Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DUAL-POLARIZED, MULTIPLE STRIP-LOOP ANTENNA, AND
ASSOCIATED METHODOLOGY, FOR RADIO DEVICE
[0001] The present invention relates generally to an antenna for a portable
radio device, such as a Bluetooth-capable or IEEE 802.11-capable device that
operates at the IMS (Industry, Medical and Scientific) frequency band. More
particularly, the present invention relates to a dual-polarized antenna, and
an
associated methodology, of compact construction, capable of positioning at, or
within,
a radio housing of the portable radio device.
[0002] L-cornered antenna loops, formed of loop strips, are disposed upon a
substrate. The loop strips extend in either of a first polarization direction
or a second
polarization direction, the second polarization direction orthogonal to the
first
polarization direction. The loop strips are of dimensions and are connected
together
to be resonant at the IMS, or other selected, frequency band at orthogonal
polarization
directions.
Backjzround of the Invention
[0003] Radio communication systems are used by many in modern society to
communicate. Many varied communication services, both voice communication
services and data communication services, are regularly effectuated by way of
radio
communication systems. And, as technological advancements permit, the types of
communication services effectuable by way of radio communication systems shall
likely increase.
[0004] Cellular communication systems are exemplary of radio
communication systems that have high levels of usage. Cellular communication
systems are typically constructed to provide wide-area coverage. And, their
infrastructures have been installed over significant portions of the populated
areas of
the world. A user communicates by way of a radio communication system through
use of a wireless device, a radio transceiver, sometimes referred to as a
mobile station
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or user equipment (UE). Typically, access to a cellular communication system
is
provided pursuant to purchase of a subscription, either on a revolving, e.g.,
monthly
basis, or on a pre-paid, time-usage basis. Cellular communication systems,
operable
pursuant to different operating standards, defme radio air interfaces at
different
frequency bands, for instance, at the 800 MHz frequency band, at the 900 MHz
frequency band, and at bands located between 1.7 GHz and 2.2 GHz.
[0005] Other types of radio communication systems are also widely used, for
instance, Bluetooth (tm)-based and IEEE 802.11-based systems, implemented,
e.g.,
as, WLAN (Wireless Local Area Network) systems, also provide for voice and
data
communications, generally over smaller coverage areas than their cellular
counterparts. WLANs are regularly operated as private networks, providing
users
who have access to such networks the capability to communicate therethrough
through the use of Bluetooth-capable or 802.11-capable wireless devices. WLANs
are sometimes configured to be connected to public networks, such as the
Internet,
and, in turn, to other communication networks, such as PSTNs (Public Switched
Telephonic Networks) and PLMNs (Public Land Mobile Networks). Interworking
entities also are sometimes provided to provide more-direct connection between
the
small-area networks and a PLMN. Various of the aforementioned systems are
implemented at the 2.4 GHZ frequency band.
[0006] Radio communication systems are generally bandwidth-constrained.
That is to say, bandwidth allocations for their operation are limited. And,
such
limited allocation of bandwidth, imposes limits upon the communication
capacity of
the communication system. Significant efforts have been made, and attention
directed
towards manners by which, to efficiently utilize the limited bandwidth
allocated in
bandwidth-constrained systems. Dual-polarization communication techniques are
sometimes utilized. In a dual-polarization technique, data communicated at the
same
frequency is communicated in separate, polarized planes. Close to a doubling
of the
communication capacity is possible through the use of dual-polarization
techniques.
To transduce signal energy pursuant to a dual-polarization scheme, the
wireless
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device is required to utilize a dual-polarized antenna, operable in the
separate
polarization planes. Use of dual-polarization techniques also are advantageous
for the
reason that the effects of multi-path transmission and other interference are
generally
reduced, thereby improving quality of signal transmission and reception.
[0007] A dual-polarized antenna is realizable, for instance, by feeding a
square patch antenna at two orthogonal edges thereof by way of an edge feed or
a
probe feed. Generally, existing dual-polarized patch antennas are used in
conjunction
with two feeding-network circuits. Such existing antennas suffer from various
limitations. For instance, separation distances between the feed connections
are
required to be great enough to prevent occurrence of coupling between the
respective
feeding lines. Excessive amounts of coupling results in high cross
polarization levels.
[0008] As wireless devices are of increasingly small dimensions, packaged in
housings of increasingly-smaller dimensions, problems associated with the
cross-
polarization levels are likely to become more significant. An improved, dual-
polarized antenna, constructed in a manner to reduce such deleterious problems
is
needed.
[0009] It is in light of this background information related to antennas for
radio devices that the significant improvements of the present invention have
evolved.
Brief Description of the Drawings
[0010] Figure 1 illustrates a functional block diagram of a radio
communication system in which an embodiment of the present invention is
operable.
