WO1999065105A1

WO1999065105A1 - Apparatus and method for aligning a transmitter and a receiver

Info

Publication number: WO1999065105A1
Application number: PCT/GB1999/001802
Authority: WO
Inventors: Ian Andrew Murphy
Original assignee: Radiant Networks Plc
Priority date: 1998-06-09
Filing date: 1999-06-08
Publication date: 1999-12-16
Also published as: GB9812431D0

Abstract

Apparatus and a method are provided for aligning an antenna of a transmitter (13) with an antenna of a receiver (13). A first viewer (21) is associated with the transmitter (13) for viewing a target on the receiver (13) along a viewing axis (23) of the first viewer (21). A second viewer (21) is associated with the receiver (13) for viewing a target on the transmitter (13) along a viewing axis (23) of the second viewer (21). The first and second viewers (21) are arranged relative to the transmitter (13) and the receiver (13) such that the receiver (13) is oriented to receive substantially directional wireless transmissions from the transmitter (13) when the second viewer (21) views a target on the transmitter (13) and the first viewer (21) views a target on the receiver (13).

Description

APPARATUS AND METHOD FOR ALIGNING A TRANSMITTER AND A RECEIVER

The present invention relates to an apparatus and a method for aligning a transmitter and a receiver.

When designing and building a communications network which uses wireless transmissions for the transmission of data from one node to another, it is essential to obtain a good understanding of the nature of the propagation paths which are likely to be encountered for the wireless transmissions. This is conventionally carried out using a "channel sounder" . A channel sounder typically consists of a transmission system and a receiving system. The transmission system repeatedly sends known data sequences, for example a pseudo-random byte sequence, over the appropriate radio channel to the receiving system. The receiving system receives transmitted signals and attempts to reconstruct the original transmitted data sequence. The ease with which this process can be carried out by the receiving system and the quality of the resulting decoded information can be used to provide information about the nature of the wireless transmission path between the transmitting system and the receiving system.

In our International patent application no. PCT/GB97/03472 and our British patent application no. 9726873.4, the entire disclosures of which are incorporated herein by reference, there is disclosed a communications apparatus comprising a mesh of interconnected nodes.

It has been proposed to use wireless transmissions at a frequency of at least 1 GHz for the communications network. The frequency used may be for example 2.4 GHz or 4 GHz or even higher frequencies such as 40 GHz, 60 GHz, 200 GHz or higher. The channel sounding should be carried out at these frequencies with a transmission system and a receiving system which have operating characteristics which approximate closely to those of the transceiver and receiver which will be used at a node in practice. The transmitter and receiver antennae for the nodes of the communications network will typically be microwave antennae horns with high gain with highly directional and collimated beams. The antennae horns will typically be positioned in urban, suburban and rural environments at heights of less than 10 to 15m above local ground level with an inter-node spacing of up to 5km. These conditions make it difficult to align a transmitter of one node with a receiver of another node. This problem is exacerbated by adverse weather conditions such as haze, fog, rain and snow as it can be very difficult to see one node from another and even more difficult to locate a microwave horn at a node over such distances. It will be appreciated that a very small error in alignment of a receiver of one node with a transmitter of another node may mean that no signal at all or only an extremely weak signal will actually be received at the receiver.

According to a first aspect of the present invention, there is provided apparatus for aligning an antenna of a transmitter with an antenna of a receiver, the apparatus comprising: a transmitter having an antenna for transmitting a substantially directional wireless transmission along a transmission axis of the transmitter; a receiver having an antenna for receiving a substantially directional wireless transmission from the transmitter along a receiving axis of the receiver; a first viewer associated with the transmitter for viewing a target on the receiver along a viewing axis of the first viewer; a second viewer associated with the receiver for viewing a target on the transmitter along a viewing axis of the second viewer; the first and second viewers being arranged relative to the transmitter and the receiver such that the receiver is oriented to receive substantially directional wireless transmissions from the transmitter when the second viewer views a target on the transmitter and the first viewer views a target on the receiver.

Thus, the transmitter and the receiver can be aligned in a very quick and simple manner as a person merely has to line up the viewers with their targets to automatically align the transmitter and the receiver. The alignment can be carried out by an unskilled user if necessary. Adjustment of the alignment, and location of and alignment with an alternative transmitter or receiver, can be accomplished very easily and accurately.

