WO2009080101A1

WO2009080101A1 - An improved antenna arrangement in an electronic device

Info

Publication number: WO2009080101A1
Application number: PCT/EP2007/064302
Authority: WO
Inventors: Sven Anders Gösta DERNERYD; Patrik Persson; Anders Stjernman; Martin Nils Johansson; Jonas FRIDÉN
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2007-12-20
Filing date: 2007-12-20
Publication date: 2009-07-02

Abstract

An electronic device (100) equipped with means for sending and/or receiving electromagnetic transmissions, said means comprising a first (120) and a second antenna (122) with respective first (121 ) and second (123) radiation patterns which cover a first and a second solid angle. The device is also equipped with a beam forming network (330) which is connected to the first and the second antenna. The beam forming network (330) can use the two antennas (120, 122) in order to simultaneously create a first (340) and a second (350) compound antenna pattern which are de-correlated with respect to each other and which both essentially cover a combination of the solid angles covered by each of the first (121) and second (123) radiation patterns.

Description

TITLE

An improved antenna arrangement in an electronic device.

TECHNICAL FIELD The present invention discloses an electronic device equipped with means for sending and/or receiving electromagnetic transmissions. The sending and/or transmitting means comprise first and second antennas with first and second radiation patterns which cover first and second solid angles.

BACKGROUND

Modern electronic devices, particularly portable devices such as, for example, portable computers ("notebook" computers), personal digital assistants ("PDA"s) and cellular telephones often have a number of integrated antennas for wireless communication.

In the case of, for example, a notebook computer, the antennas are usually arranged in or at the edges of the lid of the computer.

Notebook computers, as well as the other kinds of electronic devices mentioned previously, are usually equipped with means for wireless communications by means of such systems as WLAN, WiMAx and/or cellular telephony systems. These communication means may utilize one of the antennas which the device is equipped with for transmitting and receiving traffic, and in more advanced devices the communication means may use more than one antenna at a time, in order to obtain diversity reception, to utilize MIMO technology (Multiple Input Multiple Output) or to suppress interference.

A drawback with present day solutions in electronic devices is that if two or more antennas are integrated in or arranged at the device, for example at the lid of the device, the radiation patterns of the antennas will often cover different solid angles, sometimes even in the form of opposing hemispheres , which may make the use of diversity technology, MIMO-technology, interference suppression, and multi-standard or multi-frequency communication difficult or impossible in cases in which coinciding beams would be advantageous.

SUMMARY

Thus, as has emerged from the description above, there exists a need for a solution by means of which an electronic device such as for example a portable computer which has at least two antennas available for communication can utilize those antennas simultaneously without being limited by the restrictions caused by the antenna patterns of the individual antennas.

Such a solution is offered by the present invention in that it discloses an electronic device equipped with means for sending and/or receiving electromagnetic transmissions. The send/transmit means comprise at least a first and a second antenna with respective first and second radiation patterns which cover respective first and second solid angles.

The device of the invention is also equipped with a beam forming network which is connected to the first and the second antenna, and the beam forming network can use the two antennas in order to simultaneously create a first and a second compound antenna pattern which are de-correlated with respect to each other and which both essentially cover a combination of the solid angles covered by each of the first and second radiation patterns.

Thus, in a device of the invention, two or more antennas can be used to obtain two or more radiation patterns, each of which essentially covers the same solid angle, that solid angle being the result of taking the union of the solid angles covered by each of the individual radiation patterns of the individual antennas. This and other advantages of the present invention will become even more evident from the detailed description given in another section of this description.

In various embodiments of the invention, the de-correlation between the first and second compound radiation patterns is achieved by means of one of the following, or a combination of them, by means of which different fading characteristics are obtained:

• Spatial separation of the first and second antennas, in order to cause a phase difference between the signals transmitted in the two compound radiation patterns,

• Different frequencies for signals transmitted and/or received by the first and second antennas; • A time delay between the signals transmitted and/or received in the first and second antennas;

• Angular separation between the radiation patterns of the first and second antennas;

• Different polarizations in the first and second antennas.

The invention also discloses a method for use in an electronic device, by means of which the advantages shown above of the inventive device may be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following, with reference to the appended drawings, in which

Fig 1 shows a device in which the invention may be used, and Fig 2 shows radiation patterns of the device of fig 1 , and

Fig 3 shows components of a first embodiment of the invention, and Figs 4-9 show various embodiments of the invention, and Fig 10 shows a flow chart of a method of the invention.

