Antenna arrangement

An antenna arrangement comprises a central part extending in a first plane, an antenna element comprised in an antenna part, which antenna part and antenna element extend from the central part in a second plane, a first counterpoise part, extending from the central part in a third plane, and a second counterpoise part extending from the central part in a fourth plane, the antenna arrangement is arranged in a functional position. The functional position implying that the folded first and second counterpoise parts together represents a counterpoise and the antenna element resonates together with the counterpoise, thus making the whole antenna arrangement serve as an antenna.

TECHNICAL FIELD

The present invention relates to wireless communication. In particular the present invention relates to an antenna arrangement and a wireless communication device comprising such an antenna arrangement.

BACKGROUND

It is often desirable to provide wireless communication rather than wired communication using cables between related pairs of devices separated by a short distance. Devices that communicate using cables often require the devices to be located in close proximity to each other as dictated in part by the length of the cables. In contrast, wireless communication decreases the amount of cabling between electronic devices and thus increases the ease of use and convenience for the user. Further the wireless communication devices, such as a portable electronic device, may add more security and may be more aesthetic. With wireless communication, the distance between the related devices is generally only limited by the limits of the wireless signal transmission and reception systems. Examples of related pairs of devices include a cordless headsets on the one hand and a telephone, computer, Personal Digital Assistant (PDA), television set, VCR, DVD player, video game player, stereo receiver, CD player, and MP3 player on the other hand. Other examples of related pairs of devices include a computer and its various external devices such as a monitor, printer, keyboard, mouse, telephone and speakers for example.

The portable electronic device comprises a small inbuilt antenna of high performance to perform as required. The antenna enables wireless communication between a radio unit in the portable electronic device and a radio unit in a corresponding unit. In general it is desirable to minimize the size of the portable electronic device so as to provide a device that is as discrete and as practical as possible. Thus the space for the antenna in the portable communication device is reduced almost day by day, resulting in a keen need of improvement for the antenna miniaturization.

The volume within the portable electronic device is governed by industrial design and may place restrictions on both the size of the antenna and the size of the ground plane. However the dimensions of the antenna residing within the portable electronic device are dictated by the wavelengths of the signals that the antenna is to receive and transmit as well as the form of the antenna. Examples of such signal wavelengths are e.g. Bluetooth 2400-2483.5 MHz which corresponds to a wavelength of about 12 cm in free space. Thus the antenna and the portable electronic device are designed with mutual consideration in order to accommodate the antenna within the portable electronic device.

Many types of antenna technologies may be chosen for the internal antenna of the portable electronic device. The selection depends upon the size and shape of the portable communication device volume into which the antenna must fit and the system performance requirements of the antenna.

A commonly known antenna is the T-antenna. The T-antenna comprises two wires, a first vertical or sloping wire and a second straight horizontal wire. The vertical wire is connected to the approximate central of the straight horizontal wire, thus forming the characteristic “T”-shape. The radiation pattern of a T-antenna is Omni-directional, just like a dipole antenna. The T-antenna is easily scalable relative to the used frequency(s). A disadvantage of a stretched-wire ½ wave dipole or T-antenna is the overall physical length of it. This makes it difficult to integrate it into a small product.

Meandered mono pole antennas are also commonly used in portable communication devices. The meandering pattern of the antenna enables a reduction of the overall physical length of the antenna element whilst retaining the same electrical length. Thus the meandered mono pole antenna is more scalable than the stretched wire dipole. The total length of a meandered monopole antenna is preferably chosen to be one quarter of the wavelength of the desired resonant frequency. However, other lengths could also be used for the resonator elements including three quarters, one and one quarter, ⅕'th etc. A disadvantage of a meandered monopole is still the relative large area it needs. The meandering of the antenna employs a relatively larger area compared to the area employed by a straight wire. Further the space between the meandering lines is unused. If this space is compromised to a minimum the bandwidth of the antenna is also compromised. This largely depends on the gab between the meandering pattern and the number of meanderings.

