CN113328786B - Method and system for acquiring downlink PFD mask of low-orbit constellation system - Google Patents
Method and system for acquiring downlink PFD mask of low-orbit constellation system Download PDFInfo
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Abstract
The invention discloses a method and a system for acquiring a downlink PFD mask of a low-orbit constellation system. The method comprises the following steps: obtaining different value combinations comprising three variables of satellite latitude, elevation angle and azimuth angle of interference beams under the satellite view angle based on the latitude value range of the satellite, the elevation angle value range and the azimuth angle value range of the interference beams under the satellite view angle; traversing all the value combinations to obtain a downlink PFD mask, and executing when traversing each value combination: a, if the satellite can establish a feeder link with a feeder station under the current value combination and an interference beam can irradiate the ground, taking a projection point of the interference beam on the ground as an interfered point, entering B, and otherwise traversing the next value combination; and B, obtaining the PFD of the interfered point, and taking the PFD of the interfered point as a PFD mask corresponding to the current value combination. A simplified and feasible method for acquiring a downlink PFD mask of a low-orbit constellation system is provided.
Description
Technical Field
The invention relates to the field of satellite communication, in particular to a method and a system for acquiring a downlink PFD mask of a low-earth-orbit constellation system.
Background
Currently, in the radio rules of the international telecommunication union ITU, a low Earth Orbit constellation system (LEO) is at a low priority level in frequency coordination priority levels, and a GSO (Geostationary Earth Orbit Satellite) constellation system has a higher frequency coordination priority level than the low Earth Orbit constellation system (LEO), so that a frequency interference avoidance method for the GSO constellation system needs to be formulated to ensure that the LEO does not generate harmful interference on the system with the high priority level, thereby ensuring that the LEO coexists with the GSO constellation system at the same frequency and does not generate frequency interference.
In general, the ITU determines the interference of the low orbit constellation to the GSO satellite through a PFD mask generated by an operator of the low orbit constellation, and the PFD is an english abbreviation of Power Flux Density (Power Flux Density). The ITU-to-satellite mask PFD is defined as the maximum PFD value produced by any spatial station in the non-geostationary orbit constellation system (NGSO) observed from any point on the earth's surface. The following four parameters are defined: 1. an NGSO satellite; 2. latitude of the NGSO satellite subsatellite point; 3. azimuth angle under NGSO satellite view; 4. elevation angle under NGSO satellite view.
Because the PFD mask is generated based on the NGSO location, some assumptions must be made in generating the PFD mask. And some mitigation techniques need to be employed in calculating the mask or otherwise difficult to pass. Without any measures to reduce interference to GSO, the interference can be excessive. The method comprises the steps that network data need to be reported to an international telecommunication union ITU before a low-orbit constellation system sends a satellite, downlink PFD masks of the low-orbit constellation need to be provided in submitted materials, the international telecommunication union ITU tests the provided downlink PFD, and the effectiveness of the network data is confirmed after the test is passed.
Disclosure of Invention
The invention aims to at least solve the technical problems in the prior art, and particularly innovatively provides a method and a system for acquiring a downlink PFD mask of a low-orbit constellation system.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a method for obtaining a downlink PFD mask of a low-orbit constellation system, including: acquiring a latitude value range of a satellite which is the same as the longitude of a feeder station, and an elevation value range and an azimuth value range of an interference beam caused by a satellite feed beam under a satellite view angle, and acquiring different value combinations comprising three variables of the satellite latitude, the elevation angle and the azimuth angle of the interference beam under the satellite view angle based on the latitude value range of the satellite, the elevation angle value range and the azimuth value range of the interference beam under the satellite view angle; traversing all value combinations, and executing when traversing each value combination: step A, judging whether a feed link can be established between a satellite under the current value combination and a feed station and an interference beam can irradiate the ground, if the feed link can be established between the satellite and the feed station and the interference beam can irradiate the ground, taking a projection point of the interference beam on the ground as an interfered point, entering step B, and if not, traversing to the next value combination; step B, obtaining the PFD of the interfered point, and taking the PFD of the interfered point as a PFD mask corresponding to the current value combination; and taking all the PFD masks obtained after traversing all the value combinations as downlink PFD masks of the low-orbit constellation system.
The technical scheme is as follows: a simplified and feasible method for calculating downlink PFD mask of low orbit constellation system is proposed, the method is based on the principle that the interfered point is determined according to satellite latitude and the beam elevation angle and azimuth angle of the interfered point, when the longitude of the satellite is the same as the longitude of the feed station, the PFD of the interfered point determined according to the satellite latitude, the elevation angle and the azimuth angle under the satellite view angle is the largest, because the distance of the interference link is unchanged compared with other longitudes, but the included angle between the direction of the interfered point and the main axis of the feed beam is the smallest, the PFD is the largest, so the PFD of the interfered point can be used as the PFD mask corresponding to the value combination, and the method for calculating the downlink PFD mask can be greatly simplified.
