U.S. patent application number 13/719745 was filed with the patent office on 2013-05-16 for rfid uhf stripline antenna-coupler.
This patent application is currently assigned to ZIH Corp.. The applicant listed for this patent is ZIH Corp.. Invention is credited to Martin Andreas Karl Schwan, Karl Torchalski, Boris Y. Tsirline.
Application Number | 20130120797 13/719745 |
Document ID | / |
Family ID | 38234297 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130120797 |
Kind Code |
A1 |
Tsirline; Boris Y. ; et
al. |
May 16, 2013 |
RFID UHF STRIPLINE ANTENNA-COUPLER
Abstract
A system having a multi-coupler array is provided. Each coupler
is configured to communicate with a targeted transponder from among
a group of multiple adjacent transponders. The couplers may each
include one or more conductive strips, at least one terminating
load, a dielectric material, a first ground plane, and a second
ground plane. Each of the conductive strips can extend between the
first and second ground planes and the dielectric material from an
input end connected to a transceiver to a loaded end connected to
the terminating load. The conductive strips may be configured to
propagate electromagnetic fields concentrated in a near field
region of the conductive strips in a direction generally
perpendicular to the conductive strips to couple with a targeted
transponder. The coupler may include an enclosure for directing the
electromagnetic fields. The conductive strip may have a tapered or
non-linear profile such as a modified bow-tie profile.
Inventors: |
Tsirline; Boris Y.;
(Glenview, IL) ; Torchalski; Karl; (Arlington
Heights, IL) ; Schwan; Martin Andreas Karl; (Chicago,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZIH Corp.; |
Lincolnshire |
IL |
US |
|
|
Assignee: |
ZIH Corp.
Lincolnshire
IL
|
Family ID: |
38234297 |
Appl. No.: |
13/719745 |
Filed: |
December 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11829455 |
Jul 27, 2007 |
8358246 |
|
|
13719745 |
|
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|
|
11371785 |
Mar 9, 2006 |
7586410 |
|
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11829455 |
|
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Current U.S.
Class: |
358/1.15 ;
340/10.1 |
Current CPC
Class: |
H01P 3/085 20130101;
G06F 3/1296 20130101; G06K 7/10316 20130101; G06K 7/01 20130101;
G06K 7/10346 20130101 |
Class at
Publication: |
358/1.15 ;
340/10.1 |
International
Class: |
G06F 3/12 20060101
G06F003/12; G06K 7/01 20060101 G06K007/01 |
Claims
1. A coupler array for an RFID enabled system having a media
conveyance system configured to transport media units that each
include at least one transponder along a feed path in a feed
direction, the coupler array comprising: a plurality of couplers
for transmitting signals to one or more transponders in the feed
path, wherein the plurality of couplers includes a first coupler
located at a first position relative to the feed path and a second
coupler located at a second position relative to the feed path, the
first position is at a different location than the second
position.
2. The coupler array of claim 1 further comprising at least a third
coupler at a third position relative to the feed path, the third
position is at a different location than the first position and the
second position.
3. The coupler array of claim 1, wherein the first coupler has a
first orientation and the second coupler has a second
orientation.
4. The coupler array of claim 4, wherein at least one of the first
orientation and the second orientation is parallel to the feed
direction of the feed path.
5. The coupler array of claim 4, wherein the first orientation is
rotated at a 45.degree. angel relative to the second
orientation.
6. The coupler array of claim 4, wherein the first orientation is
rotated at a 90.degree. angel relative to the second
orientation.
7. The coupler array of claim 4, wherein each of the first
orientation and the second orientation is at an angle between
0.degree. and 90.degree. relative to the feed direction of the feed
path.
8. The coupler array of claim 1, wherein the plurality of couplers
includes at least one stripline coupler.
9. The coupler array of claim 1, wherein the plurality of couplers
includes at least one microstrip coupler
10. The coupler array of claim 1, wherein each of the plurality of
couplers is selectively activated to communicate with a targeted
transponder.
11. The coupler array of claim 1, wherein the first coupler is
configured to communicate with a first transponder in a first media
unit of the media units and the second coupler is configured to
communicate with a second transponder in a second media unit of the
media units, the first transponder and second transponder having
different orientations relative to the feed direction of the feed
path.
12. The coupler array of claim 1, wherein at least one coupler is
selectively activated based on an orientation of a targeted
transponder.
13. The coupler array of claim 1, wherein at least one coupler of
the plurality of couplers is activated to communicate with a
targeted transponder having a similar orientation to the feed path
as the coupler.
14. A printer comprising: a media conveyance system configured to
transport media units that each include at least one transponder
along a feed path in a feed direction; and a coupler array
comprising: a plurality of couplers for transmitting signals to the
transponders in the feed path, wherein the plurality of couplers
includes a first coupler located at a first position relative to
the feed path and a second coupler located at a second position
relative to the feed path, the first position is different than the
second position.
15. The printer of claim 14 further comprising a third coupler at a
third position relative to the feed path that is different than the
first position and the second position.
16. The printer of claim 14, wherein the first coupler has a first
orientation and the second coupler has a second orientation, and at
least one of the first orientation and the second orientation is
parallel to the feed direction of the feed path.
17. The printer of claim 14, wherein each of the plurality of
couplers is selectively activated to communicate with a targeted
transponder.
