Method and apparatus for carrier Doppler open-loop estimation of low-Earth orbit satellite communication and navigation fusion signals

Abstract

This application relates to a method and apparatus for open-loop estimation of carrier Doppler frequency in low-Earth orbit (LEO) satellite navigation signals. The method includes: symbol stripping of the satellite navigation signal to obtain a single-tone signal; generating local signals at redshift and blueshift frequencies based on the single-tone signal and initial estimates of the carrier Doppler frequency of the satellite navigation signal; performing digital down-conversion and coherent integration accumulation on the single-tone signal in the redshift and blueshift branches respectively, to obtain a redshift correlator and a blueshift correlator; constructing a normalized carrier discriminator based on the redshift and blueshift correlators; and updating the initial estimate of the carrier Doppler frequency of the satellite navigation signal using the normalized carrier discriminator to obtain the open-loop estimate of the carrier Doppler frequency of the satellite navigation signal. This method can reduce the computational complexity caused by DFT or FFT operations.

Description

Technical Field

[0001] This application relates to the field of satellite navigation technology, and in particular to a method and apparatus for carrier Doppler open-loop estimation of low-orbit satellite communication and navigation fusion signals. Background Technology

[0002] Compared to the medium and high orbit satellites commonly used in traditional satellite navigation constellations, low-Earth orbit (LEO) satellites offer advantages such as reduced signal attenuation, faster satellite movement, and deeper integration of communication and navigation. These advantages effectively compensate for the shortcomings of medium and high orbit satellites, such as low signal power and low message rate. Although the coverage area of ​​a single LEO satellite is smaller than that of a medium or high orbit satellite, and the ability to achieve multiple global coverage requires a larger constellation size, users of satellite communication systems generally do not have a strong need for multiple satellite coverage. Based on these characteristics, in the initial stages of LEO navigation satellite constellation construction, or when conducting integrated communication and navigation design based on LEO communication constellations, a Doppler positioning-based technology is typically adopted. This allows for the provision of navigation, positioning, and timing services to users even when the number of visible satellites is insufficient. Satellite Timing and Location (STL) signals are navigation enhancement signals broadcast by the second-generation Iridium NEXT LEO communication system. They consist of a single-carrier signal, a spread spectrum signal, and a data signal, with a duration of approximately 6.5–20.32 ms. They primarily employ a Doppler system to provide positioning and timing services to users. To address the issue of insufficient satellite coverage and meet the requirements of integrated communication and navigation design, low-Earth orbit (LEO) satellite systems will broadcast short burst signals similar to STL signals. Therefore, the accuracy of high-precision Doppler frequency measurement for these short burst signals will directly impact the navigation, positioning, and timing performance of LEO satellites.

[0003] Currently, there are two main methods for carrier Doppler estimation of satellite navigation signals: The first type involves differentiating the carrier phase estimates of two consecutive signal segments. Examples include cross-discriminators, decision-oriented discriminators, and four-quadrant arctangent discriminators, primarily used in frequency-locked loops for continuous signal reception. This method requires truncating short burst signals into two segments, shortening the correlator's integration time and increasing the impact of thermal noise jitter on carrier frequency estimation. The second type is based on Discrete Fourier Transform (DFT) interpolation, which can be rapidly processed using Fast Fourier Transform (FFT). Examples include the Rife frequency estimation method using the maximum and second-largest DFT amplitude values, the Quinn frequency estimation method using the maximum DFT amplitude and its nearest neighbors, and the truncated sine frequency estimation method based on the extreme values ​​of the DFT coefficients. Among them, the truncated string method mainly utilizes the peak spectrum of DFT and the spectrum of 0.5 frequency sampling intervals on the left and right. It can make the estimation accuracy close to the Cramer-Rao lower limit of short-time signal frequency estimation through iteration, but it has high computational complexity. Summary of the Invention

[0004] Therefore, it is necessary to provide a method and apparatus for carrier Doppler open-loop estimation of low-orbit satellite communication and navigation fusion signals that can reduce the computational complexity caused by DFT or FFT operations, in order to address the above-mentioned technical problems.

