Method and apparatus for arbitrary satellite non-cooperative positioning

Abstract

The application discloses a method and device for non-cooperative positioning of any satellite, and the method comprises the following steps: extracting Doppler information of each satellite at different observation times according to carrier signals of multiple satellites received at different observation times; constructing an equation group with time and Doppler frequency shift as known quantities, satellite orbit parameters, satellite carrier frequency and receiver coordinates as unknown quantities according to the extracted Doppler information; and solving the equation group to obtain the coordinates of the receiver. The application extracts Doppler information and constructs an equation group by receiving signals of any satellite overhead, calculates the position coordinates of the receiver, and realizes navigation and positioning when GNSS is interfered or suppressed.

Description

Technical Field

[0001] This invention belongs to the field of navigation and positioning technology, and particularly relates to a method and apparatus for non-cooperative positioning of arbitrary satellites. Background Technology

[0002] Normally, GNSS (Global Navigation Satellite System) can be used for navigation and positioning. However, under certain conditions, such as when GNSS is interfered with or suppressed, it cannot be used. Although inertial navigation can be used as a temporary supplement, the cumulative error problem of inertial navigation is quite significant. Summary of the Invention

[0003] To address the navigation and positioning problem when GNSS is interfered with or suppressed, this invention provides a method and apparatus for non-cooperative positioning with any satellite. By receiving signals from any satellite passing overhead, extracting Doppler information, constructing a set of equations, and calculating the receiver coordinates, navigation and positioning can be achieved when GNSS is interfered with or suppressed.

[0004] According to one aspect of the present invention, a method for arbitrary satellite non-cooperative positioning is provided, comprising:

[0005] Based on the carrier signals received from multiple satellites at different observation times, Doppler information of each satellite at different observation times is extracted;

[0006] Based on the extracted Doppler information, a system of equations is constructed with time and Doppler frequency shift as known quantities and satellite orbital parameters, satellite carrier frequency and receiver coordinates as unknown quantities.

[0007] Solve the system of equations to obtain the coordinates of the receiver.

[0008] As a further technical solution, the method also includes: setting the relationship between the number of observations M and the number of satellites N to satisfy: M×N>7×N+3.

[0009] As a further technical solution, the method also includes: receiving carrier signals from multiple satellites at different observation times according to a set number of observations.

[0010] As a further technical solution, after receiving carrier signals from multiple satellites at different observation times, it also includes:

[0011] Calculate the position and velocity of each of the aforementioned satellites at different observation times;

[0012] Calculate the relative velocity between each satellite and the receiver at different observation times;

[0013] Based on the relative velocity, the Doppler shift of each of the satellites at different observation times is calculated.

[0014] As a further technical solution, after obtaining the Doppler frequency shift of each satellite at different observation times, the method further includes:

[0015] Based on the Doppler frequency shift formula, equations are constructed for each satellite at different observation times;

[0016] A set of equations is formed based on the equations of multiple satellites at different observation times.

[0017] As a further technical solution, solving the system of equations includes: using the least squares method or Newton's method to solve the system of equations.

[0018] According to one aspect of the present invention, an apparatus for arbitrary satellite non-cooperative positioning is provided, comprising:

[0019] The signal extraction module is used to extract the Doppler information of each satellite at different observation times based on the carrier signals received from multiple satellites at different observation times.

[0020] The signal solving module is used to construct a system of equations with time and Doppler frequency shift as known quantities and satellite orbital parameters, satellite carrier frequency and receiver coordinates as unknown quantities based on the extracted Doppler information, and solve the system of equations to obtain the coordinates of the receiver.

[0021] According to one aspect of the present invention, a receiver is provided, which is equipped with the aforementioned device for non-cooperative positioning of any satellite.