18. The printer of claim 14, wherein the first coupler is
configured to communicate with a first transponder in a first media
unit of the media units and the second coupler is configured to
communicate with a second transponder in a second media unit of the
media units, the first transponder and second transponder having
different orientations relative to the feed direction of the feed
path.
19. The printer of claim 14, wherein at least one coupler is
selectively activated based on an orientation of a targeted
transponder.
20. The printer of claim 14 further comprising a printhead
configured to print indicia onto the media units.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application of
U.S. patent application Ser. No. 11/829,455, filed on 27 Jul. 2007,
which is a continuation-in-part application of U.S. patent
application Ser. No. 11/371,785, filed on 9 Mar. 2006 (now U.S.
Pat. No. 7,586,410, issued 8 Sep. 2009), both of which are
incorporated herein by reference in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention.
[0003] The present invention relates to RFID antenna-couplers and,
in particularly, to spatially selective antenna-couplers capable of
selectively communicating with a targeted transponder from among a
group of adjacent transponders.
[0004] 2. Description of Related Art.
[0005] Radio frequency identification (RFID) transponders, either
active or passive, are typically used with an RFID transceiver or
similar device for communicating information back and forth. In
order to communicate, the transceiver exposes the transponder to a
radio frequency (RF) electromagnetic field or signal. In the case
of a passive transponder, the RF electromagnetic field energizes
the transponder and thereby prompts the transponder to respond to
the transceiver by re-radiating the received signal back and
modulating the field in a well-known technique called
backscattering. In the case of an active transponder, the
transponder may respond to the electromagnetic field by
transmitting an independently powered reply signal to the
transceiver.
[0006] Problems can occur when interrogating multiple adjacent
transponders regardless on whether the transponders are passively
or actively powered. For example, an interrogating electromagnetic
signal may activate more than one transponder at a given time. This
simultaneous activation of multiple transponders may lead to
collision or communication, i.e. read and write, errors because
each of the multiple transponders may transmit reply signals to the
transceiver at the same time.
[0007] Several collision management techniques commercially exist
for allowing near simultaneous communication between multiple
transponders and a single transceiver while reducing communication
errors. However, such collision management techniques tend to
increase system complexity, cost, and delay response. Furthermore,
such techniques are often "blind" in that they cannot locate a
given transponder or more specifically recognize the position of a
transponder within the interrogating RF electromagnetic field. For
example, in a printer-encoder device, the device would not know
whether the transceiver was communicating with a transponder
proximate to the printhead or not.
[0008] Another method of preventing multiple transponder activation
is to electrically isolate transponders from one another. For
example, devices or systems may employ an RF-shielded housing or
anechoic chamber for shielding the adjacent and non-targeted
transponders from the electromagnetic field. In various
applications, transponders individually pass though a shielded
housing for individualized exposure to an interrogating RF
electromagnetic field. Unfortunately, RE-shielded housings add cost
and complexity to a system and limit the type (i.e., size) of
transponders that can be processed by the system. Furthermore, many
systems are limited with regard to space or weight and, thus,
cannot accommodate such shielded housings.
[0009] The challenge of avoiding multiple transponder activation
may be especially acute in some applications. RFID printer-encoders
are one example. RFID printer-encoders are devices capable of
encoding and printing on a series or stream of labels with embedded
transponders. The close proximity of the transponders to each
other, during processing, makes targeting a particular transponder
for encoding purposes problematic. Moreover, the space, cost, and
weight restrictions associated with such devices, among other
factors, make collision management techniques or shielding
components for alleviating multiple transponder activation less
than desirable.
[0010] In light of the foregoing it would be desirable to provide a
RFID system or device capable of interrogating individual
transponders positioned among multiple adjacent transponders
without the need for collision management techniques or shielding
components.
BRIEF SUMMARY
[0011] The present invention may address some of the above needs by
providing a stripline antenna-coupler for a RFID system configured
to selectively communicate with a targeted transponder from among a
group of multiple adjacent transponders. The antenna-coupler is
adapted to have a controlled transmission range that can be limited
to minimize the inadvertent activation of transponders outside a
transponder encoding region. As such, the antenna-coupler operates
with little to no anti-collision management techniques or shielding
components. The antenna-coupler of the present invention is
relatively compact with a length usually one-half wavelength or
less minimizing the footprint of the antenna-coupler within the
space-restricted RFID system. Also, the antenna-coupler may have an
enclosure configured to encourage a particular direction or profile
of the transmission signals of the antenna-coupler. For example,
the antenna-coupler may be configured for side coupling, i.e. the
antenna-coupler may be perpendicular to the targeted transponder,
which may be beneficial in a variety of space-restricted
systems.
[0012] According to one embodiment of the present invention, the
RFID system may include a transponder conveyance and an
antenna-coupler. The transponder conveyance is adapted to transport
the targeted transponder through the transponder encoding region
along a predetermined path. The antenna-coupler may be a near field
antenna-coupler and be configured to couple with the targeted
transponder in the transponder encoding region. And the
antenna-coupler may be perpendicular to the targeted transponder
during coupling. The system may further include a transceiver that
is in electrical communication with the antenna-coupler. The
transceiver is configured to generate communication signals.