In a preferred embodiment of the present invention, when traversing each value combination, determining whether a satellite under the current value combination can establish a feeder link with a feeder station and an interference beam can irradiate the ground includes: step A1, calculating an elevation angle of the feeder station relative to the satellite based on the satellite latitude in the current value combination, if the elevation angle is smaller than a first elevation angle threshold, considering that the satellite under the current value combination cannot establish a feeder link with the feeder station, and if the elevation angle is not smaller than the first elevation angle threshold, considering that the satellite under the current value combination can establish a feeder link with the feeder station; and A2, calculating an included angle between the interference beam and a connecting line between the satellite and a satellite lower point based on the elevation angle and the azimuth angle of the interference beam at the satellite viewing angle in the current value combination, if the included angle is larger than a first included angle threshold value, considering that the interference beam under the current value combination can not irradiate the ground, and if the included angle is not larger than the first included angle threshold value, considering that the interference beam under the current value combination can irradiate the ground.
The technical scheme is as follows: and invalid value combinations which cannot obtain the PFD of the interfered point are removed from all the value combinations, so that the subsequent calculation is simplified, and the operation speed is improved.
In a preferred embodiment of the present invention, in step a1, calculating an elevation E1 of the feeder station relative to the satellite based on the satellite latitude in the current value combination includes: step A11, calculating the coordinates of the satellite or the satellite subsatellite point or the feeder station in the geocentric coordinate system according to the following formula
Wherein d' represents the distance from the ground center of the satellite or the satellite subsatellite point or the feeder station, lat represents the latitude of the satellite or the satellite subsatellite point or the feeder station, and long represents the longitude of the satellite or the satellite subsatellite point or the feeder station; step A12, according to the coordinates of the satellite, the satellite subsatellite point and the geocentric coordinate system of the feed station, the distance d1 between the satellite and the feed station and the distance h between the satellite and the satellite subsatellite point are obtained; step A13, the elevation angle E1 of the feeder station relative to the satellite is:
wherein acos (·) represents an inverse cosine function, re represents the earth radius; and/or in step a2, based on the elevation angle and azimuth angle of the interference beam at the satellite view angle in the current value combination, calculating an included angle α between the interference beam and the satellite-satellite point-to-satellite line as: α ═ acos (cos (el) × cos (az)), where acos (·) denotes an inverse cosine function, el denotes the elevation angle of the interference beam under the satellite view angle in the current combination of values, and az denotes the azimuth angle of the interference beam under the satellite view angle in the current combination of values.
The technical scheme is as follows: step a1 can quickly calculate the elevation angle E1 of the feeder station relative to the satellite, and step a2 can quickly obtain the included angle α between the interference beam and the satellite-to-satellite point connection under the satellite view.
In a preferred embodiment of the present invention, in step B, after obtaining the off-axis angle between the interfered point and the main axis of the feed beam, if the interfered point satisfies the avoidance condition, a preset first PFD value is used as a PFD mask corresponding to the current value combination, and if the interfered point does not satisfy the avoidance condition, the PFD of the interfered point is used as a PFD mask corresponding to the current value combination; the avoiding condition comprises that an included angle between the satellite antenna and the direction of the interfered point is smaller than an initial satellite-borne isolation angle of the satellite.
The technical scheme is as follows: and marking and distinguishing interfered points meeting the avoidance condition through the first PFD value.
In a preferred embodiment of the present invention, if an interfered point meets an avoidance condition, the method further includes an interference avoidance step, where the interference avoidance step includes step one, or the interference avoidance step includes steps one and two: step one, if the latitude of a satellite in the current value combination is lower than that of a feed station, increasing the satellite isolation angle of the satellite, and if the included angle between a satellite antenna and the direction of an interfered point is smaller than the set satellite isolation angle, closing a satellite feed beam; and step two, acquiring the distance between the interfered point and the satellite based on the current value combination, wherein the larger the distance between the interfered point and the satellite is, the larger the on-satellite isolation angle of the satellite is adjusted, and the smaller the distance between the interfered point and the satellite is, the smaller the on-satellite isolation angle of the satellite is adjusted.
