Field of the invention
[0001] The present invention relates generally to antennas for radio communication terminals
and, in particular, to low-profile antennas devised to be incorporated into portable
terminals, and which are capable of operating at different telecommunication frequency
bands.
Background
[0002] Since the end of the 2000
th century the cellular telephone industry has had enormous development in the world.
From the initial analog systems, such as those defined by the standards AMPS (Advanced
Mobile Phone System) and NMT (Nordic Mobile Telephone), the development has during
recent years been almost exclusively focused on standards for digital solutions for
cellular radio network systems, such as D-AMPS (e.g., as specified in EIA/TIA-IS-54-B
and IS-136) and GSM (Global System for Mobile Communications). Different digital transmission
schemes are used in different systems, e.g. time division multiple access (TDMA) or
code division multiple access (CDMA). Currently, the cellular technology is entering
the so called 3
rd generation, providing several advantages over the former, 2
nd generation, digital systems referred to above. Among those advantages an increased
bandwidth will be provided, allowing effective communication of more complex data.
The 3
rd generation of mobile systems have been referred to as the UMTS (Universal Mobile
Telephony System) in Europe and CDMA2000 in the USA, and is already implemented in
Japan to some extent. Furthermore, it is widely believed that the first generation
of Personal Communication Networks (PCNs), employing low cost, pocket-sized, cordless
telephones that can be carried comfortably and used to make or receive calls in the
home, office, street, car, etc., will be provided by, for example, cellular carriers
using the next generation digital cellular system infrastructure.
[0003] One evolution in cellular communication services involves the adoption of additional
frequency bands for use in handling mobile communications, e.g., for Personal Communication
Services (PCS) services. Taking the U.S. as an example, the Cellular hyperband is
assigned two frequency bands (commonly referred to as the A frequency band and the
B frequency band) for carrying and controlling communications in the 800 MHZ region.
The PCS hyperband, on the other hand, is specified in the United States to include
six different frequency bands (A, B, C, D, E and F) in the 1900 MHZ region. Thus,
eight frequency bands are now available in any given service area of the U.S. to facilitate
communication services. Certain standards have been approved for the PCS hyperband
(e.g., PCS1900 (J-STD-007)), while others have been approved for the Cellular hyperband
(e.g., D-AMPS (IS-136)). Other frequency bands in which these devices will be operating
include GPS (operating in the 1.5 GHz range) and UMTS (operating in the 2.0 GHz range).
Each one of the frequency bands specified for the Cellular and PCS hyperbands is allocated
a plurality of traffic channels and at least one access or control channel. The control
channel is used to control or supervise the operation of mobile stations by means
of information transmitted to and received from the mobile stations. Such information
may include incoming call signals, outgoing call signals, page signals, page response
signals, location registration signals, voice channel assignments, maintenance instructions,
hand-off, and cell selection or reselection instructions as a mobile station travels
out of the radio coverage of one cell and into the radio coverage of another cell.
The control and voice channels may operate using either analog modulation or digital
modulation.
[0004] The signals transmitted by a base station in the downlink over the traffic and control
channels are received by mobile or portable terminals, each of which have at least
one antenna. Historically, portable terminals have employed a number of different
types of antennas to receive and transmit signals over the air interface. For example,
monopole antennas mounted perpendicularly to a conducting surface have been found
to provide good radiation characteristics, desirable drive point impedances and relatively
simple construction. Monopole antennas can be created in various physical forms. For
example, rod or whip antennas have frequently been used in conjunction with portable
terminals. For high frequency applications where an antenna's length is to be minimised,
another choice is the helical antenna. In addition, mobile terminal manufacturers
encounter a constant demand for smaller and smaller terminals. This demand for miniaturisation
is combined with desire for additional functionality such as having the ability to
use the terminal at different frequency bands and different cellular systems.
[0005] It is commercially desirable to offer portable terminals which are capable of operating
in widely different frequency bands, e.g., bands located in the 800 MHz, 900 MHz,
1500 MHz, 1800 MHz, 1900 MHz, 2.0 GHz and 2.45 GHz regions. Accordingly, antennas
which provide adequate gain and bandwidth in a plurality of these frequency bands
will need to be employed in portable terminals. Several attempts have been made to
create such antennas. In order to reduce the size of the portable radio terminals,
built-in antennas have been implemented over the last couple of years. The general
desire today is to have an antenna, which is not visible to the customer. Today different
kinds of patches are used, with or without parasitic elements. The most common built-in
antennas currently in use in mobile phones include are the so called planar inverted-F
antennas (PIFA). This name has been adopted du to the fact that the antenna looks
like the letter F tilted 90 degrees in profile. Such an antenna needs a feeding point
as well as a ground connection. If one or several parasitic elements are included
nearby, they can be either grounded or dielectrically separated from ground.
[0006] The trend for future mobile terminals is a continued reduction of size and weight,
and built in type miniature antennas are strongly desired for portable mobile terminals
within 300 MHz-3000 MHz frequency range for this reason. Existing built in type antennas
used in mobile phones includes microstrip antennas and the aforementioned PIFA. Microstrip
antennas are low profile, small in size and light in weight. The PIFA has already
been used in mobile phone handsets and is one of the most promising designs, as suggested
by K.Qassim, "Inverted-F antenna for portable handsets ", IEE Colloqium on Microwave
Filters and Antennas for Personal Communication Systems, pp.3/1-3/6, Feb.1994, London,
UK. However, as the mobile phone becomes smaller and smaller, both conventional microstrip
patch and PIFA antennas are still too large to fit the small phone chassis. This is
particularly problematic when the new generations of phones needs multiple antennas
for cellular, wireless local area network, GPS and diversity.
