U.S. patent application number 12/362553 was filed with the patent office on 2009-08-06 for rfid system and communication method performed by the same.
This patent application is currently assigned to Samsung Techwin Co., Ltd.. Invention is credited to Sung-ho Cho, Ki-yong Jeon, Chang-seok Yoon.
Application Number | 20090195360 12/362553 |
Document ID | / |
Family ID | 40931110 |
Filed Date | 2009-08-06 |
United States Patent
Application |
20090195360 |
Kind Code |
A1 |
Jeon; Ki-yong ; et
al. |
August 6, 2009 |
RFID SYSTEM AND COMMUNICATION METHOD PERFORMED BY THE SAME
Abstract
Provided is an RFID system and method for maintaining a constant
strength of a signal transmitted from an RFID tag to an RFID
reader, regardless of a distance between the reader and tag. The
RFID signal strength measuring reader measures a signal strength
received from the RFID tag, creates control information used to set
an amplification amount of the RFID tag by using a value of the
measured strength to include the control information in an output
signal, and sends the output signal to the RFID tag. The RFID tag,
if the signal sent from the RFID reader is received, extracts
internal information from the received signal, sends the
information to the RFID reader as an output signal, and extracts
the control information included in the signal sent from the RFID
reader to adjust a strength of the output signal according to a
value of the control information.
Inventors: |
Jeon; Ki-yong;
(Changwon-city, KR) ; Yoon; Chang-seok; (Seoul,
KR) ; Cho; Sung-ho; (Seoul, KR) |
Correspondence
Address: |
DRINKER BIDDLE & REATH LLP;ATTN: PATENT DOCKET DEPT.
191 N. WACKER DRIVE, SUITE 3700
CHICAGO
IL
60606
US
|
Assignee: |
Samsung Techwin Co., Ltd.
Changwon-city
KR
Industry - University Cooperation Foundation Hanyang
University
Seoul
KR
|
Family ID: |
40931110 |
Appl. No.: |
12/362553 |
Filed: |
January 30, 2009 |
Current U.S.
Class: |
340/10.1 |
Current CPC
Class: |
G06K 7/10366 20130101;
G08C 17/02 20130101; G06K 7/10297 20130101; H04B 5/0062
20130101 |
Class at
Publication: |
340/10.1 |
International
Class: |
H04Q 5/22 20060101
H04Q005/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2008 |
KR |
10-2008-0010367 |
Claims
1. A radio frequency identification (RFID) system comprising: an
RFID tag; and an RFID signal strength measuring reader that
measures a strength of a signal received from the RFID tag, creates
control information used to set an amplification amount of the RFID
tag by using a value of the measured strength to include the
control information in an output signal, and sends the output
signal to the RFID tag; wherein the RFID tag, if the signal sent
from the RFID reader is received, extracts internal information
from the received signal, sends the information to the RFID reader
as an output signal, and at this time, extracts the control
information included in the signal sent from the RFID reader to
adjust a strength of the output signal according to a value of the
control information.
2. The RFID system of claim 1, wherein, if the strength of the
signal transmitted from the RFID tag to the RFID reader is below a
low predetermined value, the RFID reader sets the value of the
control information so that the amplification amount of the RFID
tag is increased, and if the strength of the signal transmitted
from the RFID tag to the RFID reader is above a high predetermined
value, the RFID reader sets the value of the control information so
that the amplification amount of the RFID tag is reduced.
3. The RFID system of claim 1, wherein the strength of the signal
transmitted from the RFID tag to the RFID reader is inversely
proportional to a distance between the RFID reader and the RFID
tag.
4. The RFID system of claim 1, wherein the RFID tag comprises: an
antenna that sends a signal to the RFID reader and receives a
signal from the RFID reader; a logic unit that receives the signal
from the antenna to extract internal information from the received
signal and extracts the control information included in the signal
transmitted from the antenna; a modulating unit that modulates the
internal information; and an output unit connected to the logic
unit and the modulating unit, the output unit amplifies an output
signal of the modulating unit, adjusts an amplification amount of
the output signal of the modulating unit according to the value of
the control information to output the amplification amount as an
output signal of the RFID tag, and sends the output signal to the
antenna.
5. The RFID system of claim 4, wherein the logic unit comprises: a
signal analyzing unit that extracts and analyzes the control
information, and sends an analysis result to the output unit; a
memory storing the information; and a data processing unit that
extracts the information stored in the memory and sends the
information to the modulating unit.
6. The RFID system of claim 4, wherein the output unit comprises: a
variable amplification unit that receives an output signal of the
modulating unit and an output signal of the logic unit, and adjusts
the amplification amount of the output signal of the modulating
unit according to the value of the control information which is
output from the logic unit to output the amplification amount; and
a circulator that sends the output signal of the variable
amplification unit to the antenna, and sends the signal transmitted
from the antenna to the logic unit.
7. The RFID system of claim 4, wherein the output unit comprises an
impedance adjusting unit connected to the modulating unit and the
logic unit, and adjusts the strength of the output signal of the
modulating unit according to the value of the control information
which is output from the logic unit.
8. A communication method performed by a RFID system comprising an
RFID reader and an RFID tag, the method comprising: if a signal
sent from the RFID tag is received, then measuring a strength of
the received signal, wherein the RFID reader measures the strength;
creating control information used to set an amplification amount of
an output signal of the RFID tag by using a value of the measured
strength, wherein the RFID reader creates the control information;
and sending a signal including the control information to the RFID
tag, wherein the RFID reader sends the signal.
9. The method of claim 8, wherein, if the strength of the received
signal is below a predetermined low value, the RFID reader sets the
value of the control information so that the amplification amount
of the RFID tag is increased, and if the strength of the received
signal is above a predetermined high value, the RFID reader sets
the value of the control information so that the amplification
amount of the RFID tag is reduced.
10. A communication method performed by an RFID system comprising
an RFID reader and an RFID tag, the method comprising: if a signal
sent from the RFID reader is received, then checking if control
information used to set an amplification amount of the RFID tag is
included in the received signal, wherein the RFID tag performs
checking; if the control information is included in the received
signal, then extracting the control information and information
stored in the RFID tag and modulating the extracted information,
wherein the RFID tag performs extraction; and amplifying the
modulated signal, and adjusting and outputting an amplification
amount of the modulated signal according to a value of the control
information, wherein the RFID tag performs amplification and
adjustment.
11. The method of claim 10, wherein the control information is set
by the RFID reader to increase the amplification amount of the RFID
tag if the RFID reader and the RFID tag are a long distance from
each other, and to reduce the amplification amount of the RFID tag
if the RFID reader and the RFID tag are a short distance from each
other.
