Dual feed multiband antenna and a portable radio communication device comprising such an antenna

Abstract

 The present invention relates to an antenna device for a portable radio communication device, comprising a first radiating element (1) having a first feed portion (5), a second radiating element (2) having a second feed portion (6), a first filter (3) and a second filter (4), wherein said first and second radiating elements (1, 2) are interconnected through said first filter (3), said first radiating element (1) is configured to be tuned to a first frequency band, and said second radiating element (2) is configured to be tuned to a second frequency band, wherein said first radiating element (1) is configured to be fed by at least said first frequency band and a third frequency band lower than said first frequency band and said second frequency band through said first feed portion (5), said second radiating element (2) is configured to be fed by said second frequency band through said second filter (4), said first filter (3) is configured to block said first and second frequency bands and pass said third frequency band, and said second filter (4) is configured to block said third frequency band and pass said second frequency band.

Description

FIELD OF INVENTION

[0001] The present invention relates generally to antennas, and particularly to antenna devices for portable radio communication devices.

BACKGROUND

[0002] The market for portable radio communication devices, such as mobile phones, PDA, portable computers and similar devices, is today very competitive, which puts tough demands on the manufacturers. Furthermore, antennas of such devices many times only have access to limited space of different shapes.

SUMMARY OF THE INVENTION

[0003] An object of the present invention is thus to provide an antenna device which can have reduced size or improved performance compared to known solutions, for a portable radio communication device.

[0004] This object, among others, is according to the present invention attained by an antenna device and a portable radio communication device, respectively, as defined by the appended claims.

[0005] By providing an antenna device, for a portable radio communication device, comprising a first radiating element having a first feed portion, a second radiating element having a second feed portion, a first filter and a second filter, wherein the first and second radiating elements are interconnected through the first filter, the first radiating element is configured to be tuned to a first frequency band, and the second radiating element is configured to be tuned to a second frequency band, wherein the first radiating element is configured to be fed by at least the first frequency band and a third frequency band lower than the first frequency band and the second frequency band through the first feed portion, the second radiating element is configured to be fed by the second frequency band through the second filter, the first filter is configured to block the first and second frequency bands and pass the third frequency band, and the second filter is configured to block the third frequency band and pass the second frequency band, reduced size can be achieved compared to known antenna devices since the highest frequency band utilizes the antenna volume more efficiently.

[0006] By preferably providing the antenna device over ground or close to ground the first or second radiating element advantageously has a ground portion for grounding the antenna device.

[0007] To improve isolation between the radiating elements the first feed portion is preferably arranged at the first radiating element facing away from the second radiating element and/or the second feed portion is preferably arranged at the second radiating element facing away from the first radiating element.

[0008] Further features and advantages of the present invention will be evident from the following description.

BRIEF DESCRIPTION OF THE DRAWING

[0009] The present invention will become more fully understood from the detailed description of embodiments given below and the accompanying figure, which is given by way of illustration only, and thus, is not limitative of the present invention, wherein:

Fig. 1 schematically illustrates an antenna device according to a first embodiment of the present invention.

Fig. 2 schematically illustrates an antenna device according to a second embodiment of the present invention.

Fig. 3 schematically illustrates an antenna device according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0010] In the following description, for purpose of explanation and not limitation, specific details are set forth, such as particular techniques and applications in order to provide a thorough understanding of the present invention. However, it will be apparent for a person skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed description of well-known methods and apparatuses are omitted so as not to obscure the description of the present invention with unnecessary details.

[0011] An antenna device according to a first embodiment of the present invention will now be described with reference to Fig. 1.

[0012] The antenna device for a portable radio communication device, such as a mobile phone, a PDA, a portable computer and similar devices, comprises a first radiating element 1 having a first feed portion 5, a second radiating element 2 having a second feed portion 6, a first filter 3, which preferably is a low pass filter 3, and a second filter 4, which preferably is a high pass filter 4. The first radiating element 1 and the second radiating element 2 are connected through the low pass filter 3. The first radiating element 1 is configured to be tuned to a first frequency band and the second radiating element 2 is configured to be tuned to a second frequency band, preferably in the same range or higher than the first frequency band. The low pass filter 3 connects the first radiating element 1 and the second radiating element 2, wherein the position of the low pass filter 3 between the radiating elements 1 and 2 is a part of the specific antenna design and may thus vary.