[0007] Lai, Kin, Yue, Albert et al has published a meandering inverted-F antenna in WO 96/27219.,
by which it is possible to reduce the antenna size to about 40% of conventional PIFA
antennas. In many applications, multi-band performance is needed. In order to make
multi-band built-in antenna, Ying has proposed a printed twin-spiral dual band antenna
in US patent No 6,166,694. The disclosure includes a dual-band built-in antenna having
two strip-line parts which resonant at different frequencies. In that design, the
bandwidth of antenna is smaller because thin strip lines are used as radiators. A
compensation method is therefore also proposed, i.e. a resistor loading is introduced
on the matching bridge, which gives wider bandwidth at the loss of some gain.
[0008] WO 00/36700 discloses a further improved dual band patch antenna, proposed by Ying.
That antenna use the same concept as the printed twin spiral antenna which was stated
in US 6,166,694, the antenna havinh two parts which operate in two frequency ranges.
Instead of using narrow strip, it uses the patches with slot cutting, the slotted
patches are used as radiators, they can offer wider bandwidth.
[0009] For triple band application, the upper band need the band from 1710 MHz to 1990 MHz.
The solution in WO 00/36700 can not meet the requirement. A semi built-in multi-band
printed patch antenna was proposed by Ying in WO 01/17063. That design needs larger
surface area to realise triple band antenna.
In WO 01/91233 Ying has proposed a compact multi-band branch printed antenna. The
antenna can cover tri-band by using a parasitic metal element.
[0010] EP 1113524 A2 discloses a method for coupling a signal to an antenna structure, as
well as to an antenna structure, which comprises at least two antenna elements, a
ground plane for grounding the antenna structure, a coupling line for coupling a first
antenna element and a second antenna element to each other, and a feeding line for
feeding the antenna structure through one feeding point. The first antenna element
is next to the ground plane and perpendicular to the ground plane. The second antenna
element is above the ground plane and parallel to the ground plane. The first antenna
element is arranged to receive information on a reception band of a broadband radio
system and the second antenna element is arranged to transmit information on a transmission
band of said broadband radio system. By arranging the second antenna element to be
adjustable and by adding antenna element to the antenna structure, the antenna structure
according to the invention can be used, for example, in mobile stations of 2nd and
3rd generation mobile communication systems.
[0011] WO 01/91236 A1 discloses multiple frequency band antennas having first and second
conductive branches for use within wireless communications devices, such as radiotelephones.
First and second conductive branches are in adjacent, spaced-apart relationship. First
and second signal feeds extend from the first conductive branch and terminate at respective
first and second switches. Third and fourth signal feeds extend from the second conductive
branch and terminate at respective third and fourth switches. The first and second
conductive branches can jointly radiate as a dipole antenna in a first frequency band
when the first and fourth switches are open, and when the second and third switches
electrically connect the second and third feeds to a first receiver/transmitter. The
antenna structure may be changed by reconfiguring the various switches. For example,
the first and second conductive branches may radiate separately as respective inverted-F
antennas, or may radiate independently as monopole antennas.
[0012] In order to be able to have double-band performance in two telecommunication systems
having different frequency bands, it must be possible to operate at four different
bands. An example thereof is the GSM application, which in USA and in Europe covers
four bands: GSM800 (824MHz-894MHz) in America, GSM900 (880-960MHz) in Europe, GSM1800
(1710- 1880MHz) in Europe and GSM1900 (1850-1990MHz) in America. Consequently, there
is a general need four communication terminals, and antennas therefor, capable of
quad-band operation.
Summary of the invention
[0013] Hence, it is an object of the present invention to overcome the deficiencies related
to the prior art. More specifically, it is an object to provide an antenna for radio
communication which is capable of operating in different dual-band radio communication
systems, where the dual-band frequencies are different in such different communication
systems.
[0014] According to a first aspect, this object is fulfilled by a tuneable radio antenna
device for a radio communication terminal, said antenna device comprising a ground
substrate, an antenna element, and a ground pole connecting the antenna element to
the ground substrate, wherein an impedance switch device is operable to change the
impedance of a connection between the antenna element and the ground substrate for
tuning the antenna element to different resonance frequencies.
[0015] In one embodiment the impedance switch device comprises a MEMS switch.
[0016] Preferably said antenna element comprises a first elongated member, and a second
elongated member which is shorter than said first member, wherein said impedance switch
is operable to switch between a first impedance setting , in which said members are
resonant for a first lower and a first higher frequency band, respectively, and a
second impedance setting, in which said members are resonant for a second lower and
a second higher frequency band, respectively, different from said first lower and
a first higher frequency band.
In one embodiment said impedance switch device comprises a first switch operable to
change the impedance of a first connection between the first member and the ground
substrate, and a second switch operable to change the impedance of a second connection
between the second member and the ground substrate. Said first switch is preferably
devised to optionally set, for said first connection, a first impedance in said first
impedance setting or a second impedance in said second impedance setting, and said
second switch is correspondingly devised to optionally set, for said second connection,
a third impedance in said first impedance setting or a fourth impedance in said second
impedance setting .
