RFID reader/writer

• US 20070222608A1
• Filed: 06/28/2006
• Published: 09/27/2007
• Est. Priority Date: 03/16/2006
• Status: Abandoned Application

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Maniwa, Toru
• Application Number:
  US11/475,887
• Publication Number:
  US 20070222608A1
• Time in Patent Office: Days
• US Class Current: 340/572.700
• 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

Abstract

In an RFID reader/writer, a transmitted signal generation unit generates a carrier wave formed by circular polarization. A first antenna transmits and receives a polarized wave of a first polarization component. A second antenna transmits and receives a polarized wave of a second polarization component orthogonal to the first polarization component. When a signal analysis unit receives a reflected wave from a plurality of tags for the carrier waves by the first and second antennas, the unit analyzes the first and second polarization components contained in the reflected wave. Based on the analysis result of the signal analysis unit, electric power to be transmitted from the first and second antennas is set to control the polarized wave of a transmission wave to be transmitted with a command to a plurality of tags.

Claims

1. An RFID reader/writer, comprising:

a generation unit for generating a carrier wave of circular polarization;

a first antenna for transmitting a first polarization component of the carrier wave of circular polarization, and receiving the first polarization component of a reflected carrier wave;

a second antenna for transmitting a second polarization component orthogonal to the first polarization component of the carrier wave of circular polarization, and receiving the second polarization component of the reflected carrier wave;

an analysis unit for analyzing the first and second polarization components contained in the reflected wave from a plurality of tags received by the first and second antennas; and

a setting unit for setting transmission power to be transmitted from the first and second antennas to control the polarization of the carrier wave to be transmitted with a command to the plurality of tags based on an analysis result of the analysis unit.

2. The RFID reader/writer according to claim 1, wherein

the first and second polarization components are constituted by a vertical component and a horizontal component, and the carrier wave equally includes a vertical component and a horizontal component.

3. The RFID reader/writer according to claim 2, further comprising

a phase shifter which is arranged between the first and second antenna and the generation device, and provides a phase shift of π

/2 between a vertical component and a horizontal component contained in the carrier wave.

4. The RFID reader/writer according to claim 2, wherein

the generation unit for comprises a rotation device providing the second antenna with a π

/2 phase turned signal from a signal to be provided for the first antenna.

5. The RFID reader/writer according to claim 1, wherein

the first and second polarization components are respectively a right-handed polarization component and a left-handed polarization component, and

a carrier wave having only the right-handed polarization component or the left-handed polarization component is transmitted through either the first or second antenna.

6. The RFID reader/writer according to claim 1, wherein

the setting unit sets the transmission power from the first and second antennas using the amplitude of a signal of a polarization component in the first and second antennas obtained as a result of analysis by the analysis unit.

7. The RFID reader/writer according to claim 1, wherein

the setting unit sets the transmission power from the first and second antennas and a phase difference of an electric wave transmitted from each of the antennas using amplitude and a phase of a signal of a polarization component in the first and second antennas obtained as a result of analysis by the analysis unit.

8. An RFID reader/writer, comprising:

a generation unit for generating a carrier wave of linear polarization;

a first antenna for use in transmitting a first polarization component of a carrier wave of the linear polarization, and receiving a first polarization component of a reflected carrier wave;

a second antenna for use in transmitting a second polarization component orthogonal to the first polarization component in a carrier wave of the linear polarization, and receiving a second polarization component of a reflected carrier wave;

an analysis unit for analyzing the first and second polarization components included in reflected waves from a plurality of tags received by the first and second antennas; and

a setting unit for setting transmission power to be transmitted from the first and second antennas to control the polarization of a carrier wave to be transmitted with a command to the plurality of tags based on an analysis result of the analysis device.

9. A method for transmitting a command to a plurality of tags from an RFID reader/writer, comprising the processes of:

generating a carrier wave of circular polarization;

analyzing a first polarization component and a second polarization component contained in reflected waves from a plurality of tags received by a first antenna transmitting the first polarization component of the carrier wave of circular polarization, and receiving the first polarization component of a reflected carrier wave, and a second antenna transmitting the second polarization component orthogonal to the first polarization component of the carrier wave of circular polarization, and receiving the second polarization component of a reflected carrier wave; and

setting transmission power to be transmitted from the first and second antennas to control polarization of the carrier wave to be transmitted with a command to the plurality of tags based on an analysis result of the analysis device.