[0022] According to one aspect of the present invention, a receiver is provided, comprising: a radio frequency front-end assembly for receiving satellite signals; a signal sampling and digitization assembly for sampling and digitizing the received satellite signals; a signal demodulation and frequency analysis assembly for processing the converted signals and extracting Doppler information from the satellite; and a positioning calculation assembly for constructing a system of equations based on the extracted Doppler information, wherein time and Doppler frequency shift are known quantities, and satellite orbital parameters, satellite carrier frequency, and receiver coordinates are unknown quantities, and solving the system of equations to obtain the coordinates of the receiver.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The proposed non-cooperative positioning method for arbitrary satellites, by receiving signals from any overlying satellite, extracting Doppler information, and constructing a system of equations for calculation, enables receiver positioning without needing to know the orbital parameters of these satellites, thus achieving navigation and positioning when GNSS is interfered with or suppressed. Furthermore, this invention, while obtaining receiver coordinates, can also acquire satellite orbital parameters and carrier frequencies for other uses. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram illustrating the principle of an arbitrary satellite non-cooperative positioning method provided in an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram illustrating the specific process of receiver position determination provided in an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of a receiver provided in an embodiment of the present invention. Detailed Implementation

[0029] It should be noted that:

[0030] This invention addresses the current situation where GNSS is unusable due to interference or suppression, and using inertial navigation for temporary supplementation leads to significant cumulative errors. It provides an arbitrary satellite non-cooperative positioning method, which can be used as an alternative navigation and positioning scheme when GNSS is interfered with or suppressed.

[0031] Existing technologies employ various techniques to address the challenge of achieving high-precision navigation when signals are interfered with or disrupted. However, current technologies still rely on satellite orbit data to calculate satellite positions. In practice, satellite orbit data is difficult to obtain during non-cooperative positioning (some data is classified, and more often, accuracy and timeliness cannot be guaranteed). Furthermore, when the location is unknown, it is difficult to identify the satellite to which the received signal belongs, making it challenging to correlate the received signal with its orbit. Compared to existing technologies, the method of this invention does not require satellite orbit data and can directly calculate its own position, thus improving usability and reliability.

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form new technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0033] Please see Figure 1 This invention provides a method for non-cooperative positioning of arbitrary satellites. First, based on the carrier signals of multiple satellites received at different observation times, Doppler information of each satellite at different observation times is extracted. Then, based on the extracted Doppler information, a system of equations is constructed with time and Doppler frequency shift as known quantities and satellite orbital parameters, satellite carrier frequency, and receiver coordinates as unknown quantities. Finally, the system of equations is solved to obtain the coordinates of the receiver.

[0034] It should be noted that when a satellite is in motion, the receiver receives satellite signals and experiences the Doppler effect. Since the Doppler effect is related to relative velocity, at different times and for different satellites, there will be multiple iso-Doppler surfaces (or iso-relative velocity surfaces) and iso-Doppler change surfaces (or iso-relative acceleration surfaces). These surfaces are typically hyperboloids, conical surfaces, spheres, or hyperspheres. Finding the intersection points of these surfaces yields the receiver's position. Therefore, this embodiment of the invention receives carrier signals from multiple satellites at different times, extracts the Doppler information of each satellite at different times, and constructs a system of equations with time and Doppler frequency shift as known quantities, and satellite orbital parameters, satellite carrier frequency, and receiver coordinates as unknowns. Solving this system of equations yields the receiver's coordinates, thus completing the positioning process. Simultaneously, the satellite orbital parameters and carrier frequency can also be obtained for other uses.

[0035] In this embodiment of the invention, since there are a large number of satellites in the sky, with more than 6,000 low-Earth orbit (LEO) and medium-Earth orbit (MEO) communication satellites alone, and hundreds of visible satellites at any location, it is sufficient to complete non-cooperative positioning.

[0036] It should be noted that the known quantities involved in solving the receiver position in the embodiments of the present invention include:

[0037] tj : Observation time, j-th observation, j = 1, 2, ..., M.

[0038] Δf i,j Let be the Doppler shift received by the i-th satellite during the j-th observation, where i = 1, 2, ..., N, j = 1, 2, ..., M. N is the number of satellites observed, and M is the number of observations for each satellite.

[0039] c: speed of light.

[0040] The unknowns involved include:

[0041] r rec =(x rec ,y rec ,z rec ): The location (coordinates) of the receiver.

[0042] f i0 : The carrier frequency of the i-th satellite.

[0043] a i ,e i i i ,Ω i ,ω i M i : The orbital parameters of the i-th satellite.

[0044] For each satellite, there are 7 unknowns. If there are N satellites, there are a total of 7×N+3 unknowns. Therefore, if we want to obtain a solution to an overdetermined equation, the product of the number of observations M and the number of satellites N must be greater than the number of unknowns, that is, M×N>7×N+3. Generally, it can be assumed that the number of observations must be greater than 7.