[0017] In one embodiment said antenna element is a branched antenna, wherein said first
member is a first branch of the antenna element, and said second member is a second
branch of said antenna element, each branch having a first and a second end, wherein
said branches are connected to said ground pole at their first ends. Said first switch
is preferably devised to connect the second end of said first branch to ground, through
said first or second impedance, and said second switch is preferably devised to connect
the second end of said second branch to ground, through said third or fourth impedance.
Preferably, said impedance switch device comprises a single pole double throw micro
electromechanical systems switch. Said antenna device is, in a specific embodiment,
a low-profile planar inverted-F antenna.
[0018] In another embodiment from the branched antenna type, said first member of the antenna
element is a main radiating element, the first connection forming said ground pole,
and said second member is a parasitic element to said antenna element, connectable
to ground at one of its ends by said second connection. Said first switch is preferably
devised to connect said ground pole to ground, through said first or second impedance,
and said second switch is preferably devised to connect said second connection said
parasitic element to ground, through said third or fourth impedance. Preferably, said
impedance switch device comprises a double pole double throw micro electromechanical
systems switch. In a specific embodiment, said antenna device is a low-profile planar
parasitic inverted-F antenna.
[0019] According to a second aspect, the object of the invention is fulfilled by a communication
terminal devised for multi-band radio communication, comprising a housing, a user
input and output interface, wherein that communication terminal comprises an antenna
device according to the aforementioned first aspect of the invention, and optionally
any of the further features of the mentioned embodiments.
[0020] According to a third aspect, the object of the invention is fulfilled by a tuneable
quad-band radio antenna device for a radio communication terminal, said antenna device
comprising a ground substrate, a dual-band antenna element comprising a first elongated
antenna member, a second elongated antenna member, which is shorter than said first
member, a ground connection connecting said members to ground, and an impedance switch
device operable to change the impedance of said connection for tuning the antenna
element, such that in a first impedance setting the antenna element is resonant to
a first and a second radio frequency, and in a second impedance setting the antenna
element is resonant to a third and a fourth radio frequency which are frequency shifted
from said first and second radio frequencies.
[0021] According to a fourth aspect, the object of the invention is fulfilled by a communication
terminal devised for quad-band radio communication, comprising a housing, a user input
and output interface, wherein that communication terminal comprises an antenna device
according to the aforementioned third aspect.
Brief description of the drawings
[0022] The features and advantages of the present invention will be more apparent from the
following description of the preferred embodiments with reference to the accompanying
drawings, on which
Fig. 1 schematically illustrates a tuneable multi-band radio antenna device according
to a first embodiment of the invention;
Fig. 2 schematically illustrates the feeding and the ground connections of one branch
of the embodiment according to Fig. 1;
Fig. 3 schematically illustrates the impedance switch arrangement at the ground connections
of the different branches according to the embodiment of Fig. 1;
Fig. 4 schematically illustrates a tuneable multi-band radio antenna device according
to a second embodiment of the invention;
Fig. 5 schematically illustrates the feeding and the ground connection of the main
radiating element of the embodiment according to Fig. 2;
Fig. 6 schematically illustrates the impedance switch arrangement at the ground connections
of the main radiating element and the parasitic according to the embodiment of Fig.
4;
Fig. 7 schematically illustrates an exemplary communication terminal implementing
an antenna design according to an embodiment of the invention;
Fig. 8 illustrates a simulation result of the return loss for a specific embodiment
in accordance with Fig. 1; and
Fig. 9 illustrates a simulation result of the return loss for a specific embodiment
in accordance with Fig. 4.
Detailed description of preferred embodiments
[0023] The present description refers to radio terminals as a device in which to implement
a radio antenna design according to the present invention. The term radio terminal
includes all mobile equipment devised for radio communication with a radio station,
which radio station also may be mobile terminal or e.g. a stationary base station.
Consequently, the term radio terminal includes mobile telephones, pagers, communicators,
electronic organisers, smartphones, PDA:s (Personal Digital Assistants), vehicule-mounted
radio communication devices, or the like, as well as portable laptop computers devised
for wireless communication in e.g. a WLAN (Wireless Local Area Network). Furthermore,
since the antenna as such is suitable for but not restricted to mobile use, the term
radio terminal should also be understood as to include any stationary device arranged
for radio communication, such as e.g. desktop computers, printers, fax machines and
so on, devised to operate with radio communication with each other or some other radio
station. Hence, although the structure and characteristics of the antenna design according
to the invention is mainly described herein, by way of example, in the implementation
in a mobile phone, this is not to be interpreted as excluding the implementation of
the inventive antenna design in other types of radio terminals, such as those listed
above. Furthermore, it should be emphasised that the term comprising or comprises,
when used in this description and in the appended claims to indicate included features,
elements or steps, is in no way to be interpreted as excluding the presence of other
features elements or steps than those expressly stated.
[0024] The present invention is described herein with reference mainly to two exemplary
embodiments, both relating to cellular mobile phones. Both examples relates to planar
inverted F antennas for built-in use. However, from the instant description a person
skilled in the art will realise that, although not shown, the invention as claimed
is equally applicable to other types of antennas for radio communication purposes,
such as e.g. stub antennas or micro-strips.
