CA2473479C - Method of pointing a vehicular mounted directional antenna of a satellite signal receiver at a communications satellite - Google Patents
Method of pointing a vehicular mounted directional antenna of a satellite signal receiver at a communications satellite Download PDFInfo
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- CA2473479C CA2473479C CA002473479A CA2473479A CA2473479C CA 2473479 C CA2473479 C CA 2473479C CA 002473479 A CA002473479 A CA 002473479A CA 2473479 A CA2473479 A CA 2473479A CA 2473479 C CA2473479 C CA 2473479C
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- 238000000034 method Methods 0.000 title claims description 26
- 230000003213 activating effect Effects 0.000 claims description 2
- 230000004913 activation Effects 0.000 claims description 2
- 230000010354 integration Effects 0.000 claims description 2
- 238000002604 ultrasonography Methods 0.000 claims 1
- 230000009897 systematic effect Effects 0.000 description 3
- 230000001934 delay Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/27—Adaptation for use in or on movable bodies
- H01Q1/32—Adaptation for use in or on road or rail vehicles
- H01Q1/325—Adaptation for use in or on road or rail vehicles characterised by the location of the antenna on the vehicle
- H01Q1/3275—Adaptation for use in or on road or rail vehicles characterised by the location of the antenna on the vehicle mounted on a horizontal surface of the vehicle, e.g. on roof, hood, trunk
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
- H01Q1/125—Means for positioning
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
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- Engineering & Computer Science (AREA)
- Remote Sensing (AREA)
- Radio Relay Systems (AREA)
- Variable-Direction Aerials And Aerial Arrays (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
In pointing a vehicular (7) mounted directional antenna (5) of a satellite signal receiver at a communications satellite transmitting radio signals by means of analyzing the receiving levels of radio signals transmitted by the satellite and received via the directional antenna, tracking being preceded by a pointing and acquisition mode for initial and repeat pointing of the directional antenna at the satellite, activated as soon as the received signal drops below a defined signal level threshold, signal shadowing caused by obstacles (8) in the link between satellite and directional antenna are sensed by means of a sensor system additionally provided on the vehicle and information as to the shadowing zones in the field of view and/or in the motion range of the directional antenna output and the pointing and acquisition mode is disabled for the duration of passing the shadowing zones on the basis of the information obtained by means of the sensor system as to the shadowing zones following the tracking phase or deactivated following a pointing and acquisition mode, despite the received signal dropping below a defined signal level threshold. For use in mobile satellite communications.
Description
Method of pointing a vehicular mounted directional antenna of a satellite signal receiver at a communications satellite The invention relates to a method of continually pointing a vehicular mounted directional antenna of a satellite signal receiver at a communications satellite transmitting radio signals by means of analyzing the receiving levels of radio signals transmitted by the satellite and received via the directional antenna, tracking being preceded by a pointing and acquisition mode for initial and repeat pointing of the directional antenna at the satellite, activated as soon as the received signal drops below a defined signal level threshold.
Directional antennas are needed for satellite communications involving high data rates. These are e.g.
antennas such as a parabolic antenna exhibiting a concentrated main lobe in one direction and thus very high gain. When such an antenna is provided for mobile reception on a vehicle, e.g. on board a motor vehicle, ship or aircraft, it continually needs to be re-pointed at the satellite to compensate for vehicle motion in thus maintaining the satellite communications link.
A variety of methods are known for tracking the antenna in this context, most of which are based on analysis of the received signal strength such as e.g. conical scan or monopulse scan or simply by signal feedback in optimizing the received signal.
Directional antennas are needed for satellite communications involving high data rates. These are e.g.
antennas such as a parabolic antenna exhibiting a concentrated main lobe in one direction and thus very high gain. When such an antenna is provided for mobile reception on a vehicle, e.g. on board a motor vehicle, ship or aircraft, it continually needs to be re-pointed at the satellite to compensate for vehicle motion in thus maintaining the satellite communications link.
A variety of methods are known for tracking the antenna in this context, most of which are based on analysis of the received signal strength such as e.g. conical scan or monopulse scan or simply by signal feedback in optimizing the received signal.
In directional antenna pointing a distinction is usually made between the status of coarse pointing, the acquisition status and the actual tracking status (tracking phase). In coarse pointing, to be initiated in first-time or repeat pointing at a satellite, a systematic search of the transmitter mounted on the satellite is made by the ground receiver until a signal strength is received, needed as a minimum. During the subsequent acquisition phase the main lobe of the directional antenna is moved until the received signal strength is optimized and in the course of the following, actual tracking phase of the directional antenna reception in mobile operation is maintained by correcting minor erroneous pointing of the directional antenna main lobe.
In this arrangement, the pointing and acquisition duration needs to be a minimum in ensuring fast communications in initializing the communications system or following loss of the satellite signal. The pointing and acquisition duration can be shortened by focusing the pointing zones e.g. by attitude and position information of the mobile directional antenna.
If the link between satellite and mobile reception antenna in communications is disrupted by an obstacle, this usually involves, because of the signal being shaded, a signal loss which especially at the higher frequencies has a particularly sharp ON (line of sight to satellite)/OFF
(shadowing) characteristic due to the refraction in this case being less. From the strength of the signal received there is no distinguishing whether the signal loss is due to the directional antenna being erroneously pointed or because of a shadowing obstacle. In any case, as soon as the received signal drops below a defined signal level threshold in tracking, the search for the satellite signal is initiated.
