High-precision Doppler estimation method based on multi-symbol joint processing

Abstract

A high-precision Doppler estimation method based on multi-symbol joint processing belongs to the technical field of satellite navigation, and comprises the following steps: performing signal arrival detection and carrier Doppler initial estimation by using a pilot frequency of a low-orbit navigation signal; removing carrier coarse frequency offset, and performing matched filtering; calculating a symbol optimal sampling moment by using a synchronous code of the low-orbit navigation signal; acquiring an optimal sampling point of the signal to form a to-be-estimated sequence; performing multi-symbol joint carrier phase measurement; carrier phase continuity detection and correction are carried out; and performing Doppler estimation based on the obtained continuous carrier phase to obtain a final Doppler estimation result. According to the high-precision Doppler estimation method based on multi-symbol joint processing, a high-precision carrier Doppler estimation result can still be obtained when a navigation message of a low-orbit navigation signal cannot be normally demodulated.

Description

Technical Field

[0001] The invention relates to a high-precision Doppler estimation method based on multi-symbol joint processing, and belongs to the technical field of satellite navigation. Background Art

[0002] GNSS has become the most basic and important means for people to obtain spatiotemporal information. With the advancement of technology, global navigation satellite systems are becoming increasingly indispensable to production and life. However, existing GNSS systems transmit navigation signals in an orbit approximately 20,000 kilometers above the Earth, and the signal power reaching the ground is limited. In military or other critical scenarios, maintaining spatiotemporal information in complex wireless environments is crucial, so methods beyond existing GNSS are needed to ensure the accuracy, availability, and integrity of navigation operations. Low-orbit communication satellite integrated navigation positioning refers to navigation by integrating navigation signals into the downlink communication radio signals of a low-orbit communication satellite constellation. Leveraging the large number of satellites in the low-orbit communication constellation and their close proximity to the ground (approximately 1,000 km), it can serve as a backup and enhancement to the existing navigation system, greatly improving the availability and survivability of satellite navigation positioning in complex conditions.

[0003] The navigation signals integrated into low-orbit communication constellations (hereinafter referred to as LEO navigation signals) are typically burst signals, lasting from tens to tens of milliseconds, and are transmitted using time division, code division, or frequency division. Doppler positioning is an important method for navigation and positioning using LEO navigation signals. The accuracy of Doppler positioning is very sensitive to Doppler error, and even small Doppler estimation errors can significantly impact the final positioning accuracy. Therefore, obtaining high-precision Doppler from the limited-length LEO navigation signals becomes crucial. Summary of the Invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and provide a high-precision Doppler estimation method based on multi-symbol joint processing, so as to solve the problem of obtaining a high-precision carrier Doppler estimation result when the navigation message of the low-orbit navigation signal cannot be demodulated normally.

[0005] The technical solution of the present invention is: a high-precision Doppler estimation method based on multi-symbol joint processing, comprising:

[0006] The pilot signal of the low-orbit navigation signal is used to detect the signal arrival and estimate the carrier Doppler, and obtain the preliminary carrier Doppler estimation result;

[0007] Remove the carrier coarse frequency offset of the initial carrier Doppler estimation result, perform matched filtering, and obtain the baseband signal after matched filtering;

[0008] The optimal sampling time of the baseband signal after matched filtering is calculated using the synchronization code of the low-orbit navigation signal;

[0009] Based on the optimal sampling moment of the symbol, the optimal sampling point of the baseband signal after matched filtering is obtained to form a sequence to be estimated;

[0010] Performing multi-symbol joint carrier phase measurement on the sequence to be estimated to obtain a measurement result;

[0011] Performing carrier phase continuity detection and correction on the measurement result to obtain a corrected continuous carrier phase;

[0012] Doppler estimation is performed based on the corrected continuous carrier phase to obtain the final estimation result, so that even when the navigation message of the low-orbit navigation signal cannot be demodulated normally, the carrier Doppler estimation result that meets the preset accuracy requirements can still be obtained.

[0013] Furthermore, the signal arrival detection and carrier Doppler initial estimation include: designing multiple parallel detection channels, each channel including a filter module, an FFT module, a signal frequency domain arrival detection module and a carrier Doppler initial estimation module, the filter module obtains an input signal of a possible frequency band and transforms it through the FFT module, and then detects and estimates it through the signal frequency domain arrival detection module and the carrier Doppler initial estimation module respectively; the frequency bands of multiple detection channels are combined to form a total frequency band that can cover all possible frequency bands of the input signal.

