Note: Descriptions are shown in the official language in which they were submitted.
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MOBILE WIRELESS COMMUNICATIONS DEVICE INCLUDING A SLOT ANTENNA
AND RELATED METHODS
Technical Field
[0001] The present disclosure generally relates to the field
of wireless communications systems, and, more particularly, to
mobile wireless communications devices and related methods.
Background of the Invention
[0002] Mobile wireless communications systems continue to
grow in popularity and have become an integral part of both
personal and business communications. For example, cellular
telephones allow users to place and receive voice calls almost
anywhere they travel. Moreover, as cellular telephone technology
has increased, so too has the functionality of cellular devices
and the different types of devices available to users. For
example, many cellular devices now incorporate personal digital
assistant (PDA) features such as calendars, address books, task
lists, etc. Moreover, such multi-function devices may also allow
users to wirelessly send and receive electronic mail (email)
messages and access the Internet via a cellular network and/or a
wireless local area network (WLAN), for example.
[0003] Even so, as the functionality of cellular
communications devices continues to increase, so too does the
demand for smaller devices which are easier and more convenient
for users to carry. One challenge this poses for cellular device
manufacturers is designing housings that cooperate with antennas
to provide desired operating characteristics within the
relatively limited amount of space available.
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Brief Description of the Drawings
[0004] FIG. 1 is a top plan view of a mobile wireless
communications device including an electrically conductive
enclosure having a slot therein defining a slot antenna in
accordance with one example embodiment.
[0005] FIG. 2 is a schematic block diagram of a portion of
the device of FIG. 1.
[0006] FIG. 3 is a side schematic view of the portion of the
device in FIG. 2.
[0007] FIG. 4 is a perspective view of a portion of a device
including an antenna feed in accordance with another example
embodiment.
[0008] FIG. 5 is a graph of measured return loss for a
prototype mobile wireless communications device without a tuning
element.
[0009] FIG. 6 is a graph of measured gain for the prototype
mobile wireless communications device without a tuning element.
[0010] FIG. 7 is a graph of measured return loss for a
prototype mobile wireless communications device with a FR-4
tuning element.
[0011] FIG. 8 is a graph of measured gain for the prototype
mobile wireless communications device with the FR-4 tuning
element.
[0012] FIG. 9 is a graph of measured return loss for a
prototype mobile wireless communications device with a TDK
ceramic tuning element.
[0013] FIG. 10 is a graph of measured gain for the prototype
mobile wireless communications device with the TDK ceramic
tuning element.
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[0014] FIG. 11 is a schematic block diagram illustrating
additional components that may be included in the mobile
wireless communications device of FIG. 1.
Detailed Description of the Preferred Embodiments
[0015] 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 alternative
embodiments.
[0016] In accordance with one exemplary aspect, a mobile
wireless communications device may include a portable housing
and a printed circuit board (PCB) carried by the portable
housing. The mobile wireless communications device may also
include at least one electronic component carried by the PCB and
an electrically conductive enclosure coupled to the PCB and
having a top spaced above the PCB over the at least one
electronic component. The top of the electrically conductive
enclosure may have a slot therein defining a slot antenna.
[0017] The mobile wireless communications device may further
include a tuning element carried by the electrically conductive
enclosure and being positioned over the slot, for example. The
tuning element may include a dielectric material body. The
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-tuning element may further include a conductive material layer
on the dielectric material body, for example.
[0018] The slot may include a base slot, and first and second
parallel slots extending in opposite directions from the base
slot. The base slot may have opposing ends, and the first and
second parallel slots may extend from the opposing ends, for
example.
[0019] The electrically conductive enclosure may further
include a sidewall depending from the top, for example. The
mobile wireless communications device may further include at
least one antenna feed carried by the PCB and coupled to the
electrically conductive enclosure adjacent the slot. The at
least one antenna feed may include a pair of antenna feeds
coupled to the electrically conductive enclosure on opposing
sides of the slot, for example. The at least one antenna feed
may include at least one of a flexible stripline and a spring
contact.
[0020] The mobile wireless communications device of may
further include a conductive layer carried by the PCB defining a
ground plane, for example. The electrically conductive
enclosure is carried above the ground plane.
[0021] A method aspect is directed to a method of making a
mobile wireless communications device that may include a
portable housing, a printed circuit board (PCB) carried by the
portable housing, and at least one electronic component carried
by the PCB. The method may include forming a slot in a top of
an electrically conductive enclosure to be coupled to the PCB to
form a slot antenna. The top may be spaced above the PCB over
the at least one electronic component.
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[0022] Referring initially to FIGS. 1-3, a mobile wireless
communications device 30 illustratively includes a portable
housing 31 a printed circuit board (PCB) 32, carried by the
portable housing. The PCB 32 also includes a conductive layer
46 defining a ground plane (FIG. 3).