Methods known hitherto of tracking a mobile receiving antenna to a satellite, taking into account analysis of the received signal level, are described, for example, in DE 38 23 109 C2, WO 95/20249, US 5,194,874 and US
6,075,482, all of which fail to distinguish between shadowing and erroneous pointing of the directional antenna in signal loss. When the signal received by the directional antenna drops below a defined threshold a new search action is initiated in these known methods by the receiver either instantly or after a defined delay even if the directional antenna is in a shaded zone.
Furthermore, additional information as to the rotational motion of the vehicle is analyzed in these known methods, i.e. a loss of signal without rotational motion of the vehicle is interpreted to be a shadowing and a repeat search action delayed. This supports making the decision as to whether a signal loss is due to shadowing of the propagation path or to erroneous pointing of the antenna.
This information, in addition, fails to apply to a significant operational range in tracking the antenna which is vital in the case of a satellite particularly for rotational motion of the vehicle with the mounted antenna.
According to the present invention, there is provided a method of continually pointing a vehicular mounted directional antenna of a satellite signal receiver at a 3a communications satellite transmitting radio signals by means of analyzing the receiving levels of radio signals transmitted by the satellite and received via the directional antenna, tracking being preceded by a pointing and acquisition mode for initial and repeat pointing of the directional antenna at the satellite, activated as soon as the received signal drops below a defined signal level threshold, and signal shadowing caused by obstacles in the link between satellite and directional antenna are sensed by means of a sensor system provided on the vehicle, and information is output by said sensor system which results in disabling said pointing and acquisition mode for the duration of passing the shadowing zones, despite the received signal is dropping below a defined signal level threshold, and in not activating the pointing and acquisition mode at least initially after having passed sensed shadowing zones not exceeding a defined duration, so that no new satellite signal search is started, the directional antenna instead remaining as pointed prior to the occurrence of each shadowing, characterized in that said information concerning shadowing zones is not output by a sensor system deciding only indirectly on shadowing, but is a direct information output by a sensor system whose line of sight is steered together with the field of view of the directional antenna (5), or is output by a data base in which the shadowing zones resulting in a shadowing pattern are stored.
Each receiving status described is illustrated in FIGs. 1 to 4, where Pin is the received strength and Popt is the maximum strength received with optimum pointing of directional antenna 1, for example a parabolic antenna, received without shadowing. The direction of direct incidence of the satellite signal is identified by the arrow 2 in all four FIGs.
Referring now to FIG. 1 there is illustrated the status for optimum reception in which the main lobe 3 of the directional antenna 1 corresponding to the direction of maximum sensitivity precisely points in the direction of direct incidence 2 of the satellite signal. In this status we thus have Pin = Popt .
Referring now to FIG. 2 there is illustrated the status of slight erroneous pointing of the directional antenna 1 in which the direction of the main lobe 3 of the directional antenna 1 slightly differs from the direction of direct incidence 2 of the satellite signal. In this status we thus have Pin 9:-- Popt.
Referring now to FIG. 3 there is illustrated the status of coarse erroneous pointing of the directional antenna 1 in which the direction of the main lobe 3 of the directional antenna 1 greatly differs from the direction of direct incidence 2 of the satellite signal. In this status we thus have Pln << Popt .
Referring now to FIG. 4 there is illustrated the status in which, although the directional antenna 1 is substantially pointed at the satellite, in other words the direction of the main lobe 3 of the directional antenna 1 agrees with the direction of direct incidence 2 of the satellite signal, a disruptive obstacle 4 exists between the 5 satellite and the directional antenna 1. In the course of the zone of signal shadowing due to the obstacle the strength received can greatly differ from Pin :z~ PoPt to Pin PoPt .
Re-pointing or a signal loss results in a coarse pointing of the directional antenna 1 and thus of the main lobe 3 in the form of a systematic search for the direction of incidence 2 of the satellite signal until a signal strength Pin <G PoPt necessary as a minimum in the status as shown in FIG. 3 is received. Coarse pointing is followed by the acquisition phase during which the strength Pin received via the directional antenna 1 is optimized, i.e.
until in the end the status as shown in FIG. 1 is attained.
After this, during the actual tracking phase of the directional antenna 1, reception in mobile operation is maintained as represented by FIG. 2. If the communications link between the satellite and the mobile directional antenna 1 is disrupted by an obstacle 4, as shown in FIG.
4, because of signal shadowing, a signal loss occurs.
The strength Pin of the received signal fails to indicate whether the cause of the signal loss is coarse erroneous pointing of the directional antenna 1 as shown in FIG. 3 or shadowing due to an obstacle 4 as shown in FIG. 4. The result of the signal loss in any case is a repeat systematic search of the direction of incidence of the satellite signal which in the case of a shadowing is, of course, useless.
In this arrangement, the pointing and acquisition duration needs to be a minimum in ensuring fast communications in initializing the communications system or following loss of the satellite signal. The pointing and acquisition duration can be shortened by focusing the pointing zones e.g. by attitude and position information of the mobile directional antenna.
