Small-size double-parabolic antenna low-orbit terminal tracking method

Abstract

The invention provides a small-size double-parabolic antenna low-orbit terminal tracking method. The method comprises the following steps: calculating a target geographic azimuth angle and a pitch angle of a target in a geographic coordinate system; measuring a course angle, a pitch angle and a roll angle of a carrier and a current azimuth angle, a pitch angle and a third axis angle of an antenna; calculating a target carrier azimuth angle and a pitch angle of the target under the carrier coordinate system; according to the obtained target geographic azimuth angle and pitch angle, the carrier course angle, pitch angle and roll angle and the current azimuth angle of the antenna, an azimuth pitch type control strategy is adopted to solve the control azimuth angle of the antenna, and the current angle of the azimuth axis of the antenna is adopted as a coordinate rotation constraint condition to solve the control pitch angle of the antenna and the angle of the third control axis of the antenna; and each axis of the antenna is controlled to rotate to a target angle, so that the beam of the terminal antenna points to the target. The problems of antenna elevation angle threshold setting, tracking mode switching, recalculation and the like do not need to be considered, and the tracking algorithm is simple.

Description

Technical Field

[0001] The invention belongs to the technical field of low-orbit satellite communications, and in particular relates to a small-size dual-throw antenna low-orbit terminal tracking method. Background Art

[0002] With the vigorous development of low-orbit satellite technology and commercial operation services, communication terminals for low-orbit satellites have developed rapidly in recent years. The low-orbit satellite terminal products currently developed can be basically divided into two categories from the technical system: one is based on the phased array technology system, which has the advantages of small product size and fast beam switching. However, the performance of the current products is lacking, the cost is high, and the power consumption and noise are large; the other is a technical system that uses parabolic antennas for relay tracking. The disadvantage is that the single parabolic antenna has a slower satellite switching speed than the phased array antenna, so two antennas are required for relay tracking. However, the advantages of this type of product are stable product performance, low cost, low power consumption and noise, and therefore it is widely used in specific scenarios.

[0003] In the case that low-orbit satellites need to pass overhead, the parabolic antenna terminals currently used are all three-axis antennas. The tracking strategies of traditional antennas are usually divided into two types: one is to track when the AE mount antenna is at low elevation angles, and to track when the XY mount antenna is at high elevation angles. When this method is used for tracking at high elevation angles, the azimuth is driven at a constant speed, and there may be signal loss when tracking overhead; the other tracking strategy is relay tracking of the AE axis and the EC axis. This method will increase the tracking error when the tracking axis is switched. In recent years, in the development of low-orbit satellite terminal antennas, in order to reduce the product volume and achieve integrated design, the motion range of the third axis is often designed to be very small, resulting in the previous tracking strategies not being applicable in the tracking process. At present, there is no more suitable tracking method. Generally, corrections are made on the basis of the previous tracking method, and the elevation angle of the satellite beam, the motion range of the third axis, or the motion speed of the antenna azimuth axis are classified and recalculated, resulting in at least two or more sets of calculation formulas for the control of each axis of the antenna, with many restrictions and complex tracking algorithms. Summary of the invention

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

[0005] To achieve the above purpose, the technical solution provided by the present invention is:

[0006] A small-size dual-throw antenna low-orbit terminal tracking method is provided, comprising the following steps:

[0007] Step 1, calculating the target geographic azimuth A and target geographic elevation E of the target in the geographic coordinate system according to the orbit information or real-time position information of the low-orbit satellite target;

[0008] Step 2: Use the inertial navigation system installed on the antenna to measure the carrier heading angle H, carrier pitch angle P and carrier roll angle R during the carrier movement, and use the angle sensors installed on the antenna azimuth axis, pitch axis and third axis to measure the current azimuth angle Az of the antenna. c 、The current elevation angle of the antenna El c and the current third axis angle of the antenna Cr c ;

[0009] Step 3: According to the calculated target geographic azimuth A and target geographic elevation E, obtain the target carrier azimuth A of the target in the carrier coordinate system j and the target carrier pitch angle E j ;

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

[0011] Furthermore, in step 4, the antenna control azimuth angle Az is solved using the following formula: i , antenna control pitch angle El i And the antenna controls the third axis angle Cr i :

[0012]

[0013] In the formula,

[0014] Further, in step 4, when the angle 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 calculation result of the antenna third-axis command angle is zero; when the angle 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 calculation result of the antenna third-axis command angle will automatically compensate for the beam deviation angle caused by the failure to track the azimuth.

