WO2006019290A1

WO2006019290A1 - A method for installing an antenna of a satellite receiver on a celestial body, satellite receiver and control unit for such a satellite receiver

Info

Publication number: WO2006019290A1
Application number: PCT/NL2004/000586
Authority: WO
Inventors: Jan Arie Van Houwelingen
Original assignee: Stichting Astron
Priority date: 2004-08-20
Filing date: 2004-08-20
Publication date: 2006-02-23

Abstract

A method for installing a satellite receiver (1) on a celestial body (10). The satellite receiver (1) has a phased array antenna (4), and a receiver memory (52) in which reference data is stored. The data represents at least properties of at least two satellites (21-23) in orbit around the celestial body (10). The properties include satellite identification information and satellite position with respect to the celestial body (10). The method includes (a) pointing the phased array antenna (4) in a pre-determined direction with respect to the celestial body (10); and (b) searching for satellites from which satellite signals can be received by means of the satellite receiver, said searching including: controlling an antenna beam (40) of the phased array antenna (4) such that the phased array antenna (4) scans a part of the sky of the celestial body (10). If a satellite signal is received by the phased array antenna (4) during the searching: (c) receivable satellites are identified in the scanned part of the sky from at least one aspect of the received satellite signal, and the satellite identification information.

Description

Title: A method for installing an antenna of a satellite receiver on a celestial body, satellite receiver and control unit for such a satellite receiver.

The invention relates to a method for installing a satellite receiver. The invention further relates to a satellite receiver, a satellite system and a control unit for use in a satellite receiver.

In the art, satellite receivers with a dish shaped antenna are generally known. These prior art antennas have a dish-shaped reflector which reflects incoming election magnetic radiation to a focal point. In or near the focal point, a receiver device, also known in the art as a Low Noise Block converter (LNB), is disposed which receives and converts the focussed radiation into electrical signals. These satellite receivers can be divided into two classes.

The first class includes single satellite receivers. A single satellite receiver can receive only one satellite at the time. The dish is either mounted in a fixed position or controlled by positional motors. In case the dish is mounted in a fixed position, the satellite receiver can aim at only one satellite and can receive only one satellite.

In case, the dish is controlled by positional motors, the antenna does not have an optimal installation position, as there is no inherent limit to the azimuth/elevation adjustments that can be made and therefore there is no Optimal installation position' to be found. Also, due to the fact that the receiver has a single satellite dish, it is not possible to keep track of a satellite while changing the position of the dish.

The second class includes multi-satellite receivers. Such multi-satellite receivers are able to receive signals from different satellites simultaneously, but only when the satellites are positioned in a straight line. In reality, most satellites are located along an arc shaped line. Thus, only a part of the arc can be covered by a multi-satellite dish when accepting a limited performance loss.

Furthermore, it is not possible to change the angles of the LNB's or the distance between the LNB's, because the LNB's are fixed in a mechanical construction to the dish. Thus, without moving the dish, the multi-sattelite receiver can receive only as many satellites as there are LNB's, and each LNB can only receive one satellite.

It is known in the art to install a satellite receiver with a dish-shaped antenna by firstly estimating where to aim, secondly to install the dish in that direction such that it receives a msodirmni signal power, and finally to manually turn the low noise block converter (LWB)₉ until a 'good' tv signal is received. Then, a user has to check whether the desired satellite is received, e.g. by viewing the signals on a television.

It is also known in the art, that a part of the installation of the prior art satellite receivers can be automated to a certain extend.

For example, United States patent 5 955 988 describes a method for installing a dish antenna. The dish antenna described in this prior art document is provided with a TV graphical user interface (GUI) to enable a user to input antenna location information required for setting up a dish antenna. When the TV GUI is set in a dish set-up mode, the user may activate a U.S. map button to display a map of the United States or another area on the earth's surface. When a remote pointing device is directed at a point on the map that represents the current location of a satellite receiver, the TV GUI displays a regional map that shows in more detail a region where the receiver is located. When the user selects the receiver location within the regional map, a CPU determines the latitude and longitude values of the selected location, and calculates magnetic north and elevation angles for the antenna installation. The calculated angels are then provided to a pointing device which mechanically positioned the antenna.

United States patent 5 471 219 describes a method for installing a satellite dish antenna mounted on a vehicle. The antenna described in this prior art document has a receiver connected to the satellite dish antenna that receives signals from an electronic compass for generating a magnetic direction signal. A user of the system manually selects the latitude and longitude coordinates corresponding to the parked vehicle location. The receiver determines an initial search position for the satellite dish antenna based upon the magnetic reading and the entered latitude and longitude values. The satellite dish antenna is moved from an un-stowed position to an initial search position. The satellite dish antenna is then moved in a first rectangular spiral search pattern to obtain a rough-tune position corresponding to the detection of a signal peak for a selected audio sub carrier frequency in a selected channel of a target satellite. A fine-tune search is then performed and the method calculates all the azimuth and elevation positions of all remaining satellites.

However, the known satellite receivers, and the known methods to install those satellite receivers, are disadvantageous because they require geographical input from an operator or a user of the satellite receiver. Accordingly, this individual lias to know the longitude and latitude of the satellite receiver relative to the celestial body, or to know geographic characteristics corresponding thereto, such as the nearest city.

It is a goal of the invention to provide a method for installing a satellite receiver on a celestial body, which does not require prior knowledge of the longitude and latitude of the position of the satellite receiver relative to the celestial body.

Therefore, in accordance with the invention, a method according to claim 1 is provided.