[0013] The first radiating element 1 is configured to be fed by the first frequency band and a third frequency band lower than the first frequency band and the second frequency band. Preferably both the first and third frequency bands are fed through the first feed portion 5. Alternatively, the first radiating element 1 is provided with a third feed portion, and the first and third frequency bands are fed through the first and third feed portions, respectively. The first radiating element 1, the second radiating element 2 and the low pass filter 3 together are configured to be tuned to the third frequency band.

[0014] The second radiating element 2 is configured to be fed by the second frequency band. The second frequency band is fed through the high pass filter 4, which is configured to block at least the third frequency band and pass the second frequency band. The high pass filter 4 could further be configured to also block the first frequency band, although is should be sufficiently blocked by the low pass filter 3 as described below.

[0015] The low pass filter 3 is configured to block the first and second frequency bands and to pass the third frequency band. The high pass filter 4 and the low pass filter 3 are preferably provided by lumped components, since it provides a high degree of design freedom. Alternatively, the filters 3 and 4 are provided by e.g. distributed components that are implemented in the pattern of the antenna elements 1 and/or 2. Also, a filter component (e.g. ceramic or LTCC) can be used directly to provide desired filtering.

[0016] The antenna device is preferably provided with a grounding portion 8 for the first radiating element 1, when the antenna device is arranged over ground or near ground, in order to ground the antenna device.

[0017] The radiating elements 1 and 2 are depicted as patches. However, the radiating elements 1 and 2 can also be made like e.g. off-ground antennas (monopole or IFA). The antenna device can also be provided with parasitic radiators to boost performance in one band, having no galvanic connection to the radiating elements 1 and 2 themselves.

[0018] Although the filters have been described above as low pass filter and high pass filter, respectively, they could alternatively be e.g. bandpass or bandstop filters.

[0019] At least the third frequency band is preferably distinct apart from the first and second frequency bands, for relevant separation of the two radiating elements, to allow use of simple filters. Also the first and second frequency bands are preferably distinct apart.

[0020] For an antenna device arranged to provide e.g. tri-band GSM and WCDMA the configuration would be as follows.

[0021] Tri-band GSM comprises GSM900, 1800 and 1900, which would be fed through the first feed portion 5 to the first radiating element 1. WCDMA2100 would be fed through the high pass filter 4 and the second feed portion 6 to the second radiating element 2. The first filter 3 is configured to pass frequencies below 1400 MHz and block frequencies there above. The second filter 4 is configured to pass signals over 1900 MHz and block frequencies there below. The first radiating element 1 is configured for passing S₁₁ requirements for GSM1800 and 1900. The second radiating element 2 is configured for passing S₁₁ requirements for

[0022] WCDMA. The first and second radiating elements 1 and 2 are together configured to pass S₁₁ requirements for GSM900.

[0023] For an antenna device arranged to provide e.g. GSM900, GSM1800 and GSM1900 with reception diversity for the high bands the configuration would be as follows.

[0024] GSM comprises Rx and TX frequency bands. GSM 900 Rx and Tx, GSM1800 RX and Tx, as well as GSM1900 Rx and Tx would be fed through the first feed portion 5 to the first radiating element 1. GSM1800 Rx and GSM1900 Rx would be fed through the high pass filter 4 and the second feed portion 6 to the second radiating element 2. The first filter 3 is configured to pass frequencies below 1400 MHz and block frequencies there above. The second filter 4 is configured to pass frequencies above 1400 MHz and block frequencies there below. The first radiating element 1 is configured for passing S₁₁ requirements for GSM1800 and GSM1900. The second radiating element 2 is configured for passing S₁₁ requirements for GSM1800 Rx and GSM1900 Rx. The first and second radiating elements 1 and 2 are together configured to pass S₁₁ requirements for GSM900.

