A nonlinear satellite channel equalization method and system

Abstract

The present invention relates to the field of satellite-terrestrial broadband communication technology, and discloses a nonlinear satellite channel equalization method and system, which includes the following steps: S1, AD sampling: using an analog-to-digital conversion circuit to sample a transmitted signal and restore the analog signal to a digital signal; S2, pre-equalization: offsetting the nonlinear distortion of the sampled digital signal; S3, demodulation: demodulating the pre-equalized digital signal. The present invention solves the problems of poor performance, large amount of calculation, poor working stability, etc. in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite-terrestrial broadband communication, and in particular to a nonlinear satellite channel equalization method and system. Background Art

[0002] Satellite-to-terrestrial broadband (bandwidth greater than 100MHz) communications are a core technology in satellite applications. Due to the long distances between satellites and the ground, the system uses high-power amplifiers, which can cause signal distortion, primarily in the form of amplitude modulation / amplitude modulation (AM / AM) and amplitude modulation / phase modulation (AM / PM). Furthermore, to improve transmission efficiency, the system often employs high-order signal modulation schemes. However, these high-order modulation signals are more susceptible to channel distortion, which can reduce reception performance.

[0003] Figure 7 This paper describes a typical satellite-to-ground communication system. The satellite modulates the transmitted data sequence, generating an analog signal. After passing through the channel, the signal is distorted by nonlinear characteristics such as group delay and amplification. This distortion has little impact on conventional modulations (such as BPSK (binary phase-shift keying) and QPSK (quaternary phase-shift keying), allowing the receiver demodulator to achieve good signal reception. However, for higher-order modulation signals (8PSK (octal phase-shift keying), 16QAM (hexadecimal quadrature amplitude modulation), 16APSK (hexadecimal amplitude-phase modulation), and 32APSK (thirty-two binary amplitude-phase modulation)), channel nonlinearity significantly impacts demodulation sensitivity, with the impact becoming more pronounced with higher modulation orders. In this case, nonlinear equalization is required in the receiver demodulator to determine the channel's characteristic function and use its inverse function to offset the signal distortion caused by the channel characteristics.

[0004] From a practical perspective, nonlinear equalization of satellite channels has the following difficulties: 1. Poor performance; 2. Large amount of computation, which cannot be implemented using conventional electronic devices; 3. Poor working stability.

[0005] The equalization methods currently available in the literature are: 1. They primarily target linear channels; 2. They employ nonlinear algorithms, which impose high constraints on their use cases and are not universally applicable; and 3. They cannot guarantee operational stability. Currently, there are no reports on practical technologies related to nonlinearity in satellite-to-terrestrial broadband communications. Most research is still at the theoretical simulation stage or focused on computer-based back-end processing. Summary of the Invention

[0006] To overcome the deficiencies of the prior art, the present invention provides a nonlinear satellite channel equalization method and system to solve the problems of poor performance, large computational complexity, and poor working stability in the prior art.

[0007] The technical solution adopted by the present invention to solve the above problems is:

[0008] A nonlinear satellite channel equalization method comprises the following steps:

[0009] S1, AD sampling: use analog-to-digital conversion circuit to sample the transmitted signal and restore the analog signal to a digital signal;

[0010] S2, pre-equalization: offsets the nonlinear distortion of the sampled digital signal;

[0011] S3, demodulation: demodulate the digital signal after pre-equalization.

[0012] As a preferred technical solution, in step S2, the pre-equalization uses a polyphase transversal filtering structure to offset the nonlinear distortion of the received digital signal.

[0013] As a preferred technical solution, the pre-equalization includes two working modes, namely a self-calibration mode with human participation and an unmanned working mode: in the self-calibration mode, the transmitter sends a known signal to make all the coefficients of the pre-equalization and post-equalization converge according to the channel characteristics. The goal is to minimize the mean square error between the received signal and the transmitter signal. When the mean square error of the demodulated signal fluctuates within the set range, the self-calibration mode is completed; in the working mode, the pre-equalization coefficient is fixed, and the input signal is adaptively equalized by adjusting the post-equalization. The result after equalization is the demodulated output.

[0014] As a preferred technical solution, in step S2, in the self-calibration mode, the carrier frequency of the known signal at the transmitting end is an integer multiple of the sampling rate of the analog-to-digital conversion circuit, the symbol rate of the known signal at the transmitting end is an integer multiple of the sampling rate of the analog-to-digital conversion circuit, and the modulation system of the known signal at the transmitting end is high-order modulation.

[0015] As a preferred technical solution, in step S2, the pre-equalizer compares the distance between the received signal and the known signal at the transmitting end to obtain a nonlinear equalization error, and uses the error to adjust the coefficient of the equalization filter.

[0016] As a preferred technical solution, the following steps are also included:

[0017] S4, post-equalization: uses a polyphase transverse filtering structure to perform linear equalization on the linear part of the demodulated data.

