GB2404791A

GB2404791A - Compact antenna arrangement for simultaneous operation under two different protocols

Info

Publication number: GB2404791A
Application number: GB0417507A
Authority: GB
Inventors: James William Kingsley; Brian Collins
Original assignee: Antenova Ltd
Current assignee: Antenova Ltd
Priority date: 2003-08-08
Filing date: 2004-08-06
Publication date: 2005-02-09
Anticipated expiration: 2024-08-06
Also published as: WO2005015689A1; GB0417507D0; GB0318667D0; GB2404791B

Abstract

An antenna arrangement comprises first and second antenna structures 33, 34, where the said structures are arranged within a common plane and the first antenna structure 33 is a multi-band antenna and the second antenna structure 34 is configured to operate with a polarisation direction which is parallel to the said plane. The first antenna structure 33 may comprise dielectric and conductive component combinations which operate at different and non-interacting frequencies which may involve a parasitic member. The antenna 33 may have a single feed with the antenna components being fed in series or in parallel. The said antenna 33 may involve dielectric antenna or dielectric loaded antenna arrangements and may include printed or strip dipole or stacked patch formations. The second antenna structure 34 may be a short-circuited quarter wavelength patch antenna. The said structures 33, 34 may be elongate such that they fit in the frame of a display 2. Two of the first antenna structures 33 may be located close to each other with orthogonal longitudinal axes and orthogonal or opposed polarisations. The second antenna structure 34 may be arranged in the frame to optimise its isolation from the first antenna structures 33. The first antennas 33 may be for WLAN operation and the second antenna 34 may be for Bluetooth (RTM) operation.

Description

2404791

ANTENNAS FOR WIRELESS COMMUNICATION TO A LAPTOP

COMPUTER

There is an increasing demand for the provision of wireless data communications for 5 the users of computing or communications equipment, especially small equipment, where it is required to provide a number of different co-existing services with significant mutual isolation. Such equipment includes portable or laptop computers, tablet computers, personal digital assistants (PDAs), navigation devices, printers and other peripheral devices. A particular device may be required to support wireless 10 communications by way of a number of different data standards operating in various frequency bands. To enhance the operation of these communication links, some services will employ the techniques of space- or polarisation-diversity. These requirements create the need for a number of different antennas to be mounted on a single small portable device; additionally the designer must provide sufficient mutual 15 isolation between these antennas to permit the proper and independent operation of the various services provided.

The present invention relates to arrangements of antennas on a laptop computer, PDA or the like, both the type of antennas and their disposition, in order to achieve good 20 isolation between the antennas. Both dielectric and non-dielectric antennas may be deployed in these arrangements. The present invention is not concerned with the design of the individual antenna elements per se, one of which is described in UK patent application no 0313890.6 of 16th June 2003, the full contents of which are hereby incorporated into the present application by reference. Suitable dielectric 25 antennas include, but are not limited to, dielectric resonator antennas (DRAs), high dielectric antennas (HDAs), dielectrically loaded antennas (DLAs) and dielectrically excited antennas (DEAs).

It is known from US 6,339,400 to provide an integrated antenna for a laptop 30 computer in which one or more traditional slot antennas or planar inverted-F antennas (PIFAs) are mounted on a metal frame surrounding a display of the laptop

1

computer. There is no consideration in the disclosure of multi-band operation and antenna isolation.

It is known from US 6,115,762 to provide an antenna formed on a PCB or the like 5 and to embed this within a computing device, either by integrating the antenna on a PCB of the computing device itself, or by forming the antenna on a separate PCB and then inserting this into a slot, such as a PCMCIA slot, of the computing device. The antenna is provided with beamsteering capability, but there is no discussion of multi-band operation and antenna isolation.

10

US 6,380,898 discloses a dual mode antenna for attachment to a laptop. The antenna is an extendible external antenna, and only one antenna is provided on the laptop.

