U.S. patent application number 13/933184 was filed with the patent office on 2013-11-07 for inspection method and inspection device for rfid tag.
The applicant listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Yuya DOKAI, Tsuyoshi MUKAI.
Application Number | 20130293356 13/933184 |
Document ID | / |
Family ID | 49327295 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130293356 |
Kind Code |
A1 |
MUKAI; Tsuyoshi ; et
al. |
November 7, 2013 |
INSPECTION METHOD AND INSPECTION DEVICE FOR RFID TAG
Abstract
An RFID tag inspection method includes the steps of transmitting
a measurement signal from a reader/writer simultaneously to a
plurality of RFID tags arrayed on a collective base member and
configured to process radio signals, receiving response waves from
the individual RFID tags in a batch by the reader/writer, and
determining, based on strengths and a number of received signals
read by the reader/writer, whether or not the individual RFID tags
are acceptable. Thus, acceptance/rejection inspection can be
performed on the plural RFID tags, which are arrayed on the
collective base member, in a batch.
Inventors: |
MUKAI; Tsuyoshi;
(Nagaokakyo-shi, JP) ; DOKAI; Yuya;
(Nagaokakyo-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Nagaokakyo-shi |
|
JP |
|
|
Family ID: |
49327295 |
Appl. No.: |
13/933184 |
Filed: |
July 2, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2012/080493 |
Nov 26, 2012 |
|
|
|
13933184 |
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Current U.S.
Class: |
340/10.1 |
Current CPC
Class: |
G06K 7/10019 20130101;
G06K 7/10366 20130101; G06K 7/10465 20130101 |
Class at
Publication: |
340/10.1 |
International
Class: |
G06K 7/10 20060101
G06K007/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2012 |
JP |
2012-092359 |
Claims
1-10. (canceled)
11. An RFID tag inspection method comprising the steps of:
transmitting a measurement signal from a reader/writer
simultaneously to a plurality of RFID tags arrayed on a collective
base member and configured to process radio signals; reading
response waves from each of the plurality of RFID tags in a batch
by the reader/writer; and determining, based on strengths and a
number of received signals read by the reader/writer, whether or
not each of the plurality of RFID tags is acceptable.
12. The RFID tag inspection method according to claim 11, wherein
the measurement signal is transmitted from one reader/writer, and
the response waves from each of the plurality of RFID tags are read
in a batch by the one reader/writer.
13. The RFID tag inspection method according to claim 12, wherein,
in the reading step, the response waves from the RFID tags are
intensified by a reflecting plate.
14. The RFID tag inspection method according to claim 11, wherein
the measurement signal is transmitted from one reader/writer, and
the response waves from each of the plurality of RFID tags are read
in a batch by another one reader/writer.
15. The RFID tag inspection method according to claim 11, wherein
the acceptance/rejection determining step includes a step of
determining whether received signal strengths of the response waves
from each of the plurality of individual RFID tags are not less
than a threshold, and a step of determining whether a number of the
received response waves is matched with a number of the RFID tags
arrayed on the collective base member.
16. The RFID tag inspection method according to claim 11, wherein,
in the transmitting step, a dielectric member is interposed between
the reader/writer transmitting the measurement signal and the
plurality of RFID tags.
17. An RFID tag inspection device comprising: a dielectric member
on which a plurality of RFID tags arrayed on a collective base
member is disposed; a reader/writer disposed at a position opposite
to the collective base member with the dielectric member interposed
between the reader/writer and the collective base member; and a
determining unit configured to determine, based on strengths and a
number of received signals read by the reader/writer, whether or
not each of the plurality of RFID tags is acceptable.
18. The RFID tag inspection device according to claim 17, further
comprising a reflecting plate disposed on an opposite side of the
collective base member relative to the reader/writer.
19. The RFID tag inspection device according to claim 18, further
comprising an adjusting member arranged to adjust a distance
between the reader/writer and the reflecting plate.
20. The RFID tag inspection device according to claim 17, further
comprising another reader/writer for reception, which is disposed
on an opposite side of the collective base member relative to the
reader/writer.
