CN113794497B - Mobile satellite communication antenna terminal with anti-interference positioning function - Google Patents
Mobile satellite communication antenna terminal with anti-interference positioning function Download PDFInfo
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- CN113794497B CN113794497B CN202110975543.5A CN202110975543A CN113794497B CN 113794497 B CN113794497 B CN 113794497B CN 202110975543 A CN202110975543 A CN 202110975543A CN 113794497 B CN113794497 B CN 113794497B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18517—Transmission equipment in earth stations
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/27—Adaptation for use in or on movable bodies
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/02—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18513—Transmission in a satellite or space-based system
Abstract
A mobile satellite communications antenna terminal with interference-resistant positioning, comprising: a directional transceiving antenna, an IMU or INS module, a GNSS module (optional), an antenna control module, a doppler shift tracking module, a position state estimation module, a satellite communication module, etc. The directional transmitting and receiving antenna forms a directional beam to realize the transmitting and receiving of satellite communication signals; the IMU or INS module acquires attitude information of the motion carrier; the antenna control module controls the antenna beam to be aligned with the communication satellite; the Doppler frequency shift tracking module carries out Doppler frequency shift tracking on a satellite communication signal carrier or a beacon; the position state estimation module is used for fusing various information and outputting high-precision position information of the motion carrier. The invention can realize that the satellite communication function and the motion carrier positioning function of the mobile satellite communication antenna terminal can work normally when the GNSS module does not exist or GNSS signals are interfered.
Description
Technical Field
The invention belongs to the technical field of satellite communication terminals, and particularly relates to a mobile satellite communication antenna terminal with an anti-interference positioning function.
Background
The traditional mobile satellite communication antenna terminal can realize satellite facing by the antenna by depending on GNSS equipment to provide position information of a moving carrier, and further assist in realizing beam pointing control between the carrier and the satellite. In the case of interference of GNSS, the satellite communication system is difficult to work normally.
In the face of complex modern battlefield environment conditions, GNSS information is easily interfered, so that a moving carrier satellite communication measurement and control system cannot work normally, and communication is interrupted.
The applicant submits a Chinese invention patent with the application number of 202110845079.8 from 2021-07-26, which relates to a moving carrier navigation method and a device based on directional antennas and Doppler information, and realizes the moving carrier navigation based on the directional antennas and the Doppler information by adopting the following steps:
s1: knowing the precise initial position of the moving carrier, which carries the directional antenna, fixed or moving beacon position information. When there are multiple fixed or mobile beacons, one of them can be selected according to the use environment and other limitations, and switched during operation according to the strategy, or multiple beacons can be selected, and multiple directional antennas can be selected for use.
S2: the antenna beam control system based on the directional antenna utilizes IMU or INS assistance to keep the directional antenna always aligned with the beacon in the motion process of the motion carrier, and outputs the attitude angle of the motion carrier and the attitude angle deviation of the motion carrier during alignment. The method specifically comprises the following steps:
s2.1: in the moving process of the moving carrier, with the assistance of an IMU or an INS, obtaining the moving information of the moving carrier, namely the longitude and latitude information, the attitude angle and the attitude angle change rate of the moving carrier;
s2.2: determining an azimuth angle A, a pitch angle E and a polarization angle V of an antenna beam of a directional antenna in a geographic system by utilizing longitude and latitude information, an attitude angle and a beacon position of a moving carrier, and realizing beam adjustment by utilizing an antenna beam control system, so that the directional antenna initially faces a beacon to realize the capture of a beacon signal;
s2.3: after capturing the beacon signal, the directional antenna precisely aligns the beacon in a signal maximum mode to complete the stable tracking of the beacon and obtain the actual azimuth angle A of the antenna beam of the directional antenna in the geographic system during precise alignment T To the pitch angle E T ；
S2.4: after the wave beam tracking is realized, the attitude angle deviation of the moving carrier is obtained according to the azimuth angle and pitch angle control deviation signals, and the attitude angle deviation of the moving carrier, namely the azimuth angle A and the pitch angle E, and the actual azimuth angle A T Angle of pitch E T The deviation therebetween.
In the moving process of the moving carrier, the IMU or the INS continuously measures the attitude change of the moving carrier, and the beam pointing direction is adjusted by using the beam control system, so that the directional antenna beam is always pointed to the beacon and continuously tracked.
