KR20190087008A - Hybrid tracking method and apparatus consisting of step tracking and mono-pulse tracking for improve performance in tracking satellite in mobile satellite communication terminal - Google Patents

Abstract

According to the present invention, provided is a hybrid tracking method of step tracking and mono-pulse tracking for improving satellite tracking performance of a mobile satellite communication terminal, which comprises: a search mode performance step for performing a search mode when the level of a beacon signal is less than or equal to the threshold value; and a tracking mode performance step for performing a tracking mode when the level of the beacon signal is higher than the threshold value. In the search mode performance step, the raster scan is performed when the level of the beacon signal is less than the tracking level. If the level of the beacon signal is higher than the tracking level, the process proceeds to the tracking mode, so that satellite tracking is possible in a wide area, and high speed and high precision satellite tracking performance can be secured.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid tracking method and apparatus for tracking tracking and monopulse tracking for improving satellite tracking performance of a mobile satellite communication terminal,

The present invention relates to a satellite tracking method of a satellite antenna system mounted on a mobile platform such as a vehicle, a ship, an aircraft, and the like. The satellite tracking method uses a step trace using a beacon signal, which is a satellite signal, and a monopulse tracking, To a method for improving satellite tracking performance of an antenna system.

In order to provide a stable communication link, it is necessary to install a technique that can steadily and precisely orient the satellite even in a situation where disturbance such as position and attitude change of the mobile platform is applied to the antenna system. Satellite-oriented technologies can be roughly classified into an open loop method and a closed loop method.

The open-circuit method is a satellite-oriented method that relies on an inertial navigation system (INS) to measure the latitude, longitude, and altitude of an antenna system, GPS and attitude change Euler angles. In this method, the azimuth angle, elevation angle, and polarization used by the antenna on the earth surface (Global Coordinate) are calculated by using the latitude, longitude and altitude information of the antenna obtained through GPS and the latitude, longitude and altitude information of the satellite to be communicated. Calculate the polarization angle depending on whether or not. Then, the disturbance Euler angles are measured through the INS, the angle that the current antenna is aimed at is measured by using the encoder, and then the inverse kinematics is taken into consideration in consideration of the current disturbance so that the antenna can be oriented in the satellite direction on the earth surface coordinate system And a method of applying an angle command to the antenna. However, when this method is used, measurement errors of sensors such as antenna manufacturing error, sensor mounting position error, and gyro drift can cause satellite directional error, which may degrade communication performance.

The closed loop method is a method to receive satellite signals and use them for satellite orientation, which enables more robust satellite tracking than the open circuit method. Typical closed loop methods include step tracking and monopulse tracking. Among them, the step tracking receives a beacon signal among the satellite signals, performs a circle or box shape scan for each step, directs to a place where the level of the beacon signal is highest during scanning, It is a way to track satellites repeatedly. However, since the beacon signal contains noises and the level change of the beacon signal is gentle in accordance with the change of the directivity angle in the vicinity of the satellite directing point, high tracking performance can not be expected because the tracking uncertainty becomes large near the satellite directing point. Among the closed loop method, monopulse tracking is a method of using a monopulse signal produced by processing a beacon signal for satellite tracking. This monopulse signal is also referred to as a monopulse error, which means a satellite-directed error in the antenna coordinate system of the direct antenna. Therefore, high-speed, high-precision real-time satellite tracking is possible if it is directly used for satellite tracking. However, such a monopulse tracking can be used in only a part of the vicinity of the satellite directing point. Since the monopulse tracking has a linear characteristic only in a narrow area, it can be used for satellite tracking only in this specific area.

It is an object of the present invention to provide a mixed tracking method and apparatus for step tracking and monopulse tracking for improving satellite tracking performance of a mobile satellite communication terminal.

In order to solve the above problems, a hybrid tracking method of step tracking and monopulse tracking for improving satellite tracking performance of a mobile satellite communication terminal according to the present invention is characterized in that if the level of the beacon signal is below the threshold, A search mode performing process; And performing a tracking mode when the level of the beacon signal is higher than the threshold value, and performing a search mode when the level of the beacon signal is lower than the threshold, If the level of the beacon signal is higher than the tracking level, the process proceeds to the tracking mode, and it is possible to track the satellite in a wide area, thereby ensuring high-speed, high-precision satellite tracking performance.

In one embodiment, the tracking mode performing step includes a monopulse tracking step of performing monopulse tracking in an environment in which monopulse tracking is possible; And a step tracking step of performing step tracking within the step traceable area in an environment where monopulse tracking is not possible.