12. An RFID tag that communicates with an RFID reader wirelessly,
the RFID tag comprising: a signal strength measuring unit that
receives a signal from the RFID reader and measures a strength of
the received signal; and an output unit that receives a signal that
is output from the signal strength measuring unit, adjusts a
strength of an RFID tag signal, and sends the RFID tag signal to
the RFID reader.
13. The RFID tag of claim 12, wherein if the strength of the signal
which is input into the signal strength measuring unit is above a
predetermined high value, the output unit reduces the strength of
the input signal, and if the strength of the signal which is input
into the signal strength measuring unit is below a predetermined
low value, the output unit increases the strength of the input
signal.
14. The RFID tag of claim 12, further comprising: a logic unit
connected to the signal strength measuring unit, the logic unit
receives the signal which is output from the signal strength
measuring unit, outputs data stored in the logic unit, and sends
the data to the output unit.
15. The RFID tag of claim 14, further comprising: a modulating unit
connected between the logic unit and the output unit, the
modulating unit modulates the signal which is output from the logic
unit, and sends the modulated signal to the output unit.
16. The RFID tag of claim 12, further comprising: an antenna that
receives the signal from the RFID reader, transmits the signal to
the signal strength measuring unit, and sends the signal which is
output from the output unit to the RFID reader.
17. The RFID tag of claim 12, wherein the output unit adjusts the
strength of the output signal by adjusting an internal impedance
thereof.
18. An RFID tag that communicates with an RFID reader, the RFID tag
comprising: an antenna that receives and sends a signal from and to
the RFID reader; a signal strength measuring unit that receives the
signal from the RFID reader and measures a strength of the received
signal; a variable amplification unit that amplifies an input
signal, receives an output signal of the signal strength measuring
unit, adjusts an amplification amount of the input signal, and
outputs the adjusted signal; and a circulator connected to the
variable amplification unit, the signal strength measuring unit,
and the antenna, that transmits the signal which is output from the
variable amplification unit to the antenna, and sends the signal
which is output via the antenna to the signal strength measuring
unit.
19. The RFID tag of claim 18, wherein, if the strength of the
signal which is input to the signal strength measuring unit is
above a predetermined high value, the variable amplification unit
reduces the strength of the input signal, and if the strength of
the signal which is input to the signal strength measuring unit is
below a predetermined low value, the variable amplification unit
increases the strength of the input signal.
20. The RFID tag of claim 18, further comprising: a logic unit
connected to the signal strength measuring unit, that receives the
signal which is output from the signal strength measuring unit,
outputs data stored in the logic unit, and sends the data to the
variable amplification unit.
21. The RFID tag of claim 20, further comprising: a modulating unit
connected to the logic unit and the variable amplification unit,
that modulates the signal that is output from the logic unit, and
sends the modulated signal to the variable amplification unit.
22. A method of operating an RFID tag that communicates with an
RFID reader, the method comprising: measuring a strength of a
signal sent from the RFID reader and outputting the signal as a
control signal; extracting information stored in the RFID tag;
modulating a signal of the extracted information; and adjusting a
strength of the modulated signal according to the control signal
and sending the modulated signal to the RFID reader.
23. The method of claim 22, wherein the adjusting comprises: if the
strength of the signal transmitted from the RFID reader to the RFID
tag is below a predetermined low value, then increasing the
strength of the signal which is output from the RFID tag, and if
the strength of the signal transmitted from the RFID reader to the
RFID tag is above a high predetermined value, reducing the strength
of the signal which is output from the RFID tag.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION
[0001] This application claims the benefit of Korean Patent
Application No. 10-2008-0010367, filed on Jan. 31, 2008, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a radio frequency
identification (RFID) system that comprises an RFID reader and an
RFID tag and performs mutual communication, and a communication
method performed by the RFID system.
[0004] 2. Description of the Related Art
[0005] Radio frequency identification (RFID) technology is a radio
frequency recognition technology, which identifies an object by
using a radio frequency ranging, that is a radio frequency band,
from MHz to GHz, without contacting the object. A wide radio
frequency band makes it possible to use various types of
frequencies and utilize different frequencies according to
particular applications.
[0006] An RFID system using an RFID technology can be used to
obtain information about a product wirelessly. For this, the RFID
system includes an RFID tag that includes the information about the
product and is attached to the product and an RFID reader that
communicates with the RFID tag wirelessly and extracts information
about the product.
[0007] In more detail, the RFID tag includes an antenna and an RFID
chip, stores and renews the information sent from the RFID reader
in the RFID chip through the antenna, and sends the information
stored in the RFID chip to the RFID reader through the antenna. The
RFID tag modulates a wireless signal sent from the antenna of the
RFID reader according to the information stored in the RFID chip
and reflects the modulated wireless signal. The RFID reader reads
the information stored in the RFID chip from the reflected wireless
signal.
[0008] RFID tags are classified into active type RFID tags and
passive type RFID tags. An active RFID tag is supplied with power
from outside, and thus it uses long distance communication. On the
other hand, a passive RFID tag is supplied with power from a signal
sent from an RFID reader, and outputs a signal that significantly
changes according to a distance between the passive RFID tag and
the RFID reader.
[0009] When the passive RFID tag is nearby, a high-power carrier
wave is transmitted from the RFID reader to the passive RFID tag,
and a modulated signal is transmitted from the passive RFID tag to
the nearby RFID. On the other hand, when the passive RFID tag is
far away, a low-power carrier wave is transmitted from the RFID
reader to the passive RFID tag, and the modulated signal is
transmitted from the passive RFID tag to the far-away RFID. That
is, a signal transmitted from the passive RFID tag to the RFID
reader has a power that is inversely proportional to the distance
between the passive RFID tag and the RFID reader.
[0010] Also, since a passive type RFID reader aims at a
long-distance recognition, receiving a signal that exceeds a
certain level, e.g., from a nearby RFID tag, may cause a problem
with a recognition rate of an RFID tag signal. On an experimental
basis, a short-distance recognition was measured to be smaller than
an appropriate distance recognition. Accordingly, the RFID reader
must maintain strength of a RFID tag signal at a certain level in
order to increase a recognition rate with respect to information
stored in the RFID tag.
SUMMARY
[0011] The present invention provides an RFID system for
maintaining a constant strength of a signal transmitted from an
RFID tag to an RFID reader, regardless of a distance between the
RFID reader and the RFID tag.
[0012] The present invention also provides a communication method
performed by an RFID system for maintaining a constant strength of
a signal transmitted from an RFID tag to an RFID reader, regardless
of a distance between the RFID reader and the RFID tag.
[0013] According to an aspect of the present invention, there is
provided an RFID system comprising: an RFID reader measuring a
strength of a signal sent from an RFID tag, creating control
information which sets an amplification amount of the RFID tag by
using the measured value to include the control information in an
output signal, and sending the output signal to the RFID tag; and
an RFID tag extracting internal information when the signal sent
from the RFID reader is received, and sending the information to
the RFID reader as an output signal, and at this time, extracting
the control information comprised in the signal sent from the RFID
reader to adjust strength of the output signal according to the
control information.
