Low earth orbit satellite signal space incoming direction simulation method

Abstract

The invention belongs to the field of satellite signal simulation, and discloses a low-orbit satellite signal space incoming direction simulation method, which comprises the following steps of: constructing a hemispherical test environment, calculating the trajectory projection of a satellite on a hemispherical surface, and controlling an unmanned aerial vehicle to fly along the trajectory projection of the hemispherical surface. According to the semi-spherical test environment and the flight path control method constructed by the invention, the unmanned aerial vehicle forwards the low-orbit satellite simulation signal generated by the original infield simulation test environment, so that the low-orbit satellite signal space incoming direction simulation is realized, and the development of the complete machine simulation test on the communication terminal is supported. Based on the wireless test environment constructed by the invention, the blank of a test link between an infield simulation test and an outfield real satellite test can be filled, and the outfield real satellite test efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the field of satellite signal simulation, and mainly relates to a method for simulating the spatial orientation of low-orbit satellite signals. Background Art

[0002] At present, there are two main methods for low-orbit technology research and development and equipment development: indoor simulation testing and outdoor satellite measurement. Indoor simulation testing generates low-orbit satellite simulation signals, which are injected into the communication terminal host through RF cables to form a wired test environment; outdoor satellite measurement mainly uses the signal processing payload of the on-orbit satellite and the onboard phased array antenna to generate real low-orbit signals. After transmission through space, they are radiated to the antenna aperture of the communication terminal, forming a wireless test environment with the entire communication terminal. Generally, outdoor satellite measurement is carried out after the indoor simulation test is completed. However, the above method has the following shortcomings:

[0003] (1) The indoor simulation test is a wired test and cannot simulate the communication terminal antenna or the entire device including the antenna, so the test is not comprehensive.

[0004] (2) Field satellite measurement is a wireless test that can be used to test the entire device. However, because it relies on real satellite orbits, the test scenarios are limited and difficult to reproduce, which is not conducive to troubleshooting problems and conducting boundary tests.

[0005] (3) There is a lack of transition between the indoor simulation test and the outdoor satellite measurement, which can easily lead to frequent problems during the outdoor real-satellite test, wasting precious orbital resources and human resources, and is extremely unfavorable to the research of new waveforms and new technologies. Summary of the invention

[0006] The purpose of the present invention is to provide a low-orbit satellite signal spatial simulation method to meet the needs of low-orbit satellite waveform verification, so as to support waveform research and technical verification experiments when there are insufficient orbital resources or no real satellites.

[0007] The technical solution adopted by the present invention is:

[0008] A method for simulating the spatial direction of a low-orbit satellite signal comprises the following steps:

[0009] Step 1: Using the test point as the coordinate origin and sphere center, a hemispherical test environment is constructed in the ENU station coordinate system;

[0010] Step 2, calculating the trajectory projection of the satellite in the hemispherical test environment according to the satellite coordinates, the sphere center coordinates and the sphere radius;

[0011] Step 3, establish a time reference, control the UAV to fly along the trajectory projection in the hemispherical test environment, and appear at the specified coordinate point at the specified time.

[0012] Furthermore, the specific process of step 1 is as follows:

[0013] Step 101, select a test point, the test point and its surrounding areas allow drones to take off and land, the test airspace has no obvious obstruction, and calibrate the geodetic coordinates of the test point;

[0014] Step 102, establishing the ENU station coordinate system with the test point as the coordinate origin;

[0015] Step 103, constructing a three-dimensional sphere with the test point as the sphere center and R as the radius, wherein the sphere is divided into upper and lower parts by the EN plane of the ENU coordinate system, and the upper hemisphere is a hemispherical test environment;

[0016] The calculation method of the sphere radius R is as follows:

[0017] The beam width of the communication simulation antenna is D PS , the receiving beam width is D PR , the receiving beam width of the communication terminal antenna is D TR , the beam width is D TS , the UAV position control accuracy is δ, it can be concluded that:

[0018] R≥360°δ / (πD PS );

[0019] R≥360°δ / (πD PR );

[0020] R≥360°δ / (πD TR );

[0021] R≥360°δ / (πD TS );

[0022] Take the maximum value and record it as R 0 , we can get:

[0023] R 0 =360°δ / π / min{D PS , D PR , D TR , D TS};

[0024] Take R≥(1.5~2)R 0 .

