Radio frequency identification tag and radio frequency identification tag antenna

• US 8,098,201 B2
• Filed: 06/09/2008
• Issued: 01/17/2012
• Est. Priority Date: 11/29/2007
• Status: Expired due to Fees

• Current Assignee: Electronics and Telecommunications Research Institute, Industrial Cooperation Foundation Chonbuk National University
• Original Assignee: Electronics and Telecommunications Research Institute, Industrial Cooperation Foundation Chonbuk National University
• Inventors: Choi, Won Kyu, Kim, Jeong Seok, Choi, Gil Young, Son, Hae Won, Pyo, Cheol Sig, Chae, Jong-Suk
• Primary Examiner(s): DUONG, DIEU HIEN
• Application Number:
  US12/135,851
• Publication Number:
  US 20090140928A1
• Time in Patent Office: 1,317 Days
• Field of Search: 343/700.MS, 343/866, 343/795, 343/741, 340/572.7
• US Class Current: 343/700.MS
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 13/10 Resonant slot antennas
• CPC Class Codes: H01Q 9/0414 in a stacked or folded configuration

Abstract

An RFID tag includes an antenna and a chip, and the antenna includes a first polygonal dielectric material, first and second microstrip lines partially formed in the first dielectric material, a second polygonal dielectric material stacked on the first dielectric material, and a third microstrip line partially formed in the second dielectric material. According to the present invention, the RFID tag can efficiently receive electromagnetic waves to thereby maximize a readable range.

Claims

1. A radio frequency identification (RFID) tag including an antenna that receives an interrogation signal corresponding to a radio frequency (RF) signal and a chip that generates a response signal corresponding to the interrogation signal, the RFID tag comprising:

the antenna, comprising;

a first polygonal dielectric material having a first plane surface corresponding to a ground plane and a second plane surface that does not contact the first plane surface;

a first microstrip line formed in a part of the second plane surface, and having first and second lateral ends and covering a left side of the second plane surface at least at corner surfaces of the left side;

a second microstrip line formed in another part of the second plane surface, and having first and second lateral ends and covering a right side of the second plane surface opposite the left side at least at corner surfaces of the right side, wherein the first lateral ends of the first and second microstrip lines face each other;

a second polygonal dielectric material having a third plane surface and a fourth plane surface that does not contact the third plane surface, and that is stacked on the second plane surface of the first dielectric material such that the third plane surface is stacked on and contacts the second plane surface; and

a third microstrip line formed in the fourth plane surface, and having two lateral ends,

wherein the second lateral ends of the first and second microstrip lines are electrically connected to the ground plane,

wherein the first microstrip line and the second microstrip line serve as a ground plane of the third microstrip line; and

the chip partially formed in the second plane surface and electrically connected to the first lateral ends of the first and second microstrip lines,

wherein the chip transmits the response signal corresponding to the interrogation signal through the antenna.

2. The RFID tag of claim 1, wherein the antenna further comprises:

a first feed terminal connected to one of the first and second lateral ends of the first microstrip line;

and a second feed terminal connected to one of the first and second lateral ends of the second microstrip line, and

the chip is partially formed in the second plane to contact the third plane, is electrically connected to the first microstrip line through the first feed terminal, and is electrically connected to the second microstrip line through the second feed terminal.

3. The RFID tag of claim 2, wherein impedance of the antenna and impedance of the chip respectively comprise a resistance component and a reactance component, a value of the resistance component of the impedance of the antenna and a value of the resistance component of the impedance of the chip are the same in size and have the same sign, and the value of the reactance component of the impedance of the antenna and the value of the reactance component of the impedance of the chip are the same in size but opposite in sign.

4. The RFID tag of claim 3, wherein the impedance of the antenna corresponds to the length of the first microstrip line, the length of the second microstrip line, and the length of the third microstrip line.

5. The RFID tag of claim 4, wherein the resistance component of the impedance of the antenna corresponds to the width of an end connected to the first feed terminal among the first and second lateral ends of the first microstrip line and the width of an end connected to the second feed terminal among the first and second lateral ends of the second microstrip line, and the reactance component of the impedance of the antenna corresponds to the distance of the first and second lateral ends of the first microstrip line, the distance of the first and second lateral ends of the second microstrip line, and the distance of the two lateral ends of the third microstrip line.

6. A radio frequency identification (RFID) antenna for receiving and transmitting radio frequency (RF) signals, the RFID antenna comprising:

a first polygonal dielectric material having a first plane surface corresponding to a ground plane and a second plane surface that does not contact the first plane surface;

a first microstrip line formed in a part of the second plane surface, and having first and second lateral ends and covering a left side of the second plane surface at least at corner surfaces of the left side;

a second microstrip line formed in a part of the second plane surface, and having first and second lateral ends and covering a right side of the second plane surface opposite the left side at least at corner surfaces of the right side;

a second polygonal dielectric material having a third plane surface and a fourth plane surface, and stacked on the second plane surface of the first dielectric material such that the third plane surface is stacked on and partially contacts the second plane surface, the first microstrip line, and the second microstrip line; and

a third microstrip line partially or entirely formed in the fourth plane surface,

wherein the first lateral ends of the first microstrip line and of the second microstrip line face each other,

wherein the first microstrip line and the second microstrip line serve as a ground plane surface of the third microstrip line, and

wherein the RFID antenna has an impedance that is adjustable based on dielectric loss rates of the first and second polygonal dielectric materials, lengths, widths, and impedances of the first, second, and third microstrip line.

7. The RFID antenna of claim 6, wherein one of the first and second microstrip lines has first and second lateral ends that are the same in width.

8. The RFID antenna of claim 6, wherein one of the first and second microstrip lines has first and second lateral ends that are different from each other in width.

9. The RFID antenna of claim 8, wherein the first microstrip line and the second microstrip line respectively have lateral ends that are different from each other in width, and a shorter one of the first and second lateral ends of the first microstrip line and a shorter one of the first and second lateral ends of the second microstrip line face each other.

10. The RFID antenna of claim 6, wherein the third microstrip line has a curved circumference.

11. The RFID antenna of claim 10, wherein the microstrip line has a ring shape.

12. The RFID antenna of claim 6, wherein the third microstrip line has a polygonal-shaped circumference.

13. The RFID antenna of claim 6, further comprising:

a first shorting plate formed in a fifth plane that connects the first and second planes, and physically connecting the first microstrip line and the ground plane so as to short the first microstrip line from the ground plane; and

a second shorting plate formed in a sixth plane that connects the first and second planes, and physically connecting the second microstrip line and the ground plane so as to short the second microstrip line from the ground plane.