GB2366081A

GB2366081A - Radiation-efficient portable radio antenna which adapts to conditions

Info

Publication number: GB2366081A
Application number: GB0019648A
Authority: GB
Inventors: Ovadia Grossman; Moshe Ben-Ayun; Mark Rozental; Arieh Vered
Original assignee: Motorola Israel Ltd
Current assignee: Motorola Solutions Israel Ltd
Priority date: 2000-08-09
Filing date: 2000-08-09
Publication date: 2002-02-27
Also published as: GB0019648D0

Abstract

A wireless communications unit (10) having a radiating element (12) operably coupled to a processor (54) that reconfigures the radiating element (12) depending upon a mode of operation of the wireless communications unit (10) wherein the mode of operation of the wireless communications unit (10) is determined by a spatial operating environment of the wireless communications unit (10). This provides the advantages of significantly improving antenna efficiency when the wireless communications unit is participating in a communication. A radiating element (12) comprising a coil (14) operably coupled to a conducting cylinder (16) with said conducting cylinder (16) positioned substantially adjacent to the coil (14) is provided. Additionally, a method of operating a wireless communications unit (10) comprising a radiating element (12) operably coupled to a processor (54) is provided. The method having the steps of determining a spatial operating environment of the wireless communications unit (10) and/or a mode of operation of the wireless communications unit (10); and reconfiguring the operation of the radiating element (12) depending upon said determination.

Description

<Desc/Clms Page number 1> ADAPTIVE RADIATION-EFFICIENT PORTABLE RADIO ANTENNA Field of the Invention This invention relates to antennas, and in particular antennas for use in wireless communication products such as cellular telephones or mobile radios.

Background of the Invention In the field of this invention it is known to use antennas to radiate electromagnetic signals. Antennas are basic components of any electronic system that requires free space as a propagation medium.

An antenna is a device that provides a means for radiating or receiving radio waves. It is a transducer between, say, a guided electromagnetic wave and an electromagnetic wave propagating in free space. In a communications link, a transmitter circuit of a first communications device is connected through a coaxial cable, a microstrip transmission line or other such means to an antenna, the signal is radiated in free space to another antenna, and then passes through another coaxial cable, a microstrip transmission line or other similar structure to a receiver circuit of a second communications device. A 50ohm characteristic impedance is usually taken as standard for such links to/from antennas, although domestic cables use, however, a 75ohm characteristic impedance.

Notwithstanding the considerable differences in physical realisation of antennas for different frequencies and

purposes, there are certain basic properties that define the function and operation of an antenna. The properties most often of interest in the design of an antenna are: radiation pattern, antenna gain, polarisation and impedance. For a linear, passive antenna, these properties are identical for the transmitting operation and the receiving operation of the antenna, by virtue of the reciprocity theorem as known to those skilled in the art.

The radiation pattern of an antenna determines the spatial distribution of the radiated energy. For example, a vertical wire antenna gives uniform coverage in the horizontal (azimuth) plane, with some vertical directionality, and as such is often used for broadcasting purposes.

As an alternative to a radiation pattern providing a uniform coverage an antenna, and therefore the corresponding radiation pattern, can be made directional. The directional properties of antennas are frequently expressed in terms of a gain function. The gain of an antenna is defined as the ratio of the maximum radiation intensity from the antenna to the maximum from a reference antenna having the same input power. The reference antenna for this purpose is usually a hypothetical loss-less isotropic radiator and the gain is subsequently expressed in dBi (dB level with reference to an isotropic radiator - described later).

At a distance `r' from an isotropic (ideal, uniform- distribution) antenna, the radiated power is spread evenly over a spherical surface of area 4nr2. For an antenna with gain, it follows that the power incident on

an area `A', at a distance `r' in the direction of the most intense radiation is: P = G* Pt*A/ (47cr2) (1) where Pt is the transmit power and G is the gain. However, realisable antennas are never "ideal" and some loss of signal throughput occurs. In such a case, the fraction of power reflected by a non-ideal antenna is: prefl/pinc - IF I 2

where Zin is the antenna input impedance, Zo the line impedance and I' is the voltage reflection coefficient. Zin is a function of frequency, and its variation with frequency, or that of II'I, is usually the parameter, together with the voltage standing wave ratio (VSWR) of the antenna, that is determined to assess the efficiency of the antenna.