The viewing axis of the transmitter is preferably substantially parallel to the transmission axis of the transmitter and the viewing axis of the receiver is preferably substantially parallel to the receiving axis of the receiver. This facilitates alignment of the transmitter and the receiver.

Each viewer may be an optical viewer for viewing a target in the visible spectrum.

Each viewer preferably comprises a camera. It will be understood that a "camera" includes any device which can view an image and relay the image to a remote display device where the image can be displayed. Thus, there is preferably provided a display screen for each of the transmitter and the receiver for displaying an image viewed by the camera associated with said transmitter and receiver.

Each target at the transmitter and the receiver may conveniently be the viewer associated with said transmitter and receiver. Thus, alignment of the transmitter and the receiver can be achieved by simply viewing the first viewer with the second viewer and vice versa. Each viewer is preferably mounted on a pan-tilt mechanism whereby the viewer can be selectively panned and tilted.

The apparatus preferably includes a remote controller for remotely controlling movement of the viewer.

According to a second aspect of the present invention, there is provided apparatus for aligning a receiver with a transmitter, the apparatus comprising: a receiver for receiving a substantially directional wireless transmission from a directional transmitter along a receiving axis of the receiver; and, a viewer for viewing a target on a transmitter along a viewing axis of the viewer, said viewing axis being arranged relative to the receiving axis of the receiver such that the receiver is oriented to receive substantially directional wireless transmissions from a directional transmitter when the viewer views a target on a said transmitter.

The viewing axis is preferably substantially parallel to the receiving axis.

The viewer may be an optical viewer for viewing a target in the visible spectrum.

The viewer preferably comprises a camera.

The apparatus preferably comprises a display screen for the receiver for displaying an image viewed by the camera.

The apparatus may comprise a transmitter, wherein the target at the transmitter is a viewer associated with said transmitter. The viewer is preferably mounted on a pan-tilt mechanism whereby the viewer can be selectively panned and tilted.

The apparatus preferably comprises a remote controller for remotely controlling movement of the viewer.

According to a third aspect of the present invention, there is provided a method of aligning an antenna of a transmitter with an antenna of a receiver, the transmitter having an antenna for transmitting a substantially directional wireless transmission along a transmission axis of the transmitter; the receiver having an antenna for receiving a substantially directional wireless transmission from the transmitter along a receiving axis of the receiver; there being a first viewer associated with the transmitter for viewing a target on the receiver along a viewing axis of the first viewer and a second viewer associated with the receiver for viewing a target on the transmitter along a viewing axis of the second viewer; the method comprising the steps of: remotely controlling the orientation of the second viewer to view a target on the transmitter with the second viewer and remotely controlling the orientation of the first viewer to view a target on the receiver with the first viewer, thereby orienting the transmitter and the receiver such that the receiver is oriented to receive substantially directional wireless transmissions from the transmitter.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a side elevation of a portion of an example of apparatus according to the present invention with some parts cut away for clarity; and, Fig. 2 is a schematic side elevation of two transceivers connected by a wireless transmission link.

Referring to the drawings, there is shown a first node 10 and a second node 11 which may form part of a communications apparatus comprising a plurality of such nodes. A node 10,11 will typically be associated with a user of or subscriber to the communications apparatus. Each node 10 has a radio transceiver subsystem 12 which is connected to a transmitter/receiver (transceiver) unit 13 which is in turn mounted on top of a tall structure such as a mast 14, a rooftop, etc. Signals for transmission are generated by the radio subsystem 12 and mixed with a carrier frequency signal for transmission by the transmitter part of the transceiver 13. Similarly, signals received by the receiver part of the transceiver 13 are down converted to an intermediate frequency (IF) signal and sent to the radio subsystem 12.

The signals actually transmitted by the transceiver 13 are highly directional and collimated and will typically have a carrier frequency greater than 1 GHz . The carrier frequency might be for example 2.4 GHz, 4 GHz, 40 GHz, 60 GHz, 200 GHz or even higher frequencies such as 100,000 GHz. At these frequencies, which are microwave or higher, the transceiver 13 has an antenna in the form of a horn 15 which is arranged to transmit and receive signals along a longitudinal transceiver axis 16 of the horn 15.