An Inverted F Antenna (IFA) is a planar antenna, having a low profile or a flat structure, that are commonly employed as internal antennas configured inside portable communication devices, such as handsets, operating in e.g. the 1900 MHz radio frequency band. A conventional Planar Inverted F Antenna (PIFA) includes a radiating element, a wire and a ground plane. The planar inverted F antenna is shaped like the letter F. The planar inverted F antenna, as well as, an inverted F antenna, both requires a relatively large ground plane to work correctly. This significantly limits the scalability of the F antenna types. Further the F antennas suffer from a narrow bandwidth characteristic which is a considerable limitation.

/Thus what is needed is an antenna for use in a portable communication device that meets the required communication performance without or with minimized performance degradation. Further it is highly desirable that the antenna is small, space efficient and light thus avoiding clumsy and unwieldy devices. In the case of the portable communication device being represented by a cordless headset it is further desirable that the antenna has a high efficiency when the headset is put in talk position, i.e. is arranged close to the body of the user.

The antenna should preferable also be configured to allow better placement of control switches, electronic components and/or buttons of the portable communication device. Ideally the antenna is also cost-effective to manufacture and easy to assemble.

SUMMARY

The object of the present invention is to provide an antenna arrangement that is small, space efficient and light whilst still meeting the required communication performance without or with minimized performance degradation.

According to a first aspect of the invention, the object is achieved by an antenna arrangement for wireless communication. The antenna arrangement comprises a central part extending in a first plane and an antenna element comprised in an antenna part which antenna part and antenna element extend from the central part in a second plane. The antenna arrangement further comprises a first counterpoise part extending from the central part in a third plane and a second counterpoise part extending from the central part in a fourth plane. The antenna arrangement is arranged in a functional position. The functional position is obtained when the antenna arrangement is folded such that:

The second plane of the antenna element s principally perpendicular to the first plane of the central part, the third plane of the first counterpoise part, is principally perpendicular to the first plane of the central part and principally perpendicular to the second plane of the antenna element, and the fourth plane of the second counterpoise part is principally perpendicular to the first plane of the central part and principally parallel with the second plane of the antenna element, and principally perpendicular to the third plane of the first counterpoise part. The functional position implies that the folded first and second counterpoise parts together represents a counterpoise and the antenna element resonates together with the counterpoise, thus making the whole antenna arrangement serve as an antenna.

In one embodiment, the antenna arrangement further comprises a third counterpoise part extending from the central part in a fifth plane. The functional position is obtained when the antenna arrangement is folded such that further the fifth plane of the third counterpoise part is principally parallel with the third plane of the first counterpoise part. The functional position implying that the folded first, second and third counterpoise parts together represents a counterpoise and the antenna element resonates together with the counterpoise, thus making the whole antenna arrangement serve as an antenna.

In one embodiment of the antenna arrangement, the antenna element is a T antenna or a monopole.

In one embodiment the antenna element is represented by a conductive material such as e.g. copper.

In one embodiment the functional position is represented by the shape of a vessel, a housing, a box, a container, a case holder, a receptacle, a reservoir.

In one embodiment the antenna arrangement is represented by a printed circuit board, a flexible printed circuit board, a conductive material.

In one embodiment the antenna arrangement comprises holes and/or through going cavities.

In one embodiment antenna arrangement is tuned to a wanted resonation frequency by adjusting the length and width of one or a plural of the arms of the antenna element.

In one embodiment the resonation frequency is 1-80 GHz, e.g. 2.5 GHz.

According to a second aspect of the invention the object is achieved by a wireless communication device comprising an antenna arrangement according to the first aspect of the invention

In some embodiments the wireless communication device is represented by a head set, a cordless telephone, a cordless mouse, a cordless computer or a Personal Digital Assistant (PDA).