The technical scheme is as follows: effective evasion measures and a reasonable on-satellite isolation setting method are provided, and on-satellite isolation angles are not uniformly set, so that the setting of the on-satellite isolation angles can be reduced as much as possible, the on-satellite isolation angles approach a PFD threshold value specified by ITU as much as possible, and further the influence on the use of the low-orbit constellation is reduced.
In a preferred embodiment of the present invention, in step B, the PFD of the interfered point is obtained by using the following formula: PFD ═ Pt + Gt (θ) -10log10(4πd2) (ii) a Wherein Pt represents satellite transmission power set in a low-earth constellation system; gt (theta) represents the gain of the satellite transmitting antenna at the interfered point, theta represents the included angle between the satellite antenna and the interfered point, and Gt (theta) can be determined according to the satellite antenna information after theta is determined; d represents interfered point and satelliteThe distance of the star.
In a preferred embodiment of the invention, the equation is based on
Obtaining the distance d between the interfered point and the satellite; wherein alpha represents an elevation angle and an azimuth angle of an interference wave beam under a satellite view angle in the current value combination, and an included angle between the interference wave beam and a satellite subsatellite point connecting line; e2 represents the elevation angle of the interfered point to the satellite based on the satellite latitude in the current value combination; re represents the earth radius.
The technical scheme is as follows: based on the conversion between the geocentric coordinate system and the satellite coordinate system, the distance d between the interfered point and the satellite can be rapidly obtained.
In a preferred embodiment of the present invention, in step B, the obtaining of the angle θ between the satellite antenna and the interfered point direction includes: step B1, according to the coordinates of the satellite, the satellite down-pointing point and the earth center coordinate system of the feed station, the distance d1 between the satellite and the feed station, the distance d2 between the feed station and the satellite down-pointing point, and the distance h between the satellite and the satellite down-pointing point are obtained, and the included angle beta between the connection line of the satellite and the feed station and the connection line of the satellite and the satellite down-pointing point is obtained:
wherein acos (·) represents an inverse cosine function; step B2, obtaining the coordinate (X) of the feed station in the satellite coordinate system according to the included angle theta between the satellite antenna and the interfered point directionS,YS,ZS)：
Obtaining the coordinates (Xi, Yi, Zi) of the interfered point in the satellite coordinate system according to the distance d between the interfered point and the satellite:
wherein el represents the elevation angle of the interference beam under the satellite view angle in the current value combination, and az represents the azimuth angle of the interference beam under the satellite view angle in the current value combination; step B3, according to the coordinates of the feeder station and the interfered point in the satelliteCoordinates in the system obtain the distance d3 from the interfered point to the power feeding station; and step B4, in a triangle formed by taking the satellite, the feeder station and the interfered point as vertexes, under the condition that the distance d1 between the satellite and the feeder station, the distance d3 between the interfered point and the feeder station and the distance d between the interfered point and the satellite are known, obtaining an included angle between a connecting line of the satellite and the feeder station and a connecting line between the satellite and the interfered point according to a triangle theorem, and taking the included angle as an included angle theta between the satellite antenna and the interfered point.
The technical scheme is as follows: the satellite coordinate system coordinate of the interfered point under the satellite view angle is obtained based on the conversion of the geocentric coordinate system and the satellite coordinate system, and the included angle theta between the satellite antenna and the interfered point direction can be quickly, simply and conveniently determined.
In a preferred embodiment of the invention, the method for setting the satellite transmitting power Pt comprises the steps of calculating the distance between the satellite and the feeder station under the current value combination, wherein the larger the distance between the satellite and the feeder station is, the larger the satellite transmitting power Pt is adjusted, and the smaller the distance between the satellite and the feeder station is, the smaller the satellite transmitting power Pt is adjusted.
The technical scheme is as follows: the satellite transmit power control strategy described above can reduce the PFD, reducing the equivalent power flux density epfd of the entire low-orbit constellation at that location.
In order to achieve the above object, according to a second aspect of the present invention, the present invention provides a system including an information obtaining module and a processing module, wherein the information obtaining module obtains a latitude value range of a satellite having the same longitude as a feeder station, an elevation value range and an azimuth value range of an interference beam caused by a satellite feeder beam under a satellite view angle, and transmits the latitude value range, the elevation value range and the azimuth value range to the processing module, and the processing module executes the steps of the method for obtaining a downlink PFD mask of a low earth orbit constellation system according to the present invention to obtain a downlink PFD mask of the low earth orbit constellation system.
The technical scheme is as follows: the system is based on the conversion of a geocentric coordinate system and a satellite coordinate system, and can quickly and simply determine the ground PFD (pulse frequency response) of the ground interfered direction according to the satellite latitude, the interference beam elevation angle and the azimuth angle under the satellite view angle.
