Note: Descriptions are shown in the official language in which they were submitted.
CA 02532823 2006-02-03
MOBILE WIRELESS COMMUNICATIONS DEVICE PROVIDING PATTERN/
FREQUENCY CONTROL FEATURES AND RELATED METHODS
Field of the Invention
The present invention relates to the field of communications systems, and,
more
particularly, to wireless communications systems and related methods.
Background of the Invention
Computers are often connected together as part of a Local Area Network (LAN).
The LAN permits computers to share data and programs with one another. Many
typical
LANs are based upon physical connections between individual computers and a
server, for
example. The connections may be twisted pair conductors, coaxial cables, or
optical
fibers, for example.
There is also another class of LAN based upon wireless communication to the
individual computers. A wireless LAN is not restricted to having physical
connections to
the individual computers. Accordingly, original installation may be
simplified.
Additionally, one or more of the computers may be used in a mobile fashion. In
other
words, the user may use a laptop computer and move from place to place while
still being
connected via the wireless LAN.
Various standards have been created to define operating protocols for wireless
LANs, such as the IEEE 802.11 and Bluetooth standards. The IEEE 802.11
standard, for
example, defines the protocol for several types of networks including ad-hoc
and
clientlserver networks. An ad-hoc network is a network where communications
are
established between multiple stations in a given coverage area without the use
of an access
point or server. The standard provides methods for arbitrating requests to use
the medium
to ensure that throughput is maximized for all of the users in the base
service set.
The client/server network uses an access point that controls the allocation of
transmit time for all stations and allows mobile stations to roam from one
access point to
another. The access point is used to handle traffic from the mobile radio to
the wired or
wireless backbone of the client/server network. This arrangement allows for
point
coordination of all of the stations in the basic service area and ensures
proper handling of
the data traffic. The access points route data between each station and other
wired/wireless
stations, or to and from the network server (i.e., a base station). Of course,
two or more
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LANs may be interconnected using wireless LAN devices at respective access
points. This
may be considered a network bridge application.
One of the challenges of wireless LAN implementation is designing suitable
antennas that can provide desired performance characteristics, yet are
relatively small in
size to fit within mobile devices. For example, with wireless LAN devices such
as laptop
computers, it is desirable to keep the overall size of the laptop as small as
possible.
Furthermore, internal antennas are generally preferred over external antennas,
as
externally mounted antennas take up more space and are generally more
acceptable to
damage while traveling, etc.
One example of a wireless LAN antenna that is implemented on a PMCIA card to
be inserted in a PMCIA slot of a laptop computer is disclosed in U.S. Patent
No. 6,031,503 to Preiss, II et al. The antenna assembly includes two folded, U-
shaped
antennas, which may be dipoles or slot radiators, that are disposed
orthogonally to one
another to provide polarization diversity. Polarization diversity means that
signals are
transmitted and received on two different polarizations to increase the
likelihood that the
signal is received. Signals are carried to and from the antenna by microstrip
feed lines. The
microstrip lines are placed off center along each antenna slot to establish an
acceptable
impedance match for the antenna, and the feed lines are coupled to the
communications
card by coaxial cables.
Another exemplary wireless LAN antenna configuration is disclosed in U.S.
Patent
No. 6,624,790 to Wong et al. This patent discloses first and second dual-band
printed
monopole antennas which are disposed orthogonally to one another on a
substrate. The
antenna elements are the same shape (i.e., an "F" shape). In particular, the
antenna
elements provide 2.4 GHz and 5.2 GHz WLAN operation.
There is an increasing trend toward using other portable, handheld
communications
devices in wireless LANs which are even smaller than laptops, such as personal
digital
assistants (PDAs) and cellular phones, for example. Accordingly, with even
more
restrictive space constraints for such handheld devices, there is a need for
antennas which
are appropriately sized for such applications yet still provide desired
performance
characteristics.
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CA 02532823 2006-02-03
Summary of the Invention
In view of the foregoing background, it is therefore an object of the present
invention to provide a mobile wireless communications device including an
antenna
system which provides desired performance using frequency/pattern diversity
and related
methods.
This and other objects, features, and advantages in accordance with the
present
invention are provided by a mobile wireless communications device which may
include a
frequency/pattern diversity controller. The mobile wireless communications
device may
further include a portable housing, a wireless transceiver carried by the
portable housing,
and a plurality of antennas also carned by the portable housing. Each antenna
may have a
different gain pattern at a different respective operating frequency, and the
antennas may
have different shapes to define different gain patterns at a given operating
frequency.
Moreover, the frequency/pattern diversity controller may control the wireless
transceiver
to preferentially operate with the plurality of antennas.