[0005] A method for carrier Doppler open-loop estimation of low-Earth orbit satellite communication and navigation fusion signals, the method comprising:

[0006] Acquire satellite navigation signals; perform symbol stripping on the satellite navigation signals to obtain single-tone signals; generate local signals with redshift and blueshift frequencies based on the single-tone signals and the initial estimate of the carrier Doppler frequency of the satellite navigation signals;

[0007] In the red-shift branch and the blue-shift branch, the single-tone signal is digitally down-converted according to the local signal of the red-shift frequency and the local signal of the blue-shift frequency, respectively, to obtain the red-shift digital down-converted signal and the blue-shift digital down-converted signal. Then, the red-shift digital down-converted signal and the blue-shift digital down-converted signal are coherently integrated and accumulated to obtain the red-shift correlator and the blue-shift correlator.

[0008] A normalized carrier frequency discriminator is constructed based on the redshift correlator and the blueshift correlator; the initial estimate of the carrier Doppler frequency of the satellite navigation signal is updated using the normalized carrier frequency discriminator to obtain the open-loop estimate of the carrier Doppler frequency of the satellite navigation signal.

[0009] In one embodiment, symbol stripping is performed on the satellite navigation signal to obtain a single-tone signal, including:

[0010] Symbol stripping of the satellite navigation signal yields a single-tone signal.

[0011] r1(t)=exp(j2πf0t)

[0012] Where f0 represents the actual carrier frequency of the received satellite navigation signal, and t represents the time when the signal is received.

[0013] In one embodiment, generating a local signal with a redshift frequency and a local signal with a blueshift frequency based on an initial estimate of the carrier Doppler frequency of the single-tone signal and the satellite navigation signal includes:

[0014] The local signal with redshift frequency is generated based on the initial estimate of the carrier Doppler frequency of the single-tone signal and the satellite navigation signal.

[0015]

[0016] Where f0 represents the actual carrier frequency of the received satellite navigation signal, and t represents the time of signal reception. This represents the initial estimate of the carrier Doppler frequency of the satellite navigation signal. Indicates the redshift carrier frequency;

[0017] The local signal with blue-shift frequency is generated based on the initial estimate of the carrier Doppler frequency of the single-tone signal and the satellite navigation signal.

[0018]

[0019] in, This indicates the redshift carrier frequency.

[0020] In one embodiment, the single-tone signal is digitally down-converted in the red-shift branch and the blue-shift branch according to the local signal at the red-shift frequency and the local signal at the blue-shift frequency, respectively, to obtain the red-shift digitally down-converted signal and the blue-shift digitally down-converted signal, including:

[0021] In the redshift branch, the single-tone signal is digitally down-converted based on the local signal at the redshift frequency, resulting in the redshifted digitally down-converted signal.

[0022]

[0023] Where f0 represents the actual carrier frequency of the received satellite navigation signal, and t represents the time of signal reception. This represents the initial estimate of the carrier Doppler frequency of the satellite navigation signal. Indicates the redshift carrier frequency;

[0024] In the blue-shift branch, the single-tone signal is digitally down-converted based on the local signal of the blue-shift frequency, resulting in the blue-shift digitally down-converted signal.

[0025]

[0026] in, This indicates the redshift carrier frequency.

[0027] In one embodiment, coherent integration and accumulation are performed on the red-shifted digital down-converted signal and the blue-shifted digital down-converted signal to obtain a red-shift correlator and a blue-shift correlator, including:

[0028] The redshift correlator is obtained by coherently integrating and accumulating the signal after digital down-conversion.

[0029]

[0030] Among them, T coh Indicates the coherent integration time;

[0031] The blue-shift correlator is obtained by coherently integrating and accumulating the signal after digital down-conversion.

