WO2009072974A1

WO2009072974A1 - Antenna device, portable radio communication apparatus, and manufacturing methods thereof

Info

Publication number: WO2009072974A1
Application number: PCT/SE2008/051399
Authority: WO
Inventors: Greger BYSTRÖM; Rickard Sundin; Patrik STRÖMHOLM
Original assignee: Laird Technologies Ab
Priority date: 2007-12-07
Filing date: 2008-12-03
Publication date: 2009-06-11

Abstract

An antenna device (31) for use in a portable radio communication apparatus comprises a dielectric substrate (21) having a main surface, and an electrically conductive antenna (11) arranged on the main surface of the substrate, wherein the main surface of the substrate includes first protruding members (23) and the antenna rests on the first protruding members thereby defining an air gap of a well-defined thickness between the antenna and the main surface of the substrate.

Description

ANTENNA DEVICE, PORTABLE RADIO COMMUNICATION APPARATUS, AND MANUFACTURING METHODS THEREOF

FIELD OF THE INVENTION

The present invention relates generally to the field of radio communications and particularly to antenna devices for use in portable radio communication apparatuses, to such portable radio communication apparatuses, and to manufacturing methods of such antenna devices and portable radio communication apparatuses .

BACKGROUND OF THE INVENTION AND RELATED ART

Mobile phones are subject to cost reduction demands as well as increasing adaptation for large scale manufacturing. For that reason parts included in a mobile phone are preferably designed to ensure low manufacturing and assembling costs.

According to one prior art technique for manufacturing of an antenna device for mobile phones an electrically conductive antenna is formed by punching a sheet metal. An additional step may be required for punching holes in the antenna which are required for the assembly of the antenna device. A dielectric substrate is formed e.g. by molding wherein the dielectric substrate includes taps in a surface, the positions of which correspond to the positions of the punched holes of the antenna. The antenna is arranged on the surface of the dielectric substrate such that the punched holes receive the taps, and the antenna is welded to the dielectric substrate at each of the taps/punched holes by means of ultra sonic welding. In the ideal case the antenna sheet metal is lying close to the surface of the dielectric substrate.

SUMMARY OF THE INVENTION

A problem of the described prior art manufacturing technique is that the assembling requires ultra sonic welding which adds cost and complexity.

Further, it may require the additional step of punching holes in the antenna pattern.

Still further, the ultra sonic welding is an inexact assembling technique which may not to a very high extent keep the permissible manufacturing tolerances. In particular, if the antenna of the assembled antenna device does not lie up against the dielectric substrate, that is, an unwanted air gap of e.g. 0.1 mm is obtained between the antenna and the substrate, the dielectric constant will be altered in the close vicinity of the antenna and as a result the resonance frequency of the antenna device will be altered. For the higher frequency GSM bands, the resonance frequency may vary up to 15 MHz, which is unacceptable. Consequently, each antenna device has to be tested after assembly thereof and such operation and costs. Further, the manufacturing yield may be unacceptable low, especially for the manufacture of low cost antenna devices for use in low cost mobile phones.

An object of the present invention is therefore to provide an antenna device for use in a portable radio communication device, which lacks or at least alleviates the above described shortcomings. A particular object of the invention is to provide an antenna device which is of low cost and which is easy and inexpensive to manufacture and assemble.

A still further object of the invention is to provide a portable radio communication apparatus, such as e.g. a mobile telephone, comprising an antenna device fulfilling any of the above objects.

Yet a further object of the invention is to provide a manufacturing method for an antenna device, which is of low cost and by which testing of assembled antenna devices can be avoided due to larger tolerance in the manufacturing without affecting the performance negatively.

These objects, among others, are according to the present invention attained by antenna devices, portable radio communication apparatus, and methods as defined in the appended patent claims.

An antenna device for use in a portable radio communication apparatus comprises a dielectric substrate having a main surface, and an electrically conductive antenna arranged on the main surface of the substrate. The main surface of the substrate includes according to the invention first protruding members, and the antenna rests on the first protruding members, thereby defining an air gap of a well-defined thickness between the antenna and the main surface of the substrate .

The air gap may typically be 0.4 mm thick and by adapting the antenna pattern to such a modified dielectric environment, the sensitivity of the resonance frequency response to variation in air gap between the antenna and the substrate will be much smaller than for the antenna device of the prior art. This is due to the fact that air has a much smaller dielectric constant than the typical plastic material of the substrate, and hence the resonance frequency is less affected by increasing the air gap thickness from 0.4 mm to 0.5 mm than from 0 to 0.1 mm.