More particularly, the frequency/pattern diversity controller may control the
wireless transceiver to preferentially switch at least one antenna on and at
least one
antenna off for receiving signals. Thus, a given antenna may be selected for
receiving if its
respective gain pattern at the given operating frequency provides better
reception than the
other antennas. Alternately, the frequency/pattern diversity controller may
control the
wireless transceiver to preferentially weight received signals.
In addition, the frequency/pattern diversity controller may control the
wireless
transceiver to preferentially switch at least one antenna on and at least one
antenna off for
transmitting signals. Furthermore, each antenna may be designated for
transmitting signals
at different respective operating frequencies, and the frequency/pattern
diversity controller
may control the wireless transceiver to preferentially switch the antennas on
and off for
transmitting signals based upon a given operating frequency.
The different gain patterns may comprise different gain patterns for different
polarizations in some embodiments. Further, each antenna may have a respective
boresight
aligned in a common direction. The mobile wireless communications device may
further
include a circuit board carried by the portable housing and carrying the
wireless
transceiver, and it may also carry the frequency/pattern diversity controller.
Moreover, at
least one of the antennas may comprise a conductive trace on the circuit
board. That is, at
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least one of the antennas may be carried within the portable housing. By way
of example,
the wireless transceiver may be a wireless local area network (LAN)
transceiver.
A method aspect of the invention is for operating a mobile wireless
communications device, such as the one described briefly above. The method may
include
controlling the wireless transceiver to preferentially operate with the
plurality of antennas
to provide frequency/pattern diversity.
Brief Description of the Drawings
FIG. 1 is a schematic block diagram of a mobile wireless communications device
in accordance with the present invention.
FIG. 2 is an end view of the circuit board of the mobile wireless
communications
device of FIG. 1 illustrating respective boresights of the antenna thereon.
FIG. 3 is a front elevational view of an exemplary embodiment of the antennas
of
the mobile wireless communications device of FIG. 1 illustrating respective
polarizations
thereof.
FIGS. 4 and 5 are flow diagrams illustrating methods of operating a mobile
wireless communications device in accordance with the present invention.
FIG. 6 is a schematic block diagram illustrating exemplary components of a
mobile
wireless communications device in accordance with the present invention.
Detailed Description of the Preferred Embodiments
The present invention will now be described more fully hereinafter with
reference
to the accompanying drawings, in which preferred embodiments of the invention
are
shown. This invention may, however, 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 be thorough and
complete, and will
fully convey the scope of the invention to those skilled in the art. Like
numbers refer to
like elements throughout and prime notation is used to indicate similar
elements or steps in
different embodiments.
Referring initially to FIGS. 1-3, a mobile wireless communications device 20
in
accordance with the present invention illustratively includes a portable
housing 21, a
wireless transceiver 22 carried by the portable housing, and a plurality of
antennas 23, 24
also carried by the portable housing. In the illustrated embodiment, the
wireless
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CA 02532823 2006-02-03
transceiver 22 is a wireless local area network (LAN) transceiver for
communicating over
a wireless LAN 27. However, it should be noted that in other embodiments the
mobile
wireless communications device 20 may be used with other wireless
communication
networks, such as a cellular telephone network, for example. The antennas 23
and 24 are
referred to herein as the first and second antennas, respectively, for clarity
of explanation.
The wireless transceiver 22 and first and second antennas 23, 24 may be
carried by
a circuit board 25, such as a printed circuit board (PCB), for example. More
particularly,
the first and second antennas 23, 24 may comprise printed conductive traces on
the circuit
board 25. In other embodiments, the first and second antenna elements 23, 24
need not be
on the circuit board 25, but may instead be on a separate antenna substrate,
which need not
be co-planar with the circuit board. Of course, portions of either antenna
element 23, 24
may be on both the circuit board ZS and a separate antenna substrate. In still
another
embodiment, one or more of the antennas 23, 24 may be carned on the exterior
of the
housing 21, for example.
Despite the particular configuration in a given embodiment, each antenna 23,
24
preferably has a different gain pattern at a different respective operating
frequency, and
they preferably have different shapes to define different gain patterns at a
given operating
frequency. Moreover, the mobile wireless communications device 20 further
illustratively
includes a frequency/pattern diversity controller 26 for controlling the
wireless transceiver
22 to preferentially operate with the antennas 23, 24. That is, the controller
26
advantageously provides frequency/pattern diversity by controlling the
frequency and/or
gain pattern used for either transmission or reception.