[0014] According to another aspect of the present invention, there
is provided an RFID tag that communicates with an RFID reader
wirelessly, the RFID tag includes: a signal strength measuring unit
receiving a signal from the RFID reader and measuring a strength of
the received signal; and an output unit receiving a signal which is
output from the signal strength measuring unit, adjusting the
strength of an RFID tag signal, and sending the RFID tag signal to
the RFID reader.
[0015] According to another aspect of the present invention, there
is provided an RFID tag that communicates with an RFID reader, the
RFID tag includes: an antenna receiving and sending a signal from
and to the RFID reader; a signal strength measuring unit receiving
the signal from the RFID reader and measuring a strength of the
received signal; a variable amplification unit amplifying an input
signal, receiving an output signal of the signal strength measuring
unit, adjusting an amplification amount of the input signal and
outputting the adjusted signal; and a circulator connected to the
variable amplification unit, the signal strength measuring unit,
and the antenna, transmitting the signal which is output from the
variable amplification unit to the antenna, and sending the signal
which is output via the antenna to the signal strength measuring
unit.
[0016] According to another aspect of the present invention, there
is provided a communication method of an RFID system comprising an
RFID reader and an RFID tag, the method comprising: when a signal
sent from the RFID tag is received, measuring a strength of the
received signal by the RFID reader; creating control information
which sets an amplification amount of an output signal of the RFID
tag by using the measured value by the RFID reader; and sending a
signal comprising the control information to the RFID tag by the
RFID reader.
[0017] According to another aspect of the present invention, there
is provided a communication method of an RFID system comprising an
RFID reader and an RFID tag, the method comprising: when a signal
sent from the RFID reader is received, checking whether control
information which set an amplification amount of the RFID tag is
comprised or not by the RFID tag; when the control information is
SO comprised, extracting the control information and information
stored in the RFID tag to modulate them by the RFID tag; and
amplifying the modulated signal, and at this time, outputting the
modulated signal by adjusting an amplification amount of the
modulated signal according to the control information by the RFID
tag.
[0018] According to another aspect of the present invention, there
is provided a method of operating an RFID tag that communicates
with an RFID reader, the method includes: measuring a strength of a
signal sent from the RFID reader and outputting the signal as a
control signal; extracting information stored in the RFID tag;
modulating a signal of the extracted information; and adjusting
strength of the modulated signal according to the control signal
and sending the modulated signal to the RFID reader.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other features and advantages of the present
invention will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings in which:
[0020] FIG. 1 is a block diagram of an RFID system according to an
embodiment of the present invention;
[0021] FIG. 2 is a block diagram of an RFID tag of FIG. 1 according
to an embodiment of the present invention;
[0022] FIG. 3 is a block diagram of an RFID tag of FIG. 1 according
to another embodiment of the present invention;
[0023] FIG. 4 is a flowchart of a communication method performed by
an RFID system according to an embodiment of the present
invention;
[0024] FIG. 5 is a flowchart of a communication method performed by
an RFID system according to another embodiment of the present
invention.
[0025] FIG. 6 is a block diagram of the RFID tag of FIG. 1
according to another embodiment of the present invention;
[0026] FIG. 7 is a block diagram of the RFID tag of FIG. 1
according to another embodiment of the present invention; and
[0027] FIG. 8 is a flowchart of a method of operating an RFID tag
according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0028] Hereinafter, the present invention will be described in
detail by explaining exemplary embodiments of the invention with
reference to the attached drawings. Like reference numerals in the
drawings denote like elements.
[0029] FIG. 1 is a block diagram of an RFID system 100 according to
an embodiment of the present invention.
[0030] Referring to FIG. 1, the RFID system 100 includes an RFID
reader 105 and an RFID tag 101. The RFID reader 105 and the RFID
tag 101 communicate with each other wirelessly.
[0031] The RFID reader 105 sends a signal to the RFID tag 101 in
order to extract information stored in the RFID tag 101. The RFID
reader 105 measures a strength of a signal received from the RFID
tag 101, and creates control information by using the measured
value to include the control information in an output signal. The
control information includes a value which sets an amplification
amount of the signal sent from the RFID tag 101 so that strength of
the signal received by the RFID reader 105 from the RFID tag 101
becomes constant, regardless of a distance between the RFID reader
105 and the RFID tag 101.
[0032] The strength (P.sub.tagrx) of the signal transmitted from
the RFID reader 105 to the RFID tag 101 is obtained by Equation 1
below,
P tagrx = P readertx 4 .pi. R 2 1 ) ##EQU00001##
[0033] wherein, P.sub.readertx denotes the strength of the signal
sent from the RFID reader 105, and R denotes the distance between
the RFID reader 105 and the RFID tag 101.
[0034] In Equation 1, the strength of the signal transmitted from
the RFID reader 105 to the RFID tag 101 is inversely proportional
to the square of the distance between the RFID reader 105 and the
RFID tag 101.
[0035] The strength (P.sub.readerrx) of the signal transmitted from
the RFID tag 101 to the RFID reader 105 is obtained by Equation 2
below,
P readerrx = P readertx ( 4 .pi. R 2 ) 2 2 ) ##EQU00002##
[0036] wherein, it is assumed that power (P.sub.readerrx) supplied
to the RFID reader 105 is obtained by reflecting power supplied
from the RFID reader 105 to the RFID tag 101 by 100%, and R denotes
the distance between the RFID reader 105 and the RFID tag 101.
[0037] In Equation 2, the strength of the signal transmitted from
the RFID tag 101 to the RFID reader 105 is inversely proportional
to the fourth power of the distance between the RFID tag 101 and
the RFID reader 105. For example, if the strength of the signal
transmitted from the RFID reader 105 to the RFID tag 101 is 30
[dBm], the strength of the signal transmitted from the RFID tag 101
to the RFID reader 105 is significantly reduced to -60 [dBm].
[0038] The RFID reader 105 creates the control information by using
the value obtained by Equation 2 to include the control information
in the signal output by the RFID reader 105. In more detail, if the
strength of the signal which is input to the RFID reader 105 is
greater than a certain value, since the RFID reader 105 and the
RFID tag 101 are a short distance from each other, the strength of
the signal transmitted from the RFID tag 101 must be reduced.
Alternately, if the strength of the signal which is input to the
RFID tag 101 is lower than the certain value, since the RFID reader
105 and the RFID tag 101 are a long distance from each other, the
strength of the signal transmitted from the RFID tag 101 must be
increased. The certain value may be set according to an operating
rule or by a user at his or her discretion. An example of the
control information created using the above principle is shown in
Table 1 below.