If the link between satellite and mobile reception antenna in communications is disrupted by an obstacle, this usually involves, because of the signal being shaded, a signal loss which especially at the higher frequencies has a particularly sharp ON (line of sight to satellite)/OFF
(shadowing) characteristic due to the refraction in this case being less. From the strength of the signal received there is no distinguishing whether the signal loss is due to the directional antenna being erroneously pointed or because of a shadowing obstacle. In any case, as soon as the received signal drops below a defined signal level threshold in tracking, the search for the satellite signal is initiated.
Methods known hitherto of tracking a mobile receiving antenna to a satellite, taking into account analysis of the received signal level, are described, for example, in DE 38 23 109 C2, WO 95/20249, US 5,194,874 and US
6,075,482, all of which fail to distinguish between shadowing and erroneous pointing of the directional antenna in signal loss. When the signal received by the directional antenna drops below a defined threshold a new search action is initiated in these known methods by the receiver either instantly or after a defined delay even if the directional antenna is in a shaded zone.
Furthermore, additional information as to the rotational motion of the vehicle is analyzed in these known methods, i.e. a loss of signal without rotational motion of the vehicle is interpreted to be a shadowing and a repeat search action delayed. This supports making the decision as to whether a signal loss is due to shadowing of the propagation path or to erroneous pointing of the antenna.
This information, in addition, fails to apply to a significant operational range in tracking the antenna which is vital in the case of a satellite particularly for rotational motion of the vehicle with the mounted antenna.
According to the present invention, there is provided a method of continually pointing a vehicular mounted directional antenna of a satellite signal receiver at a 3a communications satellite transmitting radio signals by means of analyzing the receiving levels of radio signals transmitted by the satellite and received via the directional antenna, tracking being preceded by a pointing and acquisition mode for initial and repeat pointing of the directional antenna at the satellite, activated as soon as the received signal drops below a defined signal level threshold, and signal shadowing caused by obstacles in the link between satellite and directional antenna are sensed by means of a sensor system provided on the vehicle, and information is output by said sensor system which results in disabling said pointing and acquisition mode for the duration of passing the shadowing zones, despite the received signal is dropping below a defined signal level threshold, and in not activating the pointing and acquisition mode at least initially after having passed sensed shadowing zones not exceeding a defined duration, so that no new satellite signal search is started, the directional antenna instead remaining as pointed prior to the occurrence of each shadowing, characterized in that said information concerning shadowing zones is not output by a sensor system deciding only indirectly on shadowing, but is a direct information output by a sensor system whose line of sight is steered together with the field of view of the directional antenna (5), or is output by a data base in which the shadowing zones resulting in a shadowing pattern are stored.
Each receiving status described is illustrated in FIGs. 1 to 4, where Pin is the received strength and Popt is the maximum strength received with optimum pointing of directional antenna 1, for example a parabolic antenna, received without shadowing. The direction of direct incidence of the satellite signal is identified by the arrow 2 in all four FIGs.
Referring now to FIG. 1 there is illustrated the status for optimum reception in which the main lobe 3 of the directional antenna 1 corresponding to the direction of maximum sensitivity precisely points in the direction of direct incidence 2 of the satellite signal. In this status we thus have Pin = Popt .
Referring now to FIG. 2 there is illustrated the status of slight erroneous pointing of the directional antenna 1 in which the direction of the main lobe 3 of the directional antenna 1 slightly differs from the direction of direct incidence 2 of the satellite signal. In this status we thus have Pin 9:-- Popt.
Referring now to FIG. 3 there is illustrated the status of coarse erroneous pointing of the directional antenna 1 in which the direction of the main lobe 3 of the directional antenna 1 greatly differs from the direction of direct incidence 2 of the satellite signal. In this status we thus have Pln << Popt .
Referring now to FIG. 4 there is illustrated the status in which, although the directional antenna 1 is substantially pointed at the satellite, in other words the direction of the main lobe 3 of the directional antenna 1 agrees with the direction of direct incidence 2 of the satellite signal, a disruptive obstacle 4 exists between the 5 satellite and the directional antenna 1. In the course of the zone of signal shadowing due to the obstacle the strength received can greatly differ from Pin :z~ PoPt to Pin PoPt .
Re-pointing or a signal loss results in a coarse pointing of the directional antenna 1 and thus of the main lobe 3 in the form of a systematic search for the direction of incidence 2 of the satellite signal until a signal strength Pin <G PoPt necessary as a minimum in the status as shown in FIG. 3 is received. Coarse pointing is followed by the acquisition phase during which the strength Pin received via the directional antenna 1 is optimized, i.e.
until in the end the status as shown in FIG. 1 is attained.
After this, during the actual tracking phase of the directional antenna 1, reception in mobile operation is maintained as represented by FIG. 2. If the communications link between the satellite and the mobile directional antenna 1 is disrupted by an obstacle 4, as shown in FIG.
4, because of signal shadowing, a signal loss occurs.
The strength Pin of the received signal fails to indicate whether the cause of the signal loss is coarse erroneous pointing of the directional antenna 1 as shown in FIG. 3 or shadowing due to an obstacle 4 as shown in FIG. 4. The result of the signal loss in any case is a repeat systematic search of the direction of incidence of the satellite signal which in the case of a shadowing is, of course, useless.
Accordingly, a search within a shaded zone is unable to acquire the satellite signal and merely unnecessarily extends the time in searching for the signal. Hitherto, shortening the search time in satellite signal tracking involving directional antennas is only attained by location and position information of the mobile directional antenna, resulting in focusing of the search zone.