[0025] Furthermore, the specific process of step 2 is:

[0026] Step 201, calculating the coordinates of the visible satellite S observed from the test point at a certain time in the ECEF rectangular coordinate system according to the satellite ephemeris;

[0027] Step 202: Convert the coordinates of satellite S in the ECEF rectangular coordinate system to the ENU station coordinate system, and calculate the elevation angle θ and azimuth angle of satellite S in the ENU station coordinate system.

[0028] Step 203, based on the sphere radius R and the satellite pitch angle θ and azimuth angle Calculate the coordinates of the satellite projection S' in the ENU station coordinate system;

[0029] Step 204, converting the coordinates of the satellite projection S' in the ENU station coordinate system to the ECEF rectangular coordinate system to obtain the coordinates of the satellite projection S' in the ECEF rectangular coordinate system;

[0030] Step 205, converting the coordinates of the satellite projection S' in the ECEF rectangular coordinate system to the geodetic coordinate system to obtain the coordinates of the satellite projection S' in the geodetic coordinate system;

[0031] Step 206 , as the satellite moves, steps 201 to 205 are repeated to obtain a series of coordinate points of the satellite projection S′ in the geodetic coordinate system, ie, the trajectory projection of the satellite in the hemispherical test environment.

[0032] Furthermore, the specific process of step 3 is as follows:

[0033] Step 301, establish a time reference, which has two modes: external timing and autonomous timing. External timing refers to externally connecting NTP and B-code time information for timing, which is synchronized with the external time system; autonomous timing refers to the UAV control system autonomously receiving Beidou signals for timing, which is synchronized with Beidou time.

[0034] Step 302: The UAV control system reads the trajectory projection file generated in step 2 and obtains the coordinates of the initial trajectory point P 0 , transmitted to the drone, and the drone flies to the initial trajectory point P 0 , waiting for instructions;

[0035] Step 303: The UAV control system reads the simulation time corresponding to the initial trajectory point and uses it as the start time T 0 , when the time base reaches the start time T 0 When the time base reaches T k When the UAV is at P k point, the drone control system sends the next moment T k+1 Track point coordinates P k+1 To the drone, the drone will detect the time difference ΔT k and distance difference ΔP k Calculate flight speed v k , with speed v k To the new coordinate Pk+1 Flight, where:

[0036] ΔT k =T k+1 -T k ;

[0037] ΔP k =||P k+1 -P k ||,||·|| represents Euclidean distance;

[0038] υ k =ΔP k / ΔT k ;

[0039] Step 304: After reading the last set of (time, trajectory point coordinates) data pairs, the drone control system sends an end command to the drone.

[0040] Compared with the background technology, the present invention has the following advantages:

[0041] (1) The low-orbit simulation signal generated by the present invention and its spatial orientation are consistent with those of a real low-orbit satellite, and can be used for testing the entire communication terminal to make up for the shortcomings of indoor simulation testing.

[0042] The present invention adds a small amount of equipment such as unmanned aerial vehicles (UAVs) and communication simulation antennas on the basis of an indoor simulation test environment, and forwards the low-orbit satellite simulation signal generated by the indoor simulation test environment, which contains waveform characteristics and satellite-to-ground propagation characteristics and has been fully verified, via the unmanned aerial vehicle to realize the construction of a wireless simulation environment; at the same time, the unmanned aerial vehicle is synchronously controlled to run along the trajectory projection of the hemisphere to realize the spatial direction simulation of the low-orbit satellite signal; based on the present invention, the waveform characteristics, propagation characteristics, and signal direction of the generated low-orbit satellite simulation signal are consistent with those of a real low-orbit satellite, and the communication terminal tracks the unmanned aerial vehicle in an actual satellite-following manner to perform a closed-loop test, which makes up for the deficiency that the indoor simulation test cannot perform a whole-machine test of the communication terminal.

[0043] (2) The present invention can serve as an intermediate link between indoor simulation testing and outdoor real-satellite testing, supporting more efficient testing work.

