Antenna, tag communication apparatus, tag communication system, scanning adjusting method for tag communication apparatus and computer readable medium

• US 7,724,140 B2
• Filed: 06/30/2005
• Issued: 05/25/2010
• Est. Priority Date: 07/01/2004
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Saito, Keisuke, Okamura, Shinichiro, Kawai, Takehiro
• Primary Examiner(s): Swarthout; Brent
• Application Number:
  US11/170,435
• Publication Number:
  US 20060001585A1
• Time in Patent Office: 1,790 Days
• Field of Search: 340/572.1, 340/572.7, 340/10.1, 340/825.49, 340/572.4, 343/754, 343/702, 343/701, 455/562.1, 455/272, 455/575.7, 342/368
• US Class Current: 340/572.7
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 3/14 Systems for determining direction or deviation from predetermined direction aerial arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00; combinations of different interacting aerial units for giving a desired directional characteristic H01Q21/29; aerials or aerial systems providing at least two radiation patterns H01Q25/00
• CPC Class Codes: G01S 3/46 using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
• CPC Class Codes: G01S 7/40 Means for monitoring or calibrating
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence

Abstract

An RFID reader/writer performs a radio communication with an RFID tag. An antenna for tag communication used in the RFID reader/writer is a beam scanning antenna that can perform scanning with the beam of a transmitted radio wave. The beam has a high directivity in a certain scanning direction. The scanning with the beam is performed so that a plane including the certain scanning direction intersects with a floor surface as a reflecting surface on which the strongest reflected wave is generated.

Claims

1. An apparatus configured to be placed within a space defined by a plurality of reflecting surfaces and to communicate with an RFID (RadioFrequency Identification) tag through a radio wave, said apparatus comprising:

at least one antenna configured to transmit a radio wave beam having a first directivity in a first direction and a second directivity which is lower than the first directivity in directions other than the first direction when the apparatus is placed within the space; and

a scanning controller configured to cause the at least one antenna to change an advancing direction of the radio wave beam within a scanning plane when the apparatus is placed within the space,

wherein the scanning plane intersects with one of the reflecting surfaces having higher reflectivity than the other reflecting surfaces at an angle falling within a range from 45 degrees to 90 degrees.

5. The apparatus as claimed in claim 1, wherein:

the at least one antenna comprises;

a plurality of antenna elements; and

a phase shifter configured to shift phases of signals transmitted to the antenna elements so as to generate the radio wave beam.

6. The apparatus as claimed in claim 1, wherein the radio wave is a microwave.

7. The apparatus as claimed in claim 1, wherein:

the at least one antenna includes a plurality of antennas.

8. The apparatus as claimed in claim 1, wherein the apparatus is configured to be placed within the space so that the antenna is disposed separately from the one of the reflecting surfaces.

9. The apparatus as claimed in claim 7, wherein the apparatus is configured to be placed within the space so that at least two of the antennas are arrayed in a direction substantially perpendicular to the one of the reflecting surfaces.

10. The apparatus as claimed in claim 7, wherein the apparatus is configured to be placed within the space so that at least two of the antennas oppose each other across the space.

2. An apparatus for communicating with an RFID (RadioFrequency Identification) tag through a radio wave, said apparatus comprising:

an antenna which communicates with the RFID tag and generates a scanning beam in a space, wherein said scanning beam is narrowed in at least one direction so as to cover a part of the space, and said at least one direction in which the beam is narrowed intersects with a reflecting surface that generates a relatively high intensity reflection;

a scanning control section which controls the scanning with the beam of the radio wave transmitted from the antenna to the space;

a communication section which communicates with the RFID tag through the antenna;

a counting section which counts a number of the RFID tags with which the communication section completes the radio communication; and

a scanning adjusting section for adjusting the scanning with the beam by;

(a) instructing the scanning control section so as to make the antenna perform the scanning with the scanning beam at a certain scanning range and a certain incrementing angle for a certain scanning time;

(b) acquiring the number of the RFID tags counted in the counting section during the scanning;

(c) repeating (a) and (b) for various scanning ranges, incrementing angles and scanning times; and

(d) determining the scanning range, incrementing angle and the scanning time so as to obtain a maximum number of the RFID tags counted in the counting section.

3. A method for adjusting a scanning beam transmitted from an antenna to a space, said antenna communicating with an RFID (Radio Frequency Identification) tag through a radio wave and generates the scanning beam in a space, wherein said scanning beam is narrowed in at least one direction so as to cover a part of the space, and said at least one direction in which the beam is narrowed intersects with a reflecting surface that generates a relatively high intensity reflection, said method comprising:

(a) performing, using a computer, the scanning with the scanning beam at a certain scanning range and a certain incrementing angle for a certain scanning time;

(b) counting, using the computer, a number of RFID tags whose radio communications with the antenna are completed during the scanning;

(c) repeating, using the computer, (a) and (b) for various scanning ranges, incrementing angles and scanning times; and

(d) determining, using the computer, the scanning range, the incrementing angle and the scanning time so that the counted number of the RFID tags is maximum.

4. A computer readable medium comprising a program including instructions for operating an apparatus for communicating with an REID (Radio Frequency Identification) tag through a radio wave, said apparatus having an antenna which communicates with the RFID tag and generates a scanning beam in a space, wherein said scanning beam is narrowed in at least one direction so as to cover a part of the space, and said at least one direction in which the beam is narrowed intersects with a reflecting surface that generates a relatively high intensity reflection, and a scanning control section which controls the scanning with the beam of the radio wave transmitted from the antenna, said instructions comprising:

(a) instructing the scanning control section so as to make the antenna perform the scanning with the scanning beam at a certain scanning range and a certain incrementing angle for a certain scanning time;

(b) acquiring the number of the RFID tags counted during the scanning;

(c) repeating (a) and (b) for various scanning ranges, incrementing angles and scanning times; and

(d) determining the scanning range, incrementing angle and the scanning time so as to obtain a maximum number of counted the RFID tags.