TABLE-US-00001 TABLE 1 Adjustment Based on Distance Measured value
Control of information Distance between signal received included in
signal Amplification RFID reader and by RFID reader output by RFID
amount RFID tag (decimal number) reader (binary) of RFID tag Short
9-15 0001-0111 Decreased Appropriate 8 1000 Maintained at standard
level Long 1-7 1001-1111 Increased
[0039] As shown in Table 1 above, if the RFID reader 105 and the
RFID tag 101 are an appropriate distance from each other, a value
of the control information is set to "1000", and thus the signal
transmitted from the RFID tag 101 to the RFID reader 105 maintains
a standard amplification amount. If the RFID reader 105 and the
RFID tag 101 are a short distance from each other, the value of the
control information is set to "0001-0111", and thus an
amplification amount of the signal transmitted from the RFID tag
101 to the RFID reader 105 is reduced below the standard
amplification amount. If the RFID reader 105 and the RFID tag 101
are a long distance from each other, the value of the control
information is set to "1001-1111", and thus the amplification
amount of the signal transmitted from the RFID tag 101 to the RFID
reader 105 is increased above the standard amplification amount. In
this regard, when the value of the control information is between
"0111" and "0001", the RFID tag 101 may be set to more greatly
reduce the amplification amount of the signal transmitted to the
RFID reader 105 as the value is smaller. When the value of the
control information is between "1001" and "1111", the RFID tag 101
may be set to more greatly increase the amplification amount of the
signal transmitted to the RFID reader 105, as the value is
greater.
[0040] In Table 1, although the value of the control information
uses four bits using a binary code, the present invention is not
limited thereto. The value of the control information may use more
or less than four bits, or use another code besides the binary
code. Also, if the value of the control information is small, the
amplification amount of the RFID tag 101 may be set to be reduced.
If the control information value is great, the amplification amount
of the RFID tag 101 may be set to be increased.
[0041] The RFID tag 101 receives the signal from the RFID reader
105, extracts information stored therein, and sends the information
to the RFID reader 105. At this time, the RFID tag 101 adjusts an
amplification amount of an output signal according to the control
information included in the signal transmitted from the RFID reader
105.
[0042] The RFID tag 101 may be a passive type RFID tag that
operates with power supplied from the signal transmitted from the
RFID reader 105. The RFID tag 101 may also use a backscattering
method in order to perform effective communication at low cost.
[0043] The backscattering method modulates a signal by using a
carrier wave signal transmitted from the RFID reader 105 without
including an internal oscillator in the RFID tag 101. The
backscattering method enables amplitude shift key (ASK) and phase
shift key (PSK) modulations through three types of transmission
phenomenon of absorption, specular reflection, and
retro-reflection.
[0044] If a carrier wave input from an antenna of the RFID tag 101
terminates due to an impedance load such as a transmission line, a
signal is not reflected and is absorbed. When a terminal of the
transmission line is opened, a signal having the same phase is
reflected. When the transmission line is short-circuited, a signal
having an inversed phase is reflected. Although all this method
needs is a simple and low-cost circuit, since it uses a carrier
wave sent from the RFID reader 10, the strength of a signal
significantly changes according to the distance between the RFID
reader 105 and the RFID tag 101. If the strength of the signal
changes, a recognition rate of a signal received by the RFID reader
105 is reduced. To address this problem, an amplification amount of
the RFID tag 101 is adjusted according to the distance between the
RFID reader 105 and the RFID tag 101 in order to maintain a
constant strength of the signal received by the RFID reader
105.
[0045] The RFID tag 101 is attached to an object and stores an
identification (ID) of the object. The RFID reader 105 identifies
the RFID tag 101, and writes or reads additional information to or
from the RFID tag 101.
[0046] The RFID reader 105 and the RFID tag 101 uses various
international standards of communication, such as those for data
encoding, modulation, collision prevention, data decoding, and
demodulation. At present, an EPC Class 1 Generation 2[3] has been
registered in ISO/IEC, and its range of use has been
internationally increased.
[0047] The RFID tag 101 of the current embodiment is based on the
operation of the RFID system 100 according to the EPC Class 1
Generation 2[3] standard. However, the present invention is not
limited thereto, and the RFID tag 101 may be operated by using
various international standards of communication, such as data
encoding, modulation, collision prevention, data decoding,
demodulation, etc.
[0048] FIG. 2 is a block diagram of the RFID tag 101 of FIG. 1
according to an embodiment of the present invention. Referring to
FIG. 2, the RFID tag 101 includes an antenna 211, a logic unit 221,
a modulating unit 231, and an output unit 241.
[0049] The antenna 211 receives a signal sent from the RFID reader
105 (see FIG. 1) wirelessly, sends the signal to the output unit
241, and transmits a signal P4 sent from the output unit 241 to the
RFID reader 105 (see FIG. 1) wirelessly.
[0050] The logic unit 221 is connected to the antenna 211, the
modulating unit 231, and the output unit 241. The logic unit 221
inputs a signal sent from the output unit 241, outputs output
signals P1 and P2, and sends the output signals P1 and P2 to the
output unit 241 and the modulating unit 231, respectively. The
logic unit 221 includes a signal analyzing unit 223, a data
processing unit 225, and a memory 227.
[0051] The signal analyzing unit 223 receives a signal which is
input from the antenna 211 and extracts control information
included in the signal. Then, the signal analyzing unit 223
analyzes the control information, outputs an analysis result as an
amplification control signal P1, and sends the amplification
control signal P1 to the output unit 241. The signal sent from the
antenna 211 includes control information and general information.
The signal analyzing unit 223 does not analyze the general
information and outputs the general information as an output signal
P2, and sends the output signal P2 to the data processing unit
225.
[0052] The data processing unit 225 receives the output signal P2
of the signal analyzing unit 223, extracts information stored in
the memory 227, and transmits the information to the modulating
unit 231.
[0053] The memory 227 stores data. The data includes specific
information about, for example, nationality of a product to which
the RFID tag 101 is attached, origin, price, manufacturing date,
expiration date thereof, etc.
[0054] The modulating unit 231 is connected to the logic unit 221
and the output unit 241. The modulating unit 231 receives a signal
which is output from the logic unit 221, modulates the signal as a
modulated signal P3, and transmits the modulated signal P3 to the
output unit 241. The modulating unit 231 may use a frequency
modulation 0 (FM0) method in order to modulate the signal P3. The
FM0 method, which is defined by an ISO/IEC 18000-6 standard, is a
common modulation method used in a response signal transmitted from
the RFID tag 101 to the RFID reader 105 (see FIG. 1). The FM0
method has three types of A, B, and C. The types A and B must use
only FM0, and the type C uses the FM0 or a miller subcarrier. The
FM0 is easy to use because data and waveform of the FM0 are simpler
than those of the miller subcarrier.