For many directional antennas, the important properties of the radiation pattern are the beam-width and the level of the side-lobes, in planes passing through the beam maximum. The beam-width in a particular plane is defined by the angular width of the pattern at a level that is 3dB down from the beam maximum. The side-lobe level is specified with reference to the maximum of the main beam and is generally expressed in dB down from this level.

In the design of wireless communications products, the efficiency of the antenna operation is a critical factor, namely the ability to transfer power input to an antenna into a radiated free-space signal, or receive a free- space signal and convert that received signal to a received input power for a receiver circuit, with minimal loss.

It is known that such radiated signals can be easily absorbed into objects, thereby effectively disturbing/ reducing the radiated (or received) power of the antenna. Consequently the operating efficiency of the antenna is reduced. Absorbent objects generally disturb antenna radiation pattern when positioned near to the antenna, and if placed in close proximity to the antenna can cause the gain of the antenna to be reduced by as much as 15- 25.dB One solution to limit absorbency of a radiated signal would be to use directional antennas. A technique to achieve this is to make a directional radiation pattern with a shallow null toward the absorbent article. However, this leads to uneven distribution of the radiated pattern. As a general principle, highly directional antennas also require antenna dimensions of many wavelengths. Such dimensions are clearly unsightly, cumbersome and currently inappropriate for wireless communications units operating at very high frequencies (VHF) or ultra high frequencies (UHF).

As indicated, the performance of a portable communications unit, in terms of available range and power output, is significantly reduced when the antenna

is brought in close proximity to an absorb6,nt (or sometimes reflective) article. The article absorbs the radiated power causing the coverage range of the radiated signal to be decreased. Consequently, the transmit power of the wireless communications unit needs to be increased to achieve the same coverage area as a non-absorbed signal.

The reason for this is that an antenna is typically optimised to operate in free space. It is possible to use other antennas that have a much weaker interaction with the absorbent articles and thereby perform better near such articles. However their performance is generally poor in a free space environment, where communications units predominantly spend most of their time in a receiving or scanning mode of operation.

A prior art arrangement that could address these alternative operating requirements is to switch between two distinct antennas. Such a solution is costly and consumes a lot of space as it requires two external antennas. In reality, the solution generally employed, at least in current cellular and mobile communications fields, has been to design systems with a very dense population of base stations to compensate for such absorbencies and propagation losses. Clearly, this solution significantly increases the cost of deploying a communications technology.

Nowadays there are many regulatory authorities that set stringent limits for radiated signals. As such, the majority of cellular phones and mobile radios have to attain certain levels of antenna performance. Taking into account system antenna requirements, a highly

efficient antenna applied to a specific cellular phone or mobile radio can provide a significant marketing advantage for the cellular phone or mobile radio manufacturer.

Thus, a need exists to provide a high radiation-efficient portable radio antenna, particularly when a wireless communications unit transfers from an idle mode into a communicating mode of operation, where at least some of the aforementioned disadvantages may be alleviated. Sununary of the Invention In accordance with a first aspect of the preferred embodiment of the present invention, a wireless communications unit is provided. The wireless communications unit is characterised by a radiating element operably coupled to a processor that reconfigures the radiating element depending upon a mode of operation of the wireless communications unit wherein the mode of operation of the wireless communications unit is determined by a spatial operating environment of the wireless communications unit.

In this manner, by determining a spatial operating environment of the wireless communications unit the radiating element can be reconfigured and its performance thereby optimised according to the determined spatial operating environment In the preferred embodiment of the invention, the wireless communications unit includes switching means

operably coupled to the processor and the radiating element for effecting the reconfiguration of the radiating element under direction from the processor, in response to said determination. Preferably, the determination is accomplished by performance measurement means operably coupled to the processor and the radiating element for determining the spatial operating environment of the wireless communications unit.

In the preferred embodiment of the invention, the performance measurement means include a forward path and a feedback path to determine power levels of signals transmitted to and received from the radiating element. The determination indicates the spatial operating environment of the wireless communications unit, and in particular whether the wireless communications unit is operating in the vicinity of an absorbent structure. Preferably, the reconfiguration of the radiating element is performed by coupling the radiating element to a second radiating element when the wireless communications unit is operating in the vicinity of an absorbent structure.

In the preferred embodiment of the invention, the second radiating element portion of the reconfigured radiating element is a substantial ground plane comprising a shielded printed circuit board or the chassis of the wireless communications unit, which is fed by a transmission line.