A repeat search during scanning of a shaded zone due to an obstacle fails to result in the satellite signal being re-acquired and delays the time in re-acquisition of the signal after leaving the shaded zone. When a train mounting a pointable directional antenna, for example, enters a tunnel or when a mobile obstacle, such as e.g. a truck shadows an antenna provided for pointing on an automobile, a repeat search for the satellite signal is automatically commenced, after a certain. time, in conventional tracking methods.
The invention has the object of perfecting such methods for pointing a vehicular mounted directional antenna of a satellite signal receiver at a communications satellite to minimize the time needed in searching for the signal and thus the duration up to commencing communications after having passed zones of signal shadowing.
In accordance with the invention relating to a smart method of the aforementioned kind this object is achieved expediently to advantage by signal shadowing caused by obstacles in the link between satellite and directional antenna being sensed by means of a sensor system additionally provided on the vehicle and information as to the shadowing zones in the line of sight and/or in the motion range of the directional antenna output and by the pointing and acquisition mode being disabled for the duration of scanning the shadowing zones on the basis of the information obtained by means of the sensor system as to the shadowing zones following the tracking phase or deactivated following a pointing and acquisition mode, despite the received signal dropping below a defined signal level threshold.
Now, unlike in known methods, in the method in accordance with the invention an additional sensor system is consequently included, directly furnishing information as to the shadowing zones of the directional antenna. This information is used in controlling the antenna to prevent searching in a shadowing zone and thus to minimize the time involved in signal acquisition.
In this arrangement the information as to the shadowing zones is made use of to prevent the antenna control in the search status from searching in the shadowing zones and/or in the actual tracking status from reassuming the search status if the antenna control utilizes additional information as to the location and position of the directional antenna.
Advantageous and expedient further embodiments and aspects of the method in accordance with the invention read from the sub-claims relating back to claim 1 directly or indirectly.
A repeat search during scanning of a shaded zone due to an obstacle fails to result in the satellite signal being re-acquired and delays the time in re-acquisition of the signal after leaving the shaded zone. When a train mounting a pointable directional antenna, for example, enters a tunnel or when a mobile obstacle, such as e.g. a truck shadows an antenna provided for pointing on an automobile, a repeat search for the satellite signal is automatically commenced, after a certain. time, in conventional tracking methods.
The invention has the object of perfecting such methods for pointing a vehicular mounted directional antenna of a satellite signal receiver at a communications satellite to minimize the time needed in searching for the signal and thus the duration up to commencing communications after having passed zones of signal shadowing.
In accordance with the invention relating to a smart method of the aforementioned kind this object is achieved expediently to advantage by signal shadowing caused by obstacles in the link between satellite and directional antenna being sensed by means of a sensor system additionally provided on the vehicle and information as to the shadowing zones in the line of sight and/or in the motion range of the directional antenna output and by the pointing and acquisition mode being disabled for the duration of scanning the shadowing zones on the basis of the information obtained by means of the sensor system as to the shadowing zones following the tracking phase or deactivated following a pointing and acquisition mode, despite the received signal dropping below a defined signal level threshold.
Now, unlike in known methods, in the method in accordance with the invention an additional sensor system is consequently included, directly furnishing information as to the shadowing zones of the directional antenna. This information is used in controlling the antenna to prevent searching in a shadowing zone and thus to minimize the time involved in signal acquisition.
In this arrangement the information as to the shadowing zones is made use of to prevent the antenna control in the search status from searching in the shadowing zones and/or in the actual tracking status from reassuming the search status if the antenna control utilizes additional information as to the location and position of the directional antenna.
Advantageous and expedient further embodiments and aspects of the method in accordance with the invention read from the sub-claims relating back to claim 1 directly or indirectly.
Expediently, after having passed sensed shadowing zones not exceeding a defined duration the pointing and acquisition mode is not activated, at least initially, so that no new satellite signal search is started, the directional antenna instead remaining as pointed prior to the occurrence of each shadowing.
After having scanned passed shadowing zones exceeding a defined duration the pointing and acquisition mode can be activated to advantage in thus starting a new satellite signal search.
Subsequent to having scanned a sensed shadowing zone, expediently with activation of the pointing and acquisition mode, it is on the basis of information obtained by means of the sensor system as to the=shadowing zones and/or other historical information focusing the three-dimensional search zone that in the pointing and acquisition mode only zones are searched by the directional antenna which proved to be non-shaded.
Sensing shadowing zones in contrast to zones with a clear line of sight and thus satellite visibility can now be undertaken to advantage by means of a distance measuring sensor steered together with the directional antenna should shadowing zones always occur in the complete receiving range of the directional antenna such as e.g. in train tunnels, whereby obstacles in the near field of view of the directional antenna are sensed by means of the distance measuring sensor having the same angle of aperture as the tracked directional antenna and whose line of sight is steered together with the directional antenna.
After having scanned passed shadowing zones exceeding a defined duration the pointing and acquisition mode can be activated to advantage in thus starting a new satellite signal search.
Subsequent to having scanned a sensed shadowing zone, expediently with activation of the pointing and acquisition mode, it is on the basis of information obtained by means of the sensor system as to the=shadowing zones and/or other historical information focusing the three-dimensional search zone that in the pointing and acquisition mode only zones are searched by the directional antenna which proved to be non-shaded.
