DEVICE FOR READING RADIO FREQUENCY IDENTIFYERS FOR VOLUMETRIC CONFINING OF THE DETECTION REGION

• US 20100194538A1
• Filed: 06/26/2009
• Published: 08/05/2010
• Est. Priority Date: 06/28/2008
• Status: Active Grant

• Current Assignee: Instituto Superior Tã‰Cnico, ISCTE-Instituto Universitário de Lisboa, Creativesystems Sistemas e Serviços de Consultoria Lda (Johnson Controls International plc)
• Original Assignee: Instituto Superior Tã‰Cnico, ISCTE-Instituto Universitário de Lisboa, Creativesystems Sistemas e Serviços de Consultoria Lda (Johnson Controls International plc)
• Inventors: dos Reis Medeiros, Carla Sofia, Cardoso Fernandes, Carlos Antonio, Lopes Leal Rodrigues da Costa, Jorge Manuel
• Granted Patent: US 8,400,273 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 13/206 Microstrip transmission line antennas

Abstract

Device for reading radio frequency identifiers (RFID) ensuring volumetric confinement at UHF of the detection of RFID tags to a desired volume above a reading surface, which includes one or more metallic transmission lines (6) printed on a di-electric substrate (8), on a metallic reference ground plane (7), an RFID reader or interrogator (3) at one end and a load (10) at the other end whereby a structure (19,21,22,23), that comprises the reading surface, in which the one or more transmission lines (6), the dielectric substrate (8) and the metallic reference ground plane (7) are embedded or attached, and the electric fields (11) are contained in planes perpendicular to the one or more transmission lines (6) with one to five wavelengths that extend over all or part of the length of the reading surface, and wherein the dielectric substrate (8) has a low permittivity, less than 1,5 and of the transmission line (6) is comprised between 8 and 15% of the wavelength.

Claims

1. A device for reading radio frequency identifiers (RFID) ensuring volumetric confinement at UHF of the detection of RFID tags to a desired volume above a reading surface, which includes one or more metallic transmission lines printed on a dielectric substrate, on a metallic reference ground plane, an RFID reader or interrogator at one end and a load at the other end characterized by further comprising a structure, that comprises the reading surface, in which one or more transmission lines, the dielectric substrate and the metallic reference ground plane are embedded or attached, and the electric fields are contained in planes perpendicular to one or more transmission lines with one to five wavelengths that extend over all or part of the length of the reading surface, and wherein the dielectric substrate has low permittivity, less than 1.5 and the width of the transmission line is comprised between 8 and 15% of the wavelength.

2. A device according to claim 1, which additionally comprises a matching circuit when the characteristic transmission line impedance is different from the RFID reader or interrogator impedance.

3. A device according to claim 1, wherein one or more transmission lines with straight or curvilinear paths along the reading surface of the structure.

4. A device according to claim 1, wherein the low permittivity substrate is expanded polystyrene.

5. A device according to claim 1, wherein the reference ground plane corresponds to structure when this is metallic.

6. A device according to claim 1, wherein the extension of the reading surface s controlled by the width of the transmission line, with widths between 8 and 15% of the wavelength, and by the dimensions of the reference ground plane.

7. A device according to claim 6, wherein the dimension of the reference ground plane is at least 90% of the reading surface.

8. A device according to claim 7, wherein structure has depth of 30 cm and a length of 100 cm, the low permittivity substrate is 1 cm thickness, the transmission line is 5 cm width for a 50Ω

impedance and the reference ground plane has the same dimensions of the structure.

9. A device according to claim 1, operating in the band between 860 and 960 MHz.

10. An RFID tags confined detection system wherein several devices according to claim 1 are mounted in association.