[0055] The output unit 241 inputs the amplification control signal
P1 which is output from the logic unit 221 and the output signal P3
of the modulating unit 231, amplifies the output signal P3 of the
modulating unit 231 according to the amplification control signal
P1, and transmits the amplified signal P4 to the antenna 211. That
is, the output unit 241 adjusts an amplification amount of the
output signal P3 of the modulating unit 231 according to a value of
the amplification control signal P1. The output unit 241 adjusts
the strength of the output signal P3 by control of the
amplification control signal P1 so that the strength of the signal
transmitted from the RFID tag 101 to the RFID reader 105 (see FIG.
1) is maintained constant, regardless of a distance between the
RFID tag 101 and the RFID reader 105.
[0056] The output unit 241 includes a variable amplification unit
243 and a circulator 245.
[0057] The variable amplification unit 243 inputs the signal which
is output from the modulating unit 231 and the amplification
control signal P1 which is output from the signal analyzing unit
223. The variable amplification unit 243 receives and amplifies the
signal P3 which is output from the modulating unit 231. At this
time, the variable amplification unit 243 adjusts an amplification
amount of the signal P3 according to the value of the amplification
control signal P1. For example, if the value of the amplification
control signal P1 is smaller than the value shown in Table 1, i.e.,
"1000", the variable amplification unit 243 reduces the
amplification amount of the signal P3 and reduces the strength of
the output signal P4. If the value of the amplification control
signal P1 is greater than the value shown in Table 1, i.e., "1000",
the variable amplification unit 243 increases the amplification
amount of the signal P3 and increases the strength of the output
signal P4.
[0058] The circulator 245 is connected to the variable
amplification unit 243, the signal analyzing unit 223, and the
antenna 211, and sets a path of signals which are input and output
to and from the variable amplification unit 243, the signal
analyzing unit 223, and the antenna 211. That is, the circulator
245 sends the signal which is input from the antenna 211 to the
signal analyzing unit 223, and sends the signal which is input from
the variable amplification unit 243 to the antenna 211.
[0059] The RFID tag 101 of the present invention analyzes the
control information included in the signal sent from the RFID
reader 105 (see FIG. 1) and adjusts an amplification amount of the
variable amplification unit 243 according to the value of the
control information, so that strength of the signal P4 transmitted
from the RFID tag 101 to the RFID reader 105 (see FIG. 1) is
adjusted and output according to the distance between RFID reader
105 (see FIG. 1) and the RFID tag 101. That is, if the RFID reader
105 (see FIG. 1) and the RFID tag 101 are a long distance from each
other, the strength of the output signal P4 of the RFID tag 101 is
increased. If the RFID reader 105 (see FIG. 1) and the RFID tag 101
are a short distance from each other, the strength of the output
signal P4 of the RFID tag 101 is reduced. Accordingly, the strength
of the signal transmitted from the RFID tag 101 to the RFID reader
105 (see FIG. 1) is always constant.
[0060] FIG. 3 is a block diagram of an RFID tag 101 of FIG. 1
according to another embodiment of the present invention. Referring
to FIG. 3, the RFID tag 101 includes an antenna 311, a logic unit
321, a modulating unit 331, and an impedance adjusting unit
341.
[0061] The antenna 311 receives a signal sent from the RFID reader
105 (see FIG. 1) wirelessly, sends the signal to the logic unit
321, and sends a signal sent from the impedance adjusting unit 341
to the RFID reader 105 (see FIG. 1) wirelessly.
[0062] The logic unit 321 is connected to the antenna 311, the
modulating unit 331, and the impedance adjusting unit 341. The
logic unit 321 inputs a signal sent from the impedance adjusting
unit 341, outputs output signals P1 and P2, and sends the output
signals P1 and P2 to the impedance adjusting unit 341 and the
modulating unit 331, respectively. The logic unit 321 includes a
signal analyzing unit 323, a data processing unit 325, and a memory
327.
[0063] A signal analyzing unit 323 receives a signal sent from the
antenna 311, and extracts and analyzes control information included
in the signal. Then, the signal analyzing unit 323 outputs an
analysis result as an amplification control signal P1 and sends the
amplification control signal P1 to the impedance adjusting unit
341. The signal sent from the antenna 311 includes the control
information and general information. Accordingly, the signal
analyzing unit 323 outputs the general information as the output
signal P2, and sends the output signal P2 to the data processing
unit 325.
[0064] The data processing unit 325 receives the output signal P2
sent from the signal analyzing unit 323, extracts information
stored in the memory 327, and sends the information to the
modulating unit 331.
[0065] The memory 327 stores data. The data includes specific
information about, for example, nationality of a product to which
the RFID tag 101 is attached, origin, price, manufacturing date,
expiration date thereof, etc.
[0066] The modulating unit 331 is connected to the logic unit 321
and the impedance adjusting unit 341. The modulating unit 331
receives a signal which is output from the logic unit 321,
modulates the signal, outputs the modulated signal P3, and sends
the modulated signal P3 to the impedance adjusting unit 341. The
modulating unit 331 may use a frequency modulation 0 (FM0) method
in order to modulate the signal (P3). The FM0 method, which is
defined by an ISO/IEC 18000-6 standard, is a common modulation
method used in a response signal transmitted from the RFID tag 101
to the RFID reader 105 (see FIG. 1). The FM0 method has three types
of A, B, and C. The types A and B must use only FM0, and the type C
uses the FM0 or a miller subcarrier. The FM0 is easy to use because
data and waveform of the FM0 are simpler than those of the miller
subcarrier.
[0067] The impedance adjusting unit 341, that is an output unit,
inputs the amplification control signal P1 which is output from the
signal analyzing unit 323 and the output signal P3 which is output
from the modulating unit 331, and adjusts and outputs the strength
of the output signal P3 according to the value of the amplification
control signal P1. The impedance adjusting unit 341 adjusts the
strength of the output signal P4 by adjusting internal impedance.
That is, if the value of the amplification control signal P1 is in
the range of "0001-0111", as shown in Table 1, since the RFID
reader 105 (see FIG. 1) and the RFID tag 101 are a short distance
from each other, the strength of the signal P4 which is output from
the impedance adjusting unit 341 is reduced. Alternately, if the
value of the amplification control signal P1 is in the range of
"1001-1111", as shown Table 1, since the RFID reader 105 (see FIG.
1) and the RFID tag 101 are a long distance from each other, the
strength of the signal P4 which is output from the impedance
adjusting unit 341 is maintained at a highest level.
[0068] The RFID tag 101 of the present embodiment adjusts and
outputs the strength of the signal P4 transmitted from the
impedance adjusting unit 341 to the RFID reader 105 (see FIG. 1)
according to the value of the control information included in the
signal transmitted from the RFID reader 105 (see FIG. 1). In more
detail, if the RFID tag 101 and the RFID reader 105 (see FIG. 1)
are a short distance from each other, the impedance adjusting unit
341 reduces and outputs the strength of the output signal P4, and,
if the RFID tag 101 and the RFID reader 105 (see FIG. 1) are a long
distance from each other, the impedance adjusting unit 341
maintains and outputs the strength of the output signal P4 at the
highest level.
