A method for determining the initial attitude, orientation and position of Ku-band phased array antenna

Abstract

The present invention relates to a method for determining the initial attitude, azimuth, and position of a Ku-band phased array antenna. This method utilizes direction-finding information from direct television broadcast satellite Ku-band signals to compensate for and correct multi-sensor measurement results. Ultimately, the method uses a fused positioning equation to obtain initial attitude, azimuth, and rough position information for a phased array antenna positioning terminal. This method utilizes existing direct television broadcast satellites as reference satellites and their broadcast Ku signals as reference signals. This allows Ku-band phased array antennas to directly receive signals without requiring the additional configuration of multiple frequency bands. This significantly reduces hardware platform requirements compared to existing methods that utilize multiple frequency-point combination antennas to receive satellite signals from different frequency bands.

Description

Technical Field

[0001] The present invention relates to the technical field of mobile satellite communications, and in particular to a method for determining the initial attitude, azimuth, and position of a Ku-band phased array antenna, which is applied to calibrating the initial attitude and azimuth of a phased array antenna for satellite tracking and sampling in navigation and positioning. Background Art

[0002] As GNSS applications deepen, its inherent shortcomings are becoming increasingly apparent. These include electromagnetic signal interference and difficulty achieving positioning under geographically obstructed conditions. The inherent limitations and vulnerabilities of satellite navigation systems pose serious security risks. Leveraging communication satellite signals for navigation and positioning can enable PNT services independent of GNSS systems. High-throughput communication satellite signals, such as those from Starlink and Oneweb, operate in the Ku band. Their transmit and receive signals rely on precise tracking and sampling by phased array antennas. This requires initial attitude and azimuth calibration and position estimation to ensure successful satellite tracking.

[0003] The currently commonly used initial calibration method for mobile communication antennas is to obtain antenna position information using the navigation constellation and antenna attitude information using inertial sensors while accurately tracking satellites. By demodulating the beacon signal of the target communication satellite or navigation satellite, the antenna's own attitude and azimuth information can be inferred under the condition that the real-time position of the satellite is known, thus completing the initial alignment. This method has the following disadvantages: (1) For non-cooperative users, the signals broadcast by the low-orbit communication giant constellation cannot be demodulated. Even in areas without cooperative users, the pilot signals broadcast by satellites do not contain valid information, making it impossible to distinguish the different pilot signals broadcast by each satellite. This results in the initial attitude and azimuth calibration process of the phased array antenna not being able to rely on the target constellation to be tracked. (2) When the satellite navigation constellation signal is interfered with and unavailable, the antenna position information cannot be obtained, and thus the pitch angle and azimuth angle of the target satellite and the antenna line of sight vector in the antenna carrier coordinate system cannot be calculated. At the same time, the initial attitude and azimuth calibration of the phased array antenna cannot be completed according to the navigation constellation; (3) The spatial position of the low-orbit communication satellite changes rapidly over time. Under the condition that the ephemeris parameters cannot be obtained, the spatial position of the low-orbit communication satellite cannot be accurately calculated, making the method based on the target satellite reverse calculation completely invalid; (4) The current low-orbit communication giant constellation signal frequency is in the Ku band and other high frequency bands, and the navigation satellite frequency band is in the L band and S band. If the Ku band phased array tracking sampling equipment needs to perform airspace scanning on the navigation satellite, it needs to be equipped with an L band or S band antenna, and the overall device is redundant.

[0004] In summary, existing phased array antenna initial spatial state calibration technology requires first using navigation satellites for antenna positioning. Then, after calculating the communication satellite's spatial position based on ephemeris parameters, antenna beam alignment can be performed. Finally, cooperative demodulation and processing of the communication satellite signals are performed to complete direction finding of the communication satellite before the antenna initial spatial state calibration can be achieved. Existing technology cannot achieve initial antenna spatial state calibration if navigation satellites are unavailable, ephemeris parameters cannot be obtained in a timely manner, or the calibration communication satellite signals cannot be processed collaboratively. Furthermore, because communication satellite signals and navigation satellite signals reside in different frequency bands, the antenna design requires integrating multiple antennas with different frequency bands, resulting in complex and costly equipment.

