Dual polarization antenna and RFID reader employing the same

• US 7,427,955 B2
• Filed: 12/07/2005
• Issued: 09/23/2008
• Est. Priority Date: 12/08/2004
• Status: Expired due to Fees

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Chae, Jong-Suk, Pyo, Cheol-Sig, Choi, Won-Kyu, Seong, Nak-Seon
• Primary Examiner(s): PHAN, THO GIA
• Application Number:
  US11/297,182
• Publication Number:
  US 20060145926A1
• Time in Patent Office: 1,021 Days
• Field of Search: 343/700.MS, 343/702, 343/829, 343/846
• US Class Current: 343/700.0MS
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 21/065 Patch antenna array
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 9/0421 with a shorting wall or a shorting pin at one end of the element H01Q9/0414 takes precedence

Abstract

Provided is a dual polarization antenna realized by using four inverted F-type radiators and a Radio Frequency Identification (RFID) reader employing the dual polarization antenna. The dual polarization antenna includes a ground plate and four inverted F-type radiators set up on the ground plate. Currents of the same phase are fed to the first and second inverted F-type radiators each other. Currents of an inverted phase are fed to the third and fourth inverted F-type radiators each other. The four inverted F-type radiators form an angle of 90° with one another. The first and second inverted F-type radiators radiate electric wave of vertical polarization and the third and fourth inverted F-type radiators radiate electric wave of horizontal polarization. Since the dual polarization antenna has excellent orthogonal and isolation characteristics, the antenna can extend a transmission distance between the reader and the tag and improve a communication quality.

Claims

1. A dual polarization antenna, comprising:

a ground plate;

first and second inverted F-type radiators set up on the ground plate in confrontation to each other; and

third and fourth inverted F-type radiators set up on the ground plate in confrontation to each other, wherein currents of the same phase are fed to the first and second inverted F-type radiators; and

currents of an inverted phases are fed to the third and fourth inverted F-type radiators, wherein the first and third inverted F-type radiators form an angle of 90°

with one another; and

the second and fourth inverted F-type radiators form an angle of 90°

with one another; and

the first and second inverted F-type radiators form an angle of 0°

with one another;

and the third and fourth inverted F-type radiators form an angle of 0°

with one another.

2. The antenna as recited in claim 1, further comprising:

a first feeding line for feeding the first and second inverted F-type radiators; and

a second feeding line for feeding the third and fourth inverted F-type radiators, wherein feeding path lengths from a feeding connector of the first feeding line to the first and second inverted F-type radiators are the same, and a difference between feeding path lengths from a feeding connector of the second feeding line to the third and fourth inverted F-type radiators is odd number-times as much as a half-wave length of the antenna.

3. The antenna as recited in claim 2, wherein the first and second feeding lines have an air strip structure and are positioned at a predetermined distance from the ground plate.

4. The antenna as recited in claim 3, wherein the first and second feeding lines are electrically separated from each other.

5. The antenna as recited in claim 1, wherein the first and second inverted F-type radiators radiate electric wave of vertical polarization, and the third and fourth inverted F-type radiators radiate electric wave of horizontal polarization.

6. A Radio Frequency Identification (RFID) reader, comprising:

a dual polarization antenna;

an RF transmitting means for transmitting an RF signal to an RFID tag through the dual polarization antenna;

an RF receiving means for receiving the RF signal from the RFID tag through the dual polarization antenna; and

a signal processing means for processing the transmitted/received RF signals, wherein the dual polarization antenna includes;

a ground plate;

first and second inverted F-type radiators set up on the ground plate in confrontation to each other; and

third and fourth inverted F-type radiators set up on the ground plate in confrontation to each other, wherein currents of the same phase are fed to the first and second inverted F-type radiators each other, currents of an inverted phase are fed to the third and fourth inverted F-type radiators each other.

7. The RFID reader as recited in claim 6, wherein the four inverted F-type radiators form an angle of 90.degree. with one another.

8. The RFID reader as recited in claim 6, further comprising:

a first feeding line for feeding the first and second inverted F-type radiators; and

a second feeding line for feeding the third and fourth inverted F-type radiators, wherein feeding path lengths from a feeding connector of the first feeding line to the first and second inverted F-type radiators are the same; and

a difference of feeding path lengths from a feeding connector of the second feeding line to the third and fourth inverted F-type radiators is odd number-times as much as a half-wave length of the antenna.

9. The RFID reader as recited in claim 8, wherein the first and second feeding lines have an air strip structure and are positioned at a predetermined distance from the ground plate.

10. The RFID reader as recited in claim 9, wherein the first and second feeding lines are electrically separated from each other.

11. The RFID reader as recited in claim 6, wherein the first and second inverted F-type radiators radiate electric wave of vertical polarization, and the third and fourth inverted F-type radiators radiate electric wave of horizontal polarization.