Drawings
Fig. 1 is a schematic flow chart of an application scenario of a downlink PFD mask acquisition method of a low-orbit constellation system according to the present invention;
fig. 2 is a schematic diagram of an interference scenario of a low-orbit constellation system with downlink interference to a ground station of a GSO constellation system in the prior art;
fig. 3 is a schematic diagram of a feeder station to satellite elevation in the method for acquiring a downlink PFD mask of a low-earth constellation system according to the present invention;
fig. 4 is a schematic view of a satellite view in the method for acquiring a downlink PFD mask of a low-earth constellation system according to the present invention;
fig. 5 is a simulation schematic diagram of downlink PFD mask simulation ITU test obtained by the method for obtaining downlink PFD mask of low-orbit constellation system of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.
In the description of the present invention, unless otherwise specified and limited, it is to be noted that the terms "mounted," "connected," and "connected" are to be interpreted broadly, and may be, for example, a mechanical connection or an electrical connection, a communication between two elements, a direct connection, or an indirect connection via an intermediate medium, and specific meanings of the terms may be understood by those skilled in the art according to specific situations.
The invention discloses a method for acquiring a downlink PFD mask of a low-orbit constellation system, which comprises the following steps:
acquiring a latitude value range of a satellite which is the same as the longitude of a feeder station, and an elevation value range and an azimuth value range of an interference beam caused by a satellite feed beam under a satellite view angle, and acquiring different value combinations comprising three variables of the satellite latitude, the elevation angle and the azimuth angle of the interference beam under the satellite view angle based on the latitude value range of the satellite, the elevation angle value range and the azimuth value range of the interference beam under the satellite view angle; traversing all value combinations, and executing when traversing each value combination: step A, judging whether the satellite under the current value combination can establish a feed link with a feed station and an interference beam can irradiate the ground, if the satellite can establish the feed link with the feed station and the interference beam can irradiate the ground, taking a projection point of the interference beam on the ground as an interfered point, entering step B, and if not, traversing to the next value combination; step B, obtaining the PFD of the interfered point, and taking the PFD of the interfered point as a PFD mask corresponding to the current value combination; and taking all the PFD masks obtained after traversing all the value combinations as downlink PFD masks of the low-orbit constellation system.
In this embodiment, after the low orbit constellation system is designed, the latitude value range of the satellite having the same longitude as that of the feed station, and the elevation value range and the azimuth value range of the interference beam caused by the satellite feed beam under the satellite view angle can be obtained from the low orbit constellation system design information. Preferably, a latitude value step, an interference beam elevation value step and an interference beam azimuth value step are respectively set, and a plurality of different value combinations are obtained according to the value steps in the latitude value range of the satellite, the elevation value range and the azimuth value range of the interference beam under the satellite view angle.
In the prior art, a low-orbit constellation system LEO is a schematic diagram of an interference scene of downlink interference of a GSO constellation system ground station, and the orbit height of the GSO constellation system is greater than the LEO orbit height. The method is used for detecting the FSS service of the low-orbit constellation system during calculation of the downlink PFD mask, namely the interference of the low-orbit satellite feed beam on a ground station GSO ES of the GSO constellation system, and the judgment can reach the specified protection standard. The GSO satellites are all above the equator, therefore, the ground station GSO ES of the GSO satellite is pointing towards the equator direction, when the latitudes of the feeder station and the GSO constellation ground station are both higher than the low-orbit satellite and are in the same direction (i.e. the latitudes of the feeder station and the GSO constellation ground station are not in the range of south latitude or north latitude, the same direction is called), as shown in fig. 2, the direction of the feed beam of the low-orbit constellation satellite is pointing towards the feeder station, i.e. pointing towards the ground station of the GSO satellite, and the receiving antenna of the ground station of the GSO satellite is pointing towards the equator, i.e. pointing towards the direction of the low-orbit satellite, at this time, the attenuation of the interference beam and the attenuation received by the GSO ground station are smaller, and larger interference can be generated. When the feed station and the GSO constellation ground station are in different directions of the low orbit satellite or the latitude of the GSO constellation ground station is lower than that of the low orbit satellite, the feed beam direction of the low orbit satellite and the receiving antenna of the GSO constellation ground station point in a non-intersecting way, and then the attenuation of the interference beam and the attenuation received by the GSO ground station are larger, and the generated interference is smaller.
