CDM-based on-orbit calibration method for downlink phased-array antenna of low-orbit communication satellite

Abstract

The invention relates to a low-orbit communication satellite downlink phased-array antenna in-orbit calibration method based on CDM, and belongs to the technical field of satellite testing. According to the method, pointing measurement and calibration of a downlink phased-array antenna of a low-orbit communication satellite are taken as input, and measurement and calibration of beam pointing of the downlink phased-array antenna are realized through test and data processing of a plurality of beam EIRP of the downlink phased-array antenna. The method has the functions of calibration signal generation, beam EIRP test, beam stereo directional diagram reconstruction, pointing deviation measurement and beam pointing adjustment. Simulation experiments show that the calibration method designed by the invention can effectively reduce the beam pointing deviation of the downlink phased-array antenna of the low-orbit communication satellite.

Description

Technical Field

[0001] The invention relates to an on-orbit calibration method for a downlink phased array antenna of a low-orbit communication satellite based on CDM, which is suitable for the pointing measurement and calibration of the downlink phased array antenna of a low-orbit communication satellite and belongs to the technical field of satellite testing. Background Art

[0002] Compared with high-orbit satellites, low-orbit satellite constellations have obvious advantages in launch costs and global coverage, and have the characteristics of strong anti-destruction, low transmission delay, low link attenuation, and high communication rate. Therefore, the low-orbit satellite network system characterized by low-orbit giant constellations is showing a booming development trend around the world.

[0003] SpaceX's "Starlink" project has initially formed a global satellite communication network, providing cheap and fast broadband Internet services to users around the world. In addition, the Internet constellation plans of OneWeb of the United Kingdom, Telesat of Canada, O3b constellation of multinational enterprise SES, Boeing, Samsung, etc. are also being actively promoted.

[0004] As low-orbit satellite constellations enter the large-scale deployment stage, satellites need to be mass-produced and launched, and the ground test system cannot guarantee that the test content covers all satellites. In addition, due to the complex space environment of low-orbit satellites, satellites will be affected by factors such as the atmospheric environment, particle radiation and electromagnetic radiation environment, and geomagnetic field environment in space, which may cause failures in on-board antennas. In order to ensure the quality of satellite on-orbit services, it is necessary to conduct additional on-orbit testing and calibration of the satellite antenna’s antenna pointing to improve the beam pointing accuracy and meet the system’s use requirements. If the satellite’s uplink and downlink phased array antennas are independent stand-alone units, calibration tests for uplink and downlink are required separately.

[0005] Calibration test can be divided into downlink calibration and uplink calibration. Downlink beam calibration is usually carried out by the signal gateway or satellite transmitting calibration signals, and the beam calibration receiving station is set up on the ground. The receiving station judges the energy of different beam calibration signals to obtain the antenna pointing error; uplink beam calibration is carried out by the ground beam calibration station transmitting calibration signals, and the satellite or signal gateway performs energy estimation and field strength comparison to obtain the antenna pointing error. The Thuraya system adopts the uplink calibration scheme. The Aces satellite system uses both calibration schemes. Summary of the invention

[0006] The present invention aims at the problem of pointing measurement and calibration of the downlink phased array antenna of low-orbit communication satellite, and realizes the measurement and calibration of its beam pointing by testing and processing the EIRP of multiple beams of the downlink phased array antenna. Simulation experiments show that the calibration method designed by the present invention can effectively reduce the beam pointing deviation of the downlink phased array antenna of low-orbit communication satellite.

[0007] The calculation scheme adopted by the present invention is:

[0008] A method for in-orbit calibration of a downlink phased array antenna of a low-orbit communication satellite based on CDM (code division multiple access), comprising the following steps:

[0009] Step 1: The satellite transmits calibration signals of equal power in multiple beams of the downlink phased array antenna and transmits reference signals on the omnidirectional antenna;

[0010] Step 2: In the test window of the low-orbit satellite, the ground calibration station receives the calibration signal and the reference signal, and processes them to obtain the measurement result of the satellite EIRP (equivalent isotropic radiated power) value;

[0011] Step 3: The ground data processing system receives and stores the measurement data of multiple calibration stations and multiple test windows, classifies and processes the data, and obtains the stereoscopic pattern data of multiple beams;

[0012] Step 4: The ground data processing system normalizes the stereoscopic pattern data of multiple beams to obtain the measured value of the satellite downlink phased array antenna pointing, and compares and analyzes it with the design value to form an analysis result;

[0013] Step 5: The ground data processing system determines the beam deviation based on the analysis results, formulates an avoidance, adjustment or processing strategy based on information including the satellite's orbit, attitude and end-user communication quality, and remotely controls the execution on the satellite through the measurement and control signal;

[0014] Step 6: During the test window of the low-orbit satellite, the ground calibration station continues to measure the beam pointing of the adjusted satellite downlink phased array antenna and corrects the pointing deviation in an iterative manner until the beam pointing of the satellite downlink phased array antenna meets the system requirements.

