Technical Field
[0001] The invention relates to an antenna for use in a portable electronic communication
apparatus such as a mobile telephone. More specifically, the invention relates to
a built-in antenna comprising a pattern of conductive material, which is printed on
the printed circuit board (PCB) of the portable electronic communication apparatus.
The invention also relates to a portable electronic communication apparatus comprising
such a printed built-in antenna.
Prior Art
[0002] A portable electronic communication apparatus, such as a mobile telephone,requires
some sort of antenna in order to establish and maintain a wireless radio link with
another unit in the communication system, normally a base station. In the telecommunication
industry, the demand for mobile telephones that are small in size, light in weight,
and inexpensive to manufacture are continuously present. To this end, printed built-in
antennas are utilized for mobile telephones within the 300-3000 MHz frequency range.
Printed built-in antennas known in the art comprises microstrip patch antennas and
planar inverted-F antennas (PIFA).
[0003] As the mobile telephones becomes smaller and smaller, both conventional microstrip
patch and PIFA antennas are still too large to fit small mobile telephone chassis.
This is particularly problematic when the new generation of mobile telephones needs
multiple antennas for cellular, wireless local are network, GPS and diversity.
[0004] The antenna pattern of the antennas according to the above are printed on a support
member separated from the main printed circuit board (PCB) of the mobile telephone.
After manufacturing, the antenna can be connected to the PCB by utilizing connectors,
such as pogo-pins.
[0005] Disadvantages of built-in antennas known in the art are that both the connectors
and the assembling of the antenna and the PCB add considerable cost to the mobile
telephone. Also, the mechanical tolerances involved in the assembling of the conventional
built-in antenna and the PCB effect the performance of the antenna negatively. That
is, it is difficult to obtain exactly the same position of the antenna in relation
to the signal source, and sufficient connection of the pogo-pins. Also, in antenna
configurations known in the art, the space between the antenna and the PCB is not
utilized effectively, by e.g. positioning electronic components in between them.
[0006] Further, as it becomes more and more common with multi-port antennas in portable
electronic communication apparatuses, i.e. antennas having separate antenna arms for
each Rx (receiver unit) and Tx (transmitter unit), the number of connectors is increasing
and consequently the cost and the problem with mechanical tolerances.
Summary of the Invention
[0007] It is an object of the present invention to provide a built-in antenna having a printed
pattern of conductive material with good radiation characteristics in at least one
frequency band, which is inexpensive to manufacture and utilizes the interior space
of an electronic communication apparatus effectively. More specifically, it is an
object of the invention to provide an antenna, which can be connected to the RF circuits
of the printed circuit board (PCB) of the apparatus without any conventional connectors,
such as pogo-pins. A further object of the invention is to eliminate the mechanical
tolerances involved with the assembly of the antenna and the PCB.
[0008] Another object of the invention is to provide a portable electronic apparatus comprising
a PCB and a built-in antenna, which can be connected to said PCB without any connectors.
[0009] The above objects are achieved by providing an antenna adapted to be built-in and
used in a portable electronic communication apparatus. The antenna comprises a pattern
of a conductive material printed directly on the PCB of the portable electronic communication
apparatus, which comprises the RF circuits of the apparatus. Further, the above objects
are achieved by providing an extended ground plane connected to the main ground plane
of the PCB and situated parallel to and opposite the antenna pattern. The antenna
pattern and the extended ground plane are positioned with a distance in relation to
each other, and form a space, in which low profile electronic components can be positioned.
[0010] The above objects are also achieved by a portable electronic communication apparatus
comprising a PCB having RF circuits connected to an built-in antenna, which is printed
on the PCB of the apparatus and connected to the RF circuits. Also, the apparatus
of the invention comprises an extended ground plane, which provides good radiation
characteristics for the antenna.
[0011] By providing the inventive antenna manufacturing costs of the portable electronic
communication apparatus is lowered and the interior space of the apparatus is utilized
more effectively.
[0012] As an alternative, the antenna pattern can be provided to form a multi-port antenna
comprising antenna arms having four connections to the circuitry of the PCB. In this
embodiment the cost savings in relation the known art will be even bigger. Also, as
no connectors, such as pogo-pins are needed, the insertion loss is lowered. Further,
by providing separate antenna patterns for the Rx and Tx circuits respectively, it
is possible to connect the antenna to the Rx and Tx circuitry respectively, without
having an antenna switch, which will lower the cost of the mobile phone even more.
