High-dynamic Doppler blind measurement method for low-orbit satellite transmission system

Abstract

A high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system relates to the technical field of Doppler measurement, and comprises the following steps: processing a zero intermediate frequency received signal by using a CP timing estimation module to obtain a timing offset estimation value of an orthogonal frequency division multiplexing symbol; according to the timing offset estimation value, a fractional Doppler measurement module is adopted to measure a fractional Doppler value in the zero intermediate frequency receiving signal; calculating an integer Doppler value through an integer Doppler measurement module by using the fractional Doppler value; synthesizing the fractional Doppler value and the integer Doppler value into a Doppler measurement value; compensating the Doppler measurement value back to the zero intermediate frequency receiving signal, and measuring through a Doppler change rate measurement module to obtain a Doppler change rate; the method and the device are used for solving the problem of inaccurate uplink signal Doppler pre-compensation in a high-dynamic communication application scene.

Description

Technical Field

[0001] The present invention relates to the field of Doppler measurement technology, and in particular to a high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system. Background Art

[0002] Doppler measurement technology is a key technology in communication systems. The quality of its Doppler measurement performance has a direct and significant impact on subsequent signal demodulation, decoding, and rate modulation. For low-orbit satellite transmission systems, the highly dynamic channel characteristics bring serious inter-carrier interference (ICI) problems to the demodulation of its orthogonal frequency division multiplexing (OFDM) system. Therefore, Doppler measurement is an important and difficult issue in low-orbit satellite transmission systems.

[0003] Currently, Doppler measurement methods for OFDM systems are divided into data-assisted and non-data-assisted methods. Data-assisted methods are a common Doppler measurement method and are widely used in terrestrial mobile communications and satellite transmission systems. However, when the pilot / training sequence is unknown, data-assisted Doppler measurement methods are no longer applicable.

[0004] Non-data-assisted Doppler measurement methods, also known as Doppler-blind measurement methods, including maximum likelihood joint search based on cyclic prefix (CP), can effectively measure delay and Doppler. However, for high-dynamic low-orbit satellite application scenarios, the large integer frequency offsets caused by high dynamics cannot be effectively estimated by this algorithm. Therefore, an OFDM Doppler measurement method suitable for high dynamics is urgently needed.

[0005] In addition, for highly dynamic communication application scenarios, existing non-data-aided Doppler measurement methods cannot estimate the Doppler change rate, which also leads to inaccurate uplink signal Doppler pre-compensation.

[0006] In summary, satellite transmission OFDM systems with high dynamic application scenarios, whether data-assisted or non-data-assisted, have some insurmountable problems. Therefore, we propose a high-dynamic Doppler blind measurement method for low-orbit satellite transmission systems. Summary of the Invention

[0007] The object of the present invention is to provide a high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system, which is used to solve the problem of inaccurate Doppler pre-compensation of uplink signals in high-dynamic communication application scenarios.

[0008] The present invention is achieved through the following technical solutions:

[0009] A high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system, specifically comprising:

[0010] The CP timing estimation module processes the zero-IF received signal to obtain the estimated symbol timing offset (STO) of the orthogonal frequency division multiplexing symbol.

[0011] Based on the timing offset estimate, the fractional Doppler measurement module is used to measure the fractional Doppler value (FFO) of the zero-IF received signal.

[0012] Using the fractional Doppler value, the integer Doppler value (Integer carrier frequency offset, IFO) is calculated by the integer Doppler measurement module;

[0013] Combine the fractional Doppler value and the integer Doppler value into a Doppler measurement value (carrier frequency offset, CFO);

[0014] The Doppler measurement value is compensated back to the zero intermediate frequency receiving signal, and the Doppler change rate is measured by the Doppler change rate measurement module to obtain the Doppler change rate.