S3: and receiving the beacon signal obtained by the directional antenna by using a Doppler frequency shift tracking module, and measuring and obtaining Doppler frequency information caused by the movement of the moving carrier in the beacon signal. When S1 selects multiple beacons and multiple directional antennas, multiple beams are aligned to the multiple beacons, and multiple doppler frequencies and beam pointing information are obtained.
S4: and correcting errors of an inertial measurement component or an inertial navigation system based on the attitude angle of the moving carrier and the attitude angle deviation of the moving carrier when the directional antenna aligns the beacon, the beacon position information and the Doppler frequency information of a beacon signal received by the moving carrier, and finally outputting the corrected navigation position information of the moving carrier. When S1 selects a plurality of beacons and a plurality of directional antennas, navigation calculation utilizes a plurality of Doppler frequencies and beam pointing information, and correction precision is improved.
Namely, the error accumulation of the inertial measurement unit IMU or the inertial navigation system INS can be corrected by using the directional antenna pointing information, the attitude angle deviation of the motion carrier, the beacon position information and the navigation information obtained by Doppler information correction, so that the high-precision navigation information output is realized.
The method can realize signal processing on a moving carrier by utilizing the position and beacon signals of fixed or moving beacons such as a geosynchronous communication satellite and the like under the condition that navigation positioning systems such as a GPS/BD and the like fail, and meets certain-precision navigation positioning information of moving carriers such as vehicles, ships, airplanes and missiles.
However, the method still has the problems of poor interference resistance and the like.
Disclosure of Invention
In order to overcome the defects of the prior art and meet the requirement of anti-interference navigation and positioning of a satellite communication terminal on a motion carrier, the invention aims to provide a mobile satellite communication antenna terminal with an anti-interference positioning function.
In order to achieve the purpose, the invention adopts the technical scheme that:
a mobile satellite communications antenna terminal with tamper resistant positioning, comprising:
the directional transmitting and receiving antenna is arranged on the moving carrier and used for forming a directional antenna beam and realizing the transmitting and receiving of satellite communication signals or the receiving of satellite beacon signals;
the satellite communication module is used for modulating and demodulating satellite communication signals and amplifying power;
the IMU or INS module is used for acquiring attitude information of the motion carrier, calculating the position of the motion carrier, the attitude of the carrier and the attitude change rate, realizing the motion of the isolation carrier and keeping the mobile satellite communication antenna terminal stable;
the antenna control module is used for receiving the attitude information of the moving carrier provided by the IMU or the INS module, controlling the antenna beam to point to the communication satellite, keeping the directional transmitting-receiving antenna always aligned with the communication satellite in the moving process of the moving carrier, and outputting the attitude angle of the moving carrier and the attitude angle deviation of the moving carrier during alignment;
the Doppler frequency shift tracking module is used for receiving a beacon signal or a satellite communication signal obtained by the directional transmitting and receiving antenna, performing Doppler frequency shift tracking on a satellite communication signal carrier or a beacon, and measuring and obtaining Doppler frequency information caused by the movement of the moving carrier in the beacon or the carrier signal;
and the position state estimation module corrects errors of the IMU or INS module based on the initial position of the moving carrier, the attitude angle of the moving carrier and the attitude angle deviation of the moving carrier when the directional transceiving antenna is aligned with the beacon, the position information of the communication satellite and the Doppler frequency information of the beacon/carrier signal received by the moving carrier, and finally outputs the corrected navigation position information of the moving carrier.
In one embodiment of the present invention, further comprising:
and the GNSS module gives accurate position information of the moving carrier when the GNSS is available.
In an embodiment of the invention, under the condition that the position of the communication satellite is known, the antenna control module receives the position information of the moving carrier, the attitude of the carrier and the change rate information of the attitude given by the IMU or the INS module, and realizes the initial acquisition of the communication satellite by the communication-in-motion antenna; and then, according to the standard that the energy of the signals received by the directional transmitting and receiving antenna is maximum, the accurate alignment and tracking of the antenna beam to the satellite are realized.
In one embodiment of the present invention, the antenna beam is controlled by the antenna control module in a mechanical rotation mode or an electronic phase control mode.
