A method for tracking low-orbit terminals using a small-sized dual-throw antenna

Abstract

This invention provides a method for tracking a small-sized dual-throw antenna low-Earth orbit terminal, comprising: calculating the target's geographic azimuth and elevation angles in a geographic coordinate system; measuring the carrier's heading, elevation, and roll angles, as well as the antenna's current azimuth, elevation, and third-axis angles; calculating the target's carrier azimuth and elevation angles in a carrier coordinate system; based on the obtained target geographic azimuth and elevation angles, carrier heading, elevation, and roll angles, and antenna's current azimuth angle, employing an azimuth-elevation control strategy to solve for the antenna control azimuth angle, and using the antenna's current azimuth axis angle as a coordinate rotation constraint to solve for the antenna control elevation angle and antenna control third-axis angle, and controlling the rotation of each axis of the antenna to the target angle, so that the terminal antenna beam points towards the target. This invention eliminates the need to consider antenna elevation threshold settings, tracking mode switching, and recalculation issues, resulting in a simple tracking algorithm.

Description

Technical Field

[0001] This invention belongs to the field of low-Earth orbit satellite communication technology, specifically relating to a tracking method for a low-Earth orbit terminal using a small-sized dual-throw antenna. Background Technology

[0002] With the rapid development of low-Earth orbit (LEO) satellite technology and commercial operation services, communication terminals for LEO satellites have seen rapid development in recent years. Currently, LEO satellite terminal products can be broadly categorized into two types based on their technical architecture: one type is based on phased array technology, which offers advantages such as small size and fast beam switching. However, current commercially available products suffer from performance deficiencies, high costs, and significant power consumption and noise. The other type employs a parabolic antenna for relay tracking. Its disadvantage is that a single parabolic antenna has a slower satellite-switching speed compared to a phased array antenna, requiring two antennas for relay tracking. However, this type of product offers advantages such as stable performance, low cost, and low power consumption and noise, making it widely used in specific scenarios.

[0003] For low-Earth orbit (LEO) satellites requiring overhead tracking, current parabolic antenna terminals are all three-axis antennas. Traditional antenna tracking strategies typically fall into two categories: one involves tracking at low elevation angles using an AE (Advanced Elevation) mount and at high elevation angles using an XY (Extremely High Elevation) mount. This method, with its azimuth-velocity constant drive at high elevation angles, may experience signal loss during overhead tracking. The other strategy involves relay tracking along the AE and EC axes, which increases tracking error when switching tracking axes. In recent years, the development of LEO satellite terminal antennas has often resulted in a very small range of motion for the third axis to reduce product size and achieve integrated design. This makes previous tracking strategies less applicable, and a suitable tracking method has yet to emerge. Generally, existing methods are modified, requiring recalculation of satellite beam elevation angle, third-axis range of motion, or antenna azimuth axis speed after mode classification. This results in at least two or more sets of calculation formulas for controlling each antenna axis, leading to numerous constraints and complex tracking algorithms. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of poor tracking performance caused by the complex tracking algorithm of the low-orbit terminal with small-sized dual-throw antenna in the prior art, and to provide a new tracking algorithm and tracking strategy that can ensure that the beam of the low-orbit terminal antenna is stably pointed to the target satellite.

[0005] To achieve the above objectives, the technical solution provided by this invention is:

[0006] A method for tracking low-orbit terminals using a small-sized dual-throw antenna is provided, comprising the following steps:

[0007] Step 1: Based on the orbital information or real-time location information of the low-orbit satellite target, calculate the target's geographic azimuth angle A and geographic elevation angle E in the geographic coordinate system.

