GB2370724A

GB2370724A - Diversity antennae for personal wireless communications apparatus

Info

Publication number: GB2370724A
Application number: GB0031359A
Authority: GB
Inventors: Thomas Keller; Jason Woodard
Original assignee: Ubinetics Ltd
Current assignee: Aeroflex Cambridge Ltd
Priority date: 2000-12-21
Filing date: 2000-12-21
Publication date: 2002-07-03
Anticipated expiration: 2020-12-21
Also published as: GB2370724B; GB0031359D0

Abstract

A personal wireless communications device such as a video phone comprises a number of separate units 12, 18, 24 communicating via cables 14, 16. The distributed nature of the device is used to place antennae 28, 30, 32 in the separate units to provide diversity reception and transmission. Signals received by the three antennae can be combined to form a better quality signal. The antennae can be used for beam steering of signals transmitted from the device. Antennae can additionally or alternatively be located in the cables 14, 16.

Description

PERSONAL WIRELESS COMMUNICATIONS APPARATUS The invention relates to a personal wireless communications apparatus. In particular, it relates to the reception and transmission of wireless signals using such apparatus. The mobile telephone is an example of a conventional personal wireless communications device. Mobile telephones are known to experience the phenomenon of fading.

Fading is caused by multi-path propagation of radio signals to a receiver. The signal components arriving at a receiver via different paths have phase differences relative to one another. Therefore, the multi-path components interfere at the receiver. The relative phase differences of the components depends upon the position of the receiver. If the receiver moves, then the way in which the multi-path components combine at the receiver changes, consequentially changing the interference pattern at the receiver. For example, when a mobile telephone is moved, it passes through nodes where the multi-path components bind, substantially in phase, thus providing a relatively high amplitude signal for reception by the mobile telephone. The mobile telephone will also move through nodes of destructive interference, where the multi-path components combine substantially out of phase, with the result that the received signal amplitude is low. As the mobile telephone is moved, it will pass from a destructive node to a constructive node and thence back to a destructive node, and so on. The distance between a node of constructive interference and an adjacent node of destructive interference is of the order of one half of the wavelength of the signals being received, which, for current telecommunications technology, means that the nodes are separated by a distance of the order of 1 Ocm where such conditions of interference arise, it can be frustrating for user of a mobile telephone to hold the telephone's antenna in position within a constructive node for the duration of a call.

One object of the invention is to provide improved personal wireless communications apparatus.

According to one aspect, the invention provides a distributed, personal wireless communications device comprising a plurality of antennas, said antennas exploiting the distributed nature of the device by being dispersed around the device to enhance the device's transmission and/or reception abilities.

Since the antennas are dispersed, there is a smaller chance that they will all be located within the same destructive node, and hence the reception of signals is enhanced overall.

Since the antennas are dispersed, they can be employed to direct the transmission of signals away from the device, thus raising the possibility of lowering the power needed for the transmission of those signals to reach their destination.

The wireless communications device according to the invention is a distributed personal wireless communications device, rather than a compact unitary device such as a conventional mobile telephone.

The distributed personal wireless communications device may be a plurality of separate, intercommunicating units and one of the antennas may be located in the unit and at least one other antenna may be located elsewhere. Thus, the dispersal of antennas may be achieved by, for example, providing the antennas in different units.

The distributed wireless communications device may be a plurality of separate intercommunicating units, at least two of which are cabled together, and one of the antennas may be located in the cable and at least one other antenna may be located elsewhere. In this way, the cables between the units are exploited in the dispersal of the antennas.

Preferably, the antennas are arranged in the device to facilitate their exploitation by the device for transmitting signals with a desired directional bias. For example, the device can use the antennas for"beam steering"of the signals transmitted from the device.

Preferably, the antennas are arranged in the device to ameliorate fading problems in the signals received by the device. At least two of the antennas in the device may be arranged in a spatially diverse relationship, such that they are unlikely to be situated within the same node of destructive interference. At least two of the antennas are separated by more than half a wavelength of the signals being received and/or transmitted.

