WO2010029304A1

WO2010029304A1 - Multifunctional antenna

Info

Publication number: WO2010029304A1
Application number: PCT/GB2009/002174
Authority: WO
Inventors: Peter Hall; Elham Ebrahimi
Original assignee: University of Birmingham
Current assignee: University of Birmingham
Priority date: 2008-09-12
Filing date: 2009-09-10
Publication date: 2010-03-18
Anticipated expiration: 2011-03-12
Also published as: GB0816755D0

Abstract

A multifunctional antenna (12) is disclosed comprising a substrate (28) having a monopole antenna (13) provided on a first side (10) thereof and a microstrip patch antenna (32) provided on an opposite second side (30) thereof. The relative positions of the monopole antenna (13) and the microstrip patch antenna (32) are such that the monopole antenna (13) serves as a ground plane for the microstrip patch antenna (32).

Description

Multifunctional Antenna

Field of the Invention The invention relates to a multifunctional antenna. Particularly, but not exclusively, the invention relates to a multifunctional antenna for use in a portable device such as a mobile phone, personal digital assistant (PDA), radio or laptop.

Background to the Invention There is growing demand for multifunctional devices which are capable of transmitting and/or receiving wireless signals for a number of different applications operating over a number of different frequency bands. For example, mobile phones are often required to operate in different countries where the communication frequencies and standards are different. The phone may also require, GPS, Bluetooth connectivity, and wireless internet access. Traditionally, this means that a number of different antenna are required with corresponding circuitry and this has implications on the size of the device and its styling, both of which are considered by end users as important factors.

Similar considerations also arise in relation to the concept of Cognitive Radio (CR) and in particular Spectrum Sensing Cognitive Radio (SSCR) which aims to provide the user with an improved and more reliable service by making more efficient use of the frequency spectrum. It is envisaged that a CR device would change its communication frequency whenever necessary - for example, to avoid interference and spectrum "traffic jams"; to make better use of the many currently under-utilised licensed frequency bands; to cater for different applications; or to respond to user requirements. A CR would have to co-exist with legacy wireless systems by sharing the same spectrum resources without significantly interfering with them. In order to make informed decisions about the choice of operating frequency the CR must scan the frequency spectrum listening for legacy users and available bandwidth. Although the architecture of CR has not yet been standardised some suggest that an Ultra Wide-Band (UWB) omni-directional antenna could be used for performing the sensing function and a separate narrowband directional antenna, which is capable of being tuned to a selected frequency, could then handle the required communications. However, a particular challenge arises when there is a requirement to simultaneously sense and communicate (i.e. to continuously monitor the spectrum usage in a process which runs in parallel with the communication link). It has therefore been proposed that spectrum sensing and radio re-configuration may only be performed when the communication link quality falls below a pre-defined threshold. In any case, the space available for these antennas and their supporting circuitry will be limited in a portable CR device.

It is therefore an aim of the present invention to provide a multifunctional antenna which helps to address the above-mentioned problems.

Summary of the Invention

According to a first aspect of the present invention there is provided a multifunctional antenna comprising a substrate having a monopole antenna provided on a first side thereof; and a microstrip patch antenna provided on an opposite second side thereof; the relative positions of the monopole antenna and the microstrip patch antenna being such that the monopole antenna serves as a ground plane for the microstrip patch antenna.

The present invention therefore provides a compact multifunctional antenna which comprises both a monopole antenna and a microstrip patch antenna. Accordingly, the antenna can be made to operate in a wideband or an Ultra Wide-Band (UWB) mode when the monopole antenna is activated and to operate over a narrowband of frequencies when the microstrip patch antenna is activated. In particular embodiments, the antenna may be configured to operate simultaneously in both the UWB and narrowband modes of operation. Accordingly, the sensing and communicating functions of a CR could be performed simultaneously with the present antenna.

The fact that a compact antenna structure is provided, which is capable of operation in at least two different modes of operation, means that the overall size of a device incorporating the antenna can be reduced since there is no need for separate antennas to perform each function. It will be understood that the term Ultra Wide-Band (UWB) is used throughout to denote a relatively large frequency range and is not limited to a specific range of frequencies such as those defined as UWB by the US Federal Communications Commission (FCC).