[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art. Summary of the Invention

[0006] The present invention solves the problem of overcoming various requirements and limitations of the prior art, such as the need for navigation satellite positioning, communication satellite ephemeris parameters, communication satellite signal cooperative demodulation capabilities, and multi-band integrated antennas, and provides a method for determining the initial attitude, azimuth, and position of a Ku-band phased array antenna. The method has the advantages of requiring no navigation satellite positioning, no communication satellite calibration, and capable of completing attitude, azimuth, and position calculation using a single Ku-band antenna.

[0007] Technical solution of the present invention:

[0008] A method for determining the initial attitude, orientation, and position of a Ku-band phased array antenna is characterized by comprising the following steps:

[0009] Step 1: Use the magnetic sensor readings in the northeast celestial coordinate system to perform coordinate conversion to obtain the azimuth information of the current phased array antenna in the northeast celestial coordinate system; use the inertial sensor three-axis accelerometer to estimate the horizontal attitude of the phased array antenna, and obtain the off-axis angular deviation angle and azimuth angular deviation angle of the array normal beam in the northeast celestial coordinate system of the phased array antenna carrier coordinate system; use the air pressure sensor to estimate the altitude of the phased array antenna; simultaneously use the phased array antenna to scan the entire airspace and sample signals, and there is a temporal correspondence between the phased array antenna beam direction and the signal sampling data stream;

[0010] Step 2: Perform multi-pass filtering on the data stream of the signal sampling to filter out interference signals, obtain a filtered sampling signal, and perform signal processing such as nonlinear processing or local sequence correlation to extract signal characteristics of the sampling signal that change with the phased array antenna beam direction;

[0011] Step 3: Based on the changes in the signal characteristics described in step 2, a feature recognition algorithm is used to identify and determine the energy of the sampled signal from the time domain characteristics, frequency domain characteristics, and modulation characteristics, thereby completing the detection of the live TV satellite signal, thereby achieving direction finding of each live TV satellite signal, and obtaining the direction finding information of each live TV satellite in the phased array antenna carrier coordinate system, wherein the direction finding information includes azimuth information and pitch angle information;

[0012] Step 4: Use the direction-finding information of no less than two live TV satellites and the known fixed airspace positions of the live TV satellites as observation quantities, and the spatial information of the phased array antenna measured by the three types of sensors as the initial state to construct a fusion positioning equation, where the spatial information of the phased array antenna measured by the three types of sensors is the azimuth information of the current phased array antenna in the northeast celestial coordinate system measured by the magnetic sensor, the off-axis angular deviation angle and azimuth deviation angle of the array normal beam in the northeast celestial coordinate system of the phased array antenna carrier measured by the inertial sensor, and the altitude of the phased array antenna measured by the pressure sensor; use the fusion positioning equation to calculate the initial attitude and azimuth information of the phased array antenna in the northeast celestial coordinate system and the rough position information of the phased array antenna, and at the same time obtain the measurement corrections for the magnetic sensor, the three-axis accelerometer and the pressure sensor.

[0013] In particular, in the step 2, the passband of the multi-passband filter only includes the entire signal frequency range under the frequency points corresponding to each program of the live TV satellite, and after filtering, the signal of the live TV satellite signal band with periodic bursts and continuous broadcasts is obtained.

[0014] In particular, in step 2, the signal processing method is performed in one or both of the following modes:

[0015] (1) Performing second-, fourth-, and eighth-order nonlinear processing on the filtered sampled signal to eliminate the modulated bipolar pseudo code and data information stream in the signal, and obtaining single carrier components of second, fourth, and eighth frequencies, respectively, from which signal characteristics that change with the phased array antenna beam direction are extracted;

[0016] (2) Performing local sequence correlation on the filtered sampled signal to complete signal capture and extract signal features that change with the phased array antenna beam direction. The local sequence correlation includes the local spread spectrum code sequence under spread spectrum modulation and the local training symbol under OFDM system.