EP 1 079 296 discloses an electronically steerable array of patch antennas embedded 15 in a back of a display screen component of a laptop. Again, this does not address multi-band operation and antenna isolation.

Dielectric antennas are devices that radiate or receive radio waves at a chosen frequency of transmission and reception, as used in for example in mobile 20 telecommunications. In general, a dielectric antenna consists of a volume of a dielectric material disposed on or close to a grounded substrate, with energy being transferred to and from the dielectric material by way of monopole probes inserted into the dielectric material or by way of monopole aperture feeds provided in the grounded substrate (an aperture feed is a discontinuity, generally rectangular in 25 shape, although oval, oblong, trapezoidal or butterfly/bow tie shapes and combinations of these shapes may also be appropriate, provided in the grounded substrate where this is covered by the dielectric material. The aperture feed may be excited by a strip feed in the form of a microstrip transmission line, coplanar waveguide, slotline or the like which is located on a side of the grounded substrate 30 remote from the dielectric material). Direct connection to and excitation by a microstrip transmission line is also possible. Alternatively, dipole probes may be

2

inserted into the dielectric material, in which case a grounded substrate is not required. By providing multiple feeds and exciting these sequentially or in various combinations, a continuously or incrementally steerable beam or beams may be formed, as discussed for example in the present applicant's co-pending US patent 5 application serial number US 09/431,548 and the publication by KINGSLEY, S.P. and O'KEEFE, S.G., "Beam steering and monopulse processing of probe-fed dielectric resonator antennas", IEE Proceedings - Radar Sonar and Navigation, 146, 3,121 - 125, 1999, the full contents of which are hereby incorporated into the present application by reference.

10

The resonant characteristics of a dielectric antenna depend, inter alia, upon the shape and size of the volume of dielectric material, the shape, size and position of the feeds thereto and also on the shape, size and position of the groundplane. It is to be appreciated that in a dielectric antenna, it is the dielectric material that radiates when 15 excited by the feed. This is to be contrasted with a dielectrically loaded antenna (DLA), in which a traditional conductive radiating element is encased in a dielectric material that modifies the resonance characteristics of the radiating element. As a further distinction, a DLA has either no, or only a small, displacement current flowing in the dielectric whereas a DRA or HDA has a non-trivial displacement 20 current.

Dielectric antennas may take various forms, a common form having a cylindrical shape or half- or quarter-split cylindrical shape. The resonator medium can be made from several candidate materials including ceramic dielectrics.

25

Dielectric resonator antennas (DRAs) were first studied systematically in 1983 [LONG, S.A., MCALLISTER, M.W., and SHEN, L.C.: "The Resonant Cylindrical Dielectric Cavity Antenna", IEEE Transactions on Antennas and Propagation, AP-31, 1983, pp 406-412]. Since then, interest has grown in their radiation patterns because 30 of their high radiation efficiency, good match to most commonly used transmission lines and small physical size [MONGIA, R.K. and BHARTIA, P.: "Dielectric

3

Resonator Antennas - A Review and General Design Relations for Resonant Frequency and Bandwidth", International Journal of Microwave and Millimetre-Wave Computer-Aided Engineering, 1994, 4, (3), pp 230-247]. A summary of some more recent developments can be found in PETOSA, A., ITTIPIBOON, A., ANTAR, 5 Y.M.M., ROSCOE, D., and CUHACI, M.: "Recent advances in Dielectric-Resonator Antenna Technology", IEEE Antennas and Propagation Magazine, 1998, 40, (3), pp 35 -48.

A variety of basic shapes have been found to act as good dielectric resonator 10 structures when mounted on or close to a ground plane (grounded substrate) and excited by an appropriate method. Perhaps the best known of these geometries are:

Rectangle [McALLISTER, M.W., LONG, S.A. and CONWAY G.L.: "Rectangular Dielectric Resonator Antenna", Electronics Letters, 1983, 19, (6), pp 15 218-219].