[0013] Further preferred features of the invention are defined in the dependent claims.
[0014] It should be emphasized that the term "comprises/comprising" when used in this specification
is taken to specify the presence of stated features, integers, steps, components or
groups thereof.
Brief Description of the Drawings
[0015] Preferred embodiments of the present invention will now be described in more detail
with reference to the accompanying drawings, in which:
Fig. 1 shows a mobile telephone having a built-in antenna according to the invention;
Fig. 2 illustrates a PIFA antenna printed on the main PCB of the mobile phone in Fig.
1;
Fig. 3 illustrates a multi-port antenna printed on the main PCB of the mobile phone
in Fig. 1; and
Fig. 4 is a SWR diagram and a Smith chart representing the performance of the embodiment
shown in Fig. 2.
Detailed Disclosure
[0016] Fig. 1 illustrates a mobile telephone 1 as one example in which the printed built-in
antenna according to the invention may be used. However, the inventive antenna may
be used in virtually any other portable electronic communication apparatus, in which
a built-in antenna is preferred.
[0017] The mobile telephone 1 shown in Fig. 1 comprises a loudspeaker 2, a keypad 3, a microphone
4, and a display 5 as is generally known in the art. Further, the mobile telephone
1 comprises the antenna according to the invention, which is built-in into the chassis
of the mobile telephone 1.
[0018] Fig. 2 illustrates a multi-band printed built-in antenna according to a first embodiment
of the invention. The antenna comprises a pattern of conductive material printed directly
on the main printed circuit board (PCB) 7 of the mobile telephone 1. In Fig. 2, the
PCB 7 is shown as ending at the beginning of the antenna pattern. However, as is apparent
to the man skilled in the art, this is only for illustrative purposes. In a real application
the PCB 7 extends over the full extension of the entire antenna pattern, as the antenna
pattern is printed on the PCB 7.
[0019] In the embodiment of Fig. 2 the antenna pattern comprises at a first plane a dual-band
PIFA (Planar Inverted-F Antenna) antenna having a first arm 8 and a second arm 9,
which are resonant in a first and second frequency band, respectively. Also, to provide
a third frequency band, at which the antenna is resonant, the antenna pattern comprises
a parasitic element 10, which is capacitively coupled to the main PIFA. Further, to
provide good radiation characteristics, e.g. directed radiation, and a ground plane
under the antenna pattern an extended ground plane 11 is provided at a second plane,
essentially parallel to the first plane and opposite the antenna pattern.
[0020] The first and second antenna arms 8, 9 of the conductive pattern are printed directly
on a first side of the main PCB 7. The main PCB 7 has a main ground plane, to which
the second antenna arm 9 is connected. The first antenna arm 8 is connected to the
RF port 13 of the main PCB 7. The connection between the antenna pattern and the patches
of the PCB 7 is e.g. provided by connection strips, which provide sufficient connection
between the antenna and the RF circuits of the PCB to not have an effect on the antenna
tuning such as impedance matching and bandwidth. By printing the conductive pattern
of the antenna directly on the main PCB 7, it is possible to connect the antenna arms
8, 9 to a RF port 13 and ground plane of the PCB 7, respectively, without any conventional
connectors, such as pogo-pins. The RF circuitry of the mobile telephone 1 as such
forms no essential part of the present invention and is therefore not described in
detail herein.
[0021] As will be readily realized by the man skilled in the art, the RF circuitry will
comprise various known HF (high frequency) components and base band components suitable
for receiving a frequency signal, filtering the received signal, demodulating the
received signal into a baseband signal, filtering the baseband signal further, converting
the baseband signal to digital form, applying digital signal processing to the digitized
baseband signal (including channel and speech decoding), etc. Conversely, the HF and
baseband components of the radio circuitry will be capable of applying speech and
channel encoding to a signal to be transmitted, modulating it onto a carrier wave
signal, supplying the resulting HF signal to the antenna, etc.