[0017] In particular, in the step 2, the signal characteristics that vary with the phased array antenna beam direction include time domain characteristics, frequency domain characteristics, and modulation characteristics;

[0018] (1) Time domain characteristics refer to:

[0019] The filtered sampled signal is averaged within the coherence time;

[0020] The standard deviation of the filtered sampled signal within the coherence time;

[0021] (2) Frequency domain characteristics refer to:

[0022] Power spectral density distribution of the filtered sampled signal;

[0023] (3) Modulation characteristics refer to:

[0024] Different modulation modes contained in the filtered sampled signal;

[0025] The local spreading code and local training symbol type used by the filtered sampled signal;

[0026] Only the filtered sampling signals that simultaneously meet the time domain characteristics, frequency domain characteristics and modulation characteristics are considered to contain live TV satellite signals and can be extracted.

[0027] In particular, in step three, the feature recognition algorithm identifies and determines the energy of the sampled signal from the time domain features, frequency domain features, and modulation features. The process is as follows:

[0028] In terms of time domain characteristics, the sampling signal contains both continuous broadcast signals and periodic burst signals, and the time interval of the burst signals is consistent with the burst signal of the live TV satellite. In terms of frequency domain characteristics, the sampling signal exists within each predetermined frequency band and the signal Doppler is zero. In terms of modulation characteristics, the sampling signal modulation methods include PSK modulation and OFDM modulation, and can match the local spreading code and local training symbols.

[0029] After completing the sampling signal identification, energy judgment is performed, and the relationship between the signal strength of each live TV satellite and the full airspace scan is counted. The beam direction corresponding to the maximum signal strength of each live TV satellite is used to complete the detection of the live TV satellite signal, thereby realizing the direction finding of each live TV satellite signal and obtaining the direction finding information of each live TV satellite in the phased array antenna carrier coordinate system.

[0030] In particular, in step 4, the fusion positioning equation is implemented as follows:

[0031] Assume the position of the phased array antenna is There are four unknowns in the equation. The following linearization formula is constructed and solved based on the least squares method:

[0032] .

[0033] Where, represents the longitude of the phased array antenna position, represents the latitude of the phased array antenna position, represents the initial azimuth angle of the phased array antenna beam, Represents the initial elevation angle of the phased array antenna beam; known quantities include: represents the actual observation azimuth of k live TV satellites, Represents the actual observed elevation angle of the kth live TV satellite.

[0034] The advantages of the present invention compared with the prior art are:

[0035] (1) The present invention uses a live TV satellite as a calibration satellite instead of the existing technology that uses navigation satellite positioning. It can not only complete the determination of the initial spatial state of the phased array antenna in an environment where the navigation satellite is unavailable, but also avoid the need for additional integrated navigation satellite antennas. At the same time, the live TV satellite has the characteristic of fixed spatial position, and a relatively accurate satellite spatial position can be obtained without real-time updating of ephemeris parameters. The existing technology uses low-orbit communication satellites as calibration satellites. The satellites are in a high-speed motion state, and the ephemeris parameters need to be continuously updated to solve the satellite spatial position.

[0036] At the same time, the live TV satellite signals processed by the overall technical solution have the characteristics of a fixed system and distinct features, and the signal processing process is simple and reliable. However, the low-orbit communication satellite signals processed by the existing technology have a complex system and changeable content. They are difficult to use and prone to failure when their signal modulation information is unknown.

[0037] Finally, the overall technical solution only needs to use the direction-finding results of the live TV satellite and the fused positioning equation to simultaneously solve the initial position and initial spatial state of the phased array antenna. The required observation quantity is small, the calculation is simple and fast, and the system robustness is high. The existing technology requires the known position of the phased array antenna to complete the initial spatial state determination with the help of communication satellites.