Description
INCORPORATION BY REFERENCE
[0001] The present application claims priority to International
Application No. PCT/JP2012/080493 filed on Nov. 26, 2012, and to
Japanese Patent Application No. 2012-092359 filed on Apr. 13, 2012,
the entire contents of each of these applications being
incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an inspection method and an
inspection device for an RFID (Radio Frequency Identification) tag
used in an RFID system.
[0004] 2. Description of the Related Art
[0005] Recently an RFID system for transferring predetermined
information by performing communication in a non-contact manner
between a reader/writer and an RFID tag attached to an article has
been practiced as an information management system for articles.
The RFID tag and the reader/writer each include a radio IC element
for processing of a high-frequency signal or a feed circuit and an
antenna.
[0006] An HF-band RFID system utilizing a frequency band of 13 MHz
and a UHF-band RFID system utilizing a frequency band of 900 MHz
are generally used as the RFID system. In particular, the UHF-band
RFID system is promising as an article management system because of
having a relatively long communication distance and being able to
read a plurality of tags in a batch.
[0007] As a system for inspecting, prior to shipment, whether or
not the above-mentioned type of RFID tag having been manufactured
is acceptable, Japanese Unexamined Patent Application Publication
No. 2009-181246, for example, discloses a system for conveying a
long sheet on which a plurality of RFID tags are arranged at
predetermined intervals, and performing communication with respect
to the individual RFID tags for inspection. With this system,
however, because the communication is separately performed on the
individual RFID tags such that the RFID tags will not interfere
with each other, i.e., because the communication and the inspection
are carried out in a closed system per RFID tag, a lot of time is
required for the communication and the inspection. Moreover,
because a long sheet is used, the inspection cannot be performed in
a state where a predetermined number of RFID tags are arranged on a
collective base member.
SUMMARY OF THE INVENTION
[0008] Preferred embodiments of the present invention provide an
inspection method and an inspection device for an RFID tag, which
can inspect a plurality of RFID tags, arrayed on a collective base
member, in a batch to determine whether or not the RFID tags are
acceptable.
[0009] An RFID tag inspection method according to a first aspect of
a preferred embodiment of the present invention includes the steps
of simultaneously transmitting a measurement signal from a
reader/writer to a plurality of RFID tags, which are arrayed on a
collective base member and which are configured to process radio
signals, reading response waves from the individual RFID tags in a
batch by the reader/writer; and determining, based on strengths and
a number of received signals read by the reader/writer, whether or
not the individual RFID tags are acceptable.
[0010] With the inspection method described above, the measurement
signal preferably is transmitted to the plural RFID tags
simultaneously, which are arrayed on the given area, and the
response waves from the individual RFID tags are received in a
batch by the reader/writer used for the transmission or by a
reader/writer dedicated for reception. Whether or not the
individual RFID tags are acceptable is determined by analyzing the
received signals. Therefore, the plural RFID tags can be inspected
in a batch in a shorter time with the so-called open system.
[0011] An RFID tag inspection device according to a second aspect
of a preferred embodiment of the present invention includes a
dielectric member on which a plurality of RFID tags arrayed on a
collective base member are disposed, a reader/writer disposed at a
position opposing to the collective base member with the dielectric
member interposed between the reader/writer and the collective base
member, and a determining unit configured to determine, based on
strengths and a number of received signals read by the
reader/writer, whether or not the individual RFID tags are
acceptable.
[0012] The above and other elements, features, steps,
characteristics and advantages of the present invention will become
more apparent from the following detailed description of the
preferred embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1A and 1B illustrate an RFID tag to be inspected; more
specifically, FIG. 1A is a perspective view illustrating one RFID
tag, and FIG. 1B is a perspective view illustrating a plurality of
RFID tags arrayed on a collective base member.
[0014] FIG. 2 is an explanatory view to explain the configuration
for carrying out an inspection.
[0015] FIGS. 3A and 3B illustrate an inspection device according to
a first preferred embodiment of the present invention; more
specifically, FIG. 3A is a perspective view, and FIG. 3B is a front
view.
[0016] FIG. 4 is a flowchart illustrating inspection
procedures.