[0015] Furthermore, the CP timing estimation module is used to process the zero intermediate frequency received signal to obtain the timing offset estimation value of the orthogonal frequency division multiplexing symbol, specifically in the following steps:

[0016] Note k for a zero intermediate frequency receiving signal, performing time synchronization on the zero intermediate frequency receiving signal;

[0017] Performing coherent accumulation processing on the time-synchronized zero-IF received signal through the first coherent accumulation unit of the CP timing estimation module;

[0018] performing non-coherent accumulation processing on the coherent accumulation result by the first non-coherent accumulation unit of the CP timing estimation module;

[0019] The non-coherent accumulation result is estimated by the first linear classification unit of the CP timing estimation module to obtain a timing offset value.

[0020] Furthermore, the time synchronization of the zero intermediate frequency received signal is:

[0021]

[0022] Where k = 0, 1, ..., N-1 represents a shift to the kth sample point; N is the effective OFDM symbol length; and G is the cyclic prefix length, which is obtained from engineering experience and field equipment measurements.

[0023] Furthermore, the first coherent accumulation unit of the CP timing estimation module performs coherent accumulation processing on the time-synchronized zero-IF received signal, and the calculation formula is:

[0024]

[0025] Here, m represents the mth non-coherent accumulation. For each shift k, there are M groups of coherent accumulation results.

[0026] Furthermore, the first non-coherent accumulation unit of the CP timing estimation module performs non-coherent accumulation processing on the coherent accumulation result, and the calculation formula is:

[0027]

[0028] Furthermore, the first linear classification unit of the CP timing estimation module estimates the non-coherent accumulation result to obtain a timing offset value, and the specific calculation formula is:

[0029]

[0030] Furthermore, the fractional Doppler measurement module is used to measure the fractional Doppler value in the zero intermediate frequency received signal, and the specific steps are as follows:

[0031] Based on the timing offset value, extract M groups of zero-IF received signal samples after timing completion;

[0032] After calculating M groups of zero-IF received signal samples after timing completion using the second coherent accumulation unit of the fractional Doppler measurement module, the coherent accumulation result of the mth group of zero-IF received signal samples is output;

[0033] The phase detection processing unit of the fractional Doppler measurement module is used to perform phase detection processing on the coherent accumulation result;

[0034] According to the phase detection result, the proportional merging unit of the fractional Doppler measurement module outputs the fractional Doppler measurement value result.

[0035] Furthermore, the fractional Doppler value is used to calculate the integer Doppler value through the integer Doppler measurement module, and the specific steps are as follows:

[0036] Compensate the zero-IF signal samples after timing completion according to the fractional Doppler measurement result;

[0037] The CP removal unit of the integer Doppler measurement module removes the CP of the zero intermediate frequency signal after fractional Doppler compensation to obtain M groups of orthogonal frequency division multiplexing valid symbol sample data;

[0038] According to the M groups of OFDM valid symbol sample data, the OFDM demodulation unit of the integer Doppler measurement module calculates and outputs the mth group of valid OFDM mapping symbols;

[0039] Demodulating the mapped symbols through a digital modulation removal unit of an integer Doppler measurement module to obtain M groups of demodulated data;

[0040] Using the OFDM modulation unit of the integer Doppler measurement module, performing OFDM modulation on the M groups of demodulated data to obtain M groups of OFDM modulated signals;

[0041] Performing signal framing on M groups of OFDM modulated signals;

[0042] The first correlation spectrum estimation unit of the integer Doppler measurement module is used to calculate the framed signal to obtain a spectrum estimation output, and a binary number pair of the spectrum estimation output is constructed;

[0043] According to the binary number pairs output by the spectrum estimation, the integer Doppler measurement value is estimated by using the second linear classification unit of the integer Doppler measurement module.

[0044] Furthermore, the fractional Doppler value and the integer Doppler value are combined into a Doppler measurement value, and the calculation formula is:

[0045] CFO=IFO+FFO;

[0046] Where CFO is the Doppler measurement value, IFO is the integer Doppler value, and FFO is the fractional Doppler value.