By way of example, the wireless LAN 27 may utilize multiple operating
frequency
bands such as a 2.4 GHz frequency band (i.e., approximately 2.4 to 2.483 GHz)
and a 5
GHz frequency band (i.e., approximately 4.9 to 6 GHz), as will be appreciated
by those
skilled in the art. Because the 5 GHz frequency band is roughly double the 2.4
GHz
frequency band, it is possible to make each of the antennas 23, 24 resonate in
both
frequency bands. This may be done by varying the effective length of the
antennas 23, 24
using appropriate design techniques for the given antenna types used, as will
be
appreciated by those skilled in the art.
Thus, in accordance with the present example, both of the antennas 23, 24 are
designed to resonate in both the 2.4 and 5 GHz frequency bands, but they each
have
different gain patterns in the two frequency bands, and the gain patterns of
each antenna
CA 02532823 2006-02-03
are different from the gain patterns of the other antenna at a given operating
frequency.
More particularly, the first antenna 23 is designed so that its maximum gain
along its
boresight 28 (FIG. 2) occurs at the 2.4 operating frequency, while the maximum
gain of
the second antenna 24 along its boresight 29 occurs at the 5 GHz operating
frequency.
Preferably, the respective boresights 28, 29 are aligned in a common
direction, such as at a
same angle a (e.g., 90°) with respect to the circuit board 25, as shown
in FIG. 2. It should
be noted that the antenna elements 23, 24 are shown with hatching in FIG. 2
for clarity of
illustration, even though this is not a cross-sectional view.
As such, the frequency/pattern diversity controller 26 may control the
wireless
transceiver 22 to preferentially switch one of the antennas 23, 24 on and the
other off for
receiving signals based upon which antenna's gain pattern is providing the
best reception.
The frequency/pattern controller 26 may make this determination based upon
signal
strength or noise measurements, for example, as will be appreciated by those
skilled in the
art. Thus, a given one of the antennas 23, 24 may be selected for receiving if
its respective
gain pattern at the given operating frequency provides better reception than
the other
antenna.
Alternately, rather than using one of the antennas 23, 24 and not the other,
the
frequency/pattern diversity controller 26 may control the wireless transceiver
22 to
preferentially weight received signals. Thus, based upon signal strength and
noise
considerations, for example, the frequency/pattern diversity controller 26 may
control the
wireless LAN transceiver to weight the signals received by each of the first
and second
antennas 23, 24.
The frequency/pattern diversity controller 26 may similarly control the
wireless
transceiver 22 to preferentially operate the antennas 23, 24 during
transmission. That is,
the frequency/pattern diversity controller 26 may control the wireless
transceiver 22 to
preferentially switch one of the antennas 23, 24 on and the other off for
transmitting
signals. More particularly, each of the antennas 23, 24 may designated for
transmitting
signals at different respective operating frequencies.
For example, the first antenna 23 may be designated for transmitting in the
2.4
GHz frequency band, while the second antenna 24 may be designated for
transmitting in
the 5.2 GHz band, as will be discussed further below. Of course, both antennas
23, 24
could be used for transmitting signals and their outputs weighted, as
similarly discussed
for received signals above. Thus, the frequency/pattern diversity controller
26 may
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CA 02532823 2006-02-03
preferentially switch the antennas 23, 24 on and off for transmitting signals
based upon the
given operating frequency (i.e., the 2.4 GHz or S GHz frequency band) being
used by the
receiving wireless LAN device (e.g., an access point, etc.).
The mobile wireless communications device 20 therefore not only provides
frequency/pattern diversity, but it may also provide polarization diversity in
certain
embodiments. That is, the different gain patterns of the first and second
antennas 23, 24
may comprise different gain patterns for different polarizations. As shown in
FIG. 3, for
example, the first antenna 23 has substantially horizontal polarization as
illustrated by a
dashed arrow 30, while the second antenna 24 has a substantially vertical
polarization as
illustrated by a dashed arrow 31. Of course, other polarization arrangements
may also be
used.
In the illustrated example, the first antenna 23 is a monopole antenna with a
single
feed point connected to a signal source 32 (i.e., the wireless transceiver).
The second
antenna 24 is a slot inverted F antenna which has a first feed point connected
to the signal
source 32, and a second feed point connected to ground. The monopole antenna
24 has a
meandering shape in the illustrated example, which may be used to change the
effective
length, for example. However, various other shapes (including a straight
conductor) and
antenna types may also be used in accordance with the present invention, as
will be
appreciated by those skilled in the art.
