A Beidou receiver navigation system and method based on dual-antenna adaptive attitude transformation

Abstract

The present invention discloses a Beidou receiver navigation system and method based on dual antennas adapted to attitude transformation. The system includes an aircraft and a navigation and positioning module. The navigation and positioning module includes a baseband signal acquisition module, a navigation processing module, a pseudorange compensation module, a positioning and calculation module, and a database. The method steps are as follows: 1) Each antenna transmits a satellite navigation radio frequency signal; 2) Obtain the satellite navigation baseband signal; 3) Decode to obtain the satellite navigation observable information and send it to the navigation processing module; 4) Extract the pseudorange from the antenna to each satellite; 5) Calculate the corrected pseudorange Ρ' from the center position of the aircraft to each satellite; 6) The positioning and calculation module receives and calculates the corrected pseudorange Ρ' from the center position of the aircraft to each satellite to obtain the position of the aircraft. The present invention adopts a new dual-antenna positioning method to solve the drawback of 3 dB signal attenuation of the dual antennas, so as to improve the positioning reliability problem under high dynamics.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation, and specifically to a Beidou receiver navigation system and method based on dual antennas adapted to attitude transformation. Background Art

[0002] With the maturity of Beidou satellites, various aircraft are increasingly equipped with Beidou receivers to improve navigation accuracy. However, when some aircraft are flying in the air, they are not as stable as airplanes, and their flying postures are arbitrary. They may rotate, dive, or make sharp turns, etc. The satellite receiver relies on the satellite antenna to receive satellite signals from the sky for positioning. The positioning accuracy is directly related to the number of received satellites and the DOP distribution of the satellites. If most of the received satellite signals come from one side of the sky, see Figure 1 , and the satellites in the other half of the sky cannot be received, the positioning accuracy of the Beidou satellite receiver will drop rapidly, and the positioning reliability will decrease. To address the positioning reliability problem caused by the attitude change of the aircraft, the currently commonly used solution is to deploy dual antennas or multiple antennas at different parts of the aircraft, see Figure 2 , and then combine the signals of multiple antennas through RF to form a combined omnidirectional antenna, see Figure 5 , to address the directivity problem during attitude transformation. This solution has a certain effect, but through the direct combination of dual antenna RF signals, the signal is attenuated by 3dB, and the attenuation of the RF signal combined by multiple antennas is even more serious and increases exponentially. The attenuation caused by the RF link makes the originally weak satellite signal even weaker, making it difficult to achieve high-dynamic positioning and ensuring the positioning result. Therefore, currently, the dual antenna technology is mostly used to balance the signal attenuation and the satellite reception quality under attitude transformation. Summary of the Invention

[0003] The object of the present invention is to provide a Beidou receiver navigation system based on dual antennas adapted to attitude transformation, including an aircraft and a navigation and positioning module.

[0004] There are n antennas provided on the aircraft. n≥2. n is a positive integer.

[0005] Each antenna uses an independent RF channel to send satellite navigation RF signals to the navigation and positioning module.

[0006] The navigation and positioning module includes a baseband signal acquisition module, a navigation processing module, a pseudorange compensation module, a positioning and calculation module, and a database.

[0007] The baseband signal acquisition module samples each satellite navigation RF signal respectively to obtain a satellite navigation baseband signal. The sampling frequency is denoted as f. Each satellite navigation RF signal is independent of each other; each satellite navigation RF signal has undergone down-conversion processing.

[0008] The baseband signal acquisition module decodes the satellite navigation baseband signal to obtain satellite navigation observation information and sends it to the navigation processing module.

[0009] The baseband signal acquisition module simultaneously samples n channels of satellite navigation RF signals.

[0010] The satellite navigation observation information includes carrier information, satellite spreading code, original message information, and signal strength.

[0011] The navigation processing module analyzes the satellite navigation observation information and extracts the pseudorange from the antenna to each satellite.

[0012] The steps of extracting the pseudorange from the antenna to each satellite are as follows:

[0013] 1) Obtain the satellite navigation observation information carried by each channel of satellite navigation baseband signal respectively.