DETAILED DESCRIPTION Fig 1 shows an example of an electronic device 100 in which the invention may be applied. It should be pointed out that this example in no way should be used to restrict the scope of the present invention to a device such as the one shown in fig 1 , the invention can be applied to a wide range of other devices such as, for example, cellular or ordinary cordless telephones, stationary computers or personal digital assistants, PDAs.

In addition, it should also be pointed out that although the invention will be illustrated by means of a device equipped with two antennas, this is merely an example intended to facilitate the reader's understanding of the invention, and should not be seen as limiting the scope of the present invention. As will be realized by those skilled in the field, the invention can be applied to a device with a more or less arbitrary number of antennas.

Returning now to fig 1 , the device 100 shown in fig 1 is a portable computer, a so called "notebook" computer, which has a foldable lid 110 which is rotatable in the direction shown by means of an arrow "A" in fig 1. In addition, the computer 100 also comprises a chassis in which there is arranged a keyboard, said chassis being shown as 130 in fig 1.

As is shown symbolically in fig 1 , the computer 100 is equipped with a first 120 and a second 122 antenna, which are located on the edge of the foldable lid 110 of the computer. Thus, when the computer 100 is in a "standalone use" position, the lid 110 will be in a position which is more or less perpendicular to the chassis, if the computer is placed on, for example, a table. Often, the first and the second antennas will have radiation patterns which do not coincide. This is shown symbolically in fig 2, which shows the first antenna 120 with its radiation pattern 121 , and the second antenna 122 with its radiation pattern 123. In the example shown in fig 2, the two radiation patterns cover entirely different solid angles. As can be understood, the different coverage of the radiation patterns 121 , 123 will make it difficult for the computer 100 to utilize such technologies as for example, MIMO, Multiple Input Multiple Output communication, diversity transmission/reception or interference suppression, since these technologies often call for radiation patterns which at least partly coincide.

The present invention is aimed at making it possible to combine the use of multiple antennas in an electronic device with technologies such as MIMO communication, diversity reception/transmission and interference suppression. An example of how this purpose of the invention is achieved is shown in fig 3. So as not to obscure the drawing, the entire device 100 is not shown in fig 3.

According to the invention, the device 100 is equipped with a beam forming network 330 such as the one shown in fig 3. As indicated in fig 3, the beam forming network 330 is connected to two or more of the antennas 120, 122 in the device 100. The beam forming network 330 will be exemplified in more detail below, but it uses the two antennas 120,122 in order to simultaneously create two compound antenna radiation patterns 340, 350 which are de- correlated with respect to each other and which both essentially cover a combination of the solid angles covered by each of the individual radiation patterns of the two antennas 120, 122.

As can be seen in fig 2, the individual radiation patterns 121 , 123 of the two individual antennas 120, 122 are essentially non-overlapping, but as shown in fig 3, by means of the invention, the two compound radiation patterns 340, 350 each essentially cover the envelope of the union of the individual radiation patterns 121 ,123.

As also shown in fig 3, the beam forming network 330 comprises a first and a second access port 310, 320, at which signals for transmission/reception to/from the antennas 120, 122 can be accessed. In addition, each of the antennas 120, 122 also exhibit an access port 340, 350, to which the beam forming network is connected.

The access ports 310, 320 of the beam forming network 330 each connect to each of the access ports of each antenna, so that signals to/from the antennas can be combined in the desired manner, which will be described in more detail below by means of examples.

It should be pointed out that beam forming networks as such are well known to those skilled in the field of antennas, for which reason examples of beam forming networks will be given below but will not be described in extensive detail, but rather only in a manner which will allow a man skilled in the field to understand how the beam forming network 330 is employed in the present invention.

Thus, examples of beam forming networks which may be used are passive devices such as 3 dB couplers, suitably hybrid 3 dB couplers, phase shifters, delay lines or Butler matrixes. In addition, digital beam forming at baseband level is also possible within the scope of the present invention.

A first example of how the beam forming network 330 of the present invention can use the two antennas 120, 122 to create two compound radiation patterns 340, 350 which each is a composite of the two individual radiation patterns and which are de-correlated with respect to each other is to let (in the case of transmission) the two antennas be spatially separated, so that the compound radiation patterns transmit signals between which there is a phase difference.