[0032]

[0033] In one embodiment, a normalized carrier discriminator is constructed based on the redshift correlator and the blueshift correlator, including:

[0034] A normalized carrier frequency discriminator is constructed based on the redshift correlator and the blueshift correlator.

[0035]

[0036] Where W1 represents the redshift correlator and W2 represents the blueshift correlator.

[0037] In one embodiment, the initial estimate of the carrier Doppler frequency of the satellite navigation signal is updated using a normalized carrier discriminator to obtain the open-loop estimate of the carrier Doppler frequency of the satellite navigation signal, and the method further includes:

[0038] The initial estimate of the carrier Doppler frequency of the satellite navigation signal is updated using a normalized carrier discriminator, resulting in the open-loop estimate of the carrier Doppler frequency of the satellite navigation signal.

[0039]

[0040] Where D represents the normalized carrier frequency discriminator, This represents the initial estimate of the carrier Doppler frequency.

[0041] A low-Earth orbit satellite communication and navigation fusion signal carrier Doppler open-loop estimation device, the device comprising:

[0042] The frequency signal generation module is used to acquire satellite navigation signals; to strip symbols from the satellite navigation signals to obtain single-tone signals; and to generate local signals with redshift and blueshift frequencies based on the single-tone signals and the initial estimate of the carrier Doppler frequencies of the satellite navigation signals.

[0043] The correlator construction module is used to digitally down-convert the single-tone signal in the red-shift branch and the blue-shift branch according to the local signal of the red-shift frequency and the local signal of the blue-shift frequency, respectively, to obtain the red-shift digital down-converted signal and the blue-shift digital down-converted signal. Then, the red-shift digital down-converted signal and the blue-shift digital down-converted signal are coherently integrated and accumulated to obtain the red-shift correlator and the blue-shift correlator.

[0044] The estimation update module is used to construct a normalized carrier frequency discriminator based on the redshift correlator and the blueshift correlator; and to update the initial estimate of the carrier Doppler frequency of the satellite navigation signal using the normalized carrier frequency discriminator to obtain the carrier Doppler open-loop estimate of the satellite navigation signal.

[0045] The aforementioned open-loop estimation method and apparatus for carrier Doppler frequency estimation of low-Earth orbit satellite communication and navigation fusion signals, constructed in this application, utilizes a red-blue frequency shift correlator and a frequency discriminator. The correlator performs operations such as stripping the signal modulation symbols, digital down-conversion, and correlation integration accumulation. The discriminator incorporates a normalized carrier frequency discriminator. This approach achieves accurate estimation of the carrier Doppler frequency while effectively reducing the computational complexity of frequency estimation, with the estimation accuracy approaching the theoretical limit of Cramer-Rao. Throughout the implementation, only the local carrier frequency of the classical receiver is changed, and a carrier frequency discriminator is added. Complex operations such as matrix inversion and eigenvalue decomposition are not involved. Therefore, this application is simple to implement, requires minimal computation, and is very convenient to carry out. It represents an improvement on the truncated sine wave frequency estimation method, avoiding the use of complex DFT or FFT operations without affecting frequency estimation accuracy. It can be directly applied to carrier Doppler frequency estimation for both short bursts and continuous signals. Attached Figure Description

[0046] Figure 1 This is a flowchart illustrating a low-orbit satellite communication and navigation fusion signal carrier Doppler open-loop estimation method in one embodiment;

[0047] Figure 2 Here is a block diagram of a carrier Doppler frequency open-loop estimator in one embodiment;

[0048] Figure 3 This is a schematic diagram of the correlator output value versus frequency deviation in one embodiment;

[0049] Figure 4This is a schematic diagram of the frequency discrimination curve of the carrier Doppler frequency open-loop estimator in another embodiment;

[0050] Figure 5 This is a curve showing the variation of the frequency discriminator normalization coefficient with the red-blue frequency shift interval in one embodiment;

[0051] Figure 6 The image shows a curve illustrating the variation of carrier-Doppler frequency estimation accuracy with signal-carrier-to-noise ratio in one embodiment.