[0025] Figure 1 discloses schematically a first embodiment of the invention. With the evolution
of micro-electronics and memory storage capability, the communication terminal providers
do their best to meet the general requirements of the terminal usage for having smaller
and smaller terminals. In order to obtain a compact size terminal, miniature multi-band
antennas are strongly recommended. The embodiment of figure 1 discloses a PIFA devised
according to the invention. This kind of antenna has a feeding pin 5 and a ground
pole 6, contacting the antenna to the ground plane to of the printed circuit board
PCB 2. The specific embodiment of figure 1 is a dual-band branched antenna, having
a first elongated member 3 resonant to a first radio frequency, and a second elongated
member 4, which is shorter than the first member 3. The second member 4 is resonant
to a second radio frequency, higher than the first radio frequency. Without reference
to the specific size and form of the antenna, this is a well-known design for a dual-band
radio antenna. If the desire is to use the antenna device 1 for four-band application,
this kind of antenna cannot be directly used. Four-band application is desirable to
make the radio terminal adapted to different dual-band systems having different pairs
of resonant frequencies. One example of were a four-band coverage wound be desirable,
is for a terminal capable of dual band application in the GSM systems of both Europe
and the USA. This is the example for which the embodiment of figure 1, as well as
the embodiment of figure 4 disclosed further down, will be described, although a person
skilled in the art would realise that the invention as disclosed will have a technical
effect also in other cases were a four-band application is desirable.
[0026] The geometry of the antenna device 1 disclosed in figure 1 is a branch PIFA antenna.
The long branch 3 operates at GSM 900, whereas the short branch 4 operates at GSM
1800, which means that the antenna is tuned to Europe mode. Ground pole 6 connects
the first member 3 to ground at a first end 7, from which member 3 extends in an elongated
shape to a second end 9. Similarly, member 4 extends from a first end 8 at the ground
connection of the ground pole 6 to a second end 10. At the second end 9 of member
3 a connection 11 is arranged between the member 3 and ground 2 through a reactance
loading 21. Member 4 has a separate connection 12 connecting the second end 10 of
the member to ground 2 through another reactance loading 22. Each reactance loading
21, 22 has an adaptive impedance which contributes to the resonance frequency of the
respective branch. In accordance with the invention, each reactance loading comprises
an impedance switch 21,22 capable of shifting the impedance through the connections
11,12. The impedance switches 21,22 are in one embodiment operated separately, but
are in a preferred embodiment operated as one impedance switch device 20, indicated
in the drawing by the dashed line.
[0027] Figure 2 illustrates the principle for the frequency tuning by impedance shifting
for the first branch member 3. The reactance loading of the impedance switch 21 is
optionally set to a first impedance value Z1 or a second impedance value Z2. When
the switch 21 is set to Z1 the resonance frequency for antenna member 3 is adapted
to a resonance of 900 MHz to cover Europe mode. When the switch 21 is shifted such
that connection 11 connects antenna member 3 to ground 2 through the second impedance
Z2, the resonance frequency is decreased such that it covers 800 MHz for the American
mode.
[0028] Figure 3 corresponds to figure 2, but illustrates the impedance switches 21,22 for
both branches 3,4. Similar to the first impedance switch 21, also described in figure
2, figure 3 illustrates that the impedance switch 22 for branch 4 comprises a third
impedance Z3 and a forth impedance Z4, through either of which connection 12 may connect
antenna member 4 to ground 2. Antenna member 4 is preferably, as mentioned earlier,
the branch adapted for the higher frequency in a dual-band system. When switch 22
connects ground 2 to Z3, the resonance frequency of antenna member 4 will be set to
1800 MHz to cover Europe mode. By switching connection 12 such that antenna member
4 connects to ground 2 through impedance Z4, the resonance frequency of branch 4 is
switched to 1900 MHz to cover the American mode. In a preferred realisation of this
embodiment, a SPDT (single pole double throw) MEMS (micro electro-mechanical systems)
switch is used in the impedance switches 21,22. The use of a MEMS switch for this
purpose is advantageous since it has low insertion loss and low power consumption.
Furthermore, since the MEMS switch is mechanical it does not consume any power when
it is not used, since no current passes through it, which makes it ideal for mobile
phone application. SPDT switches are otherwise known in the art for the purpose of
switching between receive or transmit, as disclosed for instance by Schultz et al.
in US 4,803,447. In one embodiment, the switch is not only controlled by the MEMS,
but rather comprised therein. By applying different levels of voltage to the MEMS,
different impedances are thereby obtained through the switch.
[0029] A computer simulation has been made on an antenna principle according to the antenna
device 1 of figure 1. Figure 8 shows a diagram of the return loss, as obtained through
the simulation measurements. When the impedance switch device 20 is in its first setting,
such that switch 21 provides an impedance Z1 for connection 11 and switch 22 provides
an impedance Z3 for connection 12, the antenna device 1 is adapted to Europe mode.
The simulation result relating to that setting is indicated by numeral 81 and figure
8. When the impedance switch device 20 is shifted, such that switch 21 provides impedance
Z2 for connection 11 and switch 22 provides impedance Z4 for connection 12, the antenna
device 1 is adapted to American mode. The simulation results for American mode are
indicated by numeral 80 in figure 8. As is evident from the drawing, the dual-band
coverage is suitable shifted by the impedance switch device 20, wherein a quad-band
antenna device 1 has been obtained. The simulation for which the results are disclosed
in Fig. 8 are performed on the antenna alone. When the antenna is enclosed in a housing
or chassis of a communication terminal, such as a cellular phone of Fig. 7, both curves
80 and 81 will be slightly shifted downwards in frequency. Thereby the resonances
of the antenna elements will be suitably located at 800 and 1900 MHz or 900 and 1800
MHz, respectively, for America or Europe mode.