In one embodiment of the present invention, for a communication satellite signal having linear polarization, the antenna control module performs linear polarization control and outputs a linear polarization deviation.
In an embodiment of the present invention, the directional transceiver antenna, the satellite communication module, the IMU or INS module, and the antenna control module are combined to implement a satellite communication function.
In one embodiment of the invention, the directional transceiving antenna, the IMU or INS module, the antenna control module, the doppler shift tracking module and the position state estimation module combine to realize a navigation positioning function of the moving carrier.
In one embodiment of the invention, the moving carrier is a missile, an airplane, a ship, a cannonball or a vehicle, the communication satellite is a geosynchronous communication satellite or a geosynchronous orbit communication satellite, and the directional transmitting and receiving antenna is a reflector antenna, a flat plate antenna or a phased array antenna.
In an embodiment of the present invention, the attitude angle deviation of the moving carrier is an azimuth angle a of the directional transmitting and receiving antenna in the geographic system and an actual azimuth angle a T And the elevation angle E of the antenna beam of the directional transmitting-receiving antenna in the geographic system and the actual elevation angle E T The deviation between A, E and the polarization angle V of the antenna beam of the directional transmitting/receiving antenna in the geographic system is calculated as follows:
wherein L is the latitude of the point where the moving carrier is locatedPi is pi, lambda is the longitude of the moving carrier, lambda s Longitude of the beacon subsatellite point;
the antenna control module performs fine alignment on A, E, namely, the antenna beam direction is modulated until the received beacon signal energy is maximum, fine alignment is considered to be achieved at the moment, and the antenna beam of the directional transmitting and receiving antenna is obtained at the actual azimuth angle A of the geographic system after fine alignment T To the pitch angle E T 。
In one embodiment of the present invention, the doppler frequency information in the beacon signal due to the motion of the moving carrier includes the true doppler frequency
And a doppler frequency error δ f, wherein:
δf＝δv r ·e rs ·c/f carrier ＝δv a ·c/f carrier
in the formula: v. of r Is the velocity, δ v, of the moving carrier in the earth-centered earth-fixed (ECEF) coordinate system r Is the velocity error, v, of the moving carrier in the geocentric geostationary coordinate system s Is the speed of the beacon in the geocentric geostationary coordinate system, e rs Is the unit vector of the sight line direction from the moving carrier to the beacon in the geocentric geostationary coordinate system, c is the speed of light, f carrier Is the carrier frequency, δ v a Is the speed error of the moving carrier in the direction of the moving carrier to the satellite video.
Compared with the prior art, the invention has the beneficial effects that:
on the basis of realizing the satellite communication function, the accurate position of the moving carrier can be output, and the positioning function of the moving carrier is realized. On the premise of the position of the motion carrier given by the navigation function, the satellite communication function can realize that the directional receiving and transmitting antenna can be always aligned to the satellite, and the satellite communication signal or the beacon signal is received to complete the satellite communication function; the satellite communication function realizes that the navigation function of the antenna terminal can complete the position estimation of the moving carrier and output the accurate position information of the moving carrier on the premise that the wave beam faces the satellite and can receive satellite signals or beacon signals. Therefore, the mobile satellite communication antenna terminal provided by the invention has the advantages that the satellite communication function and the navigation positioning function are mutually coupled and supported. In addition, because the directional transmitting and receiving antenna is adopted, external interference and deception signals are difficult to enter through the main lobe of the antenna, and therefore the mobile satellite communication antenna terminal with the navigation positioning function and the satellite communication function has the obvious anti-interference characteristic.
Drawings
Fig. 1 is a block diagram of a mobile satellite communications antenna terminal according to the present invention.
Fig. 2 is a diagram of a mobile communication antenna terminal vehicle-mounted experimental object in an embodiment of the present invention.
Fig. 3 is a physical diagram of a planar directional transmitting-receiving antenna used in one embodiment of the present invention.
Fig. 4 is a functional block diagram of a satellite communication module according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of the antenna control module control in an embodiment of the present invention.
Fig. 6 is a schematic diagram of an implementation of the doppler shift tracking module and the position state estimation module according to an embodiment of the present invention.
Fig. 7 is a schematic diagram of a motion carrier, a communication satellite and a coordinate relation according to an embodiment of the present invention.