[0052] Figure 7 This is a structural block diagram of a low-orbit satellite communication and navigation fusion signal carrier Doppler open-loop estimation device in one embodiment. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0054] In one embodiment, such as Figure 1 As shown, a method for carrier Doppler open-loop estimation of low-Earth orbit satellite communication and navigation fusion signals is provided, including the following steps:

[0055] Step 102: Acquire satellite navigation signals; perform symbol stripping on the satellite navigation signals to obtain single-tone signals; generate local signals with redshift frequency and local signals with blueshift frequency based on the initial estimate of the carrier Doppler frequency of the single-tone signals and the satellite navigation signals.

[0056] For satellite navigation signals, symbols such as message, secondary code, pseudo-random code, and subcarriers are typically modulated on the radio frequency carrier, enabling functions such as information transmission, improved ranging performance, spectrum spreading, and spectrum splitting. First, it is necessary to strip the various symbols c(t) modulated on the receiver's digital intermediate frequency signal r(t) = c(t)exp(j2πf0t), so that the received signal is despread into a single-tone signal r1(t) = exp(j2πf0t), where f0 is the actual carrier frequency of the received signal.

[0057] Step 104: In the red-shift branch and the blue-shift branch, the single-tone signal is digitally down-converted according to the local signal of the red-shift frequency and the local signal of the blue-shift frequency, respectively, to obtain the red-shift digital down-converted signal and the blue-shift digital down-converted signal. Then, the red-shift digital down-converted signal and the blue-shift digital down-converted signal are coherently integrated and accumulated to obtain the red-shift correlator and the blue-shift correlator.

[0058] Assume the initial value of the received signal carrier frequency estimation is Digital down-conversion local signals that generate red-shift and blue-shift frequencies respectively. and The redshift carrier frequency is Blue shift carrier frequency is The carrier frequency interval between redshift and blueshift is 2Δf.

[0059] Step 106: Construct a normalized carrier frequency discriminator based on the redshift correlator and the blueshift correlator; use the normalized carrier frequency discriminator to update the initial estimate of the carrier Doppler frequency of the satellite navigation signal to obtain the carrier Doppler open-loop estimate of the satellite navigation signal.

[0060] A normalized carrier frequency discriminator is constructed based on redshift and blueshift correlators. The initial estimate of the carrier Doppler frequency of the satellite navigation signal is updated using the normalized carrier frequency discriminator. Only the local carrier frequency of the classical receiver is changed, and a carrier frequency discriminator is added. It does not involve complex operations such as matrix inversion and eigenvalue decomposition. Therefore, this invention is simple to implement, has a small computational load, reduces computational complexity, and is very convenient to implement. It can be directly used for carrier Doppler frequency estimation of short bursts and continuous signals.

[0061] In the aforementioned open-loop estimation method for carrier Doppler frequencies of low-Earth orbit satellite communication and navigation fusion signals, this application constructs a red-blue frequency shift correlator and a frequency discriminator. The correlator performs operations such as stripping the signal modulation symbols, digital down-conversion, and correlation integration accumulation. The discriminator designs a normalized carrier frequency discriminator, which enables accurate estimation of the carrier Doppler frequency while effectively reducing the computational complexity of frequency estimation. Furthermore, the frequency estimation accuracy approaches the theoretical limit of Cramer-Rao. Throughout the implementation process, only the local carrier frequency of the classical receiver is changed, and a carrier frequency discriminator is added. Complex operations such as matrix inversion and eigenvalue decomposition are not involved. Therefore, this application is simple to implement, has low computational load, and is very convenient to implement. It is an improvement on the truncated sine frequency estimation method, which can avoid using complex DFT or FFT operations without affecting the frequency estimation accuracy. It can be directly used for carrier Doppler frequency estimation of short bursts and continuous signals.

