U.S. patent application number 14/588095 was filed with the patent office on 2015-05-21 for multi-mode rfid tag architecture.
This patent application is currently assigned to BROADCOM CORPORATION. The applicant listed for this patent is BROADCOM CORPORATION. Invention is credited to Ahmadreza Rofougaran, Maryam Rofougaran, Amin Shameli.
Application Number | 20150137949 14/588095 |
Document ID | / |
Family ID | 40327143 |
Filed Date | 2015-05-21 |
United States Patent
Application |
20150137949 |
Kind Code |
A1 |
Rofougaran; Ahmadreza ; et
al. |
May 21, 2015 |
MULTI-MODE RFID TAG ARCHITECTURE
Abstract
A multi-mode RFID tag includes a power generating and signal
detection module, a baseband processing module, a transmit section,
a configurable coupling circuit, and an antenna section. In near
field mode, the configurable coupling circuit is operable to couple
the transmit section to a coil or inductor in the configurable
coupling circuit to transmit an outbound transmit signal using
electromagnetic or inductive coupling to an RFID reader. In far
field mode, the configurable coupling circuit is operable to couple
the transmit section to the antenna section, and the multi-mode
RFID tag then utilizes a back-scattering RF technology to transmit
the outbound transmit signal to RFID readers.
Inventors: |
Rofougaran; Ahmadreza;
(Newport Coast, CA) ; Rofougaran; Maryam; (Rancho
Palos Verdes, CA) ; Shameli; Amin; (Irvine,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BROADCOM CORPORATION |
IRVINE |
CA |
US |
|
|
Assignee: |
BROADCOM CORPORATION
IRVINE
CA
|
Family ID: |
40327143 |
Appl. No.: |
14/588095 |
Filed: |
December 31, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14089164 |
Nov 25, 2013 |
8941497 |
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14588095 |
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13855150 |
Apr 2, 2013 |
8643490 |
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14089164 |
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13539652 |
Jul 2, 2012 |
8432285 |
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13855150 |
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13234632 |
Sep 16, 2011 |
8237566 |
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13539652 |
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12695169 |
Jan 28, 2010 |
8022825 |
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13234632 |
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11928544 |
Oct 30, 2007 |
7679514 |
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12695169 |
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60921221 |
Mar 30, 2007 |
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60932411 |
May 31, 2007 |
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Current U.S.
Class: |
340/10.1 |
Current CPC
Class: |
H04B 5/0012 20130101;
H04B 5/0087 20130101; G06K 7/0008 20130101; G06K 7/10198 20130101;
G06K 19/073 20130101; G06K 19/0724 20130101; H04B 5/0062 20130101;
G06K 19/07766 20130101 |
Class at
Publication: |
340/10.1 |
International
Class: |
G06K 7/10 20060101
G06K007/10 |
Claims
1. A transceiver, comprises: a circuit operable to format an
outbound signal in a near field mode and in an RF mode, wherein the
circuit is configured to format the outbound signal using a first
protocol when in the near field mode and format the outbound signal
using a second protocol when in the RF mode; and a transmitter
operable to generate an outbound transmit signal and transmit the
outbound transmit signal at a first frequency in the near field
mode and at a second frequency in the RF mode.
2. The transceiver of claim 1, wherein the first frequency in the
near field mode includes at least one of: approximately 135 KHz or
less; or approximately 13.56 MHz.
3. The transceiver of claim 2, wherein the second frequency in the
RF mode includes at least one of: approximately 2.45 GHz frequency;
approximately 860 MHZ to 930 MHz; or approximately 433.92 MHz.
4. The transceiver of claim 1, wherein the transmitter includes: a
coupling circuit operable to couple the transmitter to a first
circuit to transmit the outbound transmit signal using inductive
coupling in the near field mode and operable to couple the
transmitter to a second circuit to transmit the outbound transmit
signal as an RF signal in the far field mode.
5. The transceiver of claim 1, further comprising: a power
generating module including a power supply.
6. The transceiver of claim 1, comprising: a power generating
module, wherein the power generating module is operable to convert
an inbound receive signal from an RFID interrogator into a supply
voltage.
7. The transceiver of claim 1, wherein the first protocol is a
first ISO standard defined protocol and wherein the second protocol
is a second ISO standard defined protocol.
8. The transceiver of claim 1, wherein the transceiver supports one
or more of: amplitude shift keying (ASK) modulation, biphase space
modulation or FM0 encoding.
9. A radio frequency identification (RFID) device, comprises: a
transceiver operable to receive an inbound receive signal in a near
field mode and an RF mode; at least one circuit configured to
decode the inbound receive signal using a first protocol when in
the near field mode and decode the inbound receive signal using a
second protocol when in the RF mode.
10. The RFID device of claim 9, wherein the first protocol is a
first encoding protocol and wherein the second protocol is a second
encoding protocol.
11. The RFID device of claim 9, wherein the first protocol is a
first ISO standard defined protocol and wherein the second protocol
is a second ISO standard defined protocol.