[0014] Furthermore, when the number of detection channels is three, the filter of the first detection channel is a low-pass filter, and the passband is set to [-fo / 3+Δ, fo / 3+Δ]KHz, and the Δ value is 1; the second detection channel is a band-pass filter, and the passband is set to [-fo*2 / 3-Δ, -fo / 3+Δ]KHz and [fo*1 / 3-Δ, fo*2 / 3+Δ]KHz; the third detection channel is a band-pass filter, and the passband is set to [-fo-Δ, -fo*2 / 3+Δ]KHz and [fo*2 / 3-Δ, fo+Δ]KHz; wherein fo is the maximum possible carrier center frequency offset value.

[0015] Furthermore, the carrier Doppler preliminary estimation result of the detection channel with the largest FFT peak is selected as the best carrier Doppler preliminary estimation result.

[0016] Furthermore, acquiring the best sampling point of the signal includes: acquiring the best sampling points of all symbols of the pilot, synchronization code and extended synchronization code to form a complete sequence to be estimated.

[0017] Furthermore, performing multi-symbol joint carrier phase measurement includes:

[0018] Calculate the correlation value in segments;

[0019] The phase value is calculated based on the correlation value.

[0020] Furthermore, the correlation value is

[0021]

[0022] Among them, r[n] is the sequence to be estimated, s[n] is the value corresponding to the midpoint n in the sequence to be estimated, is the number of signal segments, M is the total number of sampling points, m0 is the number of sampling points in each signal segment, R[m] is the relevant accumulated value, and * represents conjugation.

[0023] Furthermore, the phase value is

[0024]

[0025] in, represents the signal conjugate, φ[m]∈[0,2π], and j is a complex unit.

[0026] Further, performing Doppler estimation based on the obtained continuous carrier phase includes:

[0027]

[0028] in, f a , f0 and the estimated results of the initial phase, f0 is the Doppler frequency offset, f a is the Doppler change rate, and For f0 and f a , θ0 is the initial phase; H and Φ are the frequency matrix and code phase matrix in the Doppler estimation, and the Doppler estimation is performed using the least squares method.

[0029] Furthermore, the frequency matrix and code phase matrix in the Doppler estimation are respectively

[0030] Φ=[φ[1],…,φ[M1]] T

[0031]

[0032] Among them, T is the time corresponding to the sampling point, f s is the system sampling rate.

[0033] The advantages of the present invention compared with the prior art are:

[0034] (1) The present invention achieves a more accurate estimation result of the optimal symbol sampling time under weak signal conditions by separating the synchronization code part from the navigation message part and placing the synchronization code before the navigation message. At the same time, the extended synchronization code is combined with the previous pilot and synchronization code for Doppler estimation, which effectively improves the accuracy of Doppler estimation.

[0035] (2) The present invention improves the signal-to-noise ratio of the pilot part of the input signal by filtering the input signal separately and then detecting it during signal capture, thereby increasing the detection probability of signal arrival and achieving high-precision estimation of the carrier coarse frequency offset;

[0036] (3) The present invention improves the estimation accuracy of carrier phase by performing multi-symbol joint carrier phase measurement in carrier phase estimation, and achieves higher-precision Doppler estimation under weak signal conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0038] Figure 1 This is a schematic diagram of Doppler positioning based on low navigation signals;

[0039] Figure 2 is a low navigation signal format according to the present invention;

[0040] Figure 3 This is an example of an actual low-orbit navigation and positioning signal;

[0041] Figure 4 is a flow chart of a Doppler estimation method according to the present invention;

[0042] Figure 5 This is an example of an FFT peak detection result;

[0043] Figure 6 1 is a schematic diagram of the Doppler estimation process according to the present invention. DETAILED DESCRIPTION

[0044] In order to better understand the above technical solution, the technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0045] The following further describes in detail a high-precision Doppler estimation method based on multi-symbol joint processing provided by an embodiment of the present invention in conjunction with the accompanying drawings. Specific implementation methods may include:

[0046] S1) using the pilot of the low-orbit navigation signal to perform signal arrival detection and preliminary carrier Doppler estimation;

[0047] S2) removing the coarse carrier frequency offset and performing matched filtering;

[0048] S3) calculating the optimal symbol sampling time using the synchronization code of the low-orbit navigation signal;

[0049] S4) obtaining the optimal sampling points of the signal to form a sequence to be estimated;

[0050] S5) performing multi-symbol joint carrier phase measurement;

[0051] S6) performing carrier phase continuity detection and correction;

[0052] S7) Performing Doppler estimation based on the obtained continuous carrier phase to obtain a final estimation result.