[0062] In one embodiment, symbol stripping is performed on the satellite navigation signal to obtain a single-tone signal, including:

[0063] Symbol stripping of the satellite navigation signal yields a single-tone signal.

[0064] r1(t)=exp(j2πf0t)

[0065] Where f0 represents the actual carrier frequency of the received satellite navigation signal, and t represents the time when the signal is received.

[0066] In one embodiment, generating a local signal with a redshift frequency and a local signal with a blueshift frequency based on an initial estimate of the carrier Doppler frequency of the single-tone signal and the satellite navigation signal includes:

[0067] The local signal with redshift frequency is generated based on the initial estimate of the carrier Doppler frequency of the single-tone signal and the satellite navigation signal.

[0068]

[0069] Where f0 represents the actual carrier frequency of the received satellite navigation signal, and t represents the time of signal reception. This represents the initial estimate of the carrier Doppler frequency of the satellite navigation signal. Indicates the redshift carrier frequency;

[0070] The local signal with blue-shift frequency is generated based on the initial estimate of the carrier Doppler frequency of the single-tone signal and the satellite navigation signal.

[0071]

[0072] in, This indicates the redshift carrier frequency.

[0073] In one embodiment, the single-tone signal is digitally down-converted in the red-shift branch and the blue-shift branch according to the local signal at the red-shift frequency and the local signal at the blue-shift frequency, respectively, to obtain the red-shift digitally down-converted signal and the blue-shift digitally down-converted signal, including:

[0074] In the redshift branch, the single-tone signal is digitally down-converted based on the local signal at the redshift frequency, resulting in the redshifted digitally down-converted signal.

[0075]

[0076] Where f0 represents the actual carrier frequency of the received satellite navigation signal, and t represents the time of signal reception. This represents the initial estimate of the carrier Doppler frequency of the satellite navigation signal. Indicates the redshift carrier frequency;

[0077] In the blue-shift branch, the single-tone signal is digitally down-converted based on the local signal of the blue-shift frequency, resulting in the blue-shift digitally down-converted signal.

[0078]

[0079] in, This indicates the redshift carrier frequency.

[0080] In one embodiment, coherent integration and accumulation are performed on the red-shifted digital down-converted signal and the blue-shifted digital down-converted signal to obtain a red-shift correlator and a blue-shift correlator, including:

[0081] The redshift correlator is obtained by coherently integrating and accumulating the signal after digital down-conversion.

[0082]

[0083] Among them, T coh Indicates the coherent integration time;

[0084] The blue-shift correlator is obtained by coherently integrating and accumulating the signal after digital down-conversion.

[0085]

[0086] In one embodiment, a normalized carrier discriminator is constructed based on the redshift correlator and the blueshift correlator, including:

[0087] A normalized carrier frequency discriminator is constructed based on the redshift correlator and the blueshift correlator.

[0088]

[0089] Where W1 represents the redshift correlator and W2 represents the blueshift correlator.

[0090] In one embodiment, the initial estimate of the carrier Doppler frequency of the satellite navigation signal is updated using a normalized carrier discriminator to obtain the open-loop estimate of the carrier Doppler frequency of the satellite navigation signal, and the method further includes:

[0091] The initial estimate of the carrier Doppler frequency of the satellite navigation signal is updated using a normalized carrier discriminator, resulting in the open-loop estimate of the carrier Doppler frequency of the satellite navigation signal.

[0092]

[0093] Where D represents the normalized carrier frequency discriminator, This represents the initial estimate of the carrier Doppler frequency.