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

[0016] Furthermore, in step 4, if the antenna motion path passes through the azimuth dead zone, and the azimuth dead zone ranges from AzL to AzR, the antenna azimuth axis is controlled to rotate in the opposite direction by an angle Az i ', reversal angle Az i 'The calculation is as follows:

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

[0018] (2) Process AzErr as follows:

[0019]

[0020] (3) Perform a remainder operation and introduce a 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 further comprises: step 5, calculating the actual direction of the antenna beam in the geographic coordinate system, that is, the geographic azimuth angle A of the antenna beam c and the antenna beam geographic elevation angle E c , to verify that the antenna’s beam is pointing toward the target:

[0025]

[0026] In the formula,

[0027]

[0028] Furthermore, step 5 also includes determining the geographical azimuth A of the antenna beam. c Processing of data jump:

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

[0030]

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

[0032]

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

[0034]

[0035] Where M is the angle fluctuation range.

[0036] The advantages of the present invention are:

[0037] 1. The tracking method for a low-orbit satellite terminal antenna proposed in the present invention can solve the current satellite tracking problem of a type of small-size low-orbit terminal satellite antenna. According to the tracking strategy proposed in the present invention, when the antenna performs target tracking, when the antenna elevation angle is low, the antenna azimuth axis can track the azimuth axis target angle, and the calculation 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 rises to the azimuth tracking blind spot, the antenna azimuth axis cannot track the azimuth axis target angle, and the calculation result of the antenna third-axis command angle will automatically compensate for the beam deviation angle caused by the failure to track the azimuth. Therefore, there is no need to consider the antenna elevation angle threshold setting, tracking mode switching, and recalculation. The tracking algorithm is simple and the tracking effect is improved.

[0038] 2. When the antenna passes through an azimuth dead zone on the motion path during tracking, the antenna azimuth axis can be controlled to reverse to achieve the required antenna azimuth angle. This can effectively solve the problem of limited installation position of terminal antennas with azimuth dead zones during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and / or other features and advantages of the present invention will become more easily understood through the following description with reference to the accompanying drawings, which are not drawn to scale and some features are exaggerated or reduced to show details of specific components. In the accompanying drawings:

[0040] Figure 1 It is a flow chart of a small-size dual-throw antenna low-orbit terminal tracking method of the present invention;

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

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

[0043] Figure 4 It is the antenna beam pointing of the low-orbit satellite in the antenna coordinate system. DETAILED DESCRIPTION

[0044] The present invention will be described in detail below with reference to the accompanying drawings by means of exemplary embodiments of the present invention. It should be noted that the following detailed description of the present invention is only for the purpose of illustration, and is not intended to limit the present invention.

[0045] The present invention provides a small-size dual-throw antenna low-orbit terminal tracking method, which is used to solve the current satellite tracking problem of a type of small-size low-orbit terminal satellite antenna. The algorithm only needs a set of mathematical formulas and does not need to recalculate the elevation angle of the satellite beam, the motion range of the third axis, or the motion range of the antenna azimuth axis after pattern classification.

[0046] When a low-orbit satellite passes by, when the terminal antenna points its beam to the satellite, if the carrier carrying the antenna changes its attitude, it will directly affect the direction of the antenna, causing its beam to deviate from the satellite, resulting in signal loss of lock. In order to make the antenna fixed on a carrier such as a vehicle, ship, or aircraft always point to the satellite during the movement of the carrier, measures need to be taken to stabilize the direction of the antenna.

[0047] To achieve this control, the usual measure is to establish a mathematical model of antenna pointing and derive it, use its conclusion as the instruction for antenna control, control the antenna axis system to rotate the corresponding angle and form a closed-loop control system with the angle measurement unit, so that the antenna always points to the satellite when the carrier's attitude changes, thereby achieving the purpose of real-time tracking of the antenna.