[0053] Furthermore, the steps of using the pilot of the low-orbit navigation signal to perform signal arrival detection and carrier Doppler initial estimation are designed with multiple parallel detection channels, each of which includes a filter, a fast Fourier transform (hereinafter referred to as FFT), signal frequency domain arrival detection, and carrier Doppler initial estimation; the filter of each channel detects a possible frequency band of the input signal, and the total frequency band formed by the frequency bands of multiple filters can cover all possible frequency bands of the input signal.

[0054] In one possible implementation, the steps of using the pilot of the low-orbit navigation signal to perform signal arrival detection and carrier Doppler estimation include three parallel detection channels, and the filter design method for each channel is as follows:

[0055] Assume that the possible frequency range of the input signal is [-fo, fo] kHz, where fo is the maximum possible carrier center frequency offset, which is independent of the signal bandwidth. Assume there are three detection channels. Channel 1 uses a low-pass filter with a passband set to [-fo / 3+Δ, fo / 3+Δ] kHz, with a Δ value of 1. Channel 2 uses a band-pass filter with passbands set to [-fo*2 / 3-Δ, -fo / 3+Δ] kHz and [fo*1 / 3-Δ, fo*2 / 3+Δ] kHz. Channel 3 uses a band-pass filter with passbands set to [-fo-Δ, -fo*2 / 3+Δ] kHz and [fo*2 / 3-Δ, fo+Δ] kHz.

[0056] In one possible implementation, the steps of using the pilot of the low-orbit navigation signal to perform signal arrival detection and carrier Doppler estimation include three parallel detection channels, and the filter design method for each channel is as follows:

[0057] Furthermore, in the step of using the pilot of the low-orbit navigation signal to perform signal arrival detection and carrier Doppler preliminary estimation, the carrier Doppler preliminary estimation result selection module selects a specific method for selecting the best carrier Doppler preliminary estimation result from the carrier Doppler preliminary estimation results of all channels, and selects the carrier Doppler preliminary estimation result of the channel with the largest FFT peak as the best carrier Doppler preliminary estimation result.

[0058] In one possible implementation, the method of obtaining the best sampling points of the signal to form the sequence to be estimated is based on the specific method of the best sampling moment of the symbol, and the best sampling points of all symbols of the pilot, synchronization code and extended synchronization code are taken to form a complete sequence to be estimated.

[0059] Furthermore, in a possible implementation, the specific method for performing multi-symbol joint carrier phase measurement includes the following steps:

[0060] S51) Calculate the correlation value R[m] in sections:

[0061]

[0062] Among them, r[n] is the sequence to be estimated, s[n] is the value corresponding to the midpoint n in the sequence to be estimated, is the number of signal segments, m0 is the number of sampling points in each segment, and the time Tn corresponding to the sampling point closest to the middle of the segment is taken as Tm.

[0063] S52) Calculate the phase value φ[m]:

[0064]

[0065] in, represents the signal conjugate, φ[m]∈[0,2π].

[0066] A high-precision Doppler estimation method based on multi-symbol joint processing, wherein the specific method for performing Doppler estimation based on the obtained continuous carrier phase is:

[0067]

[0068] in, f a , f0 and the estimated results of the initial phase,

[0069] Φ=[φ d [1],…,φ d [M1]] T

[0070]

[0071] In the solution provided in the embodiment of the present invention, Figure 1A low-orbit satellite passing overhead flies regularly along its orbit. The ground navigation receiver continuously receives and tracks the low-orbit navigation signals sent by the low-orbit satellite, obtains the Doppler information in the signal, and completes its own navigation positioning.