[0008] Step 2: Utilize an inertial navigation system mounted on the antenna to measure the carrier's heading angle H, pitch angle P, and roll angle R during its motion. Also, use angle sensors mounted on the antenna's azimuth, pitch, and third axes to measure the antenna's current azimuth angle Az. c Antenna current elevation angle El c and the current third axis angle Cr of the antenna c ;

[0009] Step 3: Based on the calculated target geographic azimuth A and target geographic elevation E, obtain the target carrier azimuth A in the carrier coordinate system. j and target vehicle pitch angle E j ;

[0010] Step 4: Based on the obtained target geographical azimuth A and target geographical elevation E, vehicle heading angle H, vehicle elevation angle P and vehicle roll angle R, and antenna current azimuth Az c An azimuth-elevation control strategy is employed to solve for the antenna control azimuth angle Az. i And the current angle of the antenna azimuth axis is used as the coordinate rotation constraint condition A. j =Az c Solve for the antenna control elevation angle El i and antenna control of the third axis angle Cr i It controls the azimuth axis, elevation axis and third axis of the antenna to rotate to the solved angle, so that the beam of the terminal antenna points to the target, thereby completing antenna pointing tracking.

[0011] Furthermore, in step 4, the antenna control azimuth angle Az is solved using the following formula. i Antenna control elevation angle El i and antenna control of the third axis angle Cr i :

[0012]

[0013] In the formula,

[0014] Furthermore, in step 4, when the difference between the actual angle of the antenna azimuth axis and the target angle is less than a predetermined angle tolerance threshold, the antenna azimuth axis can track the target angle, and the calculated result of the antenna third axis command angle is zero; when the difference between the actual angle of the antenna azimuth axis and the target angle is greater than or equal to the predetermined angle tolerance threshold, the antenna azimuth axis cannot track the target angle, and the calculated result of the antenna third axis command angle will automatically compensate for the beam deviation angle caused by the inability to track the azimuth.

[0015] Furthermore, the predetermined angle tolerance threshold is within the range of 0.2°-0.5°.

[0016] Furthermore, in step 4, if the antenna's movement path passes through an azimuth dead zone, the azimuth dead zone ranges from AzL to AzR, then the antenna's azimuth axis is rotated in the opposite direction by an angle Az. i ', Reverse angle Az i The calculation is as follows:

[0017] (1) Calculate the required antenna azimuth rotation angle: AzErr=Az i -Az c ;

[0018] (2) Perform the following processing on AzErr:

[0019]

[0020] (3) Perform the remainder operation and introduce the variable P: P = (Az) i +AzErr')%360;

[0021] And perform the following operation on P:

[0022] (4) Determine the reverse rotation angle of the antenna azimuth axis:

[0023]

[0024] Furthermore, the tracking method also includes: Step 5, calculating the actual pointing of the antenna beam in the geographic coordinate system, i.e., the geographic azimuth angle A of the antenna beam. c and antenna beam geographic elevation angle E c This is to verify whether the antenna beam is pointing towards the target.

[0025]

[0026] In the formula,

[0027]

[0028] Furthermore, step 5 also includes setting the geographical azimuth angle A of the antenna beam. c Handling data jumps:

[0029] When the azimuth A of the low-orbit star is in the first quadrant:

[0030]

[0031] When the azimuth A of a low-orbit star is in the second or third quadrant:

[0032]

[0033] When the azimuth A of a low-orbit star is in the fourth quadrant:

[0034]

[0035] In the formula, M represents the angular fluctuation range.

[0036] The advantages of this invention are:

[0037] 1. The tracking method for low-Earth orbit (LEO) satellite terminal antennas proposed in this invention can solve the current problem of satellite tracking for a class of small-sized LEO terminal antennas. According to the tracking strategy proposed in this invention, when the antenna is tracking a target, if the antenna elevation angle is low, the antenna azimuth axis can track the target angle on the azimuth axis, and the calculated result of the antenna third axis command angle is zero, which is consistent with the tracking effect of traditional three-axis antennas. When the antenna elevation angle increases to the azimuth tracking blind zone, the antenna azimuth axis cannot track the target angle on the azimuth axis, and the calculated result of the antenna third axis command angle will automatically compensate for the beam deviation angle caused by the inability to track the azimuth. Therefore, there is no need to consider issues such as setting the antenna elevation angle threshold, switching the tracking mode, and recalculating. The tracking algorithm is simple and the tracking effect is improved.

