WO2001082409A1

WO2001082409A1 - An antenna device and a method of manufacturing such a device

Info

Publication number: WO2001082409A1
Application number: PCT/SE2001/000919
Authority: WO
Inventors: Istvan Bartha; Annika Yidong Hu; Daniel Sundberg
Original assignee: Allgon Mobile Communications Ab
Priority date: 2000-04-27
Filing date: 2001-04-27
Publication date: 2001-11-01
Also published as: SE0001537L; SE0001537D0; AU5283501A

Abstract

An antenna device (1) comprises a support structure (10), a first internal antenna (20) and a second extendable/retractable whip antenna (30). The second antenna is slidingly mounted in an electrically conduc-tive tube (36,38) connected to the internal antenna. The tube functions both as a connector for the whip antenna with the second antenna in an extended end position as well as a matching means for the internal antenna. The tube can also function as a radiating element. Operation in more than one frequency band can thus be supported.

Description

AN ANTENNA DEVICE AND A METHOD OF MANUFACTURING SUCH A DEVICE

FIELD OF INVENTION The present invention relates generally to an antenna device and more particularly to a combined antenna device including an internal antenna and an external antenna connected in extended mode. The present invention also relates to a portable communication device comprising such an antenna device and a method of manufacturing such an antenna device.

BACKGROUND

It is well known in the portable communication device art, such as with mobile phones, to use a combination of a first internal antenna and a second extendable/- retractable antenna, such as a whip antenna. Because a whip antenna can be cumbersome when extended, it is normally preferred that it be retracted except when the communication device is actively being utilised.

The use of dual antennas poses a special problem regarding the coupling and decoupling of the different antenna devices. Normally, the extendable/retractable antenna should be electrically decoupled from a feeding device when in a retracted position while it should be electrically coupled when in an extended position. Also, a dual antenna solution poses problems regarding RF matching.

A common requirement for antenna devices used with mobile phones is that they support operation in more than one frequency band. This feature can be difficult to obtain with the mechanical limitations imposed by the small size of the device in which the antenna device is mounted.

The patent publications WO 97/34377 and WO 99/03166 describe different antenna devices comprising a first meander-shaped antenna and a second extendable/- retractable antenna in the form of a whip antenna. However, neither of these documents describes the assembly of the antenna device or RF matching by means of the extendable antenna.

The US patent US 6,031,496 (Kuittinen et al.) discloses a combination antenna with two parts and a connector part to connect them to a radio apparatus . The two antenna parts are separated from each other and a plating is provided to protect the user's head from radiation. No RF matching or multi-frequency operation are described.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an antenna device of the kind initially mentioned that has a simple construction and is inexpensive to manufacture.

Another object is to provide an antenna device wherein the matching of the internal and the external antennas is facilitated.

Yet another object is to provide an antenna device wherein a multiple band function can be provided. The invention is based on the realisation that an elongated metal tube can be used together with a whip antenna and an internal antenna in order to obtain a simple and yet reliable construction and wherein the metal tube both give one resonance frequency for RF and can be used for RF matching of the combination of the internal antenna and the whip antenna.

According to the present invention there is provided an antenna device as defined in claim 1.

There is also provided a portable communication device as defined in claim 16.

There is also provided a method of manufacturing an antenna device as defined in claim 17.

By means of the antenna device, the manufacturing method and the portable communication device according to the invention, at least some of the drawbacks associated with prior art are overcome.

Preferred embodiments are defined in the dependent claims .

BRIEF DESCRIPTION OF THE DRAWING

The invention is now described, by way of example, with reference to the accompanying drawing, in which:

Fig. 1 is a perspective view of an antenna device according to the invention;

Fig. 2 is a plan view of the device of figure 1 with a whip antenna in a retracted position, and Fig. 3 is a view similar to that of figure 2 but with the whip antenna in an extended position.

DETAILED DESCRIPTION OF THE INVENTION

In the following, a detailed description of a pre- ferred embodiment will be given. Where a described element denoted by a numeral comprises several parts, these parts are distinguished by means of an accompanying letter.

