GB2363001A

GB2363001A - Radio antenna coupler

Info

Publication number: GB2363001A
Application number: GB0013374A
Authority: GB
Inventors: Moshe Einat; Rami Abramowitz; Gadi Shirazi
Original assignee: Motorola Israel Ltd
Current assignee: Motorola Solutions Israel Ltd
Priority date: 2000-06-02
Filing date: 2000-06-02
Publication date: 2001-12-05
Anticipated expiration: 2020-06-02
Also published as: GB2363001B; GB0013374D0

Abstract

A radio antenna coupler (100) for a radio device (104) having an antenna (110), the coupler comprising: a conductive plane (102); an RF coupling element (108) connected to the conductive plane for coupling radio signals from the antenna; and the radio device being located at a position in which the antenna is positioned adjacent the RF coupling element, and the radio device extends substantially parallel with the conductive plane for a distance (<I>L</I>) from the antenna's base substantially equal to one quarter of the operating wavelength of the radio device, thereby to form therewith a short-circuited transmission line so as to provide contact-less ground connection. This provides good ground plane radio antenna coupling without requiring a conductive ground plane connection.

Description

2363001 RADIO ANTENNA COUPLER

Field of the Invention

This invention relates to radio antenna couplers. Radio antenna couplers are used to couple signals from a radio unit, such as a cellular telephone, to an external antenna, such as may be mounted on the exterior of a motor vehicle.

Background of the Invention

In the field of this invention it is known, in many radio units such as cellular telephones, for a radio frequency (RF) ground contact to be placed near an antenna base for the use of an RF coupler. The coupler, which is installed in a vehicle adapter, for example, typically needs this

RF ground to couple the maximum possible RF energy from the antenna, and transfer it to an external port such as a vehicle roof antenna. However, in certain radios that originally were not designed to have a RF ground contact for a vehicle adapter RF coupler, there is a later demand for a vehicular adapter that contains an RF coupler.

One solution to the problem can sometimes be to replace a certain part of the radio with a new part that contains the ground contact. This solution involves a change in a part of the radio when installing the vehicle adapter, and often will require a major change in the radio design.

Another solution is to use an RF structure without a common ground between the coupler and the radio. However, such a solution is hard to design and likely to achieve poor coupling results.

is therefore a challenge for the designer to provide an RF ground connection to the radio ground for the coupler without a direct contact to the radio, and 10 without changing the radio design.

It is an object of the present invention to provide a radio antenna coupler wherein the abovementioned disadvantage(s) may be alleviated.

Summary of the Invention

In accordance with a first aspect of the invention there is provided a radio antenna coupler as claimed in claim 1.

In accordance with a second aspect of the invention there is provided a method of coupling a radio antenna as claimed in claim 5.

Brief Description of the Drawings

One radio antenna coupling arrangement incorporating the present invention will now be described described, by way of example only, with reference to the accompanying drawing, in which:

FIG. 1 shows a schematic cross-section of the antenna coupling arrangement.

Description of Preferred Embodiment(s)

Referring now to FIG. 1, an RF antenna vehicular coupling arrangement 100 includes a conductive plane 102. The conductive plane 102 is arranged to be positioned near to, but not in conductive contact with, a radio 104 such as a cellular telephone. When the radio 104 is brought into position to be coupled to the conductive plane 102, the plane 102 is located beneath the radio, covering most of its width and about half of its length. The position of the radio 104 relative to the ground plane 102 is conveniently determined by a non-conductive bracket 106 which is fixed to the ground plane 102 and in which the radio 104 appropriately locates.

The conductive plane is also provided with a coupling element 108 such as an inductor (see, for example, 25 GB patent application no. 9918966.4, in the name of Motorola) or a capacitor (see, for example, US patent no. 5, 668,561, also in the name of Motorola). The coupling element 108 is conductively connected to the adjacent the base of the radio's radio 104 is brought into its shown in FIG. 1.

plane 102 at a point antenna 110 when the coupling position as As can be seen in FIG. 1, when the radio 104 is brought into its coupling position, the plane, together with the electrically conductive chassis of the radio, forms a parallel-plate transmission line structure with an "open" end 112. The distance L from the base of the antenna 110 to the "open" end 112 of the conductive plane is set to be:

L = Y4 A where A is the wavelength of the RF radiation. This results in the "open circuit" at the end 112 being reflected to a "short circuit" after an electrical path of length of Y4A. Accordingly, the base of the antenna effectively connected to the conductive plane. In the present example, with the radio 104 having an operating frequency of some 800 MHz, the path length L is approximately 9 cm.

In this way, a good connection between the radio chassis and the coupler ground plane is achieved without direct contact.

The contact-less ground plane 102 thus becomes a part of the coupler and the coupling element 108 (which can be capacitive or inductive) can operate with the presence of a relatively good ground plane.

Although this method of contact-less ground plane coupling has been described in the context of a cellular telephone, it will be understood that it is not limited to use with cellular telephones, and could alternatively be used with any radio (such as, for example, an iDEN (registered trade mark) radio tranceiver as sold by Motorola) requiring RF coupling.

In summary it will be understood that the present invention provides good ground plane radio antenna coupling without requiring a conductive ground plan connection.

1 -6

Claims

Claim (s)

A radio antenna coupler for a radio device having an antenna, the coupler comprising:

ground plane means having a conductive plane; radio frequency (RF) coupling means connected to the ground plane means for coupling radio signals from the antenna of the radio device; and means for receiving the radio device at a position in which:

the antenna of the radio device is positioned adjacent the RF coupling means, and the radio device extends substantially parallel with the conductive ground plane for a distance from the antenna's base substantially equal to one quarter of the operating wavelength of the radio device, thereby to form therewith a short-circuited transmission line so as to provide contact-less ground connection.
2. The radio antenna coupler according to claim 1 wherein the coupler is a vehicle adaptor RF coupler.
3. The radio antenna coupler according to claim 1 or 2 wherein the radio device comprises a cellular telephone.
4. The radio antenna coupler according to claim 1, 2 or 3 wherein the RF coupling means comprises inductive coupling means.
5. The radio antenna coupler according to claim 1, 2 or 3 wherein the RF coupling means comprises capacitive coupling means.
6. A method of coupling a radio device having an antenna, the method comprising: providing a conductive plane; providing radio frequency (RF) coupling means connected to the conductive plane for coupling RF signals from the antenna of the radio device; and positioning the radio device at a position relative to the conductive plane in which: the antenna of the radio device is positioned adjacent the RF coupling means, and the radio device extends substantially parallel with the conductive plane for a distance from the antenna's base substantially equal to one quarter of the operating wavelength of the radio device, thereby to form therewith a short-circuited transmission line so as to provide contact-less ground connection.
7. The method according to claim 6 wherein the step of providing radio frequency (RF) coupling means includes coupling RF signals from the antenna of the radio device to a device of a vehicle.
8. The method according to claim 6 or 7 wherein the radio device comprises a cellular telephone.
9. The method according to claim 6, 7 or 8 wherein the RF coupling means comprises inductive coupling means.
10. The method according to claim 6, 7 or 8 wherein the RF coupling means comprises capacitive coupling means.
11. A radio antenna coupler substantially as hereinbefore described with reference to the accompanying drawing.
12. A method of coupling a radio device substantially as hereinbefore described with reference to the accompanying drawing.