A deep space satellite navigation signal simulator

Abstract

The present invention discloses a deep space satellite navigation signal simulator, which belongs to the field of deep space exploration satellite navigation technology. It includes a data simulation device, a signal generation device, and a signal broadcasting device. The data simulation device simulates the constellation of the deep space satellite navigation system, calculates the orbit and navigation message of the deep space satellite navigation constellation using orbital dynamics theory, and uses a mathematical model to calculate the pseudo-range and Doppler observation between the deep space satellite and the user terminal; the signal generation device uses a GPU to accelerate the calculation of a digital intermediate frequency signal in parallel and up-convert it into a radio frequency signal, and the signal broadcasting device realizes the broadcasting of the deep space satellite navigation system signal. The present invention adopts software-defined simulation and unified signal broadcasting architecture, has the advantages of high precision, easy upgrade, low cost, etc., and can simulate and evaluate the navigation positioning and timing performance of deep space satellite navigation systems with different constellation configurations and different signal systems.

Description

Technical Field

[0001] The invention belongs to the technical field of deep space exploration satellite navigation, and in particular relates to a deep space satellite navigation signal simulator. Background Art

[0002] As the exploration of the moon and deep space continues to deepen, the construction of lunar and Mars bases, resource development, and more complex scientific exploration activities will all require more accurate and reliable navigation services. The traditional navigation and positioning methods based on ground measurement and control have limited accuracy and cannot meet the diverse needs of future deep space activities, thus giving rise to the need to build a deep space satellite navigation system.

[0003] Due to the complexity and particularity of the construction of deep space satellite navigation systems, it is necessary to conduct sufficient demonstration and simulation verification before the construction of the system, provide preliminary testing and verification for the construction of deep space satellite navigation systems and navigation and positioning services, and ensure the stability and reliability of the navigation system in the deep space environment. The space environment between the Earth and the Moon or between the Earth and Mars is very different from the satellite navigation environment around the Earth. The distance between the Earth and the Moon / Earth and Mars is farther than that between the Earth and the Moon, and there is a large delay and attenuation in signal transmission; the gravitational field of the sun and the planets will also affect the propagation of signals; in addition, there are interference factors such as solar wind and cosmic rays in the Earth-Moon / Earth-Mars space. Whether it is lunar exploration or Mars exploration, higher requirements will be placed on the accuracy of the navigation system. The positioning and navigation of users in the Earth-Moon / Earth-Mars space must be controlled within a very small range. These factors will bring huge challenges to the design and implementation of deep space satellite navigation systems. Summary of the invention

[0004] In view of the above problems, the present invention proposes a deep space satellite navigation signal simulator. The present invention adopts software-defined simulation and unified signal broadcasting architecture, has the advantages of high precision, easy upgrade, low cost, etc., and can simulate and evaluate the navigation, positioning and timing performance of deep space satellite navigation systems with different constellation configurations and different signal systems.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A deep space satellite navigation signal simulator, comprising a data simulation device, a signal generation device and a signal broadcasting device;

[0007] The data simulation device is implemented based on a PC and is used to simulate and generate satellite orbits and user motion trajectory data of a deep space satellite navigation system, thereby generating pseudo-range observations and navigation messages;

[0008] The signal generating device is implemented based on NVIDA CUDA and is used to calculate a zero intermediate frequency signal of a multi-channel combined path according to pseudo-range observations and navigation messages;

[0009] The signal broadcasting device is implemented based on XILINX Zynq UltraScale+RFSOC, and is used to process multi-channel combined zero intermediate frequency signals and output analog radio frequency signals.

[0010] Furthermore, the data simulation device performs the following steps:

[0011] Step 1: According to the initial information set by the user, the user's motion trajectory at any point in the simulation space is simulated by numerical integration through velocity and acceleration to generate the 3D position, 3D velocity, 3D acceleration and 3D posture information of the user terminal;

[0012] Step 2, using the input constellation configuration information, using a high-precision dynamic model to calculate the acceleration of the deep space satellite navigation satellite, and numerically integrating the acceleration of the deep space satellite navigation satellite to obtain the orbit of the deep space navigation system satellite at any time;

[0013] Step 3: Use the built-in quadratic satellite clock error model to obtain the satellite clock error after extrapolation;