The monopole antenna may comprise a planar radiating patch. The shape of the radiating patch of the monopole antenna is not particularly limited and may be, for example, square, rectangular, triangular, circular, elliptical, annular, star-shaped or irregular. Furthermore, the radiating patch may include at least one notch, slot or parasitic element. It will be understood that the shape and configuration of the monopole antenna will depend upon the desired characteristics of the antenna for the application in question.

Similarly, the size and shape of the microstrip patch antenna may be varied to provide the optimum characteristics for the narrowband mode of operation. Accordingly, the microstrip patch antenna may be, for example, square, rectangular, triangular, circular, elliptical, annular, star-shaped or irregular. Furthermore, the microstrip patch antenna may include at least one notch, slot or parasitic element. Optionally, the microstrip patch antenna may be electrically connected (i.e. shorted) to the monopole antenna. More specifically, the microstrip patch antenna may be configured as an Inverted-L

Antenna (ILA), an Inverted-F Antenna (IFA) or a Planar Inverted-F Antenna (PIFA).

As above, it will be understood that the shape and configuration of the microstrip patch antenna will depend upon the desired characteristics of the antenna for the application in question.

In a particular embodiment, the monopole antenna is generally wine-glass shaped with a rounded base section and a rectangular top section. The rounded base section may be part-circular or part-elliptical.

A first transmission line may be coupled to the monopole antenna to link the monopole antenna to a transmitter and/or receiver circuit. A second transmission line may be coupled to the microstrip patch antenna to link the microstrip patch antenna to a transmitter and/or receiver circuit.

The first and/or second transmission line may be constituted by a microstrip comprising a conducting strip on the first side of the substrate and a transmission line ground plane provided on the second side of the substrate, opposite to the conducting strip. The conducting strip may be tapered to alter the impedance of the first and/or second transmission line.

Alternatively, the first and/or second transmission line may be constituted by a coplanar waveguide (CPW) comprising a conductor having a transmission line ground plane on either side thereof, each spaced from the conductor by a pre-determined gap. Accordingly, in the case of a CPW, all of the components of the first and/or second transmission line are provided on the same side of the substrate.

In either of the above embodiments, the shape and configuration of the first and/or second transmission line may vary to provide the required impedance characteristics.

Furthermore, the first and/or second transmission line may be coupled, respectively, to the monopole antenna and/or the microstrip patch antenna along an edge thereof and may be disposed centrally along the edge or offset to one side. Alternatively, the first and/or second transmission line may be coupled, respectively, to the monopole antenna and/or the microstrip patch antenna at a corner thereof.

The transmission line ground plane may also serve as a ground plane for the monopole antenna.

It will be understood that, since the ground plane in a monopole antenna serves as an impedance matching circuit, the dimensions of the ground plane (that is the transmission line ground plane, as defined above) and the feed gap provided between the lower surface of the radiating patch and the top surface of the ground plane affect the operating bandwidth. A plurality of microstrip patch antennas may be provided and arranged so that the monopole antenna serves as a ground plane for each of them. More specifically, the radiating patch of the monopole antenna may serve as a ground plane for the/each microstrip patch antenna.

A switching means may be provided for selectively activating (i.e. feeding) one or both of the monopole antenna and the microstrip patch antenna.

It will be understood that when the monopole antenna is activated multiple resonances will be permitted giving rise to wideband or UWB operation. However, when the microstrip patch antenna is activated only a single mode of resonance will be supported and, as such, the antenna will operate in a narrowband of frequencies.

The multifunctional antenna may be configured to be switchable from one mode of operation, suitable for one application, to another mode of operation, suitable for another application. Some possible applications for the UWB antenna include broadband wireless internet, spectrum scanning in cognitive radios, and wireless USB (i.e. the streaming of high bandwidth data from one device to another). Applications for the narrowband antenna would include any form of narrowband communication, such as wireless LAN and GSM, and the communications function within a cognitive radio system.

It will be understood that optimisation of any particular design of the multifunctional antenna will need to take into account the return loss performance of the device both when the monopole antenna is activated and when the microstrip patch antenna is activated.