[0011] Figure 2 illustrates a plan view of a dual-polarized, multiple-strip
loop
antenna of an embodiment of the present invention.
[0012] Figure 3 illustrates a graphical representation showing simulated and
measured return losses plotted as a function of frequency of an antenna
forming part
of a wireless device of an exemplary embodiment of the present invention.
[0013] Figure 4 illustrates a representation of an exemplary, simulated
current
distribution of an antenna of an embodiment of the present invention.
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[0014] Figure 5 illustrates a graphical representation of simulated radiation
patterns of an antenna of an embodiment of the present invention at 2.47GHz.
[0015] Figure 6 illustrates a graphical representation, similar to that shown
in
Figure 5, but of measured radiation patterns exhibited by an antenna of an
embodiment of the present invention at 2.47 GHz.
[0016] Figure 7 illustrates a graphical representation showing simulated gain
as a function of an antenna of an embodiment of the present invention.
[0017] Figure 8 illustrates a method flow diagram representative of the
method of operation of an embodiment of the present invention.
Detailed Description
[0018] The present invention, accordingly, advantageously provides antenna
apparatus, and an associated method, for a portable radio device, such as a
Bluetooth-
compatible or 802.11-compatible device that operates at the IMS (Industry,
Medical
and Scientific) frequency band.
[0019] Through operation of an embodiment of the present invention, a dual-
polarized antenna of compact construction is provided. The antenna is capable
of
positioning at, or within, a radio housing of the portable radio device.
[0020] In one aspect of the present invention, the antenna is formed of loop
strips etched upon a substrate, configured in a manner to be resonant at a
selected
frequency band, such as a frequency band located at 2.47 GHz. The substrate is
of
dimensions permitting its positioning, together with the loop strips etched
thereon,
within the housing of a portable radio device, such as a wireless device
operable in a
Bluetooth-compatible or 802.11-compatible system. Signal energy polarized in
orthogonal, or other, directions. Transduced signal energy generated at the
wireless
device is transduced into electromagnetic form by the antenna and propagated
therefrom in the polarized directions. And, electromagnetic energy
communicated to
the wireless device in the polarized directions is transduced into electrical
form for
subsequent operations thereon by circuitry of the radio device.
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[0021 ] In another aspect of the present invention, a first group of the loop
strips etched onto the substrate is configured to form an L-cornered antenna
loop.
The L-cornered loop is formed by configuring adjacent loop strips such that
ends of
the adjacent loop strips intersect at substantially perpendicular angles. The
loop strips
5 of the first group, so-configured, are all, therefore positioned variously
to extend in a
first polarization direction or a second polarization direction, the second
polarization
direction orthogonal to the first polarization direction.
[0022] In another aspect of the present invention, a second group of loop
strips etched onto the substrate define a second L-cornered loop. Adjacent
ones of the
loop strips are configured to be connected at their ends at intersecting,
substantially-
perpendicular angles, thereby to be rectangular-cornered. And, each loop
strip, so-
configured, extends variously in a first polarization direction or a second
polarization
direction, orthogonal to a first polarization direction. Signal energy is
transduced by
the second loop, also in the two polarization directions.
[0023] In another aspect of the present invention, the first group and second
group of the loop strips include a shared set of loop strips, i.e., loop
strips that are
common to both the first group and the second group. The shared set of loop
strips
form part of the first antenna loop and part of the second antenna loop. At
least one
of the loop strips of the shared set extends in the first polarization
direction, and at
least one of the loop strips of the shared set extends in the second
polarization
direction. And, more specifically, the shared set includes at least two loop
strips that
extend in the first polarization direction and at least one loop strip that
extends in the
second polarization direction. The loop strips that extend in the first
polarization
direction are connected together by way of a loop strip that extends in the
second
polarization direction.
[0024] In another aspect of the present invention, a single feed connection is
provided for both of the polarization directions. The single feed connection
is
formed, or otherwise defmed, at a loop strip of the shared set. The feed
connection is
positioned to permit symmetrical excitation of the two antenna loops. Through
the
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use of the single feed connection, problems associated with cross polarization
are
reduced. A high-gain, high-efficiency, and compact, dual-polarized antenna is
thereby
provided.
[0025] In these and other aspects, therefore, antenna apparatus, and an
associated methodology is provided for a radio device. A substrate is
provided. And
a first group of loop strips is disposed upon the substrate. The loop strips
of the first
group are configured to form a first loop having at least one loop strip
extending in a
first polarization direction and at least one loop strip extending in a second
polarization direction. A second group of loop strips is disposed upon the
substrate.
The loop strips of the second group are configured to form a second loop
having at
least one strip that extends in the first polarization direction and at least
one strip
extending in the second polarization direction. The fust and second groups of
loop
strips each have loop strips that extend in the first and second polarization
directions,
respectively, and exhibit dual-polarization operation.