[0069] Accordingly, the strength of the signal transmitted from the
RFID tag 101 to the RFID reader 105 (see FIG. 1) is always
maintained constant, regardless of the distance between the RFID
tag 101 and the RFID reader 105 (see FIG. 1).
[0070] FIG. 4 is a flowchart of a communication method performed by
the RFID system 100 of FIG. 1 according to an embodiment of the
present invention. Referring to FIG. 4, the communication method
performed by the RFID system 100 includes Operations 411 through
451. The communication method performed by the RFID system 100 of
the present embodiment will be described with reference to FIG.
1.
[0071] In Operation 411, the RFID reader 105 checks if a signal
sent from the RFID tag 101 is received or not. If the signal is
received, the RFID reader 105 proceeds to a next operation, and if
not, the RFID reader 105 does not proceed to the next
operation.
[0072] In Operation 421, if the RFID reader 105 receives the signal
sent from the RFID tag 101, the RFID reader 105 measures the
strength of the received signal. In order to measure the strength
of the received signal, the RFID reader 105 may use a received
signal strength indication (RSSI) calculator.
[0073] In Operation 431, the RFID reader 105 creates control
information as shown in Table 1, according to a measurement
result.
[0074] In Operation 441, the RFID reader 105 includes the control
information in an output signal of the RFID reader 105.
[0075] In Operation 451, the RFID reader 105 sends the output
signal of the RFID reader 105 including the control information to
the RFID tag 101.
[0076] FIG. 5 is a flowchart of a communication method of the RFID
system 100 of FIG. 1 according to another embodiment of the present
invention. Referring to FIG. 5, the communication method performed
by the RFID system 100 (see FIG. 1) includes Operations 511 through
551. The communication method of the RFID system 100 (see FIG. 1)
illustrated in FIG. 5 will be described with reference to FIG.
1.
[0077] In Operation 511, the RFID tag 101 checks if a signal sent
from the RFID reader 105 is received or not. If the signal is
received, the RFID reader 105 proceeds to a next operation, and if
not, the RFID reader 105 does not proceed to the next
operation.
[0078] In Operation 521, if the RFID tag 101 receives the signal
sent from the RFID reader 105, the RFID tag 101 checks if the
control information is included in the received signal.
[0079] In Operation 531, if the control information is included in
the received signal, the RFID tag 101 extracts a value of the
control information. The RFID tag 101 extracts information stored
in the memory 227 of FIG. 2 or the memory 327 of FIG. 3 in response
to the received signal and modulates the information. If the
control information is not included in the received signal, the
RFID tag 101 creates an error signal and stops all the
operations.
[0080] In Operation 541, the RFID tag 101 amplifies the modulated
signal and adjusts an amplification amount of the modulated signal
according to the value of the control information. That is, as
shown in Table 1, if the value of the control information is great
due to the long distance between the RFID reader 105 and the RFID
tag 101, the RFID tag 101 increases the amplification amount of the
modulated signal or maintains it at the highest level. If the value
of the control information is small due to the short distance
between the RFID reader 105 and the RFID tag 101, the RFID tag 101
reduces the amplification amount of the modulated signal.
[0081] In Operation 551, the RFID tag 101 sends the amplified and
output signal to the RFID reader 105.
[0082] As illustrated in FIGS. 4 and 5, the RFID reader 105
measures strength of the signal sent from the RFID tag 101, creates
control information according to a measurement result to include
the control information in an output signal of the RFID reader 105,
and sends the control information to the RFID tag 101. The RFID tag
101 adjusts and outputs an amplification amount of the output
signal of the RFID tag 101 according to the value of the control
information included in the signal sent from the RFID reader
105.
[0083] Accordingly, the strength of the signal transmitted from the
RFID tag 101 to the RFID reader 105 is always maintained constant,
regardless of the distance between the RFID tag 101 and the RFID
reader 105.
[0084] FIG. 6 is a block diagram of the RFID tag of FIG. 1
according to another embodiment of the present invention. Referring
to FIG. 6, an RFID tag 101 includes an antenna 611, a signal
strength measuring unit 621, a logic unit 631, a modulating unit
641, and an output unit 651.
[0085] The antenna 611 receives a signal from the RFID reader 105
(see FIG. 1) wirelessly, sends the signal to the circulator 655,
and transmits a signal sent from the circulator 655 to the RFID
reader 105 (see FIG. 1) wirelessly.
[0086] The signal strength measuring unit 621 is connected to the
circulator 655, the logic unit 631, and a variable amplification
unit 653. The signal strength measuring unit 621 inputs the signal
sent from the circulator 655, outputs output signals P11 and P21,
and sends the output signals P11 and P21 to the logic unit 631 and
the variable amplification unit 653. That is, the signal strength
measuring unit 621 receives the signal from the circulator 655,
outputs the signal, and sends the signal to the logic unit 631. The
signal strength measuring unit 621 measures strength of the signal
which is output from the circulator 655 and outputs the strength
control signal P21 including a value of a measurement result, and
sends the strength control signal P21 to the variable amplification
unit 653. At this time, if the strength of the signal which is
output from the circulator 655 is greater than a predetermined
value, the strength control signal P21 has a high level voltage. If
the strength of the signal which is output from the circulator 655
is lower than the predetermined value, the strength control signal
P21 has a low level voltage. Alternately, if the strength of the
signal which is output from the circulator 655 is greater than the
predetermined value, the strength control signal P21 has a low
level voltage, and, if the strength of the signal which is output
from the circulator 655 is lower than the predetermined value, the
strength control signal P21 has a high level voltage.
[0087] The logic unit 631 includes a memory that stores specific
information about, for example, nationality of a product to which
the RFID tag 101 is attached, origin, price, manufacturing date,
expiration date thereof, etc. The logic unit 631 receives a signal
from the signal strength measuring unit 621, extracts the specific
information stored in the memory, and sends the information to the
modulating unit 641.
[0088] The modulating unit 641 is connected to the logic unit 631
and the variable amplification unit 653. The modulating unit 641
receives a signal from the logic unit 631, modulates the signal,
and sends the signal to the variable amplification unit 653. The
modulating unit 641 may use frequency modulation 0 (FM0) in order
to modulate the input signal. The FM0, which is defined by the
ISO/IEC 18000-6 standard, is a common modulation method used in a
response signal transmitted from the RFID tag 101 to the RFID
reader 105 (see FIG. 1). The FM0 has three types of A, B, and C.
The types A and B must use only FM0, and the type C uses the FM0 or
a miller subcarrier. The FM0 is easily used because data and
waveform of the FM0 are simpler than those of the miller
subcarrier.