In this manner, and advantageously, the current distribution of the antenna is more evenly spread out across the communications unit, thereby reducing the

disturbance effect of any absorbent article in the vicinity of the antenna.

In a second aspect of the preferred embodiment of the present invention, a radiating element, preferably a coil-based antenna is provided. The radiating element includes a coil operably coupled to a conducting cylinder with said conducting cylinder positioned substantially adjacent to the coil.

In this manner, and advantageously, the conducting cylinder slightly detunes or reduces the Q of the coil to improve bandwidth.

Preferably, the conducting cylinder is operably coupled to the coil without having a galvanic connection with the coil. In the preferred embodiment, the coil of the radiating element is slightly de-tuned to increase the bandwidth of the radiating element and/or the stability of any wireless communications unit connected thereto. The radiating element is reconfigurable to be operably coupled to a second radiating element, preferably a grounded printed circuit board or chassis of a wireless communication unit, with the conducting cylinder and the transmission line being used as a feeder for the second radiating element.

In a third aspect of the preferred embodiment of the present invention, an antenna switching arrangement is provided.

In a fourth aspect of the preferred embodiment of the present invention, a method of operating a wireless communications unit is provided. The wireless

communications unit includes a radiating element operably coupled to a processor. The method is characterised by the steps of determining a spatial operating environment of the wireless communications unit and/or a mode of operation of the wireless communications unit; and reconfiguring the operation of the radiating element depending upon said determination.

Exemplary embodiments of the present invention will now be described, with reference to the accompanying drawings, in which: FIG. 1 shows an antenna coupled to a wireless communications unit arrangement in accordance with a preferred embodiment of the present invention; FIG. 2 shows a wireless communications unit adapted to support the various inventive concepts of a preferred embodiment of the present invention, the figure particularly illustrating the antenna switching operation.

FIG. 3 shows a typical prior art antenna vertical- polarisation radiation pattern with the antenna positioned near an absorbent article.

FIG. 4 shows a typical prior art antenna vertical- polarisation radiation pattern with the antenna being positioned at a handheld distance away from an absorbent article.

FIG. 5 shows an antenna vertical-polarisation radiation pattern in accordance with the antenna arrangement of a

preferred embodiment of the invention, with the antenna being positioned near an absorbent article.

FIG. 6 shows an antenna vertical-polarisation radiation pattern in accordance with the antenna arrangement of a preferred embodiment of the invention, with the antenna being positioned at a handheld distance away from an absorbent article.

Description of Preferred Embodiment(s) An antenna.coupled to a wireless communications unit 10, for example a cellular phone, is shown in FIG. 1 in accordance with a preferred embodiment of the present invention. The wireless communications unit 10 includes an antenna 12 preferably a regular coil antenna having a coil portion 14 and a conducting cylinder 16 positioned over the coil portion 14. It is worth noting that in the preferred embodiment of the invention the conducting cylinder 16 does not have galvanic connection with the coil portion 14.

The cylinder is interacting with the coil capacitively and inductively, and transforms the covered part of the coil into a special case of a transmission line. If the cylinder is floating and not connected galvanically, it can be described as a weak transformer which slightly detunes the coil, but leaves it operating at the same frequency.

The coil portion 14 is distinguished over prior art coil antenna arrangements due to the coil portion 14

being arranged to slightly detune the antehna's performance, thereby increasing the bandwidth of the antenna and/or the stability of the antenna coupling arrangement when positioned near an absorbent article. The conducting cylinder 16 is further used as a feeder structure for the transmission line antenna. The coil contains the power that is coupled via the cylinder to the transmission line.

The conducting cylinder 16 further distinguishes the antenna arrangement of the present invention over prior art antenna arrangements. The conducting cylinder 16 is operably connected to transmission line 18 via an antenna mode switch 24. The antenna 12 may use a fully shielded printed circuit board (PCB) 20 or the internal chassis 22 of the wireless communications unit as a ground plane. When the antenna mode switch 24 is open, the antenna operation performs substantially as normal, where the transmit signal predominantly radiates from the coil portion 14. It is possible that, given the dual-mode arrangement of the preferred embodiment of the invention, the operation of the antenna in the first `open switch' mode of operation may be a little detuned, due to the configuration of the coil portion 14.