[0048] Reference Figure 1 As an exemplary embodiment of the present invention, a small-size dual-throw antenna low-orbit terminal tracking method comprises the following steps:

[0049] Step S1, calculating the target geographic azimuth A and the target geographic elevation E of the target in the geographic coordinate system according to the orbit information or real-time position information of the low-orbit satellite target;

[0050] Step S2, using the inertial navigation system installed on the antenna to measure the carrier heading angle H, carrier pitch angle P and carrier roll angle R during the carrier movement, and using the angle sensors installed on the antenna azimuth axis, pitch axis and third axis to measure the antenna current azimuth angle Az c 、The current elevation angle of the antenna El c and the current third axis angle of the antenna Cr c ;

[0051] Step S3, according to the calculated target geographic azimuth A and target geographic elevation E, obtain the target carrier azimuth A of the target in the carrier coordinate systemj and the target carrier pitch angle E j ;

[0052] Step S4: according to the obtained target geographic azimuth angle A and target geographic pitch angle E, the carrier heading angle H, carrier pitch angle P and carrier roll angle R, and the current azimuth angle Az of the antenna c , the azimuth-pitch control strategy is used to solve the antenna control azimuth angle Az i , and use the current angle of the antenna azimuth axis as the coordinate rotation constraint A j =Az c , solve the antenna control pitch angle El i And the antenna controls the third axis angle Cr i , and control the antenna azimuth axis, pitch axis and third axis to rotate to the solved angle, so that the beam of the terminal antenna points to the target, thereby completing the antenna pointing tracking.

[0053] The orbit prediction of low-orbit satellites can be analyzed by the SGP4 (Simplified General Perturbations Version4) algorithm, but the prediction result is an angle in the geographic coordinate system, which cannot be directly used for the angle control of the antenna. It is necessary to first convert it to the angle in the carrier coordinate system, and then convert it to the angle in the antenna coordinate system, which is the command angle required for the final antenna control. In the present invention, the coordinate rotation process is geographic coordinate system->carrier coordinate system->antenna coordinate system.

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

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

[0056] Figure 3 is the antenna pointing direction of the low-orbit satellite in the carrier coordinate system. j X j Y j Z j ;O j X j The axis points to the right of the carrier, O j X j The axis rotation forms the carrier pitch angle; j Y j The axis points to the direction of the carrier's travel, O j Y j The axis rotation forms the carrier roll angle; j Z j The axis points upwards to the carrier, O j Z j The axis rotates to form the carrier heading angle; j Z j Axis and O j X j Axis and O j Y j The axes form a right-handed rectangular coordinate system.

[0057] In the figure, S is the target satellite position; O j The S line is the antenna beam pointing in the carrier coordinate system; A j and E j They are the azimuth and elevation angles of the satellite in the carrier coordinate system, which are obtained by rotating the satellite angles in the geographic coordinate system.

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

[0059] Figure 4 is the antenna pointing direction of the low-orbit satellite in the antenna coordinate system. i X i Y i Z i , O i Z i Axis is the third axis of the antenna, O i Z i The angle of the third axis of the antenna formed by the axis rotation; i X i The axis coincides with the elevation axis of the antenna, Oi X i The rotation of the axis forms the elevation angle of the antenna. When the elevation angle is parallel to the antenna base, the third axis coincides with the antenna azimuth axis. i Y i Axis is the electrical axis direction, O i Z i Axis and O i X i Axis and O i Y i The axes form a right-handed rectangular coordinate system.

[0060] In the figure, S is the target satellite position; O i The S line is the beam pointing 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 Axis clockwise rotation angle Az i , and then rotate around O j X' j The axis is rotated by angle El according to the right hand system i , and finally with the rotated O j Y j 'Rotate angle Cr according to the right-hand principle i .

[0062] For the antenna control system, the antenna pointing process mainly involves precise control of the antenna's axes, namely the azimuth axis, pitch axis and the third axis.

[0063] The present invention proposes the following tracking strategy for a new type of low-orbit terminal satellite antenna with a small third-axis motion range: the control command angle of the antenna azimuth axis adopts an azimuth-pitch type mount solution method, and in solving the command angles of the pitch axis and the third axis, the actual angle of the azimuth axis is used as the coordinate rotation constraint condition.

[0064] The advantages of the antenna control angle obtained in this way are:

[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 of the azimuth axis. The antenna only uses the azimuth and elevation axes for tracking, and the third axis does not move.

[0066] When the satellite elevation angle gradually increases until the actual azimuth movement speed does not meet the tracking requirements, the antenna azimuth axis cannot track the azimuth axis target angle, so the antenna enters the tracking blind area. At this time, the third axis will automatically enter the tracking mode to compensate for the pointing deviation caused by the inadequate tracking of the azimuth. At the same time, the azimuth will automatically move towards the target position at the maximum operating speed of the antenna.