[0013] The antenna-coupler may include a first ground plane and a
second ground plane spaced apart from each other and connected by
one or more connections and at least two conductive strips
positioned between the ground planes. The conductive strips are
configured to propagate a plurality of electromagnetic fields,
while the ground planes and connections between them are configured
to promote the propagation of the electromagnetic fields from a
side of the conductive strips. More specifically, the
electromagnetic fields from the side of the conductive strips may
be in a direction generally perpendicular to the length of the
conductive strips and generally parallel to the grounds planes for
coupling with the targeted transponder in the transponder encoding
region. For example, the near field antenna-coupler may include a
number of connections that extend substantially around the
conductive strips and define one active side of the antenna-coupler
free of connections and is configured to promote the propagation of
the electromagnetic fields from the active side for coupling with
the targeted transponder.
[0014] The antenna-coupler may also have a dielectric material
positioned between the first ground plane and the second ground
plane. For example, the dielectric material may be FR4 or air.
[0015] The antenna-coupler may also include an input port for
connecting the antenna-coupler to the transceiver and at least one
terminating load. Each of the conductive strips may extend from a
first end that is connected to the input port and a second end that
is connected to the at least one terminating load. Each second end
of each conductive strip may be terminated by an individual
terminating load (i.e., one load per strip) such that the load
impedance ("Z.sub.L") equals the input impedance ("Z.sub.IN")
multiplied by the number of conductive strips of the
antenna-coupler ("N"). Alternatively, the second ends of the
conductive strips may be terminated by a common terminating load
(i.e., the conductive strips are terminated by the same load) such
that Z.sub.L equals Z.sub.IN.
[0016] The antenna-coupler of the present invention may further be
configured to operate within a band of frequencies. Each conductive
strip defines a width and a length. According to one embodiment of
the present invention, the width of a conductive strip remains
substantially constant and the length of the conductive strip is
substantially equal to one half wavelength of the centered
frequency within the band of frequencies. According to another
embodiment, the width of the conductive strip varies forming a
tapered profile and the length of the conductive strip is equal to
or less than one half wavelength of the centered frequency. For
example, the tapered profile of a conductive strip may be a
modified bow-tie profile, an exponential profile, a triangular
profile, a Klopfenstein profile, and a Hecken profile.
[0017] The dielectric material may form a number of dielectric
substrates depending on the number of conductive strips. A
conductive strip may be directly deposited onto one of the surfaces
of the dielectric substrates. Or the dielectric material may form
one overall substrate layer having cut-outs for receiving the
conductive strips.
[0018] According to one embodiment of the present invention, the
input port is adjacent to one of the ground planes and is connected
to the first end of each of the conductive strips by a connection
extending through the ground plane, the dielectric material, and to
the conductive strips.
[0019] The antenna-coupler may have a first and a second
terminating load. The first terminating load may be adjacent to the
first ground plane and may be connected to the second end of the
first conductive strip by a connection extending through the first
ground plane, the dielectric material, and to the first conductive
strip. The second terminating load may be adjacent to the second
ground plane and is connected to the second end of the second
conductive strip by a connection extending through the second
ground plane, the dielectric material, and to the second conductive
strip. Alternatively, each of the terminating loads may be on the
same ground plane. Each connection may be a via, such as a hidden
or buried via.
[0020] Each of the conductive strip defines a characteristic
impedance which may be less than the load impedance. For example,
the load impedance may be substantially equal to 50 ohms and the
characteristic impedance may be less than 50 ohms.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0021] Having thus described the invention in general terms,
reference will now be made to the accompanying drawings, which are
not necessarily drawn to scale, and wherein:
[0022] FIG. 1 is a side schematic view of a printer-encoder
according to an embodiment of the present invention;
[0023] FIG. 2A is a simplified cut-away top view of a web of media
units passing over an antenna-coupler according to an embodiment of
the present invention;
[0024] FIG. 2B a cross-section view of the web and antenna-coupler
of FIG. 2A;
[0025] FIG. 3 is a perspective view of an electro-magnetic field
distribution of the antenna-coupler of-FIG. 2B;
[0026] FIG. 4 is a simplified cut-away bottom view of a web of
media units passing over an antenna-coupler array according to
another embodiment of the present invention;
[0027] FIG. 5 is a simplified cut-away bottom view of a web of
media units passing over an antenna-coupler array according to yet
another embodiment of the present invention;
[0028] FIG. 6A is a cross-sectional side view of an antenna-coupler
according to another embodiment of the present invention; and
[0029] FIG. 6B is a perspective exploded view of the
antenna-coupler of FIG. 6A.
DETAILED DESCRIPTION OF THE INVENTION
[0030] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
some, but not all embodiments of the invention is shown. Indeed,
this invention may be embodied in many different forms and should
not be construed as limited to the embodiments set forth herein;
rather, these embodiments are provided so that this disclosure will
satisfy applicable legal requirements. Like numbers refer to like
elements throughout.
[0031] The present invention concerns an apparatus for enabling an
RFID transceiver (sometimes referred to as a "reader") to
selectively communicate with a targeted transponder that is
commingled among or positioned in proximity to multiple adjacent
transponders. As will be apparent to one of ordinary skill in the
art, various embodiments of the present invention are described
below that selectively communicate with a targeted transponder
requiring little to no physical isolation of the transponder using
space-consuming shielded housings, anechoic chambers, or relatively
more complex or costly collision management techniques.