[0023] The exemplary device 30 further illustratively
includes a display 60 and a plurality of control keys including
an "off hook" (i.e., initiate phone call) key 61, an "on hook"
(i.e., discontinue phone call) key 62, a menu key 63, and a
return or escape key 64. Operation of the various device
components and input keys, etc., will be described further below
with reference to FIG. 11.
[0024] The wireless communications device 30 also includes
electronic components 33a-33n carried by PCB 32. The electronic
components 33a-33n may include wireless communications circuitry
configured to perform a wireless communications function, for
example, wireless voice or data communications. Other
circuitry, for example, discrete components, associated with the
mobile wireless communications device 30 may also be carried by
the PCB 32.
[0025] An electrically conductive enclosure 34 is coupled to
the PCB 32 and carried above the ground plane 46. The
electrically conductive enclosure 34 includes a top 47 spaced
above PCB 32 over the electronic components 33a-33n. The
electrically conductive enclosure 34 also includes a sidewall 37
depending from the top 47.
[0026] The top 47 of the electrically conductive enclosure 34
has a slot 35 therein defining a slot antenna. The slot 35
illustratively includes a base slot 36 having opposing ends 41,
42. First and second parallel slots 43, 44 extend in opposite
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directions from the opposing ends 41, 42 of the base slot 36.
The slot 35 may extend in other directions, but it may be
desirable that the slot does not "double over" on itself as this
may reduce antenna efficiency and thus performance. The
electrically conductive enclosure 34 may have additional slots
or openings for ventilation, which may be relatively small
compared to the slot 35. Moreover, the electrically conductive
enclosure 34 may have more than one slot therein defining more
than one slot antenna.
[0027] The length of the slot 35 determines the operating
frequency of the slot antenna. The position of the electrically
conductive enclosure 34 with respect to the ground plane 46 is
another variable that may affect performance of the slot
antenna.
[0028] For the slot antenna to operate in the correct mode
for the frequency of operation and to give the desired
bandwidth, it is desirable that the slot 35 be the correct
length, the electrically conductive enclosure 34 surrounding the
slot 35 is large enough to support circulating currents around
the slot, and the cavity, i.e. the distance of the slot and the
electrically conductive enclosure 34 above the PCB 32, has
sufficient depth. Physical restraints of the mechanics of the
mobile wireless communications device 30 may hamper obtaining of
desired characteristics.
[0029] To compensate for the increased difficulty of
obtaining desired characteristics because of the physical
constraints, i.e. size, the mobile wireless communications
device 30 includes a tuning element 50 carried by the
electrically conductive enclosure 34. The tuning member 50
loads the slot 35 as a parasitic element. The tuning element 50
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is illustratively positioned over the slot 35, and more
particularly, bridges or spans the slot 35. The tuning member
50 includes a dielectric material body 51 and may have a
relatively high dielectric constant, for example. For example,
the dielectric material body 51 may be FR-4 dielectric material
or a ceramic material. Of course, the dielectric material body
51 may include other dielectric materials.
[0030] The tuning element 50 may also optionally include a
conductive material layer 52 on the dielectric material body 51.
The conductive material layer 52 may be copper, for example.
The conductive material layer 52 may be another conductive
material, as will be appreciated by those skilled in the art.
More than one tuning element may be used, as will be appreciated
by those skilled in the art.
[0031] The thickness of the tuning element 50 may be
particularly useful for determining gain and return loss of the
slot antenna. The height of the slot 35 and the tuning element
50 above the PCB 32 also determines the gain or return loss.
The thickness of the tuning element 50 and the height of the
tuning element and the slot 35 above the PCB may be the primary
adjustments for determining gain or return loss. The position
of the electrically conductive enclosure 34 in the X-Y plane on
the ground plane 46, and the X-Y position of the tuning element
50 may also determine the gain or return loss of the slot
antenna. As will be appreciated by those skilled in the art,
the height of the tuning element 50 and the electrically
conductive enclosure 34 may be adjustable via an adjustment
mechanism. This may accommodate in-situ adjustment and thus,
different gain patterns, for example.
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[0032] The slot antenna may be particularly useful for
operating in the IEEE 802.11a frequency band of approximately
5.2 GHz to 5.8 GHz. As will be appreciated by those skilled in
the art, mounting a slot antenna on the electrically conductive
enclosure 34 advantageously helps ease the problem of finding
the room or space within the portable housing 31. As the IEEE
802.11a standard describes a single band antenna, moving it away
from a clear area onto the PCB, for example, may be particularly
useful as it would leave more room for multi-band antennas,
which are typically more difficult to implement.
[0033] A pair of antenna feeds in the form of spring contacts
53a, 53b are carried by the PCB 32 and coupled to the
electrically conductive enclosure 34 adjacent the slot 35, and
more particularly, on opposing sides of the slot.