[0038] (2) The frequency band of the multi-band filter in the present invention is the Ku band. The Ku band phased array antenna is used to receive the Ku band signal of the low-orbit communication giant constellation in the same frequency band. At the same time, it can receive the Ku band signal of the live TV satellite used as a position reference. There is no need to add additional phased array antennas of other frequency bands to assist in the initial calibration, thereby reducing the requirements for the hardware platform.

[0039] (3) The reference signal used for phased array calibration in the present invention is the Ku-band signal of the live television satellite, which contains a PSK signal and an OFDM signal. The signal processing is completed using an innovative signal processing method, which avoids the problem of being unable to receive the signal when the navigation constellation is interfered with, and also avoids the problem of being unable to use the satellite for initial phased array calibration when the target satellite to be tracked only broadcasts a non-cooperative signal with no valid information.

[0040] (4) The present invention extracts the time domain, frequency domain and modulation domain features of the Ku-band signal of the live TV satellite, thereby avoiding the problem that the satellite cannot be used for initial calibration of the phased array when the target satellite to be tracked only broadcasts a non-cooperative signal without valid information.

[0041] (5) The present invention uses a feature recognition algorithm to identify and determine the energy of the sampled signal based on time domain features, frequency domain features, and modulation features. While avoiding demodulation and resolution of navigation signals, it also avoids demodulation of low-orbit communication satellite signals, thereby improving processing efficiency.

[0042] (6) The present invention uses a fusion positioning equation to complete the calculation of the initial position and spatial state of the phased array antenna, and does not rely on the navigation constellation to provide the initial position of the phased array antenna. Under the background of positioning requirements, the initial attitude and azimuth calibration of the phased array antenna can be completed by relying only on multiple sensors and live TV satellites, and the preliminary position estimation can be completed at the same time, which has strong practicality and usability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are only some embodiments of the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0044] Figure 1 Flowchart for implementing the method of the embodiment of the present invention;

[0045] Figure 2 Schematic diagram of the signal processing and feature extraction method in an embodiment of the present invention:

[0046] Figure 3 This is a flowchart for implementing the feature recognition algorithm, energy judgment algorithm, and positioning solution in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] like Figure 1As shown, the embodiment of the present invention uses the direction-finding information compensation of the Ku-band signal of the direct television satellite to correct the multi-sensor measurement results, and finally uses the phased array antenna positioning terminal initial attitude and azimuth information and rough position information obtained by the fusion positioning equation, which specifically includes the following steps:

[0049] Step 1: Use the magnetic sensor readings in the northeast celestial coordinate system to perform coordinate conversion to obtain the azimuth information of the current phased array antenna in the northeast celestial coordinate system; use the inertial sensor three-axis accelerometer to estimate the horizontal attitude of the phased array antenna, and obtain the off-axis angular deviation angle and azimuth angular deviation angle of the array normal beam in the northeast celestial coordinate system of the phased array antenna carrier coordinate system; use the air pressure sensor to estimate the altitude of the phased array antenna; simultaneously use the phased array antenna to scan the entire airspace and sample signals, and there is a temporal correspondence between the phased array antenna beam direction recording and the signal sampling data stream;

[0050] In particular, the above step 1 is specifically implemented as follows:

[0051] (11) Collect data from the magnetic sensor in all horizontal directions, perform weighted averaging of the magnetic sensor readings over the entire week, and simultaneously correct the initial bias of the magnetometer while obtaining the azimuth information of the current phased array antenna in the northeast sky coordinate system;

[0052] (12) The accelerometer output in the inertial sensor is smoothed and filtered to reduce the influence of noise. The acceleration triaxial output measurement value is the component of gravity acceleration in three directions, which reflects the attitude information of the phased array antenna. The azimuth deviation angle of the array normal beam in the carrier coordinate system of the phased array antenna in the northeast sky coordinate system is obtained by calculation. and off-axis angle , the calculation formula is as follows:

[0053] ;

[0054] Where, is the local acceleration of gravity, , 、 and Represent the x-axis, y-axis, and z-axis accelerometer measurement results respectively;