[0045] Please see Figure 2 After receiving carrier signals from multiple satellites at different observation times, the specific steps for determining the receiver position include the following:

[0046] Step 1: Calculation of satellite position and velocity

[0047] According to Kepler's equations, the satellite's mean anomaly angle M... i (t j ) and the near-point angle E i (t j The relationship between them is:

[0048] M i (t j ) = E i (t j )-e i sin(E i (t j ))

[0049] Among them, M i (t j E is the angle of approach. i (t j ) is the angle closest to the point, e i This is the satellite's eccentricity. The angle of nearest point E. i (t j The eccentricity can be solved numerically (e.g., Newton's method). However, since the satellite parameters are unknowns, and the satellite reception time is short, and the satellites are mainly in LEO and MEO mode with small eccentricities, the following formula can be used for approximation:

[0050]

[0051] Satellite position calculation:

[0052] The satellite's instantaneous true perimeter angle v i (t j ) and the angle E of the nearest point i (t j The relationship between them is:

[0053]

[0054] Satellite position r i (t j )=(x i (t j) ,y i (t j ),z i (t j ))for:

[0055]

[0056] Among them, a i It is the satellite's semi-major axis, e i It is the eccentricity, v i (t j E is the instantaneous true perimeter angle. i (t j () is the near-point angle.

[0057] Satellite velocity calculation:

[0058] The satellite's speed v i (t j )=(v xi (t j) ,v yi (t j ),v zi (t j The derivative of the satellite's position with respect to time is:

[0059]

[0060] Step 2: Calculation of relative velocity

[0061] The receiver's position is r rec =(x rec ,y rec ,z rec The satellite's position is r. i (t j The satellite's velocity is v. i (t j If the relative position vector r between the receiver and the satellite is 0, then the relative position vector r between the receiver and the satellite is 0. i,rec (t j )for:

[0062] r i,rec (t j ) = r i (t j )-r rec

[0063] relative velocity v rel,i (t j () is the velocity component between the satellite and the receiver, along the line-of-sight direction between the receiver and the satellite:

[0064]

[0065] Step 3: Calculation of Doppler frequency shift

[0066] Based on relative velocity v rel,i (t j This allows us to calculate the Doppler frequency shift Δf. i,j :

[0067]

[0068] Where: c is the speed of light, f i0 It is the carrier frequency of the i-th satellite, v rel,i (t j () is the relative speed between the satellite and the receiver.

[0069] Step 4: Construct a system of equations

[0070] Based on the Doppler frequency shift formula, equations are constructed for each satellite at different observation times:

[0071]

[0072] In this equation, Δf i,j It is the known Doppler frequency shift r i (t j ) and vi (t j ) by orbital parameter θ i =(a i ,e i i i ,Ω i ,ω i M i ) indicates that f i0 It is the satellite carrier frequency, and the receiver's coordinates r rec =(x rec ,y rec ,z rec ) is the unknown quantity to be solved.

[0073] Step 5: Solve the system of equations

[0074] After obtaining the system of equations, since there are N satellites, each with Doppler shift data at M observation times, this system of equations consists of N×M equations. By solving this nonlinear system of equations, the three-dimensional coordinates r of the receiver can be obtained. rec =(x rec ,y rec ,z rec It can also obtain the orbital parameters and carrier frequencies of all satellites.

[0075] Common solution methods include the least squares method or Newton's method.

[0076] When solving a system of nonlinear equations using the least squares method, the error function to be minimized is as follows:

[0077]

[0078] When solving nonlinear equations using Newton's method, the receiver coordinates r are updated. rec The estimated value is calculated until the error is minimized.

[0079] It should be understood that any techniques not described in detail in this specification are considered conventional techniques or common knowledge in the field.

[0080] Based on the same inventive concept as the above-described method embodiments, this invention also provides an apparatus for arbitrary satellite non-cooperative positioning, comprising: a signal extraction module, used to extract Doppler information of each satellite at different observation times based on carrier signals received from multiple satellites at different observation times; and a signal solving module, used to construct a system of equations with time and Doppler frequency shift as known quantities and satellite orbital parameters, satellite carrier frequency and receiver coordinates as unknown quantities based on the extracted Doppler information, and solve the system of equations to obtain the coordinates of the receiver.