[0038] 2. When the antenna passes through the azimuth dead zone on the movement path during the tracking process, the antenna azimuth axis can be reversed to achieve the required antenna azimuth angle. Therefore, it can effectively solve the problem of limited installation position of terminal antennas with azimuth dead zones during operation. Attached Figure Description

[0039] The above and / or other features and advantages of the present invention will become more readily understood from the following description with reference to the accompanying drawings, which are not drawn to scale and some features are enlarged or reduced to show details of specific parts.

[0040] Figure 1 This is a flowchart of the low-orbit terminal tracking method with a small-sized dual-throw antenna according to the present invention;

[0041] Figure 2 It refers to the antenna beam direction of a low-orbit satellite in a geographic coordinate system;

[0042] Figure 3 It refers to the antenna beam pointing of a low-orbit satellite in the carrier coordinate system;

[0043] Figure 4 It refers to the antenna beam pointing of a low-orbit satellite in the antenna coordinate system. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and exemplary embodiments thereof. It should be noted that the following detailed description of the present invention is for illustrative purposes only and is not intended to limit the scope of the invention.

[0045] This invention provides a tracking method for a small-sized dual-throw antenna low-Earth orbit terminal, which solves the current problem of satellite tracking for a type of small-sized low-Earth orbit terminal. The algorithm only requires a set of mathematical formulas and does not require recalculation after mode classification of satellite beam elevation angle, third axis motion range or antenna azimuth axis motion range.

[0046] When a low-Earth orbit satellite passes overhead, if the attitude of the carrier supporting the antenna changes while its beam is pointing towards the satellite, it will directly affect the antenna's pointing direction, causing the beam to deviate from the satellite and resulting in signal lock-on failure. To ensure that antennas fixed on carriers such as vehicles, ships, and aircraft always point towards the satellite during carrier movement, measures need to be taken to stabilize and control the antenna's pointing direction.

[0047] To achieve this control, the usual approach is to establish and derive a mathematical model of antenna pointing, and use the results as instructions for antenna control. This controls the antenna axis to rotate by a corresponding angle and forms a closed-loop control system with the angle measurement unit, ensuring that the antenna always points to the satellite even when the carrier's attitude changes, thus achieving the goal of real-time antenna tracking.

[0048] Reference Figure 1 The low-orbit terminal tracking method with a small-sized dual-throw antenna, as an exemplary embodiment of the present invention, includes the following steps:

[0049] Step S1: Calculate the target's geographic azimuth A and geographic elevation E in the geographic coordinate system based on the orbital information or real-time location information of the low-orbit satellite target.

[0050] Step S2: Measure the carrier's heading angle H, pitch angle P, and roll angle R during its motion using an inertial navigation system mounted on the antenna. Also, measure the antenna's current azimuth angle Az using angle sensors mounted on the antenna's azimuth, pitch, and third axes. c Antenna current elevation angle El c and the current third axis angle Cr of the antenna c ;

[0051] Step S3: Based on the calculated target geographic azimuth A and target geographic elevation E, obtain the target carrier azimuth A in the carrier coordinate system.j and target vehicle pitch angle E j ;

[0052] Step S4: Based on the obtained target geographical azimuth A and target geographical elevation angle E, vehicle heading angle H, vehicle elevation angle P and vehicle roll angle R, and antenna current azimuth angle Az c An azimuth-elevation control strategy is employed to solve for the antenna control azimuth angle Az. i And the current angle of the antenna azimuth axis is used as the coordinate rotation constraint condition A. j =Az c Solve for the antenna control elevation angle El i and antenna control of the third axis angle Cr i It controls the azimuth axis, elevation axis and third axis of the antenna to rotate to the solved angle, so that the beam of the terminal antenna points to the target, thereby completing antenna pointing tracking.