12. The RFID device of claim 9, wherein the transceiver further
comprises: a coupling circuit operable to couple the RFID device to
a first antenna circuit to receive the inbound receive signal using
inductive coupling in the near field mode and operable to couple
the RFID device to a second antenna circuit to receive the inbound
receive signal as an RF signal in the far field mode.
13. The RFID device of claim 9, comprising: a power generating
module operable in an active mode, wherein the power generating
module includes a power supply.
14. The RFID device of claim 9, comprising: a power generating
module operable in a passive mode, wherein the power generating
module is operable to convert an inbound receive signal from an
RFID interrogator into a supply voltage.
15. A transceiver, comprises: a circuit operable to encode an
outbound signal in a near field mode and in an RF mode, wherein the
circuit is configured to format the outbound signal using a first
data encoding protocol in a near field mode and a second data
encoding protocol in an RF mode.
16. The transceiver of claim 15, further comprising: a transmitter
operable to generate a transmit signal using the outbound signal
and transmit the transmit signal at a first frequency in the near
field mode and at a second frequency in the RF mode.
17. The transceiver of claim 16, further comprising: wherein the
transmitter is further operable to receive a first command in the
near field mode; and wherein in response to the first command, the
circuit is operable to generate the outbound signal using the first
encoding protocol.
18. The transceiver of claim 17, further comprising: wherein the
transmitter is further operable to receive a second command in the
RF mode; and in response to the second command, the circuit is
operable to generate the outbound signal using the second encoding
protocol and transmitting the outbound transmit signal in the RF
mode.
19. The transceiver of claim 15, wherein the first frequency in the
near field mode includes at least one of: approximately 135 KHz or
less; or approximately 13.56 MHz.
20. The transceiver of claim 19, wherein the second frequency in
the RF mode includes at least one of: approximately 2.45 GHz
frequency; approximately 860 MHZ to 930 MHz; or approximately
433.92 MHz.
Description
CROSS REFERENCE TO RELATED PATENTS
[0001] The present U.S. Utility patent application claims priority
pursuant to 35 U.S.C. .sctn.120 as a continuation of U.S. Utility
application Ser. No. 14/089,164, entitled "Multi-Mode RFID Tag
Architecture", filed Nov. 25, 2013, which is a continuation of U.S.
Utility application Ser. No. 13/855,150, entitled "Multi-Mode RFID
Tag Architecture", filed Apr. 2, 2013, now U.S. Pat. No. 8,643,490,
which is a continuation of U.S. Utility application Ser. No.
13/539,652, entitled "Multi-Mode RFID Tag Architecture", filed Jul.
2, 2012, now U.S. Pat. No. 8,432,285, which is a continuation of
U.S. Utility application Ser. No. 13/234,632, entitled "Multi-Mode
RFID Tag Architecture", filed Sep. 16, 2011, now U.S. Pat. No.
8,237,566, which is a continuation of U.S. Utility application Ser.
No. 12/695,169, entitled "Multi-Mode RFID Tag Architecture", filed
Jan. 28, 2010, now U.S. Pat. No. 8,022,825, which is a continuation
of U.S. Utility application Ser. No. 11/928,544, entitled
"Multi-Mode RFID Tag Architecture", filed Oct. 30, 2007, now U.S.
Pat. No. 7,679,514, which claims priority pursuant to 35 U.S.C.
.sctn.119(e) to U.S. Provisional Application No. 60/921,221,
entitled "RFID System", filed Mar. 30, 2007; and U.S. Provisional
Application No. 60/932,411, entitled "RFID System", filed Mar. 31,
2007, all of which are hereby incorporated herein by reference in
their entirety and made part of the present U.S. Utility patent
application for all purposes.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT
DISC
[0003] Not applicable.
BACKGROUND OF THE INVENTION
[0004] 1. Technical Field of the Invention
[0005] This invention relates generally to communication systems
and more particularly to RFID systems.
[0006] 2. Description of Related Art
[0007] A radio frequency identification (RFID) system generally
includes a reader, also known as an interrogator, and a remote tag,
also known as a transponder. Each tag stores identification or
other data for use in identifying a person, item, pallet or other
object or data related to a characteristic of a person, item,
pallet or other object. RFID systems may use active tags that
include an internal power source, such as a battery, and/or passive
tags that do not contain an internal power source, but instead are
remotely powered by the reader.
[0008] Communication between the reader and the remote tag is
enabled by radio frequency (RF) signals. In general, to access the
identification data stored on an RFID tag, the RFID reader
generates a modulated RF interrogation signal designed to evoke a
modulated RF response from a tag. The RF response from the tag
includes the coded data stored in the RFID tag. The RFID reader
decodes the coded data to identify or determine the characteristics
of a person, item, pallet or other object associated with the RFID
tag. For passive tags without a battery or other power source, the
RFID reader also generates an unmodulated, continuous wave (CW)
signal to activate and power the tag during data transfer. Thus,
passive tags obtain power from transmissions of the RFID reader.
Active tags include a battery and have greater ability to power
transceivers, processer, memory and other on-tag devices.
[0009] RFID systems typically employ either far field or near field
technology. In far field technology, the distance between the
reader and the tag is great compared to the wavelength of the
carrier signal. Typically, far field technology uses carrier
signals in the ultra high frequency or microwave frequency ranges.