This use of phase differences is shown schematically in fig 4, which has the same components as fig 3, but in which the two compound radiation patterns 340, 350 are indicated as having direction-dependent different phases Cp₁, φ₂, in the transmitted signals, so that the radiation patterns 340, 350 become de- correlated with respect to each other. Naturally, the same principle can be used for reception.

In a second embodiment, the beam forming network 330 of the present invention uses the two antennas 120, 122 to create two compound radiation patterns 340, 350 which each is a composite of the two individual radiation patterns and which are de-correlated with respect to each other by (in the case of transmission) transmitting one and the same signal or different signals in each of the compound patterns 340, 350 but on two different frequencies f1 , f2, between which there is a frequency spacing "Δf" which is sufficient to ensure that the fading of the signal in each of the compound radiation patterns make the two radiation patterns de-correlated or "orthogonal".

This use of different frequencies to create de-correlation is shown schematically in fig 5 which has the same components as fig 3, but in which the two compound radiation patterns 340, 350 are indicated as having a frequency separation "Δf" for one and the same transmitted signal or different transmitted signals, so that the signals transmitted at different frequencies using the radiation patterns 340, 350 become de-correlated with respect to each other. Naturally, the same principle can be used for reception.

In a third embodiment of the invention, the beam forming network 330 of the present invention uses the two antennas 120, 122 to create two compound radiation patterns 340, 350 which each is a composite of the two individual radiation patterns and makes them de-correlated with respect to each other by means of an angular separation between the "pointing direction" of the first and second antennas, i.e. the direction of the main beam of the antennas, so that two separate propagation paths with different fading characteristics are obtained.

This use of an angular difference, "angle diversity", is schematically shown in fig 6 which has the same components as fig 3, but in which an angular separation is shown between the first and the second antennas 120, 122 in that a first "pointing" direction or angle G₁ is shown for the first antenna 120 and a second such direction or angle Θ₂ is shown for the second antenna, with a difference between the angles B₁ and G₂. The difference between the angles Θ₁ and Θ₂ is used to exploit multipath propagation to make the signals in the two compound radiation patterns de-correlated with respect to each other. Naturally, this principle can be used both for reception or transmission.

In a further embodiment of the invention, the beam forming network 330 of the present invention uses the two antennas 120, 122 to create two compound radiation patterns 340, 350 which each is a composite of the two individual radiation patterns and makes them de-correlated with respect to each other by means of using a time delay Δt between signals which are transmitted and/or received in the compound radiation patterns.

This use of a time delay, "time diversity", is schematically shown in fig 7 which has the same components as fig 3, but in which a separation in time "Δt" is shown between the signals transmitted using the two compound patterns 340, 350. The separation "Δt" is used to create de-correlated fading between the two compound patterns 340, 350. Naturally, this principle can be used both for reception or transmission.

Another example by means of which the beam forming network 330 of the present invention can use the two antennas 120, 122, is if the radiation patterns of the two antennas are mainly overlapping and of different polarizations which are orthogonal to each other, such as, for example, vertical and horizontal polarization. In such a case, the beam forming network 330 can use the two antennas 120, 122 to create first and second composite radiation patterns which are orthogonal to each other by means of having differing first and second polarizations which are orthogonal to each other, each of which being a polarization which is a composite of the vertical and horizontal polarizations.

The use of different polarization is shown schematically in fig 8 which has the same components as fig 3, but in which the first antenna 120 is indicated as having vertical polarization and the second antenna 122 is indicated as having horizontal polarization, the two antennas having mainly overlapping radiation patterns, with the two compound radiation patterns 340, 350 being indicated as having different polarizations, Pi and P₂, which are thus two different composites of horizontal and vertical polarization which are orthogonal to each other. It should be pointed out that the two polarizations P1 and P2 do not need to be vertical and horizontal, these two polarizations are merely examples intended to facilitate the reader's understanding of the "polarization embodiment" of the invention.

An additional manner by means of which the beam forming network 330 of the present invention can use the two spatially separated antennas 120, 122, is if the radiation patterns of the two antennas are mainly overlapping and of the same polarization. In such a case, the beam forming network 330 can use the two antennas 120, 122 to create first 340 and second 350 compound radiation patterns which are orthogonal to each other by means of having interleaved radiation pattern maxima and minima, which are such that when the compound pattern 340 has a maximum the compound pattern 350 has a minimum, and vice versa. In fig 9, a further embodiment 900 of an electronic device of the invention is shown. This embodiment 900 is similar to the embodiment 100 shown in fig 1 , and in other words is an electronic device which comprises at least a first 120 and a second 122 antenna.