In this embodiment, the satellite feed beam refers to a beam emitted when a satellite antenna points to a feed station, and due to the antenna side lobe effect, the feed beam has beam components in other directions except for the beam component pointing to the feed station, and these beam components are called interference beams, that is, the interference beams are side lobe interference of the feed beam. In a preferred embodiment, when traversing each combination of values, determining whether the satellite under the current combination of values can establish a feeder link with the feeder station and the interference beam can illuminate the ground includes:
step A1, calculating the elevation angle of the feeder station relative to the satellite based on the satellite latitude in the current value combination, if the elevation angle is smaller than a first elevation angle threshold, it is indicated that the satellite can not feed at the latitude, and will not interfere any ground area, considering that the satellite under the current value combination can not establish a feeder link with the feeder station, and can abandon the current value combination, enter the next value combination judgment, if the elevation angle is not smaller than the first elevation angle threshold, considering that the satellite under the current value combination can establish a feeder link with the feeder station; the first elevation threshold may be preset according to low-orbit constellation system design information.
And step A2, calculating an included angle between the interference beam and a connecting line between the satellite and a satellite lower point based on the elevation angle and the azimuth angle of the interference beam at the satellite viewing angle in the current value combination, if the included angle is larger than a first included angle threshold value, considering that the interference beam under the current value combination can not irradiate the ground, and if the included angle is not larger than the first included angle threshold value, considering that the interference beam under the current value combination can irradiate the ground. The first angle threshold may be preset.
In this embodiment, preferably, as shown in fig. 3, in step a1, calculating an elevation E1 of the feeder station relative to the satellite based on the satellite latitude in the current value combination includes:
step A11, calculating the coordinates (X, Y, Z) of the satellite or the satellite subsatellite point or the feeder station in the geocentric coordinate system according to the following formula:
Step A12, according to the coordinates of the satellite, the satellite subsatellite point and the geocentric coordinate system of the feed station, the distance d1 between the satellite and the feed station and the distance h between the satellite and the satellite subsatellite point are obtained; it is known that finding the distance between two points from two coordinates is a conventional technique, and is not described herein.
Step A13, the elevation angle E1 of the feeder station relative to the satellite is:
In a preferred embodiment, as shown in fig. 4, in step a2, based on the elevation angle and the azimuth angle of the interference beam under the satellite view angle in the current value combination, the included angle α between the interference beam and the satellite-satellite point-to-point line is determined as follows: α ═ acos (cos (el) × cos (az)), where acos (·) denotes an inverse cosine function, el denotes the elevation angle of the interference beam under the satellite view angle in the current combination of values, and az denotes the azimuth angle of the interference beam under the satellite view angle in the current combination of values. In fig. 4, the positive Y-axis direction in the view angle of the satellite is the direction pointing to the earth center, and the positive Z-axis direction is the north direction of the satellite.
In a preferred embodiment, in step B, after obtaining an off-axis angle between the interfered point and the main axis of the feed beam, the off-axis angle is an included angle θ between the satellite antenna and the interfered point, if the interfered point satisfies an avoidance condition, taking a preset first PFD value as a PFD mask corresponding to a current value combination, and if the interfered point does not satisfy the avoidance condition, taking the PFD of the interfered point as the PFD mask corresponding to the current value combination; the avoiding condition comprises that the included angle between the satellite antenna and the direction of the interfered point is smaller than the initial on-satellite isolation angle of the satellite. The first PFD value is preferably, but not limited to, -1000.
In a preferred embodiment, if the interfered point meets the avoidance condition, the method further comprises an interference avoidance step, wherein the interference avoidance step comprises a first step, or the interference avoidance step comprises a first step and a second step:
step one, if the latitude of a satellite in the current value combination is lower than that of a feed station, increasing the satellite isolation angle of the satellite, and if the included angle between a satellite antenna and the direction of an interfered point is smaller than the set satellite isolation angle, closing a satellite feed beam;
and step two, acquiring the distance between the interfered point and the satellite based on the current value combination, wherein the larger the distance between the interfered point and the satellite is, the larger the on-satellite isolation angle of the satellite is adjusted, and the smaller the distance between the interfered point and the satellite is, the smaller the on-satellite isolation angle of the satellite is adjusted.
In this embodiment, when the low-earth satellite latitude is smaller than the feeder station latitude, the feeder beam transmitted by the low-earth satellite has a higher probability of causing larger interference to the ground station of the GSO constellation system, and therefore a larger on-satellite isolation angle is required, compared to the case where the low-earth satellite latitude is larger than the feeder station latitude. Therefore, the on-satellite isolation angle can be more reasonably set according to the satellite latitude instead of being uniformly set. The size of the on-satellite isolation angle can be considered by combining the distance between the satellite and the interfered point on the ground in the interfered direction, because the larger the distance is, the smaller the interference is, and the larger the on-satellite isolation angle can be set.