[0055] (13) Obtain the air pressure measurement value from the air pressure sensor, process the air pressure measurement value through smoothing filtering, reduce the measurement error of the air pressure sensor, and finally obtain the estimation of the altitude of the phased array antenna;

[0056] (14) When using a phased array antenna to scan the entire airspace, it is necessary to mesh the 0°-90° elevation angle and the 0°-360° azimuth angle according to the phased array antenna beam width, and complete the full airspace search of the semi-celestial sphere by traversing each grid. When the phased array antenna beam points to each grid, the signal is synchronously sampled. The phased array antenna beam direction and the signal sampling data stream have a temporal correspondence, ultimately achieving full airspace scanning and signal sampling by the phased array antenna.

[0057] In step one, magnetic, inertial, and barometric sensors are used to estimate the phased array antenna's azimuth angle, the off-axis and azimuth deviation angles of the array's normal beam in the carrier coordinate system, and the altitude. These parameters are not directly used to estimate the phased array antenna's heading attitude. Instead, they serve as initial conditions for the unknown quantities in the subsequent positioning solution equations, resulting in rapid convergence and low divergence. The measurement accuracy of magnetic and inertial sensors is limited, and existing technologies that directly use their measurement results as the phased array antenna's heading attitude estimate suffer from large errors.

[0058] Step 2: Perform multi-pass filtering on the data stream of the signal sampling to remove the interference signal, obtain the filtered sampling signal, and perform signal processing such as nonlinear processing or local sequence correlation to extract the signal characteristics of the sampling signal that changes with the phased array antenna beam direction;

[0059] like Figure 2 As shown, in particular, the above step 2 is specifically implemented as follows:

[0060] (21) The sampled signal is subjected to multi-passband filtering. The passband of the multi-passband filtering only includes the entire signal frequency range at the frequency points corresponding to each program of the live TV satellite, and the other frequency ranges are stopbands. After filtering, the signal of the periodic burst and continuous broadcast live TV satellite signal band is obtained.

[0061] (22) The signal processing method adopts one of the following two modes:

[0062] Performing second-, fourth-, and eighth-order nonlinear processing on the filtered sampled signal to eliminate the modulated bipolar pseudo-code and data information stream in the signal, respectively obtaining single carrier components of second, fourth, and eighth frequencies, and extracting signal characteristics that vary with the phased array antenna beam direction;

[0063] The filtered sampled signal is subjected to local sequence correlation to complete signal capture, from which signal features that change with the phased array antenna beam direction are extracted. The local sequence correlation includes the local spreading code sequence under spread spectrum modulation and the local training symbol under OFDM system.

[0064] (23) Signal characteristics that vary with the direction of the phased array antenna beam include time domain characteristics, frequency domain characteristics, and modulation characteristics. Time domain characteristics refer to the mean value of the filtered sampled signal within the coherence time and the standard deviation of the filtered sampled signal within the coherence time. Frequency domain characteristics refer to the power spectrum density distribution of the filtered sampled signal. Modulation characteristics refer to the different modulation modes contained in the filtered sampled signal and the local spreading code and local training symbol types used by the filtered sampled signal. Only filtered sampled signals that meet the time domain characteristics, frequency domain characteristics, and modulation characteristics are considered to contain live TV satellite signals and can be extracted.

[0065] The existing technology uses communication satellites as space-based references and requires sampling of capture and demodulation schemes designed for the communication satellite signal system to complete communication satellite signal processing and feature extraction. The live TV satellite signal system processed in this step is fixed and does not require additional capture algorithms designed for the communication satellite signal system. The signal processing method used in this step only designs nonlinear processing and correlation processing, and signal features are easy to extract. Therefore, the algorithm is simple and has low computational complexity, and can quickly realize live TV satellite signal capture and feature extraction.