Sensing shadowing zones in contrast to zones with a clear line of sight and thus satellite visibility can now be undertaken to advantage by means of a distance measuring sensor steered together with the directional antenna should shadowing zones always occur in the complete receiving range of the directional antenna such as e.g. in train tunnels, whereby obstacles in the near field of view of the directional antenna are sensed by means of the distance measuring sensor having the same angle of aperture as the tracked directional antenna and whose line of sight is steered together with the directional antenna.
Such a distance measuring sensor may be designed to operate to advantage on an ultrasbund basis.
As long as the shadowing zones for a mobile directional antenna are known as a function of the position, sensing the shadowing zones in contrast to zones with a clear line of sight and thus also satellite visibility can now be undertaken to advantage by means of a shadowiiig database, whereby the shadowing zones resulting in a shadowing pattern are stored in the database and the obstacles in the motion range determined by means of position information.
Sensing the shadowing zones in contrast to zones with a clear line of sight and thus also satellite visibility can also be undertaken, however, to advantage by means of an array of infrared sensors steered together with the directional antenna so that an infrared image derived from the array of infrared sensors images the shadowing zones in the full receiving range of the directional antenna on the basis of the temperature differences in a clear line of sight and due to obstacles.
Sensing the shadowing zones, in contrast to zones with a clear line of sight and thus also satellite visibility, can also be undertaken in other variants by analyzing the noise level received by the mobile directional antenna as determined by No = kT where k is the Boltzmann constant and T is the noise temperature in the field of view of the directional antenna and the noise temperature of the directional antenna is obtained from the known integration 5 of all radiating points in the field of view of the directional antenna as given by the equation T = ~~T~,(D,~O)G(D,p}sinOdOd~p 10 where Tb(e,ip) is the temperature of a radiator with the angles 8,,p and G(B,() describes the resulting gain of the antenna. The noise temperature of a mobile directional antenna in the microwave range is between 3 and 100 Kelvin in a clear line of sight depending on the angle of elevation or in excess of 1000 Kelvin when pointed at the sun, whereas in shadowing the ambient noise temperature is in the range of approx. 250 Kelvin to approx. 3500 Kelvin. By means of a noise temperature sensor the noise temperature of the directional antenna can be analyzed with no problem to thus permit reliably distinguishing between shaded zones and a clear line of sight.
The method in accordance with the invention will now be detailed by way of the drawings in which:
FIGs. 1 to 4 each represent in a diagrammatic view a satellite signal reception status as already explained with the directional antenna differingly pointed FIG. 5 represents in three diagrammatic views in sequence the pointing status in each case of a directional antenna mounted on a bus in passing a shadowing zone caused by an obstacle without sensing shadowing, FIG. 6 represents again in three diagrammatic views in sequence the pointing status in each case of a directional antenna mounted on a bus in passing a shadowing zone caused by an obstacle but now with sensing shadowing, FIG. 7 represents diagrammatically the surroundings of a mobile satellite receiver as a hemispherical fisheye image showing the obstacles causing shadowing.
Referring now to FIGs. 5 and 6 makes the advantages afforded by the method in accordance with the invention clearly obvious. Each FIG. 5 and FIG. 6 depicts in three status images in sequence (a), (b) and (c) the pointing status of a directional antenna 5 mounted on a bus 7 moving to the right on a road 6, in passing a shadowing zone caused by an obstacle B. In this arrangement FIG. 5 shows the status sequence of known methods with no sensing of the shadowing whilst FIG. 6 shows the status sequence in the method in accordance with the invention with sensing the shadowing.
Once the satellite transmitting the signals has been correctly sighted by the main lobe 10 of the directional antenna 5 in accordance with the direction of incidence 9 of the satellite signal, as shown in the status images (a) of FIG. 5 and FIG. 6, the search for the satellite signal is initiated after a certain delay as shown in status image (b) in FIG. 5 without sensing shadowing on loss of the satellite signal which, however, is of little sense in the shadowing.
Once the shadowing has passed, it is highly probable that the directional antenna 5 is no longer pointing at the satellite, i.e. the main lobe 10 is no longer pointing in the direction of incidence 9 of the satellite signal, meaning that the satellite signal first needs to be retrieved. This erroneous pointed status is depicted in status image (c) of FIG. 5.
When, contrary thereto, as shown in FIG. 6 the shadowing is sensed. No satellite signal search is started during shadowing, as indicated by status image (b) in FIG. 6 and the satellite communications link is instantly reavailable because of there being no change in the pointing of the directional antenna 5 and its main lobe 10 once the shadowing has passed. This is shown in status image (c) of FIG. 6.
During more lengthy shadowing phases there is a possibility, after the shadowing, of the main lobe 10 of the directional antenna 5 pointing in the wrong direction, in other words no longer in the direction of incidence 9 of the satellite signal, due to a change in direction of the bus 7 and thus of the directional antenna 5 during shadowing, e.g. in a tunnel with a bend. On sensing the shadowing the search for the satellite signal is not started until reception of the satellite signal is again possible which can substantially shorten the pointing and acquisition time.