[0026] Turning first, therefore, to Figure 1, a radio communication system,
shown generally at 10, provides for communications with a mobile station 12.
The
mobile station, in the exemplary implementation, operates pursuant to a
Bluetooth
standard or IEEE 802.11 (b) or (g) standard, operable to send and to receive
signals at
the 2.4 GHz band. More generally, the mobile station 12 is representative of
any of
various wireless devices, and the radio communication system is representative
of any
various radio communication systems operable in conformity with any of various
communication standards or permitting of operation at unregulated frequency
bands.
Accordingly, while the following description shall describe exemplary
operation of a
Bluetooth or IEEE 802.11-compliant system, operable at the 2.4 GHz frequency
band,
it should be understood that the following description is merely exemplary and
that
the description of operation of the radio communication system operable in
conformity in another manner is analogous.
[0027] The radio communication system includes a network part, here
represented by a network station 14. The network station comprises, for
instance, an
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access point of a WLAN or an analogous entity that transceives signals with
wireless
devices, such as the mobile station 12. The network station, which here forms
an
access point, is part of a local network structure (WLAN) 16 that, in turn, is
coupled
to an external network, here a public packet data network (PDN) 18, such as
the
Internet.
[0028] The operating standard pursuant to which the mobile and network
stations are operable is permitting of, and here provides for, dual-polarized
communications at the operational frequency band of the communication system,
here
an ISM band that extends between 2.40 and 2.485 GHz.
[0029] The mobile station 12 includes transceiver circuitry, here represented
by a receive (RX) part 26 and a transmit (TX) part 28. The receive and
transmit parts
are coupled, such as by way of an antenna coupler or other entity that
provides
isolation between the transceiver parts to an antenna 32 of an embodiment of
the
present invention. The transceiver circuitry is capable of dual-polarization
operation.
That is to say, the transmit and receive parts are capable of generating
signals for
transmission in both of the polarization directions and also to operate upon
signals
communicated to the mobile station in both of the polarization directions.
[0030] Correspondingly, the antenna 32 forms a dual-polarized antenna,
capable of transducing signal energy of both of the polarization directions.
That is to
say, signal energy is detected by the antenna in both of the dual-polarization
directions. And, signal energy generated at the mobile station is transduced
into
electromagnetic form and radiated in both of the dual polarization directions.
In the
exemplary implementation, the antenna 32 is disposed upon a generally planar
substrate, of dimensions permitting its positioning within a housing of the
mobile
station.
[0031] Figure 2 illustrates in greater detail the antenna 32 of an embodiment
of the present invention and that forms part of the mobile station 12, shown
in Figure
1. The antenna is formed of a plurality of loop strips 42 disposed upon a
substrate 44.
The loops strips are etched, painted, or otherwise formed upon the substrate.
The
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loop strips are configured such that adjacent ones of the loop strips abut
against one
another in electrical connection therebetween. The loop strips are of lengths
and
widths and are connected together so as to be resonant at a desired frequency
band,
here the 2.4 GHz frequency band.
[0032] The loop strips are arranged into a rectangular loop structure
comprised of a first group 46 of loop strips and a second group 48 of loop
strips. The
adjacent loop strips intersect at their ends in substantially perpendicular
intersecting
angles. The groups 46 and 48 form antenna loops-in which, due to the
perpendicular
intersecting angles of adjacent loop strips, the corners of the loops are L-
configured,
that is to say, L-comered.
[0033] The loop strips of the loops 46 and 48 include a shared set 52 of loop
strips. The loop strips of the shared set are shared between the groups. That
is to say,
the loop strips of the shared set form parts of both groups 46 and 48.
[0034] The shared set, in the exemplary implementation, and as shown,
includes three loop strips, connected end-to-end, including two L-cornered
portions.
[0035] Figure 2 illustrates references 54, 56, 58, 60, 62, 64, 66, and 68. At
each of these reference points, an L-shaped corner of a loop is formed. Due to
the
substantially perpendicular intersections of the adjacent loop strips, the
loop strips
each extend in one of two polarization directions. The polarization directions
are
orthogonal, defmed by the axes 72 and 74. The axis 74 defines a first
polarization
direction, and the axis 72 defines a second polarization direction. Loop
strips that
extend between reference points 64 and 54, between reference points 60 and 58,
between reference points 62 and 68, and between reference points 66 and 56 all
extend in the first polarization direction. Loop strips extending between
reference
points 54 and 56, between reference points 56 and 58, between reference points
64
and 62, between reference points 62 and 60, and between reference points 66
and 68
all extend in the second polarization direction. In the exemplary
implementation, and
as shown, the lengths defming an outer perimeter of a rectangular
configuration
defined by the loop strips are all the same. Additionally, loop strips defined
by points
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54-56, 66-72, and 62-60 are also all of the corresponding lengths. And, in the
exemplary implementation, the widths of each of the loop strips is of the same
width,
w.