[0032] Several embodiments of the present invention may be useful
for reading, writing, or otherwise encoding passive or active
transponders located on assembly lines, in inventory management
centers where on-demand RFID labeling may be needed, or in other
similar circumstances, where the transponders are in close
proximity to each other. In various embodiments, one or more
transponders are mounted to or embedded within a label, ticket,
card, or other media form that may be carried on a liner or
carrier. In alternate linerless embodiments, a liner or carrier may
not be needed. Such RFID enabled labels, tickets, tags, and other
media forms are referred to collectively herein as "media units."
As will be apparent to one of ordinary skill in the art, it may be
desirable to print indicia such as text, numbers, barcodes,
graphics, etc., to such media units before, after, or during
communications with their corresponding transponders.
[0033] The present invention has been depicted, for illustration
purposes, in the context of a specific application, namely, RFID
enabled printer systems, also referred to herein as
"printer-encoders." Examples of printer-encoders are disclosed in
commonly-owned U.S. Pat. Nos. 6,481,907 and 6,848,616, which are
hereby incorporated herein by reference. However, the inventive
concepts described herein are not limited to printer-encoders and
may be applied to other RFID enabled systems that may benefit from
the ability to selectively communicate with a targeted transponder
disposed among multiple adjacent transponders close to the
antenna-coupler.
[0034] FIG. 1 illustrates an RFID printer-encoder 20 structured for
printing and programming a series or stream of media units 24
according to one embodiment of the present invention. In various
embodiments, as shown in FIGS. 2A and 2B, at least a few of the
media units 24 include transponders 26. As noted above, media units
may include labels, cards, etc, that are carried by a substrate
liner or web 22 as shown.
[0035] Referring back to FIG. 1, the printer-encoder 20 includes
several components, such as a printhead 28, a platen roller 29, a
feed path 30, a peeler bar 32, a media exit path 34, rollers 36, a
carrier exit path 38, a take-up spool 40, a ribbon supply roll 41,
a transceiver 42, a controller 45, and an antenna-coupler 50. The
web 22 is directed along the feed path 30 and between the printhead
28 and the platen roller 29 for printing indicia onto the media
units 24. The ribbon supply roll 41 provides a thermal ribbon (not
shown for clarity) that extends along a path such that a portion of
the ribbon is positioned between the printhead 28 and the media
units 24. The printhead 28 heats up and presses a portion of the
ribbon onto the media units 24 to print indicia. The take-up spool
40 is configured to receive and spool the used ribbon. This
printing technique is commonly referred to as a thermal transfer
printing. However, several other printing techniques may be used
including, but not limited to, direct thermal printing, inkjet
printing, dot matrix printing, and electro-photographic
printing.
[0036] After printing, as shown in FIG. 1, the media unit web 22
proceeds to the media exit path 34 where the media units are
typically individually removed from the web 22. For example, in one
embodiment, pre-cut media units 24 may be simply peeled from the
web 22 using the peeler bar 32 as shown. In other embodiments, a
group of multiple media units may be peeled together and
transmitted downstream to an in-line cutter for subsequent
separation (not shown). Various other known media unit removal
techniques may be used as will be apparent to one of ordinary skill
in the art.
[0037] In applications, such as the depicted embodiment, in which
the media units 24 are supported by a web 22, the web 22 may be
guided out of the printer-encoder 20 along the carrier exit path 38
by rollers 36 or other devices. Techniques and structures for
conveying or guiding the web of media units along the entire feed
path of the printer-encoder are well known in the art and, thus,
such techniques and conveyance systems are not described in great
detail.
[0038] The transceiver 42 is configured for generating and
transmitting RF communication signals that are broadcasted by the
spatially selective antenna-coupler 50 located proximate the media
feed path 30. For purposes of the present specification, the
transceiver 42 and the antenna-coupler 50 may be referred to
collectively as forming at least part of a communication system. As
will be explained in more detail below, the communication system
transmits an electromagnetic signal or pattern for establishing, at
predetermined transceiver power levels, a mutual coupling between
the transceiver and a targeted transponder of a media unit that is
located in the transponder encoding region, such that data may be
read from and written to transponder. The electromagnetic signal
has a far field component and a near field component. In general,
the far field component is too weak to activate or communicate with
any of the transponders, while the near field component is
concentrated mostly in the transponder encoding region such that it
only activates or communicates with the transponders in the
transponder encoding region.
[0039] In general, the transceiver is a device configured to
generate, process, and receive electrical communication signals.
One in the art would appreciate that similar devices such as
transmitters, receivers, or transmitter-receivers may be used
within this invention. "Transceiver" as used in the present
application and the appended claims refers to the devices noted
above and to any device capable of generating, processing, or
receiving electrical and/or electromagnetic signals.
[0040] FIG. 3 illustrates the stripline antenna-coupler 50 in
accordance with an embodiment of the present invention. The
antenna-coupler 50 is structured in electrical communication with
the transceiver (not shown in FIG. 3) for receiving and
broadcasting the signals originating from the transceiver to the
targeted transponder. In the depicted embodiment, the stripline
antenna-coupler 50 includes a first ground plane 52, a first
dielectric substrate 54, a conductive strip 56, a second dielectric
substrate 58, a second ground plane 60, an input port 62 and a
terminating load 64.