For UWB operation, in order to ensure that the antenna yields a good impedance match over the desired range of operating frequencies, it will be necessary to adjust the length and width of the transmission ground plane together with the gap between the transmission ground plane and the monopole antenna (i.e. the radiating patch). It will be understood that the dimensions and the lateral position of the monopole antenna relative to the microstrip patch antenna can significantly alter the performance of the antenna under the narrowband mode of operation.

A parametric study may be undertaken to evaluate the optimum construction of a particular multifunctional antenna according to an embodiment of the present invention.

Brief Description of the Drawings Certain embodiments of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 illustrates a view of the top layer of a multifunctional antenna according to a first embodiment of the present invention, as printed onto a substrate;

Figure 2 illustrates a view of the bottom layer of the multifunctional antenna shown in Figure 1, as printed onto the substrate, with the structure provided on the top layer illustrated in dashed lines;

Figure 3 shows a graph of both measured and simulated return loss against frequency for the antenna shown in Figures 1 and 2, when operating in UWB mode;

Figure 4 shows a graph of both measured and simulated return loss against frequency for the antenna shown in Figures 1 and 2, when operating in narrowband mode;

Figure 5A illustrates some alternative shapes for the monopole antenna shown in Figure

1 , wherein the radiating patch is a polygon which is fed from one of its straight edges;

Figure 5B illustrates some alternative shapes for the monopole antenna shown in Figure

1, wherein the radiating patch is a polygon which is fed from one of its corners; Figure 5C illustrates some alternative shapes for the monopole antenna shown in Figure

1, wherein the radiating patch is circular or elliptical;

Figure 5D illustrates some alternative shapes for the monopole antenna shown in Figure

1 , wherein the radiating patch is a polygon incorporating a notch therein;

Figure 5E illustrates some alternative shapes for the monopole antenna shown in Figure 1 , wherein the radiating patch incorporates cut outs;

Figure 5 F illustrates some alternative shapes for the monopole antenna shown in Figure

1 , wherein the radiating patch incorporates additional stubs or parasitic elements; Figure 6A illustrates some alternative shapes for the monopole antenna shown in Figure

1, wherein the ground plane incorporates notches, slots and slits;

Figure 6B illustrates some alternative shapes for the monopole antenna shown in Figure

1, wherein the ground plane incorporates bevels; Figure 6C illustrates some alternative shapes for the monopole antenna shown in Figure

1 , wherein the ground plane incorporates cut outs and bevels at the feed point;

Figure 7 A illustrates some alternative shapes for the monopole antenna shown in Figure

1 , wherein the radiating patch is fed asymmetrically;

Figure 7B illustrates some alternative shapes for the monopole antenna shown in Figure 1 , wherein the radiating patch is fed through multiple points;

Figure 8A illustrates some alternative shapes for the microstrip patch antenna shown in

Figure 2, wherein the radiating patch is a simple geometric shape;

Figure 8B illustrates some alternative shapes for the microstrip patch antenna shown in

Figure 1, wherein the radiating patch is a complex geometric shape; Figure 9 illustrates some alternative shapes for the microstrip patch antenna shown in

Figure 2, wherein different feed mechanisms are employed;

Figure 10 illustrates some alternative shapes for the microstrip patch antenna shown in

Figure 2, wherein further feed mechanisms are employed;

Figure 11 illustrates an alternative configuration for the microstrip patch antenna shown in Figure 2, namely a Planar Inverted-F Antenna (PIFA) structure;

Figure 12 illustrates some alternative shapes for the planar surface of the PIFA structure shown in Figure 11 ;

Figure 13 illustrates a view similar to that of Figure 2 but with the microstrip patch antenna rotated 90 degrees with respect to the monopole antenna; and Figure 14 illustrates similar to that of Figure 2 but with the microstrip patch antenna rotated 180 degrees with respect to the monopole antenna.