The present invention is very advantageous compared to prior art solutions, such as the inverted F antenna and the planar inverted F antenna which are designed to concentrate radio frequency currents only around the antenna area. The antenna arrangement according to the present solution instead uses the relative small 3D build-up ground plane (counterpoise) to radiate also. This gives the benefit of having an antenna arrangement100in functional position that is very space efficient and having good antenna efficiency near the human body but still is relative small in size.

DETAILED DESCRIPTION

The invention is defined as an antenna arrangement which may be put into practice in the embodiments described below. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It should be understood that there is no intent to limit the present method or arrangement to any of the particular forms disclosed, but on the contrary, the present method and arrangement is to cover all modifications, equivalents, and alternatives failing within the scope of the invention as defined by the claims.

When using the word “comprise” or “comprising” it shalt be interpreted as non-limiting, in the meaning of “consist at least of”.

FIG. 1depicts an antenna arrangement100according to some embodiments of the present solution before being arranged and folded into a functional position. The antenna arrangement100may be adapted to be used in a wireless device. Examples of such wireless devices are e.g. a cordless headset, a cordless mouse, a cordless printer, a cordless monitor for a computer and/or a phone and/or a Personal Digital Assistant (PDA), a cordless computer communicating with a corresponding computer dock.

The antenna arrangement100as depicted inFIG. 1is arranged in a first position wherein the antenna arrangement100extends primarily in two dimensions. This is due to the fact that the antenna arrangement100also has a certain depth. According to some embodiments the antenna arrangement100in the first position may be flat and may be unfolded. The antenna arrangement100does not serve as the high efficient antenna in the first position, but could as well be a good functioning antenna. The antenna arrangement100may be made of e.g. a Printed Circuit Board (PCB), a flexible PCB or any relatively good conductive material.

The antenna arrangement100comprises a central part120extending in a first plane.

The antenna arrangement100further comprises an antenna element115. The antenna element115is comprised in an antenna part110. The antenna part110and antenna element115extend from the central part120in a second plane. The antenna arrangement100is adapted to convert signals received and/or signals to be output by the antenna element115.

The antenna part110further comprises a first counterpoise part,130extending from the central part120in a third plane, and a second counterpoise part140extending from the central part120in a fourth plane.

The antenna arrangement100, may further comprise a third counterpoise part (150) extending from the central part (120) in a fifth plane.

In this first position depicted inFIG. 1, before being arranged into a functional position, the antenna element115, the central part120, the first counterpoise part130, the second counterpoise part140and the third counterpoise part150if available all extends in the same plane. When the first counterpoise part130, the second counterpoise part140and the third counterpoise part150if available are folded into a functional position, together they represent a counterpoise. This is further described below.

In some embodiments, the antenna arrangement100is roughly shaped as a box like inFIG. 3(to be described below) which is very advantageous for obtaining symmetrical near field behaviour when the antenna arrangement is arranged in a functional position, i.e. the functional position (FIG. 3).

The antenna arrangement100may further comprise common components to be able to work such as e.g. a signal converter, a signal contact and a small ground plane called a counterpoise (there is no real ground plane).

According to some embodiments the design of both the antenna element115and antenna arrangement100should be drawn with care and should at least contain one layer with a conducting covering of good conductivity. It is possible to have a less covering area concerning the planes of the central part120, the first counterpoise part130, the second counterpoise part140and the third counterpoise part150if available. But on average these should be a good enough counterpoise for the antenna—covering may be only of parts of the central part120, the first counterpoise part130, the second counterpoise part140and the third counterpoise part150if available. This is because the whole design of the antenna arrangement100, such as e.g. a PCB, serves as an antenna, since the whole design of the antenna arrangement100, when being arranged in a second position, i.e. a functional position, contributes to high performance of the antenna arrangement100.

A counterpoise is just a small/bad ground plane which is divined relative to the longest relevant used wavelength of a device. A relative good ground plane covers at least and area lager then the square of the ½ wavelength.

If an antenna element as part115is mounted on a small ground plane, called a counterpoise, the counterpoise also starts to radiate and effectively becomes part of the whole antenna. If the counterpoise is too small then the antenna configuration doesn't work as efficient anymore.