In far-field applications, the RFID reader generates and transmits
an RF signal via an antenna to all tags within range of the
antenna. One or more of the tags that receive the RF signal
responds to the reader using a backscattering technique in which
the tags modulate and reflect the received RF signal.
[0010] In near-field technology, the operating distance is usually
less than one wavelength of the carrier signal. Thus, the reading
range is approximately limited to 20 cm or less depending on the
frequency. In near field applications, the RFID reader and tag
communicate via electromagnetic or inductive coupling between the
coils of the reader and the tag. Typically, the near field
technology uses carrier signals in the low frequency range. For the
tag coil antennas, RFID tags have used a multilayer coil (e.g., 3
layers of 100-150 turns each) wrapped around a metal core at lower
frequencies of 135 KHz. Sometimes, at higher frequency of 13.56
MHz, RFID tags have used a planar spiral coil inductor with 5-7
turns over a credit-card-sized form factor. Such tag coil antennas
are large in comparison to the other modules of the RFID tag and
are not able to be integrated on a chip, such as a complementary
metal-oxide-semiconductor (CMOS), bipolar complementary
metal-oxide-semiconductor (BiCMOS) or gallium arsenide (GaAs)
integrated circuit, with other modules of the RFID tag.
[0011] The International Organization for Standardization (ISO) has
developed an RFID standard called the ISO 18000 series. The ISO
18000 series standard describes air interface protocols for RFID
systems especially in applications used to track items in a supply
chain. The ISO 18000 series has seven parts to cover the major
frequencies used in RFID systems around the world. The seven parts
are: [0012] 18000-1: Generic parameters for air interfaces for
globally accepted frequencies; [0013] 18000-2: Air interface for
below 135 KHz; [0014] 18000-3: Air interface for 13.56 MHz; [0015]
18000-4: Air interface for 2.45 GHz; [0016] 18000-5: Air interface
for 5.8 GHz; [0017] 18000-6: Air interface for 860 MHz to 930 MHz;
[0018] 18000-7: Air interface at 433.92 MHz.
[0019] According to the ISO 18000-2 and 18000-3 parts of the ISO
18000 series, near-field technology with magnetic/inductive
coupling has an air interface protocol at low frequency (LF) of 135
KHz or less or at 13.56 high frequency (HF). ISO 18000-3 defines
two modes. In mode 1, the tag to reader data rate is 26.48 kbps
while mode 2 is a high speed interface of 105.9375 kbps on each of
8 channels. The communication protocol used by the reader and the
tag is typically a load modulation technique.
[0020] Far field technology with RF backscatter coupling has three
ISO defined air interfaces at 2.45 GHz microwave frequency
according to ISO 18000-5, 860 MHZ to 930 MHz ultra high frequency
(UHF) range according to ISO 18000-6 and 433.92 MHz UHF according
to ISO 18000-7. For UHF at 860-930 MHz, the ISO 18000-6 has defined
two tag types, Type A and Type B with a tag to reader link defined
as including 40 kbps data rate, Amplitude Shift Keying (ASK)
modulation, and biphase-space or FM0 encoding of data.
[0021] In addition, the EPCglobal Class 1, Generation 2 standard
defines a tag standard using UHF with a tag to reader link of 40 to
640 kbps, ASK or Phase Shift Keying (PSK) modulation and data
encoding of FM0 or Miller-modulated subcarrier.
[0022] Generally, tags employing near field technology operating at
LF or HF have been used in applications involving item-level
tagging for inventory control in the supply chain management or
applications involving short range reads such as smart cards or
vicinity credit cards, e.g. for access control or monetary use,
passports, money bills authentication, bank documents, etc. Such
applications do not need long range reads of the tags but may need
more security provided by near field technology. In addition, near
field technology is known for better performance on tags near
fluids, such as fluid medications, wherein far field RF coupling
tends to incur interference from the fluids.
[0023] Tags employing far field technology RF coupling at microwave
or UHF have been used in applications involving shipping units such
as pallets or carton level tracking or other applications needing
long-distance reads.
[0024] These different types of technology and the number of
different RFID standards, each defining a different protocol for
enabling communication between the reader and the tag, has
inhibited the wide spread use of RFID tags for multiple
applications. Therefore, a need exists for a highly integrated,
low-cost RFID tag. In addition, a need exists for a multi-standard,
multi-technology RFID tag.