However, the embodiment 900 differs from the embodiment 100 in the placement of the antennas: as is shown in fig 9, the first and second antennas 120, 122 are asymmetrically arranged along different edges of the electronic device 900, so that no "symmetry planes" can be found in the electronic device 900 with respect to the location of the two antennas.

The asymmetric arrangement of the antennas 120, 122 is due to the fact that with antennas arranged symmetrically on a device, i.e. so that a plane of symmetry can be found in the device with respect to the antennas, there is a risk that the individual radiation patterns of the two antennas will have coinciding "nulls". In order to avoid such coinciding nulls between the radiation patterns of the antennas of the inventive electronic device, the antennas may be placed asymmetrically on or in the device, for example along different edges as shown in fig 9.

Fig 10 shows a rough flow chart of a method 1000 of the invention. Steps which are options or alternatives are shown with dashed lines.

The method of the invention, which is shown in fig 10, is intended for use in an electronic device such as the one 100 shown in fig 1 , and comprises the steps of:

• equipping, step 1010, the device with means for sending and/or receiving electromagnetic transmissions,

• letting, step 1015, the means for sending and/or receiving comprise at least a first and a second antenna, such as the ones 120, 122 shown in figs 1-8 and described above, • letting, step 1020, the first and second antennas have radiation patterns which cover a first Ωi and a second solid angle Ω₂ respectively,

• equipping, step 1025, the device with a beam forming network such as the one 330 shown in figs 3-8 above, which is connected to the first and the second antenna.

As indicated in step 1030, according to the inventive method, the beam forming network is used to utilize the two antennas to simultaneously create a first 340 and a second 350 compound antenna pattern which are de- correlated with respect to each other and which both essentially cover a combination of the solid angles covered by each of the first 121 and second 123 radiation patterns.

Step 1035 indicates that, as has also been explained above, that the solid angles covered by the radiation patterns of the first and second antennas are made to be either overlapping, partly overlapping or non-overlapping.

Steps 1040-1060 show various ways of obtaining the de-correlation between the compound radiation patterns, which are used in various embodiments of the invention:

As shown in step 1040, the de-correlation between the first and second compound radiation patterns can be achieved by using different polarizations P-i, P₂, in the first and second antennas.

Step 1045 shows that the de-correlation between the first and second compound radiation patterns can be achieved by creating a phase difference Δφ between the signals transmitted and/or received from the first and the second antennas. As shown in step 1050, the de-correlation between the first and second compound radiation patterns can also be achieved by using different frequencies, so that a frequency difference Δf is created between signals transmitted and/or received by the first and second antennas.

Step 1055 shows that the de-correlation between the first 340 and second 350 compound radiation patterns can be achieved by using an angular separation θ between the "pointing directions" of the first 120 and second 122 antennas, so that two separate propagation paths with different fading characteristics are obtained.

Another way of obtaining the de-correlation between the first and second compound radiation patterns is shown in step 1060: a time delay, Δt, can be created between the signals transmitted and/or received by the first and second antennas.

Also according to the method of the invention, the first and second antennas can in one embodiment be placed asymmetrically in the device, so as to avoid coinciding null directions in the radiation patterns of the antennas.

The method of the invention can be applied to a variety of devices, such as, for example:

• a portable computer,

• a wireless telephone such as a telephone for cellular communications or a cordless telephone,

• a personal digital assistant, a PDA, as the electronic device.

The invention is not limited to the examples of embodiments described above and shown in the drawings, but may be freely varied within the scope of the appended claims. For example, more than two individual antennas may be employed to generate the compound radiation patterns of the invention.

Claims

1. An electronic device (100) equipped with means for sending and/or receiving electromagnetic transmissions, said means comprising at least a first (120) and a second antenna (122) with respective first (121) and second (123) radiation patterns which cover a first and a second solid angle, the device also being equipped with a beam forming network (330) which is connected to the first and the second antenna, the device (100) being characterized in that the beam forming network (330) can use the two antennas (120, 122) in order to simultaneously create a first (340) and a second (350) compound antenna pattern which are de-correlated with respect to each other and which both essentially cover a combination of the solid angles covered by each of the first (121) and second (123) radiation patterns.

2. The electronic device (100) of claim 1 , in which the solid angles covered by the radiation patterns of the first (120) and second (122) antennas are either overlapping, partly overlapping or non-overlapping.