-- --- --- -----With no historical data at all as to the search zone, the full reception range of the directional antenna, e.g. the complete upper hemisphere needs to be systematically searched for the satellite signal. It is usually the case, however, to minimize the time needed in searching for the signal by making use of historical data in various aspects in focusing the search zone. Thus, knowing the momentary position and approximate orientation of the mobile satellite receiver, for example, furnishes information for focusing the search zone, since this makes the elevation and azimuth range known.
Referring now to FIG. 7 there is illustrated how by way of a diagrammatic fisheye image of the momentary surroundings of the mobile satellite receiver a hemispherical fisheye image located in azimuth/elevation coordinates can be made use of to expedite searching for the signal, by focusing the search to zones not shadowing by obstacles. By means of the sensor system additionally provided on the vehicle in the form of a hemispherical fisheye image, signal shadowing due to obstacles in the link between the satellite and the directional antenna are sensed and information as to the shadowing zones in the field of view and/or motion range of the directional antenna furnished.
Because of the information obtained by the fisheye sensor system as to the shadowing zones the pointing and acquisition mode in the mobile satellite receiver is disabled for the scan duration of shadowing zones after tracking, or deactivated following the pointing and acquisition mode, even when the reception signal has dropped below a defined threshold for the reception signal level which otherwise - in other words when the directional antenna is erroneously pointed - results in the pointing and acquisition mode being activated. Now, it is only after shadowing of longer duration and, of course, also whenever the pointing of the directional antenna is sensed to be wrong that a new search for the satellite signal is started and only in the focused zones not shaded by obstacles.
List of Reference Numerals 1 directional antenna 2 direction of incidence of the satellite signal 10 3 main lobe 4 obstacle 5 directional antenna 6 road 7 bus, vehicle 15 8 obstacle 9 direction of incidence of the satellite signal 10 main lobe
As long as the shadowing zones for a mobile directional antenna are known as a function of the position, sensing the shadowing zones in contrast to zones with a clear line of sight and thus also satellite visibility can now be undertaken to advantage by means of a shadowiiig database, whereby the shadowing zones resulting in a shadowing pattern are stored in the database and the obstacles in the motion range determined by means of position information.
Sensing the shadowing zones in contrast to zones with a clear line of sight and thus also satellite visibility can also be undertaken, however, to advantage by means of an array of infrared sensors steered together with the directional antenna so that an infrared image derived from the array of infrared sensors images the shadowing zones in the full receiving range of the directional antenna on the basis of the temperature differences in a clear line of sight and due to obstacles.
Sensing the shadowing zones, in contrast to zones with a clear line of sight and thus also satellite visibility, can also be undertaken in other variants by analyzing the noise level received by the mobile directional antenna as determined by No = kT where k is the Boltzmann constant and T is the noise temperature in the field of view of the directional antenna and the noise temperature of the directional antenna is obtained from the known integration 5 of all radiating points in the field of view of the directional antenna as given by the equation T = ~~T~,(D,~O)G(D,p}sinOdOd~p 10 where Tb(e,ip) is the temperature of a radiator with the angles 8,,p and G(B,() describes the resulting gain of the antenna. The noise temperature of a mobile directional antenna in the microwave range is between 3 and 100 Kelvin in a clear line of sight depending on the angle of elevation or in excess of 1000 Kelvin when pointed at the sun, whereas in shadowing the ambient noise temperature is in the range of approx. 250 Kelvin to approx. 3500 Kelvin. By means of a noise temperature sensor the noise temperature of the directional antenna can be analyzed with no problem to thus permit reliably distinguishing between shaded zones and a clear line of sight.
The method in accordance with the invention will now be detailed by way of the drawings in which:
FIGs. 1 to 4 each represent in a diagrammatic view a satellite signal reception status as already explained with the directional antenna differingly pointed FIG. 5 represents in three diagrammatic views in sequence the pointing status in each case of a directional antenna mounted on a bus in passing a shadowing zone caused by an obstacle without sensing shadowing, FIG. 6 represents again in three diagrammatic views in sequence the pointing status in each case of a directional antenna mounted on a bus in passing a shadowing zone caused by an obstacle but now with sensing shadowing, FIG. 7 represents diagrammatically the surroundings of a mobile satellite receiver as a hemispherical fisheye image showing the obstacles causing shadowing.
Referring now to FIGs. 5 and 6 makes the advantages afforded by the method in accordance with the invention clearly obvious. Each FIG. 5 and FIG. 6 depicts in three status images in sequence (a), (b) and (c) the pointing status of a directional antenna 5 mounted on a bus 7 moving to the right on a road 6, in passing a shadowing zone caused by an obstacle B. In this arrangement FIG. 5 shows the status sequence of known methods with no sensing of the shadowing whilst FIG. 6 shows the status sequence in the method in accordance with the invention with sensing the shadowing.
Once the satellite transmitting the signals has been correctly sighted by the main lobe 10 of the directional antenna 5 in accordance with the direction of incidence 9 of the satellite signal, as shown in the status images (a) of FIG. 5 and FIG. 6, the search for the satellite signal is initiated after a certain delay as shown in status image (b) in FIG. 5 without sensing shadowing on loss of the satellite signal which, however, is of little sense in the shadowing.
Once the shadowing has passed, it is highly probable that the directional antenna 5 is no longer pointing at the satellite, i.e. the main lobe 10 is no longer pointing in the direction of incidence 9 of the satellite signal, meaning that the satellite signal first needs to be retrieved. This erroneous pointed status is depicted in status image (c) of FIG. 5.