If the antenna is a monopole type of antenna the length of the antenna will be slightly longer in the antenna device of the invention due to the desired air gap of a controlled thickness.

Advantages of the present invention include inter alia easier and faster manufacture and assembly of a robust antenna device with less manufacturing steps and to a lower cost, less influence on the resonance frequency of inaccurately assembled antenna device, larger manufacturing tolerances, and no need for testing the assembled antenna devices.

Further characteristics of the invention and advantages thereof will be evident from the following detailed description of embodiments of the invention.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will become better understood from the detailed description of embodiments of the present invention given hereinbelow and the accompanying Figs. 1-3, which are given by way of illustration only and thus, are not limitative of the present invention. Fig. 1 illustrates, schematically, in a perspective view, an electrically conductive antenna as being comprised in an antenna device according to a first embodiment of the present invention.

Fig. 2 illustrates, schematically, in a perspective view, a dielectric substrate as being comprised in the antenna device according to the first embodiment of the invention .

Fig. 3 illustrates, schematically, in a perspective view, the antenna device according to the first embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of an antenna device for use in a low cost portable radio communication apparatus according to the present invention will now be described with reference to Figs. 1-3. The antenna device 31 (illustrated assembled in Fig. 3) comprises an electrically conductive antenna 11 (illustrated separately in Fig. 1) and a dielectric substrate 21 (illustrated separately in Fig. 2) .

The antenna 11 is preferably punched from sheet metal and comprises one or more radiating elements and optionally parasitic elements in order to radiate in one or more radio frequency bands. Typically, the radiating elements are of monopole type. The antenna comprises hooks 13 or similar for attachment purposes and a contact region 15 to be connected to radio frequency circuitry of the portable radio communication apparatus into which it is mounted. The substrate 21 is of a suitable dielectric material such as a plastic, which is formed to a suitable shape by e.g. molding. The substrate 21 has a main surface in which first protruding members 23 are arranged. The first protruding members 23 are realized in the form of a number of ridges extending transverse to a longitudinal direction of the substrate 21, preferably along the entire width of the substrate 21 or at least along a major portion thereof. While assembled, the antenna 11 rests on the ridges 23 of the substrate 21, thereby defining an air gap of a well-defined thickness between the antenna 11 and the main surface of the substrate 21.

The controlled space or clearance between the radiator and the carrier makes the antenna device less sensitive for gap variations and process tolerances.

Further, second protruding members 25 are arranged in the main surface of the substrate 21 for holding the antenna 11 in a lateral direction transverse to the longitudinal direction of the substrate 21. The second protruding members 25 are realized in the form of a number of taps or walls that are adapted to the pattern of the antenna 11 so as to hold the various parts of the antenna (e.g. different radiating elements) in position in the lateral direction transverse to the longitudinal direction of the substrate 21.

As can be seen to the left in Fig. 2 first and second protruding members 23, 25 can be arranged at the same longitudinal position of the substrate 21. The substrate 21 comprises also holes 27 and/or edges 29 which engage with the hooks 13 of the antenna 11 while assembled in a snap-in mechanism.

In Figs. 1-3 the antenna comprises four hooks 13 which engage with holes 25/edges 27, but in the general case the antenna is attached to the substrate 21 at two different positions as a minimum.

The antenna 11 is preferably pressed against the first protruding members 23 by means of being assembled with in-built compressive, tensile or bending stresses. To this end the antenna is flexible and is at rest shaped differently than the main surface of the substrate 21. If the main surface of the substrate 21 is convex in the longitudinal direction, the antenna may be planar or have a convex shape in the same direction with a larger radius than that of the main surface of the substrate 21. It shall be noted that the main surface may be of virtually any shape. For instance, it may be convex in one or two lateral directions, it may be concave in one or two lateral directions, or it may be essentially planar.

If the main surface of the substrate 21 is planar, the antenna may be concave in the longitudinal direction.

It shall be appreciated that while the dielectric substrate 21 is illustrated as being of similar size, the substrate may be much larger and carry other components of a portable radio communication apparatus.

In one embodiment the dielectric substrate is the main chassis of the portable radio communication apparatus and in another embodiment the dielectric substrate is a back or front cover of the portable radio communication apparatus, in which embodiment the main surface on which the antenna is mounted is the interior surface of the cover.