Detailed Description of Certain Embodiments

With reference to Figure 1, there is illustrated a top layer 10 of a multifunctional antenna 12 according to a first embodiment of the present invention. The top layer 10 comprises a monopole antenna 13 in the form of a radiating patch 14 which is fed at the centre of its base 16 by a coplanar waveguide (CPW) 18. The CPW 18 comprises a central conductor 20 having a section of ground plane 22 on either side thereof.

In this particular embodiment, the patch 14 is wine-glass shaped with a rectangular top section 24 and a half-elliptical bottom section 26. The semi-major axis, r_a, and semi- minor axis, r_b, of the half-elliptical bottom section 26, are 15 mm and 8 mm, respectively.

The conductor 20 has width W_f of 4mm and each section of ground plane 22 is spaced from the conductor 20 by a gap g_f of 0.33mm. The CPW 18 is therefore arranged to provide a 50Ω impedance to the patch 14. A feed gap g is provided between the base 16 of the patch 14 and each section of ground plane 22. Since the ground plane in a monopole antenna serves as an impedance matching circuit, the dimensions of each section of ground plane 22 and the feed gap g affect the operating bandwidth of the antenna 13. Thus, to achieve a good impedance matching, the feed gap g is set at 0.3 mm, the length L of each section of ground plane 22 is set at 10 mm, and the width W from the far end of one section of ground plane 22 to the far end of the other section of ground plane 22 is 54 mm.

The monopole antenna 13 is printed onto a dielectric substrate 28. In this embodiment, the substrate 28 is a Taconic TLC laminate with a relative permittivity ε_r of 3+/-0.05 and a thickness h of 0.79mm.

The monopole antenna 13 has been demonstrated to operate in an UWB of frequencies from approximately 3 to 11 GHz, as will be described in more detail below.

Figure 2 shows the bottom layer 30 of the multifunctional antenna 12 shown in Figure 1, with the structure provided on the top layer 10 illustrated in dashed lines. A microstrip patch antenna 32 is printed onto the bottom layer 30 and comprises a rectangular patch 34 which is fed by a tapered microstrip transmission line 36. The rectangular patch 34 is disposed above the radiating patch 14 of the monopole antenna 13 such that the monopole antenna 13 serves as the ground plane for the microstrip patch antenna 32. More specifically, the rectangular patch 34 is positioned generally above the right-hand side of the half-elliptical bottom section 26 (when viewed from the bottom layer 30) and extends a short distance upwardly into the rectangular top section 24. As can be seen from Figure 2, the rectangular patch 34 is surrounded on all sides by the radiating patch 14. Furthermore, the rectangular patch 34 of the present embodiment has a width W_patch of 5 mm and a length L_pat_Ch of 8 mm.

The rectangular patch 34 is electrically connected to the radiating patch 14 by a shorting pin 38. The shorting pin 38 is positioned adjacent the base 40 of the rectangular patch 34, a short distance in from the left-hand edge 42.

The tapered microstrip transmission line 36 is arranged to feed the rectangular patch 34 at the far right-hand edge 44 of the base 40. A taper 46 transforms the tapered microstrip transmission line 36 from a 50Ω line above the base of the section of ground plane 22 to a 100Ω line above the top of the section of ground plane 22.

The Applicants have found that the microstrip patch antenna 32 can operate well as a narrowband antenna within the 802.1 1a WLAN band (5.15-5.825GHz). However, it will be understood that the performance of the microstrip patch antenna 32 can be affected by altering the size of the rectangular patch 34, the position of the shorting pin 38, the position of the rectangular patch 34 relative to the monopole antenna 13 and the position of the tapered microstrip transmission line 36.

In order to verify the performance of the above multifunctional antenna 12, a prototype was fabricated and the results of a series of measurements on this device are shown in Figures 3 and 4 alongside simulated results obtained using a transient solver in CST Microwave Studio which employed The Finite Integration Method.

From each of these graphs it can be seen that the multifunctional antenna 12 performs well in both the UWB and narrowband mode. There is also a reasonable standard of agreement between the results obtained through measurement and simulation and it is believed that any discrepancies between the results are largely due to fabrication errors.