[0014] 2) Determine whether there is a situation where multiple channels of satellite navigation baseband signals carry the same satellite navigation observation information. If so, select one channel of satellite navigation baseband signal according to the signal strength and pseudorange residual value, and delete the navigation observation information of the corresponding satellite in other satellite navigation baseband signals. The criteria for selecting the satellite navigation baseband signal are: the maximum signal strength value and / or the minimum pseudorange residual value.

[0015] The pseudorange compensation module compensates the pseudorange from the antenna to each satellite, calculates the corrected pseudorange Ρ' from the center position of the aircraft to each satellite, and sends it to the positioning and calculation module.

[0016] The corrected pseudorange Ρ' from the satellite to the center position of the aircraft is as follows:

[0017] Ρ' = Ρ + δ. (1)

[0018] In the formula, Ρ is the original pseudorange received by the antenna. δ is the distance from the antenna to the center position of the aircraft.

[0019] The positioning and calculation module receives and calculates the corrected pseudorange Ρ' from the center position of the aircraft to each satellite to obtain the position of the aircraft.

[0020] The steps of the positioning and calculation module receiving and calculating the corrected pseudorange Ρ' from the center position of the aircraft to each satellite are as follows:

[0021] 1) Establish a pseudorange calculation equation between the antenna and the satellite, that is:

[0022]

[0023] In the formula, is the actual distance from the antenna to the satellite. δt uIs the product of the clock error of the satellite navigation system and the speed of light. Is other error terms. (x, y, z) are the position coordinates of antenna R. (x (n) , y (n) , z (n) ) are the position coordinates of satellite S n .

[0024] 2) Linearize formula (2) at the vector [x k-1 , y k-1 , z k-1 , δt u,k-1 to obtain: T where:

[0025]

[0026] In the formula, r (n) (x k-1 ) represents the distance between satellite S n and the aircraft obtained after the (k - 1)th iteration.

[0027] 3) Rewrite formula (3) into matrix form, i.e.:

[0028] Gx = b (4)

[0029] In the formula, matrix G represents vector x represents matrix b represents

[0030] 4) Use the least squares method to solve formula (4) to obtain:

[0031]

[0032] In the formula, Δx, Δy, and Δz are the antenna coordinate correction amounts. Δδt u is the correction amount of the product of the clock error of the satellite navigation system and the speed of light. The correction amount refers to the correction amount based on the intermediate result of the least squares method iteration.

[0033] 5) Update the antenna position coordinates (x, y, z) based on the antenna coordinate correction amounts. The antenna position is the aircraft coordinate.

[0034] The database stores the data of the baseband signal acquisition module, navigation processing module, pseudorange compensation module, and positioning solution module.

[0035] A method for using a Beidou receiver navigation system based on a dual - antenna adaptive attitude transformation includes the following steps:

[0036] 1) Each antenna of the aircraft receives satellite signals and sends satellite navigation radio frequency signals to the navigation and positioning module through independent radio frequency channels.

[0037] 2) The baseband signal acquisition module samples each satellite navigation RF signal to obtain a satellite navigation baseband signal. The sampling frequency is denoted as f.

[0038] 3) The baseband signal acquisition module decodes the satellite navigation baseband signal to obtain satellite navigation observation information and sends it to the navigation processing module.

[0039] 4) The navigation processing module analyzes the satellite navigation observation information and extracts the pseudorange from the antenna to each satellite.

[0040] 5) The pseudorange compensation module compensates the pseudorange from the antenna to each satellite, calculates the corrected pseudorange Ρ’ from the center position of the aircraft to each satellite, and sends it to the positioning and calculation module.

[0041] 6) The positioning and calculation module receives and calculates the corrected pseudorange Ρ’ from the center position of the aircraft to each satellite to obtain the position of the aircraft.