In such a method, the latitude and longitude of the position of the satellite receiver can be determined from the angle of the satellite signal stemming from a receivable satellite with respect to the phased array antenna, the satellite position stored in the memory, and the predetermined direction. Accordingly, prior knowledge of the longitude and latitude of the position of the satellite receiver relative to the celestial body are not required. Furthermore, such a method of installing the satellite receiver can be less sensitive to errors in positioning the antenna, since the receivable satellites in a direction different from the pre-determined direction will be found by scanning the sky. Optionally the position of the phased array antenna relative to the celestial body, can even be determined accurately if the actual direction in which the phased array antenna points deviates from the pre-determined position. An additional advantage is that such a satellite receiver may be implemented in a manner which allows tracking of movements of the phase array antenna on the celestial body, as is explained below in more detail. Another advantage is that the method also be applied to find and track non-stationary satellites.

Furthermore, in accordance with the present invention, a satellite receiver according to claim 14, a satellite system according to claim 15 a control unit according to claim 16, and a computer program product according to claim 17 are provided.

Specific embodiments of the invention are set forth in the dependent claims. Further details, aspects and embodiments of the invention will be described, by way of example only, with reference to the attached drawing.

FIG. 1 schematically shows a side view of an example of an embodiment of a satellite system according to the invention.

FIG. 2 schematically shows a block diagram of an example of an embodiment of a satellite receiver according to the invention. FIG. 3 schematically shows a flow-chart of an example of a method for installing a satellite receiver according to the invention.

FIG. 4 schematically shows a flow-chart of an example of the satellite find process in the method of FIG. 3.

FIG. 5 schematically shows a flow-chart of an example of the antenna location process in the method of FIG. 3.

FIG. 6 schematically shows a flow-chart of another example of the antenna location process in the method of FIG. 3.

FIG. 7 schematically illustrates locating the position of a phased array antenna on a celestial body, using a signal from a satellite in orbit around a celestial body.

The example of a satellite system of FIG. 1 includes satellites 21-23, each provided with a transmitter, and includes an example of an embodiment of a satellite receiver 1 according to the invention. Depending on the position of the satellite receiver 1, the satellite receiver 1 may receive satellite signals 31-33 transmitted by the satellites 21-23. In FIG. 1, the satellite receiver 1 is positioned on a celestial body 10, e.g. the earth, and the satellites 21-23 are in orbit around the celestial body 10. However, the satellite receiver 1 may likewise be in the air or in space, and for example be in an airplane or be a part of a satellite itself. In the example of FIG. 1, the satellite receiver includes an antenna array, which in this example forms a phased array antenna 4. Array antenna systems as well as phased array antenna systems are generally known in the art of antennas, for example from United States patent 6 232 919, and for the sake of brevity are not described in full detail.

The phased array antenna 4 has a window within which signals can be received. In this example, the phased array antenna 4 has been designed in such a way that it has a window of plus or minus 20 degrees around the direction in which the phased array antenna 4 is pointing. In the window, signals will be received with sufficient quality. Signals incident at an angle of more than 20 degrees with respect to this direction, that is outside the window, will have a reduced quality, up to the point that no useful signal can be received. However, it will be clear for a person skilled in the art of antenna design that it is possible to develop a phased array antenna which is capable of supporting a larger window, or a smaller window, and that the window may have any suitable shape or configuration, and, e.g., that the window does not necessarily have to be symmetrical in any direction. In the position shown in FIG. I₃ the satellite receiver 1 can receive signals within the window indicated with dash-dotted area 49a. Thus, the example of a satellite receiver 1 shown in FIG. 1 is able to receive signals from two satellites 21,22 within the window. If the phased array antenna 4 is moved, the position of the window changes, as shown with the area 49b indicated in FIG. 1 with the dashed line. After this movement, the satellite receiver 1 may receive satellite signals 32,33 from the satellites 22,32 within the window.

As shown in FIG. 2, in this example the phased array antenna 4 includes four antenna elements 41-44 positioned in a row. The antenna elements 41-44 can receive a satellite signal 3 transmitted from the satellite 2. However, it should be noted that the phased array antenna 4 may be implemented in any suitable manner, for example as described in International patent publication WO/03/047029, incorporated herein by reference. In general, any number of antenna elements may be used and the invention is not limited to the shown number of antenna elements. Furthermore, the antenna elements may, depending on the specific implementation, be positioned in an arrangement different from the line-shaped one dimensional arrangement in FIG. 2, such as a random distribution, a matrix shaped two-dimensional arrangement, a three dimensional arrangement or any other suitable arrangement. Furthermore, the phased array antenna 4 may include antenna elements sensitive to electro-magnetic radiation of a certain polarisation only, such as horizontally polarised, vertically polarised, right-hand eUiptically polarised, left-hand elliptically polarised or otherwise. For instance, the phased array antenna 4 may include two sets of antenna elements, the first set being sensitive to a first polarisation and the other set being sensitive to a second polarisation, which second polarisation can, for instance, be orthogonal to the first polarisation. The phased array antenna 4 may further include a suitable polarisation control circuit connected to the antenna elements 41-44.

The antenna elements 41-44 can receive electromagnetic radiation which reaches the phased array antenna 4 at an angle within the window 49a, 49b, also referred to as the viewing range or aperture of the phased array antenna 4. In FIG. 2, a bundle of electromagnetic radiation is shown. The bundle is composed of four parallel rays sl-s4 stemming from a, not shown, source of radiation. In the example shown, the ray s4 has a certain phase phi4 incident on the antenna element 44. The ray s3 incident on the antenna element 43, however, must cover an additional distance Δl, which is equal to the distance between the antenna elements 43 and 44 multiplied by the cosine of the angle α between the rays and the antenna plane X in which the antenna elements 41-44 are situated. As a result, the ray s3 has a phase shift relative to the ray s4 when the ray s3 reaches the antenna 4. The phases of the rays si and s2 differ in a similar manner.