[0094] In a specific embodiment, Figure 2 This is a block diagram of the carrier Doppler frequency open-loop estimator designed in this application. The receiver's digital intermediate frequency signal r(t) is stripped of various modulation symbols c(t) to obtain a single-tone signal r1(t). Local carrier modulation generates redshift carrier frequencies of... and the blue-shift carrier frequency is The digital down-converted local signals s1(t) and s2(t) are used to perform digital down-conversion operations on signal r1(t) in the red-shift and blue-shift branches to obtain w1(t) and w2(t) respectively. The signals w1(t) and w2(t) are then subjected to coherent integration and accumulation operations to obtain W1 and W2. Finally, a normalized carrier frequency discriminator is constructed to perform frequency identification.

[0095] Figure 3 The correlation curves for the baseline correlator, blue-shift correlator, and red-shift correlator are given, and the simulation is set with a coherence integration time T. coh The time is 1ms, and the normalized maximum correlation value is 1. The local signal carrier frequency of the reference correlator is... Frequency deviation is The local signal carrier frequency of the blue shift correlator is The local signal carrier frequency of the redshift correlator is Here, the red-blue frequency shift interval Δf is set to 500Hz. The theoretical correlation function of the reference correlator is R(f) d )=|sinc(f d T coh )|, where sinc(·) represents the Singer function.

[0096] Figure 4 Frequency discrimination curves of the carrier Doppler frequency open-loop estimator under different red-blue frequency shift intervals are presented. The simulation is set with a coherent integration time T. coh The red-blue frequency shift interval Δf is 1ms, with values ​​of 50Hz, 250Hz, 500Hz, 750Hz, and 950Hz. It can be seen that the larger the red-blue frequency shift interval Δf, the smaller the corresponding monotonic frequency discrimination interval, ranging from [Δf-1 / T]. coh 1 / T coh -Δf], where monotonicity refers to the frequency discrimination function increasing monotonically with frequency deviation. For example, for a 50Hz red-blue frequency shift interval, the monotonic frequency discrimination interval is [-950Hz, 950Hz]; for a 500Hz red-blue frequency shift interval, the monotonic frequency discrimination interval is [-500Hz, 500Hz]; and for a 950Hz red-blue frequency shift interval, the monotonic frequency discrimination interval is [-50Hz, 50Hz].

[0097] Figure 5 The curves showing the variation of the normalization coefficients of the frequency discriminator with the red-blue frequency shift interval are presented. The simulation is set with a coherent integration time T. coh The red-blue frequency shift interval Δf is 1 ms, traversing from 50 Hz to 950 Hz with a traversal interval of 50 Hz. The normalization coefficient of the frequency discriminator can be approximated as the reciprocal of the slope of the frequency discrimination curve at the red-blue frequency shift interval Δf = 0. It can be seen that when the red-blue frequency shift interval Δf is 50 Hz, the normalization coefficient k is 6069; when the red-blue frequency shift interval Δf is 500 Hz, the normalization coefficient k is 500; and when the red-blue frequency shift interval Δf is 950 Hz, the normalization coefficient k is 48.

[0098] Figure 6 The curves of carrier Doppler frequency estimation accuracy versus signal-to-noise ratio are presented under different coherent integration times. The simulation is set with the red-blue frequency shift interval Δf = 1 / (2T).coh The normalization coefficient of the frequency discriminator is k = 1 / (2T). coh Coherent integration time T coh We take values ​​of 1ms, 10ms, and 20ms respectively. For a duration of T... coh For a finite-length signal, the lower bound of the Cramer-Rao expression for frequency estimation accuracy is: Where C / N0 represents the carrier-to-noise ratio (CNR) of the received signal. It can be seen that the higher the CNR of the received signal, the higher the estimation accuracy of the carrier Doppler frequency; the longer the coherent integration time, the higher the frequency estimation accuracy; the frequency estimation accuracy under the simulation settings is close to the lower limit of the Cramer-Rao theory. For a received signal CNR of 40 dB-Hz, the frequency estimation accuracies corresponding to different coherent integration times are 137.1 Hz, 4.0 Hz, and 1.4 Hz, respectively; for a received signal CNR of 70 dB-Hz, the frequency estimation accuracies corresponding to different coherent integration times are 4.0 Hz, 0.12 Hz, and 0.044 Hz, respectively.