In one embodiment, the raster scan interval is narrower than the step trackable area so that the scan interval of the raster scan is at least once within the step trackable area for minimizing the time required for the raster scan, And the raster scan interval increases in proportion to a difference between the level of the beacon signal and the tracking level.

In one embodiment, in the step tracking process, the step traceable region may be selected at a level where the level of the beacon signal exceeds a level of a side lobe of the antenna radiation pattern.

In one embodiment, the monopulse tracking process or the step tracking process is performed according to availability of the monopulse signal for monopulse tracking, and the level of the beacon signal in the monopulse tracking process or the step tracking process is And enters the search mode if the level is below the tracking level.

In one embodiment, in the monopulse tracking process, a pointing command to an antenna is received from a monopulse control unit, a disturbance measurement angle is received from an inertial sensor (INS), and the received pointing command And outputting the pointing angle of the antenna based on the disturbance measurement angle.

In one embodiment, in the monopulse tracking process, a value obtained by subtracting the disturbance measurement angle from a sum of a reference angle of the antenna and a first pointing angle in the pointing command is input to the 3-axis drive system for the input The pointing angle of the antenna can be outputted in consideration of the influence of the antenna.

According to the present invention, in a communication environment in which monopulse tracking is not possible, the satellite tracking can be performed in a wide area through the step tracking. In a communication environment capable of monopulse tracking, step tracking is performed in a wide area near the satellite directing point, Satellite tracking is possible. As a result, satellite tracking is possible in a wider area than monopulse tracking alone, and monopulse tracking enables high-speed, high-precision satellite tracking performance rather than single step tracking.

Since the step trace traces to the monopulse trace usable region, the interval of the raster scan can be selected relatively widely, and it takes less time to carry out the entire satellite tracking including retrace.

In addition, the satellite tracking control structure capable of simultaneously inputting the mono pulse signal of the present invention and the angle command of the initial direction, raster scan, and step tracking, And the like.

1 is a conceptual diagram of a satellite tracking system of a mobile satellite communication terminal according to the present invention.
FIG. 2 shows a coordinate system and an inertial navigation sensor arrangement of a three-axis driving antenna system according to the present invention.
FIG. 3 shows a receive radiation pattern of a beacon signal received in an elevation angle direction according to the present invention.
4 is a conceptual diagram of step tracking according to the present invention.
5 is a conceptual diagram of a raster scan according to the present invention.
6 shows a theoretical mono-pulse signal usable area according to the present invention in accordance with the present invention.
FIG. 7 is a flowchart of a step tracking method and a monopulse tracking mixed tracking method for improving satellite tracking performance of a mobile satellite communication terminal according to the present invention.
FIG. 8 shows a detailed configuration of an integrated controller for performing a mixing tracking method according to the present invention and a mixed tracking controller using a mode switch.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, It will be possible. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Like reference numerals are used for similar elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Should not.

The suffix modules, blocks, and parts for the components used in the following description are given with or taken into consideration only for ease of specification, and do not have their own meaning or role.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, a method and apparatus for tracking a mixed step tracking and monopulse tracking for improving satellite tracking performance of a mobile satellite communication terminal according to the present invention will be described.

In this regard, the present invention is a method of combining the above-described tracking methods for satellite tracking. First, the open circuit method is most influenced by INS gyro drift during sensor measurement error. Therefore, if the satellite is oriented only by the opening method, the antenna system can be directed to the wrong place. In step tracking, the beacon signal is used for satellite tracking. Since the beacon signal has the highest point on the main lobe and the highest point on the side lobe, when the step tracking is performed on the side lobe, And satellite tracking may not be possible. Thus, step tracking can also be used only in certain areas where beacon signals are present on the main lobes, as in monopulse tracking. Although this step-tracking area is wider than the monopulse tracking area, it can not be used for high-speed satellite tracking because it requires a driving time per step, and satellite tracking performance is less favorable than monopulse tracking near the satellite- . In case of monopulse tracking, monopulse signal, which means satellite direction error, is used for satellite tracking. Therefore, it is possible to perform high-speed real-time satellite tracking, but it can be used only in a relatively narrow area than a step tracking near a satellite directing point. If the signal can not be acquired, monopulse tracking can not be used. If the satellite tracking is performed by mixing the step tracking and the monopulse tracking as in the present invention, the satellite tracking is performed using the step tracking in a wide area near the satellite direction point, and the monopulse tracking is performed in the narrow area near the satellite direction point High-speed and high-precision satellite tracking can be performed. However, step tracking essentially performs directional angular control for beacon-level peak orientation, and monopulse tracking uses a satellite-directed error called a monopulse signal as feedback, so the two tracking methods have different control system configurations. When different control systems are embedded in one antenna system, the mode change between the control systems can degrade the stability of the antenna system. Therefore, it is necessary to develop a new control algorithm to maintain system stability in order to mix the two tracking systems.