When, contrary thereto, as shown in FIG. 6 the shadowing is sensed. No satellite signal search is started during shadowing, as indicated by status image (b) in FIG. 6 and the satellite communications link is instantly reavailable because of there being no change in the pointing of the directional antenna 5 and its main lobe 10 once the shadowing has passed. This is shown in status image (c) of FIG. 6.
During more lengthy shadowing phases there is a possibility, after the shadowing, of the main lobe 10 of the directional antenna 5 pointing in the wrong direction, in other words no longer in the direction of incidence 9 of the satellite signal, due to a change in direction of the bus 7 and thus of the directional antenna 5 during shadowing, e.g. in a tunnel with a bend. On sensing the shadowing the search for the satellite signal is not started until reception of the satellite signal is again possible which can substantially shorten the pointing and acquisition time.
-- --- --- -----With no historical data at all as to the search zone, the full reception range of the directional antenna, e.g. the complete upper hemisphere needs to be systematically searched for the satellite signal. It is usually the case, however, to minimize the time needed in searching for the signal by making use of historical data in various aspects in focusing the search zone. Thus, knowing the momentary position and approximate orientation of the mobile satellite receiver, for example, furnishes information for focusing the search zone, since this makes the elevation and azimuth range known.
Referring now to FIG. 7 there is illustrated how by way of a diagrammatic fisheye image of the momentary surroundings of the mobile satellite receiver a hemispherical fisheye image located in azimuth/elevation coordinates can be made use of to expedite searching for the signal, by focusing the search to zones not shadowing by obstacles. By means of the sensor system additionally provided on the vehicle in the form of a hemispherical fisheye image, signal shadowing due to obstacles in the link between the satellite and the directional antenna are sensed and information as to the shadowing zones in the field of view and/or motion range of the directional antenna furnished.
Because of the information obtained by the fisheye sensor system as to the shadowing zones the pointing and acquisition mode in the mobile satellite receiver is disabled for the scan duration of shadowing zones after tracking, or deactivated following the pointing and acquisition mode, even when the reception signal has dropped below a defined threshold for the reception signal level which otherwise - in other words when the directional antenna is erroneously pointed - results in the pointing and acquisition mode being activated. Now, it is only after shadowing of longer duration and, of course, also whenever the pointing of the directional antenna is sensed to be wrong that a new search for the satellite signal is started and only in the focused zones not shaded by obstacles.
List of Reference Numerals 1 directional antenna 2 direction of incidence of the satellite signal 10 3 main lobe 4 obstacle 5 directional antenna 6 road 7 bus, vehicle 15 8 obstacle 9 direction of incidence of the satellite signal 10 main lobe
Claims (8)
1. A method of continually pointing a vehicular mounted directional antenna of a satellite signal receiver at a communications satellite transmitting radio signals by means of analyzing the receiving levels of radio signals transmitted by the satellite and received via the directional antenna, tracking being preceded by a pointing and acquisition mode for initial and repeat pointing of the directional antenna at the satellite, activated as soon as the received signal drops below a defined signal level threshold, and signal shadowing caused by obstacles in the link between satellite and directional antenna are sensed by means of a sensor system provided on the vehicle, and information is output by said sensor system which results in disabling said pointing and acquisition mode for the duration of passing the shadowing zones, despite the received signal is dropping below a defined signal level threshold, and in not activating the pointing and acquisition mode at least initially after having passed sensed shadowing zones not exceeding a defined duration, so that no new satellite signal search is started, the directional antenna instead remaining as pointed prior to the occurrence of each shadowing, characterized in that said information concerning shadowing zones is not output by a sensor system deciding only indirectly on shadowing, but is a direct information output by a sensor system whose line of sight is steered together with the field of view of the directional antenna (5), or is output by a data base in which the shadowing zones resulting in a shadowing pattern are stored.
2. The method as set forth in claim 1, characterized in that after having passed sensed shadowing zones exceeding a defined duration, the pointing and acquisition mode is activated in thus starting a new satellite signal search.
3. The method as set forth in claim 2, characterized in that subsequent to having passed a sensed shadowing zone, with activation of the pointing and acquisition mode, it is on the basis of information obtained by means of the sensor system as to the shadowing zones and/or other historical information focusing the three-dimensional search zone that in the pointing and acquisition mode only zones are searched by the directional antenna (5) which proved to be nonshaded.
4. The method as set forth in any one of claims 1 to 3, characterized in that sensing shadowing zones in contrast to zones with a clear line of sight and thus visibility of the satellite is undertaken by means of a distance measuring sensor steered together with the directional antenna (5) should shadowing zones always occur in the complete receiving range of the directional antenna, whereby obstacles (8) in the near field of view of the directional antenna are sensed by means of the distance measuring sensor having the same angle of aperture as the tracked directional antenna and whose line of sight is steered together with the directional antenna.
5. The method as set forth in claim 4, characterized in that said distance measuring sensor operates on an ultrasound basis.
6. The method as set forth in any one of claims 1 to 3, characterized in that, as long as the shadowing zones for a mobile directional antenna (5) are known as a function of the position, sensing the shadowing zones in contrast to zones with a clear line of sight and thus also satellite visibility is undertaken by means of a shadowing database, whereby the shadowing zones resulting in a shadowing pattern are stored in the database and the obstacles (8) in the motion range determined by means of position information.