Figure 1 shows an antenna device 1 comprising a frame 10 for supporting radiating and receiving antenna elements. The frame 10 is a generally box like plastic element adapted to be mounted in a housing of a portable communication device, such as a mobile phone. In order to decrease the total weight of the antenna de- vice, the frame 10 can be made hollow. The frame 10 is supporting on the upper surface thereof 11a, lib, in the following collectively referred to by the reference numeral 11, a first internal antenna, generally designated 20, including a printed antenna pattern or electrically conductive layer 22, in the figures shown as a pattern for a so-called modified PIFA antenna.

The frame 10 is adapted to be mounted to a printed circuit board (not shown) functioning as a ground element for the antenna device. The frame and thereby the conductive layer 22 will then be positioned at a predetermined distance from the ground plane and generally parallel thereto by means of four legs 13, three of which 13a-c are shown in figure 1. The legs 13 are provided with a respective hook at the ends thereof for a snap-in mounting of the frame to the printed circuit board. The thickness of the frame material and the distance between the conductive layer 22 and the ground plane will partly determine the characteristics of the antenna 20.

The frame 10 is also provided with a recess 12a, 12b, 12c, in the following collectively referred to by the reference numeral 12, for reception of an extendable/- retractable antenna, such as a whip antenna, generally designated 30. The recess 12 is divided into three portions, comprising a first narrower portion 12a and a second wider portion 12b. The narrower portion has an essentially circular cross-section with an opening to the upper surface 11 of the frame to allow the whip antenna to be inserted therein by means of a "click- in" function. Between these narrower and wider portions 12a, 12b, there is a portion 12c with slanting walls arranged for a smooth transition from the recess 12 to the upper surface 11 of the frame. This slanting portion 12c is provided for the antenna 20 to pass be- low the whip antenna 30, the function of which will be described below.

The upper surface 11 of the frame 10 is provided with a conductive layer 22 in the shape of a modified PIFA pattern and functioning as a first radiating element of the antenna device. The conductive layer 22 is preferably disposed on a flexible film carrier, which in turn is attached to the upper surface 11 of the frame 10. The conductive layer is made of an electrically conductive material, such as aluminium or copper. The conductive layer 22 is arranged to be connected to the ground element (not shown) by means of a grounding means connected at a grounding portion 24. The conductive layer 22 is also arranged to be connected to RF circuitry by means of a feeding element (not shown) connected at a feeding portion 26.

The upper surface 11 of the device 10 as seen in figure 1 is divided into two parts 11a and lib by the recess 12. The first portion 11a is provided with the conductive layer 22 and the second portion lib comprises the feeding portion 26. The feeding portion is connected to the conductive layer 22 by means of a conductive path 27 passing through the recess 12 at the slanting portion 12c.

The whip antenna 30 comprises an elongated whip part 32 arranged to be slidingly mounted in a conductive tube 36 and functioning as a radiating element. The whip part is isolated by means of an isolating outer layer made of for example rubber or plastics and is provided with a knob 33 at the outer end thereof. At the opposite end, i.e., at the inner end, the whip is provided with an enlarged coupling end portion or stopper 34 made of some suitable metal. The stopper is divided into four identical portions by means of four slits therein, see figure 1. By means of this, the stopper is provided with a resilient characteristics used for keeping the whip in position, see below.

The tube 36 in which the whip part 32 is arranged is made of some suitable metal, such as copper, brass or stainless steel. At one end thereof, the tube 36 is provided with a wider portion 38 for reception of the stopper 34. The wider portion 38 has an inner diameter that is slightly smaller than the outer diameter of the stopper 34. However, the resilient characteristics of the stopper enables it to be inserted into the wider portion 38 and be held in position by means of the forces exerted by the stopper 34 on the inner surface of the wider portion 38.

Besides functioning as a reception element for the stopper 34, the wider portion 38 also functions as a connector element, connecting the tube to the conductive path 27 of the first antenna being provided in the slanting part 12c of the recess 12. Also, in extended mode of the whip 30, the wider portion 38 provides coupling between the stopper 34 of the whip 30 and the metal tube 36 and therewith with the conductive layer 22.

The whip antenna 30 is arranged to be mounted in the recess 12. In mounted position, the whip 30 is thus positioned with the wider portion 38 directly above the conductive path 27 interconnecting the conductive layer 22 and the feeding portion 26 and in contact therewith. Thus, the tube 36 is always in galvanic contact with the first radiating element 22 and there- by the conductive tube can be used for RF matching of the first antenna. This matching is achieved by adjusting the length of the tube 36 so at so give desired matching. Thus, the tube provides a flexible and cost-efficient means for matching of an internal antenna, such as a modified PIFA. The tubes used for the antenna device can be stored in different pre- determined lengths or be stored in a standard length, which is then adapted by means of e.g. cutting at the time of assembly.