[0041] The ground planes 52, 60, the dielectric substrates 54, 58,
and the conductive strip 56 are stacked such that the conductive
strip 56 is between the dielectric substrates 54, 58 and the ground
planes 52, 60. More specifically, according to the illustrated
embodiment of FIG. 3, the first ground plane 52 has a first surface
and an opposite second surface. The first dielectric substrate 54
has a first surface and an opposite second surface. The first
surface of the first dielectric substrate 54 is adjacent to the
second surface of the first ground plane 52. The conductive strip
56 also has a first surface and an opposite second surface. The
first surface of the conductive strip 56 is adjacent to the second
surface of the first dielectric substrate 54. The second dielectric
substrate 58 has a first surface and an opposite second surface.
The first surface of the second dielectric substrate 58 faces the
second surface of the first dielectric substrate 54 and is adjacent
to the second surface of the conductive strip 56. The second ground
plane 60 has a first surface and an opposite second surface. The
first surface of the second ground plane 60 is adjacent to the
second surface of the second dielectric substrate 58.
[0042] Although the first and second dielectric substrates 54, 58
are primarily described as separate layers within the
antenna-coupler 50, the first and second dielectric substrates may
be one overall substrate or dielectric layer that is between the
two ground planes 52, 60 and includes a cut-out area configured to
receive the conductive strip 56. Also, the ground planes and
dielectric substrates are depicted as being generally rectangular
in shape. However, the general shape of the ground planes and the
dielectric substrates may vary between applications. For example,
the ground planes and the dielectric substrates may be a portion of
a relatively larger printed circuit board. The dielectric
substrates may be made or constructed from various dielectric
materials, including but not limited to, plastics, glasses,
ceramics, or combinations such as Rogers materials, Isola
materials, or woven glass reinforced epoxy laminate, commonly
referred to as "FR4" or flame resistant 4. Moreover, the dielectric
material may be air. Therefore the two ground planes may be spaced
apart from each other and have only air and the conductive strip
between them. One in the art would appreciate that these various
materials may be used to achieve a specific dielectric
constant.
[0043] FIGS. 6A and 6B illustrate the stripline antenna-coupler 150
in accordance with another embodiment of the present invention.
Rather than having one conductive strip, the stripline
antenna-coupler 150 may have multiple conductive strips. For
example, according to the embodiment of FIG. 6A, the stripline
antenna-coupler 150 has two conductive strips 156, 157. In this
depicted embodiment, the stripline antenna-coupler 150 includes a
first ground plane 152, a first dielectric substrate 154, a first
conductive strip 156, a second dielectric substrate 158, a second
ground plane 160, a second conductive strip 157, a third dielectric
substrate 159, an input port 162 and first and second terminating
loads 164, 165.
[0044] The ground planes 152, 160, the dielectric substrates 154,
158, 159 and the conductive strips 156, 157 are stacked such that
the conductive strips 156, 157 are between the dielectric
substrates 154, 158, 159 and the ground planes 152, 160. More
specifically according to the illustrated embodiment of FIGS. 6A
and 6B, the first ground plane 152 has a first surface and an
opposite second surface. The first dielectric substrate 154 has a
first surface and an opposite second surface. The first surface of
the first dielectric substrate 154 is adjacent to the second
surface of the first ground plane 152. The first conductive strip
156 also has a first surface and an opposite second surface. The
first surface of the first conductive strip 156 is adjacent to the
second surface of the first dielectric substrate 154. The second
dielectric substrate 158 has a first surface and an opposite second
surface. The first surface of the second dielectric substrate 158
faces the second surface of the first dielectric substrate 154 and
is adjacent to the second surface of the first conductive strip
156. The second conductive strip 157 has a first surface and an
opposite second surface. The first surface of the second conductive
strip 157 faces the second surface of the second dielectric
substrate 158 and is adjacent to the second surface of the second
dielectric substrate 158. The third dielectric substrate 159 has a
first surface and an opposite second surface. The first surface of
the third dielectric substrate 159 faces the second surface of the
second conductive strip 157 and is adjacent to the second surface
of the second conductive strip 158. The second ground plane 160 has
a first surface and an opposite second surface. The first surface
of the second ground plane 160 is adjacent to the second surface of
the third dielectric substrate 159.
[0045] Although the first, second, and third dielectric substrates
154, 158, 159 are primarily described as separate layers within the
antenna-coupler 150, the first, second, and third dielectric
substrates may be one overall substrate or dielectric layer that is
between the two ground planes 152, 160 and includes cut-out areas
configured to receive the conductive strips 156, 157. Also, the
ground planes and dielectric substrates are depicted as being
generally rectangular in shape. However, the general shape of the
ground planes and the dielectric substrates may vary between
applications. For example, the ground planes and the dielectric
substrates may be a portion of a relatively larger printed circuit
board. The dielectric substrates may be made or constructed from
various dielectric materials, including but not limited to,
plastics, glasses, ceramics, or combinations such as Rogers
materials, Isola materials, or woven glass reinforced epoxy
laminate, commonly referred to as "FR4" or flame resistant 4.
Moreover, the dielectric material may be air. Therefore the two
ground planes may be spaced apart from each other and have only air
and the conductive strip between them. One in the art would
appreciate that these various materials may be used to achieve a
specific dielectric constant.
[0046] As an example only, the stripline antenna-coupler 50 having
a single conductive strip as in FIG. 3 may have approximately the
following overall dimensions 3.5.times.18.times.100 mm and the
stripline antenna-coupler 150 having two conductive strips as in
FIG. 6A may have approximately the following overall dimensions
6.times.14.times.100 mm. The bow-tie shaped conductive strip may
have a width that varies linearly from 9 mm to 4.5 mm back to 9 mm.
