A ground-based automatic tracking and receiving system for low-orbit satellite constellations

Abstract

The present application relates to a ground-based automatic tracking and receiving system for a low-orbit satellite constellation, which includes an antenna end and a control end. The antenna end is a hemispherical multi-beam phased array antenna.

Description

Technical Field

[0001] The present application relates to a method for automatically tracking and receiving satellite signals, which belongs to the field of satellite communications, and specifically to a ground-based automatic tracking and receiving system for low-orbit satellite constellations. Background Art

[0002] Low-orbit satellites, due to their proximity to Earth, can capture more detailed Earth observation features and offer low-latency data transmission, making them suitable for high-speed communications satellite constellations. To conveniently access real-time payload information transmitted by satellites, a ground-based receiving system is required to continuously track the satellites and acquire the data.

[0003] Due to the characteristics of their orbits, low-orbit satellites have short orbital periods and transit times. For example, a low-orbit inclined circular orbit satellite at an altitude of 600 kilometers may only transit for a dozen minutes. Mobile satellite receiving antennas must quickly track satellite position changes in real time. In particular, when satellites form a constellation, multiple satellites may enter simultaneously. Satellite antennas must track multiple satellites and filter out satellites if the number of satellites they can receive exceeds the limit.

[0004] Currently, there are several main antenna technologies for mobile satellite communications: parabolic antennas, flat-panel array antennas, and phased array antennas. The advantages of parabolic antennas are their strong signal reception capabilities and relatively low cost, making the entire antenna system highly cost-effective. However, their disadvantages are that they must be constructed in a mushroom shape, which increases wind resistance and requires mechanical adjustment for antenna alignment. Flat-panel array antennas offer small size, light weight, low wind resistance, and ease of installation and use, but they also require mechanical adjustment for antenna alignment. Phased array antennas, due to their powerful functionality, flexible operation, computer-controlled inertia-free beam scanning, and multi-beam phased array antennas that can receive multiple target signals, have become the primary antenna form for many military phased array antennas or satellite applications. They provide flexibility for capturing and tracking satellite signals while on the move and are the mainstream antenna for current and future mobile ground stations.

[0005] The current mobile satellite receiving system is mainly used for receiving television satellites (see Chinese patent application No. 201610307432.6 "A mobile satellite receiving system") or Beidou and GPS navigation satellites (see Chinese patent application No. 201410370647.3 "A Beidou satellite signal receiving system and method"). The orbital altitude of these satellites is higher than that of low-orbit satellites, and due to the characteristics of the satellite orbit or the purpose of signal reception, the ground receiving end does not need to continuously track the satellite, and is not suitable for the low-orbit satellite constellation that requires continuous tracking involved in this application.

[0006] Current mobile satellite receiving systems are primarily used to receive geosynchronous satellite signals and are used on fixed platforms, vehicles, and ships. Specifically, for example, the Chinese patent application "A Mobile Satellite Receiving System" (Application No. 201610307432.6) proposes a vehicle-mounted satellite receiving system based on a control system, gyroscopic sensors, an electronic compass, a GPS module, and a servo system. The system mechanically adjusts the antenna's direction to accommodate the movement and displacement of a ground vehicle. This system faces the following challenges when used in low-orbit satellite constellations: 1. The system is used to track television satellites, which are in geosynchronous orbits and have minimal positional fluctuations relative to the ground. Once a satellite is found, its position can be assumed to be unchanged. However, the position of low-orbit satellites relative to the ground continuously changes, requiring strategies to predict the satellite's flight trajectory and track its position changes. 2. This method uses a mechanical device to adjust the direction of the satellite antenna to accommodate changes in the vehicle's position and attitude. However, during a low-orbit satellite's transit, the pitch angle varies from 0 to 90 degrees and the azimuth angle from 0 to 360 degrees. The mechanical device must respond to these changes in the satellite's position within a short period of time, and the mechanical motion device is prone to failure, reducing system reliability. 3. The system's antenna can only be aimed at a single satellite and cannot simultaneously track multiple satellites within its territory. For low-orbit satellite constellations, multiple satellites may enter simultaneously, making this system difficult to meet. Patent "A Beidou Satellite Signal Receiving System and Method" (Application No. 201410370647.3) proposes a system for receiving Beidou signals. While it can receive signals from multiple satellites, it primarily processes Beidou signals, and the antenna does not track satellites.