[0089] The output unit 651 inputs the strength control signal P21
which is output from the signal strength measuring unit 621 and a
signal which is output from the modulating unit 641, adjusts the
magnitude of the signal which is output from the modulating unit
641 according to the strength control signal P21, and sends the
signal to the antenna 611.
[0090] The output unit 651 includes the variable amplification unit
653 and the circulator 655.
[0091] The variable amplification unit 653 inputs a signal which is
output from the modulating unit 641 and the strength control signal
P21 which is output from the strength control signal P21. The
variable amplification unit 653 receives the signal from the
modulating unit 641 and amplifies the signal. At this time, the
variable amplification unit 653 adjusts an amplification amount of
the signal according to the value of the strength control signal
P21, and creates an output signal. For example, if the strength
control signal P21 has a low level voltage, the variable
amplification unit 653 reduces the amplification amount to reduce
the strength of the output signal. If the strength control signal
P21 has a high level voltage, the variable amplification unit 653
increases the amplification amount to increase the strength of the
output signal.
[0092] The circulator 655 is connected to the variable
amplification unit 653, the signal strength measuring unit 621, and
the antenna 611, and sets a path of input and output signals
between the variable amplification unit 653, the signal strength
measuring unit 621, and the antenna 611. That is, the circulator
655 sends the signal which is input from the antenna 611 to the
signal strength measuring unit 621, and sends the signal which is
input from the variable amplification unit 653 to the antenna
611.
[0093] The RFID tag 101 of the present embodiment in FIG. 6
includes the signal strength measuring unit 621 and the variable
amplification unit 653. The signal strength measuring unit 621
measures the strength of the signal received through the antenna
611 and outputs the strength control signal P21 according to the
measurement result. The variable amplification unit 653 adjusts and
outputs the strength of the input signal according to the strength
control signal P21. Accordingly, the RFID tag 101 transmits the
signal, to RFID reader 105 (see FIG. 1), having the strength
adjusted according to the distance between the RFID tag 101 to RFID
reader 105 (see FIG. 1).
[0094] FIG. 7 is a block diagram of the RFID tag of FIG. 1
according to another embodiment of the present invention. Referring
to FIG. 7, the RFID tag 101 includes an antenna 711, a signal
strength measuring unit 721, a logic unit 731, a modulating unit
741, and an output unit 751.
[0095] The antenna 711 receives a signal from the RFID reader 105
(see FIG. 1) wirelessly, transmits the signal to the signal
strength measuring unit 721, and sends a signal sent from the
output unit 751 to the RFID reader 105 (see FIG. 1) wirelessly.
[0096] The signal strength measuring unit 721 is connected to the
antenna 711, the output unit 751, and the logic unit 731. The
signal strength measuring unit 721 inputs a signal via the antenna
711 and sends the signal as an output signal P11 to the logic unit
731. The signal strength measuring unit 721 measures the strength
of the signal via the antenna 711, outputs the strength control
signal P21 having a value according to a measurement result, and
sends the strength control signal P21 to the output unit 751. That
is, if the strength of the signal which is input via the antenna
711 is greater than a predetermined value, the strength control
signal P21 has a high level voltage. If the strength of the signal
which is input via the antenna 711 is lower than the predetermined
value, the strength control signal P21 has a low level voltage. To
the contrary, if the strength of the signal which is input via the
antenna 711 is greater than the predetermined value, the strength
control signal P21 has a low level voltage, and if the strength of
the signal which is input via the antenna 711 is lower than the
predetermined value, the strength control signal P21 has a high
level voltage.
[0097] The logic unit 731 includes a memory that stores specific
information about, for example, nationality of a product to which
the RFID tag 101 is attached, origin, price, manufacturing date,
expiration date thereof, etc. The logic unit 731 receives a signal
from the signal strength measuring unit 721, extracts the specific
information stored in the memory, and sends the information to the
modulating unit 741.
[0098] The modulating unit 741 is connected to the logic unit 731
and the output unit 751. The modulating unit 741 receives a signal
from the logic unit 731, modulates the signal, and sends the signal
to the output unit 751. The modulating unit 741 may use FM0 in
order to modulate the input signal. The FM0, which is defined by
the ISO/IEC 18000-6 standard, is a common modulation method used in
a response signal transmitted from the RFID tag 101 to the RFID
reader 105 (see FIG. 1). The FM0 has three types of A, B, and C.
The types A and B must use only FM0, and the type C uses the FM0 or
a miller subcarrier. The FM0 is easily used because data and
waveform of the FM0 are simpler than those of the miller
subcarrier.
[0099] The output unit 751 inputs the strength control signal P21
which is output from the signal strength measuring unit 721 and a
signal which is output from the modulating unit 741, adjusts the
magnitude of the signal which is output from the modulating unit
741 in response to the strength control signal P21, and sends the
signal to the antenna 711. The output unit 751 includes an
impedance adjusting unit for adjusting internal impedance to adjust
the strength of the input signal.
[0100] As described above, the RFID tag 101 of the present
invention in FIG. 7 includes the signal strength measuring unit 721
and the output unit 751. The signal strength measuring unit 721
measures the strength of the signal received through the antenna
711, outputs the strength control signal P21 in response to the
measurement result. The output unit 751 adjusts the strength of the
input signal according to the strength control signal. Accordingly,
the RFID tag 101 transmits the signal to RFID reader 105 (see FIG.
1) in which the signal is adjusted according to the magnitude of RF
power according to the distance between the RFID tag 101 to RFID
reader 105 (see FIG. 1).
[0101] The RFID tag 101 and the RFID reader 105 (see FIG. 1)
constitute an RFID system. The RFID tag 101 is attached to an
object and stores identification (ID) of the object. The RFID
reader 105 identifies the RFID tag 101, and writes or reads
additional information to or from the RFID tag 101.
[0102] Communication between the RFID reader 105 (see FIG. 1) and
the RFID tag 101 uses various international standards of
communication, such as data encoding, modulation, collision
prevention, data decoding, and demodulation. At present, the EPC
Class 1 Generation 2[3] has been registered in the ISO/IEC, and its
range of use has been internationally increased.
[0103] The RFID tag 101 of the current embodiment is based on the
operation of the RFID system 100 according to the EPC Class 1
Generation 2[3] standard. However, the present invention is not
limited thereto, and the RFID tag 101 may be operated by using
various international standards of communication, such as data
encoding, modulation, collision prevention, data decoding,
demodulation, etc.
[0104] FIG. 8 is a flowchart of a method of operating an RFID tag
according to an embodiment of the present invention. Referring to
FIG. 8, the method of operating the RFID tag 101 (see FIGS. 6 and
7) of the present invention includes Operations 811 through 871.
The method of operating the RFID tag 101 illustrated in FIG. 8 will
be described with reference to FIGS. 6 and 7.