[0022] In the first embodiment shown in Fig. 2, the antenna is designed to have an input
impedance of 50 ohm, without any impedance matching circuit. The first antenna arm
8 is designed to be resonant in a first frequency band at around 900 Mhz (GSM), and
the second antenna arm 9 is designed to be resonant in a second frequency band at
around 1800 Mhz (DCS). However, the design and tuning of the embodiment in Fig. 2
is only exemplifying, and is not considered to limit the scope of the invention. Other
designs of the printed antenna arms are equally well possible within the scope of
the invention.
[0023] As an option, the antenna in Fig. 2 comprises the parasitic element 10, which is
printed on a second side of the main PCB 7. Therefore, in this embodiment the main
PCB is at least a dual-layer PCB. The parasitic element 10 is connected to the ground
plane of the PCB 7, by e.g. a connection strip, and capacitively coupled to the main
PIFA. Since the main PIFA and the parasitic element 10 are positioned on opposite
sides of the PCB 7, the distance between them is the thickness of the PCB.
[0024] For tuning purposes of the bandwidth of the antenna, the parasitic element is positioned
with a longitudinal displacement opposite the antenna pattern of the first side of
the PCB 7 as can be seen in Fig. 2. Also, the length of the parasitic element 10 will
effect the natural frequency of said element 10 and the bandwidth of the antenna.
The parasitic element 10 widens the bandwidth of the second antenna arm 9, which adds
the third frequency band, at which the antenna is resonant. Here, the third frequency
band is at around 1900 MHz (PCS). However, the exact design of the parasitic element
10 forms no essential part of the invention. Fig. 2 is only showing an exemplifying
embodiment and is not considered to limit the scope of the invention.
[0025] By printing the antenna pattern on the main PCB, the antenna is always positioned
in the same position everytime. Therefore, the mechanical tolerances involved with
the connection of an antenna known in the art to the PCB can be substantially eliminated,
which also improves the performance of the antenna. For example, a bad connection
between the circuits of the PCB and the antenna will not occur and the antenna pattern
will always be positioned in exactly the same position in relation to the signal source.
[0026] As is known to the man skilled in the art, it is preferred to provide a ground plane
under the antenna pattern of a PIFA antenna. Therefore, the extended ground plane
11 having a first and second end, respectively, is provided essentially parallel to
the PCB, and positioned opposite the antenna pattern at the second side of the PCB
7. This will also provide good radiation characteristics of the antenna, e.g. by directing
the radiation in a preferred direction. The size of the extended ground plane 11 is
at least as big as the size of the antenna pattern, and the shape of said plane 11
corresponds essentially to the shape of said pattern. A smaller extended ground plane
11 is possible, however it will have a negative effect on the bandwidth of the antenna.
[0027] The distance between the PCB 7 and the extended ground plane 11 is preferably in
the range of 6-10 mm. A smaller distance will decrease the bandwidth of the antenna,
and a larger distance is not necessary and will only effect the dimensions of the
antenna. In this embodiment, the extended ground plane 11 comprises a metal layer
mounted on a carrier, such as a piece of dielectric material. However, other configurations
of conductive material, which can provide a ground plane 11 can be utilized. The material
of the extended ground plane 11 should have good reflection properties of electromagnetic
radiation, such as copper. This will direct the radiation of the antenna in a preferred
direction and the antenna efficiency will increase.
[0028] As can be seen in Fig. 2, the first end of the extended ground plane 11 is connected
to the ground plane of the main PCB 7 through a distance portion 12, which will provide
sufficient distance between the extended ground plane 11 and the PCB 7. Also, the
distance portion 12 will provide connection between the extended ground plane 11 and
the ground plane of the PCB 7. A first end of the distance portion 12 is connected
to the PCB 7, preferably at the connection point of the parasitic element 10 to the
ground plane of the PCB 7, as can be seen in Fig. 2, and is extending substantially
orthogonal from the second side of the PCB 7. However, other angles are also possible
as long as sufficient distance between the PCB 7 and the extended ground plane 11
is obtained. A second end of the distance portion 12 is connected to the first end
of the extended ground plane 11. In the first embodiment, the distance portion 12
is made of a conductive material, such as copper, for connecting the ground plane
of the PCB 7 and the extended ground plane 12. Also, it is possible that the distance
portion 12 forms part of the extended ground plane 11, which then is provided e.g.
as a bent metal layer.