Specifically, in the present invention, the antenna system performs initial satellite orientation by an open circuit method. At this time, if the sensor can not direct to the vicinity of the satellite due to a measurement error, it receives a beacon signal, performs a wide scan of a raster scan shape, and allows a beacon signal to enter the main lobe. If the antenna enters the main lobe of the beacon signal, if the monopulse signal can be used while performing the satellite tracking using the step tracking, if the monopulse signal enters the linear region, the monopulse tracking is performed to track the satellite. In this way, monopulse tracking can be performed in a wide range of communication environments. If the monopulse signal can not be acquired, the satellite can be traced using only step tracking. In the case of mixed tracking, satellite tracking is possible in a wide area near the satellite directing point, and high speed and high precision tracking performance is the same as that of monopulse tracking in a narrow region near the satellite directing point. In addition, in the present invention, in order to use a step trace and a monopulse trace in combination, a directional error feedback (monopulse signal) of the monopulse tracking and a tracking which receives angular command and angular feedback of the initial orientation, raster scan, The antenna drive system also maintains stability in the conversion of the tracking mode using the control structure.

Hereinafter, a mixed tracking method and apparatus for step tracking and monopulse tracking for improving satellite tracking performance of a mobile satellite communication terminal according to the present invention will be described with reference to the accompanying drawings.

In this regard, FIG. 1 shows a conceptual diagram of a satellite tracking system 1000 of a mobile satellite communication terminal according to the present invention. That is, as shown in FIG. 1, the satellite tracking system may refer to a system in which a vehicle having a mobile satellite communication terminal including the antenna system 100 tracks the satellite 200. FIG. 2 shows a coordinate system and an inertial navigation sensor arrangement of the three-axis driving antenna system 100 according to the present invention. The satellite tracking of the mobile terminal is operated with the same concept as in Fig. The antenna system 100 mounted on the mobile platform measures the position information of the antenna system and the disturbance caused by the mobile equipment with the INS and GPS inertial navigation sensors mounted on the mobile platform. A communication link can be maintained when the antenna system 100 accurately coordinates the satellite while compensating for such disturbances. FIG. 2 illustrates the three-axis driving of the azimuth angle, elevation angle and polarization angle of the antenna system 100 and the arrangement of the inertial navigation sensor, but this can be changed depending on the operating area and whether or not the polarization is used. The coordinate system used in the satellite tracking antenna system is composed of an earth surface coordinate system (Earth Coordinate), an antenna bottom coordinate system, and an antenna coordinate system as shown in FIG. 1 and FIG. In case of the open circuit method which does not use the satellite signal as feedback, the antenna should be orientated on the surface coordinate system of the earth using the latitude, longitude and altitude information of the antenna and satellite latitude, altitude and hardness information using GPS, To calculate the polarization angle. In addition, we solve the inverse kinematics considering the disturbance and calculate the angular command of each rotation axis so that the antenna can compensate the disturbance and direct the satellite. Next, the current rotation angle is fed back through the encoder, and the angular command calculated previously is controlled so that each rotation axis of the antenna follows. This open-loop method, which does not utilize satellite signals, is used only in the early satellite orientation because of the inaccuracy of the satellite-oriented performance due to the error of the inertial navigation sensor.

Meanwhile, FIG. 3 shows a reception radiation pattern of a beacon signal received in an elevation angle direction according to the present invention. As shown in FIG. 3, the reception radiation pattern of the beacon signal has a main lobe and a side lobe according to a change in altitude angle.

Meanwhile, FIG. 4 shows a conceptual view of step tracking according to the present invention.

Referring to FIG. 4, the antenna system after the paper machine may perform step tracking or monopulse tracking immediately if step tracking or monopulse tracking is possible, but may not be able to do so. Therefore, in this case, it is necessary to perform raster scan.

That is, FIG. 5 shows a concept of raster scan according to the present invention. A raster scan having a shape as shown in FIG. 5 is performed. The raster scan is performed based on the initial orientation point on the earth's surface coordinate system. During the scan, the beacon signal is received, and the beacon level on the beacon pattern shown in FIG. In the case of exceeding the side lobe during scanning, the raster scan is stopped and step tracking is performed. In this process, the raster scan interval of FIG. 5 is selected such that the beacon level of FIG. 3 can enter at least one time in an area where the main lobe is more than the main scan lane. This choice allows the raster scan to start step tracking reliably, and maximizes the raster scan interval, minimizing the time required for raster scanning. This can shorten the time spent on the initial satellite tracking and satellite retracement.