[0014] Step 4: Analyze the visible satellites based on the satellite orbits of the deep space satellite navigation system and the user's motion trajectory data, and select the visible satellites at the current moment;

[0015] Step 5: According to the satellite orbit of the deep space satellite navigation system and the user's motion trajectory data, combined with the satellite transmitting antenna and the receiving end antenna model, considering the influence of the earth's rotation, ionospheric delay, tropospheric delay and general relativity gravity delay, calculate the pseudo-range observation value with the user's receiving time as the time scale, and then send it to the signal generation device;

[0016] Step 6: For the currently visible satellite, use the least squares method to fit the orbit and clock error of the navigation constellation orbit to obtain the optimal expression of the ephemeris parameters, that is, the navigation message, which is sent to the signal generation device.

[0017] Furthermore, the signal generating device performs the following steps:

[0018] Step 1, receiving the pseudo-range observation data and navigation message data sent by the data simulation device, and after data distribution, calculating the signal transmission time and transmission attenuation by frequency band and satellite one by one, and performing error calculation, signal transmission time calculation and signal strength calculation to generate intermediate frequency signal input parameters;

[0019] Step 2: For each satellite, generate a pseudo code for each frequency point through a pseudo code generator and store it in a data buffer area;

[0020] Step 3: According to the signal strength, signal transmission time, and signal transmission time, the sparse and discrete pseudo-range observations are encrypted by GPU interpolation, and the strength, message, pseudo-code, and carrier phase are modulated in combination with the broadcast message and pseudo-code in the data buffer area. The multi-channel combined zero intermediate frequency signal is output, and the zero intermediate frequency signals and noise signals generated by multiple satellites are added and sent to the signal broadcasting device through the PCIE high-speed data channel.

[0021] Furthermore, the signal broadcasting device performs the following steps:

[0022] Step 1: Receive data sent by the signal generation device, parse and verify it according to the frequency point, write the correct data into the DDR cache, retransmit and verify the wrong data until it is correct and store it in the DDR cache. If it times out, report the error status; then, at the arrival time of the whole second, read the data from the DDR cache and input it into the FIFO part of the RF module;

[0023] Step 2: After I / Q interpolation, I / Q mixing, delay control, filtering, and RF-DAC conversion, the output of the analog RF signal is completed.

[0024] The beneficial effects of the present invention compared with the prior art are:

[0025] 1. The present invention is applicable to deep space satellite navigation systems and can realize the simulation and broadcasting of radio frequency signals of deep space satellite navigation systems.

[0026] 2. The present invention is based on a software radio platform and uses a PC to realize data simulation of a deep space satellite navigation system. Based on NVIDIA Quadrature and GPU parallel computing, the present invention generates a digital zero intermediate frequency signal, which has a simple architecture and is flexible and reliable.

[0027] 3. The present invention adopts XILINX Zynq UltraScale+RFSOC architecture to generate radio frequency signals, and the radio frequency broadcasting frequency can be flexibly configured through software.

[0028] In summary, the present invention adopts software-defined simulation and unified signal broadcasting architecture, which can realize deep space satellite navigation information simulation, zero intermediate frequency signal simulation and radio frequency signal broadcasting. It has the advantages of high precision, easy upgrade and low cost, and can simulate and evaluate the navigation, positioning and timing performance of deep space satellite navigation systems with different constellation configurations and different signal systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 4 is a schematic diagram of pseudorange simulation in an embodiment of the present invention.

[0030] Figure 2 It is a schematic diagram of the working principle of the deep space satellite navigation signal simulator in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] A deep space satellite navigation signal simulator, such as Figure 2 As shown, it includes a data simulation device, a signal generation device and a signal broadcasting device. The device uses the data simulation device to simulate the deep space satellite navigation system constellation, uses the orbital dynamics theory to calculate the orbit and navigation message of the deep space satellite navigation constellation, and uses a mathematical model to calculate the pseudo-range and Doppler observation amount between the deep space satellite and the user terminal; sends the pseudo-range, Doppler observation amount and navigation satellite message generated by the simulation to the signal generation device, and then uses the GPU to accelerate the calculation of the digital intermediate frequency signal in parallel and up-convert it into a radio frequency signal, and finally realizes the broadcast of the deep space satellite navigation system signal through the signal broadcasting device.