Alternatively or additionally, the tube 36 functions as a radiating element by itself, operating at a different RF resonance frequency than the first radiating element 22. The properties of the tube, e.g. resonance frequency, are adjusted by means of adjusting the length of the tube, just as with the RF matching.

With the whip in a retracted position, see figure 2, the whip is positioned with the non-conductive whip portion 32 facing the wider portion 38. Thus, there is no electrical contact between the whip portion 32 and the tube 36, whereby the whip is in a non-operative position, i.e., being decoupled from the feeding RF circuitry. However, when the whip portion 32 is moved to an extended position, see figure 3, the wider portion 38 receives the stopper 34 of the whip antenna. In the extended end position shown in figure 3, the conductive stopper 34 of the whip is in electric contact with the metal tube and thereby with the feeding portion 26 via the wider portion 38 of the metal tube 36 and the conductive path 27 of the first antenna.

The manufacturing and assembly of the antenna device 1 will now be described. The plastic frame 10 is moulded in a conventional way to the shape shown in figure 1. The conductive layer 22 is then deposited on the upper surface of the frame 10 in a convenient way, e.g. by means of taping, gluing or heat staking.

The whip antenna 30 can be assembled simultaneously with the first antenna 20. The whip portion 32 is manufactured in a suitable way known to the person skilled in the art. It is then inserted into the metal tube 36, which has been shaped from a sheet metal, for example, with a thickness of about 0.1 - 0.5 millimetres. The tube can be made in one piece or in two or more subsequently assembled pieces. To complete the assembly of the whip antenna 30, the stopper 34 is attached to the whip portion 32.

Finally, the whip antenna 30 is mounted into the recess 12 by means of the "click-in" function provided by the narrower portion 12a of the recess 12. Thus, the design of the antenna device provides for an easy and straightforward assembly process.

The above described embodiment provides an antenna device which is compact, easy to manufacture and easy to assemble. Both the height and the width of the device can be made to fit in a modern compact size mobile phone .

It is realised that the antenna device according to the invention can be varied within the scope defined by the appended claims. Thus, the radiating and receiving elements have been shown with specific shapes. It is realised that they can have any suitable shape adapted for the specific requirements on the antenna in question. The first antenna has been described as a modified PIFA. However, the first antenna can be of any suitable internal antenna type, such as a conventional PIFA, micro-strip, patch, or meander antenna.

The grounding portion 24 has been shown located at a specific position. However, it could be positioned at any suitable place as long as the desired characteristics of the antenna device are obtained. As an example, the grounding portion could even be somewhere along the tube 36.

In the preferred embodiment, galvanic coupling is used for coupling the whip antenna 30 to the internal antenna 20. However, also capacitive or inductive coupling can be used. In that case, the stopper 34 is provided with an electrically non-conductive layer preventing direct electrical contact between the tube 36 and the whip 32 in an extended end position of the whip.

Also, when using galvanic coupling between the internal antenna and the whip antenna, the invention is not limited to an internal antenna wherein the conductive layer 22 and the feeding portion 26 are located on each side of the tube 36. Thus, the grounding and feeding portions 24, 26 could be located at an edge of the first portion 11a of the upper surface 11 while the conductive path 27 ends at a distance from an edge of the second portion lib of the upper surface 11.

In the preferred embodiment, the stopper 34 is divided into several portions, thereby making it resilient. Instead, the end portion 38 of the tube 36 can be made resilient, e.g., by making it flanged. In that case, the stopper 34 can be made non-resilient.

It is realised that the extent to which the whip an- tenna 30 is extended can be used for matching purposes. Thus, by adjusting the extended end position of the whip antenna, the RF characteristics of the whip antenna and the internal antenna can be adjusted.

In the embodiment shown in the figures, the upper sur- face 11 of the frame 10 is divided into two portions

11a, lib by the recess 12. However, it is equally possible to provide the recess on an edge surface of the frame 11. In that case, the upper surface 11 of the frame can remain undivided.