[0029] To further improve the antenna characteristics, a second conductive layer 14, similar
to the first conductive layer of the extended ground plane 11, can as an option be
provided substantially parallel to and opposite said first conductive layer of the
extended ground plane 11 to form a microwave choke. This second layer 14 is also connected
to the second end of the distance portion 12, and consequently to the ground plane
of the main PCB 7. The second conductive layer has preferably the same size and form
as the first conductive layer and form a slot therewith. The distance between the
conductive layers is small, preferably not more than 1 mm. Between the conductive
layers is a dielectric member 15 provided, e.g. in form of the support element described
above.
[0030] Between the extended ground plane 11 and the PCB, it is possible to position electronic
components of the mobile telephone 1 having a low profile in the range of up to approximately
3 mm, such as a buzzer. By positioning suitable electronic components between the
PCB 7 and the extended ground plane 11, the interior space of the mobile telephone
will be better utilized.
[0031] The first embodiment disclosed in Fig. 2 provides a small and efficient antenna,
which is inexpensive to manufacture and provides good radiation characteristics in
several frequency bands. A Smith chart and a SWR (standing wave ratio) diagram in
Fig. 4 illustrate the performance of a prototype of the antenna in Fig. 2.
[0032] As is well known to the man skilled in the art, a SWR diagram illustrates the frequencies
at which an antenna is resonating. The SWR diagram of Fig. 4 represents the return
loss in dB as a function of frequency. The lower dB values in a SWR diagram, the better.
In a SWR diagram, a resonance is an area, within which the return loss is low (a high
negative value in dB). In the SWR diagram of Fig. 4 this looks look like steep and
deep cavities. As is apparent, the antenna according to the invention has good resonating
properties in the GSM band at around 880-960 MHz, the DCS band at around 1710-1880
MHz, and the PCS band at around 1850-1990 MHz.
[0033] Briefly speaking, in the Smith chart of Fig. 4 the circles represent different frequencies,
in which the antenna of Fig. 2 is operating. The horizontal axis represents pure resistance
(no reactance). Of particular importance is the point at 50 Ω (the middle of the horizontal
axis), which normally represents an ideal input impedance. As can be seen in Fig 4,
the first embodiment of the antenna is tuned to have an input impedance of 50 Ω without
any impedance matching circuit.
[0034] As is mentioned previously, the specific design ofthe antenna pattern is not fundamental
to the present invention. The design of the antenna pattern is different in each individual
case to tune the antenna in a preferred frequency band. To illustrate this, a second
alternative embodiment of the inventive antenna is disclosed in Fig. 3. Again, the
PCB 27 is shown as ending at the beginning of the antenna pattern, as in Fig. 2. However,
as is apparent to the man skilled in the art, this is only for illustrative purposes.
In a real application the PCB 27 extends over the full extension of the entire antenna
pattern, as the antenna pattern is printed on the PCB 27.
[0035] The built-in printed multi-port antenna comprises in a similar fashion as the multi-band
antenna in Fig. 2 an antenna pattern printed on the main PCB 27 of the mobile telephone
1. However, the antenna pattern of the multi-port antenna comprises different antenna
arms for different frequency bands and each Rx and Tx.
[0036] The multi-port antenna is a dual-band antenna having four multi-port antenna arms
28, 29, 30, 31, i.e. two for the lower frequency band and two for the higher frequency
band. In this embodiment no parasitic element is provided. However, the man skilled
in the art easily implements this by providing a dual-layer PCB with a parasitic element
printed on the PCB 27 opposite the main antenna pattern. Also, the multi-port antenna
comprises an extended ground plane 25 having one, or two (not shown), conductive layers
similarly to the first embodiment in Fig. 2, connected to the main ground plane of
the PCB 27.
[0037] Each of the multi-port antenna arms 28, 29, 30, 31 are connected to Rx and Tx ports
32, 33, 34, 35, respectively, of the PCB 27 by connection strips, as described above.
[0038] The present invention has been described above with reference to a first embodiment
and an alternative embodiment. However, many alternative embodiments not described
herein are equally possible within the scope of the invention, as defined by the appended
independent claims. Particularly as regards the specific geometrical dimensioning
of the pattern of conductive material, which makes up the antenna, the various dimensions
will have to be carefully selected depending on the actual application. Moreover,
the frequency bands in which the antenna is operative may also be greatly varied depending
on the actual application. Therefore, the antenna pattern has to be tuned for the
actual application, which is believed to be routine actions by the man skilled in
the art and is therefore not further disclosed herein.