[0042] The technical effect of the present invention is beyond doubt. The present invention adopts a new dual-antenna positioning method to solve the drawback of 3 dB signal attenuation of the dual-antenna, so as to improve the positioning reliability problem under high dynamics. Description of the Drawings

[0043] Figure 1 Schematic diagram of the situation where a single antenna on the aircraft receives satellites in half of the sky;

[0044] Figure 2 Schematic diagram of the situation where dual antennas on the aircraft receive satellites in the omni-directional sky;

[0045] Figure 3 Schematic diagram of the satellite navigation positioning principle;

[0046] Figure 4 Schematic diagram of the pseudorange correction of the dual antennas receiving satellites respectively.

[0047] Figure 5 Flowchart of the dual-antenna RF signal combining receiver scheme.

[0048] Figure 6 Flowchart of the receiver scheme with dual antennas independently processed through the baseband channel. Detailed Embodiment

[0049] The present invention will be further described below in conjunction with the embodiments, but it should not be understood that the above-mentioned subject scope of the present invention is limited to the following embodiments. Without departing from the above technical idea of the present invention, various substitutions and changes made according to the common general knowledge and customary means in the art shall be included within the protection scope of the present invention.

[0050] Embodiment 1:

[0051] See Figures 1 to 6 , a Beidou receiver navigation system based on dual - antenna adaptive attitude transformation, including an aircraft and a navigation and positioning module.

[0052] There are n antennas installed on the aircraft. n≥2. n is a positive integer.

[0053] Each antenna uses an independent radio frequency channel to send satellite navigation radio frequency signals to the navigation and positioning module.

[0054] The navigation and positioning module includes a baseband signal acquisition module, a navigation processing module, a pseudorange compensation module, a positioning solution module, and a database.

[0055] The baseband signal acquisition module samples each satellite navigation radio frequency signal respectively to obtain satellite navigation baseband signals. The sampling frequency is denoted as f. Each satellite navigation radio frequency signal has undergone down - conversion processing. The down - conversion processing is implemented through a frequency - conversion circuit.

[0056] The baseband signal acquisition module decodes the satellite navigation baseband signals to obtain satellite navigation observable information and sends it to the navigation processing module.

[0057] The baseband signal acquisition module samples n satellite navigation radio frequency signals simultaneously.

[0058] The satellite navigation observable information includes carrier information, satellite spreading code, original message information, and signal strength.

[0059] The navigation processing module analyzes the satellite navigation observable information and extracts the pseudorange from the antenna to each satellite.

[0060] The steps to extract the pseudorange from the antenna to each satellite are as follows:

[0061] 1) Obtain the satellite navigation observable information carried by each satellite navigation baseband signal respectively.

[0062] 2) Determine whether there is a situation where multiple satellite navigation baseband signals carry the same satellite navigation observable information. If so, select one satellite navigation baseband signal according to the signal strength and pseudorange residual value, and delete the navigation observable information of the corresponding satellite in other satellite navigation baseband signals. The criteria for selecting the satellite navigation baseband signal are: the maximum signal strength value and / or the minimum pseudorange residual value.

[0063] The pseudorange compensation module compensates the pseudorange from the antenna to each satellite, calculates the corrected pseudorange Ρ’ from the center position of the aircraft to each satellite, and sends it to the positioning solution module.

[0064] The corrected pseudorange Ρ’ from the satellite to the center position of the aircraft is as follows:

[0065] Ρ’ = Ρ + δ. (1)

[0066] Where Ρ is the original pseudorange received by the antenna. δ is the distance from the antenna to the center position of the aircraft. The original pseudorange is the measured value of the antenna phase center.

[0067] The positioning and calculation module receives the corrected pseudorange Ρ’ from the center position of the aircraft to each satellite and performs calculations to obtain the position of the aircraft.

[0068] The steps for the positioning and calculation module to receive the corrected pseudorange Ρ’ from the center position of the aircraft to each satellite and perform calculations are as follows:

[0069] 1) Establish the pseudorange calculation equation between the antenna and the satellite, that is:

[0070]

[0071] Where is the actual distance from the antenna to the satellite. δt u is the product of the satellite navigation system clock error and the speed of light. is other error terms. (x, y, z) are the position coordinates of the antenna R. (x (n) , y (n) , z (n) ) are the position coordinates of the satellite S n .