BRIEF SUMMARY OF THE INVENTION
[0025] The present invention is directed to apparatus and methods
of operation that are further described in the following Brief
Description of the Drawings, the Detailed Description of the
Invention, and the claims. Other features and advantages of the
present invention will become apparent from the following detailed
description of the invention made with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0026] FIG. 1 is a schematic block diagram of an embodiment of an
RFID system in accordance with the present invention;
[0027] FIG. 2 is a schematic block diagram of an embodiment of a
multi-mode RFID tag in accordance with the present invention;
[0028] FIG. 3 is a schematic block diagram of a configurable
coupling circuit in one embodiment of a multimode RFID tag in
accordance with the present invention;
[0029] FIG. 4 is a schematic block diagram of another embodiment of
a multimode RFID tag in accordance with the present invention;
[0030] FIG. 5 is a schematic block diagram of coil antennas in one
embodiment of a multimode RFID tag and RFID reader in accordance
with the present invention; and
[0031] FIG. 6 is a schematic block diagram of magnetic coupling
between a multi-mode RFID tag and RFID reader in one embodiment in
accordance with the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0032] FIG. 1 is a schematic block diagram of an RFID (radio
frequency identification) system that includes a computer/server
12, a plurality of RFID readers 14-18 and a plurality of RFID tags
20-30. The RFID tags 20-30 may each be associated with a particular
object for a variety of purposes including, but not limited to,
tracking inventory, tracking status, location determination,
assembly progress, et cetera. The RFID tags may be active devices
that include internal power sources or passive devices that derive
power from the RFID readers 14-18.
[0033] Each RFID reader 14-18 wirelessly communicates with one or
more RFID tags 20-30 within its coverage area. For example, RFID
tags 20 and 22 may be within the coverage area of RFID reader 14,
RFID tags 24 and 26 may be within the coverage area of RFID reader
16, and RFID tags 28 and 30 may be within the coverage area of RFID
reader 18. In one mode of operation, the RF communication scheme
between the RFID readers 14-18 and RFID tags 20-30 is a backscatter
coupling technique using far field technology whereby the RFID
readers 14-18 request data from the RFID tags 20-30 via an RF
signal, and the RF tags 20-30 respond with the requested data by
modulating and backscattering the RF signal provided by the RFID
readers 14-18. In another mode of operation, the RF communication
scheme between the RFID readers 14-18 and RFID tags 20-30 is a
magnetic or inductive coupling technique using near field
technology whereby the RFID readers 14-18 magnetically or
inductively couple to the RFID tags 20-30 to access the data on the
RFID tags 20-30. Thus, in one embodiment of the current invention,
the RFID tags 20-30 may communicate in a far field mode to an RFID
reader 14-18 with such capabilities and in a near field mode to an
RFID reader 14-18 with such capabilities.
[0034] The RFID readers 14-18 collect data as may be requested from
the computer/server 12 from each of the RFID tags 20-30 within its
coverage area. The collected data is then conveyed to
computer/server 12 via the wired or wireless connection 32 and/or
via peer-to-peer communication 34. In addition, and/or in the
alternative, the computer/server 12 may provide data to one or more
of the RFID tags 20-30 via the associated RFID reader 14-18. Such
downloaded information is application dependent and may vary
greatly. Upon receiving the downloaded data, the RFID tag 20-30 can
store the data in a non-volatile memory therein.
[0035] As indicated above, the RFID readers 14-18 may optionally
communicate on a peer-to-peer basis such that each RFID reader does
not need a separate wired or wireless connection 32 to the
computer/server 12. For example, RFID reader 14 and RFID reader 16
may communicate on a peer-to-peer basis utilizing a back scatter
technique, a wireless LAN technique, and/or any other wireless
communication technique. In this instance, RFID reader 16 may not
include a wired or wireless connection 32 to computer/server 12. In
embodiments in which communications between RFID reader 16 and
computer/server 12 are conveyed through the wired or wireless
connection 32, the wired or wireless connection 32 may utilize any
one of a plurality of wired standards (e.g., Ethernet, fire wire,
et cetera) and/or wireless communication standards (e.g., IEEE
802.11x, Bluetooth, et cetera).
[0036] As one of ordinary skill in the art will appreciate, the
RFID system of FIG. 1 may be expanded to include a multitude of
RFID readers 14-18 distributed throughout a desired location (for
example, a building, office site, et cetera) where the RFID tags
may be associated with access cards, smart cards, mobile phones,
personal digital assistants, laptops, personal computers, inventory
items, pallets, cartons, equipment, personnel, et cetera. In
addition, it should be noted that the computer/server 12 may be
coupled to another server and/or network connection to provide wide
area network coverage.
[0037] FIG. 2 is a schematic block diagram of an embodiment of a
multi-mode RFID tag 38 which can be used as one of the RFID tags
20-30 in FIG. 1. The multi-mode RFID tag 38 is operable to
communicate in a far field mode to an RFID reader 14-18 and in a
near field mode to an RFID reader 14-18. The multi-mode RFID tag 38
includes a power generating and signal detection module 40, a
baseband processing module 42, a transmit section 44, a
configurable coupling circuit 46, and an antenna section 48. The
multi-mode RFID tag 38 may be an active tag and include a battery
41. If an active tag, the battery 41 may replace or assist the
power generating function of the power generating and signal
detection module 40 to power the baseband processing module 42,
transmit section 44 and configurable coupling circuit 46. If the
multi-mode RFID tag 38 is a passive tag, no battery 41 is
present.