[0072] like Figure 2 Typically, a low-orbit communication satellite divides a downlink channel into multiple superframes, each of which has at least one low-orbit navigation signal. The low-orbit navigation signal according to the present invention includes a pilot, a synchronization code, a navigation message, and an optional extended synchronization code.

[0073] like Figure 3 , this is an actual low-orbit navigation signal. Figure 3 The horizontal axis is the data point count, and the vertical axis is the signal strength. Figure 3 The upper part gives the amplitude envelope of the acquired signal in the digital domain, and the lower part gives the values ​​of the in-phase and quadrature components of the acquired signal.

[0074] exist Figure 3 The figure further shows that the relatively constant amplitude envelope of the low-orbit navigation signal in the example is the signal header, which is the pilot portion of the signal. The subsequent sections with significantly larger fluctuations are the synchronization code and navigation message. The envelope of the navigation message blank area in the figure is also constant. After the navigation message, there is an extended synchronization code.

[0075] like Figure 4 、 Figure 6 According to the present invention, the high-precision Doppler estimation method based on multi-symbol joint processing includes the following steps:

[0076] S1) Using the pilot of the low-orbit navigation signal to perform signal arrival detection and initial carrier Doppler estimation.

[0077] Multiple parallel detection channels are designed. Each channel includes a filter, a fast Fourier transform (FFT), signal frequency domain arrival detection, and initial carrier Doppler estimation. The filter of each channel detects a possible frequency band of the input signal. The total frequency band formed by the combined frequency bands of multiple filters can cover all possible frequency bands of the input signal.

[0078] Assume that the possible frequency range of the input signal is [-fo, fo] KHz, where fo is the maximum possible carrier center frequency offset value, which is independent of the signal bandwidth. Assume that there are three detection channels in total. The filter of channel 1 is a low-pass filter with a passband set to [-fo / 3+Δ, fo / 3+Δ] KHz, where Δ is a small offset, typically 1; channel 2 is a band-pass filter with a passband set to [-fo*2 / 3-Δ, -fo / 3+Δ] KHz and [fo*1 / 3-Δ, fo*2 / 3+Δ] KHz; channel 3 is a band-pass filter with a passband set to [-fo-Δ, -fo*2 / 3+Δ] KHz and [fo*2 / 3-Δ, fo+Δ] KHz. The result of this processing can improve the receiving sensitivity by 10*log10(3)=4.7dB compared to a single channel.

[0079] The carrier Doppler preliminary estimation result selection module selects the best carrier Doppler preliminary estimation result from the carrier Doppler preliminary estimation results of all channels. A typical selection criterion is to obtain the peak value in the FFT result in the FFT transformation step, and select the carrier Doppler preliminary estimation result of the channel with the largest FFT peak as the best carrier Doppler preliminary estimation result.

[0080] When the input signal has a carrier-to-noise ratio of 45dBHz and the signal length corresponding to FFT is 0.5ms, the effect of FFT detection is as follows: Figure 5 .

[0081] S2) Remove the coarse carrier frequency offset and perform matched filtering.

[0082] Carrier frequency offset removal and matched filtering are common techniques in this field and can be performed by ordinary technicians.

[0083] S3) calculating the optimal symbol sampling time using the synchronization code of the low-orbit navigation signal;

[0084] Assuming the signal sampling rate is N (N is no less than 8), a sliding calculation is performed on the cross-correlation between the input signal and the local synchronization code template signal. Assuming the sampling point with the maximum cross-correlation result is numbered x, then the optimal sampling time for all symbols of the navigation signal is the sampling point numbered x+iN, where i is an integer. In other words, the time corresponding to sampling point number x+iN is the optimal sampling time for all symbols.

[0085] S4) obtaining the optimal sampling points of the signal to form a sequence to be estimated;

[0086] Based on the symbol optimal sampling time, the optimal sampling points of all symbols from the pilot, synchronization code, and extended synchronization code are taken to form a complete sequence to be estimated. The estimated sequence here does not include the optimal sampling points of the symbols corresponding to the navigation message.