[0072] 2) Linearize formula (2) at the vector [x k-1 , y k-1 , z k-1 , δt u,k-1 to obtain: T to get:

[0073]

[0074] Where r (n) (x k-1 ) represents the distance between the satellite S n and the aircraft obtained after k-1 iterations.

[0075] 3) Rewrite formula (3) into matrix form, that is:

[0076] Gx = b (4)

[0077] Where the matrix G represents the vector x represents the matrix b represents

[0078] 4) Use the least squares method to solve formula (4) to obtain:

[0079]

[0080] Wherein, Δx, Δy, and Δz are the antenna coordinate correction amounts. Δδt u is the correction amount of the product of the satellite navigation system clock error and the speed of light.

[0081] 5) Update the antenna position coordinates (x, y, z) based on the antenna coordinate correction amounts. The antenna position is the aircraft coordinate.

[0082] The database stores the data of the baseband signal capture module, the navigation processing module, the pseudorange compensation module, and the positioning and solution module.

[0083] Embodiment 2:

[0084] A method for using a Beidou receiver navigation system based on dual-antenna adaptive attitude transformation includes the following steps:

[0085] 1) Each antenna of the aircraft receives satellite signals and sends the satellite navigation radio frequency signals to the navigation and positioning module through independent radio frequency channels.

[0086] 2) The baseband signal capture module samples each satellite navigation radio frequency signal respectively to obtain the satellite navigation baseband signal. The sampling frequency is denoted as f.

[0087] 3) The baseband signal capture module decodes the satellite navigation baseband signal to obtain the satellite navigation observable information and sends it to the navigation processing module.

[0088] 4) The navigation processing module analyzes the satellite navigation observable information and extracts the pseudorange from the antenna to each satellite.

[0089] 5) The pseudorange compensation module compensates the pseudorange from the antenna to each satellite, calculates the corrected pseudorange Ρ' from the aircraft center position to each satellite, and sends it to the positioning and solution module.

[0090] 6) The positioning and solution module receives and solves the corrected pseudorange Ρ' from the aircraft center position to each satellite to obtain the aircraft position.

[0091] Embodiment 3:

[0092] See Figure 5 , a method for using a Beidou receiver navigation system based on dual-antenna adaptive attitude transformation includes the following steps:

[0093] 1) According to the flight configuration and characteristics of the aircraft, two satellite antennas, or multiple satellite antennas, are deployed at different positions on the aircraft, and there is no limit to the distance between the antennas. Each satellite antenna undergoes down-conversion processing through its own independent radio frequency channel (different from the conventional multi-antenna combining scheme, where radio frequency combining and intermediate frequency combining are not performed here), and directly enters the navigation baseband for intermediate frequency baseband signal processing. This signal contains carrier information as well as the original information of the satellite spreading code and message.

[0094] 2) The navigation baseband adopts a multi-baseband parallel processing method, with multiple baseband channels set inside. Each baseband channel processes the satellite signals of one antenna, and simultaneously captures, tracks, and extracts observation quantities from the signals coming from multiple antennas.

[0095] The multiple navigation baseband channels in the navigation baseband are independent of each other, and each baseband channel can meet the requirements of backend positioning and solution calculation. The navigation processing reads the observation quantity information of multiple baseband channels simultaneously, and analyzes the respective navigation baseband observation quantities (signals from different antennas), and then extracts the satellite signals in the entire sky. For the situation where some satellite signals may be tracked simultaneously in multiple navigation baseband channels, according to the signal strength (preferably the stronger one) and the observation quantity accuracy (preferably the one with higher pseudorange accuracy, generally according to the carrier dynamic range, select the one with smaller pseudorange residual, such as less than 10 meters as the preferred condition, the smaller the residual, the better), one is selected to ensure that the backend of the baseband fits the distribution of omnidirectional sky satellites. For the situation where some satellite signals can be received by antenna A but not by antenna B, the union of A and B is selected for positioning and solution calculation.