In a preferred embodiment, in step B, the PFD of the interfered point is obtained using the following formula: PFD ═ Pt + Gt (θ) -10log10(4πd2) (ii) a Wherein Pt represents satellite transmission power set in a low-earth constellation system; gt (theta) represents the gain of a satellite transmitting antenna at the interfered point, theta represents the included angle between the satellite antenna and the interfered point, and Gt (theta) can be determined according to the satellite antenna information after theta is determined; d represents the distance of the interfered point from the satellite.
In a preferred embodiment, the equation is based on
Obtaining the distance d between the interfered point and the satellite; wherein alpha represents an elevation angle and an azimuth angle of an interference wave beam under a satellite view angle in the current value combination, and an included angle between the interference wave beam and a connecting line between a satellite and a satellite sub-satellite point; e2 represents the elevation angle of the interfered point to the satellite based on the satellite latitude in the current value combination; re represents the earth radius.
In a preferred embodiment, in step B, the process of obtaining the angle θ between the satellite antenna and the direction of the interfered point includes:
step B1, according to the coordinates of the satellite, the satellite down-pointing point and the earth center coordinate system of the feed station, the distance d1 between the satellite and the feed station, the distance d2 between the feed station and the satellite down-pointing point, and the distance h between the satellite and the satellite down-pointing point are obtained, and the included angle beta between the connection line of the satellite and the feed station and the connection line of the satellite and the satellite down-pointing point is obtained:
step B2, according to satelliteThe included angle theta between the antenna and the direction of the interfered point is used for acquiring the coordinate (X) of the power feeding station in a satellite coordinate systemS,YS,ZS)：
Obtaining the coordinates (Xi, Yi, Zi) of the interfered point in the satellite coordinate system according to the distance d between the interfered point and the satellite:
step B3, obtaining the distance d3 from the interfered point to the feeder station according to the coordinates of the feeder station and the interfered point in a satellite coordinate system;
and step B4, in a triangle formed by taking the satellite, the feeder station and the interfered point as vertexes, under the condition that the distance d1 between the satellite and the feeder station, the distance d3 between the interfered point and the feeder station and the distance d between the interfered point and the satellite are known, obtaining an included angle between a connecting line of the satellite and the feeder station and a connecting line between the satellite and the interfered point according to a triangle theorem, and taking the included angle as an included angle theta between the satellite antenna and the interfered point.
In a preferred embodiment, the setting method of the satellite transmitting power Pt is that under the current value combination, the distance between the satellite and the feeder station is calculated, the larger the distance between the satellite and the feeder station is, the larger the satellite transmitting power Pt is adjusted, and the smaller the distance between the satellite and the feeder station is, the smaller the satellite transmitting power Pt is adjusted. When the satellite is in the visual field of the feeder station, the distance between the satellite and the feeder station is calculated in real time, and the transmitting power of the satellite feed beam is adjusted accordingly.
In an application scenario of the method for acquiring the downlink PFD mask of the low-orbit constellation system provided by the present invention, a specific flowchart is shown in fig. 1, and specifically includes the following steps:
step 1: configuring longitude and latitude of a feeder station and satellite longitude;
step 2: setting a satellite latitude;
step 3: calculating coordinates of a sub-satellite point, a satellite and a power feeding station in the geocentric coordinate system;
step 4: according to the coordinates of each position, the distance from the subsatellite point to the feeder station and the distance from the feeder station to the satellite are calculated;
step 5: calculating the elevation angle between the power feeding station and the satellite at the current latitude, if the elevation angle is smaller than the minimum elevation angle of power feeding, indicating that the satellite cannot feed at the latitude, namely, the satellite cannot interfere with any place, turning to step2, calculating the conditions of other latitudes, and otherwise, turning to the next step;
step 6: calculating an included angle between a connection line of the satellite and the feed station and a connection line of the satellite and the sub-satellite point;
step 7: solving the coordinates of the feeder station in a satellite coordinate system;
step 8: setting the elevation angle and the azimuth angle of an interference wave beam under a satellite view angle;
step 9: calculating an included angle alpha between the interference wave beam and a connecting line between the satellite and the off-satellite point;
step 10: judging the size of alpha, if the size of alpha is larger than a certain threshold value, the interference beam of the satellite cannot irradiate the ground, turning to step8, and otherwise, turning to the next step;
step 11: calculating the distance from the satellite interference wave beam to the ground;
step 12: calculating the coordinates of the interfered point in a satellite coordinate system;
step 13: calculating the distance between the interfered point and the power feeding station;
step 14: solving the off-axis angle between the satellite interference wave beam and the main axis of the feed wave beam;
step 15: judging whether the avoidance strategy is met, if the avoidance is needed, turning to step8, otherwise, turning to the next step;
step 16: the pfd at the interfered site is determined.