[0007] Therefore, there is an urgent need in this field to develop a satellite receiving system for low-orbit satellite constellations that can reliably track rapidly changing positions. Summary of the Invention

[0008] The purpose of this application is to provide a satellite automatic tracking system based on a multi-beam phased array antenna that can reliably track rapidly changing positions.

[0009] In order to achieve the above objectives, this application provides the following technical solutions.

[0010] The present application provides a ground automatic tracking and receiving system for a low-orbit satellite constellation, which includes an antenna end and a control end.

[0011] Wherein, the antenna end is a hemispherical multi-beam phased array antenna.

[0012] In one embodiment of the present application, the antenna end is equipped with a multi-channel signal processing module.

[0013] In another embodiment of the present application, the antenna end is further equipped with a three-axis gyroscope and a GPS module.

[0014] In another embodiment of the present application, the control end includes a communication module, an orbit extrapolation module, an antenna direction calculation module, an antenna direction correction module, a satellite screening module, and a data processing module.

[0015] In another embodiment of the present application, the hemispherical multi-beam phased array antenna has antenna array elements installed on a spherical surface, which can synthesize a multi-beam antenna to receive satellite signals, and the internal beam controller controls the direction of each beam of the antenna according to the control instructions sent by the control end, thereby aiming at the satellite.

[0016] Compared with the prior art, the beneficial effect of the present application is that the satellite receiving system for low-orbit satellite constellations of the present application introduces a hemispherical multi-beam phased array antenna, which can control the beam direction through the beam control circuit, eliminates the mechanical adjustment device in the system, increases the system reliability, and can track satellites with rapidly changing positions. The antenna control and processing module adopts a multi-channel processing method, which can realize the tracking of multiple satellites and satellite data processing at the same time. The control device of the system uses an orbital extrapolation model to predict the satellite position, calculates the antenna pitch angle and azimuth angle in combination with the ground antenna position, and corrects the above angles in combination with the satellite attitude to achieve the purpose of real-time tracking. In the case of receiving multiple satellites, the satellite can be selectively tracked according to the length of time the satellite is connected to the antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the ground automatic tracking and receiving system for low-orbit satellite constellations in this application.

[0018] Figure 2 This is a schematic diagram of the calculation of antenna and satellite positions under geocentric coordinates of this application. DETAILED DESCRIPTION

[0019] The technical solution of the present application will be clearly and completely described below in conjunction with the accompanying drawings and embodiments of the present application.

[0020] This application proposes an automatic satellite tracking system based on a multi-beam phased array antenna. The system consists of an antenna and a control unit. The antenna is a hemispherical multi-beam phased array antenna. Its hemispherical shape helps it search for satellite targets within an azimuth angle of 0 to 360 degrees. Internal beam control circuitry adjusts the beam direction to align with satellites without mechanically moving the antenna. The multi-beam antenna can allocate beams to track multiple satellites. The antenna is equipped with a multi-channel signal processing module, enabling simultaneous reception and processing of data from multiple satellites. It is also equipped with a three-axis gyroscope and a GPS module to obtain the antenna's real-time heading, pitch, and roll angles, as well as its latitude, longitude, and altitude. This positioning and attitude information is stored in the antenna's status information. The processed satellite data and its acquired attitude information are transmitted to the control unit via the same communication module, with the data separated by different frame formats. The control unit primarily consists of a communication module, an orbit extrapolation module, an antenna direction calculation module, an antenna direction correction module, a satellite screening module, and a data processing module. The communication module sorts the status information and data information transmitted by the antenna end, and distributes them to different modules for processing. The communication module sends the data information to the data processing module, processes the data and outputs it to other devices for use; the position information in the status information is sent to the antenna direction calculation module, and the satellite position calculated by the orbit extrapolation module is combined to calculate the pitch angle and azimuth angle of the satellite relative to the ground antenna at this time; the attitude information in the status information is sent to the antenna direction correction module to correct the direction angle calculated by the antenna direction calculation module, and the corrected angle is sent to the antenna end through the communication module to control the beam pointing of the multi-beam phased array antenna. The satellite orbit data required by the orbit extrapolation module of the control end is input from the outside through a file. The satellite screening module of the control end will combine the predicted satellite position given by the orbit extrapolation module, and when the number of satellites is too many, select the satellite that can establish a connection with the antenna for the longest time to receive data, and send the selected satellite number to the antenna end to set the corresponding beam parameters. The system principle diagram of this application is shown in the figure below. Figure 1 shown.