The antenna element115may be made of a conductive material such as e.g. copper or a combination of conductive materials. The antenna element115may be adapted for wave lengths such as e.g. 1 GHz to 80 GHz. The antenna element115may be a small built-in antenna, thus the antenna element115is a part of the antenna arrangement100which may be arranged on or be integrated in the antenna part100.

According to the embodiments wherein the antenna arrangement100is made of an Isolating material conducting wires may be needed to connect the antenna element115to an exciting point, e.g. placed at the folding between the central part120and the antenna part110. Impedance matching may be commonly performed in order to maximize power transfer and minimize reflections of a signal back into the source.

According to some embodiments the antenna element115may be e.g. a T antenna, a monopole antenna or a conductive element of any shape which resonates together with the counterpoise to enlarge the antenna element115to enable the whole antenna arrangement100to serve as an antenna. The antenna arrangement100serves as an antenna with or without a matching network. A common matching network may comprise combinations of transformers, resistors, inductors and capacitors. The matching network is not depicted in any Figure.

FIG. 2depicts the exemplary scenario wherein the antenna element115is a T antenna. The antenna element comprises a first arm210which is connected at a first end211to a central point of a second arm220. The first arm210extends generally along a longitudinal length of the antenna element115. The second arm220extends generally along a latitudinal length of the antenna element115. The second arm220serves as a signal radiation and reception element and the first arm210also serves as a signal radiation and reception element. As depicted inFIG. 2according to some embodiments the second arm220may be bent in one or both ends. The bending of the second arm220may be performed to be able to fit the antenna element within the antenna arrangement100. Thus the shape of the antenna element115may be dependent of the shape of the antenna arrangement100. Thus the antenna element115according to the present solution is very space efficient.

The shape of the antenna element115may be necessary when tuning the whole antenna arrangement100to a wanted resonation frequency. Examples of wanted resonation frequencies may be in the range of 1-80 GHz such as e.g. 2,5 GHz for Bluetooth communication. Tuning of resonation frequency may be performed by adjusting the length and width of the first arm210and/or the second arm220of the figure T of the antenna element115. This means that the antenna arrangement100may be tuned to a wanted resonation frequency by adjusting the length and width of one or a plural of the arms210,220of the antenna element115.

The first arm210may comprise a second end212which is connected to an exciting port. The second end212of the first arm210of the antenna element115may be attached to the antenna arrangement100by using screws, rivets, pop rivets, by soldering, etched copper traces etc.

The antenna element100is adapted to be used when being arranged in a second position, from now on called the functional position300as seen inFIG. 3.

The functional position300, which also may be called the functional position, comprises arranging, such as e.g. folding, bending, bowing, curving, some, or all, of the counterpoises in three dimensions. When using the word folding in this document it should be interpreted as any of folding, bending, bowing or curving.

According to the embodiments wherein the antenna arrangement100is comprised in a portable communication device, such as e.g. a headset the functional position300may be represented by an upright talk position located close to the body of the user, such as a left talk position and/or a right talk position.

The antenna arrangement100may be arranged in the functional position300in different ways. In the example ofFIG. 3

To serve as an antenna, the antenna arrangement100is arranged in a functional position. The functional position is obtained when the antenna arrangement100is folded, i.e. folded, bent, bowed or curved or similar such that:

The second plane of the antenna element115is principally perpendicular to the first plane of the central part120;

The third plane of the first counterpoise part130, is principally perpendicular to the first plane of the central part120and principally perpendicular to the second plane of the antenna element115; and

The fourth plane of the second counterpoise part140is principally perpendicular to the first plane of the central part120and principally parallel with the second plane of the antenna element115, and principally perpendicular to the third plane of the first counterpoise part130.

If, the antenna arrangement100further comprises the third counterpoise part150, the functional position being obtained when the antenna arrangement100is folded such that further the fifth plane of the third counterpoise part150is principally parallel with the third plane of the first counterpoise part130.