Triangle [ITTIPIBOON, A., MONGIA, R.K., ANTAR, Y.M.M., BHARTIA, P. and CUHACI, M.: "Aperture Fed Rectangular and Triangular Dielectric Resonators for use as Magnetic Dipole Antennas", Electronics Letters, 1993, 29, (23), pp 2001-20 2002],

Hemisphere [LEUNG, K.W.: "Simple results for conformal-strip excited hemispherical dielectric resonator antenna", Electronics Letters, 2000, 36, (11)].

25 Cylinder [LONG, S.A., McALLISTER, M.W., and SHEN, L.C.: "The Resonant Cylindrical Dielectric Cavity Antenna", IEEE Transactions on Antennas and Propagation, AP-31,1983, pp 406-412].

Half-split cylinder (half a cylinder mounted vertically on a ground plane) 30 [MONGIA, R.K., ITTIPIBOON, A., ANTAR, Y.M.M., BHARTIA, P. and CUHACI,

4

M: "A Half-Split Cylindrical Dielectric Resonator Antenna Using Slot-Coupling", IEEE Microwave and guided Wave Letters, 1993, Vol. 3, No. 2, pp 38-39].

Some of these antenna designs have also been divided into sectors. For example, a 5 cylindrical DRA can be halved [TAM, M.T.K. and MURCH, R.D.: "Half volume dielectric resonator antenna designs", Electronics Letters, 1997, 33, (23), pp 1914 -1916]. However, dividing an antenna in half, or sectoring it further, does not change the basic geometry from cylindrical, rectangular, etc.

10 High dielectric antennas (HDAs) are similar to DRAs, but instead of having a full ground plane located under the dielectric resonator, HDAs have a smaller ground plane or no ground plane at all. DRAs generally have a deep, well-defined resonant frequency, whereas HDAs tend to have a less well-defined response, but operate over a wider range of frequencies. HDAs can take the same variety of preferred shapes as 15 DRAs. However, any arbitrary dielectric shape can be made to radiate and this can be useful when trying to design the antenna to be conformal to its casing.

In both DRAs and HDAs, the primary radiator is the dielectric resonator. In DLAs the primary radiator is a conductive component (e.g. a copper wire or the like) and 20 the dielectric modifies the medium in which the antenna operates, and generally makes the antenna smaller. Dielectrically excited antennas (DEAs) are similar to DLAs in that the primary radiator is a conductive component (such as a copper dipole or patch), but unlike DLAs they have no feed mechanism. DEAs are parasitic conducting antennas that are excited by a nearby dielectric or dielectric antenna 25 having its own feed mechanism. There are advantages to this arrangement, as outlined in UK patent application no 0313890.6 of 16th June 2003.

For the avoidance of doubt, the expression "electrically-conductive antenna components" defines a traditional antenna component such as a patch antenna, slot 30 antenna, monopole antenna, dipole antenna, planar inverted-L antenna (PILA) or any other antenna component that is not a DRA, HDA, DLA or DEA. In some preferred

5

embodiments of the present invention, use is made of printed or strip dipoles and patches.

Additionally, for the purposes of the present application, the expression "dielectric 5 antenna" is hereby defined as encompassing DRAs, HDAs, DLAs and DEAs.

Embodiments of the present invention thus relate to the use of DRAs, HDAs, DLAs and DEAs as one type of primary radiating structure that is used in conjunction with an electrically-conductive antenna component in order to achieve high isolation 10 between the antennas.

According to a first aspect of the present invention, there is provided an antenna arrangement comprising at least first and second antenna structures each having a longitudinal axis, the antenna structures being arranged such that their longitudinal 15 axes are all substantially in a given plane, characterised in that the first antenna structure is a multi-band antenna and in that the second antenna structure is configured to operate with a direction of polarisation parallel to the given plane.

Preferably, the antenna structures are generally elongate. The antenna structures are 20 also preferably substantially thin or planar along their longitudinal axes.