[0066] Step 3: Based on the changes in the signal characteristics described in step 2, use a feature recognition algorithm to identify and determine the energy of the sampled signal from the time domain characteristics, frequency domain characteristics and modulation characteristics, complete the detection of the live TV satellite signal, and thus realize the direction finding of each live TV satellite signal, and obtain the direction finding information of each live TV satellite in the phased array antenna carrier coordinate system, and the direction finding information includes azimuth information and pitch angle information.

[0067] like Figure 3 As shown, in particular, the above step three is specifically implemented as follows:

[0068] (31) The feature recognition algorithm identifies and determines the energy of the sampled signal based on the time domain features, frequency domain features, and modulation features. In terms of time domain features, the sampled signal contains continuous broadcast signals and periodic burst signals, and the burst signal time interval is consistent with the burst signal of the live TV satellite. In terms of frequency domain features, the sampled signal exists within each predetermined frequency band and the signal Doppler is zero. In terms of modulation features, the sampled signal modulation mode includes PSK modulation and OFDM modulation, and can match the local spread spectrum code and local training symbol.

[0069] (32) After completing the identification of the sampled signal, energy judgment is performed, and the relationship between the signal strength of each live TV satellite and the full airspace scan is counted. The beam direction corresponding to the maximum signal strength of each live TV satellite is used to complete the detection of the live TV satellite signal, thereby realizing the direction finding of each live TV satellite signal and obtaining the direction finding information of each live TV satellite in the phased array antenna carrier coordinate system.

[0070] Step 4: Use the direction-finding information of no less than two live TV satellites and the known fixed airspace positions of the live TV satellites as observation quantities, and the spatial information of the phased array antenna measured by the three types of sensors as the initial state to construct a fusion positioning equation, where the spatial information of the phased array antenna measured by the three types of sensors is the azimuth information of the current phased array antenna in the northeast celestial coordinate system measured by the magnetic sensor, the off-axis angular deviation angle and azimuth deviation angle of the array normal beam in the northeast celestial coordinate system of the phased array antenna carrier measured by the inertial sensor, and the altitude of the phased array antenna measured by the pressure sensor; use the fusion positioning equation to calculate the initial attitude and azimuth information of the phased array antenna in the northeast celestial coordinate system and the rough position information of the phased array antenna, and at the same time obtain the measurement corrections for the magnetic sensor, the three-axis accelerometer and the pressure sensor.

[0071] (41) In particular, the above fusion positioning equation is implemented as follows:

[0072] Assume the position of the phased array antenna is Point, there are 4 unknown quantities in the equation, which are: represents the longitude of the phased array antenna position, represents the latitude of the phased array antenna position, represents the initial azimuth angle of the phased array antenna beam, represents the initial elevation angle of the phased array antenna beam; represents the actual observation azimuth of k live TV satellites, Represents the actual observed elevation angle of the kth live TV satellite, and the following linearization formula is constructed:

[0073] ;

[0074] (42) Let the position of the kth live TV satellite be point, represents the longitude of the kth live TV satellite, represents the latitude of the kth live TV satellite, Representatives Projection point of a point on the earth's surface and the position of the phased array antenna The lines connecting the points are arc segments, which are respectively Point and The angle between the two meridians of the projection point on the earth's surface is read as the angle between the two meridians. Indicates that the air pressure sensor measures the altitude of the phased array antenna. represents the orbital height of the kth live TV satellite, represents the radius of the earth, which is obtained according to the trihedral angle cosine formula:

[0075] ;

[0076] According to the spherical sine formula, we can get:

[0077] ;

[0078] According to the plane cosine formula, we get:

[0079] ;

[0080] The above equations are solved together to calculate the initial position (longitude and latitude), initial azimuth and initial elevation of the phased array antenna.