For the double conductive strips, each conductive strip may have a
width that varies linearly from 10 mm to 3 mm back to 10 mm. The
linear length of the conductive strip (from end to end) may be
approximately 64 mm in an embodiment having a single conductive
strip. The linear length of the conductive strip (from end to end)
may be approximately 57 mm in an embodiment having two conductive
strips.
[0047] As explained in more detail below, the conductive strip 56
(or strips 156, 157) provides a conductive plane for the
propagation of electromagnetic waves from the antenna-coupler to a
targeted transponder. The conductive strip is fabricated from a
conductive material. For example only, the conductive material may
be copper, gold, silver, aluminum or combination thereof, or doped
silicon or germanium. The conductive strip 56 has a length
extending from a first end, referred to herein as the input end 66,
to a second end, referred to herein as the loaded end 68. The
conductive strip 56 defines a width from a first side edge 70 to a
second side edge 72. The conductive strip 56 also has a thickness
extending from the first surface of the conductive strip to the
second surface of the conductive strip.
[0048] The method of fabricating the antenna-coupler, including the
conductive strip may vary. For example and as noted above, the
dielectric substrate may include a cut out area in which the
conductive strip is inserted into. The conductive strip may also be
deposited directly onto either the second surface of the first
dielectric substrate or the first surface of the second dielectric
substrate. For example only, the conductive strip may be printed or
etched onto one of these surfaces.
[0049] The input end 66 of each conductive strip is connected to
the input port 62. For example only and as shown in FIG. 3, the
input port 62 may be adjacent to the first surface of the first
ground plane 52 and may be connected to the input end 66 of the
conductive strip by a vias or other connection 74 extending through
the first ground plane 52 and the first dielectric substrate 54 to
the conductive strip 56. For the embodiment of FIG. 6A, the input
port 162 may be connected to both the input ends of the first and
second conductive strips 156, 157 by a via or other connection 174
extending through the first ground plane 152 and extending through
the dielectric substrates 154, 158 to the conductive strips 156,
157.
[0050] Referring back to FIG. 3, the loaded end 68 of the
conductive strip is connected to the terminating load 64. The
terminating load 64 may be adjacent to the first surface of the
first ground plane 52 and may be connected to the loaded end 68 of
the conductive strip by a via or other connection 76 extending
through the first ground plane 52 and the first dielectric
substrate 54 to the conductive strip 56. As another example, in the
embodiment illustrated in FIG. 6A, each of the loaded ends 168, 169
of the first and second conductive strips 156, 157 may be connected
to a terminating load 164, 165 by one or more vias or other
connections 176, 177. Although depicted as two separate terminating
loads 164, 165, in other embodiments each loaded end 168, 169 may
be connected to the same terminating load.
[0051] The input port 62 connects the transceiver directly (or
indirectly through any form of transmission line) to the
antenna-coupler. For example, the input port may be a "RF port" as
known in the art. In particular, the transceiver is configured to
send an electrical source signal to the antenna-coupler through the
input port. The signal passes through the input port 62, the
conductive strip 56, and into the terminating load 64, which is
connected to at least one of the ground planes 52, 60.
[0052] In general as the electrical signal passes through a
conductive strip, the conductive strip operates as a transmission
line, rather than operating as a standing wave radiating antenna or
magnetic field generating coil. The passing signal in the
conductive strip generates electromagnetic fields concentrated in
the near field region of the conductive strip. The electromagnetic
fields may be adapted to couple the antenna-coupler to a
transponder disposed proximate the conductive strip, referred to
herein as the transponder encoding region. A more detailed
description of the electromagnetic fields concentrated in the near
field region, also known as "leaky" electromagnetic fields, is
provided in "Leaky Fields on Microstrip" L. O. McMillian et al.
Progress in Electromagnetics Research, PIER 17, 323-337, 1997 and
in commonly owned U.S. Patent Application Publication Nos.
2005/0045723 and 2005/0045724 to Tsirline et al., which are hereby
incorporated by reference. The effective range of antenna-couplers
relying on such leaky electromagnetic fields is limited because the
fields degrade, at an exponential rate, with increasing distance
from the antenna-coupler. This limited range reduces the likelihood
that a given transceiver's signal will activate transponders
outside the transponder encoding region.
[0053] As stated above the conductive strip is terminated at one
end by the terminating load. The terminating load is configured to
have an impedance value substantially equal to a source impedance
defined by the transceiver and its related circuitry. For example,
the terminating load and the source impedance may be 50 ohms. In
general, at the center operating frequency, the input impedance of
the antenna-coupler measured at the input end of a conductive strip
that has a linear length (i.e., measured from the input end to the
loaded end) of one half wavelength, or multiple thereof, is
substantially equal to the terminating load regardless of the
characteristic impedance of the conductive strip. A linear
conductive strip (i.e., a conductive strip have a constant width)
may be effectively shortened by tapering the conductive strip, such
that the width of the conductive strip varies over the length of
the conductive strip. In other words, a tapered conductive strip
having a length less than one half wavelength is similar to a
conductive strip having a length equal to one half wavelength in
that it has minimal impact on the input impedance. The
characteristic impedance of the conductive strip is defined by the
width of the conductive strip. Because it has no or minimal
influence on the input impedance of the antenna-coupler at the
center operating frequency, the conductive strip is dimensioned to
achieve proper coupling with a targeted transponder, while the
terminating load is configured to maintain an impedance match
between the antenna-coupler and the transceiver. For example, the
width of the conductive strip may be decreased or increased at
selective areas to produce a desired operating bandwidth of the
antenna-coupler. Decreasing the width of the conductive strip at
its center generally increases (i.e. widens) the bandwidth.