The given plane may be defined by a display screen of a laptop computer or PDA or other device having a display screen. The antenna structures are preferably located at edges of or in a border of the display screen.

25

In a particularly preferred embodiment, the first antenna structure includes at least one dielectric antenna component configured to operate at a first frequency. The first antenna structure additionally comprises a second antenna component, which may also be a dielectric antenna component, or may be an electrically-conductive antenna 30 component. The second antenna component is configured to operate at a second frequency different from the first frequency, thus providing dual band operation of

6

the first antenna structure as a whole. It will be appreciated that additional antenna components may be provided in the first antenna structure so as to enable operation at more than two frequencies or bands of frequencies. The first and second antenna components may both be fed from a common feed point, either in series or in 5 parallel.

Where both the first and second antenna components of the first antenna structure are both dielectric antennas, they may be provided with a common feed, such as a direct microstrip transmission line, or a microstrip transmission line with slot coupling to 10 the dielectric components, or any other suitable feed. In this case, the dielectric components may be shaped and sized differently from each other to provide dual band operation. Alternatively, each of the first and second dielectric antenna components may be provided with its own feed. Where a common feed is provided, the first and second dielectric components may be fed in series or in parallel.

15

Alternatively, where the second antenna component of the first antenna structure is an electrically-conductive antenna, for example a PILA or patch antenna or the like, it need not be electrically connected to the first dielectric antenna component or to the feed, but is parasitically excited by the first dielectric antenna component so as to 20 operate at a different frequency determined by the configuration of the second electrically-conductive antenna component. This arrangement is described in more detail in the present applicant's co-pending UK patent application no 0313890.6.

It is particularly preferred that the first and second antenna components of the first 25 antenna structure are configured to resonate or radiate at first and second respective frequencies, with the first antenna component being relatively impervious or unresponsive to feed signals at the second frequency, and the second antenna component being relatively impervious or unresponsive to feed signals at the first frequency.

30

7

For example, where the first antenna structure comprises a first dielectric antenna component that operates at 5GHz, and a second electrically-conductive antenna component that operates at around 2.4 to 2.5GHz, the first dielectric antenna component is preferably configured so as to present a relatively insignificant 5 response discontinuity at around 2.4 to 2.5GHz. In this way, feed signals at around 2.4 to 2.5GHz, provided along a feedline which connects the first and second antenna components to each other in series, will tend to travel from a feed point, past the first dielectric antenna component and then to the second electrically-conductive antenna component so as to excite this second component. The second electrically-10 conductive antenna component is configured so as not to resonate at 5GHz, but instead to present an almost purely reactive input impedance at this frequency, and therefore feed signals at around 5GHz will excite only the first dielectric antenna component. The length of a feedline joining the first and second antenna components is chosen carefully, according to known RF transmission line techniques, so that the 15 impedance presented at an adjacent end of the first dielectric antenna component is effectively an open circuit, thereby resulting in the operation of the first dielectric antenna component being relatively unaffected by the presence of the second electrically-conductive antenna component.

20 In an alternative, parallel-fed example, the first and second antenna components may be fed from a feed point located in between the two components, with a feedline extending from the feed point in both directions towards the respective first and second antenna components. Again, a key point is that the first and second antenna components respectively present an almost completely reactive impedance at the 25 frequency of operation of the other. By careful selection of the respective lengths of feedline from the common feed point, the impedance of the first antenna component is made to be a "virtual" open circuit at the frequency of operation of the second antenna component and vice versa. The input impedance at each frequency may be essentially that same as that of the antenna component that operates at that frequency.

30

8

In both series-fed and parallel-fed configurations, not only is the input impedance preserved at each frequency, but only the antenna component that is actually operating at any given time will carry any significant current, so that its radiation pattern is substantially undisturbed by the presence of the other antenna component.