[0017] FIG. 5 is a graph to explain acceptance/rejection
determination.
[0018] FIG. 6 is a graph to explain the action of a dielectric
pedestal.
[0019] FIG. 7 is a graph to explain the action of a reflecting
plate.
[0020] FIG. 8 is an explanatory view illustrating the basic
configuration of an inspection device according to a second
preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] An inspection method and an inspection device for an RFID
tag, according to preferred embodiments of the present invention,
will be described below with reference to the accompanying
drawings. It is to be noted that common components and portions in
the drawings are denoted by the same reference symbols, and
duplicate description of those components and portions is
omitted.
[0022] As illustrated in FIG. 1A, an RFID tag 10 to be inspected
for acceptance/rejection preferably is constituted such that a pair
of radiation plates 12 is disposed on a long base film 11, and an
RFID chip 13 is mounted between respective opposing ends of the
radiation plates 12. The RFID chip 13 preferably is a known chip
for processing RF signals, and the chip preferably includes a
signal processing circuit, a memory circuit, etc. The RFID chip 13
is constituted as a semiconductor integrated circuit chip. The RFID
chip 13 may be in the form of a bare chip or a packaged IC, for
example. The RFID chip 13 and the radiation plates 12 are joined to
each other preferably via electrical direct coupling (DC
connection) using a solder bump, for example, but they may be
electromagnetically coupled to each other. Furthermore, the RFID
chip 13 may be prepared by mounting a semiconductor integrated chip
to a feed circuit substrate that includes a matching circuit and a
resonance circuit.
[0023] As illustrated in FIG. 1B, the individual RFID tags 10 are
arrayed in parallel or substantially in parallel on a large-area
collective base member 11', which can be separated into the plural
base films 11 independent of one another, such that long sides of
the base films 11 are positioned adjacent to each other. The plural
RFID tags 10 arrayed on one collective base member 11' are treated
as one lot and are subjected to the inspection at the same
time.
[0024] Necessary information, such as the individual number (tag
number), is stored in each of the RFID chips 13 before the RFID
chips 13 are joined to the radiation plates 12. When the RFID tag
10 including the RFID chip 13 is manufactured, the individual
number becomes an identification (ID) number that is identify the
RFID tag 10. For example, if fifty RFID tags 10 are arrayed on one
collective base member 11', numbers 1 to 50 are uniquely assigned
to the RFID chips 13. Moreover, the RFID tag 10 is preferably used
in a UHF-band RFID system utilizing a frequency band of 900 MHz,
for example.
[0025] The inspection of the RFID tag 10 is performed as
illustrated in FIG. 2. The collective base member 11' including the
RFID tags 10 arrayed in parallel or substantially in parallel
thereon is located on a dielectric pedestal 20 in the form of a
flat plate, and the collective base member 11' is covered with a
box 25 including a reflecting plate 26 that is fixed to a ceiling
portion of the box 25. The box 25 is made of a resin, and the
reflecting plate 26 includes a metal film made of aluminum, for
example. On the other hand, an antenna 31 of a reader/writer 30 is
closely disposed just under the dielectric pedestal 20, and a
measurement signal is simultaneously transmitted from the antenna
31 to the plural RFID tags 10. The reader/writer 30 is known in the
art, and the antenna 31 is a patch antenna, which is connected to a
feed circuit 32 and which radiates a high-frequency wave in one
direction perpendicular or substantially perpendicular to an
antenna surface (i.e., in a direction toward the side where the
RFID tags 10 are disposed) with directivity.
[0026] The reader/writer 30 then receives and reads respective
response waves from the RFID tags 10 by the antenna 31 in a batch.
More specifically, the reception and the read of the response waves
from the RFID tags 10 are executed with the reader/writer 30 by
identifying the respective ID numbers of the RFID tags 10 and
measuring an RSSI (Received Signal Strength Indicator) of each of
radio signals corresponding respectively to the ID numbers. At that
time, some portion of the response wave from each RFID tag 10
propagates directly toward the antenna 31, and the other portion of
the response wave propagates toward the antenna 31 after being
reflected by the reflecting plate 26. Whether or not the individual
RFID tags 10 are acceptable is determined based on the strengths
and the number of the received signals, which are read by the
reader/writer 30. Details of such inspection procedures will be
described later with reference to FIG. 4.