[0033] Specifically, the data simulation device performs the following steps:

[0034] Step 1: According to the initial information set by the user, the user's motion trajectory at any point in the simulation space is simulated by numerical integration through velocity and acceleration to generate the 3D position, 3D velocity, 3D acceleration and 3D posture information of the user terminal;

[0035] Step 2, using the input constellation configuration information, the acceleration of the deep space satellite navigation satellite is calculated using a high-precision dynamics model, and the satellite acceleration is numerically integrated to obtain the orbit of the deep space navigation system satellite at any time; the high-precision dynamics model includes the gravity of the center of the earth, the non-spherical gravity of the earth, the three-body perturbation force of the moon, the sun and other large planets in the solar system, the solid tide perturbation force of the earth, the solar light pressure perturbation force and the relativistic effect, etc.;

[0036] Step 3: Use the built-in quadratic satellite clock error model to obtain the satellite clock error after extrapolation;

[0037] Step 4: Analyze the visible satellites based on the satellite orbits of the deep space satellite navigation system and the user's motion trajectory data, and select the visible satellites at the current moment;

[0038] Step 5: According to the satellite orbit of the deep space satellite navigation system and the user's motion trajectory data, combined with the satellite transmitting antenna and the receiving end antenna model, considering the influence of the earth's rotation, ionospheric delay, tropospheric delay and general relativity gravity delay, calculate the pseudo-range observation value with the user's receiving time as the time scale, and then send it to the signal generation device;

[0039] Step 6: For the currently visible satellite, use the least squares method to fit the orbit and clock error of the navigation constellation orbit to obtain the optimal expression of the ephemeris parameters, that is, the navigation message, which is sent to the signal generation device.

[0040] The signal generating device performs the following steps:

[0041] Step 1, receiving the pseudo-range observation data and navigation message data sent by the data simulation device, and after data distribution, calculating the signal transmission time and transmission attenuation by frequency band and satellite one by one, and performing error calculation, signal transmission time calculation and signal strength calculation to generate intermediate frequency signal input parameters;

[0042] Step 2: For each satellite, generate a pseudo code for each frequency point through a pseudo code generator and store it in a data buffer area;

[0043] Step 3: According to the signal strength, signal transmission time, and signal transmission time, the sparse and discrete pseudo-range observations are encrypted by GPU interpolation, and the strength, message, pseudo-code, and carrier phase are modulated in combination with the broadcast message and pseudo-code in the data buffer area. The multi-channel combined zero intermediate frequency signal is output, and the digital intermediate frequency signals and noise signals generated by multiple satellites are added and sent to the signal broadcasting device through the PCIE high-speed data channel.

[0044] The signal broadcasting device performs the following steps:

[0045] Step 1: Receive the zero intermediate frequency signal data sent by the signal generation device, analyze and verify it according to the frequency point, write the correct data into the DDR cache, retransmit and recheck the wrong data, and store it in the DDR cache within a certain period of time until it is correct. If it times out, report the error status. Next, at the arrival of the whole second, read the data from the DDR cache and input it into the FIFO of the RF module;

[0046] Step 2: After I / Q interpolation, I / Q mixing, delay control, filtering, and RF-DAC conversion, the output of the analog RF signal is completed.

[0047] In this simulator, the data simulation device is implemented based on a high-performance PC. When the internal simulation time of the entire simulation system adopts geodynamics, the coordinate system adopts the solar system mass center J2000 coordinate system. The data simulation device is used to simulate and generate satellite orbits and user motion trajectory data of the deep space satellite navigation system, and then generate pseudo-range observations and navigation messages. It can use high-performance CPUs to calculate orbital integrals, orbital dynamics, navigation message fitting, error model simulation, and observation simulation, etc., to achieve deep space navigation satellite orbit simulation, user trajectory simulation, and observation simulation.

[0048] First, user trajectory simulation is performed. A variety of simulation trajectory algorithms are built in, which can simulate the user motion trajectory of any point in deep space, and generate the three-dimensional position, three-dimensional velocity, three-dimensional acceleration and three-dimensional posture information of users on Earth, users on the Moon and users on Earth and Mars. The formula is as follows:

[0049]

[0050]

[0051]

[0052] Where a0 represents the user's initial acceleration, a input Indicates the acceleration parameters input according to different user states, is the user's current total acceleration, For user speed, is the user's three-dimensional position. The user trajectory can be obtained by integrating the above formula using a numerical integrator.