[0081] make , then: , further:

[0082] , ;

[0083] in:

[0084] ;

[0085] ;

[0086] make , then:

[0087] , ;

[0088] in:

[0089] , ;

[0090] The above formula can also be further referenced:

[0091] make , then:

[0092] , ;

[0093] in:

[0094] ;

[0095] ;

[0096] (43) Order ;

[0097] The least squares method shown below is used to perform iterative solution to obtain the initial heading attitude and rough position information of the phased array antenna:

[0098] ;

[0099] The direction-finding results of live TV satellites are used to calculate the initial heading and attitude of the phased array antenna, as well as the rough position of the phased array antenna. Compared with the existing technology, there is no need to use navigation satellites for positioning and communication satellites for initial heading and attitude calculation. It has the advantages of simple calculation and strong applicability, and can be applied to situations where navigation satellites are unavailable and non-cooperative signals of communication satellites cannot be used.

[0100] In summary, the present invention solves the problem of calibrating the initial attitude and azimuth state of the phased array antenna in extreme situations such as being unable to obtain real-time satellite ephemeris, the initial position being unknown, and GNSS being unavailable. Compared to existing reverse calibration methods using inertial sensors and communication satellite beacon signals, this method does not require the use of a GNSS navigation constellation to obtain the position information of the phased array antenna, providing a practical and usable calibration method for the initial attitude and azimuth state calibration of the phased array antenna that serves positioning needs. Based on multi-sensor fusion, the present invention uses a direct television broadcast satellite as a reference benchmark to reversely obtain the initial attitude and azimuth information of the phased array antenna. Since the direct television broadcast satellite is a geosynchronous orbit satellite, there is no need to obtain the ephemeris parameters of the reference benchmark satellite in real time, and the initial attitude and azimuth state calibration of the Ku-band phased array antenna can still be completed offline, further improving the practicality and usability of the system. The present invention uses an existing direct television broadcast satellite as a reference satellite and uses its broadcast Ku signal as a reference signal. This allows the Ku-band phased array antenna to directly receive signals without the need to set up multiple frequency bands. Compared with the existing method of setting up a multi-frequency combination antenna to receive satellite signals in different frequency bands, the requirements for the hardware platform are greatly reduced.

[0101] Although the above describes the illustrative specific embodiments of the present invention to facilitate understanding of the present invention by those skilled in the art, and it should be clear that the present invention is not limited to the scope of the specific embodiments, it is obvious to those skilled in the art that as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

Claims

1. A method for determining the initial attitude, orientation, and position of a Ku-band phased array antenna, characterized by: Step 1: Use the magnetic sensor readings in the northeast celestial coordinate system to perform coordinate conversion to obtain the azimuth information of the current phased array antenna in the northeast celestial coordinate system; use the inertial sensor three-axis accelerometer to estimate the horizontal attitude of the phased array antenna and obtain the off-axis angle deviation angle and azimuth angle deviation angle of the array normal beam in the northeast celestial coordinate system of the phased array antenna carrier coordinate system; The phased array antenna uses an air pressure sensor to estimate the altitude. The phased array antenna is used to scan the entire airspace and sample signals. The phased array antenna beam direction corresponds to the data stream of the signal sampling in time. Step 2: Perform multi-pass filtering on the data stream of the signal sampling to filter out interference signals, obtain a filtered sampling signal, and perform signal processing such as nonlinear processing or local sequence correlation to extract signal characteristics of the sampling signal that change with the phased array antenna beam direction; Step 3: Based on the changes in the signal characteristics described in step 2, a feature recognition algorithm is used to identify and determine the energy of the sampled signal from the time domain characteristics, frequency domain characteristics, and modulation characteristics, thereby completing the detection of the live TV satellite signal, thereby achieving direction finding of each live TV satellite signal, and obtaining the direction finding information of each live TV satellite in the phased array antenna carrier coordinate system, wherein the direction finding information includes azimuth information and pitch angle information; Step 4: Using the direction-finding information of no less than two live TV satellites and the known fixed airspace positions of the live TV satellites as observation quantities, and the spatial information of the phased array antenna measured by the three types of sensors as the initial state, a fusion positioning equation is constructed to calculate the initial attitude and azimuth information of the phased array antenna in the northeast celestial coordinate system and the rough position information of the phased array antenna. At the same time, the measurement corrections for the magnetic sensor, three-axis accelerometer, and air pressure sensor are obtained. The spatial information of the phased array antenna measured by the three types of sensors is the azimuth information of the current phased array antenna in the northeast celestial coordinate system measured by the magnetic sensor, the off-axis angular deviation angle and azimuth angular deviation angle of the array normal beam in the phased array antenna carrier coordinate system measured by the inertial sensor, and the altitude of the phased array antenna measured by the air pressure sensor. In step 4, the fusion positioning equation is implemented as follows: Assume the position of the phased array antenna is Point, there are 4 unknown quantities in the equation, which are: represents the longitude of the phased array antenna position, represents the latitude of the phased array antenna position, represents the initial azimuth angle of the phased array antenna beam, represents the initial elevation angle of the phased array antenna beam; represents the actual observation azimuth of k live TV satellites, Represents the actual observed elevation angle of the kth live TV satellite, and the following linearization formula is constructed: ； The solution is completed based on the least squares method.