When the antenna mode switch 24 is in a `closed' position, the majority of the radio frequency (RF) energy travels to the transmission line 18 which together with the coil is the feed to energize the chassis 22 or PCB 20 or whatever is used for the ground plane to radiate the transmit signals.

In the preferred embodiment of the invention, the whole structure of the wireless communications unit 10 becomes

the antenna. Furthermore the transmission line should be an open structure - of the microstrip type.

Furthermore, when the antenna mode switch 24 is in a `closed' position the antenna current distribution is of lower density over the whole body of the wireless communications unit 10. In this manner, the efficiency near any absorbent article, such as a vehicle or a human body is much higher. With the antenna current distribution being of lower density in this mode of operation, the impedance of the transmission line 18 should not be low (>50ohm) for an effective and broadband antenna.

A prototype antenna structure as described above was built and tested in the applicant's Antenna Laboratory. The results showed a 5dB efficiency-improvement by using this concept.

Referring now to FIG. 2, a wireless communications unit 10 adapted to support the various inventive concepts of a preferred embodiment of the present invention is shown. The arrangement shown in FIG. 2 particularly illustrates the antenna switching operation of the preferred embodiment of the invention.

A modulated signal source 30 is connected to a radio frequency (RF) power amplifier (PA) 32 of the wireless communications unit 10. The RF PA 32 is, in turn, connected via a directional coupler 34 to the antenna 12. The construction of antenna 12 is preferably as described with reference to FIG. 1.

The directional coupler includes a forward'-port 35 and a reflected port 37. The forward port 35 and reflected port 37 of the directional coupler 34 are, in turn, respectively connected to RF detectors 40,42. Each RF detector 40, 42 output is a direct current (DC) voltage signal that is proportional to the reflected and forward RF powers. These DC voltages (V+ and V-) are respectively connected to analogue to digital (A/D) converters 44, 46. Preferably such A/D converters are included within, or at least controlled by, a microprocessor, such as microprocessor 54.

The microprocessor 54 calculates the reflection coefficient p:

Then from the reflection coefficient, the VSWR is calculated:

Based on the measured VSWR value, effectively an indicator of antenna efficiency, the processor determines the preferred operational mode of the antenna. Based on this determination, the microprocessor controls 58 the configuration of an antenna mode switch 24 via antenna mode switch control 52 and the microprocessor's general processor input/output (GPIO) 56 line. Antenna mode switch 24 is a low inter-modulation (IM) element, which limits the amount of spurious energy radiated from the antenna. The antenna mode switch 24 used to reconfigure the antenna, can be either a mechanical switch or a pin diode switch.

In operation, when the wireless communications unit 10 is working in a free space environment, the antenna presents an impedance to the PA that is approximately 50ohm. In this situation the VSWR will be close to a value of "1" and the "antenna mode" switch will be set to an "open" position.

When the wireless communications unit 10 is communicating, e.g. in a telephone call, and working near an absorbent or reflective article that disturbs the antenna radiation pattern and therefore the antenna efficiency, the antenna presents to the PA an impedance that is far removed from 50 ohm. In this situation the VSWR measurement will be greater then 1. In the preferred embodiment of the invention a threshold VSWR = 6:1 was chosen as the threshold for switching the "antenna mode" switch into a `closed' position. However, given a variety of operating environments of the wireless communications unit 10, alternative threshold levels could be set.

As an alternative to a predetermined threshold level, a user-defined threshold level can be used. In this manner the user can dictate and control the operation of the antenna, based on his/her communicating environment. It is also within the contemplation of the invention that such threshold levels could be dynamically adjusted by over-the-air transmissions from a communications system. To further explain the aforementioned benefits, a series of measured radiation patterns are shown, both for prior art antenna arrangements and antenna arrangements embodying the inventive concepts contained herein.

FIG. 3 shows a typical prior art antenna vertical- polarisation radiation pattern 60 with the antenna positioned near an absorbent article. It can be seen that the electromagnetic radiation measurements range between a minimum value 62 of approximately -38d8 to a maximum value 64 of approximately -10dB.

FIG. 4 shows a typical prior art antenna vertical- polarisation radiation pattern 70 with the antenna being positioned at a handheld distance away from an absorbent article. It can be seen that the electromagnetic radiation measurements range between a minimum value 72 of approximately -12d8 to a maximum value 74 of approximately +2d8.