[0034] The location where the pair of spring contacts 53a,
53b coupled to the electrically conductive enclosure 34 adjacent
the slot 35 determines multiple resonances, as will be
appreciated by those skilled in the art. In particular, one
resonance may be obtained by coupling the pair of spring
contacts 53a, 53b adjacent the center of the slot 35 with
respect to its length. If the pair of spring contacts 53a, 53b
are coupled off-center of the slot with respect to its length,
multiple resonance may be obtained.
[0035] Referring now to FIG. 4 in another example embodiment,
the antenna feeds are in the form of flexible striplines 53a',
53b'. The flexible striplines 53a', 53b' are illustratively
bent over in a c-shape. An outer portion of one of the flexible
striplines 53a' is trimmed back to expose a center portion 55'.
The center portion 55' couples to the electrically conductive
enclosure 34' adjacent the slot 35' and crosses over the slot.
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The second flexible stripline 53b', couples to the ground plane
46'. In one embodiment, the second flexible stripline 53b' is
53mm away from the first flexible stripline 53a'. The second
flexible stripline 53b' does not cross the slot 35', but rather
couples to the electrically conductive enclosure 34'. The pair
of antenna feeds 53a', 53b' may be another type of feed, for
example, pogo pins, or other mechanical structure and may be
coupled in another arrangement, as will be appreciated by those
skilled in the art.
[0036] Referring now to the graphs in FIGS. 5-6, a measured
return loss graph and an antenna gain graph for a prototype
mobile wireless communications device similar to that described
above with respect to FIG. 1, but without a tuning element are
respectively illustrated. Referring now the graphs in FIGS. 7-
8, a measured return loss graph and antenna gain graph for the
prototype mobile wireless communications device including a
tuning element are respectively illustrated. The tuning element
was a FR-4 dielectric material strip that measured 9 mm x 3 mm
by 4 mm and was positioned in the center of the slot with
respect to it length and width. A layer of copper was carried
by the FR-4.
[0037] Referring now the graphs in FIGS. 9-10, a measured
return loss graph and antenna gain graph for the prototype
mobile wireless communications device including a tuning element
are respectively illustrated. The tuning element was a TDK
ceramic dielectric material that measured 30 mm x 8 mm by 1 mm
and was positioned equally over the slot with respect to it
length and width. The TDK ceramic dielectric material had a
dielectric constant of 6.2.
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[0038] A method aspect is directed to a method of making a
mobile wireless communications device 30 that includes a
portable housing 31, a printed circuit board 32 (PCB) carried by
the portable housing, and electronic components 33a-33n carried
by the PCB. The method also includes forming a slot 35 in a top
47 of an electrically conductive enclosure 34 to be coupled to
the PCB 32 to form a slot antenna. The top 47 is to be spaced
above the PCB 32 over the electronic components 33a-33n.
[0039] Example components of a mobile wireless communications
device 1000 that may be used in accordance with the above-
described embodiments are further described below with reference
to FIG. 11. The device 1000 illustratively includes a housing
1200, a keyboard or keypad 1400 and an output device 1600. The
output device shown is a display 1600, which may comprise 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 the keypad 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
keypad 1400.
[0040] The housing 1200 may be elongated vertically, or may
take on other sizes and shapes (including clamshell housing
structures). The keypad may include a mode selection key, or
other hardware or software for switching between text entry and
telephony entry.
[0041] In addition to the processing device 1800, other parts
of the mobile device 1000 are shown schematically in FIG. 11.
These include a communications subsystem 1001; a short-range
communications subsystem 1020; the keypad 1400 and the display
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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 may comprise a
two-way RF communications device having data and, optionally,
voice communications capabilities. In addition, the mobile
device 1000 may have the capability to communicate with other
computer systems via the Internet.
[0042] Operating system software executed by the processing
device 1800 is 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.
[0043] 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 may be capable of organizing and managing
data items, such as e-mail, calendar events, voice mails,
appointments, and task items. The PIM application may also be
capable of sending and receiving data items via a wireless
network 1401. The PIM data items may be seamlessly integrated,
synchronized and updated via the wireless network 1401 with
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corresponding data items stored or associated with a host
computer system.
[0044] 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, WCDMA, PCS, GSM, EDGE, etc. Other
types of data and voice networks, both separate and integrated,
may also be utilized with the mobile device 1000. The mobile
device 1000 may also be compliant with other communications
standards such as 3GSM, 3GPP, UMTS, 4G, etc.
[0045] 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 typically involves use of a subscriber identity
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.module, commonly referred to as a SIM card, in order to operate
on a GPRS network.
[0046] 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.
[0047] 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.
[0048] 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
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-may also be used to compose data items, such as e-mail messages,
using the keypad 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.
[0049] 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.
[0050] 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, a BluetoothTM communications module to provide for
communication with similarly-enabled systems and devices, or a
near field communications (NFC) sensor for communicating with a
NFC device or NFC tag via NFC communications.
[0051] 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
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specific embodiments disclosed, and that modifications and
embodiments are intended to be included within the scope of the
appended claims.