The antenna elements 41-44 each include a phase or time shift circuit T41-T44, which imposes a phase or time shift on the received signal, e.g. the respective one of rays sl-s4. The phase or time shift or each of the antenna elements 41-44 can be controlled by a suitable shift control signal presented at a control input 48 of the phased array antenna 4. The phase shift of the rays sl-s4 can be compensated by a suitable setting of the phase- or time-shifts of the phase- or time-shifting circuits T41- T44, such that the mutual differences between the phase- or time-shifting circuits T41-T44 correspond to the phase differences of the incoming rays sl-s4.

The phase or time shifted signals from the antenna elements 41-44 are presented to a combiner unit 46 via connections 45,^" which combines the phase or time shifted signals into an antenna output signal. The combiner unit combines the phase or time shifted signals into an antenna output signal. The antenna output signal is then presented to an antenna output 47, and can be transmitted further to, for example, a television, a radio, or any other electronic device constructed to receive satellite signals.

In this way, because the phase- or time-shift depends on the angle of the incoming radiation, the direction from which the phased array antenna 4 can receive signals can be adjusted without physical movement of the phased array antenna 4, and an antenna beam 40 of the phased array antenna 4 can be formed and controlled. Beam forming and steering techniques are generally known in the art of phased array antennas and for the sake of brevity not described in further detail.

The satellite receiver 1 further includes a positioning unit 5. The positioning unit 5 has a control unit 51 which is connected with a control unit input 510 to the antenna output 47. A control unit output 511 of the control unit 51 is connected to the control input 48 of the phased array antenna 4.

The control unit 51 is further connected to a memory 52. The memory 52 may include any other suitable data storage means. The memory 52 may for example include a flash memory. Thereby, the data stored on the memory can be used at a starting point for a new installation (re-install at the same house, new installation at a new house, etc).

Reference data is stored in the memory 52. The reference data represents at least satellite identification information and satellite position with respect to a celestial body 10 of at least two satellites in orbit around the celestial body 10. The satellite position may for example be stored as the longitude and latitude of the position of a geostationary satellite with respect to earth or as the longitude and the lattitude of a path along the sky of a geosynchronouw satellite, as well as the time at which the geosynchronous satellite is of a point along the path. The satellite identification information may for instance be one or more of a transponder identification (ID) of the satellite, a transponder frequency, bit rates, and forward error correction settings of the satellite. Thereby, satellites which do not transmit an identification code of their own can be identified. For example, based on the transponder ID and frequency combinations, a satellite signal can be identified as originating from a specific satellite.

In case the control unit 51 uses, inter aha, one or more of the following aspects: transponder ID's, transponder frequencies, bit rates, and forward error correction settings as satellite identification information, the amount of memory required by the satellite receiver 1 can be reduced, because in satellite receiver systems, those aspects are already present in a memory for other purposes. For example in set-top boxes, information about those aspects is required for processing (e.g. decoding) the received satellite signals such that television or radio can outputted. The control unit 51 can then be connected to this memory, which therefore is a shared memory.

The control unit 51 is further connected to a man-machine interface, including a status indicator 53. In this example, the status indicator 53 has a visual output which includes a cross-shaped arrangement of four arrow-shaped light emitting diodes (LEDs) 531-534 respectively pointing left, right, up, and down. In the origin of the cross-shape, a central LED 535 is positioned. However, it will be clear to a person skilled in the art, that the man-machine interface may alternatively include other outputs, such as tactile outputs, or audio outputs. For example, the status indicator may include a speaker to output sounds, or have one or more touch panels via which a tactile sensation can be provided. During measurements, the LEDs 531-535 are flashing slowly to visually indicate to an operator or user of the satellite receiver 1 that the control unit 51 is processing to find receivable satellites 21-23 and to calculate the position of the satellites 21-23 and/or the satellite receiver 1 with respect to the celestial body 10. The central LED 535 is switched on by the control unit 51 in case the control unit 51 determines that the satellite receiver 1 is installed correctly, and switched off a certain period of time thereafter, e.g. five minutes or any other suitable period of time.

In case the control unit 51 determines that the satellite receiver 1 is not installed correctly, and that, for example, the phased array antenna 4 has to point in a direction more upwards and more to the left, the respective arrow shaped LED 531- 534 is switched on, to indicate to an operator or a user in which direction the phased array antenna 1 has to be moved.

The phased array antenna 4 may, for example, be pivotably mounted on a, not shown, base. The phased array antenna 4 can then by positioned to point in a certain direction either by manually pivoting the phased array antenna with respect to the base, on by pivoting by means of a, not shown, steering device, such as an electro¬ motor.

The positioning unit 5 in the example is arranged to perform an example of a method according to the invention, such as illustrated with the flow-charts of FIG's. 3- 6. The example of a method is started with pointing 110. The satellite receiver 1 is then pointed in a pre-determined direction, in this example with respect to the earth magnetic field. To that end, the positioning unit 5 may be provided with a (electronic) compass (not shown) which provides information to the not shown a steering device which can move the phased array antenna. The steering device can then be arranged to automatically position the phased array antenna, depending on the information provided by the compass.

In this example, the satellite receiver 1 is positioned with the antenna plane X in an upright position, facing southwards. Thus, in this example, after pointing 110, the phased array antenna 4 is pointing southwards with respect to the earth, and the window 49a, 49b has the shape of a cone with its central, longitudinal axis pointing horizontally southwards. Thereby, it is likely that at least one satellite is within the window 49a, 49b of the phased array antenna 4, since on the northern hemisphere, most geo-stationary satellites are present on the southern part of the sky. In addition, the positioning can be performed in a simple manner, since the south is a direction vf hich is easy to find.