[0053] The orbit prediction of low-Earth orbit satellites can be analyzed using the SGP4 (Simplified General Perturbations Version 4) algorithm. However, the prediction result is an angle in the geographic coordinate system, which cannot be directly used for antenna angle control. It needs to be transformed to an angle in the carrier coordinate system, and then to an angle in the antenna coordinate system to obtain the final command angle required for antenna control. In this invention, the coordinate rotation process is: geographic coordinate system -> carrier coordinate system -> antenna coordinate system.

[0054] Figure 2 The image shows the antenna orientation of a low-Earth orbit satellite in a geographic coordinate system. The geographic coordinate system is defined as O. d X d Y d Z d ;O d X d The axis points due east; O d Y d The axis points due north; O d Z d The axis points to the zenith, O d Z d Shaft and O d X d Shaft and O d Y d The axes form a right-handed rectangular coordinate system.

[0055] In the diagram, S represents the position of the target satellite; O d The line S represents the antenna beam direction in the geographic coordinate system; A and E are the azimuth and elevation angles of the low-orbit satellite in the geographic coordinate system, respectively, which are specifically obtained from orbit prediction by the host computer.

[0056] Figure 3 This refers to the antenna pointing of the low-Earth orbit satellite in the carrier coordinate system. The carrier coordinate system is defined as O. j X j Y j Z j ;O j X j The axis points to the right side of the carrier, O j X j The rotation of the axis forms the pitch angle of the carrier; O j Y j The axis points in the direction of the carrier's movement, O j Y j The shaft rotation forms the carrier roll angle; O j Z j The axis points upwards on the carrier, O j Z j The rotation of the axis forms the carrier's heading angle; O j Z j Shaft and O j X j Shaft and O j Y j The axes form a right-handed rectangular coordinate system.

[0057] In the diagram, S represents the position of the target satellite; O j The line S represents the antenna beam direction in the carrier coordinate system; A j and E j These are the azimuth and elevation angles of the satellite in the carrier coordinate system, respectively, which are obtained from the satellite's angles in the geographic coordinate system through coordinate rotation.

[0058] The specific process of the rotation relationship from the geographic coordinate system to the carrier coordinate system is as follows: first, rotate around O... d Z d Rotate the axis clockwise by an angle H, then rotate it around the rotated O. d X' d Rotate the axis by an angle P in a right-hand rule, and finally rotate it by the resulting O. d Y d Rotate by angle R according to the right-hand rule.

[0059] Figure 4 This refers to the antenna pointing of a low-Earth orbit satellite in the antenna coordinate system. The antenna coordinate system is defined as O. i X i Y i Z i O i Z i The axis is the third axis of the antenna, O i Z i The angle formed by rotating the axis to create the third axis of the antenna; O i X i The axis coincides with the antenna's elevation axis, Oi X i The third axis rotates to form the antenna's elevation angle. When the elevation angle is parallel to the antenna base, the third axis coincides with the antenna's azimuth axis. i Y i The axis is the direction of the electrical axis, O i Z i Shaft and O i X i Shaft and O i Y i The axes form a right-handed rectangular coordinate system.

[0060] In the diagram, S represents the position of the target satellite; O i The S-line represents the beam direction in the antenna coordinate system.

[0061] The specific process of the rotation relationship from the carrier coordinate system to the antenna coordinate system is as follows: first, rotate around O... j Z j Rotate the axis clockwise by an angle Az i Then rotate around O j X' j The axis rotates at an angle El according to the right-hand rule. i Finally, rotate the O j Y j Rotate angle Cr according to the right-hand rule i .

[0062] For antenna control systems, the antenna alignment process mainly involves precise control of the antenna's axes, namely the azimuth axis, elevation axis, and third axis.