[0044] The present invention uses the low-orbit satellite simulation signal generated by the indoor simulation test to forward and radiate through the drone to build a wireless test environment, which has the characteristics of flexible configuration of the simulation test scene and can test the entire communication terminal at the same time. The wireless test environment constructed based on the present invention can be applied after the indoor simulation test and before the outdoor real satellite test to fill the gap in the intermediate test link, which will effectively reduce the difficulty of the outdoor real satellite test, shorten the outdoor real satellite test time, and can carry out the test work more efficiently.

[0045] (3) The hemispherical test environment constructed by the present invention does not introduce time-varying errors, does not change the characteristics of the forwarded signal, and has low engineering implementation complexity.

[0046] The UAV moves along a spherical trajectory, and its movement direction is approximately perpendicular to the signal propagation direction (transmission toward the center of the sphere), so only a very small Doppler frequency deviation is introduced, which can be ignored compared with the large dynamic low-orbit signal; in addition, the UAV moves on the spherical surface, and its distance from the center of the sphere is always the radius R, so the signal delay and spatial attenuation introduced by it are fixed values ​​and can be deducted as zero; this means that in the hemispherical test environment constructed by the present invention, the low-orbit simulation signal of the indoor field simulation test environment is directly forwarded without complex compensation, so that the dynamic, delay, power and spatial direction simulation of the low-orbit satellite signal can be achieved, and the implementation complexity is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is the ENU station coordinate system established with the test point as the origin.

[0048] Figure 2 A hemispherical test environment established for the present invention.

[0049] Figure 3 For communication simulation, the antenna beam coverage area shifts with the position of the UAV.

[0050] Figure 4 This paper provides a method for calculating the radius of a sphere under the illumination of a communication simulation antenna.

[0051] Figure 5 The UAV with position offset is covered by the communication terminal antenna beam.

[0052] Figure 6 This is the calculation method for the radius of the sphere illuminated by the communication terminal antenna.

[0053] Figure 7 It is the projection of the satellite's trajectory on the hemisphere.

[0054] Figure 8 This is a simplified diagram of the low-orbit signal space simulation function. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below with reference to the accompanying drawings.

[0056] The invention belongs to the field of low-orbit satellite signal simulation, and mainly relates to a method for simulating the spatial orientation of low-orbit satellite signals.

[0057] Aiming at the need for low-orbit satellite waveform verification, the present invention provides a low-orbit satellite signal spatial direction simulation method, which can still support the whole-machine test of the satellite terminal when there are no sufficient orbit resources or no satellites.

[0058] To achieve the above object, the present invention discloses a method for simulating the spatial orientation of a low-orbit satellite signal, comprising the following steps:

[0059] Step 1: Use the test point as the coordinate origin and sphere center to construct a hemispherical test environment in the ENU station coordinate system.

[0060] The method for constructing the hemispherical test environment is as follows:

[0061] Step 101, select a test point, where drones are allowed to take off and land within a 1km range, with an elevation angle of more than 10° and no obvious obstruction, and calibrate the geodetic coordinates of the test point;

[0062] Step 102, using the test point as the coordinate origin, establish the ENU station coordinate system, such as Figure 1 As shown;

[0063] Step 103, with the test point as the sphere center and R as the radius, a three-dimensional sphere is constructed. The sphere is divided into two parts, upper and lower, by the EN plane of the ENU coordinate system. The upper hemisphere is a hemispherical test environment. Figure 2 As shown;

[0064] The radius R is determined according to the following conditions:

[0065] (1) The communication simulation antenna mounted on the drone is a narrow beam antenna, which is pointed at the test point in a staring manner. If the drone has position control errors, the illumination area of ​​the communication simulation antenna will shift with the drone. The radius of the sphere must be set to ensure that the test point can still be covered when the illumination area shifts with the drone position, such as Figure 3 shown.

[0066] Taking the transmission beam as an example, let the transmission beam width of the communication simulation antenna be D PS , the position control accuracy of the UAV is δ, and the radius of the virtual sphere is R, such as Figure 4 As shown, it is necessary to meet the following requirements:

[0067] δ≤R×tg(D PS / 2);

[0068] For low-orbit millimeter-wave signals, the satellite beam width is generally less than 5°, which can be approximated as:

[0069] δ≤R×tg(D PS / 2)≈R×(πD PS / 180°) / 2;

[0070] It can be deduced that:

[0071] R≥360°δ / (πD PS );

[0072] Similarly, for the receiving beam, the receiving beam width is recorded as D PR , it can be deduced that:

[0073] R≥360°δ / (πD PR );

[0074] (2) The communication terminal located at the test point has a narrow-beam antenna pointing to the theoretical position of the UAV. The actual position of the UAV deviates from the theoretical position. The radius of the sphere must be set to ensure that the UAV is still within the antenna beam of the communication terminal when there is a position deviation. Figure 5 shown.