A further embodiment of the invention encompasses a portable radio communication apparatus comprising any of the antenna devices disclosed above.

A manufacturing method of the antenna device 31 according to a further embodiment of the invention comprises the following steps:

(i) providing a dielectric substrate 21 having a main surface which includes first protruding members 23;

(ii) providing an electrically conductive antenna 11; and

(iϋ) assembling the antenna 11 and the substrate 21 so that the antenna 11 rests on the first protruding members 23 of the main surface of the substrate 21, thereby defining an air gap of a well-defined thickness between the antenna 11 and the main surface of the substrate 21.

Preferably, the antenna device 31 is assembled by means of a snap-in mechanism only. Hence, no expensive equipment for assembly such as ultra sonic welders is required.

However, in alternative embodiments other attachments methods may be used such as e.g. ultra sonic welding. If ultra sonic welding is used the manufacturing will, however, be more complex and costly. If the main surface of the substrate 21 comprises second protruding members 25 for holding the antenna 11 in a lateral direction transverse to a longitudinal direction of the substrate 21, the assembling step may comprise the following step:

- arranging the antenna 11 or a part thereof in between the second protruding members 25.

It shall be appreciated that an antenna device manufactured according to the above method has a very low variation in resonance frequency also at moderate process tolerances. Hereby, testing of the assembled antenna devices may not be necessary.

The assembly can be fully automatic in a stamping process line.

The manufacturing method minimizes the number of antenna device parts required and the number of assembling steps required.

Embodiments of an antenna device 31 according to the invention have been described. The person skilled in the art realizes that such embodiments can be varied within the scope of the appended claims. Particularly, the shapes of the different parts shown in the Figures can be adapted to different needs, uses and applications. In particular, the antenna pattern can have virtually any shape depending on the applications in which the antenna device 31 is to be used.

Claims

1. An antenna device (31) for use in a portable radio communication apparatus, said antenna device comprising

- a dielectric substrate (21) having a main surface; and

- an electrically conductive antenna (11) arranged on the main surface of said substrate, characterized in that

- the main surface of said substrate includes first protruding members (23) ; and

- said antenna rests on said first protruding members thereby defining an air gap of a well-defined thickness between said antenna and the main surface of said substrate .

2. The antenna device of claim 1 wherein said first protruding members comprises a number of ridges extending transverse to a longitudinal direction of said substrate.

3. The antenna device of claim 1 or 2 wherein said antenna is attached to said substrate at at least two different positions.

4. The antenna device of claim 3 wherein said antenna is pressed against said first protruding members by means of being assembled with in-built tensile or bending stresses.

5. The antenna device of any of claims 1-4 wherein the main surface of said substrate comprises second protruding members (25) for holding the antenna in a lateral direction transverse to a longitudinal direction of said substrate.

6. The antenna device of any of claims 1-5 wherein said antenna is attached to said substrate by means of a snap-in mechanism.

7. The antenna device of any of claims 1-6 wherein said antenna comprises hooks (13) and said substrate comprises holes (27) or edges (29) which engage with said hooks.

8. The antenna device of any of claims 1-7 wherein the main surface of said substrate is convex in at least one lateral direction.

9. The antenna device of any of claims 1-7 wherein the main surface of said substrate is planar or concave in at least one lateral direction.

10. The antenna device of any of claims 1-9 wherein said antenna is of monopole type.

11. The antenna device of any of claims 1-10 wherein said antenna is a dual or triple band antenna.

12. A portable radio communication apparatus comprising the antenna device as claimed in any of claims 1-11.

13. A manufacturing method of an antenna device (31) comprising the steps of: - providing a dielectric substrate (21) having a main surface which includes first protruding members (23); and

- providing an electrically conductive antenna (11); characterized by:

- assembling said antenna and said substrate so that said antenna rests on said first protruding members of the main surface of said substrate, thereby defining an air gap of a well-defined thickness between said antenna and the main surface of said substrate.

14. The method of claim 13 wherein said antenna and said substrate are assembled by means of a snap-in mechanism only.

15. The method of claim 13 or 14 wherein the main surface of said substrate comprises second protruding members (25) for holding the antenna in a lateral direction transverse to a longitudinal direction of said substrate, and the method comprises the step of arranging said antenna or part thereof in between said second protruding members.

16. A manufacturing method of a portable radio communication apparatus comprising the manufacturing method of any of claims 13-15.