The downlink PFD mask obtained according to the downlink PFD mask of the low-orbit constellation system of the present invention is subjected to ITU test, and the simulation result is shown in fig. 5.
The invention also discloses a system for acquiring the downlink PFD mask of the low orbit constellation system, which comprises an information acquisition module and a processing module, wherein the information acquisition module acquires the latitude value range of a satellite with the same longitude as the feed station, the elevation value range and the azimuth value range of an interference beam caused by a satellite feed beam under the satellite view angle and transmits the latitude value range and the elevation value range to the processing module, and the processing module executes the steps of the method for acquiring the downlink PFD mask of the low orbit constellation system to acquire the downlink PFD mask of the low orbit constellation system.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims (10)
1. A method for obtaining a downlink PFD mask of a low-orbit constellation system is characterized by comprising the following steps:
acquiring a latitude value range of a satellite which is the same as the longitude of a feeder station, and an elevation value range and an azimuth value range of an interference beam caused by a satellite feed beam under a satellite view angle, and acquiring different value combinations comprising three variables of the satellite latitude, the elevation angle and the azimuth angle of the interference beam under the satellite view angle based on the latitude value range of the satellite, the elevation angle value range and the azimuth value range of the interference beam under the satellite view angle;
traversing all value combinations, and executing when traversing each value combination:
step A, judging whether a feed link can be established between a satellite under the current value combination and a feed station and an interference beam can irradiate the ground, if the feed link can be established between the satellite and the feed station and the interference beam can irradiate the ground, taking a projection point of the interference beam on the ground as an interfered point, entering step B, and if not, traversing to the next value combination;
step B, obtaining the PFD of the interfered point, and taking the PFD of the interfered point as a PFD mask corresponding to the current value combination;
and taking all the PFD masks obtained after traversing all the value combinations as downlink PFD masks of the low-orbit constellation system.
2. The method according to claim 1, wherein when traversing each of the combinations of values, determining whether the satellite under the current combination of values can establish a feeder link with a feeder station and an interference beam can illuminate the ground, specifically comprises:
step A1, calculating the elevation angle of a feeder station relative to a satellite based on the satellite latitude in the current value combination, if the elevation angle of the feeder station relative to the satellite is smaller than a first elevation angle threshold value, considering that the satellite under the current value combination can not establish a feeder link with the feeder station, and if the elevation angle of the feeder station relative to the satellite is not smaller than the first elevation angle threshold value, considering that the satellite under the current value combination can establish a feeder link with the feeder station;
and A2, calculating an included angle between the interference beam and a connecting line between the satellite and a satellite lower point based on the elevation angle and the azimuth angle of the interference beam at the satellite viewing angle in the current value combination, if the included angle is larger than a first included angle threshold value, considering that the interference beam under the current value combination can not irradiate the ground, and if the included angle is not larger than the first included angle threshold value, considering that the interference beam under the current value combination can irradiate the ground.
3. The method of claim 2, wherein the step a1 of calculating an elevation E1 of the feeder station with respect to the satellite based on the satellite latitude in the current combination of values includes:
step A11, calculating the coordinates (X, Y, Z) of the satellite or the satellite subsatellite point or the feeder station in the geocentric coordinate system according to the following formula:
step A12, according to the coordinates of the satellite, the satellite subsatellite point and the geocentric coordinate system of the feed station, the distance d1 between the satellite and the feed station and the distance h between the satellite and the satellite subsatellite point are obtained;
step A13, the elevation angle E1 of the feeder station relative to the satellite is:
and/or in step a2, based on the elevation angle and azimuth angle of the interference beam at the satellite view angle in the current value combination, calculating an included angle α between the interference beam and the satellite-satellite point-to-satellite line as: α ═ acos (cos (el) × cos (az)), where acos (·) denotes an inverse cosine function, el denotes the elevation angle of the interference beam under the satellite view angle in the current combination of values, and az denotes the azimuth angle of the interference beam under the satellite view angle in the current combination of values.
4. The method according to claim 1, wherein in step B, after the off-axis angle between the interfered point and the main axis of the feed beam is obtained, if the interfered point satisfies the avoidance condition, the preset first PFD value is used as the PFD mask corresponding to the current value combination, and if the interfered point does not satisfy the avoidance condition, the PFD of the interfered point is used as the PFD mask corresponding to the current value combination;
the avoiding condition comprises that the included angle between the satellite antenna and the direction of the interfered point is smaller than the initial on-satellite isolation angle of the satellite.