5 These characteristics are generally maintained both when only a single signal frequency is input, or when both signal frequencies are input simultaneously. Indeed, these are the characteristics that would be obtained if a diplexing filter were used to feed both first and second antenna components from a single feed point, and the first and second antenna components of the antenna structure of embodiments of the 10 present invention may therefore be considered to be "self-diplexing".

The second antenna structure is preferably an electrically-conductive antenna structure. The key feature of the second antenna structure is that it is configured such that, in operation, it transmits radio signals having a polarisation parallel to the given 15 plane. In this way, it is possible to reduce or prevent the generation of surface waves which may propagate across a display screen or casing of a laptop computer or the like.

The antenna arrangement of embodiments of the present invention may comprise two 20 of the first antenna structures mounted relatively close to each other, for example on adjacent edges of a display screen, with the second antenna structure being located relatively far from the first antenna structures, for example at an opposed edge of the display screen. The two first antenna structures may be disposed generally orthogonal to each other.

25

Advantageously, where two of the first, dual band, antenna structures are provided, they are configured or arranged so as to have mutually opposed or orthogonal polarisations. This is because each antenna structure produces a toroidal or doughnut-shaped radiation pattern. By arranging the antenna structures in this way, 30 the patterns become orthogonal, and therefore good diversity is achieved. Nevertheless, it is to be appreciated that even in this configuration, there is likely still

9

to be a certain degree of coupling, which may not be significantly less than if the two antenna structures were arranged in the same orientation with their longitudinal axes along the same line.

5 The second antenna structure operates at a single frequency, which in some embodiments may be substantially the same as the lower frequency of operation of the first, dual-band, antenna structure. The second antenna structure, however, does not pick up signals of the lower frequency radiated by the first antenna structure that travel around, say, a metallised laptop computer casing on which the antennas are

10 mounted, because these signals are vertically polarised. Furthermore, at the lower frequency, the first antenna structure tends to radiate along the casing in the direction of its longitudinal axis, and another first antenna structure will tend to pick up this signal. Accordingly, the second antenna structure is configured differently from the first so as not to couple with this signal.

15

In one embodiment of the present invention, the first antenna structure is configured as a dual band WLAN (wireless local area network) antenna, and the second antenna structure is configured as a Bluetooth® antenna. The first antenna structure may, for example, operate at around 2.4GHz and around 5GHz, and the second antenna

20 structure may, for example, operate at around 2.4GHz only.

The first antenna structures, where more than one is provided, may be excited by a common feed, such as a branched feed system. The first antenna structures may be mutually arranged in series or in parallel.

25

According to a second aspect of the present invention, there is provided a computing device incorporating the antenna arrangement of the first aspect of the present invention.

30 As previously discussed, where the computing device has a display screen, the antenna arrangement may be disposed around edge regions of the display screen.

10

However, it will be appreciated that the antenna arrangement may be formed in any appropriate part of the computing device.

For a better understanding of the present invention and to show how it may be carried 5 into effect, reference shall now be made by way of example to the accompanying drawings, in which:

FIGURE 1 shows a prior art laptop computer with antennas mounted around a display screen;

10

FIGURE 2 is a plan view of a first embodiment of a first antenna component;

FIGURE 3 is a side elevation of the antenna component of Figure 1;

15 FIGURE 4 is an exploded perspective view of a first embodiment of a second antenna component;

FIGURE 5 is a side elevation of the antenna component of Figure 4;

20 FIGURE 6 is an exploded perspective view of a second embodiment of a second antenna component;

FIGURE 7 is a side elevation of a second embodiment of the first antenna component;

25

FIGURE 8 is a side elevation of a third embodiment of the first antenna component;

FIGURE 9 shows a laptop computer provided with an antenna arrangement of an embodiment of the present invention;

30

11

FIGURE 10 is a schematic of a laptop computer provided with an antenna arrangement of an alternative embodiment of the present invention;

FIGURE 11 is a plot showing Si i return loss of three antenna elements in a 2.4 GHz 5 band plus S12 transmission loss (isolation) between the elements; and

FIGURE 12 is a plot showing Sn return loss of two antenna elements in a 5-6 GHz band plus S12 transmission loss (isolation) between the elements.