[0047] Furthermore, the Doppler measurement value is compensated back to the zero intermediate frequency received signal, and the Doppler change rate is measured by the Doppler change rate measurement module, and the specific steps include:

[0048] The modulated signal is compensated using Doppler measurement value compensation;

[0049] The second correlation spectrum estimation unit of the Doppler change rate measurement module processes the compensated result to obtain a spectrum estimation output;

[0050] Performing incoherent accumulation on the spectrum estimation output by the second incoherent accumulation unit of the Doppler change rate measurement module, and forming 2G groups of binary number pairs according to the incoherent accumulation results;

[0051] Based on the binary number pairs of the non-coherent accumulation results, the Doppler change rate is estimated by the third linear classification unit of the Doppler change rate measurement module.

[0052] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0053] The present invention discloses a high-dynamic Doppler blind measurement method for low-orbit satellite transmission systems. The method utilizes the analytical characteristics of CP and digital modulation signals to achieve blind measurement without a pilot signal, thereby reducing system overhead and improving practicality. The method also increases the Doppler adaptability of the system, making Doppler measurement possible without pilot signal overhead.

[0054] In addition, this method is different from the traditional frequency offset estimation algorithm of high-order power cancellation, and does not introduce frequency doubling, thereby expanding the applicable range of Doppler measurement;

[0055] By separating fractional and integer frequency offsets and combining them with rate of change estimation, the frequency offset range in highly dynamic environments can be supported, adapting to the high-speed motion characteristics of low-orbit satellites. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A schematic flow chart of a method of the present invention is shown;

[0057] Figure 2 Schematic diagram of the CP timing estimation module of the present invention;

[0058] Figure 3 This is a schematic diagram of a fractional Doppler measurement module of the present invention;

[0059] Figure 4 This is a schematic diagram of an integer Doppler measurement module of the present invention;

[0060] Figure 5 Schematic diagram of the Doppler rate of change measurement module of the present invention;

[0061] Figure 6 Schematic diagram of the system flow of the present invention. DETAILED DESCRIPTION

[0062] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0063] Example 1

[0064] like Figure 1 A high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system is shown, specifically comprising:

[0065] The CP timing estimation module is used to process the zero-IF received signal to obtain the timing offset estimate of the orthogonal frequency division multiplexing symbol;

[0066] The CP timing estimation module estimates symbol timing offset through the time-domain correlation of the cyclic prefix, providing a precise time-domain synchronization basis for subsequent Doppler measurements. By leveraging the repetitive nature of the CP segment and valid symbol segment in the received signal, the maximum correlation peak is calculated through coherent and non-coherent accumulation to determine the symbol start position. This solves the inter-carrier interference (ICI) problem caused by timing offset in traditional methods under high dynamic conditions, improving synchronization accuracy.

[0067] Based on the estimated timing offset, the fractional Doppler measurement module measures the fractional Doppler value in the zero-IF received signal. Based on the CP timing estimation result, multiple groups of signal samples are extracted for phase detection and proportional merging to generate fractional Doppler values, thereby achieving precise compensation for small-scale frequency offsets and avoiding the phase ambiguity problem caused by excessive frequency offsets in traditional algorithms.

[0068] The integer Doppler measurement module calculates the integer Doppler value using fractional Doppler values. After fractional compensation, the integer frequency offset value is determined by removing the CP, performing OFDM demodulation, digital modulation cancellation, and correlation spectrum analysis, combined with linear classification. This solves the problem that traditional methods cannot handle large integer frequency offsets and expands the Doppler measurement range.

[0069] Combining the fractional Doppler value and the integer Doppler value into a Doppler measurement value;

[0070] The Doppler measurement value is compensated back to the zero intermediate frequency received signal, and the Doppler change rate is measured by the Doppler change rate measurement module. After compensating the Doppler measurement value, the Doppler change rate measurement module analyzes the dynamic change characteristics of the frequency deviation through periodic spectrum estimation and incoherent accumulation, making up for the defect of traditional blind measurement methods that cannot estimate the Doppler change rate, and improving the accuracy of uplink signal pre-compensation.