FIG. 5 shows an antenna vertical-polarisation radiation pattern 80 in accordance with the antenna arrangement of a preferred embodiment of the invention, with the antenna being positioned near an absorbent article. It can be seen that the electromagnetic radiation measurements range between a minimum value 82 of approximately -24d8 to a maximum value 84 of approximately -8d8.

A direct comparison can be made of the performance at a worst-case angle of radiation strength when near the absorbent structure, between the prior art antenna shown in FIG. 3 and the antenna arrangement of the preferred embodiment of the present invention shown in FIG. 5. It is clear that the performance of the antenna of the present invention is approximately a 14db improvement over the prior art antenna performance. The average improvement, which is a more realistic figure of the overall efficiency of the antenna arrangement of the

preferred embodiment of the present invention, shows approximately a Sdb improvement.

FIG. 6 shows an antenna vertical-polarisation radiation pattern 90 in accordance with the antenna arrangement of a preferred embodiment of the invention, with the antenna being positioned at a handheld distance away from an absorbent article. It can be seen that the electromagnetic radiation measurements range between a minimum value 92 of approximately -12dB to a maximum value 94 of approximately OdB.

A direct comparison can be made of the performance at a worst-case angle of radiation strength when at a hand- held distance from the absorbent structure, between the prior art antenna shown in FIG. 4 and the antenna arrangement of the preferred embodiment of the present invention shown in FIG. 6. It is clear that the performance of the two antennas is comparable, with a similar average over the azimuth angles. Given that these measurements are taken distal from the absorbent structure, and are therefore more representative of a free-space environment, such similar results are to be expected.

It will be understood that the aforementioned adaptive radiation-efficient antenna, suitable for portable telephone or radio operation, provides a number of significant advantages over prior art antenna arrangements.

One advantage, as previously highlighted, is that the adaptive arrangement dramatically improves the operating efficiency of the antenna. As a consequence,

transmission of lower power signals (or reception of signals using the reciprocity theorem) is a possibility in order to attain the same free-space communication range of prior art antenna arrangements. Furthermore, the reduction in radiation absorption of, say, 10dB and the subsequent improvement to antenna operating efficiency has a significant and beneficial impact for RF coverage system planning. As a consequence, wireless communications units can then communicate over greater distances for the same amount of transmit power output from the RF PA. Therefore less system equipment is required to cover the same geographical area. In an alternative view, a greater coverage area can be attained using equipment employing the inventive concepts contained herein. urthermore, any wireless product manufacturer will find t easier to attain the regulatory requirement for ntenna/radiation performance using the inventive oncepts described herein. In addition, such wireless roducts can be marketed to allay any public concern on F radiation exposure. It is within the contemplation of the invention that any wireless communications unit may benefit from the inventive concepts contained herein, not units limited to cellular telephones or mobile/portable radio equipment. Furthermore, any antenna design or configuration, such as patch, loop or slot antennas may also utilise the inventive concepts contained herein.

It is also within the contemplation of the invention that it can be used in any spatial environment that disturbs the antenna radiation pattern, and not limited to an environment that includes an absorbent article. In summary, the preferred embodiment (s) of the present invention have provided a novel method for rapid antenna efficiency improvement when a wireless communications unit transfers from an idle operating mode into a communicating mode of operation. In order to achieve this rapid antenna efficiency improvement the wireless communications unit automatically detects when it is geographically close to an absorbent article whilst communicating. In such a mode of operation, a processor in the wireless unit dynamically adapts the current distribution of the antenna to increase efficiency, whilst concurrently maintaining a substantially consistent radiation pattern in the far field.

Claims

Claims 1. A wireless communications unit, characterised by a radiating element operably coupled to a processor that reconfigures the radiating element depending upon a mode of operation of the wireless communications unit wherein the mode of operation of the wireless communications unit is determined by a spatial operating environment of the wireless communications unit.
2. The wireless communications unit according to claim 1, further comprising switching means being operably coupled to the processor and the radiating element for effecting the reconfiguration of the radiating element under direction from the processor in response to said determination.
3. The wireless communications unit according to claims 1 or 2, further comprising radiating element performance measurement means operably coupled to the processor and the radiating element for determining the spatial operating environment of the wireless communications unit.
4. The wireless communications unit according to claim 3, wherein the radiating element performance measurement means includes a forward path to determine a power level of a signal transmitted to the radiating element and a feedback path to determine a power level of a signal reflected back from the radiating element, said determination being indicative of the spatial operating environment of the wireless communications unit.