[0075] Taking the receiving beam as an example, the receiving beam width of the communication terminal antenna is recorded as D TR ,like Figure 6 As shown, similarly, the approximate method can be used to deduce:

[0076] R≥360°δ / (πD TR );

[0077] Similarly, let the communication terminal antenna beam width be D TS , it can be deduced that:

[0078] R≥360°δ / (πD TS );

[0079] Remember R 0 =max{360°δ / (πD PS )、360°δ / (πD PR )、360°δ / (πD TR )、360°δ / (πD TS )}, which is equivalent to:

[0080] R 0 =360°δ / π / min{D PS , D PR , D TR , D TS};

[0081] According to engineering experience, a certain margin is left, which can be:

[0082] R≥(1.5~2)R 0 .

[0083] Step 2: Calculate the trajectory projection of the satellite in the hemispherical test environment based on parameters such as satellite coordinates, sphere center coordinates, and sphere radius.

[0084] The trajectory projection means that the line connecting the center of the sphere and the satellite intersects with the sphere to form an intersection point. The spherical trajectory line formed by the continuous movement of the satellite is as follows: Figure 7As shown. The steps for calculating the spherical trajectory projection coordinates are as follows:

[0085] Step 201, calculating the coordinates of the visible satellite S observed from the test point at a certain time in the ECEF rectangular coordinate system according to the satellite ephemeris;

[0086] Step 202: Convert the coordinates of satellite S in the ECEF rectangular coordinate system to the ENU station coordinate system, and calculate the elevation angle θ and azimuth angle of satellite S in the ENU station coordinate system.

[0087] Step 203, based on the sphere radius R and the satellite pitch angle θ and azimuth angle Calculate the coordinates of the satellite projection S' in the ENU station coordinate system;

[0088] Step 204, convert the ENU station coordinate system coordinates of the satellite projection S' into the ECEF rectangular coordinate system, and calculate its coordinates in the ECEF rectangular coordinate system;

[0089] Step 205, converting the coordinates of the satellite projection S' in the ECEF rectangular coordinate system to the geodetic coordinate system, and calculating its coordinates in the geodetic coordinate system;

[0090] Step 206 , as the satellite moves, steps 201 to 205 are repeated to obtain a series of geodetic coordinate system coordinate points of the satellite projection S′, ie, the trajectory projection of the satellite in the hemispherical test environment.

[0091] Step 3, establish a time reference, control the UAV to fly along the trajectory projection in the hemispherical test environment, and appear at the specified coordinate point at the specified time.

[0092] The UAV flight trajectory control method:

[0093] Step 301, establish a time reference, which has two modes: external timing and autonomous timing. External timing refers to timing by externally connecting to time information such as NTP and B code, and synchronizing with the external time system; autonomous timing refers to the UAV control system autonomously receiving Beidou signals for timing, and synchronizing with Beidou time.

[0094] Step 302: The UAV control system reads the trajectory file generated in step 2 and obtains the coordinates of the initial trajectory point P 0 , transmitted to the drone, and the drone flies to the initial trajectory point P 0 , waiting for instructions;

[0095] Step 303: The UAV control system reads the simulation time corresponding to the initial trajectory point and uses it as the start time T 0 , when the time base reaches the start time T 0 At this time, the UAV control system sends the next time T 1Track point coordinates P 1 to the drone, ..., repeat the above steps, when the time base reaches T k When the UAV is at P k point, the drone control system sends the next moment T k+1 Track point coordinates P k+1 To the drone, the drone will detect the time difference ΔT k and distance difference ΔP k Calculate flight speed v k , with speed v k To the new coordinate P k+1 Flight, where:

[0096] ΔT k =T k+1 -T k ;

[0097] ΔP k =||P k+1 -P k ||,||·|| represents Euclidean distance;

[0098] υ k =ΔP k / ΔT k ;

[0099] Step 304: After reading the last set of (time, trajectory point coordinates) data pairs, the drone control system sends an end command to the drone.