10 Figure 1 shows a prior art laptop computer 1 including a hinged metallised cover 2 incorporating a display screen 3. A plurality of antenna components 4 are disposed around edge portions of the screen 3. However, in order to reduce the level of signals induced by one of the antennas in the other antennas mounted on the same computer 1, it would be desirable to avoid the excitation of surface waves which may travel 15 across the conductive structure of the screen 3 and the metallised inner face of the cover 2.

Figures 2 and 3 show an embodiment of the first, dual band, antenna structure of the present invention, in which two antenna components 5, 6 operating in two different 20 frequency bands are grouped together. A substrate of microwave laminate 7, such as a dielectric PCB substrate, is provided with a conductive metallised layer 8, which serves as a groundplane, on one face and a direct microstrip transmission line 9 on an opposed face. First and second ceramic dielectric antennas 5, 6 are mounted on the microstrip transmission line 9 on the opposed face of the substrate 7 so as to be 25 excited thereby when a predetermined electrical signal is fed to the microstrip transmission line 9. The first antenna 5 is dimensioned to operate in an upper frequency band, for example around 5GHz, while the second antenna 6 is dimensioned to operate in a lower frequency band, for example around 2.45 or 2.5GHz. One or more matching components 10, 11 may be placed in series or 30 parallel with the microstrip line 9 to ensure the achievement of a suitable input impedance across the operating frequency band. The antenna is connected to a radio

12

transmitter/receiver (not shown) by a coaxial cable (not shown) which may be attached directly or by means of a conventional coaxial connector 12.

An embodiment of the second, electrically-conductive antenna structure is shown in 5 Figures 4 and 5. This comprises a microwave (e.g. dielectric PCB) substrate 13 having a grounded conductor 14 on its lower face and a microstrip radiator and input line 15 on the opposite face. A connection between a coaxial connector 12 and the radiator 15 may be used to accommodate impedance matching arrangements 16, 17. A layer of dielectric material 18 lies against an upper face of the microstrip radiator 10 15, and a second parasitic radiator comprising a thin metallic sheet 19 is placed against an upper face of the dielectric material 18. The antenna is connected to a radio transmitter/receiver (not shown) by a coaxial cable which may be attached directly or by means of a conventional coaxial connector 12. This antenna is derived from a structure known as a stacked-patch antenna, although in this implementation 15 the aspect ratio of the exciting element and parasitic elements is very different from the conventional patch in which the width and length of these components are typically similar. Because of the extreme aspect ratio, the antenna might also be considered to be a printed or strip dipole.

20 An important property of this second antenna structure that its radiation has a direction of polarisation lying parallel with the groundplane 13, 14. This avoids the generation of surface waves which may propagate across the surface of the screen 3 or the rear of the lid 2 of the computing device 1 (see Figure 1).

25 An alternative form of the second, electrically-conductive antenna component is shown in Figure 6, and comprises a dielectric substrate 20 with a conductive groundplane 21 on its underside and carrying on its topside a feed line 22 with optional matching arrangements 23. A layer of dielectric material 24 is disposed above the feed line 22, and a quarter-wave conductive radiating element 25 is 30 provided on to of the dielectric material 24. The radiating element 25 is connected to the groundplane 21 at one end by means of one or more pins or plated-through holes

13

26. A coaxial connector 12 is also provided. This configuration is derived from a short-circuited quarter-wavelength patch radiator and is physically smaller than the arrangement shown in Figures 4 and 5.