More specifically, it can be seen from Figure 3 that when the monopole antenna 13 is operated, the device exhibits a good return loss over a UWB range of frequencies from approximately 3 to 11 GHz. Moreover, the measured return loss agrees well with the simulated return loss in the frequency range 3 GHz to 5.5 GHz. At frequencies higher than 5.5 GHz it is shown that the simulated return loss remains close to -10 dB. However, the measured return loss shows that a second resonance (not predicted in simulation) appears at 6.7 GHz. Above 6.7 GHz the measured and simulated results deviate by almost 5 dB in some places and the Applicants believe that this discrepancy may be attributed to the effect of using only relatively small (10 mm long) sections of ground plane 22.

Figure 4 shows the results when the microstrip patch antenna 32 is operated and the device serves as a narrowband antenna at approximately 5.55GHz. The measured results generally show a good agreement with the simulated results. However, the measured results do show a wider -10 dB bandwidth in comparison with the simulated results and the Applicants believe this discrepancy may be due to the characteristics of the substrate employed and the tolerances in the manufacturing process.

From the above results it is clear that monopole antenna 13 operates well over a UWB range of frequencies and the microstrip patch antenna 32 operates well within the 802.1 Ia WLAN band. Accordingly, embodiments of the present invention can provide a combined UWB and narrowband antenna in a compact configuration, for use in mobile phone and Cognitive Radio (CR) applications, amongst others. In the case of CR applications, the UWB antenna could fulfil the scanning or sensing task and the narrowband antenna could perform the required communications.

Although in the above described embodiment, the (UWB) monopole antenna 13 comprised a printed wine-glass shaped radiating patch 14 fed by a CPW 18, other designs of monopole antenna 13 could be employed. For example, different shapes of radiating patch 14 can be used and these can either be CPW or microstrip fed.

It is noted that in printed monopole antennas the currents are mainly distributed on the upper edge of the ground plane and the lower edge of the radiating patch. Accordingly, the shape of the radiating patch at the feed point, the dimensions of the ground plane and the gap between the ground plane and the feed point will influence the performance of the antenna. The ground plane should therefore be considered part of the matching circuit since varying the feeding arrangement can affect the input impedance and therefore allow the operating bandwidth to be tuned.

The lower end of the UWB frequency band is mainly influenced by the dimensions of the radiating patch. Bevelling the bottom edge of the radiating patch has been demonstrated to significantly increase the range of the upper end of the UWB. The optimization of the shape of the radiating patch, especially the shape of the bottom portion of the radiating patch, improves the impedance bandwidth by achieving a smooth impedance transition. Furthermore, the shape of the bottom portion of the radiating patch is important for controlling the capacitive coupling with the ground plane. Re-shaping of the bottom portion of the radiating patch can strongly affect the current path.

Figures 5A to 5f show several classes of typical UWB planar monopole antennas. Thus, the radiating patch can be a polygon fed either from one of its straight edges (Figure 5A) or from one of its corners (Figure 5B). In order to enhance the performance of the antenna the radiating patch may have a smooth bottom (Figure 5C), include bevels or notches (Figure 5D), include different cut outs (Figure 5E), or have added stubs or parasitic elements (Figure 5F). It will be understood that combinations and derivations of all of the mentioned options could be employed for good impedance matching.

Since the ground plane in printed monopole antennas forms a part of the matching system, there could be various modifications in the configuration of the ground plane as shown in Figures 6A to 6C. Thus, the ground plane may include notches, slots and slits (Figure 6A), bevels (Figure 6B) and cut outs or bevels at the feed point (Figure 6C).

As a part of the matching network for monopole antennas, the feeding configuration has a considerable affect on the impedance matching. Several feeding arrangements are illustrated in Figures 7 A and 7B. Thus, the radiating patch can be fed asymmetrically, or be connected to the ground plane via a shorting pin as shown in Figure 7A. In order to control the current distribution on the radiating patch, it can be fed through multiple points either by having multiple feed lines or by having a fork shaped feed line, examples of both these arrangements are depicted in Figure 7B.

Further structures for the monopole antenna may be realized by combining the above mentioned design features or by changing between CPW and microstrip feed arrangements.