Because the first antenna 23 is a single feed antenna, it will have a stronger
current
flow on the circuit board 25 than the second antenna 24, it is well suited for
providing the
maximum gain along the boresight 28 at the 2.4 GHz operating frequency. On the
other
hand, because the antenna 24 has multiple feed points the current distribution
on the
circuit board 25 will be more limited, it is well suited for providing a
maximum gain along
the boresight 29 at the 5 GHz operating frequency, as will be appreciated by
those skilled
in the art. It should be noted that more than two antennas element may be used
in some
embodiments, and that in such embodiments the frequency/pattern diversity
controller 26
need not control the wireless transceiver to preferentially operate all of
such antennas.
Moreover, the antennas 23, 24 need not always be adjacent the top of the
device 20, e.g.,
one or more of the antennas may be adjacent the bottom of the device.
A method aspect of the invention for operating the mobile wireless
communications device 20 is now described with reference to FIG. 4. Beginning
at Block
40, a determination is made as to which operating frequency or frequency band
is to be
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used, at Block 41. Using the above noted example, when the device ZO is first
turned on it
may attempt to establish communications with the wireless LAN 27 over both the
2.4 and
GHz frequency bands, as will be appreciated by those skilled in the art. If
the wireless
LAN 27 is using the first (2.4 GHz) operating frequency band, then the first
antenna 23
(which is the designated or default antenna for transmitting in this frequency
band) is
switched on and the second antenna 24 is switched off, at Block 42.
Furthermore, the frequency/pattern diversity controller 26 may determine which
antenna 23, 24 is providing better reception, as discussed above, and switch
that antenna
on and the other off for receiving wireless signals, at Blocks 43-45, thus
concluding the
illustrated method (Block 46). Similar steps to those illustrated in Blocks 42-
45 would be
performed if the wireless LAN was using the second (SGHz) operating frequency
band
(which are not shown in FIG. 4 for clarity of illustration) as will be
appreciated by those
skilled in the art.
In an alternate embodiment illustrated in FIG. 5, rather than initially
determining
which antenna 23, 24 provides better reception as described above with
reference to Block
43, each antenna may be designated as the initial (or default) receiving
antenna for a given
operating frequency band (e.g., the first antenna 23 for the 2.4 GHz frequency
band, and
the second antenna 24 for the 5 GHz frequency band), over that at Block 50'.
If the
reception quality (e.g., signal strength) using the default antenna 23 remains
above a
desired threshold over the first operating frequency band, at Block 51', then
the first
antenna would continue to be used, at Block 52'. However, if the received
signal strength
fell below the desired threshold, then the second antenna 24 may be used, or
the received
signals from both the first and second antennas weighted accordingly, at Block
53', as
discussed further above. Of course, the above described method steps are
merely
exemplary, and different variations may be used in other embodiments. For
example, the
reception quality may be determined based upon whether a noise level or bit
error rate
exceeds a threshold, for example.
Exemplary components which may be used in accordance with the present
invention are now described with reference to a handheld mobile wireless
communications
device 1000 is shown in FIG. 6. The device 1000 includes a housing 1200, a
keyboard
1400 and an output device 1600. The output device shown is a display 1600,
which is
preferably a full graphic LCD. Other types of output devices may alternatively
be utilized.
A processing device 1800 is contained within the housing 1200 and is coupled
between
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the keyboard 1400 and the display 1600. The processing device 1800 controls
the
operation of the display 1600, as well as the overall operation of the mobile
device 1000,
in response to actuation of keys on the keyboard 1400 by the user.
The housing 1200 may be elongated vertically, or may take on other sizes and
shapes (including clamshell housing structures). The keyboard may include a
mode
selection key, or other hardware or software for switching between text entry
and
telephony entry.
In addition to the processing device 1800, other parts of the mobile device
1000 are
shown schematically in FIG. 6. These include a communications subsystem 1001;
a short-
range communications subsystem 1020; the keyboard 1400 and the display 1600,
along
with other input/output devices 1060, 1080, 1100 and 1120; as well as memory
devices
1160, 1180 and various other device subsystems 1201. The mobile device 1000 is
preferably a two-way RF communications device having voice and data
communications
capabilities. In addition, the mobile device 1000 preferably has the
capability to
communicate with other computer systems via the Internet.
Operating system software executed by the processing device 1800 is preferably
stored in a persistent store, such as the flash memory 1160, but may be stored
in other
types of memory devices, such as a read only memory (ROM) or similar storage
element.
In addition, system software, specific device applications, or parts thereof,
may be
temporarily loaded into a volatile store, such as the random access memory
(RAM) 1180.
Communications signals received by the mobile device may also be stored in the
RAM
1180.