[0030] Figure 4 illustrates another embodiment of the present invention. In this case, the
antenna device 101 comprises a first elongated antenna member 30, connected to ground
20 through a ground pole 60, and fed through a connection 50. The first antenna member
30 extends in an elongated manner from a first end 70 at the ground connection 60
to a second end 90, and the length of member 30 is selected such that it is resonant
to a first radio frequency. In a manner well-known to a skilled person a second antenna
member 40 is implemented in the form of a parasitic element, connected to ground at
a connection 120 at a first end 80 of the parasitic element. The parasitic 40 extends
from the first end 80 in an elongated manner to a second end 100, and the length of
the parasitic 40 is shorter than the length of the first antenna member 30, such as
the parasitic 40 is resonant to a second and higher radio frequency. This geometry
corresponds to a dual-band parasitic antenna, which as such is known in the prior
art. In this embodiment, the ground connection 60, or ground pole 60, connects the
antenna element 30 to ground 20 through an impedance switch 210. Similarly, the ground
connection 120 of the parasitic 40 is connected to ground 20 through second impedance
switch 220. The switches 210,220 may be operated separately, although in one embodiment
they are commonly operated in an impedance switch device 200, indicated in the drawing
by the dashed line.
[0031] Figure 5 discloses the basic principal of the impedance switch 210 on the first antenna
member 30. The impedance switch 210 is optionally set such that the ground connection
60 connects the antenna member 30 to ground 20 through a first impedance Z10, or such
that the connection 60 connects antenna member 30 to ground 20 through a second impedance
Z20. By changing the impedance of the ground connection 60 the resonance frequency
of the antenna element 30 is affected such that it will be resonant for different
radio frequency dependent of the impedance setting.
[0032] Figure 6 illustrates, in a manner similar to figure 3, the arrangement of the impedance
switch device 200 for the embodiments disclosed in figure 4. In figure 6, both antenna
elements 30 and 40 are showed, and ground connections 60,120 through the respective
impedance switches 210,220 to ground 20. As for the first impedance switch 210, the
second impedance switch 220 is optionally set to a third impedance Z30 for ground
connection 120, or to a forth impedance Z40 for the ground connection 120 between
antenna element 40 and ground 20. By switching the impedance switch 220, the resonance
frequency for the parasitic element 40 will be shifted. In a specific realisation
of this embodiment, a DPDT (double pole double throw) MEMS switch is used to control
both switches 210,220. Also the DPTD has low insertion loss and low power consumption,
and is therefore advantageous to use for this purpose. Furthermore, since the MEMS
switch is mechanical it does not consume any power when it is not used, as recited
above. Also in this case, the switch may be comprised in the MEMS.
[0033] Figure 9 illustrates simulation results corresponding to those for figure 8, but
now for an embodiment as disclosed in figures 4-6. It should be noted that the grading
of the horizontal axis is the same as for Fig. 8, i.e. from 0.5 to 2.5 GHz in steps
of 0.1 GHz. In Europe mode the GSM system operates at 900 and 1800 MHz, and reference
numeral 91 indicates the return loss when the antenna device 101 is tuned to Europe
mode by having the impedance switch device 200 set to impedance Z10 and Z30, respectively.
When switching the impedance switch device 200 to impedances Z20 and Z40, respectively,
the antenna device 101 is tuned to the American mode, wherein the lower frequency
is shifted downwards and the higher frequency is shifted upwards to yield the return
loss as disclosed by the curve indicated through numeral 90. When the antenna is enclosed
in a housing or chassis of a communication terminal, such as a cellular phone of Fig.
7, both curves 90 and 91 will be slightly shifted downwards in frequency. Thereby
the resonances of the antenna elements will be suitably located at 800 and 1900 MHz
or 900 and 1800 MHz, respectively, for America or Europe mode.
[0034] Consequently, the present invention provides a solution for adapting a dual-band
radio antenna into a quad-band radio antenna, by using an impedance switch on the
ground connection of the antenna to tune the resonance frequencies. As a person skilled
in the art will realise, the antenna may have more than two branches. Furthermore,
each impedance switch may have more than two selectable settings, e.g. three or four
different impedances, for tuning to different frequencies. The embodiments disclosed
are selected primarily to provide a simplified yet enabling disclosure of the elected
ways of implementing the invention. A suitable field of application is, as previously
mentioned, for portable mobile phones in cellular radio communication systems, such
as GSM, D-AMPS, UMTS, CDMA2000 etc.
[0035] Fig. 7 illustrates a communication radio terminal in the embodiment of a cellular
mobile phone 300 devised for multi-band radio communication. The terminal 300 comprises
a chassis or housing 350, carrying a user audio input in the form of a microphone
310 and a user audio output in the form of a loudspeaker 320 or a connector to an
ear piece (not shown). A set of keys, buttons or the like constitutes a data input
interface 330 usable e.g. for dialling, according to the established art. A data output
interface comprising a display 340 is further included, devised to display communication
information, address list etc in a manner well known to the skilled person. The radio
communication terminal 300 includes radio transmission and reception electronics (not
shown), and is devised with an antenna, such as a built-in antenna device 1 inside
the housing 350, which antenna device is indicated in the drawing by the dashed line
as an essentially flat object. According to the invention, this antenna device 1,
e.g. corresponding to Fig. 1 or Fig. 4, includes a flat ground substrate 2 or 20,
an antenna element 3,4 or 30,40 with a radio signal feeding point 5 or 50, a ground
pole 6 or 60, and an impedance switch 20 or 200, connecting the antenna element to
ground through a selectable impedance in order to tune the antenna to different bands.