[0021] The multi-beam hemispherical phased array antenna at the antenna end installs antenna elements on the spherical surface, which can synthesize a multi-beam antenna to receive satellite signals, and the internal beam controller controls the direction of each beam of the antenna according to the control instructions sent by the control end, so as to align with the satellite. The control and processing part in this application processes the signals received by each beam respectively, and can independently control the direction of the antenna signal beam and process different satellite signals. The received satellite signal is filtered and processed at the baseband, and then packaged and framed into data frames and transmitted to the communication module. The GPS equipped with the antenna is used to locate the antenna, output the longitude, latitude and altitude of the antenna location, and after transmission, it is used as the input of the control end antenna direction calculation module to calculate the angular relationship between the antenna and the satellite; the angular velocity output by the three-axis gyroscope is integrated to obtain the heading angle, pitch angle and roll angle of the phased array antenna, and after transmission, it is used as the input of the control end antenna direction correction module to correct the antenna pointing direction. The GPS and gyroscope data are packaged and framed into status frames and transmitted to the communication module.

[0022] The communication module on the control side receives data and status frames from the antenna side, parses the data into satellite data, position data, and attitude data based on the frame format, and distributes it to the corresponding modules on the control side for processing. The communication module also receives control instructions calculated by other modules, including antenna attitude angles and selected satellites to be tracked, and sends them to the communication module on the antenna side.

[0023] The control end signal processing module analyzes the satellite data transmitted by the communication module and transmits the data as the output of the receiving system to other equipment.

[0024] The orbit extrapolation module monitors the input folder for new orbit files in real time. Upon detecting changes, it reads the file parameters and updates the orbit model within the control terminal. External files are input in XML format and contain the orbit semi-major axis, orbital eccentricity, orbital inclination, right ascension of the ascending node, argument of perigee, mean anomaly, and the corresponding epoch time. The orbit extrapolation model uses the HPOP model to extrapolate the satellite orbit within a specified timeframe, outputting the satellite's position (x1, y1, z1) in the geocentric coordinate system at the specified time.

[0025] The antenna direction calculation module is used to calculate the elevation and azimuth of the satellite relative to the ground antenna. After the GPS obtains the latitude, longitude and altitude of the ground antenna, the calculation module converts the antenna position to the geocentric coordinate system (x2, y2, z2). Based on the positional relationship between the satellite and the ground antenna in the coordinate system, the azimuth α and the elevation β based on the true north direction can be obtained. The schematic diagram is as follows Figure 2 As shown, the calculation formula is

[0026]

[0027]

[0028] In addition to being placed on fixed platforms, ground antennas may also be placed on mobile devices such as vehicles and ships. The antenna's attitude will change as the platform moves and tilts, so the pitch angle and azimuth angle calculated by the antenna direction calculation module need to be corrected according to the antenna's current heading angle ψ, pitch angle θ, and roll angle φ. Convert the antenna coordinates to geocentric coordinates, and the three attitude angles are as follows: Figure 2 As shown, the calculation process of the correction formula is:

[0029] 1) Correction formula for yaw angle to antenna direction angle

[0030] α ψ =α-ψ

[0031] β ψ =β

[0032] 2) Correction formula for yaw angle and roll angle to antenna direction angle

[0033]

[0034] β ψφ =arccos(-sinφcosβ ψ sinα ψ +cosφcosβ ψ )

[0035] 3) Yaw angle, roll angle, pitch angle correction formula for antenna direction angle

[0036]

[0037] β′=β ψφθ =arccos(sinθsinβ ψφ cosα ψφ +cosθcosβ ψφ )

[0038] The α' and β' finally obtained are the azimuth and elevation angles of the final antenna.