[0087] S5) performing multi-symbol joint carrier phase measurement;

[0088] For low-orbit navigation signals, the typical Doppler frequency deviation range is [-41kHz, 41kHz], and the Doppler change rate is less than 500Hz / s. According to the present invention, the mission Doppler approximately satisfies the linear relationship within the effective duration of the low-orbit navigation signal, that is,

[0089] f d [n] = f0 + f a n,n=0,1,…,M-1

[0090] Among them, M is the total number of sampling points, satisfying M=f s T, f0 is a fixed frequency deviation, f a is the Doppler change rate, f s is the system sampling rate. What we need to estimate is f0.

[0091] For the sequence r[n] to be estimated, ignoring the timing error, it satisfies

[0092]

[0093] Where A is the signal amplitude, w[n] is the noise, s[n] is the value of the original symbol, and Tn is the time corresponding to the sampling point. Due to the presence of navigation messages, Tn is not completely uniform. For the pilot, synchronization code, and extended synchronization code, s[n] is known. Our overall approach is to remove the modulated signal s[n] through correlation to obtain only the phase, and then perform least squares fitting to obtain the final Doppler frequency offset estimate.

[0094] The specific method for performing multi-symbol joint carrier phase measurement is:

[0095] S51) Calculate the correlation value R[m] in sections:

[0096]

[0097] in, is the number of signal segments, m0 is the number of sampling points in each segment, and the time Tn corresponding to the sampling point closest to the middle of the segment is taken as Tm.

[0098] S52) Calculate the phase value φ[m]:

[0099]

[0100] in, represents the signal conjugate, φ[m]∈[0,2π].

[0101] S6) performing carrier phase continuity detection and correction;

[0102] For the obtained φ[m], phase unwrapping is performed to maintain phase continuity. The specific steps are:

[0103] For any φ[m+1], if (φ[m+1]-φ[m])≥π / 2, then repeatedly execute φ[m+1]=φ[m+1]-π until (φ[m+1]-φ[m])<π / 2; otherwise, if (φ[m+1]-φ[m])≤-π / 2, then repeatedly execute φ[m+1]=φ[m+1]+π until (φ[m+1]-φ[m])<-π / 2

[0104] The final φ[m] should satisfy:

[0105]

[0106] Where u[m] is the phase noise.

[0107] S7) Performing Doppler estimation based on the obtained continuous carrier phase to obtain a final estimation result.

[0108] Usually, the least squares estimation is used to obtain:

[0109]

[0110] in, f a , f0 and the estimated results of the initial phase,

[0111] Φ=[φ d [1],…,φ d [M1]] T

[0112]

[0113] Assuming a low-orbit navigation signal with a double-sideband bandwidth of 32 kHz and a carrier-to-noise ratio of 45 dBHz, sampling at an eightfold rate, with a signal-to-noise ratio (SNR) of -9 dB before matched filtering and 0 dB after matched filtering, and using a signal with m0 = 10 Symbol ≈ 0.3 ms for correlation, a 13 dB SNR gain can be achieved. Assuming a 2 ms pilot, 2 ms ranging code, 8 ms navigation message, and 48 ms extended ranging code, the standard deviation of the Doppler estimate in Gaussian noise is better than 0.5 Hz at a carrier-to-noise ratio of 45 dBHz.

[0114] In this embodiment, we assume that the carrier-to-noise ratio is relatively low and the navigation message part may not be demodulated normally, so the navigation message part is not included in the Doppler estimation. In low-orbit navigation, each time a visible satellite passes overhead, it always goes from a low elevation angle to a high elevation angle and then to a low elevation angle. In the low-elevation angle stage, the carrier-to-noise ratio of the signal is low. When the carrier-to-noise ratio is lower than the demodulation threshold, the navigation message cannot be demodulated normally; at the high-elevation angle node, the carrier-to-noise ratio of the signal increases. Only when it is higher than the demodulation threshold can the navigation message be demodulated normally. During positioning solution (especially for static navigation receivers), the signal Doppler estimation results of the low-elevation angle node, the Doppler estimation results of the high-elevation angle stage and the navigation message can be combined to perform navigation positioning and improve positioning accuracy.