3. The electronic device (100) of claim 1 or 2, in which the de-correlation between the first (340) and second (350) compound radiation patterns is achieved by means of different polarizations (P₁, P₂) being used in the first (120) and second (122) antennas.

4. The electronic device (100) of claim 1 or 2, in which the de-correlation between the first (340) and second (350) compound radiation patterns is achieved by means of a phase difference (Cp₁, φ₂) between the signals transmitted and/or received from the first (120) and the second (122) antennas.

5. The electronic device (100) of claim 1 or 2, in which the de-correlation between the first (340) and second (350) compound radiation patterns is achieved by means of using different frequencies (Δf) for signals transmitted and/or received by the first (120) and second (122) antennas.

6. The electronic device (100) of claim 1 or 2, in which the de-correlation between the first (340) and second (350) compound radiation patterns is achieved by means of using angular separation (θ) between pointing directions of the first (120) and second (122) antennas so that two separate propagation paths with different fading characteristics are obtained.

7. The electronic device (100) of claim 1 or 2, in which the de-correlation between the first (340) and second (350) compound radiation patterns is achieved by means of using a time delay (Δt) between the signals transmitted and/or received by the first (120) and second (122) antennas.

8. The electronic device (900) of any of the previous claims, in which the antennas (120,122) are placed asymmetrically in the device, so as to avoid coinciding null directions in the radiation patterns of the antennas.

9. The electronic device (100, 900) of any of the previous claims, being a portable computer.

10. The electronic device (100, 900) of any of claims 1-7, being a wireless telephone such as a telephone for cellular communications or a cordless telephone.

11. The electronic device (100, 900) of any of claims 1-6, being a personal digital assistant, a PDA.

12. A method (1000) for use in an electronic device (100), the method comprising the steps of:

• equipping (1010) the device with means for sending and/or receiving electromagnetic transmissions, • letting (1015) said means for sending and/or receiving comprise at least a first (120) and a second antenna (122),

• letting (1020) the first and second antennas have radiation patterns which cover a first and a second solid angle respectively, • equipping (1025) the device with a beam forming network (330) which is connected to the first and the second antenna, the method (1000) being characterized in that (1030) the beam forming network (330) is used to utilize the two antennas (120, 122) in order to simultaneously create a first (340) and a second (350) compound antenna pattern which are de-correlated with respect to each other and which both essentially cover a combination of the solid angles covered by each of the first (121) and second (123) radiation patterns.

13. The method (1000, 1035) of claim 12, according to which the solid angles covered by the radiation patterns of the first (120) and second (122) antennas are made to be either overlapping, partly overlapping or non- overlapping.

14. The method (1000, 1040) of claim 12 or 13, according to which the de- correlation between the first (340) and second (350) compound radiation patterns is achieved by using different polarizations (P-i , P₂) in the first (120) and second (122) antennas.

15. The method (1000, 1045) of claim 12 or 13, according to which the de- correlation between the first (340) and second (350) compound radiation patterns is achieved by creating a phase difference (φi, q>₂) between the signals transmitted and/or received from the first (120) and the second (122) antennas.

16. The method (1000, 1050) of claim 12 or 13, according to which the de- correlation between the first (340) and second (350) compound radiation patterns is achieved by using different frequencies (Δf) for signals transmitted and/or received by the first (120) and second (122) antennas.

17. The method (1000, 1055) of claim 12 or 13, according to which the de- correlation between the first (340) and second (350) compound radiation patterns is achieved by using an angular separation (θ) between the pointing directions of the first (120) and second (122) antennas, so that two separate propagation paths with different fading characteristics are obtained.

18. The method (1000, 1060) of claim 12 or 13, according to which the de- correlation between the first (340) and second (350) compound radiation patterns is achieved by using a time delay (Δt) between the signals transmitted and/or received by the first (120) and second (122) antennas.

19. The method of any of claims 12-18, according to which the antennas (120,122) are placed asymmetrically in the device, so as to avoid coinciding null directions in the radiation patterns of the antennas.

20. The method of any of claims 12-18, applied to a portable computer as the electronic device.

21. The method of any of claims 12-18, applied to an electronic device such as a wireless telephone, i.e. a telephone for cellular communications or a cordless telephone.

22. The method of any of claims 12-18, applied to a personal digital assistant, a PDA, as the electronic device.