Alternatively, the satellite receiver 1 may be positioned with respect to the celestial body 10 in another manner, for example using the rotational axis of the celestial body 10 as a basis, or in another pre-determined direction. For instance, if the phased array antenna 4 is positioned on the southern hemisphere of the earth, the phased array antenna 4 can be positioned pointing to the north. Preferably, the pre¬ determined direction is selected on the basis that one or more satellites are expected in the window of the phased array antenna 4 when the phased array antenna 4 is pointing more or less in the pre-determined direction.

After pointing 110, a satellite find process 120 is started. As shown in FIG. 4, the satellite find process 120 may include a start 121, after which in a scan number determination 122, it is determined by the control unit 51 whether or not scans have been performed before. If no scans have been performed before, an initial scan 126 is performed. In the initial scan 126, the phased array antenna 4 scans (at least a part of) the part of the sky within the window 49a, 49b. In this example, the control unit 51 transmits a suitable beam control signal via the control unit output 511 to the phase or time shift circuit T41-T44 in order to control the antenna beam 40 such that (at least a part of) the part of the sky within the window 49a, 49b of the phased array antenna 4 is scanned.

When a satellite signal is received during the initial scan 126, receivable satellites in the scanned part of the sky are identified in initial identification 127. In this example, if the phased array antenna 4 receives the satellite signal, the phased array antenna 4 outputs an antenna signal at the antenna output 48. The control unit 51 receives the antenna output signal at the control unit input 510, and compares aspects of the antenna output signal, such as its frequency, forward error correction characteristics or other suitable aspects, with the satellite identification information stored in the memory 52. When the respective aspects of the antenna output signal match the stored information the identity of the receivable satellite is determined, and the satellite is identified. The position of the identified receivable satellite is then determined by the control unit 51, from the angle of the antenna beam 40 relative to the antenna plane X, and the pointing direction of phased array antenna 4, in this example southwards. Referring to fig. 7, if the phased array antenna 4 is installed at point P on a celestial body 10, with coordinates (φ₅ θ, EE), the position of the satellite can be determined as follows. In fig. 7, RE represents the radius of the celestial body 10, which for example for earth is known, R₀ represents the radius of a geosynchronous orbit. Arrow x represents a x-axis, arrow y represents an y-axis, and arrow z represents a s-axis of a system of coordinates originating from the center, denoted with O in fig. 7, of the celestial body 10. The x,y, and z- axes are perpendicular to each other. The z-aiάs coincides with the rotational axis of the celestial body 10, and the x- asris passes through the intersection of a prime meridian, e.g. Greenwich zero meridian. Φ en θ represent unknown angles.

After the phased array antenna is pointed towards the south, in fig. 7 along the line P-Q, with the antenna surface perpendicular to the surface of the celestial body 10, i.e. vertically, the satellite receiver scans a certain part of the sky to find a satellite. If a satellite is found, the azimuth and elevation angles β and δ of the satellite can be determined by the control unit. In fig. 7, the azimuth and elevation angles are represented by the angles which the line PS, between the satellite and the phased array antenna, makes with the pointing direction of the phased array antenna, represented by arrow PX' in fig. 7. The determined angles can be stored as coordinates (61, δl) for this satellite.

After the initial identification 127, the control unit 51 stores the information about the identified receivable satellite and as position in the memory 52 during storing 128. After storing the information in the memory 52, the satellite find process 120 is then ended in end step 129.

When no receivable satellites are identified during the initial scan 126, or when scans have been performed before, next scan 123 is performed. In the next scan 123, the control unit 51 transmits a suitable beam control signal via the control unit output 511 to the phase or time shift circuit T41-T44 in order to control the antenna elements 41-44. The phase or time shift circuit T41-T44 are controlled such that (at least a part of) the part of the sky which has not been scanned before is scanned by the beam 40.

In addition, the control unit 51 may send a suitable control signal to a driving motor, which driving motor adjusts the pointing of the phased array antenna 4 or to the status indicator 53 to notify the operator that the antenna 4 must be repositioned manually. For instance, the antenna plane X can be rotated, sueli that the position of the window 49b changes with respect to the celestial body 10. The next scan 123 may thus include (a combination of) mechanical scanning and. electronic scanning.

The new part of the sky to be scanned during the nest scan 128, can be determined in any suitable manner. For example, during the initial scan 126 and the next scan 123 the sky may be scanned entirely.

Also, an ej∑pected position of one or more satellites outside the scanned part can be estimated, and a part of the sky covering the expected position can then be scanned. Thereby, the satellite find process can be accelerated, because less scan steps will be required to find one or more desired satellites.

Alternatively, the new part of the sky may be an annular part of the sky around an identified receivable satellite. Thereby, the scan of the sky is accelerated, because in general satellites will be grouped more or less together. For example, seen from earth, geostationary satellites are positioned close to each other in the sky in an arc shaped arrangement. When a single satellite is found, there is a relatively high change that a next satellite can be found by scanning in a circle around the first satellite.

Furthermore, the new part of the sky to be scanned may be an extrapolation of the already scanned part. For instance, as mentioned, seen from the earth surface all geostationary satellites are positioned along an arc-shaped part of the sky. In case one or more satellites have been found, other satellites can be found by extrapolating an arc schape line which crosses the positions of the already found satellites.

When a satellite signal is received during the next scan 123, receivable satellites in the scanned part of the sky are determined during a subsequent identification 124. In this example, the identification 124 is performed in a similar manner as the initial identification 127. The position of the identified receivable satellite is then determined by the control unit 51 from the angle of the antenna beam 40 relative to the antenna plane X, and the direction in which the phased array antenna 4 is pointing during the next scan 123 as is explained above. During storing 125, the information about the identified receivable satellite is stored by the control unit 51 in the memory 52.