[0038] The power generating and signal detection module 40,
baseband processing module 42 and transmit section 44 may be a
single processing device or a plurality of processing devices. Such
a processing device may be a microprocessor, micro-controller,
digital signal processor, microcomputer, central processing unit,
field programmable gate array, programmable logic device, state
machine, logic circuitry, analog circuitry, digital circuitry,
and/or any device that manipulates signals (analog and/or digital)
based on hard coding of the circuitry and/or operational
instructions. One or more of the modules may have an associated
memory element, which may be a single memory device, a plurality of
memory devices, and/or embedded circuitry of the module. Such a
memory device may be a read-only memory, random access memory,
volatile memory, non-volatile memory, static memory, dynamic
memory, flash memory, cache memory, and/or any device that stores
digital information. Note that when the module implements one or
more of its functions via a state machine, analog circuitry,
digital circuitry, and/or logic circuitry, the memory element
storing the corresponding operational instructions may be embedded
within, or external to, the circuitry comprising the state machine,
analog circuitry, digital circuitry, and/or logic circuitry.
Further note that, the memory element stores, and the module
executes, hard coded and/or operational instructions corresponding
to at least some of the steps and/or functions illustrated in FIGS.
1-6.
[0039] In an embodiment, the antenna section 48 is a dipole type
antenna operable at microwave or UHF ranges. Folded dipoles or
half-wave dipoles can be used or other dipole type antennas that
can be bent or meandered with capacitive tip-loading or bowtie-like
broadband structures are also used for compact applications. In
general, the antenna section 48 can be one of several types of
antennas optimized for the desired frequency of operation and
application.
[0040] In operation, the configurable coupling circuit 46 is
operable to couple the power generating and signal detection module
40 to the antenna section 48 in a far field mode or to couple the
power generating and signal detection module 40 to an inductor or
coil antenna in the configurable coupling circuit 46 in a near
field mode, as explained in more detail below. In either mode, the
configurable coupling circuit 46 is operable to transmit an inbound
receive signal 50 to the power generating and signal detection
module 40. In a passive embodiment of multimode RFID tag 38, the
RFID reader 14-18 first generates an unmodulated, continuous wave
(CW) signal to activate and power the tag. The power generating and
signal detection module 40 converts this type of CW unmodulated
inbound receive signal 50 into a supply voltage. The power
generating circuit signal detection module 40 stores the supply
voltage and provides it to the other modules for operation.
[0041] The RFID reader 14-18 then transmits a modulated, encoded
interrogation inbound receive signal 50. The power generating and
signal detection module 40 receives the inbound receive signal 50
from the configurable coupling circuit 46. The power generating and
signal detection module 40 demodulates the inbound receive signal
50 to recover the encoded data 52. Depending on the RFID reader
14-18 and mode of operation, the inbound receive signal 50 may be
modulated using Amplitude Shift Keying (ASK) or Phase Shift Keying
(PSK) or other type of modulation. In an embodiment, the power
generating and signal detection module 40 is operable to demodulate
the inbound receive signal 50 using one or more types of
demodulation techniques to recover the encoded data 52 from the
inbound receive signal 50. The power generating and signal
detection module 40 transmits the recovered encoded data 52 to the
baseband processing module 42.
[0042] The baseband processing module 42 receives the encoded data
52 and decodes the encoded data 52 using one or more protocols.
Different data encoding protocols may be defined for signals in
near field mode and signals in far field mode. For example, in near
field mode, a first data encoding protocol may be used by the
baseband processing module 42 for decoding data while a second data
encoding protocol may be used by the baseband processing module 42
for decoding data in far field mode. For instance, Manchester
encoding may be used when in near field mode and Miller-modulated
subcarrier coding and/or biphase-space encoding may be used when in
the far field mode. Alternatively, the baseband processing module
42 may use the same data encoding protocol for near field mode and
far field mode.
[0043] In an embodiment, the baseband processing module 42 is
programmed with multiple encoding protocols to be operable to
decode the encoded data 52 in accordance with different protocols.
Thus, the baseband processing module 42 is operable to decode the
encoded data 52 using different encoding protocols when necessary
in either near field or far field mode. For example, when operating
in near field mode, the baseband processing module 42 may attempt
to decode the encoded data 52 using a first protocol typical in
near field operations, such as Manchester coding. If such decoding
is unsuccessful, the baseband processing module is operable to
attempt decoding the encoded data 52 with a next protocol until the
encoded data 52 is decoded. Similarly, when operating in far field
mode, the baseband processing module 42 may attempt to decode the
encoded data 52 using a second protocol typical in far field
operations, such as Miller-modulated subcarrier coding and
biphase-space encoding. If such decoding is unsuccessful, the
baseband processing module is operable to attempt decoding the
encoded data 52 with a next protocol until the encoded data is
decoded.
[0044] Once decoded, the baseband processing module 42 processes
the decoded data to determine a command or commands contained
therein. The command may be to store data, update data, reply with
stored data, verify command compliance, acknowledgement, change
mode of operation, etc. If the command(s) requires a response, the
baseband processing module 42 determines the response data and
encodes the response data into outbound encoded data 54.
Preferably, the baseband processing module 42 encodes the data for
the response using the same encoding protocol used to decode the
inbound encoded data 52. Once encoded, the baseband processing
module 42 provides the outbound encoded data 54 to the transmit
section 44. The transmit section 44 receives the outbound encoded
data 54 and converts the outbound encoded data 54 into an outbound
transmit signal 56.