2. The method for determining the initial attitude, orientation, and position of a Ku-band phased array antenna according to claim 1, wherein: In the step 2, the passband of the multi-passband filter only includes the entire signal frequency range under the frequency points corresponding to each program of the live TV satellite, and after filtering, the signal of the live TV satellite signal band with periodic bursts and continuous broadcasts is obtained.

3. The method for determining the initial attitude, orientation, and position of a Ku-band phased array antenna according to claim 1 or 2, wherein: In step 2, the signal processing method is performed in one or both of the following modes: (1) Performing second-, fourth-, and eighth-order nonlinear processing on the filtered sampled signal to eliminate the modulated bipolar pseudo code and data information stream in the signal, and obtaining single carrier components of second, fourth, and eighth frequencies, respectively, from which signal characteristics that change with the phased array antenna beam direction are extracted; (2) Performing local sequence correlation on the filtered sampled signal to complete signal capture and extract signal features that change with the phased array antenna beam direction. The local sequence correlation includes the local spread spectrum code sequence under spread spectrum modulation and the local training symbol under OFDM system.

4. The method for determining the initial attitude, orientation, and position of a Ku-band phased array antenna according to claim 1 or 2, wherein: In the step 2, the signal characteristics that change with the phased array antenna beam direction include time domain characteristics, frequency domain characteristics and modulation characteristics; (1) Time domain characteristics refer to: The filtered sampled signal is averaged within the coherence time; The standard deviation of the filtered sampled signal within the coherence time; (2) Frequency domain characteristics refer to: Power spectral density distribution of the filtered sampled signal; (3) Modulation characteristics refer to: Different modulation modes contained in the filtered sampled signal; The local spreading code and local training symbol type used by the filtered sampled signal; Only the filtered sampling signals that simultaneously meet the time domain characteristics, frequency domain characteristics and modulation characteristics are considered to contain live TV satellite signals and can be extracted.

5. The method for determining the initial attitude, orientation, and position of a Ku-band phased array antenna according to claim 1 or 2, wherein: In step 3, the feature recognition algorithm identifies and determines the energy of the sampled signal based on the time domain features, frequency domain features, and modulation features. The process is as follows: In terms of time domain characteristics, the sampling signal contains both continuous broadcast signals and periodic burst signals, and the time interval of the burst signals is consistent with the burst signal of the live TV satellite. In terms of frequency domain characteristics, the sampling signal exists within each predetermined frequency band and the signal Doppler is zero. In terms of modulation characteristics, the sampling signal modulation methods include PSK modulation and OFDM modulation, and can match the local spreading code and local training symbols. After completing the sampling signal identification, energy judgment is performed, and the relationship between the signal strength of each live TV satellite and the full airspace scan is counted to obtain the beam direction corresponding to the maximum signal strength of each live TV satellite. The detection of the live TV satellite signal is completed, thereby realizing the direction finding of each live TV satellite signal and obtaining the direction finding information of each live TV satellite in the phased array antenna carrier coordinate system.

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