[0096] 4) The navigation solution unit performs pseudorange compensation on the observation quantities from different baseband channels (different antennas), see Figure 4 . During compensation, according to the size of the aircraft and the relative positions of different antennas, and a central point is set. When performing pseudorange compensation, the pseudorange is compensated to this central point to ensure that the positioning accuracy error caused by the inconsistent phase centers of multiple antennas does not increase. Since the pseudorange ρ of the satellite is very large, generally about 20,000 kilometers, while the distance δ from the antenna phase center to the central point O of the carrier is relatively small, generally several tens of centimeters or a few meters in magnitude, the pseudorange correction can be approximated as Ρ’ = Ρ + δ. Where Ρ’ is the satellite pseudorange corrected to the central position, Ρ is the original pseudorange received by a certain antenna, and δ is the distance from a certain antenna to the center of the carrier.

[0097] 5) After pseudorange compensation, the multi-satellite pseudorange intersection method is used to establish a positioning solution equation for positioning and solution calculation to obtain the current point position, speed, and time. The basic principle of satellite navigation positioning is distance intersection, that is, by measuring the distances from the satellite navigation system (antenna) to each satellite, the position coordinates of the satellite navigation system (antenna) are obtained, as Figure 3 shown.

[0098] Let the position coordinates of the satellite navigation system (antenna) R be (x, y, z), and the satellite S n has position coordinates (x (n) , y (n) , z (n) ). The pseudo-range measurement value from the satellite S n to the satellite navigation system (antenna) R, after being corrected for delays such as those in the ionosphere and troposphere and for satellite clock error, is The following equation can be obtained:

[0099]

[0100] where is the actual distance from the satellite navigation system (antenna) to the satellite, δt u is the product of the satellite navigation system clock error and the speed of light, is other error terms. Ignoring the influence of other error terms, the above equation has four unknowns, x, y, z, and δt u . Therefore, at least 4 satellites need to be observed simultaneously to establish at least 4 equations in order to solve for the position coordinate values of the satellite navigation system (antenna) R. When solving the above equation, the common algorithm is to linearize the equation according to the Taylor expansion and solve the linearized matrix equation using the least squares method in Newton iteration. If k represents the number of Newton iterations currently in progress at the current epoch, then linearizing Equation 1 at k-1 [x k-1 , y k-1 , z u,k-1 T yields the following equation.

[0101]

[0102] where r (n) (x k-1 ) represents the distance from the satellite S n to the satellite navigation system obtained after k - 1 iterations. The above equation can be represented in matrix form as follows:

[0103] Gx = b (3)

[0104] The least squares solution of which is

[0105] ​

Claims

1. A Beidou receiver navigation system based on dual antennas adapting to attitude transformation, characterized in that, it includes an aircraft and a navigation and positioning module; There are n antennas arranged on the aircraft; n≥2; n is a positive integer; Each antenna uses an independent radio frequency channel to send satellite navigation radio frequency signals to the navigation and positioning module; The navigation and positioning module includes a baseband signal acquisition module, a navigation processing module, a pseudorange compensation module, a positioning calculation module and a database; The baseband signal acquisition module samples each satellite navigation radio frequency signal respectively to obtain satellite navigation baseband signals; the sampling frequency is denoted as f; each satellite navigation radio frequency signal is independent of each other; The baseband signal acquisition module decodes the satellite navigation baseband signals to obtain satellite navigation observable information and sends it to the navigation processing module; The navigation processing module analyzes the satellite navigation observable information and extracts the pseudorange from the antenna to each satellite; The pseudorange compensation module compensates the pseudorange from the antenna to each satellite, calculates the corrected pseudorange Ρ’ from the center position of the aircraft to each satellite, and sends it to the positioning calculation module; After pseudorange compensation, the positioning calculation module uses the multi-satellite pseudorange intersection method to establish a positioning calculation equation and solve the corrected pseudorange Ρ’ from the center position of the aircraft to each satellite to obtain the position of the aircraft; The database stores the data of the baseband signal acquisition module, the navigation processing module, the pseudorange compensation module and the positioning calculation module; The corrected pseudorange Ρ’ from the satellite to the center position of the aircraft is as follows: Ρ’ = Ρ + δ'; (1) In the formula, Ρ is the original pseudorange received by the antenna; δ' is the distance from the antenna to the center position of the aircraft.