[0100] The embodiments provided by the present invention are as follows:

[0101] The present invention discloses a method for simulating the spatial orientation of a low-orbit satellite signal. The test environment constructed is as follows: Figure 8 As shown, it includes hemispherical test environment parameters, trajectory projection calculation module, UAV control system, tethered cable, UAV, communication simulation antenna and the constructed hemispherical test environment; the indoor field simulation test environment in the figure is an existing system, which outputs low-orbit satellite simulation signals; the communication terminal is the device to be tested, which is placed at the center of the sphere during the test.

[0102] The hemispherical test environment parameters include the test point coordinates, radius, etc., which are determined by step 1; the trajectory projection calculation module is designed and implemented according to step 2, generates drone trajectory data and stores it as a file; the drone control system controls the drone flight trajectory according to step 3; the tethered cable is used to connect the drone control system and the drone, and transmits flight trajectory, low-orbit satellite simulation signals, power supply and other signals; the drone is a multi-rotor drone with a 15Kg load capacity and a 300m ceiling capacity, and a differential positioning accuracy of less than 0.5m; the communication simulation antenna is a transceiver antenna, simulating one receiving beam and one transmitting beam of a low-orbit satellite, the beam width is consistent with the real satellite beam, and the staring mode is adopted when working, always pointing to the center test point; the hemispherical test environment is constructed by step 1.

[0103] The working principle is as follows: according to step 1 and step 2, unmanned aerial vehicle trajectory data is generated in advance; according to step 3, a system time reference is established to realize time synchronization among the unmanned aerial vehicle control system, the indoor test environment, and the communication terminal; when the start time is reached, the present invention performs unmanned aerial vehicle flight trajectory control according to step 3 to ensure that the unmanned aerial vehicle moves according to the satellite trajectory projection and appears at the designated position at the designated time; after the start time is reached, the indoor simulated test environment starts the simulation signal generation according to the ephemeris parameters and the test point coordinates, generates the low-orbit satellite simulation signal of the antenna aperture of the communication terminal at the designated time, and radiates to the communication terminal after forwarding through the communication simulation antenna; the communication terminal generates the antenna tracking data and signal tracking parameters in advance according to the ephemeris parameters and the test point coordinates, and when the start time is reached, the system dispatches and forwards these parameters to control the antenna to point to the satellite direction, that is, the unmanned aerial vehicle direction, and simultaneously uses the signal tracking parameters to perform signal tracking and business communication.

[0104] The radius of the hemispherical test environment of the present invention is calculated as follows:

[0105] According to: R 0 =360°δ / π / min{D PS , D PR , D TR , D TS};

[0106] Take δ = 0.5m, D PS =3.5°, D PR =2.5°, D TR =1.2°, D TS =0.8°,

[0107] R 0 =72m, according to engineering experience, a certain margin is left, there are:

[0108] R≥2R 0=144m, so R=150m can be taken.

[0109] The signal transmission delay introduced by the hemispherical test environment of the present invention is:

[0110] Signal transmission delay is divided into satellite-to-ground downlink transmission delay τ 0PT The uplink transmission delay from the earth to the satellite is fixed at R = 150m, and the speed of light is c = 3e8m / s, then: τ 0PT =τ 0TP =R / c=500ns; deducted as the zero value of system delay in the indoor simulation test environment.

[0111] The spatial attenuation introduced by the hemispherical test environment of the present invention is:

[0112] Space attenuation: Satellite-to-ground space attenuation L 0PT and the uplink space attenuation L 0TP , satellite-to-ground downlink frequency f PT =20GHz, satellite-to-ground uplink frequency f TP =30GHz, then: L 0PT =32.45+20×lg(f PT ×R)≈102dB, L 0TP =32.45+20×lg(f TP ×R)≈105.5dB; in the indoor simulated test environment, the system power is deducted from zero value.

[0113] The contents not described in detail in this specification belong to the common knowledge of those skilled in the art.