[0036] The antenna 32 includes a single feed connection 82 providing a feed
connection point, connectable to the transceiver circuitry (shown in Figure 1)
of the
mobile station (shown in Figure 1). The single feed connection provides a feed
that,
positioned as-illustrated at a mid-point of the loop strip 66-68, provides for
symmetrical excitation of the loops formed of the groups 46 and 48 of loop
strips.
Because only a single feed connection is needed, problems associated with
spacing
requirements required between multiple feed connections, conventionally
required,
are obviated.
[0037] The geometrical configuration of the exemplary implementation of the
antenna 32 shown in Figure 2 provides for three in-phase parallel strips in
each of the
polarization directions 72 and 74. Strips 54-58, 66-68, and 64-60 extend in
the
second polarization direction. And, parallel strips 54-64, 58-60, and 56-66/68-
62
extending in the first polarization direction permit the antenna to exhibit
both high
gain and high efficiency.
[0038] The two groups 46 and 48 of loop strips are etched on a printed circuit
board, or other substrate. The loop strips are regarded as a combination of
two
electrically-connected, multiple L-shaped, rectangular loop strips that have a
common
set of shared strips. In a further implementation, the antenna further
includes a metal
reflector 84 disposed in the strip-loop aperture plane, here disposed beneath
a bottom
surface of the substrate 44.
[0039] Orthogonal, dual-polarization radiation is realized by arranging the
loop strips to extend in directions parallel to one of the axes 72 or 74. The
feed
connection 82, located at the center of the loop strip 66-68, provides for
symmetrical
excitation, thereby to reduce cross-polarization levels of the dual-
polarization
components. The loop strips extending in each of the polarization directions
are
arranged into an in-phase, three-element array that provides high gain levels.
The
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current, i.e., charge flow, direction during operation of the antenna reverses
at half-
wavelength intervals due to standing wave distributions along the strips.
Additionally, each side of the outer-perimetal loop is divided equivalently
into three
sections, thereby to produce an in-phase current distribution on all of the
strip sections
5 if the length of the perimetal loop is appropriately chosen.
[0040] Figure 3 illustrates a graphical representation 92 illustrating plots
94
and 96 that are representative of simulated and measured return losses,
respectively,
plotted as a function of frequency. In the exemplary implementation, the
antenna is
resonant at the 2.4 GHz frequency band, and the plots are indicative thereof.
10 [0041 ] Figure 4 again illustrates the antenna 32 of an exemplary
embodiment
of the present invention. Here, a simulated current distribution exhibited by
the
antenna at its resonant frequency of 2.47 GHz. The antenna headers represent
the
current in the antenna. Analysis of the current distribution indicates that
the current
distribution is in directions parallel to the polarization axes 72 and 74
shown in Figure
2.
[0042] Figures 5 and 6 illustrate, respectively, simulated and measured, two-
dimensional, radiation patterns of the antenna 32 of an embodiment of the
present
invention at its 2.47 GHz resonant frequency. In each representation, both
zero and
ninety degree-plane representations 102 and 104 are plotted.
[0043] Figure 7 illustrates a graphical representation 106 illustrating
simulated
gain, as a function of frequency, exhibited by the antenna 32 of an embodiment
of the
present invention. The gain is centered at, or close to, the 2.47 GHz resonant
frequency.
[0044] Figure 8 illustrates a method flow diagram, shown generally at 112,
representative of the method of operation of an embodiment of the present
invention.
The method is for transducing signal energy at a radio device.
[0045] First, and as indicated by the block 114, a first group of loop strips
are
disposed upon a substrate. The loop strips of the first group are configured
to form a
first loop having at least one strip extending in a first polarization
direction and at
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least one strip extending in a second polarization direction. And, as
indicated by the
block 116, a second group of loop strips are disposed upon the substrate. The
loop
strips of the second group are configured to form a second loop having at
least one
strip extending in the first polarization direction and at least one strip
extending in the
second polarization direction.
[0046] Once formed on the substrate, the loop strips are used to transduce
signal energy, polarized in the polarization direction and in the second
polarization
direction, at the first and second groups, respectively, of the loop strips.
[0047] Thereby, a dual-polarized antenna, of compact dimensions is provided.
Through the use of loop strips disposed upon a substrate, configured in a
manner to
permit use of a single feed connection to symmetrically excite the antenna, so-
configured, obviates the problems associated with multiple feed connections
used by
conventional dual-polarized antennas are obviated.
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