Fig. 8 is a diagram illustrating measured positioning errors of a mobile satellite communications antenna terminal according to an embodiment of the present invention.
FIG. 9 is a flow chart of a location state estimation algorithm based on graph optimization according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The invention combines the navigation method and device of 202110845079.8 with the traditional mobile satellite communication antenna terminal, and provides a mobile satellite communication antenna terminal with anti-interference positioning function, under the premise of the position of the motion carrier given by the navigation function, the basic function of the motion carrier satellite communication can realize that the directional antenna can always aim at the satellite, receive satellite communication signals or beacon signals, and complete the satellite communication function; on the premise that the basic function of the satellite communication of the moving carrier realizes that the wave beam faces the satellite and can receive satellite signals or beacon signals, the navigation function of the antenna terminal can complete the position estimation of the moving carrier and output the accurate position information of the moving carrier. The mobile satellite communication antenna terminal with the anti-interference positioning function has the satellite communication function and the navigation positioning function which are mutually coupled and supported. In addition, because the directional antenna is adopted, external interference and deception signals are difficult to enter through the main lobe of the antenna, and therefore the mobile satellite communication antenna terminal has the obvious anti-interference characteristic. That is, the invention can output the accurate position of the moving carrier and realize the positioning function of the moving carrier on the basis of realizing the satellite communication function under the condition that the GNSS navigation positioning system fails. The navigation and positioning functions of the mobile carrier of the terminal can also ensure that the satellite communication function can still work normally under the condition that the GNSS is interfered.
The architecture of the present invention is shown in fig. 1, and mainly comprises:
the directional transmitting and receiving antenna is arranged on the moving carrier and used for forming a directional antenna beam and realizing the transmitting and receiving of satellite communication signals or the receiving of satellite beacon signals; illustratively, the moving carrier may be a missile, an airplane, a ship, a cannonball or a vehicle, the communication satellite may be a geosynchronous communication satellite or a geosynchronous orbit communication satellite, and the directional transmitting and receiving antenna may be a reflector antenna, a flat plate antenna or a phased array antenna.
The satellite communication module is mainly used for modulating and demodulating satellite communication signals and amplifying power;
the IMU or INS module is used for acquiring attitude information of the motion carrier, calculating the position of the motion carrier, the attitude of the carrier and the attitude change rate, realizing the motion of the isolation carrier and keeping the mobile satellite communication antenna terminal stable;
and the antenna control module is used for receiving the attitude information of the moving carrier provided by the IMU or the INS module, controlling the antenna beam to point to the communication satellite, keeping the directional transmitting-receiving antenna always aligned with the communication satellite in the moving process of the moving carrier, and outputting the attitude angle of the moving carrier and the attitude angle deviation of the moving carrier during alignment. Exemplarily, under the condition that the position of the communication satellite is known, the antenna control module receives the position information of the moving carrier, the attitude of the carrier and the attitude change rate information, which are provided by the IMU or the INS module, so as to realize the initial acquisition of the communication antenna in motion to the communication satellite; and then, according to the standard that the energy of the signals received by the directional transmitting and receiving antenna is maximum, the accurate alignment and tracking of the antenna beam to the satellite are realized. The control of the antenna beam by the antenna control module can be in a mechanical rotation mode or an electronic phase control mode
The Doppler frequency shift tracking module is used for receiving a beacon signal or a satellite communication signal obtained by the directional transmitting and receiving antenna, performing Doppler frequency shift tracking on a satellite communication signal carrier or a beacon, and measuring and obtaining Doppler frequency information caused by the movement of the moving carrier in the beacon or the carrier signal;
and the position state estimation module is used for correcting errors of the IMU or the INS module based on the initial position of the motion carrier, the attitude angle of the motion carrier and the attitude angle deviation of the motion carrier when the directional transceiving antenna is aligned to the beacon, the position information of the communication satellite and the Doppler frequency information of the beacon/carrier signal received by the motion carrier, and finally outputting the navigation position information of the motion carrier after correction.
In one embodiment of the present invention, the method may further include:
and the GNSS module gives accurate position information of the moving carrier when the GNSS is available.
