[0001] The present invention relates generally to a portable radio device including an antenna
apparatus, 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, the radio housing of
the portable radio device.
[0002] L-comered 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.
Background 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 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, define
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 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.
[0009] EP 1679763A2 discloses multiple dipole antenna elements stacked in dimensions parallel to and/
or perpendicular to the plane of polarization and connected together in a manner that
optimizes the input impedance.
[0011] 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.
[0012] 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
[0013]
Figure 1 illustrates a functional block diagram of a radio communication system in
which an embodiment of the present invention is operable.
Figure 2 illustrates a plan view of a dual-polarized, multiple-strip loop antenna
of an embodiment of the present invention.
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 implementation of the present invention.
Figure 4 illustrates a representation of an exemplary, simulated current distribution
of an antenna of an implementation of the present invention.
Figure 5 illustrates a graphical representation of simulated radiation patterns of
an antenna of an implementation of the present invention at 2.47GHz.
Figure 6 illustrates a graphical representation, similar to that shown in Figure 5,
but of measured radiation patterns exhibited by an antenna of an implementation of
the present invention at 2.47 GHz.
Figure 7 illustrates a graphical representation showing simulated gain as a function
of an antenna of an implementation of the present invention.
Figure 8 illustrates a method flow diagram representative of the method of operation
of an implementation of the present invention.
Detailed Description
[0014] The invention is defined by the independent claims. Embodiments which do not fall
within the scope of the claims do not describe part of the present invention. The
present invention, accordingly, advantageously provides a portable radio device comprising
an 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.
[0015] Through operation of an implementation 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.
[0016] 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.
[0017] 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 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.
[0018] In another aspect of the present invention, a second group of loop strips etched
onto the substrate define a second L-comered 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.
[0019] 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.
[0020] 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 defined, at a loop strip of the shared set. The feed connection is positioned
to permit symmetrical excitation of the two antenna loops. Through the 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.
[0021] 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 first 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.
[0022] 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 lEEE 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.
[0023] The radio communication system includes a network part, here represented by a network
station 14. The network station comprises, for instance, an 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] Figure 2 illustrates in greater detail the antenna 32 of an implementation 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
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.
[0028] 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-cornered.
[0029] 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.
[0030] The shared set, in the exemplary implementation, and as shown, includes three loop
strips, connected end-to-end, including two L-comered portions.
[0031] 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,
defined 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 defining an
outer perimeter of a rectangular configuration defined by the loop strips are all
the same. Additionally, loop strips defined by points 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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 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 if the length of the
perimetal loop is appropriately chosen.
[0036] 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.
[0037] Figure 4 again illustrates the antenna 32 of an exemplary implementation 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.
[0038] Figures 5 and 6 illustrate, respectively, simulated and measured, two-dimensional,
radiation patterns of the antenna 32 of an implementation 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.
[0039] Figure 7 illustrates a graphical representation 106 illustrating simulated gain,
as a function of frequency, exhibited by the antenna 32 of an implementation of the
present invention. The gain is centered at, or close to, the 2.47 GHz resonant frequency.
[0040] Figure 8 illustrates a method flow diagram, shown generally at 112, representative
of the method of operation of an implementation of the present invention. The method
is for transducing signal energy at a radio device.
[0041] 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
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.
[0042] 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.
[0043] 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.