In embodiments of the present invention a UWB monopole antenna serves as the ground plane for a narrowband microstrip patch antenna. Consequently, less space is required for these two antenna structures than would normally be required in order to be able to switch between these two states of operation (i.e. UWB and narrowband).

The multifunctional antenna may be configured to operate in both UWB and narrowband modes simultaneously by having two separate input ports, one for each antenna.

Since, in the above-described embodiment, the UWB antenna 13 is a CPW fed monopole it can be considered as a defected ground plane for the narrowband antenna 32. This results in more complicated couplings between the UWB and narrowband antenna. In particular, the rectangular patch 34 of the narrowband antenna 32 is fed by a transmission line 36 having a defected ground plane since there is a taper-shaped slot 50 underneath the transmission line 36. The Applicants have shown that the taper- shaped slot 50 in the ground plane contributes to the matching circuit for the narrowband antenna 32. The Applicants have also shown that the dimensions and the lateral position of the rectangular patch 34 relative to the UWB antenna 13 and the shorting pin 38 have considerable effects on the resonant frequency of the narrowband antenna 32. This is thought to be due to the alteration of the current distributions caused by the presence of the UWB antenna 13 compared to a conventional shorted patch antenna.

The structure of the narrowband antenna 32 can be chosen from a wide range of possible structures which comprise printed microstrip patches of different shapes and dimensions, either with or without shorting pins.

A large amount of work has been performed on microstrip patch antennas over the past 25 years; however, all of these are derivations of a generic microstrip patch antenna which comprises a microstrip patch on one side of a substrate, a ground plane on the opposite side of the substrate and a feed line coupled to the microstrip patch. The principal geometric shapes employed in microstrip patch antennas are shown in Figure 8A and possible variants on these shapes are shown in Figure 8B.

The main feeding techniques for a microstrip patch antenna are depicted in Figures 9 and 10. It will be understood that different patch shapes and feeding arrangements can be combined to produce a large number of possible microstrip patch antenna designs.

Microstrip patch antennas can be short-circuited along the null voltage plane (i.e. through the substrate) to form a shorted microstrip patch antenna. Figure 7 shows a principal structure of such an antenna, which is categorized as a Planar Inverted-F Antenna (PIFA). The PIFA is widely used in wireless devices such as mobile handsets. In a similar way to UWB and patch antennas, PIFAs can also have different shapes and feeding arrangements. Moreover, in PIFAs the position and number of shorting pins increases the variety of the design possibilities. In response to the demand of multiple band services there are countless PIFA designs with several slots and slits and different numbers of shorting pins in different positions. Some of the possible designs are depicted in Figure 12. Adding parasitic elements to the patch could be another derivation of a PIFA design. The above mentioned designing methods both for wideband and narrowband antennas mainly cover the possible choices of individual antennas employed. However, there are also a variety of possibilities in how to combine the two antennas. Accordingly, the microstrip patch antenna 32 may be rotated by 90 degrees with respect to the monopole antenna 13, as shown in Figure 13 or it may be rotated by 180 degrees with respect to the monopole antenna 13, as shown in Figure 14.

When designing a multifunctional antenna according to an embodiment of the present invention it is important to try to achieve a good standard of return loss performance under both the narrowband and UWB mode of operation. Thus, after making a significant change to improve performance in the narrowband mode of operation, for example, the designer should switch to the UWB mode and check that the change does not have a detrimental effect there. Conversely, after making a change which improves the UWB operation he/she should check that the narrowband performance remains acceptable.

In designing the above multifunctional antenna, the relative locations of the various elements that comprise the antenna were carefully adjusted in order to optimise the return loss performance in both modes of operation and this was achieved through a parametric study.

A particular advantage of embodiments of the present invention is that they provide a multifunctional antenna which can operate in two or more bandwidths and which does not take up an excessive amount of space. Accordingly, these factors should be taken into account when optimising the antenna design.

The proposed multifunctional antenna combines two different antennas mainly for applications in which there is a need for multiple frequency and bandwidth operation. One possible application is in Cognitive Radio (CR) networks in which the radio reconfigures its characteristics according to changes in the radio background so as to efficiently exploit the radio spectrum. To access the spectrum dynamically there would be a need for a wideband (i.e. UWB) antenna to sense/scan the environment and select the best frequency range (in terms of power and interference) for transmission. The communication could then be carried out by a narrowband antenna operating within the selected frequency range.