[0054] Although the relationship between the characteristic
impedance of the conductive strip and the terminating load
impedance may vary, according to one embodiment the characteristic
impedance is less than the terminating load impedance. Terminating
the conductive strip with a terminating load allows for impedance
matching. Further, terminating the conductive strip with a
terminating load that is substantially equal to the source
impedance and greater than the characteristic impedance of the
conductive strip forms what is known in the art as a "band-pass
filter." A band-pass filter is a device that is configured to
transmit signals in a particular frequency band or bandwidth. For
example, the antenna-coupler may have an operating frequency band
of 902 MHz-928 MHz and a center operating frequency of 915 MHz.
[0055] FIGS. 2B and 3 illustrate one example of a tapered
conductive strip 56 according to an embodiment of the present
invention. One side edge 72 of the conductive strip is angled
inwardly from the input end 66 to a midpoint in the conductive
strip 56 then the side edge 72 is angled outwardly from the
midpoint to the loaded end 68. The opposite side edge 70 of the
conductive strip remains substantially straight and parallel
relative to the length of the conductive strip 56 from the input
end 66 to the loaded end 68. The two side edges 70, 72 together
define a "modified bow-tie" profile. However the profile of the
conductive strip may vary. One in the art would appreciate the
various possible tapered profiles including, but not limited to,
exponential, triangular, Klopfenstein, and Hecken taper
profiles.
[0056] In embodiments having more than one conductive strip, a
wider operating bandwidth may be achieved by varying the lengths of
the individual conductive strips. More specifically, in an
embodiment have first and second conductive strips, a length of the
first conductive strip may be shorter and a length of the second
conductive strip may be longer than the resonating length (e.g.,
1/4, and 1/2 wavelengths) of the conductive strips. In an
embodiment having a first conductive strip, a second conductive
strip, and a third conductive strip, a length of the first
conductive strip me be shorter, a length of the second conductive
strip (between the first and third conductive strips) may be
substantially equal to, and a length of the third conductive strip
may be longer than the resonating length of the conductive strips.
By varying the lengths, the antenna-coupler has a wider operating
bandwidth compared to an embodiment in which the conductive strips
have the same length relative to one another.
[0057] One aspect of the present invention is the orientation of
the antenna-coupler and, more particularly, of the conductive strip
to the targeted transponder during coupling. As illustrated in FIG.
3, the dielectric substrates 54, 58 adjacent to the first and
second surfaces of the conductive strip 56 along with the ground
planes 52, 60 promote the propagation of the electromagnetic fields
E, H from the side edges 70, 72 of the conductive strip in a
direction generally perpendicular to the length of the conductive
strip 56 and generally parallel to the ground planes 52, 60
(referred to herein as side propagation) and thus facilitates the
coupling with a transponder that is positioned generally
perpendicular to the conductive strip 56 and thus the
antenna-coupler (referred to herein as side coupling). As used
herein, the transponder and antenna-coupler are considered to be
perpendicular when the width of the conductive strip is
perpendicular to a length of the transponder.
[0058] To further promote side propagation, the two ground planes
52, 60 may be connected along their perimeters, such that the two
ground planes 52, 60 are connected along three sides. The fourth
and unconnected side is referred to as the active side 78. The
ground planes 52, 60 in effect form an envelope or an enclosure for
receiving the conductive strip 56, where one side, i.e., the active
side 78, of the envelope is opened such that the electromagnetic
fields propagate out of the envelope and are directed or aimed at
the targeted transponder. For example and as shown in FIGS. 2B and
3, the two ground planes 52, 60 may be connected by a series of
vias 80 extending along the three sides. Also, as shown, in the
modified bow-tie profile embodiment, the substantially straight
side edge 70 of the conductive strip 56 is positioned such that it
is facing out and near the active side 78 defined by the ground
planes 52, 60. The connected sides of the ground planes 52, 60 will
further promote side propagation from the straight side edge 70 of
the conductive strip through the active side 78 defined by the
ground planes 52, 60. While the described embodiment uses a
plurality of vias 80 to connect the first and the second ground
planes 52, 60, a plurality of vias is only an example of the type
of connections that may be employed with the present invention.
Another example includes using additional ground planes or
combination of additional ground planes and vias to connect the
first and second ground planes along their edges to create the
envelope for receiving the conductive strip. Creating an envelope
as described herein (e.g., stitching three sides of the
antenna-coupler with vias or other connections) is also applicable
for multiple conductive strip embodiments, such as the embodiment
illustrated in FIG. 6A.
[0059] In yet another means of promoting side propagation may be
the shape of the conductive strip. For example, the modified
bow-tie profile of the illustrated embodiment, concentrates a
maximum magnetic field strength H at the straight side edge 70 near
the middle point where the width of the conductive strip 56 is the
narrowest, as well as fringe electric fields E along the side edge
70.
