RFID TAG READER

• US 20080238682A1
• Filed: 03/19/2008
• Published: 10/02/2008
• Est. Priority Date: 03/26/2007
• Status: Abandoned Application

• Current Assignee: Sanden Corporation (Qingdao Huatong State-Owned Capital Operation (Group) Co., Ltd.)
• Original Assignee: Sanden Corporation (Qingdao Huatong State-Owned Capital Operation (Group) Co., Ltd.)
• Inventors: Shimamoto, Gaku, Matsumoto, Naoto, Tabata, Masaru, Satou, Masaaki, Kuwako, Yuji
• Application Number:
  US12/051,426
• Publication Number:
  US 20080238682A1
• Time in Patent Office: Days
• US Class Current: 340/572.4
• 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: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop

Abstract

A control unit of a reader superimposes a control signal for antenna switching on a high frequency signal outputted into an antenna unit from a high frequency circuit. The antenna unit includes: separators for separating the superimposed signals into high frequency signals and control signals; a switch circuit for switching loop antennas; and a control circuit for controlling the switch circuit based on the control signal separated by the separator.

Claims

1. An RFID tag reader comprising:

a plurality of antennas for communication with an RFID tag;

a high frequency circuit for processing a communication signal with the RFID tag;

a signal line for connecting the antennas with the high frequency circuit;

superimposing means for superimposing a control signal for antenna switching on a high frequency signal outputted from the high frequency circuit to the antennas;

separation means for separating the superimposed signal inputted from superimposing means through the signal line into the high frequency signal and the control signal; and

antenna switching means for switching the antennas based on the control signal separated by the separation means.

2. The RFID tag reader according to claim 1, wherein

the superimposing means stops an output of the high frequency signal for a predetermined period and outputs a digitalized control signal within the stopping period,

the separation means separates the signals into the high frequency signal and the control signal with a filter circuit, and

the antenna switching means has retention means for retaining the control signal separated by the separation means and switches the antennas based on the control signal retained by the retention means.

3. The RFID tag reader according to claim 2, wherein

the superimposing means applies a DC bias to the superimposed signal, and

the separation means separates a bias current from the superimposed signal and supplies the bias current to the retention means as a power supply.

4. The RFID tag reader according to claim 1, wherein

the superimposing means superimposes the control signal for antenna switching and a control signal for impedance adjustment on the high frequency signal, and

the RFID tag reader further comprises:

a matching circuit for impedance-matching the high frequency signal separated by the separation means and inputting the signal into the antennas; and

adjustment means for controlling a circuit constant of the matching circuit based on the control signal for impedance adjustment separated by the separation means.

5. The RFID tag reader according to claim 4, wherein

the matching circuit and the adjustment means are common to the plurality of antennas.

6. The RFID tag reader according to claim 1, wherein

the plurality of antennas are a plurality of loop antennas disposed in one antenna unit.

7. The RFID tag reader according to claim 6, wherein

the plurality of antenna units are daisy-chain-connected.