After storing the information in the memory 52, the satellite find process 120 is ended in step 129. After the satellite find process 120, an antenna location process 130 is performed by the control unit 51. During the antenna location process 180, the control unit 51 determines the position of the phased array antenna 4 with respect to satellites which are to be received. When the position of the phased array antenna 4 is not sufficient to receive the respective satellite, the contact unit 51 determines, to which direction the phased array antenna 4 has to be moved. The antenna location process 130 can be performed in any suitable manner, and the control unit 51 may be implemented in any manner such that the control unit 51 is capable of performing a suitable antenna location process.

In the example of an antenna location process 130 illustrated FIG. 5, the sky is scanned for at least two pre-selected satellites during the satellite find process 120, in this example the Astra ID satellite and the Eurobird satellite. The correctness of the positioning of the phased array antenna 4 with respect to the earth is checked using the position of the pre-selected satellites. If the positioning does not satisfy a predetermined quality criterion, a direction in which the phased array antenna 4 has to be moved is then determined and indicated to an operator or user of the satellite receiver 1.

In the example of fig. 5, after a start 131, the antenna location process 130 is continued by a retrieval 132 of the stored position data relating to the pre-selected satellites from the memory 52. E.g. the position with respect to the celestial body 10 has been pre-stored in the memory 52, as well as the determined position of the respective satellites as determined in identification steps 124, 127 is retrieved from the memory 52. During a check 133, the pre-stored position is compared with the determined position. After the check 133, in step 134 is determined if both pre¬ selected satellites can be received.

In case, not all of the pre-selected satellites can be received in the direction in which the antenna has to be moved is determined during move calculation 138. If neither Astra ID nor Eurobird can be received, the phased array antenna 4 is not positioned correctly. The phased array antenna is moved, and is the satellite find process 120 is performed again with a next scan 123. If only one known satellite can be received, and it is known whether the phased array antenna 4 is on the northern or southern hemisphere, than it can be determined whether the antenna needs to be moved to the left or to the right in order to receive the pre-selected satellites. As will be explained below, the position P of the phased array antenna can be determined from the coordinates of the receivable satellite, as determined in the identification 124,127 of the angle of incidence of the signals from that satellite, and the predetermined direction. Accordingly, the position of the pre-selected satellites relative to the phased array antenna 4 can be determined, and the direction in which the phased array antenna 4 has to be pivoted in order to have the pre-selected satellites in the window 49a, 49b of the phased array antenna 4.

If two known satellites are received, the satellite receiver itself can determine whether the phased array antenna 4 is installed on the northern or eastern hemisphere, and the direction in which the phased array antenna 4 has to be moved, as will be explained below. In the examples of figs. 5 or 6, this may include that only one of the ASTRA ID satellite or the Eurobird satellite can be received, together with another known satellite or two known satellites can be received, but none of the pre¬ selected satellites.

If both the Astra ID satellite and the Eurobird satellite are identified as receivable satellites, a signal quality check 135 is performed. During the signal quality check 135, the control unit 51 is determined if the received signals from the respective pre-selected satellites satisfy at least one pre-determined selection criterion, such as that the bit error rate, or the signal to noise ratio is below a treshold value or other suitable quality criterion, as is explained below in more detail with respect to step 140.

When the signal quality check 135 reveals that the signals do not satisfy the applied quality criterion, i.e. the signal quality is not sufficient, a direction in which the phased array antenna 4 has to be moved to improve the signal quality is calculated in step 136. For instance, the quality of the signals from different ones of the pre-selected satellites can be compared, and if the signals from one satellite have a higher quality than the signals from another satellite (e.g. the bit error rate is lower), the direction in which the phased array antenna has to be moved is determined as pointing more towards the satellite with the lowest signal quality. If the signal quality check 135 reveals that the signal quality is sufficient for both pre¬ selected satellites, the antenna installation process 130 is marked as good enough in step 137. After performing step 136, 137 or 138, the antenna location process is ended in step 139. In the example of an antenna installation process 130 of FIG. 6, the location of the phase array antenna 4 with respect to the celestial body 10 is determined. Thereby, further measures can be taken to reduce errors in the antenna installation. An error may for instance occur if one or more of the pre-selected satellites is obscured, for eicample if the pre-selected satellite is behind an obstacle, such as a tree or a house, and cannot be received from that position. In the example of fig. 6, the location of the phased array antenna 4 is determined and therefore the azimuth/elevation of the 'invisible' satellite can be calculated and it can be determined whether or not the satellite is likely to be behind an obstacle. E.g. the satellite can be determined to be expected near the horizon and thus likely to be obscured.

In addition the memory 52 can be provide with data which represents the height and location of objects near the position of the phased array antenna. The control unit can than be constructed to determine from this data, the position of the phased array antenna, and the azimuth/elevation of the satellite whether or not one or more of those objects are likely to obscure the satellite.

The positioning may further be provided with an altitude measuring device 54 communicatively connected to the control unit 51, from which the control unit can receive signals representing the altitude of the phased array antenna, and determine the difference in altitude of the top of subjects around the phased array antenna and the phased array antenna 4. From this difference, the control unit 51 can then determine whether or not objects around the phased array antenna 4 are likely to obscure the respective satellite.

In the example of fig. 6, after a start 181, data is retrieved from the memory 52 during retrieval 182. The retrieved data includes the pre-stored data associated with the identified receivable satellites, e.g. the pre-stored position data, as well as the data determined during the satellite find process 120, Le. the determined position of the satellites as determined during identification 124, 127.

