded decoupled RFID tag of claim 1 wherein the tag is positioned within the cavity at location where the field from the slot to the antenna is strongly coupled.
7 . The shielded decoupled RFID tag of claim 1 wherein one or more spacers are located between the tag and the slot.
8 . The shielded decoupled RFID tag of claim 7 wherein the one or more spacers are made from air, dielectric materials, magnetic materials, artificial magnetic materials, magneto-dielectric materials and combinations thereof.
9 . The shielded decoupled RFID tag of claim 1 wherein one or more spacers are placed over the slot.
10 . The shielded decoupled RFID tag of claim 9 wherein the one or more spacers are made from dielectric materials, magnetic materials, artificial magnetic materials, magneto-dielectric materials or combinations thereof.
11 . The shielded decoupled RFID tag of claim 1 wherein a housing made of a non-conductive material covers an outside surface of the conductive material walls.
12 . The shielded decoupled RFID tag of claim 11 wherein the non-conductive is material housing covers the slot.
13 . The shielded decoupled RFID tag of claim 1 wherein the non-conductive material housing includes a wall portion that is covered with a mounting adhesive.
14 . The shielded decoupled RFID tag of claim 1 wherein the slot is resonant at the operating frequency such as a half-wavelength resonator.
15 . The shielded decoupled RFID tag of claim 1 wherein the cavity is resonant at the operating frequency such as a half-wavelength resonator.
16 . The shielded decoupled RFID tag of claim 1 wherein the tag is resonant at the operating frequency such as a half-wavelength resonator.
17 . The shielded decoupled RFID tag of claim 1 wherein the slot geometry is arbitrary.
18 . The shielded decoupled RFID tag of claim 17 wherein the slot geometry is selected from a circle, an annulus, a square, a rectangle a triangle and a cross.
19 . The shielded RFID tag decoupler of claim 1 wherein a material substantially fills the three dimensional cavity.
20 . The shielded decoupled RFID tag of claim 1 wherein the conductive material walls essentially prevent RF signals at the operation frequency from entering the cavity.
21 . The shielded decoupled RFID tag of claim 1 wherein the electromagnetic field patterns associated with the slot and antenna are coupled.
22 . The shielded decoupled RFID tag of claim 1 wherein the tag, the slot and the cavity are all resonant at the operating frequency.
23 . The shielded decoupled RFID tag of claim 1 wherein the decoupler includes an outside wall portion that includes a mounting adhesive.
24 . The shielded decoupled RFID tag of claim 1 wherein the tag is selected from a passive tag, an active tag or a battery assisted passive tag.