[0099] It should be understood that, although Figure 1 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0100] In one embodiment, such as Figure 7 As shown, a carrier Doppler open-loop estimation device for low-Earth orbit satellite communication and navigation fusion signals is provided, comprising: a frequency signal generation module 702, a correlator construction module 704, and an estimate update module 706, wherein:

[0101] The frequency signal generation module 702 is used to acquire satellite navigation signals; to strip symbols from the satellite navigation signals to obtain single-tone signals; and to generate local signals with redshift frequencies and blueshift frequencies based on the single-tone signals and the initial estimates of the carrier Doppler frequencies of the satellite navigation signals.

[0102] The correlator construction module 704 is used to perform digital down-conversion on the single-tone signal in the red-shift branch and the blue-shift branch according to the local signal of the red-shift frequency and the local signal of the blue-shift frequency, respectively, to obtain the red-shift digital down-converted signal and the blue-shift digital down-converted signal. Then, the red-shift digital down-converted signal and the blue-shift digital down-converted signal are coherently integrated and accumulated to obtain the red-shift correlator and the blue-shift correlator.

[0103] The estimation update module 706 is used to construct a normalized carrier frequency discriminator based on the redshift correlator and the blueshift correlator; and to update the initial estimate of the carrier Doppler frequency of the satellite navigation signal using the normalized carrier frequency discriminator to obtain the carrier Doppler open-loop estimate of the satellite navigation signal.

[0104] Specific limitations regarding the LEO satellite communication and navigation fusion signal carrier Doppler open-loop estimation device can be found in the limitations of the LEO satellite communication and navigation fusion signal carrier Doppler open-loop estimation method described above, and will not be repeated here. Each module in the aforementioned LEO satellite communication and navigation fusion signal carrier Doppler open-loop estimation device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independently of the processor in a computer device, or stored in software in the memory of a computer device, so that the processor can call and execute the operations corresponding to each module.

[0105] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0106] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for low earth orbit satellite navigation and communication signal carrier Doppler open loop estimation, characterized in that, The method comprises: acquiring a satellite navigation signal; performing symbol stripping on the satellite navigation signal to obtain a single-tone signal; generating a red-shifted frequency local signal and a blue-shifted frequency local signal according to the single-tone signal and an initial estimation value of a carrier Doppler frequency of the satellite navigation signal; performing digital down-conversion on the single-tone signal according to the red-shifted frequency local signal and the blue-shifted frequency local signal in a red-shift branch and a blue-shift branch respectively to obtain a red-shifted digital down-converted signal and a blue-shifted digital down-converted signal, and then performing coherent integration and accumulation on the red-shifted digital down-converted signal and the blue-shifted digital down-converted signal to obtain a red-shift correlator and a blue-shift correlator; constructing a normalized carrier discriminator according to the red-shift correlator and the blue-shift correlator; and updating the initial estimation value of the carrier Doppler frequency of the satellite navigation signal by using the normalized carrier discriminator to obtain an open-loop estimation value of the carrier Doppler frequency of the satellite navigation signal.

2. The method of claim 1, wherein, performing symbol stripping on the satellite navigation signal to obtain a single-tone signal comprises: performing symbol stripping on the satellite navigation signal to obtain a single-tone signal is wherein, denotes the real carrier frequency of the received satellite navigation signal, t denotes the time instant of the received signal.