[0018] As a preferred technical solution, the self-calibration mode includes the following steps:

[0019] Z1, perform the following nonlinear combination on M consecutive sampling points:

[0020]

[0021] in, is the third-order nonlinear combination vector of M input signals, The length is L, i, j, t are multiple input signal values ​​involved in the nonlinear operation, k is the index of the nonlinear combination vector, idx is the operation time in time sequence, M is the length of the nonlinear equalizer, M is an odd number,

[0022]

[0023] Z2, Multiply by the L-length transverse filter coefficients to obtain the nonlinear combination result:

[0024]

[0025] Among them, z idx is the third-order nonlinear combination output, c uline，k is the transverse filter coefficient sequence, and the initial value of the transverse filter coefficient sequence is as follows:

[0026]

[0027] Z3, take 2N consecutive nonlinear combination result data z idx , divided into two groups according to odd and even numbers:

[0028]

[0029] in, is the even sequence output by the nonlinear combination, is the even-numbered value output by the nonlinear combination, is the odd sequence output by the nonlinear combination, is the odd value output by the nonlinear combination;

[0030] Z4, respectively, with the initialization coefficients

[0031]

[0032] z idx Perform linear filtering and get:

[0033]

[0034] is the received modulated signal;

[0035] Among them, c rvrline，k The equalization coefficient is obtained by calculating the influence of the real part of the nonlinear equalization signal on the real part of the input signal, c iviline，kThe equalization coefficient is obtained by calculating the influence of the imaginary part of the nonlinear equalization signal on the imaginary part of the input signal. is the real part of the received modulated signal, is the imaginary part of the received modulated signal;

[0036] Z5, compare the error between the received modulated signal and the original signal:

[0037]

[0038] Among them, err real To equalize the error between the real part of the output signal and the real part of the transmitted signal, txSym real is the real part of the transmitted signal, err imag To equalize the error between the imaginary part of the output signal and the imaginary part of the transmitted signal, txSym imag is the imaginary part of the transmitted signal;

[0039] Z6, update the filter coefficients of the transverse filter structure of the pre-equalization and post-equalization, and the nonlinear transverse filter coefficient update method is:

[0040]

[0041]

[0042] Where n is the number of updates, is the equalizer coefficient updated for the nth time, is the equalizer coefficient updated for the n-1th time, μ uline is the pre-equalization update step, y idx1+j is the data of L consecutive nonlinear combinations starting from idx1+j, y idx2+j is the data of L consecutive nonlinear combinations starting from idx2+j;

[0043] The linear transversal filter coefficient update method is:

[0044]

[0045] in, represents the equalizer coefficient updated for the nth time, Represents the equalizer coefficient updated for the n-1th time, μ line Indicates the post-equalization update step;

[0046] Z7, judge whether the pre-nonlinear equalization coefficient has stabilized. The judgment basis is: if the residual error fluctuation is small and the distance between the points of the QAM constellation is constant, then the self-calibration mode is completed and the nonlinear transverse filter coefficient is recorded. Switch to working mode and access the actual signal.

[0047] As a preferred technical solution, the working mode includes the following steps:

[0048] G1, combines the input sampling signals for M consecutive sampling points according to the combination method and order during self-calibration:

[0049]

[0050] in, Represents M actual input signals Rx idx The third-order nonlinear combination vector, Rx idx-i 、Rx idx-j 、Rx idx-t Represents multiple actual input signals involved in nonlinear operations;

[0051] G2, The nonlinear equalization coefficient sequence obtained in the self-calibration stage Dot product to obtain the nonlinear equalization result:

[0052]

[0053] Among them, Rz idx is the result after nonlinear equalization.

[0054] As a preferred technical solution, post-equalization includes the following steps:

[0055] S41, perform timing synchronization and carrier synchronization on the signal after nonlinear processing to restore the complex baseband signal rxSig idx ;

[0056] S42, take N consecutive complex baseband signals and the transversal filter coefficients Point multiplication to get the filtering result rxSym idx :

[0057]

[0058] S43, perform maximum likelihood estimation on the filtering result and obtain Extract the difference between the likelihood estimate and the filtered result:

[0059]

[0060] Among them, err idx is the error between the maximum likelihood estimate and the actual filtering result, is the maximum likelihood estimate of the filtering result;

[0061] S44, use err idx For transversal filter coefficients to update.

[0062] A nonlinear satellite channel equalization system, used to implement the nonlinear satellite channel equalization method, includes the following modules connected in sequence:

[0063] AD sampling module: used to sample the transmitted signal using an analog-to-digital conversion circuit and restore the analog signal to a digital signal;

[0064] Pre-equalization module: used to offset the nonlinear distortion of the sampled digital signal;

[0065] Demodulation module: used to demodulate the digital signal after pre-equalization;

[0066] Post-equalization module: used to perform linear equalization processing on the linear part of the demodulated data using a multi-phase transverse filtering structure.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] The present invention distributes the solution to the channel problem between the transmitter and the receiving demodulator, and specifically designs the transmitter signal, thereby reducing the difficulty of achieving equalization alone at the receiving demodulator. The demodulator equalization method is divided into two parts, reducing implementation complexity and improving stability. The pre-equalization adopts two working modes. The self-calibration mode allows for human supervision and intervention, with good performance. In this working mode, the channel parameters are no longer affected by noise and have high stability. The pre-equalization uses the Volterra nonlinear adaptive equalization algorithm to achieve a compromise between performance and complexity. The post-equalization is an equalization method for conventional 100-megabit broadband receiving signals, taking into account stability, implementation difficulty, and performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a circuit diagram of the present invention;