[0039] In the drawings, some of the dimensions and the distance between different parts
of the antenna, such as the distance between the PCB 7, 27 and the extended ground
plane 11, 25, are highly exaggerated for illustrative purposes, and are not to be
considered effecting the scope of the invention.
1. A built-in antenna for use in a portable electronic communication apparatus (1),
the antenna comprises a pattern of a conductive material, characterized in that the pattern of conductive material is printed on the Printed Circuit Board (PCB)
(7; 27) of the portable electronic communication apparatus (1).
2. The antenna according to claim 1, wherein the conductive pattern comprises at least
a first antenna arm (8; 28, 30), which is resonant in a first frequency band, and
a second antenna arm (9; 29, 31), which is resonant in a second frequency band, said
arms (8, 9; 28, 29, 30, 31) are printed on a first side of the PCB (7; 27).
3. The antenna according to claim 1 or 2, wherein the PCB (7) is at least a dual-layer
PCB, and the antenna pattern further comprises a parasitic element (10), which is
printed on a second side of the PCB (7) and is positioned opposite the antenna arms
(8, 9) with a longitudinal displacement relative the first antenna arm (8), the parasitic
element (10) is connected to the ground plane of the PCB (7), and capacitively coupled
to the second antenna arm (9), which parasitic element (10) provides a third frequency
band.
3. The antenna according to claim 1 or 2, wherein the conductive pattern comprises at
separate antenna arms (28, 29) for Rx (receiver unit) and Tx (transmitter unit), respectively,
which are resonant in a first frequency band, and separate antenna arms (30, 31) for
Rx and Tx, respectively, which are resonant in a second frequency band.
5. The antenna according to any of the proceeding claims, wherein said antenna further
comprises an extended ground plane (11; 25) comprising a first conductive layer, which
is connected to the ground plane of the PCB (7; 27) via a distance portion (12) having
a first end connected to the ground plane of the PCB (7; 27) and extending substantially
orthogonal therefrom, and a second end connected to the first conductive layer of
the extended ground plane (11; 25), the extended ground plane (11; 25) extends substantially
parallel to the PCB (7; ,27) and opposite the antenna pattern.
6. The antenna according to claim 5, wherein the size of the extended ground (11; 25)
at least corresponds to the size of the antenna pattern, and the shape of the extended
ground plane (11; 25) corresponds to the shape of the antenna pattern.
7. The antenna according to claim 5 or 6, wherein the distance between the PCB (7, 27)
and the extended ground plane (11; 25) is in the range of 6-10 mm.
8. The antenna according to any of the claims 5-7, wherein the extended ground plane
(11) comprises a second conductive layer positioned parallel and opposite to the first
conductive layer and is connected to the second end of the distance portion (12),
the size and the shape of said second layer corresponds to the size and shape of the
first conductive layer.
9. The antenna according to claim 8, wherein a dielectric member (15) having a thickness
of not more than 1 mm is positioned between the first and the second layers of the
extended ground plane (11).
10. The antenna according to any of the claims 5-9, wherein the conductive material of
the conductive layers and the distance portion (12) is metal.
11. The antenna according to any of the claims 5-10, wherein the conductive material
of the conductive layers and the distance portion (12) is copper.
12. The antenna according to any of the preceding claims, further comprising connection
strips for connecting the antenna arms (8, 9; 28, 29, 30, 31) and the parasitic element
(10) to the RF circuit and the ground plane of the PCB (7; 27).
13. The antenna according to any of the preceding claims, wherein the antenna is adapted
to operate in at least one of the following: a first frequency band at around 900
MHz, a second frequency band at around 1800 MHz.
14. , The antenna according to any of the claims 3 or 5-13, wherein the antenna is adapted
to operate in a third frequency band at around 1900 MHz.
15. A portable electronic communication apparatus for use in a wireless telecommunication
system, comprising an antenna according to any of the proceeding claims.
16. A portable electronic communication apparatus according to claim 15, wherein the
apparatus is a mobile telephone (1).