[0071] It should be noted that this method decomposes Doppler measurement into four stages: timing estimation, fractional compensation, integer compensation, and rate of change estimation. Through modular design and gradual optimization, the adaptability range is significantly improved. Moreover, through the separation of fractional and integer frequency offsets and combined with rate of change estimation, it supports a frequency offset range of more than ±50% in a high-dynamic environment and adapts to the high-speed motion characteristics of low-orbit satellites. It is completely based on signal structure characteristics (such as CP and modulation signal analysis) to achieve blind measurement without pilots, reduce system overhead and improve practicality. Through staged compensation and dynamic parameter optimization, the measurement range is extended to 2-3 times that of traditional methods, while supporting real-time tracking of the rate of change, which is suitable for complex channel environments.

[0072] Example 2

[0073] As an example, Figure 2The CP timing estimation module is used to process the zero intermediate frequency received signal to obtain the timing offset estimation value of the orthogonal frequency division multiplexing symbol. The specific steps are as follows:

[0074] Note r k for a zero intermediate frequency receiving signal, performing time synchronization on the zero intermediate frequency receiving signal;

[0075]

[0076] Where k = 0, 1, ..., N-1 represents shifting to the kth sample point; N is the effective OFDM symbol length; G is the cyclic prefix length, which is obtained from engineering experience and field equipment measurement; accurately capturing the symbol starting point provides the time domain synchronization basis for Doppler measurement;

[0077] The CP timing estimation module includes a first coherent accumulation unit, a first incoherent accumulation unit, and a first linear classification unit; in addition, a timing search control unit is used to time synchronize the zero intermediate frequency received signal and control the operation of the first coherent accumulation unit, the first incoherent accumulation unit, and the first linear classification unit;

[0078] The first coherent accumulation unit performs coherent accumulation processing on the time-synchronized zero-IF received signal. The calculation formula is:

[0079]

[0080] Among them, m represents the mth non-coherent accumulation. For each shift k, there are M groups of coherent accumulation results, r * It is a conjugate operation; it enhances signal correlation and improves anti-noise and anti-interference capabilities;

[0081] The coherent accumulation result is processed by the first non-coherent accumulation unit, and the calculation formula is:

[0082]

[0083] The first linear classification unit estimates the incoherent accumulation result to obtain the timing offset value. The specific calculation formula is:

[0084]

[0085] That is, the k value corresponding to the maximum value of R(k) is expressed as STO; it dynamically adapts to channel changes and supports stable communication in low-orbit satellite high-speed movement scenarios.

[0086] It should be noted that this step solves the problem of symbol timing synchronization in a high dynamic environment through the coordinated design of shift control and coherent accumulation.

[0087] Example 3

[0088] As an example, Figure 3 The fractional Doppler measurement module is used to measure the fractional Doppler value in the zero intermediate frequency received signal, and the specific steps are as follows:

[0089] Based on the timing offset value, M groups of zero-IF received signal samples are extracted after timing is completed to ensure that the signal segments to be processed subsequently are aligned with the symbol start, avoiding additional phase offsets introduced by timing errors.

[0090]

[0091] The fractional Doppler measurement module includes a second coherent accumulation unit, a phase detection processing unit, and an equal-proportional combining unit. The fractional Doppler measurement control unit is used to extract M groups of zero-IF received signal samples after timing is completed, and to control the operation of the second coherent accumulation unit, the phase detection processing unit, and the equal-proportional combining unit.