[0067] This strategy does not require orbit prediction to consider the timing of the introduction and retraction of the third axis, nor does it require the establishment of different mathematical models for factors such as antenna elevation angle, third axis motion range, or azimuth motion 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 pitch angle El i And the antenna controls the third axis angle Cr i :

[0069]

[0070]

[0071] In the formula,

[0072] Formulas (1) to (3) are used to control each axis of the antenna respectively, so:

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

[0074] When the satellite orbit elevation angle gradually increases, the running speed of the antenna azimuth axis gradually increases. Assuming that the beam elevation angle points to the zenith, the theoretical azimuth movement speed should reach infinity. Therefore, there is a blind area in the azimuth when approaching the zenith. When the elevation angle gradually increases to the blind area, the third axis movement result calculated by formula (3) gradually increases, which is equivalent to using the movement of the third axis to compensate for the limited part of the azimuth movement. Since the third axis is usually set orthogonal to the pitch axis, the movement speed of the third axis is very small within the azimuth blind area, which can achieve a good compensation effect.

[0075] When the satellite orbit elevation angle gradually decreases from the highest point, the third axis motion result calculated by formula (3) gradually decreases until it reaches zero. At low elevation angles, the azimuth and elevation axes continue to be used for tracking.

[0076] Formulas (1) to (3) are always used throughout the entire tracking process. When the elevation angle gradually increases, there is no need to classify the satellite beam elevation angle, the third axis motion range, or the antenna azimuth axis motion range or set restrictions due to the timing of introducing third-axis tracking. At the same time, when the elevation angle gradually decreases, there is no need to consider when the third axis returns to zero and the speed of returning to zero, and perform mode classification again. The entire process is completely unified with three formulas, the tracking curve is smooth, and the tracking error is stable without jumps when the third axis is involved 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 means that the antenna azimuth axis can track the target angle, and the calculation 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 means that the antenna azimuth axis cannot track the target angle, and the calculation result of the antenna third axis command angle will automatically compensate for the beam deviation angle caused by the failure of azimuth tracking. Preferably, the predetermined angle tolerance threshold is in the range of 0.2°-0.5°, and more preferably 0.2°.

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

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

[0080] (2) Process AzErr as follows:

[0081]

[0082] (3) Perform a remainder operation and introduce a 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 elevation angle of the satellite orbit gradually increases, if the antenna moving path needs to pass through an azimuth dead zone, the antenna azimuth is first controlled to reverse. During this process, the third axis begins to intervene in the movement to compensate for the tracking angle deviation caused by the azimuth reversal, thereby effectively solving the problem of limited installation position of terminal antennas with azimuth dead zones during operation.

[0087] In order to verify whether the antenna beam points to the target angle during the debugging process of the terminal antenna, the setting of various parameters and the formulation of the tracking strategy all need to use the beam space pointing as a reference basis, the antenna tracking method of the present invention may also include: step S5, calculating the actual pointing of the antenna beam in the geographic coordinate system, that is, the antenna beam geographic azimuth A c and the antenna beam geographic elevation angle E c , to verify that the antenna’s beam is pointing toward the target:

[0088]

[0089] In the formula,

[0090]

[0091] Due to the accuracy of the sensor, there is a fluctuation range for the heading roll and pitch angles. The A calculated by the above formula c As a result, there may be data jumps in adjacent quadrants, resulting in inaccurate spatial pointing data. To this end, step S5 may also include calculating the geographic azimuth angle A of the antenna beam. c Processing of data jump:

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

[0093]

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

[0095]

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

[0097]

[0098] Where M is the angle fluctuation range.

[0099] Those skilled in the art should understand that, since two antennas are relay tracking, the control of antenna B is completely consistent with that of antenna A, but since there is a delay between the data communication between the two antennas, antenna B needs to predict the data of two communication cycles in advance, and the prediction is performed by second-order extrapolation. During the entire debugging process, the spatial pointing is used as a reference, combined with the level fluctuation range, as the basis for debugging the dynamic parameters related to the tracking error.

[0100] Therefore, as described above, according to the tracking strategy proposed in the present invention, when the antenna is tracking a target, when the antenna elevation angle is low, the antenna azimuth axis can track the azimuth axis target angle, and the calculation result of the antenna third-axis command angle is zero, which is consistent with the traditional three-axis antenna tracking effect; when the antenna elevation angle rises to the azimuth tracking blind spot, the antenna azimuth axis cannot track the azimuth axis target angle, and the calculation result of the antenna third-axis command angle will automatically compensate for the beam deviation angle caused by the failure of azimuth tracking. Therefore, the tracking method of the present invention does not need to consider issues such as antenna elevation angle 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 the exemplary embodiments of the present invention may be combined in the same or similar manner into one or more other embodiments, combined with the features in other embodiments or substituted for the corresponding features in other implementations. The technical solutions obtained by these combinations or substitutions shall also be deemed to be included in the protection scope of the present invention.