[0105] In Operation 811, the signal strength measuring unit 621 or
721 receives a signal via the antenna 611 or 711. The signal
received via the antenna 611 or 711 is a signal sent from the RFID
reader 105 (see FIG. 1) wirelessly.
[0106] In Operation 821, the signal strength measuring unit 621 or
721 measures strength of the received signal, outputs the signal as
the strength control signal P21, and sends the signal to the output
unit 651 or 751. Also, the signal strength measuring unit 621 or
721 sends the received signal to the logic unit 631 or 731.
[0107] In Operation 831, if the logic unit 631 or 731 receives the
signal from the signal strength measuring unit 621 or 721, the
logic unit 631 or 731 extracts stored data and sends the data to
the modulating unit 641 or 741.
[0108] In Operation 841, the modulating unit 641 or 741 modulates
the signal which is output from the logic unit 631 or 731 and sends
the modulated signal to the output unit 651 or 751.
[0109] In Operation 851, if the output unit 651 or 751 receives the
modulated signal which is output from the logic unit 631 or 731,
the output unit 651 or 751 adjusts the strength of the modulated
signal in response to the strength control signal P21 which is
output from the signal strength measuring unit 621 or 721. That is,
if the strength of the signal transmitted from the RFID reader 105
(see FIG. 1) to the RFID tag 101 is low due to the long distance
between RFID tag 101 and the RFID reader 105 (see FIG. 1), the RFID
tag 101 increases the strength of the output signal. If the
strength of the signal transmitted from the RFID reader 105 (see
FIG. 1) to the RFID tag 101 is high due to the short distance
between RFID tag 101 and the RFID reader 105 (see FIG. 1), the RFID
tag 101 reduces the strength of the output signal.
[0110] In Operation 861, the output unit 651 or 751 compares the
adjusted signal with a predetermined value.
[0111] In Operation 871, if a value of strength of the adjusted
signal does not exceed the predetermined value, the output unit 651
or 751 sends the value to the RFID reader 105 (see FIG. 1) through
the antenna 611 or 711. If the value of the strength of the
adjusted signal exceeds the predetermined value, Operation 851 is
performed.
[0112] As described above, according to the present invention, the
RFID tag 101 in FIGS. 6 and 7 measures the strength of the signal
which is received through the antenna 611 or 711, outputs the
strength control signal P21 according to the measurement result,
and adjusts and outputs the strength of the signal which is output
from the RFID tag 101 according to the strength control signal P21.
Accordingly, the RFID tag 101 transmits the signal to the RFID
reader 105 (see FIG. 1) in which the strength of the signal is
adjusted according to the magnitude of RF power according to the
distance between the RFID tag 101 to RFID reader 105 (see FIG.
1).
[0113] According to various embodiments of the present invention,
the RFID reader 105 (see FIG. 1) measures strength of a signal sent
from the RFID tag 101 (see FIG. 1), creates control information
according to a measurement result to include the control
information in an output signal of the RFID reader 105 (see FIG.
1), and sends the control information to the RFID tag 101 (see FIG.
1). The RFID tag 101 (see FIG. 1) adjusts and outputs an
amplification amount of an output signal of the RFID tag 101 (see
FIG. 1) according to a value of the control information included in
the signal sent from the RFID reader 105 (see FIG. 1). Accordingly,
the strength of the signal transmitted from the RFID tag 101 (see
FIG. 1) to the RFID reader 105 (see FIG. 1) is always maintained
constant, regardless of the distance between the RFID tag 101 (see
FIG. 1) and the RFID reader 105 (see FIG. 1), thereby increasing a
recognition rate of the RFID reader 105 (see FIG. 1) with respect
to information stored in the RFID tag 101 (see FIG. 1).
[0114] The system or systems may be implemented on any form of
computer or computers, and can include functional programs, codes,
and code segments. Any of the computers may comprise a processor, a
memory for storing program data and executing it, a permanent
storage such as a disk drive, a communications port for handling
communications with external devices, and user interface devices,
including a display, keyboard, mouse, etc. When software modules
are involved, these software modules may be stored as program
instructions or computer readable codes executable on the processor
on a computer-readable media such as read-only memory (ROM),
random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks,
optical data storage devices, and carrier waves (such as data
transmission through the Internet). The computer readable recording
medium can also be distributed over network coupled computer
systems so that the computer readable code is stored and executed
in a distributed fashion. This media can be read by the computer,
stored in the memory, and executed by the processor.
[0115] For the purposes of promoting an understanding of the
principles of the invention, reference has been made to the
preferred embodiments illustrated in the drawings, and specific
language has been used to describe these embodiments. However, no
limitation of the scope of the invention is intended by this
specific language, and the invention should be construed to
encompass all embodiments that would normally occur to one of
ordinary skill in the art.
[0116] The present invention may be described in terms of
functional block components and various processing steps. Such
functional blocks may be realized by any number of hardware and/or
software components configured to perform the specified functions.
For example, the present invention may employ various integrated
circuit components, e.g., memory elements, processing elements,
logic elements, look-up tables, and the like, which may carry out a
variety of functions under the control of one or more
microprocessors or other control devices. Similarly, where the
elements of the present invention are implemented using software
programming or software elements the invention may be implemented
with any programming or scripting language such as C, C++, Java,
assembler, or the like, with the various algorithms being
implemented with any combination of data structures, objects,
processes, routines or other programming elements. Furthermore, the
present invention could employ any number of conventional
techniques for electronics configuration, signal processing and/or
control, data processing and the like. The words "mechanism" and
"element" are used broadly and are not limited to mechanical or
physical embodiments, but can include software routines in
conjunction with processors, etc.
[0117] The particular implementations shown and described herein
are illustrative examples of the invention and are not intended to
otherwise limit the scope of the invention in any way. For the sake
of brevity, conventional electronics, control systems, software
development and other functional aspects of the systems (and
components of the individual operating components of the systems)
may not be described in detail. Furthermore, the connecting lines,
or connectors shown in the various figures presented are intended
to represent exemplary functional relationships and/or physical or
logical couplings between the various elements. It should be noted
that many alternative or additional functional relationships,
physical connections or logical connections may be present in a
practical device. Moreover, no item or component is essential to
the practice of the invention unless the element is specifically
described as "essential" or "critical".
[0118] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural. Furthermore, recitation of ranges
of values herein are merely intended to serve as a shorthand method
of referring individually to each separate value falling within the
range, unless otherwise indicated herein, and each separate value
is incorporated into the specification as if it were individually
recited herein. Finally, the steps of all methods described herein
can be performed in any suitable order unless otherwise indicated
herein or otherwise clearly contradicted by context.
[0119] Numerous modifications and adaptations will be readily
apparent to those skilled in this art without departing from the
spirit and scope of the present invention.
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