When the beacon level enters the step tracking area, the antenna system receives the beacon signal and performs a circle scan as shown in FIG. 5 on the earth's surface coordinate system. Then, it is aimed that the beacon level is the highest during the scan, and then the circle scan is performed again based on the point.

6 illustrates a theoretical mono pulse signal usable area according to the present invention in accordance with the present invention. Referring to FIG. 6, a monopulse signal can be used within a certain angle range based on a specific angle of an altitude angle, and this range can be referred to as a monopulse linear region.

Meanwhile, FIG. 7 shows a flowchart of a step tracking method and a monopulse tracking method for improving satellite tracking performance of a mobile satellite communication terminal according to the present invention. Meanwhile, FIG. 8 shows a detailed configuration of an integrated controller for performing the mixed tracking method according to the present invention and a mixed tracking controller using a mode switch.

As shown in FIG. 7, a mixed tracking method of step tracking and monopulse tracking for improving satellite tracking performance of a mobile satellite communication terminal includes a search mode performing step (S100) and a tracking mode performing step (S200). With respect to the search mode performing step S100, if the level of the beacon signal is below the threshold value, the search mode is performed. With respect to the tracking mode performing process (S200), if the level of the beacon signal is higher than the threshold value, a tracking mode is performed. If the level of the beacon signal is higher than the level of the tracking signal in step S100, the controller performs raster scan if the level of the beacon signal is below the tracking level. If the level of the beacon signal is higher than the level of the tracking signal, ). At this time, the threshold value may be set to a specific value as shown in FIG. 7, but may be adaptively changed according to specifications and antenna specifications required in satellite communication. For example, although the threshold is set to -55 dBm in FIG. 7, it may be set to a different value in FIG. 2 and FIG. Referring to FIG. 2, it may be set to about -60 dBm in consideration of the 3 dB beam width or about -65 dBm depending on the tracking level. Meanwhile, referring to FIG. 6, the threshold value in relation to the mono-pulse linear region can be set to about -60 dBm.

In order to minimize the time required for the raster scan, the raster scan interval is set so that the scan interval of the raster scan is at least once in the step-traceable area, It can be configured to be narrower than the possible area. The raster scan interval may increase in proportion to the difference between the level of the beacon signal and the tracking level.

The process of performing the tracking mode (S200) includes a monopulse tracking process (S210) for performing monopulse tracking in an environment where monopulse tracking is possible, and a step tracking in a steptable area in the case where the monopulse tracking is not possible And a step tracking process (S220) performed. That is, the monopulse tracking process (S210) or the step tracking process (S220) may be performed depending on whether the monopulse signal for monopulse tracking is available or not. If the level of the beacon signal is below the tracking level in the monopulse tracking process (S210) or the step tracking process (S220), the user can enter the search mode (S100).

Meanwhile, in the step tracking process (S220), the step traceable region can be selected at a level where the level of the beacon signal exceeds the level of a side lobe of the antenna radiation pattern.

On the other hand, the initial satellite direction, raster scan, and step tracking uses a control algorithm except for the dotted box in Fig. 8 in that an angle command is applied to the antenna driving system on the global surface coordinate system. The difference between the angle command and the disturbance due to the INS in FIG. 8 and the coordinate transformation is a one-dimensional description of the inverse kinematics in an easy-to-understand manner.

 Theoretically, the monopulse signal can be used within the intersection of the basic board and the higher-order mode of the beacon signal of FIG. However, this monopulse signal can only be used in the tracking system in this linear region because it is linear within the narrower region near the satellite directing point within the intersection point. The monopulse tracking controller can be operated via the mode switch if it has reached the monopulse trackable region through step tracking. In this case, as described in the general one-degree-of-freedom secondary system, it has the following characteristics.

Where J is the moment of inertia, b is the viscous friction, and c is the spring coefficient. The driving apparatus of each axis can be constituted by a PI controller as shown in the following equation (2).

Where K _P is the position gain and K _I is the integral gain. Next, the integral controller in the monopulse signal is expressed by Equation (3) below.

Where K _MI is the integral gain. When a monopulse signal can be used, the transfer function for the input / output transfer function and the output relative to the disturbance can be obtained using Equations (4) and (5) below using Equations (1) and (2)

Here, _Gco is the transfer function of the antenna directivity angle relative to the open circuit method directive command, and _Gdo is the directivity transfer function relative to the disturbance. The effect of the final system input on the antenna orientation through the final value summation is as shown in Equations 6 and 7 below.