[0063] This invention proposes the following tracking strategy for novel low-orbit terminal satellite antennas with a small range of motion on the third axis: the control command angle of the antenna azimuth axis is solved using an azimuth-elevation type mount method, and the actual angle of the azimuth axis is used as a coordinate rotation constraint condition for solving the command angles of the elevation axis and the third axis.

[0064] The advantage of obtaining the antenna control angle in this way is:

[0065] When the satellite elevation angle is low, since the antenna speed can meet the tracking requirements, the antenna azimuth axis can track the target angle on the upper axis. The antenna only uses the azimuth and elevation axes for tracking, and the third axis does not move.

[0066] As the satellite elevation angle gradually increases until the actual azimuth speed does not meet the tracking requirements, the antenna azimuth axis cannot track the azimuth target angle, and the antenna enters the tracking blind zone. At this time, the third axis will automatically enter the tracking mode to compensate for the pointing deviation caused by the azimuth not being tracked properly. At the same time, the azimuth will automatically move towards the target position at the maximum antenna speed.

[0067] This strategy eliminates the need to predict the trajectory to consider the timing of the introduction and retraction of the third axis, and also eliminates the need to establish different mathematical models for factors such as antenna elevation angle, third axis range of motion, or azimuth speed.

[0068] According to the present invention, in step S4, the antenna control azimuth angle Az is solved using the following formula. i Antenna control elevation angle El i and antenna control of the third axis angle Cr i :

[0069]

[0070]

[0071] In the formula,

[0072] The antenna axes are controlled using formulas (1) to (3) respectively, therefore:

[0073] When the satellite orbit elevation angle is low, the antenna has not yet reached the azimuth blind zone because the antenna beam elevation angle is low. The third axis motion result calculated by formula (3) is near zero, which is equivalent to using the azimuth and elevation axes for tracking at low elevation angles.

[0074] As the satellite orbit elevation angle gradually increases, the azimuth axis of the antenna gradually increases. Assuming the beam elevation angle points to the zenith, theoretically the azimuth movement speed should reach infinity. Therefore, there is a blind zone in the azimuth when it approaches the zenith. When the elevation angle gradually increases to the blind zone, the motion result of the third axis calculated by formula (3) gradually increases, which is equivalent to using the motion of the third axis to compensate for the part of the azimuth movement that is restricted. Since the third axis is usually set orthogonal to the elevation axis, the motion speed of the third axis is actually very small in the range of the azimuth blind zone, which can achieve a good compensation effect.

[0075] As the satellite's orbital elevation angle gradually decreases from its highest point, the motion result of the third axis calculated using formula (3) gradually decreases until it becomes zero. At low elevation angles, the azimuth and elevation axes continue to be used for tracking.

[0076] Throughout the tracking process, formulas (1) to (3) are consistently used. As the elevation angle gradually increases, there is no need to classify or set restrictions on the satellite beam elevation angle, the range of motion of the third axis, or the range of motion of the antenna azimuth axis due to the timing of the introduction of third-axis tracking. At the same time, as the elevation angle gradually decreases, there is no need to consider when the third axis returns to zero and the speed of zeroing, and to perform mode classification again. The entire process is completely unified under three formulas, the tracking curve is smooth, and the tracking error is stable without jumps when the third axis is introduced and returns to zero.

[0077] In some embodiments, in step S4, when the difference between the actual angle of the antenna azimuth axis and the target angle is less than a predetermined angle tolerance threshold, it indicates that the antenna azimuth axis can track the target angle, and the calculated result of the antenna third axis command angle is zero; when the difference between the actual angle of the antenna azimuth axis and the target angle is greater than or equal to the predetermined angle tolerance threshold, it indicates that the antenna azimuth axis cannot track the target angle, and the calculated result of the antenna third axis command angle will automatically compensate for the beam deviation angle caused by the inability to track the azimuth. Preferably, the predetermined angle tolerance threshold is in the range of 0.2°-0.5°, more preferably 0.2°.