[0015] Further: The specific process of step 1 is as follows:

[0016] Step 101: The satellite transmits calibration signals of equal power in multiple beams of the downlink phased array antenna. The calibration signals are narrowband signals of orthogonal code division multiple access, and include satellite number, position, attitude, antenna installation matrix and time information.

[0017] Step 102: The satellite transmits a reference signal through an omnidirectional antenna, where the reference signal is a single carrier signal.

[0018] Further: The specific process of step 2 is as follows:

[0019] Step 201: In the test window of the low-orbit satellite, the ground calibration station equipment receives the calibration signal and the reference signal, obtains the power value received from different beams of the satellite downlink phased array antenna and the power value of the reference signal, and obtains the EIRP values ​​of different beams of the satellite downlink phased array antenna through differential calculation;

[0020] Step 202: The ground calibration station equipment analyzes the satellite number, position, attitude, antenna installation matrix, time and other information in the calibration signal;

[0021] Step 203: The ground calibration station equipment calculates the azimuth and elevation angles of the ground calibration station in the satellite antenna coordinate system according to the geographical location of the calibration station, the satellite position, attitude, and antenna installation matrix;

[0022] Step 204: The ground calibration station equipment calculates the timestamp corresponding to each sampling point by interpolation according to the satellite time information;

[0023] Step 205: The ground calibration station equipment timestamps the satellite number, the numbers of different beams of the satellite downlink phased array antenna, the EIRP value, and the azimuth and elevation angles of the ground calibration station in the satellite antenna coordinate system, and transmits them to the ground data processing system.

[0024] Further: The specific process of step 3 is as follows:

[0025] Step 301: The ground data processing system receives and stores measurement data of multiple calibration stations and multiple test windows;

[0026] Step 302: The ground data processing system classifies the measurement data according to the satellite number and the beam number;

[0027] Step 303: The ground data processing system processes the classified data to obtain three-dimensional directional pattern data of multiple beams.

[0028] Compared with the background technology, the present invention has the following advantages:

[0029] 1. The calibration signals transmitted by the satellite in multiple beams of the downlink phased array antenna adopt the CDM multiple access method, which can eliminate the influence of the calibration station antenna tracking accuracy, the in-band fluctuation of the transmission channel gain and the time-varying characteristics on the measurement accuracy.

[0030] 2. The calibration signal transmitted by the satellite in multiple beams of the downlink phased array antenna contains information such as satellite number, position, attitude, antenna installation matrix and time, which makes it easy to realize coordinate system conversion and satellite-ground synchronization, and is suitable for the high dynamic characteristics of satellites.

[0031] 3. During the transmission process, the calibration signal will be affected by the space environment such as rainfall and atmosphere. In order to reduce the impact of the space environment on the measurement data, the signal of the omnidirectional antenna is used as the reference signal to calibrate the measurement data. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a framework flow chart of the method designed by the present invention;

[0033] Figure 2 It is a schematic diagram of the system composition of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings.

[0035] Reference Figure 1 and Figure 2 , a CDM-based on-orbit calibration method for a downlink phased array antenna of a low-orbit communication satellite, comprising the following steps:

[0036] Step 1: Figure 2 The satellite transmits calibration signals of equal power in multiple beams of the downlink phased array antenna and transmits reference signals in the omnidirectional antenna;

[0037] Wherein, step 1 includes the following process:

[0038] Step 101: The satellite transmits calibration signals of equal power in multiple beams of the downlink phased array antenna. The calibration signals are narrowband signals of orthogonal code division multiple access, and contain information such as satellite number, position, attitude, antenna installation matrix, and time.

[0039] Step 102: In order to reduce the impact of the space environment on the measurement data, the satellite transmits a reference signal through an omnidirectional antenna, and the reference signal is a single carrier signal.

[0040] Step 2: During the test window of the low-orbit satellite, Figure 2 The ground calibration station receives the calibration signal and the reference signal and processes them to obtain the measurement result of the satellite EIRP value;

[0041] Wherein, step 2 includes the following process:

[0042] Step 201: In the test window of the low-orbit satellite, the ground calibration station equipment receives the calibration signal and the reference signal, obtains the power value received from different beams of the satellite downlink phased array antenna and the power value of the reference signal, and obtains the EIRP values ​​of different beams of the satellite downlink phased array antenna through differential calculation;

[0043] Step 202: The ground calibration station equipment analyzes the satellite number, position, attitude, antenna installation matrix, time and other information in the calibration signal;

[0044] Step 203: The ground calibration station equipment calculates the azimuth and elevation angles of the ground calibration station in the satellite antenna coordinate system according to the geographical location of the calibration station, the satellite position, attitude, and antenna installation matrix;

[0045] Step 204: The ground calibration station equipment calculates the timestamp corresponding to each sampling point by interpolation according to the satellite time information;

[0046] Step 205: The ground calibration station equipment timestamps the satellite number, the numbers of different beams of the satellite downlink phased array antenna, the EIRP value, and the azimuth and elevation angles of the ground calibration station in the satellite antenna coordinate system, and transmits them to Figure 2 Ground data processing system in.