[0045] The outbound transmit signal 56 is a carrier signal with
amplitude modulation, such as ASK, or phase modulation, such as
PSK, or load modulation of the carrier signal can be used. The
frequency of the carrier signal in near field mode in one
embodiment is a low frequency (LF) or a high frequency (HF) range.
In accordance with ISO series standards, such near field ranges are
a low frequency at approximately 135 KHz or less and a high
frequency at approximately at 13.56 MHz. In far field mode, in an
embodiment, the frequency of the carrier signal is in the ultra
high frequency range or microwave range. In accordance with ISO
series standards, such far field ranges are at approximately 2.45
GHz frequency, approximately 860 MHZ to 930 MHz ultra high
frequency (UHF) range or approximately 433.92 MHz UHF.
[0046] In near field mode, the configurable coupling circuit 46 is
operable to couple the transmit section 44 to an inductor in the
configurable coupling circuit 46 to transmit the outbound transmit
signal 56 using electromagnetic or inductive coupling to an RFID
reader 16-18. In far field mode, the configurable coupling circuit
46 is operable to couple the transmit section 44 to the antenna
section 48, and the multi-mode RFID tag 38 then utilizes a
back-scattering RF technology to transmit the outbound transmit
signal 56 to RFID readers 16-18.
[0047] FIG. 3 is a block diagram of one embodiment of the
configurable coupling circuit 46. The configurable coupling circuit
46 includes a capacitor C160, an inductor L1 62, and a second
capacitor C2 66. In one embodiment, the configurable coupling
circuit includes a switch 64. The switch 64 in this embodiment
connects the antenna section 48 and capacitor 66 to the inductor L1
and capacitor C1 in a first position. In a second position, the
switch 64 connects the antenna section 48 and capacitor 66 to
ground or otherwise isolates the antenna from the inductor L1 and
capacitor C1. The switch 64 may be an actuator, a transistor
circuit, or other equivalent device. For an active tag, a battery
41 may power the switch 64. For passive tags, an RFID reader 16-18
transmits a continuous wave, unmodulated signal to power the
multi-mode RFID tag 38. The multi-mode RFID tag 38 may then use
voltage generated from the power generating and signal detection
module 40 to power the switch 64 to change positions. In an
alternate embodiment, the multi-mode RFID tag 38 may be configured
prior to provisioning to operate in only near field mode or far
field mode. For example, the multi-mode RFID tag 38 may be
hardwired at manufacturing to only couple to the antenna section 48
for operation in far field mode or to only couple to the coil
antenna 62 to operate in near field mode. In another example, the
RFID tag 38 may be pre-programmed to operate only in near field
mode or far field mode prior to provisioning.
[0048] In far field mode, the antenna 48 and capacitor C2 are
coupled to inductor L1 and capacitor C1. Inductor L1 and capacitor
C1 are operable as an impedance matching circuit for the antenna
48. The inductor L1 provides an inductance value for impedance
matching for the antenna 48 and the capacitor C1 provides a
capacitance value to the impedance matching for the antenna 48. In
an embodiment, the capacitor C1 is adjustable or variable, such as
a digital switched capacitor, and is operable to be tuned to
provide a desired capacitance value for the impedance matching in
far field mode. Thus, in far field mode, the antenna 48 and the
configurable coupling circuit 46 receive the inbound receive signal
50 and are operable to provide the inbound receive signal 50 to the
power generating and signal detection module 40.
[0049] In near field mode, the switch 64 is open such that the
capacitor C2 is floating or connected to ground. In another
embodiment, the multi-mode RFID tag 38 does not include a switch 64
but is hardwired at manufacturing to isolate the antenna 48 and/or
capacitor C2 from the inductor L1. In an alternate embodiment,
other devices other than a switch 64 may be used to isolate the
antenna 48 and/or capacitor C2 and the inductor L1 while the
multi-mode RFID tag 38 is in near field mode.
[0050] The inductor L1 acts as a coil antenna to provide
electromagnetic or inductive coupling with the coil or coils of
RFID reader 14-18. The inductor L1 and the capacitor C1 form a
resonant circuit tuned to the transmission frequency of the RFID
reader 14-18. In response to the magnetic field generated by the
RFID reader 14-18 coil antenna, the voltage at the inductor L1
reaches a maximum due to resonance step-up in the parallel resonant
circuit. In an embodiment, the capacitor C1 is adjustable or
variable and is operable to be tuned to provide optimization of the
parallel resonant circuit. For example, the capacitor C1 may be
adjusted to provide optimization of at least one of bandwidth,
quality factor, gain and roll-off of the configurable coupling
circuit 46 in the near field mode. Generally, to operate in the
near field mode, the distance between the inductor L1 of the RFID
tag 38 and the coil antenna of the RFID reader 14-18 must not
exceed approximately .lamda./2.pi., so that the inductor L1 is
located within the magnetic field created by the coil antenna of
the RFID reader 14-18. In near field mode, the configurable
coupling circuit 46 is operable to provide the inbound receive
signal 50 to the power generating and signal detection module
40.