[0115] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0116] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

[0117] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A high-precision Doppler estimation method based on multi-symbol joint processing, characterized in that: include: The pilot signal of the low-orbit navigation signal is used to detect the signal arrival and estimate the carrier Doppler, and obtain the preliminary carrier Doppler estimation result; Remove the carrier coarse frequency offset of the initial carrier Doppler estimation result, perform matched filtering, and obtain the baseband signal after matched filtering; The optimal sampling time of the baseband signal after matched filtering is calculated using the synchronization code of the low-orbit navigation signal; Based on the optimal sampling moment of the symbol, the optimal sampling point of the baseband signal after matched filtering is obtained to form a sequence to be estimated; Performing multi-symbol joint carrier phase measurement on the sequence to be estimated to obtain a measurement result; Performing carrier phase continuity detection and correction on the measurement result to obtain a corrected continuous carrier phase; Doppler estimation is performed based on the corrected continuous carrier phase to obtain the final estimation result, so that even when the navigation message of the low-orbit navigation signal cannot be demodulated normally, the carrier Doppler estimation result that meets the preset accuracy requirements can still be obtained.

2. The high-precision Doppler estimation method based on multi-symbol joint processing according to claim 1, characterized in that: The signal arrival detection and carrier Doppler initial estimation include: designing multiple parallel detection channels, each channel including a filter module, an FFT module, a signal frequency domain arrival detection module and a carrier Doppler initial estimation module; the filter module obtains an input signal of a possible frequency band and transforms it through the FFT module, and then detects and estimates it through the signal frequency domain arrival detection module and the carrier Doppler initial estimation module respectively; and the frequency bands of multiple detection channels are combined to form a total frequency band that can cover all possible frequency bands of the input signal.

3. The high-precision Doppler estimation method based on multi-symbol joint processing according to claim 2, characterized in that: When the number of detection channels is three: The filter of the first detection channel is a low-pass filter with a passband set to [-fo / 3+Δ,fo / 3+Δ]KHz and a Δ value of 1; The second detection channel is a bandpass filter with the passband set to [-fo*2 / 3-Δ, -fo / 3+Δ]KHz and [fo*1 / 3-Δ, fo*2 / 3+Δ]KHz; The third detection channel is a bandpass filter with the passband set to [-fo-Δ, -fo*2 / 3+Δ]KHz and [fo*2 / 3-Δ, fo+Δ]KHz; Where fo is the maximum possible carrier center frequency offset value.

4. The high-precision Doppler estimation method based on multi-symbol joint processing according to claim 2, characterized in that: The carrier Doppler preliminary estimation result of the detection channel with the largest FFT peak is selected as the optimal carrier Doppler preliminary estimation result.

5. The high-precision Doppler estimation method based on multi-symbol joint processing according to claim 1, characterized in that: The obtaining of the best sampling point of the signal includes: obtaining the best sampling points of all symbols of the pilot, synchronization code and extended synchronization code to form a complete sequence to be estimated.

6. The high-precision Doppler estimation method based on multi-symbol joint processing according to claim 1, characterized in that: The performing multi-symbol joint carrier phase measurement includes: Calculate the correlation value in segments; The phase value is calculated based on the correlation value.

7. The high-precision Doppler estimation method based on multi-symbol joint processing according to claim 6, characterized in that: The relevant value is Among them, r[n] is the sequence to be estimated, s[n] is the value corresponding to the midpoint n in the sequence to be estimated, is the number of signal segments, M is the total number of sampling points, m0 is the number of sampling points in each signal segment, R[m] is the relevant accumulated value, and * represents conjugation.

8. The high-precision Doppler estimation method based on multi-symbol joint processing according to claim 7, characterized in that: The phase value is in, represents the signal conjugate, φ[m]∈[0,2π], and j is a complex unit.

9. The high-precision Doppler estimation method based on multi-symbol joint processing according to claim 7, characterized in that: The performing Doppler estimation based on the obtained continuous carrier phase comprises: in, f a , f0 and the estimated results of the initial phase, f0 is the Doppler frequency offset, f a is the Doppler change rate, and For f0 and f a , θ0 is the initial phase; H and Φ are the frequency matrix and code phase matrix in the Doppler estimation, and the Doppler estimation is performed using the least squares method.

10. The high-precision Doppler estimation method based on multi-symbol joint processing according to claim 9, characterized in that: The frequency matrix and code phase matrix in the Doppler estimation are respectively Φ=[φ[1],…,φ[M1]] T Among them, T is the time corresponding to the sampling point, f s is the system sampling rate.

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