[0027] An inspection device 40 is constituted as illustrated in
FIGS. 3A and 3B. The reader/writer 30 is disposed on a pedestal 42
supported by posts 41, and the dielectric pedestal 20, supported by
posts 43, is disposed just above the reader/writer 30. The RFID
tags 10 in one lot are disposed on the dielectric pedestal 20, and
the box 25 including the reflecting plate 26 is arranged on the
dielectric pedestal 20 to cover the RFID tags 10. Furthermore, a
distance A between the antenna 31 of the reader/writer 30 and the
reflecting plate 26 is adjustable by replacing the posts 43 with
others having a different length. In other words, the posts 43
function as distance adjusting member. It is to be noted that the
distance adjusting member can be constituted in various ways. For
example, the distance adjusting member may be constituted by
providing, instead of the posts 43, an elevating mechanism that
moves the dielectric pedestal 20 up and down.
[0028] The inspection procedures will be described below with
reference to FIG. 4. First, the RFID tags 10 in one lot are set on
the dielectric pedestal 20 (step S1). A measurement signal is
transmitted from the antenna 31 of the reader/writer 30 and
response waves are received (step S2). Next, the received signals
are measured and analyzed (step S3). It is determined, based on the
analysis result, whether the received signal strength is not less
than a threshold (see FIG. 5) (step S4).
[0029] As illustrated in FIG. 5, the received signals are analyzed
in terms of the tag number and the received signal strength for
each of the RFID tags 10. If the received signal strengths are all
not less than the threshold, the RFID tags 10 in the relevant lot
are determined to be acceptable in this stage. If any one or more
of the received signal strengths are less than the threshold, the
RFID tags 10 in the relevant lot are determined to be unacceptable
and are discarded (step S9). If disconnection, for example, occurs
in any of the RFID tags 10, the response strength from the relevant
tag is 0. In consideration of such a case, the number of ID numbers
specific to the RFID tags 10 having generated the received signals
with strengths being not less than the threshold is counted (step
S5). It is then determined whether the counted value is matched
with the number of set (inspected) RFID tags 10 in one lot (step
S6). If both the numbers are matched with each other, it is
determined that the RFID tags included in the relevant lot are all
acceptable. If both the numbers are not matched with each other, it
is determined that one or more unacceptable RFID tags are included
in the relevant lot. When the unacceptable RFID tags are not
individually specified, the RFID tags in the relevant lot are all
discarded (step S9). If the above-described inspection procedures
are completed for all prepared lots (YES in step S7), the
acceptable RFID tags are transferred to a shipping step (step
S8).
[0030] In a graph of FIG. 5, a rhombic mark C1 represents the
received signal strength when the RFID tags in one lot are all
acceptable, and a rectangular mark C2 represents the received
signal strength when the measurement is performed again after
replacing only an RFID tag 10a at the tag number 3 with an
unacceptable one.
[0031] Additionally, if the RFID tags in the collective state can
be individually specified for each tag number, it is possible to
discard only the RFID tag 10a that has been determined to be
unacceptable.
[0032] When measuring the received signals in the state where
plural RFID tags are positioned adjacent to each other, the
adjacent RFID tags affect each other and a peak frequency with
respect to a communication distance shifts to the higher frequency
side than when the RFID tag is measured in a state of single unit.
FIG. 6 depicts a transmission power value with respect to a
frequency. As the transmission power takes a lower value, this
implies that the RFID tag reacts with weaker power. The
transmission power becomes weaker as the transmission distance
increases. In other words, the fact that the RFID tag reacts with
weaker power implies capability of communication at a longer
distance.