In one embodiment of the present invention, the directional transceiver antenna, the satellite communication module, the IMU or INS module, the GNSS module (if any), and the antenna control module are combined to implement the satellite communication function. At the moment, the directional transmitting and receiving antenna forms a directional beam to realize the transmitting and receiving of satellite communication signals; the IMU or INS module senses the attitude information of the motion carrier, calculates the position of the motion carrier and realizes the motion isolation of the carrier; when the GNSS is available, the GNSS module gives accurate carrier position information; the antenna control module controls antenna beams to be aligned to a communication satellite by utilizing the position information of the carrier and the attitude information of the moving carrier; the satellite communication module comprises modules of satellite communication modulation and demodulation, power amplification and the like, and functions of modulation and demodulation, power amplification processing and the like of satellite communication transmitting and receiving signals are achieved.
In one embodiment of the invention, the directional transceiving antenna, the IMU or INS module, the antenna control module, the Doppler frequency shift tracking module and the position state estimation module are combined to realize the navigation and positioning functions of the moving carrier. The directional transmitting and receiving antenna forms a directional beam to realize satellite communication signal transmitting and receiving or satellite beacon signal receiving; the IMU or INS module senses the attitude information of the motion carrier, calculates the position of the motion carrier and realizes the motion isolation of the carrier; the antenna control module controls antenna beams to be aligned with the communication satellite, the directional transceiving antenna is kept to be aligned with the beacon all the time in the moving process of the moving carrier, and the attitude angle of the moving carrier and the attitude angle deviation of the moving carrier during alignment are output. For communication satellite signals with linear polarization, linear polarization control can be realized, and linear polarization deviation is output; the Doppler frequency shift tracking module receives a beacon signal or a satellite communication signal obtained by the directional transmitting and receiving antenna, realizes Doppler frequency shift tracking on a satellite communication signal carrier or a beacon, and measures and obtains Doppler frequency information caused by movement of a moving carrier in the beacon or the carrier signal; and the position state estimation module corrects errors of the inertial measurement component or the inertial navigation system based on the attitude angle of the moving carrier, the attitude angle deviation of the moving carrier, satellite position information and the Doppler frequency information of satellite beacons/carrier signals received by the moving carrier when the directional transmitting-receiving antenna aligns the beacon, and finally outputs the corrected navigation position information of the moving carrier. The position state estimation module can replace a GNSS module to be used for outputting the position of the moving carrier, so that an antenna control module in the mobile satellite communication antenna terminal is assisted to realize antenna beam control and stabilization.
Referring to fig. 2, in an embodiment of the present invention, the vehicle-mounted satellite communication-in-motion panel antenna is implemented by adding a satellite communication module, a doppler frequency shift tracking module, and a position state estimation module. Referring to fig. 3, in the embodiment, a planar antenna with an equivalent aperture of 0.9m is used, a main lobe of the planar antenna is used for receiving and transmitting satellite signals, the width of the main lobe is as narrow as possible, the gain is high, and a side lobe is as small as possible to enhance interference immunity. The communication satellite chosen in the example is asia-pacific 4 (134 ° E, beacon frequency 12250.5 MHz).
Fig. 4 is a functional schematic block diagram of a satellite communication module in an embodiment of the present invention, where the satellite communication module mainly includes modules such as a satellite communication modem and a power amplifier, and implements general functions such as modulation and demodulation, power amplification processing, and the like of a satellite communication transceiver signal, which are not described again.
Fig. 5 is a functional schematic block diagram of an antenna control module according to an embodiment of the present invention, where the antenna control module implements control of a polarization controller and control of two direct current motors of azimuth and elevation according to an output of an IMU module, and implements modulation of an antenna beam direction until a beacon signal energy received by a tracking receiver is maximum, at which time, it is considered that fine alignment is implemented, and after the fine alignment, an actual azimuth angle a of an antenna beam of a directional transmitting-receiving antenna in a geographic system is obtained T To the pitch angle E T . Attitude angle deviation of moving carrier, namely azimuth angle A, pitch angle E and actual azimuth angle A T Angle of pitch E T The deviation therebetween.
The azimuth angle A, the pitch angle E and the polarization angle V of the antenna beam of the directional transmitting-receiving antenna in the geographic system are as follows:
wherein L is a motion carrierThe latitude of the point, pi is pi, lambda is the longitude of the moving carrier, lambda s The longitude of the beacon substellar point.