[0092] After the second coherent accumulation unit calculates M groups of zero intermediate frequency received signal samples after timing is completed, the coherent accumulation result of the mth group of zero intermediate frequency received signal samples is output to enhance the signal correlation and anti-noise capability, which is specifically expressed as follows;

[0093]

[0094] The phase detection processing unit is used to perform phase detection on the coherent accumulation result to indirectly estimate the fractional Doppler frequency deviation. The calculation formula is:

[0095]

[0096] According to the phase detection results The fractional Doppler measurement result is output by the proportional merging unit to improve the measurement accuracy and robustness. The calculation formula is:

[0097]

[0098] It should be noted that this step achieves high-precision, low-complexity fractional frequency offset estimation.

[0099] Example 4

[0100] As an example, Figure 4 The fractional Doppler value is used to calculate the integer Doppler value through the integer Doppler measurement module, and the specific steps are as follows:

[0101] Based on the fractional Doppler measurement results, the zero-IF signal samples after timing is completed are compensated to ensure that the residual frequency offset is only an integer multiple of the subcarrier interval;

[0102]

[0103] Where n represents the sampling point position starting from STO; o s It is expressed as oversampling, which is obtained from engineering experience and field equipment measurement, and is generally 4 to 8 times;

[0104] Used to eliminate the phase rotation and inter-subcarrier interference caused by fractional frequency offset in the received signal, providing a "clean" time-frequency synchronization signal for subsequent integer Doppler measurement;

[0105] The integer Doppler measurement module includes a CP removal unit, an OFDM demodulation unit, a digital modulation elimination unit, an OFDM modulation unit, a first correlation spectrum estimation unit, and a second linear classification unit; an integer Doppler measurement control unit is used to control the operation of the CP removal unit, the OFDM demodulation unit, the digital modulation elimination unit, the OFDM modulation unit, the first correlation spectrum estimation unit, and the second linear classification unit;

[0106] The CP removal unit removes the CP of the zero-IF signal after fractional Doppler compensation to obtain M groups of orthogonal frequency division multiplexing valid symbol sample data in order to extract valid OFDM symbol segments;

[0107]

[0108] According to the M groups of OFDM valid symbol sample data, the OFDM demodulation unit calculates and outputs the mth group of valid OFDM mapping symbols for converting the signal into the frequency domain;

[0109]

[0110] Where k = 0, 1, ..., K-1;

[0111] Demodulating the mapped symbols through a digital modulation removal unit to obtain M groups of demodulated data;

[0112] The demodulation calculation formula is:

[0113]

[0114] Where q represents the power, which is set by engineering experience and is generally 4 to 8;

[0115] M groups of demodulated data are expressed as:

[0116]

[0117] An OFDM modulation unit is used to perform OFDM modulation on M groups of demodulated data to obtain M groups of OFDM modulated signals, which can extract a pure spectrum structure;

[0118]

[0119] Performing signal framing on M groups of OFDM modulated signals;

[0120] x=[x0,x1,…,x M-1 ] T =[x0,x1,x2,…,x (M-1)N-1 ] T ;

[0121] A first correlation spectrum estimation unit is used to calculate the framed signal to obtain a spectrum estimation output, and a binary number pair of the spectrum estimation output is constructed to detect the spectrum shift amount caused by the integer frequency offset;

[0122] The spectral estimation output is expressed as:

[0123]

[0124] Among them, τ=-(M-1)N,-(M-1)N+1,…,(M-1)N-1; k=0,1,…,2(M-1)N;

[0125] According to Y(k), a binary number pair of length 2(M-1)N is constructed, which is expressed as:

[0126]

[0127] Based on the binary pairs output by the spectrum estimation, the integer Doppler measurement value is estimated using the second linear classification unit, which is expressed as;

[0128]

[0129] Example 5

[0130] As an example, Figure 5 The fractional Doppler value and the integer Doppler value are combined into a Doppler measurement value, and the calculation formula is:

[0131] CFO=IFO+FFO;

[0132] Where CFO is the Doppler measurement value, IFO is the integer Doppler value, and FFO is the fractional Doppler value.