The functional position implies that the folded first, second and if available third counterpoise parts130,140,150together represent a counterpoise and the antenna element115resonates together with the counterpoise130,140,150, thus making the whole antenna arrangement100serve as an antenna.

The parts refer to being folded “principally perpendicular” and “principally parallel”. This means that when folding the parts, i.e. the antenna element115, the central part120, the first counterpoise part130, the second counterpoise part140and the third counterpoise part150if available, the antenna arrangement serves well as an antenna even if not being exactly perpendicular or parallel but more being principally perpendicular or parallel.

I.e. the functional position may be obtained by folding the antenna part110about 90 degrees toward the central part120and folding the second counterpoise part140about 90 degrees toward the central part120. This results in that the antenna part110and the second counterpoise part140are arranged beside each other in parallel or close to in parallel. Further the first counterpoise part130is folded about 90 degrees, towards the central part120and the third counterpoise part150is folded about 90 degrees towards the central part120. This results in that the first counterpoise part130and third counterpoise part150are arranged beside each other in parallel or close to in parallel. When the antenna is arranged in the functional position300some or all of the counterpoise parts are arranged in three dimensions forming e.g. a vessel, housing, box, container, case holder, receptacle reservoir.

The folded second position of the antenna arrangement100is highly advantageous since it enables a high efficiency in use of physical space, which results in a small design.

According to some embodiments some parts of, or all of, the antenna arrangement100may be used to put at least one component175on or nearby, as depicted inFIG. 1andFIG. 3. The antenna arrangement100may preferable be configured to allow a space efficient placement of the components175such as e.g. control switches, electronic components and/or buttons of the portable communication device in which the antenna arrangement100may be comprised. This enables a good space efficiency of the antenna arrangement100. This is very advantageous because it contributes to the minimization of the antenna arrangement100as well as of the portable communication device in which the antenna arrangement100may be used.

According to some embodiments the components175may be mainly made of a conductive material thus enabling the components to contribute to the operation of the antenna arrangement100.

The antenna arrangement100is according to some embodiments almost 100% space efficient since some parts of or all of the antenna100may be used to put components175on or nearby.

The performance of the antenna arrangement100when being arranged in the second position300is very advantageous. Firstly since the antenna arrangement100provides a high bandwidth 33% relative to the centre frequency of the complete antenna arrangement100. Secondly because the antenna efficiency, when the antenna arrangement100is arranged in the second position300such as e.g. placed in upright position, is much better compared to the antenna efficiency of a flat antenna such as e.g. a dipole or an Inverted F Antenna. All these points together make this a very powerful combination, especially when the antenna is operating very close to the body called talk position for a headset. In free space the efficiency of both antennas could be very well the same.

Thus the second position300, i.e. the three dimensional build-up, of the antenna arrangement100has a positive effect on antenna efficiency, compared to prior art.

The design of the antenna arrangement100is flexible in such a way that the outline of the antenna arrangement100may be arranged in different ways. An example is seen inFIG. 4.FIG. 4depicts a close-up of an exemplary embodiment of the second counterpoise part140where the outline400of the antenna arrangement100comprises straight parts, corners and round bends. Further the design of the antenna arrangement100is flexible in such a way which may render it possible for the antenna arrangement100to comprise a through going cavity410. The through going cavity410may be used to put components175trough. Examples of such components175may be non conductive components, such as e.g. a plastic button, a mounting pin, etc. This is very advantageous since the design of where and how to arrange the components175attached to the antenna arrangement100may be simplified. Thus the flexible design of the antenna arrangement100may render it possible to minimize the size and the design of the antenna arrangement100since the components175arranged on the antenna arrangement100may be located in an optimized way concerning the physical space. This makes it possible to further minimize the wireless device wherein the antenna arrangement100may be comprised.

FIG. 5depicts a wireless communication device500comprising the antenna arrangement100. The wireless communication device500may be represented by a head set, a cordless telephone, a cordless mouse, a cordless computer, a Personal Digital Assistant (PDA) or similar.