The other features of the antenna design according to the present invention described
above are naturally equally valid for the radio terminal implemented embodiment of
Fig. 7.
[0036] The foregoing has described the principles, preferred embodiments and modes of operation
of the present invention. However, the invention should not be construed as being
limited to the particular embodiments discussed above. For example, while the antenna
of the present invention has been discussed primarily as being a radiator, one skilled
in the art will appreciate that the antenna of the present invention would also be
used as a sensor for receiving information at specific frequencies. Similarly, the
dimensions of the various elements may vary based on the specific application. Furthermore,
the impedances of the invention may be capacitive, resistive and/or inductive, highly
dependent on the specific design of the antenna elements and the desired resonances.
Thus, the above-described embodiments should be regarded as illustrative rather than
restrictive, and it should be appreciated that variations may be made in those embodiments
by those skilled in the art without departing from the scope of the present invention
as defined by the following claims.
1. A tuneable quad-band radio antenna device (1) for a radio communication terminal,
said antenna device comprising a ground substrate (2), a dual-band antenna element
comprising a first elongated antenna member (3) and a second (4) elongated antenna
member, which is shorter than said first member, a radio signal feeding point (5,50),
and a micro electro-mechanical systems (MEMS) switch device (20) comprising a first
impedance switch operable to change the impedance of a first connection (11) between
said first antenna member and said ground substrate, characterised in that said MEMS switch device further comprises a second impedance switch operable to change
the impedance of a second connection (12) between said second antenna member and said
ground substrate, wherein said MEMS switch device's first and second impedance switches
are respectively devised to switch between a first impedance setting (Z1,Z3), in which
the antenna element is resonant to a first and a second radio frequency of a first
dual-band radio system, and a second impedance setting (Z2,Z4), in which the antenna
element is resonant to a third and a fourth radio frequency of a second dual-band
radio system.
2. The quad-band radio antenna device as recited in claim 1, characterised in that means are provided for obtaining said first and second impedance settings by applying
different levels of voltage to said MEMS switch device.
3. The tuneable radio antenna device as recited in claim 1 or 2, characterised in that said first impedance switch is devised to optionally connect said first connection
through a first (Z1) impedance in said first impedance setting or a second (Z2) impedance
in said second impedance setting, and in that said second impedance switch is devised to optionally connect said second connection
through a third (Z3) impedance in said first impedance setting or a fourth (Z4) impedance
in said second impedance setting.
4. The tuneable radio antenna device as recited in any of the preceding claims, characterised in that said first member is a first branch (3) of the antenna element, and said second member
is a second branch (4) of said antenna element, each branch having a first (7,8) and
a second (9,10) end, wherein said branches are connected to said ground substrate
through a ground pole (6) at their first ends.
5. The tuneable radio antenna device as recited in claim 4, characterised in that said first impedance switch (21) is devised to connect the second end (9) of said
first branch to ground, through said first (Z1) or second (Z2) impedance, and said
second impedance switch (22) is devised to connect the second end (10) of said second
branch to ground, through said third (Z3) or fourth (Z4) impedance.
6. The tuneable radio antenna device as recited in claim 4 or 5, characterised in that said MEMS switch device comprises a single pole double throw MEMS switch.
7. The tuneable radio antenna device as recited in any of the previous claims, characterised in that said antenna device is a low-profile planar inverted-F antenna.
8. The tuneable radio antenna device as recited in any of claims 1-3, characterised in that said first member is a main radiating element (30) of the antenna element, the first
connection (60) forming a ground pole, and wherein said second member is a parasitic
element (40) to said antenna element, connectable to ground at one (80) of its ends
by said second connection (90)
9. The tuneable radio antenna device as recited in claim 8, characterised in that said first impedance switch (210) is devised to connect said ground pole (60) to
ground, through said first (Z10) or second (Z20) impedance, and said second impedance
switch (220) is devised to connect said second connection (90) said parasitic element
to ground, through said third (Z30) or fourth (Z40) impedance.
10. The tuneable radio antenna device as recited in claim 8 or 9, characterised in that said MEMS switch device comprises a double pole double throw MEMS switch.
11. The tuneable radio antenna device as recited in any of the claims 8-10, characterised in that said antenna device is a low-profile planar parasitic inverted-F antenna.
12. A communication terminal (300) devised for quad-band radio communication, comprising
a housing (350), a user input (310,330) and output (320,340) interface, characterised in that communication terminal comprises an antenna device (1) according to any of the previous
claims.