[0025] An antenna device according to a second embodiment of the present invention will now be described with reference to Fig. 2. This second embodiment is identical to the first embodiment described above apart from the following.

[0026] A grounding portion 9 is arranged on the second radiating element 2 instead of on the first radiating element 1, which provides for a different functionality of the antennas according to the first and second embodiments, especially in the third frequency band. By arranging the grounding portion 9 on the second radiating element 2, preferably close to the high pass filter 4, implementation of the high pass filter 4 is facilitated, since the impedance of the radiating element will be low close to the grounding portion 9, which in turn implies that the third frequency band attains a half-wave structure (such as a loop structure). In connection herewith the grounding portion 9 is preferably positioned less than 10 mm from the high pass filter 4, more preferably less than 5 mm, and most preferably less than 2 mm.

[0027] The grounding portion 9 can alternatively be arranged on the first radiating element 1, or not used at all, as in the first embodiment described above.

[0028] An antenna device according to a third embodiment of the present invention will now be described with reference to Fig. 3. This third embodiment is identical to the second embodiment described above apart from the following.

[0029] A third filter 10 is provided between the first and second radiating elements 1 and 2. The use of a third filter 10 allows greater flexibility in design of the desired filter functions.

[0030] It will be obvious that the present invention may be varied in a plurality of ways. Such variations are not to be regarded as departure from the scope of the present invention as defined by the appended claims. All such variations as would be obvious for a person skilled in the art are intended to be included within the scope of the present invention as defined by the appended claims.

Claims

1. An antenna device for a portable radio communication device, comprising a first radiating element (1) having a first feed portion (5), a second radiating element (2) having a second feed portion (6), a first filter (3) and a second filter (4), characterized in that said first and second radiating elements (1, 2) are interconnected through said first filter (3), said first radiating element (1) is configured to be tuned to a first frequency band, and said second radiating element (2) is configured to be tuned to a second frequency band, wherein said first radiating element (1) is configured to be fed by at least said first frequency band and a third frequency band lower than said first frequency band and said second frequency band, said second radiating element (2) is configured to be fed by said second frequency band through said second filter (4), said first filter (3) is configured to block said first and second frequency bands and pass said third frequency band, and said second filter (4) is configured to block said third frequency band and pass said second frequency band.

2. The antenna device as claimed in claim 1, wherein said first radiating element (1) has a ground portion (8) for grounding said antenna device.

3. The antenna device as claimed in claim 1 or 2, wherein said second radiating element (2) has a ground portion (9) for grounding said antenna device.

4. The antenna device as claimed in claim 3, wherein said ground portion (9) on said second radiating element (2) is arranged close to said second feeding portion (6).

5. The antenna device as claimed in any of claims 1-4, wherein said first feed portion (5) is arranged at said first radiating element (1) facing away from said second radiating element (2).

6. The antenna device as claimed in any of claims 1-5, wherein said second feed portion (6) is arranged at said second radiating element (2) facing away from said first radiating element (1).

7. The antenna device as claimed in any of claims 1-6, wherein said first radiating element (1), said second radiating element (2) and said first filter (3) together are configured to be tuned to said third frequency band.

8. The antenna device as claimed in any of claims 1-7, wherein said first frequency band and said third frequency band are fed through said first feed portion (5).

9. The antenna device as claimed in any of claims 1-8, wherein said first radiating element (1) has a third feed portion, wherein said first frequency band is fed through said first feed portion (5) and said third frequency band is fed through said third feed portion.

10. The antenna device as claimed in any of claims 1-9, wherein said second frequency band is higher than said first frequency band.

11. The antenna device as claimed in any of claims 1-10, wherein said first and second frequency bands are distinct apart.

12. The antenna device as claimed in any of claims 1-11, wherein said first and third frequency bands are distinct apart.

13. A portable radio communication device characterized in that is comprises an antenna device as claimed in any of claims 1-12.

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