<Desc/Clms Page number 20>
5. The wireless communications unit according to claim 4, wherein said indication of the spatial operating environment includes whether the wireless communications unit is operating in the vicinity of an absorbent structure.
6. The wireless communications unit according to claim 5, wherein reconfiguration of the radiating element is performed by coupling the radiating element to a second radiating element when the wireless communications unit is operating in the vicinity of an absorbent structure.
7. The wireless communications unit according to claim 6, wherein said switching means is operably coupled to said second radiating element such that the switching means couples the radiating element to the second radiating element under the direction of the processor to reconfigure the radiating element.
8. The wireless communications unit according to claim 6 or 7, wherein the second radiating element is complementary to the radiating element to form a re- configured radiating element.
9. The wireless communications unit according to claim 8, wherein said second radiating element portion of the reconfigured radiating element is a substantial ground plane comprising a shielded printed circuit board of the wireless communications unit.

<Desc/Clms Page number 21>
10. The wireless communications unit'.according to claim 8, wherein said second radiating element portion of the reconfigured radiating element is a substantial ground plane comprising a chassis of the wireless communications unit.
11. The wireless communications unit according to any one of the preceding claims, wherein the radiating element is an antenna coil having a conducting cylinder positioned substantially adjacent to the coil.
12. The wireless communications unit according to claim 11, wherein said conducting cylinder is operably coupled to the coil without having a galvanic connection with the coil.
13. The wireless communications unit according to claims 11 or 12, wherein the coil is slightly de-tuned to increase the bandwidth of the radiating element and/or the stability of the radiating element when the wireless communications unit is in the vicinity of the absorbent article.
14. The wireless communications unit according to any one of claims 11 to 13 when dependent upon any one of claims 6 to 10, wherein the conducting cylinder is used as a feeder for the second radiating element.

<Desc/Clms Page number 22>
15. A radiating element comprising a coil operably coupled to a conducting cylinder with said conducting cylinder positioned substantially adjacent to the coil.
16. The radiating element according to claim 15, wherein said conducting cylinder is operably coupled to the coil without having a galvanic connection with the coil.
17. The radiating element according to claims 15 or 16, wherein the coil is slightly de-tuned to increase the bandwidth of the radiating element and/or the stability of any wireless communications unit connected thereto.
18. The radiating element according to any one of claims 15 to 17, wherein the radiating element is operably coupled to a second radiating element and the conducting cylinder is used as a feeder for the second radiating element.

<Desc/Clms Page number 23>
19. An antenna switching arrangement in accordance with any one of the preceding claims.
20. A method of operating a wireless communications unit comprising a radiating element operably coupled to a processor, the method characterised by the steps of: determining a spatial operating environment of the wireless communications unit and/or a mode of operation of the wireless communications unit; and reconfiguring the operation of the radiating element depending upon said determination.
21. The method of operating a wireless communications unit according to claim 20, the wireless communications unit further comprising switching means being operably coupled to the processor and the radiating element; the method further characterised by the step of: effecting the reconfiguration of the radiating element by said switching means under direction from the processor in response to said determination.
22. The method of operating a wireless communications unit according to claims 20 or 21, wherein the wireless communications unit further comprises radiating element performance measurement means including forward and feedback paths, the method further characterised by the steps of: determining a power level of a signal transmitted to the radiating element; determining a power level of a signal reflected from the radiating element; and determining the spatial operating environment of the wireless communications unit based on said determination of power signals.

<Desc/Clms Page number 24>
23. The method of operating a wireless communications unit according to any one of claims 20 to 22, wherein said indication of the spatial operating environment includes whether the wireless communications unit is operating in the vicinity of an absorbent structure.
24. The method of operating a wireless communications unit according to any one of claims 20 to 23, wherein the step of reconfiguring of the radiating element is performed by coupling the radiating element to a second radiating element if the wireless communications unit is operating in the vicinity of an absorbent structure.
25. The method of operating a wireless communications unit according to claim 24 when dependent upon any one of claims 21 to 23, wherein the switching means is operably coupled to the second radiating element, the method further characterised by the step of: coupling by the switching means the radiating element to the second radiating element under the direction of the processor.
26. A wireless communications unit substantially as hereinbefore described with reference to, and/or as illustrated by, FIG. 2 of the drawings.
27. A radiating element substantially as hereinbefore described with reference to, and/or as illustrated by, FIG. 1 of the drawings.