5 An alternative form of the first, dual-band antenna component is shown in Figure 7. In this embodiment a single microwave substrate 27 carries a ceramic antenna 28, fed by a direct microstrip transmission line 29 from a coaxial connector 12. A conductive metal layer or groundplane 35 is provided on an underside of the substrate 27. The ceramic antenna 28 operates in a higher frequency band. A modified patch 10 antenna 30 as already described in relation to Figures 4, 5 and 6 is also provided on the substrate 27, and this antenna 30 operates in a lower frequency band, also being fed by the microstrip transmission line 29. This arrangement operates independently at each frequency band with no requirement for separate filter elements or diplexer.

15 Figure 8 shows an alternative configuration of the first, dual band antenna component of Figure 7 in which the coaxial input connection 12 is made to the microstrip transmission line 29 at a point between two antennas 31 and 32. The electrical length of the transmission line 29 between each antenna 31, 32 and the input connector 12 is preferably chosen to provide a virtual open-circuit condition at the relevant frequency 20 for the antenna 31, 32 which is inoperative in that band. Thus a 2.5GHz antenna 31 presents a virtual open circuit at the input in the 5GHz band and a 5GHz antenna 32 presents a virtual open circuit in the 2.5GHz band. This configuration may be used to combine two ceramic antennas, a ceramic antenna with a half-wave strip dipole or a ceramic antenna with a quarter-wave short-circuit patch.

25

Figure 9 shows a particularly preferred embodiment of the present invention in which a laptop computer 1 with a hinged display screen 2, 3 is provided with dual-band antennas 33 on adjacent sides of the display screen 3 in a top right corner thereof in a mutually orthogonal arrangement. A third antenna 34 for one frequency band, 30 constructed according to Figures 4 and 5, is located on a left hand edge of the display screen 3, this position being chosen as it is remote from the two antennas 33, thus

14

reducing coupling between antennas 33 and 34. The exact relative positions of the antennas 33, 34 are determined by calculation or measurement and are selected to provide the highest attenuation between the individual dual band antennas 33.

5 Figure 10 is a schematic showing a variation of the arrangement in Figure 9, where two dual band WLAN antennas 33 are mounted on edge regions of the display screen 3, this time on the top edge and the left hand edge, and a single Bluetooth® antenna 34 is provided on a right hand edge of the display screen 3. The schematic shows the configuration on which the plots in Figures 11 and 12 are based for the S12, S13 and 10 S23 return losses.

The antenna arrangement of Figure 10 was tested on a copper chassis representing a conductive casing of a modern laptop computer. The S12 isolation between the two WLAN antennas 33 does not need to be better than 15dB to allow good diversity, but 15 the S 13 and S23 between the two WLAN antennas 33 and the Bluetooth® antenna 34 must be better than this if the two protocols (WLAN and Bluetooth®) are to operate simultaneously. In laboratory measurements made in an anechoic chamber for the 2.4 - 2.5 GHz band (between the two vertical lines in Figure 11), the S13 and S23 isolation exceeded -40dB, which is sufficient for this application. The S12 isolation 20 exceeded -15dB. The Sn return losses are also shown in Figure 11.

Only the two WLAN antennas 33 work in the 5 - 6 GHz band. The S12 isolation is better than -25dB across the whole of this band, as can be seen in Figure 12.

25 Antenna arrangements, other than the one shown in Figures 9 and 10, are possible. A key feature leading to the high isolation is a combination of the two types of antenna 33, 34 with the pair of dual band antennas 33 being configured to provide radiation with orthogonal dual polarisation, and the third antenna 34 mounted in such a way as to create maximum mutual attenuation between the antennas 33, 34.

30

15

The preferred features of the invention are applicable to all aspects of the invention and may be used in any possible combination.

Throughout the description and claims of this specification, the words "comprise" 5 and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to (and do not) exclude other components, integers, moieties, additives or steps.

16

Claims

CLAIMS:

1. An antenna arrangement comprising at least first and second antenna structures each having a longitudinal axis, the antenna structures being arranged such 5 that their longitudinal axes are all substantially in a given plane, characterised in that the first antenna structure is a multi-band antenna and in that the second antenna structure is configured to operate with a direction of polarisation parallel to the given plane.