Fig. 6 is a schematic diagram of an implementation of the doppler shift tracking module and the position state estimation module according to an embodiment of the present invention. The Doppler frequency shift tracking module is used for receiving a beacon signal (the frequency is 12250.5 MHz) obtained by the directional transmitting and receiving antenna, realizing Doppler frequency shift tracking of the satellite communication beacon and measuring and obtaining Doppler frequency information brought by a moving carrier in the beacon signal. In the embodiment, an atomic clock is used as a standard frequency source to output 10MHz and 24MHz reference frequency signals. The antenna control module outputs the beacon analog intermediate frequency signal (the frequency range is 0.95-1.45 GHz) after down-conversion as the input of the Doppler frequency shift tracking module. According to the relative motion and Doppler principle of the geosynchronous orbit satellite and the moving carrier, the Doppler model is
Wherein f is carrier Indicating the beacon signal frequency, v s Is the speed of the carrier in the geocentric geostationary coordinate system, which represents the speed of the carrier relative to the reference satellite, e is the unit vector of the line-of-sight direction of the moving carrier to the beacon in the geocentric geostationary coordinate system, and c represents the speed of light. The unit vector received from the signal to the transmission is defined as follows:
wherein
And
the positions of the satellites and the moving carrier in the ECEF.
Referring to fig. 6, the position state estimation module corrects an error of the inertial measurement unit or the inertial navigation system based on the attitude angle of the moving carrier and the attitude angle deviation of the moving carrier when the directional transmitting and receiving antenna is aligned with the beacon, the satellite position information, and the satellite beacon and the signal doppler frequency information received by the moving carrier, and finally outputs the corrected navigation position information of the moving carrier. The position state estimation module can replace a GNSS module to be used for outputting the position of the moving carrier, so that an antenna control module in the mobile satellite communication antenna terminal is assisted to realize antenna beam control and stabilization. The relationship among the moving carrier, the satellite beacon and the coordinate is shown in fig. 7, and the longitude and the latitude of the point of the moving carrier (in the northern hemisphere) are respectively set as λ (east longitude is positive, west longitude is negative) and L.
Symbol definition:
[v e ,v n ,v u ] T is the velocity vector v of the moving carrier in the northeast coordinate;
[δv e ,δv n ,δv u ] T is the moving carrier velocity error vector delta v ；
[λ,L,h] T Is the position vector p in the warp-weft-high expression form of the motion vector;
[δλ,δL,δh] T is the corresponding error vector δ p;
[e x ,e y ,e z ] T the unit vector e of the motion carrier relative to the sight direction of the communication satellite in the geocentric geostationary coordinate system;
R N is the spherical radius, and f is the eccentricity of the earth.
Receiver measures Doppler frequency information in beacon signals due to motion of moving carriers
Including true doppler frequency
And doppler frequency error δ f:
δf＝δv s ·e rs ·c/f carrier ＝δv a ·c/f carrier
in the formula:
δ f is the Doppler frequency error
c is the speed of light
f carrier Is the frequency of the beacon signal
v s Is the speed of the moving carrier in the geocentric geostationary coordinate system
v r Is the velocity of the target satellite in the geocentric geostationary coordinate system
δv s Is the speed error of the moving carrier in the geocentric geostationary coordinate system
e rs Is a unit vector of the sight direction of the moving carrier to the target satellite in the geocentric geostationary coordinate system
δv a Is the speed error of the moving carrier in the direction from the moving carrier to the satellite sight
In an embodiment of the present invention, the step of estimating the navigation position of the moving carrier in the position state estimation module is as follows.
(1) IMU module pre-integration process
The measurement models of the gyroscope and accelerometer are assumed to be:
wherein
Representing a rotation from the navigational coordinate system to the inertial coordinate system,
is the angular velocity of the earth rotation under the earth-centered earth-fixed coordinate system,
for navigation coordinate system rotation caused when the carrier is moving on the earth's surface with curvature,
and
respectively representing the measurement noise of the gyroscope and the accelerometer, and epsilon and delta respectively representing the deviation of the gyroscope and the accelerometer, which are independent of each other. g is a radical of formula n Representing the gravitational acceleration vector.