[0081] The device for non-cooperative positioning of arbitrary satellites provided in this invention receives signals from any satellite passing overhead, constructs a set of equations based on Doppler information from multiple satellites at different observation times, and calculates the position of the receiver. Thus, positioning is achieved without knowing the satellite orbital parameters, solving the navigation and positioning problem when GNSS is interfered with or suppressed.

[0082] Based on the same inventive concept as the above-described method embodiments, this invention also provides a receiver configured with the aforementioned arbitrary satellite non-cooperative positioning device. The receiver provided by this invention can achieve navigation and positioning using the aforementioned arbitrary satellite non-cooperative positioning device when GNSS is interfered with or suppressed, avoiding the cumulative error problem encountered when using inertial navigation for supplementary positioning.

[0083] Based on the same inventive concept as the above-described method embodiments, this invention also provides a receiver. Please refer to [link to relevant documentation]. Figure 3 It includes: a radio frequency front-end component for receiving satellite signals; a signal sampling and digitization component for sampling and digitizing the received satellite signals; a signal demodulation and frequency analysis component for processing the converted signals and extracting the satellite's Doppler information; and a positioning calculation component for constructing a system of equations with time and Doppler frequency shift as known quantities and satellite orbital parameters, satellite carrier frequency, and receiver coordinates as unknown quantities based on the extracted Doppler information, and solving the system of equations to obtain the receiver's coordinates.

[0084] The receiver provided in this embodiment of the invention adopts an SDR architecture. In this receiver system, the radio frequency front-end (RFFront-End) is used to receive satellite signals and convert them into signals suitable for further processing. The RFFront-End mainly includes an antenna, amplifier, filter, frequency converter, etc., to receive satellite signals in different frequency bands.

[0085] Specifically, the design of the RF front-end mainly includes antennas, low-noise amplifiers (LNAs), filters, mixers, etc., as detailed below:

[0086] Antenna: In order to receive signals from satellites, the receiver needs to be designed with an antenna that supports multiple commonly used frequency bands of satellites. A multi-frequency antenna can be used, enabling it to operate effectively in multiple frequency bands.

[0087] Low-noise amplifier: The low-noise amplifier performs initial amplification after receiving satellite signals to ensure signal quality. The LNA needs to be designed to be low-noise and wideband, capable of supporting multiple frequency bands.

[0088] Filters: Filters are used to select the frequency band of interest, and at the same time, they can suppress spurious signals to ensure the accuracy of subsequent signal processing.

[0089] Mixer: The mixer converts the received satellite signal frequencies from different frequency bands into intermediate frequency (IF) for subsequent digital processing.

[0090] In this receiver system, signal sampling and digitization (ADC / DSP) samples the analog signal obtained from the RF front end and converts it into a digital signal for processing via SDR.

[0091] Specifically, the received radio frequency signal is sampled by an analog-to-digital converter (ADC). Choosing an appropriate sampling rate is crucial to ensure that the signal is not distorted, especially when there is a large Doppler shift.

[0092] Sampling rate selection: According to the Nyquist theorem, the sampling rate should be higher than twice the signal bandwidth. For satellite signals, a sampling rate of tens to hundreds of MHz is typically chosen to ensure accurate capture of Doppler shift and other signal characteristics.

[0093] Dynamic range: A sufficiently large dynamic range is needed to capture signals from different satellites, which vary greatly in intensity.

[0094] In this receiver system, signal demodulation and frequency analysis (SDR processing) are performed in the digital domain, including filtering, frequency synchronization, Doppler estimation, phase tracking, etc., to extract frequency variations and signal characteristics received from the satellite.

[0095] The SDR section is responsible for processing the received signal, and the main steps include frequency synchronization and Doppler estimation.

[0096] Frequency synchronization: Due to the Doppler effect of satellites, the frequency of signals will shift. SDR receivers need to perform frequency synchronization to ensure that the signal frequency is correctly demodulated. The synchronization process typically involves automatic frequency control (AFC) or fine synchronization via the baseband portion of the signal.

[0097] Doppler estimation: The Doppler frequency shift is related to the satellite's velocity relative to the receiver. The receiver needs to estimate the Doppler frequency shift from the satellite signal. The estimation of the Doppler frequency shift can be achieved through spectral analysis of the received signal, sliding Fourier transform (FFT), or phase-locked loop (PLL) and frequency and phase tracking algorithms.