10 2. An arrangement as claimed in claim 1, wherein the antenna structures are generally elongate.

3. An arrangement as claimed in claim 1 or 2, wherein the antenna structures are substantially thin or planar along their longitudinal axes.

15

4. An arrangement as claimed in any preceding claim, wherein the first antenna structure includes a first dielectric antenna component configured to operate at a first frequency.

20 5. An arrangement as claimed in claim 4, wherein the first antenna structure additionally includes a second antenna component configured to operate at a second frequency different from the first frequency.

6. An arrangement as claimed in claim 5, wherein the second antenna 25 component is a dielectric antenna component.

7. An arrangement as claimed in claim 5, wherein the second antenna component is an electrically-conductive antenna component.

30 8. An arrangement as claimed in claim 6 or 7, wherein the first and second antenna components share a common feed.

17

9. An arrangement as claimed in claim 8, wherein the first and second antenna components are fed in series.

5 10. An arrangement as claimed in claim 8, wherein the first and second antenna components are fed in parallel.

11. An arrangement as claimed in claim 5 or any claim depending therefrom, wherein the first antenna component is configured so as substantially not to respond

10 to an input signal at the second frequency, and wherein the second antenna component is configured so as substantially not to respond to an input signal at the first frequency.

12. An arrangement as claimed in claim 11, wherein the first antenna component 15 is configured so as to present substantially a completely reactive impedance or an open circuit to an input signal at the second frequency.

13. An arrangement as claimed in claim 11 or 12, wherein the second antenna component is configured so as to present substantially a completely reactive

20 impedance or an open circuit to an input signal at the first frequency.

14. An arrangement as claimed in claim 7, wherein the second antenna component is configured to be parasitically driven by the first antenna component.

25 15. An arrangement as claimed in any preceding claim, wherein the second antenna structure is an electrically-conductive antenna structure.

16. An arrangement as claimed in any preceding claim, comprising two of the first antenna structures and one of the second antenna structures.

30

18

17. An arrangement as claimed in claim 16, wherein the two first antenna structures are disposed closer to each other than to the second antenna structure.

18. An arrangement as claimed in claim 16 or 17, wherein the two first antenna 5 structures are disposed with their longitudinal axes in a substantially orthogonal configuration.

19. An arrangement as claimed in any one of claims 16 to 18, wherein the two first antenna structures are configured or arranged to operate with mutually opposed

10 or orthogonal polarisations.

20. An arrangement as claimed in claim 7 or any claim depending therefrom, wherein the second antenna structure is a stacked patch antenna structure.

15 21. An arrangement as claimed in claim 7 or any claim depending therefrom, wherein the second antenna structure is a printed or strip dipole antenna structure.

22. An arrangement as claimed in claim 7 or any one of claims 8 to 19 depending from claim 7, wherein the second antenna structure is a short-circuited quarter-

20 wavelength patch radiator antenna structure.

23. An arrangement as claimed in any preceding claim, wherein the first antenna structure is a WLAN antenna.

25 24. An arrangement as claimed in any preceding claim, wherein the second antenna structure is a Bluetooth® antenna.

25. An arrangement as claimed in claim 5 or any claim depending therefrom, wherein the second antenna structure is configured to operate at a frequency 30 substantially equal or similar to the first or second frequency of operation of the first antenna structure.

19

26. An arrangement as claimed in any preceding claim and incorporated in a computing device.

5 27. An arrangement as claimed in claim 26, wherein the computing device has a display screen and the antenna structures are disposed on or about edge portions of the display screen.

28. A computing device incorporating the antenna arrangement of any one of the 10 preceding claims.

29. An antenna arrangement substantially as hereinbefore described with reference to or as shown in Figures 2 to 12 of the accompanying drawings.

15 30. A computing device incorporating an antenna arrangement substantially as hereinbefore described with reference to or as shown in Figures 2 to 12 of the accompanying drawings.

20