The term radiating element has been used herein for the part of an antenna, which radiates electromagnetic waves. It should be understood that this element also could be used for receiving electromagnetic waves as well. Also, throughout this application, with the expression "internal antenna" or "internal antenna element" is to be understood an antenna or antenna element provided in the housing of a radio communication device or on a surface of a non- protruding portion of the housing of the device.

Claims

1. An antenna device, comprising

- a support structure (10),

a first internal radiating element (22) provided on said support structure,

a grounding portion (24) connected to said first radiating element (22) and electrically connectable to a grounding element, and

a feeding portion (26) connected to said first radiating element (22) and electrically connectable to RF circuitry, and

an elongated second radiating element (32) arranged slidingly between a first extended end position, in which it is coupled to said feeding portion (26), and a second retracted end position, in which it is decoupled from said feeding portion (26),

characterised by

- an electrically conductive tubular element (36,38) being supported by said support structure and being permanently coupled to said first radiating element (22),

- wherein said second radiating element (32) is slidingly supported by said tubular element.

2. The antenna device according to claim 1, wherein said first radiating element (22) is generally planar.

3. The antenna device according to claim 1 or 2 , wherein said first radiating element (22) is shaped for operation in one of the following antennas: a modified PIFA, a conventional PIFA, a micro-strip antenna, a patch antenna, or a meander antenna.

4. The antenna device according to claim 1, 2, or 3, wherein said second radiating element (32) is a whip antenna.

5. The antenna device according to any of the preceding claims, wherein said support structure (10) is provided with a recess ( 12a, 12b, 12c) on a surface (11a, lib) thereof, said recess being adapted for receiving said tubular element (36,38).

6. The antenna device according to claim 5, wherein said surface (11a, lib) is divided into a first (11a) and a second (lib) portion by said recess ( 12a, 12b, 12c) , and wherein said first radiating element (22) is provided on said first portion (11a) and said feeding portion (26) is provided on said second portion (lib), said first radiating element and said feeding portion being interconnected by means of an electrically conductive path (27) arranged to be in contact with said tube (36,38), preferably with an end portion (38) of said tube.

7. The antenna device according to claim 5, wherein said surface (11a, lib) is divided into a first (11a) and a second (lib) portion by said recess ( 12a, 12b, 12c) , and wherein said first radiating element (22) and said feeding portion (26) are provided on said first portion (11a).

8. The antenna device according to claim 5, wherein said recess ( 12a, 12b, 12c) is provided on an edge surface of said support structure (10).

9. The antenna device according to any of the preceding claims, wherein said tubular element (36,38) is provided with an end portion (38) being arranged to receive an end portion (34) of said second radiating element ( 32 ) .

10. The antenna device according to claim 6, wherein, with the second radiating element (32) in said extended end position, said end portion (38) of the tube (36) provides electrical coupling between said second radiating element (32) and said first radiating element (22).

11. The antenna device according to any of the preceding claims, wherein said tubular element (36,38) functions as an RF matching means for said first radiating element (22).

12. The antenna device according to claim 11, wherein said matching is obtained by adjusting the length of said tubular element (36,38).

13. The antenna device according to any of the preceding claims, wherein said tubular element (36,38) functions as at least a part of a radiating element.

14. The antenna device according to claim 13, wherein the operating frequency of said at least a part of a radiating element is adjusted by means of adjusting the length of the tubular element (36).

15. The antenna device according to any of the preceding claims, wherein said grounding portion (24) is provided on said tubular element (36,38).

16. A portable communication device, comprising a housing and RF circuitry, characterised by an antenna device according to any of the preceding claims mounted in said housing and connected to said RF circuitry.

17. A method of manufacturing an antenna device, comprising the steps of:

a) providing a support structure (10) having a recess (12a, 12b, 12c) ,

b) depositing a first antenna portion (20) on said support structure, said first antenna portion having a first radiating element (22), a grounding portion (24), and a feeding portion (26), said grounding and feeding portions being connectable to RF circuitry,

c) providing a second antenna portion (30) comprising

- providing an elongated second radiating element (32,34) and an electrically conductive tubular element (36,38), and

inserting said elongated second radiating element (32,34) into said tubular element (36,38), and d) mounting said second antenna portion (30) in said recess ( 12a, 12b, 12c) , whereby said tubular element (36,38) contacts said first radiating element (22).

18. The method according to claim 17, wherein step d) is effected by means of a click-in function.