1. Abstimmbare Quad-Band-Funkantennen-Einrichtung für ein Funkkommunikationsendgerät,
wobei die Antenneneinrichtung ein Massesubstrat (2) aufweist, wobei ein Dualband-Antennenelement
ein erstes langgestrecktes Antennenteil (3) und ein zweites langgestrecktes Antennenteil
(4) aufweist, welches kürzer ist als das erste Teil, einen Funksignal-Speisepunkt
(5, 50), und eine mikro-elektro-mechanische Systemschalteinrichtung (20) (MEMS), die
einen ersten Impedanzschalter aufweist, der betätigbar ist, um die Impedanz einer
ersten Verbindung (11) zwischen dem ersten Antennenteil und dem Massesubstrat zu ändern,
dadurch gekennzeichnet, dass die MEMS-Schalteinrichtung außerdem einen zweiten Impedanzschalter aufweist, der
betätigbar ist, die Impedanz einer zweiten Verbindung (12) zwischen dem zweiten Antennenteil
und dem Massesubstrat zu ändern, wobei die MEMS-Schalteinrichtung, die einen ersten
und zweiten Impedanzschalter hat, entsprechend entworfen ist, um zwischen einer ersten
Impedanzeinstellung (Z1, Z3), bei der das Antennenelement in Resonanz ist zu einer
ersten und einer zweiten Funkfrequenz eines ersten Dualband-Funksystems ist, und einer
zweiten Impedanzeinstellung (Z2, Z4), bei der das Antennenelement in Resonanz mit
einer dritten und einer vierten Funkfrequenz eines zweiten Dualband-Funksystems ist,
zu schalten.
2. Quad-Band-Funk-Antenneneinrichtung nach Anspruch 1, dadurch gekennzeichnet, dass die Einrichtung vorgesehen ist, um die erste und die zweite Impedanzeinstellung durch
Anlegen unterschiedlicher Spannungspegel an die MEMS-Schalteinrichtung zu erhalten.
3. Abstimmbare Funkantenneneinrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass der erste Impedanzschalter dazu entworfen ist, um optional die erste Verbindung über
eine erste Impedanz (Z1) beim ersten Impedanzeinstellen oder eine zweite Impedanz
(Z2) beim zweiten Impedanzeinstellen zu verbinden, und dass der zweite Impedanzschalter
dazu entworfen ist, um optional die zweite Verbindung über eine dritte Impedanz (Z3)
beim ersten Impedanzeinstellen oder eine vierte Impedanz (Z4) beim zweiten Impedanzeinstellen
zu verbinden.
4. Abstimmbare Funkantenneneinrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das erste Teil ein erster Zweig (3) des Antennenelements ist, und das zweite Teil
ein zweiter Zweig (4) des Antennenelements ist, wobei jeder Zweig ein erstes (7, 8)
und ein zweites (9, 10) Ende aufweist, wobei die Zweige mit dem Massesubstrat über
einen Erdungspol (6) an ihren ersten Enden verbunden sind.
5. Abstimmbare Funkantenneneinrichtung nach Anspruch 4, dadurch gekennzeichnet, dass der erste Impedanzschalter (21) dazu entworfen ist, das zweite Ende (9) des ersten
Zweigs über die erste (Z1) oder die zweite (Z2) Impedanz mit Masse zu verbinden, und
der zweite Impedanzschalter (22) dazu ausgedacht ist, das zweite Ende (10) des zweiten
Zweigs über die dritte (Z3) oder die vierte (Z4) Impedanz mit Masse zu verbinden.
6. Abstimmbare Funkantenneneinrichtung nach Anspruch 4 oder 5, dadurch gekennzeichnet, dass die MEMS-Schalteinrichtung einen Einzelpol-Doppel-MEMS-Umschalter aufweist.
7. Abstimmbare Funkantenneneinrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Antenneneinrichtung eine Planar-Niedrig-Profil-Invertiert-F-Antenne ist.
8. Abstimmbare Funkantenneneinrichtung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass das erste Teil ein Hauptabstrahlelement (30) des Antennenelements ist, wobei die
erste Verbindung (60) einen Erdungspol bildet und wobei das zweite Teil ein parasitäres
Element (40) zum Antennenelement ist, welches mit Masse an einem (80) seiner Enden
durch die zweite Verbindung (90) verbindbar ist.
9. Abstimmbare Funkantenneneinrichtung nach Anspruch 8, dadurch gekennzeichnet, dass der erste Impedanzschalter (210) dazu entworfen ist, den Erdungspol (60) über die
erste (Z 10) oder die zweite (Z20) Impedanz mit Masse zu verbinden, und der zweiten
Impedanzschalter (220) dazu entworfen ist, die zweite Verbindung (90) des parasitären
Elements über die dritte (Z30) oder die vierte (Z40) Impedanz mit Masse zu verbinden.
10. Abstimmbare Funkantenneneinrichtung nach Anspruch 8 oder 9, dadurch gekennzeichnet, dass die MEMS-Schalteinrichtung einen Doppelpol-Doppel-MEMS-Umschalter aufweist.
11. Abstimmbare Funkantenneneinrichtung nach einem der Ansprüche 8 bis 10, dadurch gekennzeichnet, dass die Antenneneinrichtung eine parasitäre Planar-Niedrig-Profil-Invertiert-F-Antenne
ist.
12. Kommunikationsendgerät (30), welches für Quad-Band-Funkkommunikation entworfen ist,
welches ein Gehäuse (350), eine Benutzereingabe- (310, 330) und eine Benutzerausgabe-Schnittstelle
(320, 340) aufweist, dadurch gekennzeichnet, dass das Kommunikationsendgerät eine Antenneneinrichtung (1) nach einem der vorhergehenden
Ansprüche aufweist.