Claims

1. A small-size dual-throw antenna low-orbit terminal tracking method, characterized in that: The following steps are involved: Step 1, calculating the target geographic azimuth A and target geographic elevation E of the target in the geographic coordinate system according to the orbit information or real-time position information of the low-orbit satellite target; Step 2: Use the inertial navigation system installed on the antenna to measure the carrier heading angle H, carrier pitch angle P and carrier roll angle R during the carrier movement, and use the angle sensors installed on the antenna azimuth axis, pitch axis and third axis to measure the current azimuth angle Az of the antenna. c 、The current elevation angle of the antenna El c and the current third axis angle of the antenna Cr c ; Step 3: According to the calculated target geographic azimuth A and target geographic elevation E, obtain the target carrier azimuth A of the target in the carrier coordinate system j and the target carrier pitch angle E j ; Step 4: Based on the obtained target geographic azimuth A and target geographic pitch angle E, the carrier heading angle H, carrier pitch angle P and carrier roll angle R, and the current antenna azimuth Az c , the azimuth-pitch control strategy is used to solve the antenna control azimuth angle Az i , and use the current angle of the antenna azimuth axis as the coordinate rotation constraint A j =Az c , solve the antenna control pitch angle El i And the antenna controls the third axis angle Cr i , and control the antenna azimuth axis, pitch axis and third axis to rotate to the solved angle, so that the beam of the terminal antenna points to the target, thereby completing the antenna pointing tracking.

2. The small-size dual-throw antenna low-orbit terminal tracking method according to claim 1 is characterized in that: In step 4, the antenna control azimuth angle Az is solved using the following formula: i , antenna control pitch angle El i And the antenna controls the third axis angle Cr i : In the formula, 3. The small-size dual-throw antenna low-orbit terminal tracking method according to claim 1 or 2, characterized in that: In step 4, when the angle between the actual angle of the antenna azimuth axis and the target angle is less than the preset angle tolerance threshold, the antenna azimuth axis can track the target angle, and the calculation result of the antenna third-axis command angle is zero; when the angle between the actual angle of the antenna azimuth axis and the target angle is greater than or equal to the preset angle tolerance threshold, the antenna azimuth axis cannot track the target angle, and the calculation result of the antenna third-axis command angle will automatically compensate for the beam deviation angle caused by the failure to track the azimuth.

4. The small-size dual-throw antenna low-orbit terminal tracking method according to claim 3 is characterized in that: The predetermined angle tolerance threshold is in the range of 0.2°-0.5°.

5. The small-size dual-throw antenna low-orbit terminal tracking method according to claim 1 or 2, characterized in that: In step 4, if the antenna motion path passes through the azimuth dead zone, the azimuth dead zone range is AzL ~ AzR, then the antenna azimuth axis is controlled to rotate in the opposite direction by an angle Az i ', reversal angle Az i 'The calculation is as follows: (1) Calculate the required antenna azimuth rotation angle: AzErr = Az i -Az c ; (2) Process AzErr as follows: (3) Perform a remainder operation and introduce a variable P: P = (Az i +AzErr')%360; And perform the following operation on P: (4) Determine the reverse rotation angle of the antenna azimuth axis:

6. The small-size dual-throw antenna low-orbit terminal tracking method according to claim 1 or 2, characterized in that The method also includes: step 5, calculating the actual direction of the antenna beam in the geographic coordinate system, that is, the geographic azimuth angle A of the antenna beam c and the antenna beam geographic elevation angle E c , to verify that the antenna’s beam is pointing toward the target: In the formula, 7. The small-size dual-throw antenna low-orbit terminal tracking method according to claim 6 is characterized in that: Step 5 also includes calculating the antenna beam geographic azimuth A c Processing of data jump: When the azimuth angle A of the low-orbit satellite is in the first quadrant: When the azimuth angle A of the low-orbit satellite is in the second or third quadrant: When the azimuth angle A of the low-orbit satellite is in the fourth quadrant: Where M is the angle fluctuation range.

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