The transceiver 13 is mounted via a fixing 17 on a camera housing 18. The camera housing 18 is mounted on a pan-tilt mechanism 19 which is in turn mounted on the top of the mast 14. The pan-tilt mechanism 19 allows the camera housing 18 and the transceiver 13 to be panned (i.e. pivoted or rotated in a horizontal plane) and tilted (in a vertical plane) . The pan-tilt mechanism 19 is controlled remotely from a pan-tilt controller 20 at the node 10, possibly under servo control for accuracy.

The camera housing 18 contains a camera 21 having a lens 22. The optical axis 23 of the camera lens 22 is in this example parallel to the transceiver axis 16 of the horn 15 of the transceiver 13. The lens 22 can be controlled from a computer 24 to move back and forth parallel to the optical axis 23 to vary the zoom or magnification of the camera 21. The camera 21 is preferably operable in at least optical wavelengths. The output of the camera 21 is passed to the camera controller 24 so that the image seen by the camera 21 can be displayed on a display screen of the camera controller 24.

Operation is as follows. A person is situated at each node 10,11 to view the display screen of the camera controller 24 on which the image viewed by the camera 21 is displayed. The person operates the pan-tilt controller 20 at the first node 10 to steer the camera 12 at the first node 10 until an image of the camera 21 at the other node 11 is displayed on the display screen of the pan-tilt controller 24. The person at the second node 11 similarly operates the pan-tilt controller 24 of the second node 11 so that the camera 21 of the first node 10 is viewed through the camera 21 of the second node 11 and displayed on the display screen of the pan-tilt controller 24 of the second node 11. Because the transceiver axes 16 of the horns 15 of the transceivers 13 at the two nodes 10,11 are each respectively parallel to the optical axis 23 of their respective cameras 21, the transceiver axes 16 of the two nodes 10,11 will be coincident when the cameras 21 of each node 10,11 are lined up to view each other. In other words, optically aligning the two cameras 21 inevitably and automatically aligns the transceiver horns 15 of the transceivers 13 of the two nodes 10,11. Bearing in mind chat the separation 25 between the two nodes 10,11 may be for example anything from 5m to 5km or more , it may be difficult in fact to locate one node 10 from the other 11 through the cameras 21, at least initially. To facilitate the location of the cameras 21, a source of light 26 may be mounted on top of each transceiver 13 and operated to flash when alignment is taking place. Furthermore, whilst the cameras 21 will normally use optical wavelengths, infra red wavelengths may be used instead or in addition with appropriate image enhancement being used in the pan-tilt controllers 24 to enable the received image to be viewed on the screen of the pan-tilt controllers 24.

The pan-tilt controllers 24 may incorporate a video interface card to enable the received images to be electronically captured along with the data taken for the channel sounding radio measurements. In this way, a visual log of the environment and ambient weather conditions can accompany the raw data obtained from the channel sounding for use later in subsequent analysis.

It will be appreciated that for simplicity and to keep down manufacturing and installation costs, all of the equipment at each node 10,11 is substantially identical. Thus, the vertical separation between the transceiver axis 16 and the viewing axis 23 is the same at each node 10,11. Accordingly, where the transceiver axis 16 is parallel to the viewing axis 23, a person at a particular node 10,11 needs merely to steer that node's camera 21 so that the camera 21 at the other node 11,10 is in view in order to align the transceiver axes 16 of the two nodes 10,11 to create a point-to-point wireless communications link between the nodes 10,11. In other cases, a camera 21 at a particular node 10 may be arranged so that the transceivers 13 of the respective nodes 10,11 are aligned when the camera 21 views some other target on the other node 11,10; in such a case, the transmission/reception axis 16 need not be precisely parallel to the viewing axis 13 at one or both of the nodes 10,11.

The present invention provides a very simple apparatus and method for aligning a transmitter with a receiver. The apparatus can be so simple to operate that users associated with the nodes 10,11 can set up and align the respective transceivers as necessary themselves and skilled and/or trained personnel are not required to align the transceivers 13 of nodes 10,11 which communicate with each other. The antennae horns 15 can be steered remotely, avoiding the need for manual steering of the antennae horns 15 which would be difficult where the antennae horns 15 are positioned high on a mast or rooftop for example. An electronic viewer, such as a camera, can be used so that the image can be captured thereby providing a record of ambient weather conditions for example for analysis later. Because the viewer can be steered remotely and electronically, its position settings can be stored for analysis and so that the precise position of the viewer can be repeated later if necessary, perhaps following maintenance or replacement of the antennae horn for example .