Then, when a monopulse signal is available, the input / output transfer function is obtained by Equations (1) to (3).

Here, G is a _co-oriented commands to the method compared to an antenna oriented transfer function of each of opening, _do G is the transfer function of the antenna beam angle than the actual satellite position. And G _mo is the transfer function of the antenna directivity angle relative to the disturbance. It can be seen that each loop transfer function of the transfer function expressed by Equations (8) to (10) includes Equation (3) for the monopulse tracking controller. This integral controller raises the system type and plays a role to prevent the direction command of the existing open circuit method from affecting the antenna directivity angle. The final values are summarized in the following equations (11) to (13).

7 and 8, in the monopulse tracking process (S210), the control unit 800 receives a pointing command for the antenna from the monopulse control unit 810 and transmits the pointing command to the inertial sensor INS from the disturbance measurement angle, and output the pointing angle of the antenna based on the received pointing command and the disturbance measurement angle. Meanwhile, in the monopulse tracking process (S210), a value obtained by subtracting the disturbance measurement angle from the sum of the reference angle of the antenna and the first pointing angle in the pointing command is inputted, and the 3-axis drive system 820 The angle of the antenna can be calculated in consideration of the influence on the antenna.

Thereby, the drive system 820 resides in the same control loop as in FIG. 8 and performs a smooth monopulse tracking mode transition by connecting additional control loops in parallel only when monopulse tracking is available. This tracking method of mixing can be explained by the structure shown in FIG. Basically, the initial satellite direction and raster scan are defined as the search mode, and the antenna system switches to the tracking mode when step tracking is available in the search mode. Monopulse tracking is performed when monopulse tracking is possible in tracking mode, and step tracking is performed when monopulse tracking is impossible. It is impossible to perform monopulse tracking during the tracking process, and if the step tracking can not be performed, the tracking mode can be operated again to perform the satellite tracking again. This makes it possible to perform satellite tracking more quickly in a wider area when monopulse tracking alone is used, and in the case where monopulse tracking is impossible according to the communication environment, it is possible to perform satellite tracking through step tracking. In addition, if monopulse tracking is possible, monopulse tracking can maintain high-speed, high-precision satellite tracking.

According to a software implementation, the design and parameter optimization for each component as well as the procedures and functions described herein may be implemented as separate software modules. Software code can be implemented in a software application written in a suitable programming language. The software code is stored in a memory and can be executed by a controller or a processor.

Claims (7)

In a hybrid tracking method of step tracking and monopulse tracking for improving satellite tracking performance of a mobile satellite communication terminal,
Performing a search mode when the level of the beacon signal is below a threshold value; And
And performing a tracking mode when the level of the beacon signal is higher than the threshold,
In the search mode,
Wherein the controller performs raster scan if the level of the beacon signal is below the tracking level and proceeds to the tracking mode if the level of the beacon signal is higher than the tracking level. Mixed tracking method of tracking. The method according to claim 1,
In the tracking mode,
A monopulse tracking process that performs monopulse tracking in an environment where monopulse tracking is possible; And
Wherein step tracing is performed in a step traceable area in an environment where monopulse tracking is not possible. 3. The method of claim 2,
Wherein the raster scan interval is narrower than the step traceable area so that the scan interval of the raster scan is at least once in the step traceable area so as to minimize the time required for the raster scan,
Wherein the raster scan interval is increased in proportion to a difference between the level of the beacon signal and the tracking level. 3. The method of claim 2,
In the step tracking process,
Wherein the step traceable region is selected at a level at which the level of the beacon signal exceeds a level of a side lobe of the antenna radiation pattern. 3. The method of claim 2,
Performing the monopulse tracking process or the step tracking process according to availability of the monopulse signal for the monopulse tracking,
Wherein when the level of the beacon signal is below the tracking level in the monopulse tracking process or the step tracking process, the search mode enters the search mode. 3. The method of claim 2,
In the monopulse tracking process,
The method includes receiving a pointing command for an antenna from a monopulse control unit, receiving a disturbance measurement angle from an inertial sensor (INS), and determining a pointing command for the antenna based on the received pointing command and the disturbance measurement angle Wherein the step of outputting the angular velocity of the monopulse tracking is performed. The method according to claim 6,
In the monopulse tracking process,
A pointing angle of the antenna is calculated in consideration of an influence on the 3-axis drive system with respect to the input by subtracting the disturbance measurement angle from the sum of the reference angle of the antenna and the first pointing angle in the pointing command, Wherein the step tracking and the monopulse tracking are mixed.

Images