[0039] In order to obtain better signal gain, the multi-beam antenna has a limited number of beams. When multiple satellites are within the receiving range of the antenna and exceed the number of beams, the satellite screening module needs to screen the satellites in combination with the satellite extrapolation orbit. The satellite antenna receiving system proposed in this application selects satellites based on the principle that the longer the tracking time, the higher the priority. The orbit extrapolation module can extrapolate the positions of all satellites within the receiving range within a certain period of time, and the satellite screening module will continuously calculate the pitch angles of these positions relative to the antenna, and record the absolute time when the pitch angle is lower than the lowest elevation angle of the antenna. Sort the satellite numbers from late to early according to the absolute time when the pitch angle is equal to the lowest elevation angle of the antenna, and select the top-ranked satellites for tracking based on the maximum number of beams of the multi-beam antenna.

[0040] The above description of the embodiments is intended to facilitate understanding and application of the present application by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without expending any creative effort. Therefore, the present application is not limited to the embodiments described herein, and improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A ground-based automatic tracking and receiving system for a low-orbit satellite constellation, characterized in that: The system includes an antenna end and a control end; The antenna end is a hemispherical multi-beam phased array antenna, wherein the hemispherical multi-beam phased array antenna is equipped with antenna elements on a spherical surface to synthesize a multi-beam antenna to receive satellite signals, and an internal beam controller controls the direction of each beam of the antenna according to a control instruction sent by the control end, thereby aligning with the satellite; The control terminal includes a communication module, an orbit extrapolation module, an antenna direction calculation module, an antenna direction correction module, a satellite screening module and a data processing module; The control end uses an orbit extrapolation model to predict the satellite position and calculates the antenna elevation angle and azimuth angle based on the antenna position, including the following steps: The orbit extrapolation model uses the HPOP model to extrapolate the satellite orbit within a specified time and outputs the position of the satellite in the geocentric coordinate system at the specified time (x1, y1, z1); After GPS obtains the latitude, longitude and altitude of the antenna end, the calculation module converts the antenna position to the geocentric coordinate system (x2, y2, z2); The azimuth angle α and the elevation angle β based on the true north direction are obtained according to the position relationship between the satellite and the antenna in the coordinate system according to the following formula: as well as The angle is corrected according to the satellite attitude, and the corrected angle is sent to the antenna end to control the beam pointing of the multi-beam phased array antenna, including the following steps: The pitch angle and azimuth angle calculated by the antenna direction calculation module are corrected according to the antenna's current heading angle ψ, pitch angle θ, and roll angle φ, where: The correction formula of heading angle to antenna direction angle is: a ψ =a-ψ β ψ ＝β； The correction formula of heading angle and roll angle to antenna direction angle is: b ψφ =arccos(-sinφcosβ ψ Sinai ψ +cosφcosβ ψ ); The correction formula for the heading angle, roll angle, and pitch angle to the antenna direction angle is: β'=β ψφθ =arccos(sinθsinβ) ψφ thing ψφ +cosθcosβ ψφ ), The final obtained α' and β' are the azimuth and elevation angles of the final antenna; The orbit extrapolation module extrapolates the positions of all satellites within the reception range over a certain period of time, and the satellite screening module continuously calculates the pitch angles of these positions relative to the antenna. When the pitch angle falls below the antenna's minimum elevation angle, the absolute time at that moment is recorded, and the satellite numbers are sorted from latest to earliest according to the absolute time. Based on the maximum number of beams of the multi-beam antenna, the top-ranked satellites are selected for tracking.

2. The ground automatic tracking and receiving system for low-orbit satellite constellations according to claim 1, characterized in that: The antenna end is equipped with a multi-channel signal processing module.

3. The ground automatic tracking and receiving system for low-orbit satellite constellations according to claim 1, wherein: The antenna end is also equipped with a three-axis gyroscope and a GPS module.

Images