By way of example only, an embodiment of the invention will now be described, with reference to the accompanying drawing, which is a block diagram of a personal wireless communications device (a video phone).

The video phone 10 of Figure 1 comprises a central unit 12 linked by cable 14 to a visual interface and linked by cable 16 to an audio interface.

The central unit 12 controls the operation of the visual and audio interfaces via respective cables 14 and 16. The central unit 12 processes wireless signals received by the video phone 10 and outputs visual and audio information extracted from the received signals to the visual and audio interfaces respectively. The central unit 12 also processes visual and audio inputs providing to the visual and audio interfaces respectively and modulates these inputs onto signals which are transmitted from the video phone 10.

The visual interface comprises a visual unit 18 which comprises a camera 20 and a display 22. The display 22 provides the visual output from the central unit 12 in the form of images. For example, display 22 could show the image of a person engaged in a call with the user of video phone 10 or it could display a graphical user interface. The camera 20 provides images of its field of view as visual input to the video phone which the central unit 12 includes in its transmissions.

The audio interface comprises an earpiece 24 connected to the end of cable 16 and a microphone bead 26 provided on cable 16 at a point intermediate the earpiece 24 and the central unit 12. The earpiece 24 contains a loudspeaker which relays to a user audio output which the central unit has decoded from received wireless signals. The microphone bead 26 detects sounds such as user utterences and supplies them to the central unit 12 as audio input for transmission from the video phone 10. The video phone 10 has a distributed nature comprising four units interconnected via flexible cables. This facilitates the use of the video phone 10 by a user since the audio and visual interfaces may easily be located by the user for ease of use.

The video phone 10 contains three antennae 28,30 and 32 which are located in the visual unit 18 the central unit 12 and the earpiece 24 respectively. The antennae 28,30 and 32 are dispersed through the video phone 10 so as to take advantage of the video phone's distributed nature. When the video phone 10 is arranged by a user for use, each of the antennae 28,30 and 32 is separated from the others by more than one half of a wavelength of the signals being received by the video phone 10. This means that the antennae 28, 30 and 32 are spatially diverse, and unlikely to all be situated within a node of destructive interference. Thus, by combining the signals received from the three antennae 28,30 and 32, the control unit is able to recover a received signal of sufficient quality a majority of the time. The control unit 12 can also use the dispersed antennas 28,30 and 32 to give a directional bias to the signals transmitted from the video phone 10. For example, by adjusting the relative phases of the signals supplied to the antenna, the control unit 12 can arrange that the video phone 10 transmits signals in a preferred direction.

In an alternative embodiment, antennae can be located in the cables 14 and 16 in order to achieve the dispersal of the antennae. This may be in addition to, or instead of, providing antenna within the units of the video phone 10.

Claims

CLAIMS 1. A distributed personal wireless communications device comprising a plurality of antennae, said antennae exploiting the distributed nature of the device by being dispersed around the device to enhance the device's transmission and/or reception abilities.
2. A device according to claim 1, comprising a plurality of separate intercommunicating units and wherein one of the antennae is located in a unit and at least one other antennae is located elsewhere.
3. A device according to claim I or 2, wherein the device comprises a plurality of separate intercommunicating units, at least two of which are cabled together, and one of the antennae is located in the cable and at least one other antennae is located elsewhere.
4. A device according to any preceding claim, wherein the antennae are arranged in the device to facilitate their exploitation by the device for transmitting signals with a desired directional bias.
5. A device according to any preceding claim, wherein the antennae are arranged in the device to ameliorate the effects of interference on signals received by the device.
6. A device according to any preceding claim, wherein at least two of the antennae are arranged in a spatially diverse relationship.
7. A device according to any preceding claim, wherein at least two of the antennae are separated by more than one half of a wavelength of the signals being received and/or transmitted.
8. A distributed personal wireless communications device, substantially as hereinbefore described with reference to Figure 1.