[0078] Furthermore, this invention takes into account that some satellite terminals targeting low-Earth orbit satellites, due to cost and size considerations, do not use slip rings and winding devices in the azimuth direction, resulting in a small dead zone in the azimuth range. Therefore, the orbital direction of the target satellite needs to be carefully considered during antenna installation to avoid this dead zone, which causes inconvenience in actual use. Therefore, in step S4, if the antenna movement path passes through the azimuth dead zone, the azimuth dead zone range is AzL to AzR, where AzL is the dead zone angle on the left side of the antenna structure and AzR is the dead zone angle on the right side of the antenna structure, then the antenna azimuth axis is controlled to rotate in the opposite direction by an angle Az. i ', Reverse angle Az i The calculation is as follows:

[0079] (1) Calculate the required antenna azimuth rotation angle: AzErr=Az i -Az c ;

[0080] (2) Perform the following processing on AzErr:

[0081]

[0082] (3) Perform the remainder operation and introduce the variable P: P = (Az) i +AzErr')%360;

[0083] And perform the following operation on P:

[0084] (4) Determine the reverse rotation angle of the antenna azimuth axis:

[0085]

[0086] Therefore, when the satellite orbit elevation angle gradually increases, if the antenna needs to pass through the azimuth dead zone on its movement path, the antenna azimuth is first reversed. During this process, the third axis begins to intervene to compensate for the tracking angle deviation caused by the azimuth reversal. This effectively solves the problem of limited installation position for terminal antennas with azimuth dead zones during operation.

[0087] In order to verify whether the antenna beam is pointing to the target angle, and to formulate various parameters and tracking strategies during the debugging process of the terminal antenna, the spatial pointing of the beam is required as a reference. The antenna tracking method of the present invention may further include: step S5, calculating the actual pointing of the antenna beam in the geographic coordinate system, that is, the geographic azimuth angle A of the antenna beam. c and antenna beam geographic elevation angle E c This is to verify whether the antenna beam is pointing towards the target.

[0088]

[0089] In the formula,

[0090]

[0091] Due to limitations in sensor accuracy, there is a fluctuation range in the heading, roll, and pitch angles. The A calculated using the above formula... c As a result, data jumps may occur in adjacent quadrants, leading to inaccurate spatial pointing data. Therefore, step S5 may further include setting the geographical azimuth angle A of the antenna beam. c Handling data jumps:

[0092] When the azimuth A of the low-orbit star is in the first quadrant:

[0093]

[0094] When the azimuth A of a low-orbit star is in the second or third quadrant:

[0095]

[0096] When the azimuth A of a low-orbit star is in the fourth quadrant:

[0097]

[0098] In the formula, M represents the angular fluctuation range.

[0099] Those skilled in the art should understand that, since it involves relay tracking by two antennas, the control of antenna B is completely consistent with the control of antenna A. However, due to the delay in data communication between the two antennas, antenna B needs to predict the data for two communication cycles in advance, using a second-order extrapolation method. Throughout the debugging process, spatial pointing is used as a reference, combined with the level fluctuation range, as the basis for debugging the dynamic parameters related to tracking error.

[0100] Therefore, as described above, according to the tracking strategy proposed in this invention, when the antenna is tracking a target, if the antenna elevation angle is low, the antenna azimuth axis can track the azimuth target angle, and the calculated result of the antenna third axis command angle is zero, which is consistent with the tracking effect of a traditional three-axis antenna. When the antenna elevation angle increases to the azimuth tracking blind zone, the antenna azimuth axis cannot track the azimuth target angle, and the calculated result of the antenna third axis command angle will automatically compensate for the beam deviation angle caused by the inability to track the azimuth. Therefore, the tracking method of this invention does not need to consider issues such as antenna elevation threshold setting, tracking mode switching, and recalculation. The tracking algorithm is simple and the tracking effect is improved.