[0133] In addition, the Doppler measurement value is compensated back to the zero intermediate frequency received signal, and the Doppler change rate is measured by the Doppler change rate measurement module. The specific steps include:

[0134] Doppler measurement compensation is used to compensate the modulated signal and eliminate residual integer frequency offset;

[0135]

[0136] The Doppler change rate measurement module includes a second correlation spectrum estimation unit, a second incoherent accumulation unit and a third linear classification unit; a Doppler change rate measurement control unit is used to control the operation of the second correlation spectrum estimation unit, the second incoherent accumulation unit and the third linear classification unit;

[0137] The second correlation spectrum estimation unit is used to process the compensated results to obtain a spectrum estimation output, capturing the changing trend of the frequency deviation over time;

[0138]

[0139] Where m = 0, 1, ..., M-1;

[0140] The spectrum estimation output is incoherently accumulated by the second incoherent accumulation unit, and 2G groups of binary number pairs are formed based on the incoherent accumulation results to improve the signal-to-noise ratio and measurement stability. The incoherent accumulation result is expressed as:

[0141]

[0142] The 2G binary number pairs are represented as:

[0143]

[0144] Based on the binary number pairs of the incoherent accumulation results, the Doppler change rate is estimated by the third linear classification unit, which is expressed as:

[0145]

[0146] It should be noted that the timing search control unit, fractional Doppler measurement control unit, integer Doppler measurement control unit and Doppler change rate measurement control unit in the above embodiment are used to control the timing or interruption of signal processing in the corresponding modules, thereby ensuring the orderly processing of each module and ultimately realizing blind measurement of high dynamic Doppler.

[0147] Example 6

[0148] like Figure 6 A high-dynamic Doppler blind measurement system for a low-orbit satellite transmission system is shown, comprising a zero-IF receiving signal acquisition module, a CP timing estimation module, a fractional Doppler measurement module, a fractional Doppler compensation module, an integer Doppler measurement module, and a Doppler change rate measurement module;

[0149] The output of the zero intermediate frequency receiving signal acquisition module is connected to the CP timing estimation module, and the output of the CP timing estimation module is respectively connected to the fractional Doppler measurement module and the fractional Doppler compensation module; the output of the fractional Doppler compensation module is connected to the integer Doppler measurement module, and the output of the fractional Doppler measurement module and the output of the integer Doppler measurement module are added through an adder and then connected to the Doppler change rate measurement module.

[0150] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system, characterized in that: Specifically include: The CP timing estimation module is used to process the zero-IF received signal to obtain the timing offset estimate of the orthogonal frequency division multiplexing symbol; According to the timing offset estimation value, a fractional Doppler measurement module is used to measure the fractional Doppler value in the zero intermediate frequency received signal; Using the fractional Doppler value, the integer Doppler value is calculated by the integer Doppler measurement module; Combining the fractional Doppler value and the integer Doppler value into a Doppler measurement value; The Doppler measurement value is compensated back to the zero intermediate frequency receiving signal, and the Doppler change rate is measured by the Doppler change rate measurement module to obtain the Doppler change rate.

2. The high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system according to claim 1, characterized in that: The CP timing estimation module is used to process the zero intermediate frequency received signal to obtain the timing offset estimation value of the orthogonal frequency division multiplexing symbol. The specific steps are: Note r k for a zero intermediate frequency receiving signal, performing time synchronization on the zero intermediate frequency receiving signal; Performing coherent accumulation processing on the time-synchronized zero-IF received signal through the first coherent accumulation unit of the CP timing estimation module; performing non-coherent accumulation processing on the coherent accumulation result by the first non-coherent accumulation unit of the CP timing estimation module; The non-coherent accumulation result is estimated by the first linear classification unit of the CP timing estimation module to obtain a timing offset value.