1. Dispositif (1) d'antenne radio quadri-bande accordable destiné à un terminal de radiocommunications,
ledit dispositif d'antenne comprenant un substrat (2) de masse, un élément d'antenne
bi-bande comprenant un premier élément (3) d'antenne allongé ainsi qu'un deuxième
(4) élément d'antenne allongé qui est plus court que ledit premier élément, un point
(5, 50) d'alimentation en signal radio, et un dispositif (20) de commutation à microsystème
électromécanique (MEMS pour Micro Electro-Mechanical System) comprenant un premier
commutateur d'impédance pouvant être utilisé pour faire varier l'impédance d'une première
liaison (11) entre ledit premier élément d'antenne et ledit substrat de masse, caractérisé en ce que ledit dispositif de commutateur MEMS comprend de plus un deuxième commutateur d'impédance
pouvant être utilisé pour faire varier l'impédance d'une deuxième liaison (12) entre
ledit deuxième élément d'antenne et ledit substrat de masse, où ledit dispositif de
commutateur MEMS des premier et deuxième commutateurs d'impédance sont respectivement
conçus pour commuter entre un premier réglage (Z1, Z3) d'impédance dans lequel l'élément
d'antenne est en résonance à une première ainsi qu'à une deuxième fréquence radio
d'un premier système radio bi-bande, et un deuxième réglage (Z2, Z4) d'impédance dans
lequel l'élément d'antenne est en résonance à une troisième ainsi qu'à une quatrième
fréquence radio d'un deuxième système radio bi-bande.
2. Dispositif d'antenne radio quadri-bande selon la revendication 1, caractérisé en ce qu'un moyen est fourni pour obtenir lesdits premier et deuxième réglages d'impédance
en appliquant différents niveaux de tension audit dispositif de commutation MEMS.
3. Dispositif d'antenne radio accordable selon la revendication 1 ou 2, caractérisé en ce que ledit premier commutateur d'impédance est conçu pour relier de façon optionnelle
ladite première liaison à travers une première impédance (Z1) dans ledit premier réglage
d'impédance ou une deuxième impédance (Z2) dans ledit deuxième réglage d'impédance,
et en ce que ledit deuxième commutateur d'impédance est conçu pour relier de façon optionnelle
ladite deuxième liaison à travers une troisième impédance (Z3) dans ledit premier
réglage d'impédance ou une quatrième impédance (Z4) dans ledit deuxième réglage d'impédance.
4. Dispositif d'antenne radio accordable selon l'une quelconque des précédentes revendications,
caractérisé en ce que ledit premier élément est une première branche (3) de l'élément d'antenne, et ledit
deuxième élément est une deuxième branche (4) dudit élément d'antenne, chaque branche
ayant une première (7, 8) et une deuxième (9, 10) extrémité, où lesdites branches
sont reliées audit substrat de masse à travers un pôle (6) de masse à leurs premières
extrémités.
5. Dispositif d'antenne radio accordable selon la revendication 4, caractérisé en ce que ledit premier commutateur (21) d'impédance est conçu pour relier la deuxième extrémité
(9) de ladite première branche à la masse à travers lesdites première (Z1) et deuxième
(Z2) impédances, et en ce que ledit deuxième commutateur (22) d'impédance est conçu pour relier la deuxième extrémité
(10) de ladite deuxième branche à la masse, à travers lesdites troisième (Z3) et quatrième
(Z4) impédances.
6. Dispositif d'antenne radio accordable selon les revendications 4 ou 5, caractérisé en ce que ledit dispositif de commutateur MEMS comprend un commutateur MEMS à un circuit à
double position.
7. Dispositif d'antenne radio accordable selon l'une quelconque des précédentes revendications,
caractérisé en ce que ledit dispositif d'antenne est une antenne en F inversé planar à profil bas.
8. Dispositif d'antenne radio accordable selon l'une quelconque des revendications 1
à 3, caractérisé en ce que ledit premier élément est un élément (30) radiant principal de l'élément d'antenne,
la première liaison (60) formant un pôle de masse, et dans lequel ledit deuxième élément
est un élément (40) parasite dudit élément d'antenne, pouvant être relié à la masse
à l'une (80) de ses extrémités par ladite deuxième liaison (90).
9. Dispositif d'antenne radio accordable selon la revendication 8, caractérisé en ce que ledit premier commutateur (210) d'impédance est conçu pour relier ledit pôle (60)
de masse à la masse à travers ladite première (Z10) ou deuxième (Z20) impédance, et
en ce que ledit deuxième commutateur (220) d'impédance est conçu pour relier ladite deuxième
liaison (90) dudit élément parasite à la masse au travers de ladite troisième (Z30)
ou quatrième (Z40) impédance.
10. Dispositif d'antenne radio accordable selon les revendications 8 ou 9, caractérisé en ce que ledit dispositif de commutateur MEMS comprend un commutateur MEMS bipolaire à deux
directions.
11. Dispositif d'antenne radio accordable selon l'une quelconque des revendications 8
à 10, caractérisé en ce que ledit dispositif d'antenne est une antenne en F inversée parasite planar à profil
bas.
12. Terminal (300) de communications conçu pour des communications radio quadri-bandes,
comprenant un boîtier (350), une entrée (310, 330) pour un utilisateur ainsi qu'une
interface de sortie (320, 340), caractérisé en ce que le terminal de communications comprend un dispositif (1) d'antenne selon l'une quelconque
des précédentes revendications.