[0053] In the satellite orbit simulation process, the simulation dynamics model includes the gravity of the Earth's center, the Earth's non-spherical gravity, the three-body perturbation force of the Moon, the Sun and other large planets in the solar system, the Earth's solid tidal perturbation force, the solar light pressure perturbation force and the relativistic effect, etc. The formula is as follows:

[0054]

[0055]

[0056]

[0057] Among them, in the Newtonian reference frame, represents the gravitational force at the center of the Earth, represents the non-spherical gravitational perturbation of the Earth, represents the three-body perturbation force of a large celestial body, represents the earth's solid tidal force, represents the compressive force of sunlight, represents the relativistic effect perturbation force, These forces jointly determine the trajectory of the satellite. The data simulation device uses the preset initial state of the deep space satellite navigation constellation to The deep space satellite navigation constellation orbit can be obtained by integrating the above formula through a numerical integrator. Then, the orbit and clock error of the deep space satellite navigation constellation orbit obtained are fitted using the least squares method to obtain the optimal expression of the ephemeris parameters and send it to the signal generation device.

[0058] The observation simulation is based on the satellite orbit and user trajectory data of the deep space satellite navigation system. Since the deep space satellite navigation system includes multiple users on the Earth, Moon, Mars and Earth, the distance between users and navigation satellites is relatively far, and the influence of general relativity needs to be considered. In order to improve the accuracy of the simulation, the simulation observation process is carried out in the solar system barycenter reference frame (BCRS). The pseudorange calculation formula is as follows:

[0059] ρ 12 =[t2(UTC)-t1(UTC)]c

[0060] =[t2(TDB)-t1(TDB)]c-[t2(TDB)-t2(UTC)]c+[t1(TDB)-t1(UTC)]c

[0061] Wherein, t2(UTC) represents the Coordinated Universal Time (UTC) when the satellite broadcasts the signal, t1(UTC) represents the UTC when the user receives the signal, t2(TDB) represents the Solar System Barycenter Dynamic Time (TDB) when the satellite broadcasts the signal, and t1(TDB) represents the Solar System Barycenter Dynamic Time (TDB) when the user receives the signal. Figure 1 As shown. The first term in the above formula is the distance of signal propagation under BCRS, which takes into account the influence of gravitational delay. The second and third terms represent the distance correction caused by the time scale correction from TDB to UTC. The solution formula for the propagation distance of the optical signal is as follows:

[0062]

[0063]

[0064] Among them, r 21 represents the geometric distance between the satellite position at time t2(TDB) and the user position at time t1(TDB), β is the post-Newton parameter, which is generally 1, and M s is the mass of the sun, and It represents the geometric distance from the sun to the satellite or user, M i represents the masses of the planets and the Moon in the solar system in order, and Respectively represent M i The geometric distance to the satellite or user; t trans represents the delay caused by the transmitting antenna model, t rece represents the delay caused by the antenna model at the receiving end, t ion represents the ionospheric delay, t trop Represents the tropospheric delay. After the pseudorange calculation is completed, it is sent to the signal generation device.

[0065] The signal generation device is implemented based on NVIDACUDA, and is used to calculate the zero intermediate frequency signal of the multi-channel combination according to the pseudo-range observation and navigation message. The signal generation device first calculates the pseudo code of the deep space satellite navigation signal, and uses NVIDACUDA to parallelly calculate the sparse discrete pseudo-range sent by the data simulation device, and encrypts the data after interpolation, and then calculates the carrier phase data by combining the broadcast message and the pre-generated pseudo code; finally, the intensity, message, pseudo code, and carrier phase are modulated to output the zero intermediate frequency signal. The formula is as follows:

[0066]

[0067]

[0068] S=S1+S2+…+S n +ε

[0069] Where T is the signal period, f is the signal frequency, represents the signal phase, represents the signal carrier, A represents the signal strength, D(t) represents the signal message, C(t) is the pseudo code of the signal, S1 represents a certain frequency signal, S2 and S n represents other frequency signals, ε is the common noise of the signal. S is the generated zero intermediate frequency signal, which will then be sent to the XILINX Zynq UltraScale+RFSOC development component through a high-speed transmission link.