It will be appreciated by persons skilled in the art that various modifications may be made to the above-described embodiments without departing from the scope of the present invention.

Claims

Claims:

1. A multifunctional antenna comprising a substrate having a monopole antenna provided on a first side thereof; and a microstrip patch antenna provided on an opposite second side thereof; the relative positions of the monopole antenna and the microstrip patch antenna being such that the monopole antenna serves as a ground plane for the microstrip patch antenna.

2. The multifunctional antenna according to claim 1 wherein the monopole antenna comprises a planar radiating patch.

3. The multifunctional antenna according to claim 2 wherein the radiating patch is square, rectangular, triangular, circular, elliptical, annular, star-shaped or irregular.

4. The multifunctional antenna according to claim 2 or 3 wherein the radiating patch includes at least one notch, slot or parasitic element.

5. The multifunctional antenna according to any preceding claim wherein the microstrip patch antenna is operable over a narrowband range of frequencies.

6. The multifunctional antenna according to any preceding claim wherein the microstrip patch antenna is square, rectangular, triangular, circular, elliptical, annular, star-shaped or irregular.

7. The multifunctional antenna according to any preceding claim wherein the microstrip patch antenna includes at least one notch, slot or parasitic element.

8. The multifunctional antenna according to any preceding claim wherein the microstrip patch antenna is electrically connected to the monopole antenna.

9. The multifunctional antenna according to any preceding claim wherein the microstrip patch antenna is configured as an Inverted-L Antenna, an Inverted-F Antenna or a Planar Inverted-F Antenna.

10. The multifunctional antenna according to any preceding claim wherein the monopole antenna is generally wine-glass shaped with a rounded base section and a rectangular top section.

11. The multifunctional antenna according to claim 10 wherein the rounded base section is part-circular or part-elliptical.

12. The multifunctional antenna according to any preceding claim wherein a first transmission line is coupled to the monopole antenna to link the monopole antenna to a transmitter and/or receiver circuit.

13. The multifunctional antenna according to any preceding claim wherein a second transmission line is coupled to the microstrip patch antenna to link the microstrip patch antenna to a transmitter and/or receiver circuit.

14. The multifunctional antenna according to claim 12 or 13 wherein the first and/or second transmission line may be constituted by a microstrip comprising a conducting strip on the first side of the substrate and a transmission line ground plane provided on the second side of the substrate, opposite to the conducting strip.

15. The multifunctional antenna according to claim 14 wherein the conducting strip is tapered to alter the impedance of the first and/or second transmission line.

16. The multifunctional antenna according to claim 12 or 13 wherein the first and/or second transmission line is constituted by a coplanar waveguide comprising a conductor having a transmission line ground plane on either side thereof, each spaced from the conductor by a pre-determined gap.

17. The multifunctional antenna according to any of claims 12 to 16 wherein the first and/or second transmission line is coupled, respectively, to the monopole antenna and/or the microstrip patch antenna along an edge thereof and is disposed centrally along the edge or offset to one side.

18. The multifunctional antenna according to any of claims 12 to 16 wherein the first and/or second transmission line is coupled, respectively, to the monopole antenna and/or the microstrip patch antenna at a corner thereof.

19. The multifunctional antenna according to any of claims 14 to 16 wherein the transmission line ground plane serves as a ground plane for the monopole antenna.

20. The multifunctional antenna according to any preceding claim wherein a plurality of microstrip patch antennas are provided and arranged so that the monopole antenna serves as a ground plane for each of them.

21. The multifunctional antenna according to claim 20 wherein the radiating patch of the monopole antenna serves as a ground plane for each microstrip patch antenna.

22. The multifunctional antenna according to any preceding claim wherein a switching means is provided for selectively activating one or both of the monopole antenna and the microstrip patch antenna.

23. A multifunctional antenna as hereinbefore described with reference to and/or as shown in the accompanying drawings.

24. A wireless device including a multifunctional antenna according to any preceding claim.