The processing device 1800, in addition to its operating system functions,
enables
execution of software applications 1300A-1300N on the device 1000. A
predetermined set
of applications that control basic device operations, such as data and voice
communications 1300A and 1300B, may be installed on the device 1000 during
manufacture. In addition, a personal information manager (PIM) application may
be
installed during manufacture. The PIM is preferably capable of organizing and
managing
data items, such as e-mail, calendar events, voice mails, appointments, and
task items. The
PIM application is also preferably capable of sending and receiving data items
via a
wireless network 1401. Preferably, the PIM data items are seamlessly
integrated,
synchronized and updated via the wireless network 1401 with the device user's
corresponding data items stored or associated with a host computer system.
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Communication functions, including data and voice communications, are
performed through the communications subsystem 1001, and possibly through the
short-
range communications subsystem. The communications subsystem 1001 includes a
receiver 1500, a transmitter 1520, and one or more antennas 1540 and 1560. In
addition,
the communications subsystem 1001 also includes a processing module, such as a
digital
signal processor (DSP) 1580, and local oscillators (LOs) 1601. The specific
design and
implementation of the communications subsystem 1001 is dependent upon the
communications network in which the mobile device 1000 is intended to operate.
For
example, a mobile device 1000 may include a communications subsystem 1001
designed
to operate with the MobitexTM, Data TACTM or General Packet Radio Service
(GPRS)
mobile data communications networks, and also designed to operate with any of
a variety
of voice communications networks, such as AMPS, TDMA, CDMA, PCS, GSM, etc.
Other types of data and voice networks, both separate and integrated, may also
be utilized
with the mobile device 1000.
Network access requirements vary depending upon the type of communication
system. For example, in the Mobitex and DataTAC networks, mobile devices are
registered on the network using a unique personal identification number or PIN
associated
with each device. In GPRS networks, however, network access is associated with
a
subscriber or user of a device. A GPRS device therefore requires a subscriber
identity
module, commonly referred to as a SIM card, in order to operate on a GPRS
network.
When required network registration or activation procedures have been
completed,
the mobile device 1000 may send and receive communications signals over the
communication network 1401. Signals received from the communications network
1401
by the antenna 1540 are routed to the receiver 1500, which provides for signal
amplification, frequency down conversion, filtering, channel selection, etc.,
and may also
provide analog to digital conversion. Analog-to-digital conversion of the
received signal
allows the DSP 1580 to perform more complex communications functions, such as
demodulation and decoding. In a similar manner, signals to be transmitted to
the network
1401 are processed (e.g. modulated and encoded) by the DSP 1580 and are then
provided
to the transmitter 1520 for digital to analog conversion, frequency up
conversion, filtering,
amplification and transmission to the communication network 1401 (or networks)
via the
antenna 1560.
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In addition to processing communications signals, the DSP 1580 provides for
control of the receiver 1500 and the transmitter 1520. For example, gains
applied to
communications signals in the receiver 1500 and transmitter 1520 may be
adaptively
controlled through automatic gain control algorithms implemented in the DSP
1580.
In a data communications mode, a received signal, such as a text message or
web
page download, is processed by the communications subsystem 1001 and is input
to the
processing device 1800. The received signal is then further processed by the
processing
device 1800 for an output to the display 1600, or alternatively to some other
auxiliary I/O
device 1060. A device user may also compose data items, such as e-mail
messages, using
the keyboard 1400 and/or some other auxiliary I/O device 1060, such as a
touchpad, a
rocker switch, a thumb-wheel, or some other type of input device. The composed
data
items may then be transmitted over the communications network 1401 via the
communications subsystem 1001.
In a voice communications mode, overall operation of the device is
substantially
similar to the data communications mode, except that received signals are
output to a
speaker 1100, and signals for transmission are generated by a microphone 1120.
Alternative voice or audio I/O subsystems, such as a voice message recording
subsystem,
may also be implemented on the device 1000. In addition, the display 1600 may
also be
utilized in voice communications mode, for example to display the identity of
a calling
party, the duration of a voice call, or other voice call related information.
The short-range communications subsystem enables communication between the
mobile device 1000 and other proximate systems or devices, which need not
necessarily
be similar devices. For example, the short-range communications subsystem may
include
an infrared device and associated circuits and components, or a Bluetooth
communications
module to provide for communication with similarly-enabled systems and
devices.
Many modifications and other embodiments of the invention will come to the
mind
of one skilled in the art having the benefit of the teachings presented in the
foregoing
descriptions and the associated drawings. Therefore, it is understood that the
invention is
not to be limited to the specific embodiments disclosed, and that
modifications and
embodiments are intended to be included within the scope of the appended
claims.
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