The position of the phased array antenna 4 relative to the earth is determined from the retrieved data. During longitude determination 183, the longitude of the phased array antenna 4 is determined. To that end, the highest satellite is determined from the identified retrievable satellites. The geostationary position of this satellite (say 5° East) can then be selected, and the longitude of the phased array antenna 4 is determined as being the same (5° East), within an accuracy of about 2° in either direction. Thereby, the longitude of the phased array antenna 4 is determined in a computationally simple manner. However, the longitude may likewise be determined in any other suitable manner.

In the memory 51, a list of values may be pre-stored in a table, in which for example coordinates (Φ, θ, EE) of possible antenna positions in a certain area of the celestial body 10 are listed. For instance, the table may contain a list which covers the northern hemisphere and ranges the values of the angle Φ from -180° to 180°, and the angle θ from 0° to 90° with a certain resolution, e.g. 1°. However, to reduce the amount of computational power required, the area may be reduced, and cover the values for a smaller part of the celestial body 10, e.g. Europe only.

For each coordinate of an antenna position, the associated values of the azimuth and elevation angles β and δ of one or more geostationary satellites are determined and pre-stored in the table. The longitudial position y of all geostationary satellites is known, and their lattitude as well (all geostationary satellites are in the equatorial plane, hence the lattitude is 0°). Accordingly, the azimuth and elevation angles can be determined and stored in the table.

The determined coordinates (61, δl) of the received satellite are then looked up by the control unit 51 in the table and the antenna position coordinates associated with those determined coordinates be set by the control unit 51 as the position of the phased array antenna.

Alternatively, the position of the phased array antenna 4 may be determined by the control unit by calculating the position from the azimuth and elevation angles of the geo-stationary satellite and the pre-stored longitude γ thereof, using the following method. Eeferring to the XYZ system of coordinates of fig. 7, the longitude γ of the satellite in XYZ-coordinates can be described as the vector from O to S (O being the origin of the system of coordinates, S being the position of the satellite);

OS = (R₀ cos γ, R₀ sin γ, O) = R₀ cos γX + R₀ sin χΫ+OZ .

Likewise, the antenna position P, with longitude φ and latitude θ is given by the vector; OP = (R_E COS Θ COS φ, R_E cos Θ sin φ, sin Θ)

= R_E cos Θ cos φll+ R_E cos Θ sin φY + R_B sin Θ7L

(1.2)

The vector from the antenna position, P, to the satellite position, S, is then given by;

PS = OS -OP

= (R₀ COS γ - R_E cos θ cos φ) Ji+ (R₀ sin γ — R_E cos θsinφ)Y- R_E sin ΘZ ,~ ^

The transformation from XYZ-coordinates to X'YZ'-coordinates is accomplished by another coordinate transformation matrix:

(1.4)

where

The elevation of the satellite from the antenna position P can be calculated by a method represented by the mathematic formula:

S = ^- COS-¹ ($S &)

(1.5) which using equations 1.1 to 1.4 can be rewritten as: π , MiC_n cos 7 -IC_P COSeXOSeUlCOSCf COs^ )+ \

^ — - cos^"1 ) o ' ^r \^JX Y (1.6)

2 \[R₀ sin γ - R_E cos Θ sin ^ j(eos <9 sin φ) - R_E sin 6* sin θj

This can be re-ordered to:

Which can be reduced to:

J = -- cos^"1 (Jc₀ cos θ cos(f - ^) - R_E ) (1.8)

Equation l.< 8 can be re-arrai iged to:

Accordingly: β = π-cos^~' {¥τ-^') (1.10)

Now note that this can be rewritten to: β = π -co$-¹(K PS - X') (1.11) in which ^• represents the inproduct, and X' is by definition of the value (1, 0, 0), thus the inproduet reduces to:

, f sin έ? cos ^(i?₀ cosf -ic^ cos^cos^) ^ β = π — cos , v i^+ sin θ sin φ{R_Q sia/ -R_E cos θ sin φ) + R_E cos θ sin 6¹J

Which after some re-ordering reduces to: β = π - cos^"1 (R₀ sin θ cos(^ - φ) -R_E sin 0 cos θ) (1.12)

Equations 1.9 and 1.12 can be used to determine the position, since these contain only two unkowns (θ and Φ). These equations can be solved numerically using computational methods generally known in the art. In equations 1.9 and 1.12 it is assumed, that the phased array antenna 4 is aimed exactly to the south. However, if there is an offset in the aiming of the phased array antenna 4 and/or if the phased array antenna 4 is rotated, then instead of measureming δ and β, it is to be assumed that δ+Δ and β+B are measured, Δ and B representing the off-set. In such case there are four unknowns in the equations, which can be solved by measuring for two geostationary satellites. In latitude determination 184, the latitude of the position of the phased array antenna 4 is determined. In this example, the latitude is determined from the azimuth difference between at least two pre-selected satellites, in this example the Astra ID satellite and the Eurobird satellite. Those two satellites are needed to be received in most satellite receivers and are on opposite borders of the sky coverage usually required for satellite receivers. This reduces errors in the determined latitude.

In step 184, the Astra ID satellite and the Eurobird satellite are searched in the set of identified receivable satellites. When both satellites are found, the azimuth difference between those two satellites is determined and compensated for the determined longitude of the phased array antenna 4. From the corrected azimuth difference, the latitude of the phased array antenna 4 is determined.

As an alternative to the latitude determination 184 as shown in fig. 6, the satellites just above the horizon may be determined, and the latitude of the phased array antenna 4 can be calculated from the position of those satellites.

Using the longitude and latitude information, the operator can be instructed to move the antenna 4 via the man-machine interface, e.g. status indicator 53. In addition, the determined position of the phased array antenna 4 can be used to filter the received satellite signals in dependence on the determined longitude and latitude of the phased array antenna, and to output the filtered satellite signals at a receiver output 47. Thereby, for example, location based services, like country specific program listing, can be supported automatically.