[0060] As illustrated in FIGS. 2A and 2B, the enclosed design of
the antenna-coupler 50 also provides a novel architecture for the
printer-encoder installation. Also described above, within a
printer encoder, a web 22 of media units 24 may be directed along a
feed path 30 by a media conveyance system. The feed path includes
passing near or through the transponder encoding region where the
antenna-coupler is configured to couple with the transponders of
the media units. The direction of the feed path near or through the
transponder encoding region defines a feed direction. Because the
antenna-coupler of the present invention is configured for side
coupling, the antenna-coupler 50 may be generally perpendicular to
the web 22 of media units 24. As used herein, an antenna-coupler is
generally perpendicular to the web of media units when the width of
the conductive strip, which also generally defines a width of the
antenna-coupler, is generally perpendicular to the feed
direction.
[0061] This configuration of the antenna-coupler in a generally
perpendicular orientation relative to the feed path may provide a
desired printer-encoder architecture, structure, or configuration.
Specifically, because the width of the antenna-coupler is
relatively vertical, the antenna-coupler occupies less horizontal
space in the printer-encoder providing more horizontal space or
allowing for a more horizontally compact package, which in turn
allows for smaller media unit sizes.
[0062] Although the present invention has been primarily described
as an antenna-coupler for an RFID enabled system, the present
invention may employ more than one antenna-coupler. For example and
as shown in FIG. 4, the present invention may include more than one
antenna-coupler 50. The antenna-couplers 50 together define an
antenna-coupler array. Individual antenna-couplers within the array
may be selectively activated in order to follow a targeted
transponder as it moves along a predetermined path within the
system or accommodate different size or type of tags.
[0063] The orientation of the antenna-couplers 50 to the feed path
30 or to each other may vary. As shown in FIG. 4, the
antenna-couplers 50 may be substantially parallel to each other and
generally perpendicular to the feed path 30. FIG. 5 illustrates
another embodiment of an antenna-coupler array having at least one
antenna-coupler 50a that is perpendicular to the feed path and at
least one other antenna-coupler 50b that is at a 45.degree. angle
to the feed path 30. Positioning the antenna-couplers at different
angles or orientations to the feed path enables the array to
communicate with a greater variety of media units. More
specifically, in many applications the transponders 26 are
generally parallel to the width of the media units 24, such that
the transponders 26 are generally perpendicular to the feed path
30, as shown in FIG. 4. However, in other applications the
transponders 26 may be angled across the media unit 24. For
example, and as shown in FIG. 5, the transponders 26 may be
positioned diagonally across the media unit 24, such that the
transponders 26 are generally at a 45.degree. angle to the feed
path 30. An array with antenna-couplers at different orientations
may adjust to the different orientations of the transponders on the
media units, by activating the antenna-couplers that share a
similar orientation to the feed path as the transponders.
Perpendicular and 45.degree. degree orientations are only two
examples of the various orientations that may be used within the
present invention. The array may include antenna-couplers with any
orientation (e.g., 0.degree. through 90.degree.). It should be
understood that the array may include more than two
antenna-couplers and more than two antenna-coupler orientations.
Also, it should be understood that the type of antenna-couplers
within the array may vary. For example, the array may include any
type of stripline antenna-coupler or microstrip
antenna-coupler.
[0064] Further, the present invention has been disclosed primarily
in terms of an antenna-coupler configured to broadcast primarily in
the near field. However, it must be understood that the enclosure
describe herein for directing antenna antenna-coupler signals is
not restricted to near field antenna-couplers. It is contemplated
that any type of antenna-coupler could be encased in the enclosure
to thereby direct the fields of the antenna-coupler to the open end
or ends of the enclosure.
[0065] FIG. 3 illustrates an embodiment of the enclosure where the
three sides of the dielectric substrates and the ground planes are
interconnected by vias, such that the fields of the antenna-coupler
are directed out of the fourth and active side. It must be
understood that this is only an exemplary configuration. Many
configurations of the enclosure may be employed to provide the
desired field emission profile. Any pattern could be created by
varying the portions of the sides or edges that are interconnected.
For example, portions of the fourth sides could also be enclosed to
further direct the field emissions. In particular, the end portions
of the fourth sides of the ground planes could be interconnected to
direct field emissions from a center portion of the fourth side of
the enclosure. Oppositely, the center portion of the fourth side
could be interconnected to direct the fields from the end portions
of the fourth sides. Other examples come to mind. For example, open
portions could be configured along any of the edges to give desired
field emissions.
[0066] FIGS. 3, 6A and 6B illustrate sandwich type arrangements
where the conductive strip or strips are sandwiched between two
ground planes such that the fields are emitted from the sides of
the antenna-coupler. The ground planes can be configured in any
orientation to allowed field emissions from any side of the
antenna-coupler. For example, ground planes could create a tray for
the antenna-coupler having a bottom formed by a first ground plane
and a side wall extending around the perimeter of the bottom and
formed by additional ground planes. A microstrip could be located
in the tray such that fields emitting from the microstrip are
encourage to propagate through a top surface of the antenna-coupler
defined by an open top of the tray.
[0067] Many modifications and other embodiments of the inventions
set forth herein will come to mind to one skilled in the art to
which these inventions pertain having the benefit of the teachings
presented in the foregoing descriptions and the associated
drawings. Therefore, it is to be understood that the inventions are
not to be limited to the specific embodiments disclosed and that
modifications and other embodiments are intended to be included
within the scope of the appended claims. Although specific terms
are employed herein, they are used in a generic and descriptive
sense only and not for purposes of limitation.
* * * * *