5. The method for acquiring the downlink PFD mask of the low-orbit constellation system according to claim 4, wherein if the interfered point satisfies an avoidance condition, the method further comprises an interference avoidance step, wherein the interference avoidance step comprises the first step, or the interference avoidance step comprises the first step and the second step:
step one, if the latitude of a satellite in the current value combination is lower than that of a feed station, increasing the satellite isolation angle of the satellite, and if the included angle between a satellite antenna and the direction of an interfered point is smaller than the set satellite isolation angle, closing a satellite feed beam;
and step two, acquiring the distance between the interfered point and the satellite based on the current value combination, wherein the larger the distance between the interfered point and the satellite is, the larger the on-satellite isolation angle of the satellite is adjusted, and the smaller the distance between the interfered point and the satellite is, the smaller the on-satellite isolation angle of the satellite is adjusted.
6. The method for acquiring downlink PFD mask of low-orbit constellation system according to claim 1, wherein in step B, the PFD of the interfered point is acquired by using the following formula:
PFD＝Pt+Gt(θ)-10log10(4πd2) (ii) a Wherein Pt represents satellite transmission power set in a low-earth constellation system; gt (theta) represents the gain of the satellite transmitting antenna at the interfered point, theta represents the included angle between the satellite antenna and the interfered point, and Gt (theta) can be determined according to the satellite antenna information after theta is determined; d represents the distance of the interfered point from the satellite.
7. The method of claim 6, wherein the method for obtaining the downlink PFD mask of the low-orbit constellation system is based on the equation
Obtaining the distance d between the interfered point and the satellite;
wherein alpha represents an elevation angle and an azimuth angle of an interference wave beam under a satellite view angle in the current value combination, and an included angle between the interference wave beam and a satellite subsatellite point connecting line; e2 represents the elevation angle of the interfered point to the satellite based on the satellite latitude in the current value combination; re represents the earth radius and h represents the satellite-to-satellite sub-satellite point distance.
8. The method according to claim 7, wherein in step B, the process of obtaining the angle θ between the satellite antenna and the interfered point direction includes:
step B1, according to the coordinates of the satellite, the satellite down-pointing point and the earth center coordinate system of the feed station, the distance d1 between the satellite and the feed station, the distance d2 between the feed station and the satellite down-pointing point, and the distance h between the satellite and the satellite down-pointing point are obtained, and the included angle beta between the connection line of the satellite and the feed station and the connection line of the satellite and the satellite down-pointing point is obtained:
step B2, obtaining the coordinate (X) of the feed station in the satellite coordinate system according to the included angle theta between the satellite antenna and the interfered point directionS,YS,ZS)：
Obtaining the coordinates (Xi, Yi, Zi) of the interfered point in the satellite coordinate system according to the distance d between the interfered point and the satellite:
Step B3, obtaining the distance d3 from the interfered point to the feeder station according to the coordinates of the feeder station and the interfered point in the satellite coordinate system;
and step B4, in a triangle formed by taking the satellite, the feeder station and the interfered point as vertexes, under the condition that the distance d1 between the satellite and the feeder station, the distance d3 between the interfered point and the feeder station and the distance d between the interfered point and the satellite are known, obtaining an included angle between a connecting line of the satellite and the feeder station and a connecting line between the satellite and the interfered point according to a triangle theorem, and taking the included angle as an included angle theta between the satellite antenna and the interfered point.
9. The method for acquiring the downlink PFD mask of the low earth orbit constellation system as recited in claim 6, wherein the method for setting the satellite transmitting power Pt is to calculate the distance between the satellite and the feeder station under the current value combination, the larger the distance between the satellite and the feeder station is, the larger the satellite transmitting power Pt is adjusted, and the smaller the distance between the satellite and the feeder station is, the smaller the satellite transmitting power Pt is adjusted.
10. A system for acquiring downlink PFD mask of low earth orbit constellation system is characterized in that the system comprises an information acquisition module and a processing module, wherein the information acquisition module acquires a latitude value range of a satellite with the same longitude as that of a feeder station, an elevation value range and an azimuth value range of interference beam caused by satellite feed beam under satellite view angle, and transmits the latitude value range and the elevation value range to the processing module, and the processing module executes the steps of the method for acquiring downlink PFD mask of low earth orbit constellation system according to any one of claims 1 to 9 to acquire downlink PFD mask of low earth orbit constellation system.
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