[0051] During transmission, the inductor L1 acts as a coiled
antenna that creates the magnetic field from current flowing
through the inductor L1 using the energy provided to the transmit
section 44 by the power generating and signal detection module 40.
Again, in order to receive the outbound transmit signal 56 in the
near field mode, the distance between the inductor L1 of the RFID
tag 38 and the coil antenna of the RFID reader 14-18 should be
equal to or less than approximately .lamda./2.pi., so that the coil
antenna of the RFID reader 14-18 is located within the magnetic
field created by the inductor L1.
[0052] In one embodiment, as explained above with respect to FIG.
2, the baseband processing module 42 is operable to process
commands from an RFID reader 14-18. For example, one command from
the RFID reader 14-18 may be a mode command to operate the
multi-mode RFID tag 38 in near field mode or in far field mode.
Upon processing such mode command, the baseband processing module
42 is operable to configure the multi-mode RFID tag 38 to operate
in near field more or far field mode. In another embodiment, the
multi-mode RFID tag may have a preset input that may be set by a
user to determine the mode of operation. Thus, upon installation of
the multi-mode RFID tag in a particular application, the RFID tag
may be preset to the mode best suited for such application.
[0053] FIG. 4 illustrates another embodiment of a multi-mode RFID
tag 68 in accordance with the present invention. Similarly, to
FIGS. 2 and 3, the multi-mode RFID tag 68 in this embodiment
includes a power generating and signal detection module 40, a
baseband processing module 42, a transmit section 44, a
configurable coupling circuit 46, and an antenna section 48. In
addition, a switch 70 and load resistance Zm are connected between
the transmit section and configurable coupling circuit. In
operation, the switching on and off of the load resistance Zm at
the inductor L1, e.g. the coil antenna in the near field mode,
effects voltage changes at the RFID reader's coil antenna and thus
has the effect of an amplitude modulation of the RFID reader's
antenna voltage by the multi-mode RFID tag 38. By switching on and
off of the load resistance Zm in response to the outbound encoded
data 54, the transmit section 44 is operable to transfer the data
from the RFID tag to the RFID reader with load modulation.
Similarly, the switch 70 and load resistance Zm can modulate the RF
backscatter signal from the transmit section 44 to modulate the
reflected RF outbound transmit signal 56 in far field mode. Thus,
the switch 70 and load resistance Zm provide an efficient
modulation of the outbound transmit signal 56 for the multi-mode
RFID tag 38.
[0054] The embodiment 4 illustrates a passive RFID multi-mode tag
38. In another embodiment shown in FIG. 2, the multi-mode tag 38
may also be designed as an active tag by including a battery 41 to
provide the power to operate the RFID tag 38. With active tag
design, the power generating circuit may not be necessary and an
RFID reader 14-18 does not need to transmit a CW, unmodulated
signal to power the RFID tag 38 before communicating with the RFID
tag 38. In addition, the battery 41 would allow the RFID tag 38 to
switch between near field mode and far field mode in order to
detect signals from an RFID reader 14-18 without waiting for a
power signal and command from an RFID reader 14-18. The
disadvantage of active tags with a battery is the shorter duration
of life of the tag. The tag would become inoperable when the
battery loses its charge. However, an active multi-mode RFID tag 38
may be optimal for higher processing applications or applications
that only need certain duration, e.g. tags for perishable
items.
[0055] FIG. 5 illustrates a schematic block diagram of the inductor
L1 62 in one embodiment of the multimode RFID tag 38 in accordance
with the present invention. In this embodiment, the inductor L1 in
the configurable coupling circuit 46 operates in the ultra high
frequency (e.g., UHF) range in near field mode. Due to higher
frequencies, the coils of the inductor L1 can be much smaller sized
coils and can be integrated on chip with other modules of the
multi-mode RFID tag 38. As shown in FIG. 5, the inductor L1 62 has
a radius r.sub.2; the coil antenna 80 of the RFID reader 14-18 has
a radius r.sub.1; and the distance between the inductor L1 and the
coil antenna 80 equals distance d. In this embodiment, with
reference to FIG. 5, the magnetic field M.sub.12 between the coil
antenna 80 of the RFID reader 14-18 and the inductor L1 of the RFID
tag 38 is:
M 12 = .mu. 0 .pi. N 1 N 2 r 1 2 r 2 2 2 ( d 2 + r 1 2 ) 3
##EQU00001##
wherein .mu..sub.0 is the permeability of space. The inductance
L.sub.tag and Q factor of the tag Q.sub.tag can be determined
from:
L TAG .apprxeq. .mu. 0 N 2 r av ln ( 2 r av / a ) ##EQU00002## Q
TAG = .omega. 0 L r series .varies. .omega. 0 ##EQU00002.2##
For example, for one embodiment of a multi-mode RFID tag 38
operating in near field mode in UHF range at approximately 900 MHz,
the L.sub.tag equals approximately 56.6 nH and Q.sub.tag equals
approximately 4.9.