For instance, the control unit may determine if a desired satellite can be received with sufficient quality. The quality can be determined, e.g., by comparing the bit error rate (BER) with a threshold value, or otherwise.

As a first criterion, the required satellites can be received 'good enough'. This means that at that moment in time, the reception of tv/radio/internet will work, but the signal quality could degrade when it starts raining, leaves grow on trees, etc.

As a second criterion, the required satellites can be received 'good enough' with a specified margin. This means that at that moment in time, the reception of tv/radio/internet will work, also when it starts raining, leaves grow on trees, etc.

As a third criterion, the optimum position giving the highest quality is found and the antenna is installed there. The consequence could be that the installation time is increased. It is also possible to determined the signal quality based on a combination of the specified criteria.

Depending on the required reliability, one (or a combination thereof can be chosen). For instance, if the phased array antenna 4 is likely to be moved, the criterion may be "good enough", and the bit error rate (BER) may be required to be below a first threshold value. When the phased array antenna is supposed to be stationary for a longer period of time, but might be moved thereafter, the criterion might be "good enough within a margin", and for example the BER may be required to be below a second threshold value, lower than the first threshold value.

In case the phased array antenna is fixedly mounted, for instance on a house, the optimum position may be required, and the BER may be required to be below a third threshold value below the second threshold value.

When the antenna is installed correctly, Le. the quality check 140 is passed, the control unit 51 transmits in end installation step 150 a correct signal to the status indicator 53. In response to the correct signal, the status indicator 53 outputs in a for humans perceivable form that the quality is sufficient. In the example, the central LED 535 is switched on in response to the correct signal for a predetermined period of time in end installation step 150.

When the quality check 140 reveals that the signal quality from the satellite which is deserid to be received is not sufficient, a move direction of the phased array antenna 4 is determined, for example using the information of step 138 or, in the example of fig. 6, using the determined longitude and latitude of the phased array antenna 4 and an expected position of one or more satellites which are desired to be received. The control unit 51 then transmits a move signal to the status indicator 53. The move signal indicates the direction to which the satellite receiver 1 has to be moved. In response to the move signal, the status indicator 53 outputs in indication step 160 the direction in a for humans perceivable form, in the example of FIG. 2, by switching on the arrow-shaped LEDs corresponding to the determined move direction.

In the example of fig. 3, after indication step 160, the phased array antenna 4 is moved. During the movement of the phased array antenna 4, the control unit 5 can track signals from one or more satellites in tracking step 170 by steering the antenna beam 40 such that those satellites are within the window 49a, 49b. Thereby, the direction and amount of movement of the phased array antenna 4 relative to the celestial body 10 can be determined For instance, by determining the change in the azimuth and elevation angle of the satellite, and looking the corresponding position in the pre-stored list of coordinates. During movement of the satellite receiver 1, the control unit 51 may keep track of the movement until the optimum position is reached, by calculating how much the antenna has to be moved to the left or right, to reach an optimal installation from the position of the phased array antenna 4, as explained above with respect to figs. 5 and 6. When the optimum position of the phase array antenna 4 is reached, the control unit 5 can send a correct signal to the status indicator 53. The status indicator 53 can then output an optimum signal in response to the correct signal.

Tracking of the movement cannot be performed with a conventional satellite receiver, because either and the reference position of the antenna dish is changed manually or the complete mechanical construction (which is relatively heavy) is moved. When position is changed manually, the positioning engines and mechanics are not activated, in which case it will be physically impossible to continuously track a satellite. When the complete construction is moved, this will result in sudden, fast, movements in both azimuth and elevation which are impossible to follow for a mechanical construction, unless it has very strong and fast engines.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternatives within the scope of protection as defined by the appended claims.

For example, the control unit 5 may be implemented as one or more programmable devices arranged to receive data and perform instructions represented by the data, e.g. Central Processing Units as are known in the art of general purpose computers, such that the programmable devices are capable of performing at least a part of a method according to the invention. However, the control unit 5 may also include non-programmable devices arranged to perform a specific task, such as application specific integrated circuits (ASICs), as known in the art of integrated circuits, or any other device suitable to perform the functions of the control unit. Also, the phased array antenna 4 and the positioning unit 5 may be positioned at different locations and be communicatively connected. The devices in the control unit may also be positioned at different locations and be communicatively connected. For instance, the memory 52 may be provided in a set-top box inside a home, while the control unit 51 is incorporated in a phased array antenna 4 which is positioned outside. Also, the satellite receiver may be provided on a stationary object, such as a house, or a on movable object such as a car, a boat, an airplane or any other vehicle.

The invention can also be applied as a data carrier comprising data representing a computer program product, which includes a program code for performing steps of a method according to the invention when run on a programmable device. Such a data carrier can for example be a read only memory compact disk (CD- ROM) or a signal transfer medium, such as a telephone cable or a wireless connection. The programmable device may be of any suitable type. For example, it may be a computer communicatively connected to a phased array antenna. However, the computer may likewise be not physically connected to a phased array antenna, but receive data representing signals from the phased array antenna, e.g. via a floppy disk or a compact disk.

Also, the satellite receiver 1 can be used to receive satellite signals from a satellite in a geosynchronous orbit, that is an orbit that has the same orbital period as the celestial body 10 it orbits (usually the Earth, but geosynchronous orbits exist around all celestial bodies, such as moons, planets and stars, that have sufficient rotational speed for an orbit to be maintained above their surface). For instance, the satellite may be a geostationary satellite or a satellite in an inclined orbit. A geostationary satellite is a satellite in a geosynchronous orbit which is circular and equatorial, in such case the satellite will be stationary relative to the celestial body 10 around which the satellite rotates. A satellite in an inclined orbit has an orbital path which is tilted to the north or south with respect to the equatorial plane of the celestial body 10, but has a period of rotation equal to the period of the celestial body 10.