[0098] In this receiver system, the processor is used for positioning calculation and resolution. Based on the geometric relationship between the frequency offset of multiple satellites and the receiver's position, it calculates the receiver's three-dimensional position.

[0099] Once Doppler shift data from multiple satellites is obtained, the data can be handed over to the processor to form a system of equations. The system of equations is then solved using numerical processing methods to obtain the receiver's coordinates and satellite parameters, thus completing the positioning process.

[0100] Furthermore, while completing the positioning, it can also obtain satellite orbital parameters and carrier frequency for other uses.

[0101] In summary, this invention considers the Doppler effect that occurs when a receiver receives satellite signals during satellite operation. Since the Doppler effect is related to relative velocity, multiple iso-Doppler surfaces and iso-Doppler variation surfaces exist at different times and for different satellites. The receiver's position can be determined by finding the intersection of these surfaces. Therefore, this invention receives carrier signals from multiple satellites at different times, extracts the Doppler information of each satellite at different times, and constructs a system of equations with time and Doppler frequency shift as known quantities and satellite orbital parameters, satellite carrier frequency, and receiver coordinates as unknowns. Solving this system of equations yields the receiver's coordinates, thus completing the positioning. This invention can calculate the receiver's position without knowing the satellite's orbital parameters, enabling navigation and positioning when GNSS is interfered with or suppressed. Furthermore, this invention can obtain satellite orbital parameters and carrier frequency simultaneously with the receiver coordinates for other uses.

[0102] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices. The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be decomposed, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0103] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for non-cooperative positioning of arbitrary satellites, characterized in that, The method does not require prior acquisition of satellite orbit parameters and includes: The relationship between the number of observations M and the number of satellites N is set to satisfy: M×N > 7×N+3. Based on the set number of observations, carrier signals from multiple satellites are received at different observation times. Based on carrier signals received from multiple satellites at different observation times, Doppler information of each satellite at different observation times is extracted, including: calculating the position and velocity of each satellite at different observation times; calculating the relative velocity between each satellite and the receiver at different observation times; and calculating the Doppler frequency shift of each satellite at different observation times based on the relative velocity. Based on the extracted Doppler information, a system of equations is constructed with time and Doppler frequency shift as known quantities and satellite orbital parameters, satellite carrier frequency and receiver coordinates as unknown quantities. Solve the system of equations to obtain the coordinates of the receiver.

2. The method for non-cooperative positioning of any satellite according to claim 1, characterized in that, After obtaining the Doppler frequency shift of each of the aforementioned satellites at different observation times, the method also includes: Based on the Doppler frequency shift formula, equations are constructed for each satellite at different observation times; A set of equations is formed based on the equations of multiple satellites at different observation times.

3. The method for non-cooperative positioning of any satellite according to claim 1 or 2, characterized in that, Solving the system of equations includes using the least squares method or Newton's method.

4. An apparatus for non-cooperative positioning of any satellite, used to implement the method according to any one of claims 1-3, characterized in that, The device includes components that do not require prior acquisition of satellite orbit parameters. The signal extraction module is used to extract the Doppler information of each satellite at different observation times based on the carrier signals received from multiple satellites at different observation times. The signal solving module is used to construct a system of equations with time and Doppler frequency shift as known quantities and satellite orbital parameters, satellite carrier frequency and receiver coordinates as unknown quantities based on the extracted Doppler information, and solve the system of equations to obtain the coordinates of the receiver.

5. A receiver, characterized in that, The device is equipped with the non-cooperative positioning device for any satellite as described in claim 4.

6. A receiver, relying on the method of any one of claims 1-3, characterized in that, Without needing to obtain satellite orbit parameters in advance, the receiver includes: a radio frequency front-end component for receiving satellite signals; a signal sampling and digitization component for sampling and digitizing the received satellite signals; a signal demodulation and frequency analysis component for processing the converted signal and extracting the satellite's Doppler information; and a positioning calculation component for constructing a system of equations based on the extracted Doppler information, with time and Doppler frequency shift as known quantities and satellite orbit parameters, satellite carrier frequency, and receiver coordinates as unknown quantities, and solving the system of equations to obtain the receiver's coordinates.

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