A WIDEBAND MULTIBAND INTERNAL ANTENNA DEVICE AND A PORTABLE RADIO COMMUNICATION DEVICE COMPRISING SUCH AN ANTENNA
DEVICE
FIELD OF INVENTION
The present invention relates generally to an internal planar antenna device in radio communication and more particularly to a wideband multiband internal planar antenna for a radio communication device such as a mobile telephone adapted for use with at least two frequency bands.
BACKGROUND
In recent years, mobile telephones have become increasingly popular. At present time, mobile systems in different places in the world utilize different frequency bands for radio communication. Some widely used systems are AMPS (Advanced Mobile Phone Service) , GSM 900 (Global System for Mobile communications), DCS 1800 (Digital Cellular System) and PCS 1900 (Personal Communications Services) . Several solutions exist where comomations of frequency bands are used in one telephone.
It is often desirable to provide a telephone that: operates in a plurality of systems. It is also desirable to provide an antenna that is as small as possible in order to make it possible to provide a very compact: telephone.
Protruding antennae are frequently used in mobile tele- pnones, however it is difficult to achieve a compact tele¬ phone with a protruding antenna. Such an antenna can also be experienced as annoying if it gets entangled in a pocket
for example. Therefore it is desirable with integral antennae, n connection with mobile telephones.
In EP 0892459 it is described how to tune a planar antenna with two resonance frequencies to desirable frequencies. This is achieved by switching between different tuning elements. Thereby it is possible to provide access to four different radio communication systems.
A drawback with this solution is that it is necessary to switch cetween different tuning elements to tune the an- tenna to tne desired frequency, where the switching requires complex technical solutions and the switching takes time .
Througn US 5926139 it is disclosed how to use a planar antenna m two frequency bands. Two radiating portions are connected to a common feeding portion. Together the three portions have an overall configuration shaped generally like tne letter J. The antenna operates in the frequency bands 824-896 and 1850-1990 MHz.
A drawDack with this solution is that the lower frequency band is narrow.
It is generally known that it is difficult to provide a planar antenna for dual band where tne lower of the two bands covers both GSM 900 and AMPS operating frequencies.
A further frequency band is the 2.4 GHz band, whicn is utilized in Bluetooth applications.
OBJECTS OF THE INVENTION
An ob ect of the present invention is to provide an antenna device that operates in at least two frequency bands, where
the lowest frequency band is sufficiently w de witnout neec of different tuning elements.
Another ooject of the present invention is to provide an antenna device of the kmα initially mentioned that is com- pact and internal m a mobile telephone.
A further object of the present invention is to provide a compact antenna, which is easy and cost effective to produce .
SUMMARY OF THE INVENTION
The invention is based on the realisation that it is possible to provide an internal antenna that operates in a wide lower frequency band and m a higher frequency banα.
The above mentioned objects among others are, according to the invention, attained by an antenna device and by a port- able radio communication device as claimed in the appended claims .
According to the present invention tnere is provided an antenna device as defined n claim 1.
There is also provided an antenna device according to the present invention as defined in claim 14.
There is further provided a portable radio communication device according to the present invention as defined in claim 18.
Further advantages are achieved by features defined in the dependent claims.
BPIEF DESCRIPTION OF DRAWINGS
Tne present invention will become more fully understood from tne detailed description of embodiments of the present invention giver herembelow ana tne accompanying figures, which are given by way of illustration only, and thus are not limitative of the invention, in which:
Fig. 1 shows an antenna device according to the invention,
Fig. 2 shows an embodiment with an additional antenna for short-range communication, and
Fig. 3 snows an exploded view of a portable radio communication device wit an antenna device according to the in¬ vention .
DETAILED DESCRIPTION OF THE INVENTION
In the following description, for purposes of explanation and not limitation, specific details are set fourth, such as particular hardware, applications, techniques, etc. in order to provide a tnorough understanding of the present invention. However, it will be apparent to one skilled in the art that tne present invention may be utilized in other emoodi- ments tnat depart from these specific details. In other in¬ stances, detailed descriptions of well-known metnods, proto¬ cols, apparatuses, and circuits are omitted so as not to ob¬ scure tne description of tne present invention with unneces¬ sary details.
Reference will now be made to Fig. 1, wherein an antenna device for a mobile telephone is shown, where a planar an¬ tenna is utilized to provide wideband multiband frequency coverage .
The antenna device comprises a single planar radiating element 3, having a first and a second portion, which are sr.aped like two orthogonal generally rectangular elements w tn a portion in comm.cn. Th s gives the antenna a general shape of the capital letter L. The first portion, generally enclosed by a dotted line 8 and extending vertically m the figure, resonates essentially in a first, lower frequency oand, and the second portion, generally enclosed by a dotted line 7 and extending horizontally in the figure, reso- nates essentially n a second, higher frequency band.
In order to reduce the length of the second portion a slit 5 is provided, where tne slit has a first part that is approximately 45 degrees angular to an edge of the second portion and a second part that is essentially parallel to the edge of the second portion. With the slit 5 provided it is possible to achieve a desired resonance frequency with an overall length tnat is snorter tnan a quarter of a wavelength, which is convenient to achieve the desired resonance frequency when a grounding element is utilized.
A grounding element is connected, at a point 1, to tne ra¬ diating element 3 at a corner of the common portion and is connectable to a ground element . The ground element 4 is in a plane different from a plane of the radiating element 3. A feeding element is connected, at a point 2, to the ra- diatmg element 3 at an edge of tne first radiating por¬ tion, at a distance d of approximately 15 mm from the grounding element, and is connectable to a transceiver cir¬ cuit (not shown) .
The grounding element could be connected to an edge of the radiating element 3 instead of to a corner. The feeding element would m this case still be connected to the radi-
ating element 3 at an edge of the first portion, at a distance d of approximately 15 mm from the grounding element.
The feeding element could be connected to a notch in the edge of the radiating element 3 in the embodiments de- scribed above.
In order to describe an alternative embodiment according to the present invention reference is made to Fig. 2. An antenna device for a mobile telephone is shown, where two (a first and a second) planar antennae are utilized to provide wideband multiband frequency coverage. The first planar antenna has a radiating element 3 with, dual band coverage, where a lower frequency band and a middle frequency band are provided. The second planar antenna has a radiating element 6 with single band coverage, where a higher fre- quency band is provided.
The first planar antenna is as described above. The second planar antenna has a resonance frequency with sufficient bandwidth so that it is possible to utilize in Bluetooth applications. The second planer antenna utilizes the same ground element as the first planar antenna. It can utilize the same transceiver unit as the first planar antenna or a separate transceiver unit whichever is preferred. It is due to the unique shape of the first planar antenna that it is possible to provide the second planar antenna for Bluetooth applications and still get a compact antenna.
The first frequency band mentioned above is about 824-960 MHz (AMPS and GSM 900) , said second frequency band is about 1710-1880 MHz (DCS 1800) or 1880-1990 MHz (PCS 1900), and said third frequency band is about 2400-2500 MHz (Blue- tooth) .
A portable radio communication device will be described with reference to Fig. 3. The portable radio communication device has a housing that encapsulates an antenna 9, wherein the antenna can be any of previously mentioned an- tenna devices.
Radiating elements described herein is to be interpreted as elements that can both receive and/or transmit radio frequency radiation.
It will be obvious that the invention may be varied in a plurality of ways. Such variations are not to be regarded as a departure from the scope of the invention. Ail such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the appended claims.