[0047] Step 3: The ground data processing system receives and stores the measurement data of multiple calibration stations and multiple test windows, classifies and processes the data, and obtains the stereoscopic pattern data of multiple beams;

[0048] Wherein, step 3 includes the following process:

[0049] Step 301: The ground data processing system receives and stores measurement data of multiple calibration stations and multiple test windows;

[0050] Step 302: The ground data processing system classifies the measurement data according to the satellite number and the beam number;

[0051] Step 303: The ground data processing system processes the classified data to obtain three-dimensional directional pattern data of multiple beams.

[0052] Step 4: The ground data processing system normalizes the stereoscopic pattern data of multiple beams to obtain the measured value of the satellite downlink phased array antenna pointing, and compares and analyzes it with the design value to form an analysis result;

[0053] Step 5: Figure 2 The ground data processing system determines the beam deviation based on the analysis results, formulates avoidance, adjustment or processing strategies based on the satellite's orbit, attitude and end-user communication quality information, and remotely controls the execution on the satellite through measurement and control signals.

[0054] Step 6: During the test window of the low-orbit satellite, the ground calibration station continues to measure the beam pointing of the adjusted satellite downlink phased array antenna and corrects the pointing deviation in an iterative manner until the beam pointing of the satellite downlink phased array antenna meets the system requirements.

Claims

1. A CDM-based on-orbit calibration method for a downlink phased array antenna of a low-orbit communication satellite, characterized in that: The steps include: Step 1: The satellite transmits calibration signals of equal power in multiple beams of the downlink phased array antenna and transmits reference signals on the omnidirectional antenna; Step 2: In the test window of the low-orbit satellite, the ground calibration station receives the calibration signal and the reference signal, and processes them to obtain the measurement result of the satellite EIRP value; Step 3: The ground data processing system receives and stores the measurement data of multiple calibration stations and multiple test windows, classifies and processes the data, and obtains the stereoscopic pattern data of multiple beams; Step 4: The ground data processing system normalizes the stereoscopic pattern data of multiple beams to obtain the measured value of the satellite downlink phased array antenna pointing, and compares and analyzes it with the design value to form an analysis result; Step 5: The ground data processing system determines the beam deviation based on the analysis results, formulates an avoidance, adjustment or processing strategy based on information including the satellite's orbit, attitude and end-user communication quality, and remotely controls the execution on the satellite through the measurement and control signal; Step 6: During the test window of the low-orbit satellite, the ground calibration station continues to measure the beam pointing of the adjusted satellite downlink phased array antenna and corrects the pointing deviation in an iterative manner until the beam pointing of the satellite downlink phased array antenna meets the system requirements.

2. According to claim 1, a CDM-based on-orbit calibration method for a low-orbit communication satellite downlink phased array antenna, characterized in that: The specific process of step 1 is as follows: Step 101: The satellite transmits calibration signals of equal power in multiple beams of the downlink phased array antenna. The calibration signals are narrowband signals of orthogonal code division multiple access, and include satellite number, position, attitude, antenna installation matrix and time information. Step 102: The satellite transmits a reference signal through an omnidirectional antenna, where the reference signal is a single carrier signal.

3. According to claim 1, a CDM-based on-orbit calibration method for a low-orbit communication satellite downlink phased array antenna, characterized in that: The specific process of step 2 is as follows: Step 201: In the test window of the low-orbit satellite, the ground calibration station equipment receives the calibration signal and the reference signal, obtains the power value received from different beams of the satellite downlink phased array antenna and the power value of the reference signal, and obtains the EIRP values ​​of different beams of the satellite downlink phased array antenna through differential calculation; Step 202: The ground calibration station equipment analyzes the satellite number, position, attitude, antenna installation matrix, time and other information in the calibration signal; Step 203: The ground calibration station equipment calculates the azimuth and elevation angles of the ground calibration station in the satellite antenna coordinate system according to the geographical location of the calibration station, the satellite position, attitude, and antenna installation matrix; Step 204: The ground calibration station equipment calculates the timestamp corresponding to each sampling point by interpolation according to the satellite time information; Step 205: The ground calibration station equipment timestamps the satellite number, the numbers of different beams of the satellite downlink phased array antenna, the EIRP value, and the azimuth and elevation angles of the ground calibration station in the satellite antenna coordinate system, and transmits them to the ground data processing system.

4. The on-orbit calibration method for a downlink phased array antenna of a low-orbit communication satellite based on CDM according to claim 1 is characterized in that: The specific process of step 3 is as follows: Step 301: The ground data processing system receives and stores measurement data of multiple calibration stations and multiple test windows; Step 302: The ground data processing system classifies the measurement data according to the satellite number and the beam number; Step 303: The ground data processing system processes the classified data to obtain three-dimensional directional pattern data of multiple beams.

Images