2. The Beidou receiver navigation system based on dual antennas adapting to attitude transformation according to claim 1, characterized in that, the baseband signal acquisition module samples the n satellite navigation radio frequency signals simultaneously.

3. The Beidou receiver navigation system based on dual antennas adapting to attitude transformation according to claim 1, characterized in that, the satellite navigation observable information includes carrier information, satellite spreading code, original message information and signal strength.

4. The Beidou receiver navigation system based on dual antennas adapting to attitude transformation according to claim 1, characterized in that, the steps of extracting the pseudorange from the antenna to each satellite are as follows: 1) Obtain the satellite navigation observable information carried by each satellite navigation baseband signal respectively; 2) Judge whether there is a situation where multiple satellite navigation baseband signals carry the same satellite navigation observable information. If so, select one satellite navigation baseband signal according to the signal strength and pseudorange residual value, and delete the navigation observable information of the corresponding satellite in other satellite navigation baseband signals.

5. The Beidou receiver navigation system based on dual antennas adapting to attitude transformation according to claim 4, characterized in that, the criteria for selecting the satellite navigation baseband signal are: the maximum signal strength value and / or the minimum pseudorange residual value.

6. The Beidou receiver navigation system based on dual antennas adapting to attitude transformation according to claim 1, characterized in that, The steps for the positioning and calculation module to receive and calculate the corrected pseudo-range Ρ’ from the center position of the aircraft to each satellite are as follows: 1) Establish the pseudo-range calculation equation between the antenna and the satellite, that is: In the formula, is the actual distance from the antenna to the satellite; δt u is the product of the satellite navigation system clock error and the speed of light; is other error terms; (x, y, z) are the position coordinates of antenna R; (x (n) , y (n) , z (n) ) are the position coordinates of satellite S n ; 2) Linearize formula (2) at the vector [x k-1 , y k-1 , z k-1 , δt u,k-1 T to obtain:​ where r (n) (x k-1 ) represents the distance between satellite S n and the vehicle obtained after the (k - 1)th iteration; 3) Rewrite formula (3) into matrix form, that is: Gx = b (4) In the formula, matrix G represents The vector x represents The matrix b represents 4) Use the least squares method to solve formula (4) to obtain: where Δx, Δy, and Δz are the antenna coordinate correction amounts; Δδt u is the correction amount of the product of the satellite navigation system clock error and the speed of light; 5) Update the antenna position coordinates (x, y, z) based on the antenna coordinate correction amount; the antenna position is the aircraft coordinate.

7. A Beidou receiver navigation system based on a dual-antenna adaptive attitude transformation according to claim 1, characterized in that each satellite navigation radio frequency signal has undergone down-conversion processing.

8. A method of using the Beidou receiver navigation system based on a dual-antenna adaptive attitude transformation according to any one of claims 1 to 6, characterized in that it includes the following steps: 1) Each antenna of the aircraft receives satellite signals and sends the satellite navigation radio frequency signals to the navigation and positioning module using independent radio frequency channels; 2) The baseband signal acquisition module samples each satellite navigation radio frequency signal respectively to obtain the satellite navigation baseband signal; the sampling frequency is denoted as f; 3) The baseband signal acquisition module decodes the satellite navigation baseband signal to obtain the satellite navigation observable information and sends it to the navigation processing module; 4) The navigation processing module analyzes the satellite navigation observable information and extracts the pseudo-range from the antenna to each satellite; 5) The pseudo-range compensation module compensates the pseudo-range from the antenna to each satellite, calculates the corrected pseudo-range Ρ’ from the center position of the aircraft to each satellite, and sends it to the positioning and calculation module; 6) The positioning and calculation module receives and calculates the corrected pseudo-range Ρ’ from the center position of the aircraft to each satellite to obtain the aircraft position.

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