[0070] The signal broadcasting device is based on XILINX Zynq UltraScale+RFSOC and is responsible for up-conversion and signal broadcasting. The device stores the received digital zero intermediate frequency data into the buffer unit according to the frequency point, completes I / Q interpolation, I / Q mixing, delay control, and filtering processing at every full second, and completes the conversion of digital intermediate frequency signals to analog radio frequency signals through RF-DAC.

[0071] In summary, the present invention can be applied to signal simulation of deep space satellite navigation systems. It adopts software-defined simulation and unified signal broadcasting architecture, and has the advantages of high precision, easy upgrade, and low cost. It can simulate and evaluate the navigation, positioning and timing performance of deep space satellite navigation systems with different constellation configurations and different signal systems, which is of great significance to the demonstration, construction and service operation of deep space satellite navigation systems.

Claims

1. A deep space satellite navigation signal simulator, characterized in that: It includes a data simulation device, a signal generating device and a signal broadcasting device; The data simulation device is implemented based on a PC and is used to simulate and generate satellite orbits and user motion trajectory data of a deep space satellite navigation system, thereby generating pseudo-range observations and navigation messages; The signal generating device is implemented based on NVIDACUDA and is used to calculate a zero intermediate frequency signal of a multi-channel combined path according to pseudo-range observations and navigation messages; The signal broadcasting device is implemented based on XILINX Zynq UltraScale+RFSOC, and is used to process multi-channel combined zero intermediate frequency signals and output analog radio frequency signals.

2. A deep space satellite navigation signal simulator according to claim 1, characterized in that: The data simulation device performs the following steps: Step 1: According to the initial information set by the user, the user's motion trajectory at any point in the simulation space is simulated by numerical integration through velocity and acceleration to generate the 3D position, 3D velocity, 3D acceleration and 3D posture information of the user terminal; Step 2, using the input constellation configuration information, using a high-precision dynamic model to calculate the acceleration of the deep space satellite navigation satellite, and numerically integrating the acceleration of the deep space satellite navigation satellite to obtain the orbit of the deep space navigation system satellite at any time; Step 3: Use the built-in quadratic satellite clock error model to obtain the satellite clock error after extrapolation; Step 4: Analyze the visible satellites based on the satellite orbits of the deep space satellite navigation system and the user's motion trajectory data, and select the visible satellites at the current moment; Step 5: According to the satellite orbit of the deep space satellite navigation system and the user's motion trajectory data, combined with the satellite transmitting antenna and the receiving end antenna model, considering the influence of the earth's rotation, ionospheric delay, tropospheric delay and general relativity gravity delay, calculate the pseudo-range observation value with the user's receiving time as the time scale, and then send it to the signal generation device; Step 6: For the currently visible satellite, use the least squares method to fit the orbit and clock error of the navigation constellation orbit to obtain the optimal expression of the ephemeris parameters, that is, the navigation message, which is sent to the signal generation device.

3. A deep space satellite navigation signal simulator according to claim 1, characterized in that: The signal generating device performs the following steps: Step 1, receiving the pseudo-range observation data and navigation message data sent by the data simulation device, and after data distribution, calculating the signal transmission time and transmission attenuation by frequency band and satellite one by one, and performing error calculation, signal transmission time calculation and signal strength calculation to generate intermediate frequency signal input parameters; Step 2: For each satellite, generate a pseudo code for each frequency point through a pseudo code generator and store it in a data buffer area; Step 3: According to the signal strength, signal transmission time, and signal transmission time, the sparse and discrete pseudo-range observations are encrypted by GPU interpolation, and the strength, message, pseudo-code, and carrier phase are modulated in combination with the broadcast message and pseudo-code in the data buffer area. The multi-channel combined zero intermediate frequency signal is output, and the zero intermediate frequency signals and noise signals generated by multiple satellites are added and sent to the signal broadcasting device through the PCIE high-speed data channel.

4. A deep space satellite navigation signal simulator according to claim 1, characterized in that: The signal broadcasting device performs the following steps: Step 1: Receive data sent by the signal generation device, parse and verify it according to the frequency point, write the correct data into the DDR cache, retransmit and verify the wrong data until it is correct and store it in the DDR cache. If it times out, report the error status; then, at the arrival time of the whole second, read the data from the DDR cache and input it into the FIFO part of the RF module; Step 2: After I / Q interpolation, I / Q mixing, delay control, filtering, and RF-DAC conversion, the output of the analog RF signal is completed.

Images