An embodiment of the present invention has been described with particular reference to the example illustrated. However, it will be appreciated that variations and modifications may be made to the example described within the scope of the present invention.

Claims

1. Apparatus for aligning an antenna of a transmitter with an antenna of a receiver, the apparatus comprising: a transmitter having an antenna for transmitting a substantially directional wireless transmission along a transmission axis of the transmitter; a receiver having an antenna for receiving a substantially directional wireless transmission from the transmitter along a receiving axis of the receiver; a first viewer associated with the transmitter for viewing a target on the receiver along a viewing axis of the first viewer; a second viewer associated with the receiver for viewing a target on the transmitter along a viewing axis of the second viewer; the first and second viewers being arranged relative to the transmitter and the receiver such that the receiver is oriented to receive substantially directional wireless transmissions from the transmitter when the second viewer views a target on the transmitter and the first viewer views a target on the receiver.

2. Apparatus according to claim 1, wherein the viewing axis of the transmitter is substantially parallel to the transmission axis of the transmitter and the viewing axis of the receiver is substantially parallel to the receiving axis of the receiver.

3. Apparatus according to claim 1 or claim 2, wherein each viewer is an optical viewer for viewing a target in the visible spectrum.

4. Apparatus according to any of claims 1 to 3 , wherein each viewer comprises a camera.

5. Apparatus according to claim 4, comprising a display screen for each of the transmitter and the receiver for displaying an image viewed by the camera associated with said transmitter and receiver.

6. Apparatus according to any of claims 1 to 5 , wherein each target at the transmitter and the receiver is the viewer associated with said transmitter and receiver.

7. Apparatus according to any of claims 1 to 6, wherein each viewer is mounted on a pan-tilt mechanism whereby the viewer can be selectively panned and tilted.

8. Apparatus according to any of claims 1 to 7, comprising a remote controller for remotely controlling movement of the viewer.

9. Apparatus for aligning a receiver with a transmitter, the apparatus comprising: a receiver for receiving a substantially directional wireless transmission from a directional transmitter along a receiving axis of the receiver; and, a viewer for viewing a target on a transmitter along a viewing axis of the viewer, said viewing axis being arranged relative to the receiving axis of the receiver such that the receiver is oriented to receive substantially directional wireless transmissions from a directional transmitter when the viewer views a target on a said transmitter.

10. Apparatus according to claim 9, wherein the viewing axis is substantially parallel to the receiving axis.

11. Apparatus according to claim 9 or claim 10, wherein the viewer is an optical viewer for viewing a target in the visible spectrum.

12. Apparatus according to any of claims 9 to 11, wherein the viewer comprises a camera.

13. Apparatus according to claim 12, comprising a display screen for the receiver for displaying an image viewed by the camera .

14. Apparatus according to any of claims 9 to 13, comprising a transmitter, wherein the target at the transmitter is a viewer associated with said transmitter.

15. Apparatus according to any of claims 9 to 14, wherein the viewer is mounted on a pan-tilt mechanism whereby the viewer can be selectively panned and tilted.

16. Apparatus according to claim 15, comprising a remote controller for remotely controlling movement of the viewer.

17. A method of aligning an antenna of a transmitter with an antenna of a receiver, the transmitter having an antenna for transmitting a substantially directional wireless transmission along a transmission axis of the transmitter; the receiver having an antenna for receiving a substantially directional wireless transmission from the transmitter along a receiving axis of the receiver; there being a first viewer associated with the transmitter for viewing a target on the receiver along a viewing axis of the first viewer and a second viewer associated with the receiver for viewing a target on the transmitter along a viewing axis of the second viewer; the method comprising the steps of : remotely controlling the orientation of the second viewer to view a target on the transmitter with the second viewer and remotely controlling the orientation of the first viewer to view a target on the receiver with the first viewer, thereby orienting the transmitter and the receiver such that the receiver is oriented to receive substantially directional wireless transmissions from the transmitter.