RFID tag and RFID system having the same

• US 20070139290A1
• Filed: 07/20/2006
• Published: 06/21/2007
• Est. Priority Date: 12/15/2005
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Min, Young-hoon, Song, Il-jong, Tikhov, Yuri
• Application Number:
  US11/489,634
• Publication Number:
  US 20070139290A1
• Time in Patent Office: Days
• US Class Current: 343/860
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment

Abstract

A radio frequency identification tag (RFID) that extends a read range of an RFID reader, and an RFID system including the RFID tag. The RFID tag includes a tag antenna, an IC, and a bonding part electrically connecting the tag antenna to the IC. A complex conjugate of an impedance of the tag antenna is a value obtained by adding an impedance of the IC to an impedance of the bonding part. Thus, the RFID tag can achieve accurate impedance matching between the tag antenna and the bonding, smoothly perform data communication with the RFID reader, and extend the read range of the RFID reader.

Claims

1. A radio frequency identification tag (RFID) that wirelessly transmits a signal to and/or receives a signal from an RFID reader using a specific frequency band, the RFID comprising:

a tag antenna that transmits the signal to and/or receives the signal from the RFID reader;

an integrated circuit (IC) electrically connected to the tag antenna that transmits the signal to and/or receives the signal from the tag antenna; and

a bonding part electrically connecting the tag antenna to the IC,

wherein a conjugate of an impedance of the tag antenna is an obtained by adding an impedance of the IC to an impedance of the bonding part.

2. The RFID tag of claim 1, wherein the bonding part comprises one or more bonding bumps bonding the tag antenna to the IC.

3. The RFID tag of claim 2, wherein a sum of the impedances of the IC and the bonding part satisfies an equation as follows:

$\frac{1}{\left(\mathrm{Z2}+Z<br><br>\text{\hspace{1em}<br><br>}<br><br>3\right)}=\frac{1}{R<br><br>\text{\hspace{1em}<br><br>}<br><br>1-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>1}+\frac{1}{-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>2}$ $Z<br><br>\text{\hspace{1em}<br><br>}<br><br>2+Z<br><br>\text{\hspace{1em}<br><br>}<br><br>3=\frac{\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>1\right)<br><br>\left(-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>1\right)}{-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>2+\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>1\right)}=\frac{X<br><br>\text{\hspace{1em}<br><br>}<br><br>1<br><br>X<br><br>\text{\hspace{1em}<br><br>}<br><br>2+R<br><br>\text{\hspace{1em}<br><br>}<br><br>1<br><br>X<br><br>\text{\hspace{1em}<br><br>}<br><br>2<br><br>j}{-R<br><br>\text{\hspace{1em}<br><br>}<br><br>1+\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>1+X<br><br>\text{\hspace{1em}<br><br>}<br><br>2\right)<br><br>j}$ $\mathrm{RZ}=\frac{\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1\right)<br><br>\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>2^2\right)}{R<br><br>\text{\hspace{1em}<br><br>}<br><br>1^2+{\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>1+X<br><br>\text{\hspace{1em}<br><br>}<br><br>2\right)}^2}$ $\mathrm{Im}<br><br>\text{\hspace{1em}<br><br>}<br><br>Z=\frac{-X<br><br>\text{\hspace{1em}<br><br>}<br><br>2<br><br>\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1^2+\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>1\right)<br><br>\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>1+X<br><br>\text{\hspace{1em}<br><br>}<br><br>2\right)\right)}{R<br><br>\text{\hspace{1em}<br><br>}<br><br>1^2+{\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>1+X<br><br>\text{\hspace{1em}<br><br>}<br><br>2\right)}^2}$

wherein Z2 denotes the impedance of the IC, Z3 denotes the impedance of the boding part, (R−

jX1) denotes the impedance of the IC, (−

jX2) denotes the impedance of the bonding part, RZ denotes a real impedance of an impedance obtained by adding the impedances of the IC to the bonding part, and ImZ denotes an imaginary impedance of the impedance obtained by adding the impedances of the IC to the impedance of the bonding part.