3. The method of claim 1, wherein, generating a red-shifted frequency local signal and a blue-shifted frequency local signal according to the single-tone signal and an initial estimation value of a carrier Doppler frequency of the satellite navigation signal comprises: generating a red-shifted frequency local signal according to the single-tone signal and the initial estimation value of the carrier Doppler frequency of the satellite navigation signal is wherein, denotes the true carrier frequency of the received satellite navigation signal, t denotes the time of reception of the signal, denotes the initial estimate of the carrier Doppler frequency of the satellite navigation signal, denotes the red-shifted carrier frequency; generating a blue-shifted frequency local signal according to the single-tone signal and the initial estimation value of the carrier Doppler frequency of the satellite navigation signal is wherein represents the blue-shifted carrier frequency.

4. The method according to any one of claims 1 to 3, characterized in that, performing digital down-conversion on the single-tone signal according to the red-shifted frequency local signal and the blue-shifted frequency local signal in a red-shift branch and a blue-shift branch respectively to obtain a red-shifted digital down-converted signal and a blue-shifted digital down-converted signal comprises: performing digital down-conversion on the single-tone signal according to the red-shifted frequency local signal in a red-shift branch to obtain a red-shifted digital down-converted signal is wherein, denotes the true carrier frequency of the received satellite navigation signal, t denotes the time of reception of the signal, denotes the initial estimate of the carrier Doppler frequency of the satellite navigation signal, denotes the red-shifted carrier frequency; performing digital down-conversion on the single-tone signal according to the blue-shifted frequency local signal in a blue-shift branch to obtain a blue-shifted digital down-converted signal is wherein represents the blue-shifted carrier frequency.

5. The method of claim 4, wherein, performing coherent integration and accumulation on the red-shifted digital down-converted signal and the blue-shifted digital down-converted signal to obtain a red-shift correlator and a blue-shift correlator comprises: performing coherent integration and accumulation on the red-shifted digital down-converted signal to obtain a red-shift correlator is wherein denotes the coherent integration time; performing coherent integration and accumulation on the blue-shifted digital down-converted signal to obtain a blue-shift correlator is 。 6. The method of claim 1, wherein, constructing a normalized carrier discriminator according to the red-shift correlator and the blue-shift correlator comprises: constructing a normalized carrier discriminator according to the red-shift correlator and the blue-shift correlator is wherein represents a red-shifted correlator, represents a blue-shifted correlator.

7. The method of claim 1, wherein, updating the initial estimation value of the carrier Doppler frequency of the satellite navigation signal by using the normalized carrier discriminator to obtain an open-loop estimation value of the carrier Doppler frequency of the satellite navigation signal further comprises: updating the initial estimation value of the carrier Doppler frequency of the satellite navigation signal by using the normalized carrier discriminator to obtain an open-loop estimation value of the carrier Doppler frequency of the satellite navigation signal is wherein denotes a normalized carrier discriminator, denotes a carrier Doppler frequency initial estimate. 8.A device for low earth orbit satellite navigation and communication signal carrier Doppler open loop estimation, characterized in that, The device comprises: The frequency signal generation module is configured to acquire a satellite navigation signal; perform symbol stripping on the satellite navigation signal to obtain a single-tone signal; and generate a red-shift frequency local signal and a blue-shift frequency local signal according to the single-tone signal and an initial estimation value of a carrier Doppler frequency of the satellite navigation signal; The correlator construction module is configured to perform digital down-conversion on the single-tone signal according to the red-shift frequency local signal and the blue-shift frequency local signal in the red-shift branch and the blue-shift branch respectively to obtain a red-shift digital down-converted signal and a blue-shift digital down-converted signal, and then perform coherent integration and accumulation on the red-shift digital down-converted signal and the blue-shift digital down-converted signal to obtain a red-shift correlator and a blue-shift correlator. The estimation value update module is configured to construct a normalized carrier discriminator according to the red-shift correlator and the blue-shift correlator; and update the initial estimation value of the carrier Doppler frequency of the satellite navigation signal by using the normalized carrier discriminator to obtain an open-loop estimation value of the carrier Doppler frequency of the satellite navigation signal.

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