7. The method as set forth in any one of claims 1 to 3, characterized in that sensing the shadowing zones in contrast to zones with a clear line of sight and thus also satellite visibility is undertaken by means of an array of infrared sensors steered together with the directional antenna (5) so that an infrared image derived from the array of infrared sensors images the shadowing zones in the full receiving range of the directional antenna on the basis of the temperature differences in a clear line of sight and due to obstacles (8).
8. The method as set forth in any one of claims 1 to 3, characterized in that sensing the shadowing zones in contrast to zones with a clear line of sight and thus also satellite visibility is undertaken by analyzing the noise level received by the mobile directional antenna as determined by N o = kT where k is the Boltzmann constant and T is the noise temperature in the field of view of the directional antenna and the noise temperature of the directional antenna is obtained from the known integration of all radiating points in the field of view of the directional antenna as given by the equation where T b(.theta.,.phi.) is the temperature of a radiator with the angles .theta.,.phi., and G(.theta.,.phi.) describes the resulting gain of the antenna, resulting in the noise temperature of a mobile directional antenna in the microwave range being between 3° and 100° Kelvin in a clear line of sight depending on the angle of elevation or in excess of 1000° Kelvin when pointed at the sun, whereas in shadowing the ambient noise temperature is in the range of approx. 250° Kelvin to approx. 350°
Kelvin, so that by means of a noise temperature sensor the noise temperature of the directional antenna can be analyzed to thus permit distinguishing between shaded zones and a clear line of sight.
Kelvin, so that by means of a noise temperature sensor the noise temperature of the directional antenna can be analyzed to thus permit distinguishing between shaded zones and a clear line of sight.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE10332777.0 | 2003-07-17 | ||
| DE2003132777 DE10332777B3 (en) | 2003-07-17 | 2003-07-17 | A method of aligning a vehicle-mounted directional antenna of a satellite signal receiver with a communications satellite |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2473479A1 CA2473479A1 (en) | 2005-01-17 |
| CA2473479C true CA2473479C (en) | 2008-09-16 |
Family
ID=33461996
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002473479A Expired - Lifetime CA2473479C (en) | 2003-07-17 | 2004-07-12 | Method of pointing a vehicular mounted directional antenna of a satellite signal receiver at a communications satellite |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP1498983A1 (en) |
| CA (1) | CA2473479C (en) |
| DE (1) | DE10332777B3 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102008016311B4 (en) | 2007-03-30 | 2022-05-12 | Continental Teves Ag & Co. Ohg | Controlling antennas to increase a vehicle's communication range |
| WO2008119763A1 (en) * | 2007-03-30 | 2008-10-09 | Continental Teves Ag & Co. Ohg | Control of antennae for increasing the communication range of a vehicle |
| DE102008033724A1 (en) * | 2008-07-14 | 2009-09-24 | Siemens Aktiengesellschaft | Method for operating data transmission connection between satellite and railborne vehicle, involves aligning vehicle-sided antenna at end of shading regions in desired orientation before leaving of shading regions |
| DE202016103801U1 (en) * | 2016-07-14 | 2017-10-19 | Deutsches Zentrum für Luft- und Raumfahrt e.V. | Aircraft, airspace surveillance system and computer program |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6413801A (en) * | 1987-07-08 | 1989-01-18 | Aisin Seiki | Attitude controller for antenna on mobile body |
| CA1318394C (en) * | 1988-04-12 | 1993-05-25 | Ryuichi Hiratsuka | Antenna apparatus and attitude control method |
| DE69020319T2 (en) * | 1989-12-11 | 1996-03-14 | Toyoda Chuo Kenkyusho Kk | Mobile antenna system. |
| IT1240809B (en) * | 1990-03-28 | 1993-12-17 | Selenia Spazio Spa Ora Alenia | INTEGRATED SENSOR-ACTUATOR SYSTEM FOR THE CONTROL OF THE AIMING OF ANTENNAS ON BOARD ARTIFICIAL SATELLITES. |
| CN1122169A (en) * | 1994-01-20 | 1996-05-08 | 新日本制铁株式会社 | Satellite-broadcast receiving mobile antenna apparatus |
| US5917446A (en) * | 1995-11-08 | 1999-06-29 | The Charles Stark Draper Laboratory, Inc. | Radio-wave reception system using inertial data in the receiver beamforming operation |
| JP3339358B2 (en) * | 1997-05-09 | 2002-10-28 | 三菱電機株式会社 | Antenna control device |
| KR100335884B1 (en) * | 1999-12-23 | 2002-05-08 | 이계안 | Method for enhancing a satellite antenna tracking |
| KR100713387B1 (en) * | 2000-08-16 | 2007-05-04 | 레이던 컴퍼니 | Safe distance algorithm for adaptive cruise control |
-
2003
- 2003-07-17 DE DE2003132777 patent/DE10332777B3/en not_active Expired - Lifetime
-
2004
- 2004-06-30 EP EP04015289A patent/EP1498983A1/en not_active Withdrawn
- 2004-07-12 CA CA002473479A patent/CA2473479C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP1498983A1 (en) | 2005-01-19 |
| CA2473479A1 (en) | 2005-01-17 |
| DE10332777B3 (en) | 2005-03-10 |
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