The construction of a high-precision IMU pre-integration measurement model comprises the following steps:
wherein
Is a mapping from ECEF to a navigation coordinate system, (a) represents an antisymmetric matrix of a vectors,
the pre-integral measurement model ensures that the pre-integral quantity is not related to the state quantities at the moment i and the moment j, so that the pre-integral quantity does not need to be recalculated each time the state quantities at the moment i and the moment j are updated. The pre-integral measurement model is related to the deviation, the pose and the speed of the moving carrier. These states are iterated through the optimization process. Suppose that
For the pre-integrated IMU state vector,
for incremental update, then
The error that can update the pre-integrated first estimate is:
jacobian matrix
Showing that the state update causes the IMU pre-integration measurement to change. The jacobian matrix, which remains unchanged during pre-integration, may be pre-computed during initialization.
(2) Doppler frequency pre-integration measurement model
Assume that the entire state vector is:
wherein x i The IMU state vector, the doppler frequency at time i is measurable. It contains the position, velocity and orientation of the ECEF frame, and the offset of the accelerometers and gyroscopes in the IMU count volume.
Indicating the rotation from the moving carrier to the navigation body at the i-th instant. k is the optimized track length.
Indicating the ECEF position of the observation satellite, b clk Representing the frequency offset of the satellite beacon. When the GNSS measurements are valid, the GNSS receiver may,
and b clk Can be observed.
The mahalanobis norm and residual for all pre-integrals, doppler measurements, and GNSS measurements and estimates are minimized to obtain the maximum a posteriori estimate as:
wherein r is I (·),r F (. And r) G () residuals of pre-integration, doppler frequency and GNSS positioning measurements, respectively.
(3) IMU pre-integrated measurement residual and Doppler frequency measurement residual
The position and velocity of the IMU pre-integration increment represent two consecutive structure measurements k and k +1, the measurement residual of the IMU pre-integration is defined as:
wherein
Respectively representing rotation, velocity and position of IMU pre-integration increments,
representing the mapping of the antisymmetric matrix M to a corresponding real vector a.
The residual of the doppler frequency pre-integration is defined as:
wherein
Obtaining a beacon signal frequency measurement by a doppler shift tracking module, and a GNSS measurement residual is defined as:
wherein
Representing position measurements and of GNSS at time j
Representing the velocity measurement at time j, independent of each other.
(4) State estimation algorithm based on graph optimization
In this embodiment, a graph optimization method is used to solve the nonlinear optimization problem. The calculation is cycled through by optimizing variables in all trajectories and then updating the pre-integration measurements until the residual is less than the threshold in the iterative process. The algorithm flow chart is shown in fig. 9.
In one embodiment of the invention, a self-made array IMU is used, the update rate is 200Hz, the vehicle is used as a moving carrier, and a driving path is selected. The east, north and sky speeds of the GPS are converted through coordinates to obtain the LOS speed of the moving carrier relative to the target satellite, the LOS speed is used as a measurement value to carry out combined navigation, the GPS does not participate in the navigation within 400 seconds to 900 seconds, and the algorithm is used for carrying out the combined navigation. The result of the combined navigation is shown in fig. 8. The mobile satellite communication antenna terminal has a navigation positioning function, can effectively inhibit the accumulated error of INS without depending on GNSS, and realizes navigation position output with certain precision.
Claims (10)
1. A mobile satellite communications antenna terminal with interference-free positioning, comprising:
the directional transmitting and receiving antenna is arranged on the motion carrier and used for forming a directional antenna beam and realizing the transmitting and receiving of satellite communication signals or the receiving of satellite beacon signals;
the satellite communication module is used for modulating and demodulating a satellite communication signal and amplifying power;
the IMU or INS module is used for acquiring attitude information of the motion carrier, calculating the position of the motion carrier, the attitude of the carrier and the attitude change rate, and isolating the motion of the carrier;
the antenna control module is used for receiving the attitude information of the moving carrier provided by the IMU or the INS module, controlling an antenna beam to point to the communication satellite, keeping the directional transmitting-receiving antenna always aligned with the communication satellite in the moving process of the moving carrier, and outputting a moving carrier attitude angle and a moving carrier attitude angle deviation during alignment;
the Doppler frequency shift tracking module is used for receiving a beacon signal or a satellite communication signal obtained by the directional transmitting and receiving antenna, performing Doppler frequency shift tracking on a satellite communication signal carrier or a beacon, and measuring and obtaining Doppler frequency information caused by the movement of the moving carrier in the beacon or the carrier signal;
and the position state estimation module corrects the error of the IMU or INS module based on the initial position of the moving carrier, the attitude angle of the moving carrier and the attitude angle deviation of the moving carrier when the directional transceiving antenna is aligned with the beacon, the position information of the communication satellite and the Doppler frequency information of the beacon/carrier signal received by the moving carrier, and finally outputs the corrected navigation position information of the moving carrier.