[0101] Finally, it should be noted that the features mentioned and / or shown in the above description of exemplary embodiments of the present invention can be combined in the same or similar manner with one or more other embodiments, combined with features in other embodiments, or substituted for corresponding features in other embodiments. These combined or substituted technical solutions should also be considered to be included within the scope of protection of the present invention.

Claims

1. A method for tracking a low-orbit terminal using a small-sized dual-throw antenna, characterized in that, Includes the following steps: Step 1: Calculate the target's geographic azimuth in the geographic coordinate system based on the low-Earth orbit satellite target's orbital information or real-time location information. and target geographic elevation angle ; Step 2: Measure the heading angle of the carrier during its motion using an inertial navigation system mounted on the antenna. Carrier pitch angle and carrier roll angle The antenna's current azimuth angle is measured using angle sensors mounted on the antenna's azimuth, elevation, and third axes. Antenna current elevation angle and the current third axis angle of the antenna ; Step 3, based on the calculated target geographic azimuth. and target geographic elevation angle Obtain the target carrier azimuth angle in the carrier coordinate system. and target vehicle pitch angle ; Step 4, based on the obtained target geographical azimuth. and target geographic elevation angle Carrier heading angle Carrier pitch angle and carrier roll angle and the current azimuth angle of the antenna An azimuth-elevation control strategy is employed to solve for the antenna control azimuth angle. The current angle of the antenna azimuth axis is used as the coordinate rotation constraint. Solve for the antenna control elevation angle and antenna control of the third axis angle The system controls the azimuth, elevation, and third axes of the antenna to rotate to the calculated angles, so that the beam of the terminal antenna points to the target, thereby completing antenna pointing tracking. Specifically, when the difference between the actual angle of the antenna azimuth axis and the target angle is less than a predetermined angle tolerance threshold, the antenna azimuth axis can track the target angle, and the calculated result of the command angle of the antenna third axis is zero. When the difference between the actual angle of the antenna azimuth axis and the target angle is greater than or equal to the predetermined angle tolerance threshold, the antenna azimuth axis cannot track the target angle, and the calculated result of the command angle of the antenna third axis will automatically compensate for the beam deviation angle caused by the inability to track the azimuth.

2. The low-orbit terminal tracking method with a small-size dual-throw antenna according to claim 1, characterized in that, In step 4, the antenna control azimuth angle is calculated using the following formula. Antenna control elevation angle and antenna control of the third axis angle : In the formula, .

3. The low-orbit terminal tracking method with a small-size dual-throw antenna according to claim 1 or 2, characterized in that, The predetermined angle tolerance threshold is in the range of 0.2°-0.5°.

4. The low-orbit terminal tracking method with a small-size dual-projectile antenna according to claim 1 or 2, characterized in that, In step 4, if the antenna's path passes through the azimuth dead zone, the range of the azimuth dead zone is... ,but Control the reverse rotation angle of the antenna azimuth axis Reverse angle The calculation is as follows: (1) Calculate the required antenna azimuth rotation angle: ; (2) To Perform the following processing: (3) Perform the remainder operation and introduce variables. : ; And on Perform the following calculations: ; (4) Determine the reverse rotation angle of the antenna azimuth axis: 。 5. The low-orbit terminal tracking method with a small-size dual-throw antenna according to claim 1 or 2, characterized in that... It also includes: Step 5, calculating the actual direction of the antenna beam in the geographic coordinate system, i.e., the geographic azimuth angle of the antenna beam. and antenna beam geographic elevation angle This is to verify whether the antenna beam is pointing towards the target. In the formula, 。 6. The low-orbit terminal tracking method with a small-size dual-throw antenna according to claim 5, characterized in that, Step 5 also includes setting the geographic azimuth of the antenna beam. Handling data jumps: When the azimuth angle of a low-orbit star In the first quadrant: When the azimuth angle of a low-orbit star In the second or third quadrant: When the azimuth angle of a low-orbit star In the fourth quadrant: In the formula, M represents the angular fluctuation range.

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