The word 'including' does not exclude the presence of other elements or steps than those listed in a claim. Furthermore, the term 'antenna beam' refers to both the pattern of transmitted radiation of a transmitting antenna as well as the pattern of radiation which can be received with a receiving antenna. Also, depending on the specific implementation, steps of a method according to the invention may be performed simultaneously or in consecutive order. Furthermore, the words 'a' and 'an' shall not be construed as limited to 'only one', but instead are used to mean 'at least one'.

Claims

1. A method for installing a satellite receiver (1) on a celestial body (10). the satellite receiver (1) including: a phased array antenna (4), and a receiver memory (52) in which reference data is stored, the data at least representing properties of at least two satellites (21-23) in orbit around the celestial body (10), the properties including satellite identification information and satellite position with respect to the celestial body (10); the method including:

(a) pointing the phased array antenna (4) in a pre-determined direction with respect to the celestial body (10); _° (b) searching for satellites from which satellite signals can be received by means of the satellite receiver, said searching including: controlling an antenna beam (40) of the phased array antenna (4) such that the phased array antenna (4) scans a part of the sky of the celestial body (10); and if a satellite signal is received by the phased array antenna (4) during the searching: B (c) identifying receivable satellites in the scanned part of the sky from at least one aspect of the received satellite signal, and the satellite identification information.

2. A method as claimed in claim 1, further including if no satellite signals are received during said searching:

■ (d) transmitting a move signal to a status indicator (53), the move signal indicating a direction to which the satellite receiver (1) has to be moved, in response to which move signal the status indicator (53) outputs the direction in a for humans perceivable form; and if satellite signals are received during said searching:

(e) determining the location of the satellite receiver (1) with respect to the celestial body (10) by means of a comparison of the position of the identified receivable satellites with the reference data; and/or (f) determining if the satellite receiver (1) is positioned such that signals from at least one of the receivable satellites are receivable with sufficient signal quality; and if the signal quality is sufficient:

(g) transmitting a correct signal to a status indicator (53), in response to which the status indicator (53) outputs in a for humans perceivable form that the quality is sufficient; or if the signal quality is insufficient: performing step (d).

3. A method as claimed in claim 2, further including if step (d) is performed, in response to moving the satellite receiver (1), controlling the antenna beam (40) such that the phased array antenna (4) scans a new part of the sky, and performing steps (b)-(g) using signals received from the new part of the sky.

4. A method as claimed in claim 3, including determining an expected position of at least one satellite outside the scanned part, and scanning a new part of the sky which includes the expected position.

5. A method as claimed in claim 3 or 4, wherein the new part is an annular part of the sky around an identified receivable satellite.

6. A method as claimed in any one of claims 3- 5, further including if satellite signals are received and step (d) is performed, tracking signals from a satellite during a movement of the phased array antenna (4) relative to the celestial body (10), and determining from the tracked signals a movement of the phased array antenna (4).

7. A method as claimed in claim 6, further including determining an optimum position of the satellite receiver, and outputting an optimum signal when during said movement, the satellite receiver (1) reaches the optimum position.

8. A method as claimed in any one of the preceding claims, wherein step (d) is performed if the amount of receivable satellites is below a threshold value, such as two, or the group of determined receivable satellites does not include at least one pre¬ selected satellite.

9. A method as claimed in any one of the preceding claims, further including after step (e): pointing the phased array antenna (4) and/or the antenna beam (40) such that a selected satellite can be received.

10. A method as claimed in any one of the preceding claims, wherein step (e) includes: determining from the received signals a highest satellite with the highest elevation with respect to the part of surface of the celestial body (10) on which the satellite receiver (1) is positioned; determining the identity of the highest satellite; retrieving from the receiver memory (52) the position of the highest satellite relative to the celestial body (10); and determining from the position of the highest satellite relative to the celestial body(lθ) the longitude of the satellite receiver (1) position relative to the celestial body(lθ).

11. A method as claimed in claim 10, further including: searching for at least two pre-selected satellites; determining the azimuth difference between the pre-selected satellites; and determining from the azimuth difference the latitude of the satellite receiver (1) position relative to the celestial body (10).

12. A method as claimed in claim 10 or 11, further including receiving satellite signals from at least one of the receivable satellites, filtering the received satellite signals in dependence on the determined longitude and latitude, and outputting the filtered satellite signals at a receiver output (47).

13. A method as claimed in any one of claims 10-12, wherein said selected satellite is an satellite in an inclined orbit around the celestial body (10).

14. A satellite receiver, including: a phased array antenna (4); a receiver memory (52) in which reference data is stored, the data at least representing properties of at least two satellites in orbit around a celestial body (10): the properties including satellite identification information and satellite position with respect to the celestial body (10); at least one control unit (51) having a control unit input (510) connected to at least one signal output (47) of the phased array antenna (4), and a control unit output (511) connected to at least one antenna control input (48) of the phased array antenna (4); the control unit (51) being arranged to perform at least a part of a method as claimed in any one of the preceding claims.

15. A satellite system including at least one satellite (21-23) with a signal source arranged for transmitting a satellite signal and further including at least one satellite receiver (1) as claimed in claim 12 for receiving the satellite signal.

16. A control unit (51) arranged for use in a satellite receiver (1) according to claim 12.

17. A computer program product, including a program code enabling a programmable device to perform steps of a method as claimed in any one of claims 1- 13 when run on a programmable device, said programmable device being communicatively connectable to a phased array antenna.