[0033] In FIG. 6, a rhombic mark D1 represents the transmission
power value when the RFID tag is measured in a state of single
unit. In such a case, the peak frequency with respect to the
communication distance is about 955 MHz, for example. A rectangular
mark D2 represents the transmission power value when the plural
RFID tags are measured in a state adjacent to each other. In such a
case, the peak frequency with respect to the communication distance
shifts to about 985 MHz, for example. Normally, because the RFID
tag in a state of single unit communicates with the reader/writer,
the frequency of each RFID tag is set to be matched with the
radiation frequency of the reader/writer. Accordingly, if the peak
frequency shifts to the higher frequency side when inspecting the
plural RFID tags in a batch, the RFID tag and the reader/writer
cannot efficiently communicate with each other.
[0034] By interposing the dielectric pedestal 20 between the
antenna 31 of the reader/writer 30 and the RFID tags 10, the peak
frequency is lowered to about 925 MHz, for example, as indicated by
a triangular mark D3. Stated in another way, with the interposition
of the dielectric pedestal 20, it is possible to lower the peak
frequency that shifts otherwise to the higher frequency side as
mentioned above, and to realize a situation where the reader/writer
30 and the RFID tags 10 can efficiently communicate with each
other. In practice, the dielectric pedestal 20 is preferably made
of ultrahigh molecular weight polyethylene, and its relative
dielectric constant (.di-elect cons.r) is preferably about 2.3, for
example.
[0035] The reflecting plate 26 has the function of intensifying the
response wave from each RFID tag 10. The magnitude of received
signal strength can be changed by adjusting the distance A (see
FIGS. 2 and 3B) between the antenna 31 of the reader/writer 30 and
the reflecting plate 26. FIG. 7 depicts the received signal
strength for each of the RFID tags 10. More specifically, a
rectangular mark E1 represents the received signal strength when
the distance A preferably is set to about 11 cm, and a rhombic mark
E2 represents the received signal strength when the distance A
preferably is set to about 10 cm. As seen from FIG. 7, the received
signal strength increases as the distance A shortens.
[0036] The size (external dimension) of the reflecting plate 26 is
preferably larger than an area of the RFID tags 10 collected in one
lot. In the first preferred embodiment, the reflecting plate 26 is
disposed only at the ceiling surface of the box 25, and it is not
disposed at any side surface of the box 25. The reason resides in
avoiding interference between the response waves. However, the
reflecting plate 26 may be disposed at the side surface of the box
25 as well unless interference occurs.
[0037] In an inspection device according to a second preferred
embodiment, as illustrated in FIG. 8, the reader/writer 30 is used
to transmit the measurement signal, and another reader/writer 30A
for reception is disposed on the opposite side of a collective base
member 11' relative to the reader/writer 30. Thus, the plural RFID
tags 10 are inspected in a batch by using the reader/writer 30
dedicated for transmission, and using the reader/writer 30A
dedicated for reception. The inspection method is basically similar
to that described above in connection with the first preferred
embodiment.
[0038] In the second preferred embodiment, the reader/writer 30
disposed on the lower side of the RFID tags 10 is dedicated for
transmission, and the reader/writer 30A disposed on the upper side
of the RFID tags 10 is dedicated for reception. However, the
arrangement may be reversed such that the reader/writer 30A
disposed on the upper side is dedicated for transmission, and the
reader/writer 30 disposed on the lower side is dedicated for
reception.
[0039] It is to be noted that the inspection method and the
inspection device for the RFID tag, according to the present
invention, are not limited to the above-described preferred
embodiments, and they can be variously modified within the scope of
the gist of the present invention.
[0040] For example, an antenna arranged to receive the signals sent
from the RFID tags may be disposed at the position where the
reflecting plate 26 is disposed, and whether or not the RFID tags
are acceptable may be determined based on the strengths and the
number of signals received by the antenna. Furthermore, an electric
wave absorber, such as ferrite, may be disposed at the side
surfaces of the box 25 such that electric waves will not leak to
the outside.
[0041] In the preferred embodiments of the present invention, the
collective base member 11' can be separated into the plural base
films 11. Although it is not restrictive, the collective base
member 11' may be a planar member with a given area in order that a
plurality of RFID tags 10 are arranged thereon.
[0042] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing from the scope and spirit of the present invention. The
scope of the present invention, therefore, is to be determined
solely by the following claims.
* * * * *