Antenna designs for wide-band, orientation insensitive RFID devices
View Patent ↗The present subject matter provides an RFID device that operates in wide-band and is orientation insensitive. The RFID device includes a first resonator and a second resonator. The first resonator includes a sheet of electrically conductive material, defining an area covered by a perimeter. The RFID device also includes a slot defined by opposing sides and the slot being extended from an open end of an edge of the perimeter of the sheet to a closed end stretching within an internal region of the sheet. The RFID device includes a conductive member placed between the open end and closed end and is contoured by the slot in between. The second resonator includes a loop conductor coupled to an integrated circuit (chip). The second resonator is contained within the closed end of the slot and is spaced by a gap from the opposing sides. The RFID device is formed on a substrate.
1 . An RFID device comprising:
a first resonator comprising a sheet of electrically conductive material and defining an area covered by a perimeter;
a slot defined by opposing sides and the slot being extended from an open end of an edge of the perimeter of the sheet to a closed end stretching within an internal region of the sheet, wherein a conductive member is placed between the open end and the closed end and is contoured by the slot in between; and
a second resonator comprising a loop conductor coupled to an integrated circuit (chip), wherein the second resonator is contained within the closed end of the slot and is spaced by a gap from the opposing sides, wherein the second resonator is placed within the first resonator, leaving the gap between the first resonator and the second resonator.
2 . The device of claim 1 , wherein the first resonator and the second resonator are formed on a substrate, wherein the first resonator and the second resonator are co-planar to each other.
3 . The device of claim 1 , wherein the first resonator is configured to operate at a first frequency.
4 . The device of claim 3 , wherein the conductive member is configured to tune the first resonator to resonate at the first frequency.
5 . The device of claim 1 , wherein the conductive member is a capacitor.
6 . The device of claim 5 , wherein the resonance of the first resonator is a function of a capacitive reactance of the capacitor and a resistance of the sheet.
7 . The device of claim 5 , wherein the first resonator resonates when asymmetric current follows a path, wherein the path is a function of a shape and dimension of the sheet.
8 . The device of claim 7 , wherein the capacitor is selected from the group consisting of an inter-digital capacitor, a parallel plate capacitor, and a material comprising a conductive connection.
9 . The device of claim 7 , wherein the capacitor is an inter-digital capacitor.
10 . The device of claim 1 , wherein the closed end of the slot is a circular closed end.
11 . The device of claim 1 , wherein a shape of the sheet is one of a square, rectangle, circle, triangle and an irregular shape.
12 . The device of claim 1 , wherein the conductive member extends around the open end and is contoured by the slot.
13 . The device of claim 1 , wherein the second resonator comprises a feeding structure configured to receive an incoming RF signal.
14 . The device of claim 13 , wherein the feeding structure is configured to feed RF power to the first and second resonators, received from the incoming RF signal.
15 . The device of claim 14 , wherein the first and second resonators are triggered with fed RF power to produce a radiation pattern.
16 . The device of claim 15 , wherein the radiation pattern is circularly polarized.
17 . The device of claim 15 , wherein the radiation pattern is elliptically polarized.
18 . The device of claim 1 , wherein the second resonator is inductively coupled to the first resonator.
19 . The device of claim 1 , wherein the second resonator is capacitively coupled to the first resonator.
20 . The device of claim 1 , wherein the second resonator is configured to operate at a second frequency.
21 . The device of claim 20 , wherein the second resonator is tuned with the chip to resonate at the second frequency.
22 . The device of claim 21 , wherein a resonant response of the second resonator is a function of impedance of the chip and reactive inductance of the loop conductor.
23 . The device of claim 22 , wherein the impedance of the chip is one of a function of a parallel capacitance (Cp), parallel inductance (Xr), parallel resistance (Rp), and combinations thereof.
24 . The device of claim 1 , wherein a shape of the loop conductor is one of a circular, elliptical, square, rectangular, and triangular.
25 . The device of claim 1 , wherein the loop conductor in the second resonator is electrically or inductively coupled to the chip.
26 . The device of claim 1 , wherein the closed end of the slot is larger than the second resonator.
27 . The device of claim 1 , wherein the chip is an RFID chip.
28 . The device of claim 1 , wherein the opposing sides of the slot starts at the open end and extend gradually into the internal region of the sheet.
29 . The device of claim 1 , wherein the opposing sides merge with each other at the closed end.
30 . A method for operating an RFID device, the method comprising:
providing a first resonator comprising a sheet and a conductive member;
positioning a second resonator within the first resonator, the second resonator comprising a loop conductor and an RFID chip, wherein positioning the second resonator comprises placing the second resonator within the first resonator, leaving a gap between the first resonator and the second resonator;
exposing the first resonator and the second resonator to an RF signal;
feeding RF power to the second resonator via a feeding structure, wherein the feeding structure is connected to the loop conductor;
inducing the RF power to the first resonator coupled to the second resonator;
exciting the first resonator and the second resonator to operate at an operating frequency;
tuning the first resonator using the conductive member and the second resonator using the RFID chip to resonate at the operating frequency; and
radiating an output RF signal in response to the fed RF signal.
31 . The method of claim 30 , wherein exposing comprises interrogating the RFID device via an interrogator, wherein the interrogation interrogating includes transmission of an interrogation signal to retrieve data from the RFID device through RFID chip.
32 . The method of claim 30 , wherein the operating frequency is a composite frequency of the RFID device, wherein the operating frequency comprises a first frequency or a second frequency.
33 . The method of claim 30 , wherein tuning comprises:
performing impedance matching for the first resonator with a capacitive reactance of the conductive member to operate at the operating frequency; or
performing impedance matching for the second resonator with the RFID chip to operate at the operating frequency.
34 . The method of claim 30 , further comprising forming the first resonator and the second resonator on a substrate.