4. The RFID tag of claim 1, wherein the bonding part comprises one or more wires connecting the tag antenna to the IC.

5. The RFID tag of claim 4, wherein a sum of the impedances of the IC and the bonding part satisfies an equation as follows:

Z2+Z3=(R1−

jX1)+(R2+jX2)
RZ=R1+R2
ImZ=−

(X1−

X2)

wherein Z2 denotes the impedance of the IC, Z3 denotes the impedance of the bonding part, (R1−

jX1) denotes the impedance of the IC, (R2+jX2) denotes the impedance of the bonding part, RZ denotes a real impedance of the impedance obtained by adding the impedances of the IC to the bonding part, and ImZ denotes an imaginary impedance of an impedance obtained by adding the impedances of the IC to the impedance of the bonding part.

6. The RFID tag of claim 1, wherein the bonding part comprises:

one or more bonding bumps; and

a wire part comprising at least one or more wires connecting the tag antenna to the IC.

7. The RFID tag of claim 6, wherein the sum of the impedances of the IC and the bonding part satisfies an equation as follows:

$Z<br><br>\text{\hspace{1em}<br><br>}<br><br>2+Z<br><br>\text{\hspace{1em}<br><br>}<br><br>3=\frac{\left[\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>1\right)+\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>3+\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>3\right)\right]-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>4}{-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>4+\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1-\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>1\right)+\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>3+\mathrm{jX}<br><br>\text{\hspace{1em}<br><br>}<br><br>3\right)}$ $\mathrm{RZ}=\frac{\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1+R<br><br>\text{\hspace{1em}<br><br>}<br><br>3\right)<br><br>X<br><br>\text{\hspace{1em}<br><br>}<br><br>4^2}{{\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1+R<br><br>\text{\hspace{1em}<br><br>}<br><br>3\right)}^2+{\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>1-X<br><br>\text{\hspace{1em}<br><br>}<br><br>3+X<br><br>\text{\hspace{1em}<br><br>}<br><br>4\right)}^2}$ $\mathrm{Im}<br><br>\text{\hspace{1em}<br><br>}<br><br>Z=\frac{-X<br><br>\text{\hspace{1em}<br><br>}<br><br>4<br><br>\left[{\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1+R<br><br>\text{\hspace{1em}<br><br>}<br><br>3\right)}^2<br><br>\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>1-X<br><br>\text{\hspace{1em}<br><br>}<br><br>3\right)<br><br>\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>1-X<br><br>\text{\hspace{1em}<br><br>}<br><br>3+X<br><br>\text{\hspace{1em}<br><br>}<br><br>4\right)\right]}{{\left(R<br><br>\text{\hspace{1em}<br><br>}<br><br>1+R<br><br>\text{\hspace{1em}<br><br>}<br><br>3\right)}^2+{\left(X<br><br>\text{\hspace{1em}<br><br>}<br><br>1-X<br><br>\text{\hspace{1em}<br><br>}<br><br>3+X<br><br>\text{\hspace{1em}<br><br>}<br><br>4\right)}^2}$

wherein Z2 denotes the impedance of the IC, Z3 denotes the impedance of the bonding part, (R1−

jX1) denotes the impedance of the IC, (R3−

jX3) denotes an impedance of the wire part, (−

jX4) denotes an impedance of the bonding bump part, RZ denotes a real impedance of an impedance obtained by adding the impedances of the IC to the bonding part, and ImZ denotes an imaginary impedance of the impedance obtained by adding the impedances of the IC to the impedance of the bonding part.

8. An RFID system comprising:

an RFID reader that wirelessly transmits a signal using a specific frequency band; and

an RFID tag comprising a tag antenna transmitting the signal to and/or receiving the signal from the RFID reader, an IC electrically connected to the tag antenna to transmit the signal to and/or receive the signal from the tag antenna, and a bonding part electrically connecting the tag antenna to the IC,

wherein a complex conjugate of an impedance of the tag antenna is an impedance obtained by adding an impedances of the IC to an impedance of the bonding part.

9. A method of impedance matching between a radio frequency identification tag (RFID) reader and an RFID tag by determining an impedance of a tag antenna of the RFID tag, the method comprising:

determining an impedance of an integrated circuit (IC), the IC electrically connected to the tag antenna and transmitting a signal to and/or receiving a signal from the tag antenna;

determining an impedance of a binding part that electrically connects the tag antenna to the IC;

determining the impedance of the tag antenna by adding the impedance of the IC to the impedance of the bonding part.