[0056] FIG. 6 illustrates the range between the RFID tag 38 and the
RFID reader 14-18 in the UHF near field mode assuming the
embodiment of FIG. 5. As seen in FIG. 6, the range is limited by
the transmit power of the tag. For example:
Z 12 ( .omega. 0 ) = V 2 I 1 = .omega. 0 M 12 Q 2 ##EQU00003##
.DELTA. Z 11 ( .omega. 0 ) .varies. .omega. 0 2 M 12 2 Q 2
##EQU00003.2##
and assuming the maximum transmit current of the tag is 500 mA,
then the range is approximately 5 mm with a -55 dBV minimum receive
signal, the tag's minimum voltage is 0.25 volts, and a 60 dB
blocker to signal ratio. Note that the tag's input
voltage=I.sub.1*Z.sub.12; the reader's minimum RX
signal=0.5*(I.sub.1*.DELTA.Z.sub.11)2; and the blocker to signal
ratio=Z.sub.11/.DELTA.Z.sub.11. A Manchester coding with data rate
of 50 kbps is utilized in this embodiment.
[0057] Though the range of communication is smaller (e.g., <5
mm) in UHF near field mode than at lower frequencies (such as HF
and LF), such short range, UHF near field RFID communications are
well suited for near read applications, such as inventory items,
monitory paper authentication, passports, credit cards, etc. The
near field UHF operation of the RFID tag 38 also has more efficient
operation near fluids, such as fluid medication bottles. In
addition, the inductor L1 or coil antenna 62 may be designed
sufficiently small to be integrated on chip. By integrating the
RFID tag 38 onto a single integrated circuit, the cost of the RFID
tag 38 can be significantly reduced.
[0058] The multi-mode RFID tag 38 thus provides near field and far
field mode operation. In one embodiment the multi-mode RFID tag
operates in UHF range in the near field mode with an integrated on
chip inductor or coil antenna. By operating in both near field and
far field mode, the RFID tag provides multi-standard,
multi-technology option for use in multiple applications. As such,
the RFID tags are not limited to only near read or far read
applications but can be used in both type applications and are
operable to be switched from near field mode to far field mode or
from far field mode to near field mode to accommodate different
types of RFID readers and differing distances between the
multi-mode RFID tag and an RFID reader.
[0059] As may be used herein, the terms "substantially" and
"approximately" provides an industry-accepted tolerance for its
corresponding term and/or relativity between items. Such an
industry-accepted tolerance ranges from less than one percent to
fifty percent and corresponds to, but is not limited to, component
values, integrated circuit process variations, temperature
variations, rise and fall times, and/or thermal noise. Such
relativity between items ranges from a difference of a few percent
to magnitude differences. As may also be used herein, the term(s)
"coupled to" and/or "coupling" and/or includes direct coupling
between items and/or indirect coupling between items via an
intervening item (e.g., an item includes, but is not limited to, a
component, an element, a circuit, and/or a module) where, for
indirect coupling, the intervening item does not modify the
information of a signal but may adjust its current level, voltage
level, and/or power level. As may further be used herein, inferred
coupling (i.e., where one element is coupled to another element by
inference) includes direct and indirect coupling between two items
in the same manner as "coupled to". As may even further be used
herein, the term "operable to" indicates that an item includes one
or more of power connections, input(s), output(s), etc., to perform
one or more its corresponding functions and may further include
inferred coupling to one or more other items. As may still further
be used herein, the term "associated with", includes direct and/or
indirect coupling of separate items and/or one item being embedded
within another item. As may be used herein, the term "compares
favorably", indicates that a comparison between two or more items,
signals, etc., provides a desired relationship. For example, when
the desired relationship is that signal 1 has a greater magnitude
than signal 2, a favorable comparison may be achieved when the
magnitude of signal 1 is greater than that of signal 2 or when the
magnitude of signal 2 is less than that of signal 1.
[0060] The present invention has also been described above with the
aid of method steps illustrating the performance of specified
functions and relationships thereof. The boundaries and sequence of
these functional building blocks and method steps have been
arbitrarily defined herein for convenience of description.
Alternate boundaries and sequences can be defined so long as the
specified functions and relationships are appropriately performed.
Any such alternate boundaries or sequences are thus within the
scope and spirit of the claimed invention.
[0061] The present invention has been described above with the aid
of functional building blocks illustrating the performance of
certain significant functions. The boundaries of these functional
building blocks have been arbitrarily defined for convenience of
description. Alternate boundaries could be defined as long as the
certain significant functions are appropriately performed.
Similarly, flow diagram blocks may also have been arbitrarily
defined herein to illustrate certain significant functionality. To
the extent used, the flow diagram block boundaries and sequence
could have been defined otherwise and still perform the certain
significant functionality. Such alternate definitions of both
functional building blocks and flow diagram blocks and sequences
are thus within the scope and spirit of the claimed invention. One
of average skill in the art will also recognize that the functional
building blocks, and other illustrative blocks, modules and
components herein, can be implemented as illustrated or by discrete
components, application specific integrated circuits, processors
executing appropriate software and the like or any combination
thereof.
* * * * *