2. The mobile satellite communication antenna terminal with tamper resistant positioning function of claim 1, further comprising:
and the GNSS module gives accurate position information of the moving carrier when the GNSS is available.
3. The mobile satellite communication antenna terminal with anti-jamming positioning function according to claim 1 or 2, wherein under the condition that the position of the communication satellite is known, the antenna control module receives the position information of the moving carrier, the attitude of the carrier and the change rate information of the attitude given by the IMU or the INS module, so as to realize initial acquisition of the communication satellite by the communication antenna in motion; and then, according to the standard that the energy of the signals received by the directional transmitting and receiving antenna is maximum, the accurate alignment and tracking of the antenna beam to the satellite are realized.
4. The mobile satellite communications antenna terminal with interference-free positioning function of claim 3, wherein the antenna control module controls the antenna beam in a mechanically rotating manner or an electronically phased manner.
5. The mobile satellite communications antenna terminal with interference-free positioning function of claim 3, wherein for communications satellite signals with linear polarization, said antenna control module performs linear polarization control and outputs a linear polarization offset.
6. The mobile satellite communication antenna terminal with anti-jamming positioning function according to claim 1 or 2, wherein the directional transceiving antenna, the satellite communication module, the IMU or INS module, and the antenna control module are combined to implement a satellite communication function.
7. The mobile satellite communication antenna terminal with anti-jamming positioning function according to claim 1 or 2, wherein the directional transceiving antenna, the IMU or INS module, the antenna control module, the doppler shift tracking module, and the position state estimation module combine to realize the moving carrier navigation positioning function.
8. The mobile satellite communication antenna terminal with anti-jamming positioning function according to claim 1 or 2, wherein the moving carrier is a missile, an airplane, a ship, a cannonball or a vehicle, the communication satellite is a geosynchronous communication satellite or a geosynchronous orbit communication satellite, and the directional transmitting and receiving antenna is a reflector antenna, a flat antenna or a phased array antenna.
9. The mobile satellite communication antenna terminal with antijam positioning function of claim 1 or 2, wherein the attitude deviation of the moving carrier is the azimuth A of the antenna beam of the directional transmitting and receiving antenna in the geographic system and the actual azimuth A T And the elevation angle E of the antenna beam of the directional transmitting-receiving antenna in the geographic system and the actual elevation angle E T The deviation between them, A, E and the polarization angle V of the antenna beam of the directional transmitting and receiving antenna in the geographic system are calculated as follows:
wherein, L is the latitude of the point where the motion carrier is located, pi is pi, lambda is the longitude of the motion carrier, and lambda is s Longitude of the beacon subsatellite point;
the antenna control module performs fine alignment on A, E, namely, the antenna beam direction is modulated until the received beacon signal energy is maximum, at this moment, the fine alignment is considered to be realized, and the antenna beam of the directional transmitting and receiving antenna is obtained after the fine alignment at the actual azimuth angle A of the geographic system T And angle of pitch E T 。
10. The mobile satellite communication antenna terminal with interference-free positioning function according to claim 9, wherein the doppler frequency information in the beacon signal due to the motion of the moving carrier includes a true doppler frequency
And a doppler frequency error δ f, wherein:
δf＝δv r ·e rs ·c/f carrier ＝δv a ·c/f carrier
in the formula: v. of r Is the velocity, δ v, of the moving carrier in the geocentric geostationary coordinate system r Is the velocity error, v, of the moving carrier in the geocentric geostationary coordinate system s Is the speed of the beacon in the geocentric geostationary coordinate system, e rs Is the unit vector of the sight line direction from the moving carrier to the beacon in the geocentric geostationary coordinate system, c is the speed of light, f carrier Is the carrier frequency, δ v a Is the speed error of the moving carrier in the direction of the moving carrier to the satellite video.
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