Claims

1. A method for simulating the spatial direction of low-orbit satellite signals, characterized in that: The following steps are involved: Step 1: Using the test point as the coordinate origin and sphere center, a hemispherical test environment is constructed in the ENU station coordinate system; Step 2, calculating the trajectory projection of the satellite in the hemispherical test environment according to the satellite coordinates, the sphere center coordinates and the sphere radius; Step 3, establish a time reference, control the UAV to fly along the trajectory projection in the hemispherical test environment, and appear at the specified coordinate point at the specified time.

2. A method for simulating the spatial direction of a low-orbit satellite signal according to claim 1, characterized in that: The specific process of step 1 is: Step 101, select a test point, the test point and its surrounding areas allow drones to take off and land, the test airspace has no obvious obstruction, and calibrate the geodetic coordinates of the test point; Step 102, establishing the ENU station coordinate system with the test point as the coordinate origin; Step 103, constructing a three-dimensional sphere with the test point as the sphere center and R as the radius, wherein the sphere is divided into upper and lower parts by the EN plane of the ENU coordinate system, and the upper hemisphere is a hemispherical test environment; The calculation method of the sphere radius R is as follows: The beam width of the communication simulation antenna is D PS , the receiving beam width is D PR , the receiving beam width of the communication terminal antenna is D TR , the beam width is D TS , the UAV position control accuracy is δ, it can be concluded that: R≥360°δ / (πD PS ); R≥360°δ / (πD PR ); R≥360°δ / (πD TR ); R≥360°δ / (πD TS ); Taking the maximum value as R0, we can get: R0=360°δ / π / min{D PS 、D PR 、D TR 、D TS }; Take R≥(1.5~2)R0.

3. A method for simulating the spatial direction of a low-orbit satellite signal according to claim 1, characterized in that: The specific process of step 2 is: Step 201, calculating the coordinates of the visible satellite S observed from the test point at a certain time in the ECEF rectangular coordinate system according to the satellite ephemeris; Step 202, converting the coordinates of the satellite S in the ECEF rectangular coordinate system to the ENU station coordinate system, and calculating the elevation angle θ and azimuth angle φ of the satellite S in the ENU station coordinate system; Step 203, calculating the coordinates of the satellite projection S' in the ENU station coordinate system according to the sphere radius R and the satellite pitch angle θ and azimuth angle φ; Step 204, converting the coordinates of the satellite projection S' in the ENU station coordinate system to the ECEF rectangular coordinate system to obtain the coordinates of the satellite projection S' in the ECEF rectangular coordinate system; Step 205, converting the coordinates of the satellite projection S' in the ECEF rectangular coordinate system to the geodetic coordinate system to obtain the coordinates of the satellite projection S' in the geodetic coordinate system; Step 206 , as the satellite moves, steps 201 to 205 are repeated to obtain a series of coordinate points of the satellite projection S′ in the geodetic coordinate system, ie, the trajectory projection of the satellite in the hemispherical test environment.

4. The method for simulating the spatial direction of a low-orbit satellite signal according to claim 1, characterized in that: The specific process of step 3 is as follows: Step 301, establish a time reference, which has two modes: external timing and autonomous timing. External timing refers to externally connecting NTP and B-code time information for timing, which is synchronized with the external time system; autonomous timing refers to the UAV control system autonomously receiving Beidou signals for timing, which is synchronized with Beidou time. Step 302, the drone control system reads the trajectory projection file generated in step 2, obtains the coordinates of the initial trajectory point P0, transmits it to the drone, and the drone flies to the initial trajectory point P0 and waits for instructions; Step 303: The UAV control system reads the simulation time corresponding to the initial trajectory point and uses it as the start time T0. When the time base reaches the start time T0, the UAV control system sends the coordinates of the trajectory point at the next moment to the UAV in sequence. When the time base reaches T0, the UAV control system sends the coordinates of the trajectory point at the next moment to the UAV in sequence. k When the UAV is at P k point, the drone control system sends the next moment T k+1 Track point coordinates P k+1 To the drone, the drone will detect the time difference ΔT k and distance difference ΔP k Calculate flight speed v k , with speed v k To the new coordinate P k+1 Flight, where: ΔT k =T k+1 -T k ; ΔP k =||P k+1 -P k ||,||·|| represents Euclidean distance; u k =ΔP k / ΔT k ; Step 304: After reading the last set of (time, trajectory point coordinates) data pairs, the drone control system sends an end command to the drone.

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