3. The high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system according to claim 2, characterized in that: The time synchronization of the zero intermediate frequency received signal is as follows: Wherein, k=0, 1, ..., N-1 indicates shifting to the kth sample point; N is the effective OFDM symbol length; and G is the cyclic prefix length.

4. The high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system according to claim 3, characterized in that: The first coherent accumulation unit of the CP timing estimation module performs coherent accumulation processing on the time-synchronized zero-IF received signal, and the calculation formula is: Here, m represents the mth non-coherent accumulation. For each shift k, there are M groups of coherent accumulation results.

5. The high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system according to claim 4, characterized in that: The first non-coherent accumulation unit of the CP timing estimation module performs non-coherent accumulation processing on the coherent accumulation result, and the calculation formula is:

6. The high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system according to claim 5, characterized in that: The first linear classification unit of the CP timing estimation module estimates the non-coherent accumulation result to obtain a timing offset value. The specific calculation formula is:

7. The high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system according to claim 1, characterized in that: The fractional Doppler measurement module is used to measure the fractional Doppler value in the zero intermediate frequency received signal, and the specific steps are as follows: Based on the timing offset value, extract M groups of zero-IF received signal samples after timing completion; After calculating M groups of zero-IF received signal samples after timing completion using the second coherent accumulation unit of the fractional Doppler measurement module, the coherent accumulation result of the mth group of zero-IF received signal samples is output; The phase detection processing unit of the fractional Doppler measurement module is used to perform phase detection processing on the coherent accumulation result; According to the phase detection result, the proportional merging unit of the fractional Doppler measurement module outputs the fractional Doppler measurement value result.

8. The high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system according to claim 1, characterized in that: The fractional Doppler value is used to calculate the integer Doppler value through the integer Doppler measurement module, and the specific steps are as follows: Compensate the zero-IF signal samples after timing completion according to the fractional Doppler measurement result; The CP removal unit of the integer Doppler measurement module removes the CP of the zero intermediate frequency signal after fractional Doppler compensation to obtain M groups of orthogonal frequency division multiplexing valid symbol sample data; According to the M groups of OFDM valid symbol sample data, the OFDM demodulation unit of the integer Doppler measurement module calculates and outputs the mth group of valid OFDM mapping symbols; Demodulating the mapped symbols through a digital modulation removal unit of an integer Doppler measurement module to obtain M groups of demodulated data; Using the OFDM modulation unit of the integer Doppler measurement module, performing OFDM modulation on the M groups of demodulated data to obtain M groups of OFDM modulated signals; Performing signal framing on M groups of OFDM modulated signals; The first correlation spectrum estimation unit of the integer Doppler measurement module is used to calculate the framed signal to obtain a spectrum estimation output, and a binary number pair of the spectrum estimation output is constructed; According to the binary number pairs output by the spectrum estimation, the integer Doppler measurement value is estimated by using the second linear classification unit of the integer Doppler measurement module.

9. The high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system according to claim 1, characterized in that: The fractional Doppler value and the integer Doppler value are combined into a Doppler measurement value, and the calculation formula is: CFO=IFO+FFO; Where CFO is the Doppler measurement value, IFO is the integer Doppler value, and FFO is the fractional Doppler value.

10. The high-dynamic Doppler blind measurement method for a low-orbit satellite transmission system according to claim 1, characterized in that: The Doppler measurement value is compensated back to the zero intermediate frequency received signal, and the Doppler change rate is measured by the Doppler change rate measurement module, specifically comprising the following steps: The modulated signal is compensated using Doppler measurement value compensation; The second correlation spectrum estimation unit of the Doppler change rate measurement module processes the compensated result to obtain a spectrum estimation output; Performing incoherent accumulation on the spectrum estimation output by the second incoherent accumulation unit of the Doppler change rate measurement module, and forming 2G groups of binary number pairs according to the incoherent accumulation results; Based on the binary number pair of the non-coherent accumulation result, the Doppler change rate is estimated by the third linear classification unit of the Doppler change rate measurement module.

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