[0070] Figure 2 This is a schematic diagram of a traditional demodulation circuit;

[0071] Figure 3 It is a schematic diagram of the workflow of the receiver self-calibration stage of the present invention;

[0072] Figure 4 It is a schematic diagram of the working process of the receiver of the present invention;

[0073] Figure 5 is a comparison chart of received signal quality without and with the present invention;

[0074] Figure 6 This is a comparison chart of demodulation quality of receivers without and with the present invention;

[0075] Figure 7 It is a working principle diagram of the high-speed wireless data transmission system of the present invention. DETAILED DESCRIPTION

[0076] The present invention will be further described in detail below with reference to the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0077] Example 1

[0078] like Figures 1 to 7 As shown, the present invention provides a nonlinear method for high-order modulation signals in satellite-to-ground broadband communications, which has a certain universality, greatly improves the demodulation performance, and solves the contradiction between performance and computing resource overhead.

[0079] The present invention addresses the shortcomings of the prior art by providing a nonlinear equalization method for high-order modulated signals in satellite-to-terrestrial broadband communications. This method has broad applicability, significantly improves demodulation performance, and resolves the conflict between equalization performance and computational resource overhead. This method, applied to the receiver demodulator of a satellite-to-terrestrial broadband communication system, is a baseband equalization method based on digital signal processing and combines neural network computing technology with parallel adaptive blind equalization.

[0080] The above-mentioned purpose of the present invention is achieved by the following measures, and has the following technical features: (1) The solution of the problem is distributed in the transmitter and the receiving demodulator. (2) The satellite channel is estimated by sending a specific signal (specific signal center frequency, symbol rate, modulation mode, modulation sequence). (3) The receiving demodulator equalization is divided into two parts, the first part processes the nonlinear part (hereinafter referred to as pre-equalization), and the second part processes the linear part (hereinafter referred to as post-equalization). (4) The pre-equalization is as close to the signal arrival position as possible, and has two working modes, one is a self-calibration mode and the other is a working mode. (5) In the self-calibration mode, the pre-equalization uses the Volterra nonlinear adaptive equalization algorithm to adjust the parameters according to the known signal at the transmitter. (6) In the working mode, the pre-equalization performs fixed compensation on the input signal according to the adjusted parameters. (7) The post-equalization is an equalization method for conventional 100-megabit broadband receiving signals.

[0081] It is worth mentioning that: Figure 1 Two parts are added (two dotted elliptical boxes: pre-equalization and post-equalization). These two parts are the core of the present invention; the pre-equalization dotted elliptical box contains a solid box and a dotted box. The solid box is run during the operation of the device, and the dotted box is run before the device works and calculates the working parameters in the solid box. The stage in which the dotted box runs is called the "self-calibration stage", which requires the "transmitting signal" to send specific data. Figure 2This is a block diagram of a receiver. Figure 1 compared to, Figure 2 The timing synchronization and carrier synchronization on the board are combined into a "demodulation module".

[0082] The present invention implements two digital logic circuits in a demodulator receiver, respectively implementing nonlinear equalization (the corresponding digital logic circuit is hereinafter referred to as nonlinear equalization) and linear equalization (the corresponding digital logic circuit is hereinafter referred to as linear equalization) of the received signal. By employing specific operating steps to coordinate the two equalization components, higher receiving sensitivity is achieved.

[0083] The nonlinear equalizer of the present invention is located after the analog-to-digital conversion circuit and has a polyphase transversal filter structure. It uses a third-order Volterra structure to offset the nonlinear distortion of the received signal.

[0084] The linear equalization of the present invention is located after demodulation, has a multi-phase transverse filtering structure, and adopts a decision feedback linear equalization algorithm to correct the linear interference suffered by the received signal.

[0085] The present invention describes certain operating steps. Before operation, the demodulation receiver of the present invention first receives a specific signal, calculates a set of nonlinear equalization coefficients based on the reception result of the specific signal, and then places these nonlinear equalization coefficients into nonlinear equalization (referred to as self-calibration mode). During operation, the above coefficients are used to perform nonlinear equalization on the actual signal, and subsequent linear equalization performs adaptive equalization based on the input working signal (referred to as working mode).

[0086] For the specific signal described in the present invention, the carrier frequency is an integer multiple of the sampling rate of the analog-to-digital conversion circuit of the demodulation receiver, the symbol rate is an integer multiple of the sampling rate of the analog-to-digital conversion circuit of the demodulation receiver, and the modulation system is high-order modulation (the digital information carried by each symbol is greater than two bits).

[0087] The present invention calculates a set of nonlinear equalization coefficients, compares the distance between the received signal and the expected value result by nonlinear equalization, obtains the nonlinear equalization error, and uses the error to adjust the directional filter coefficient.

[0088] The subsequent linear equalization described in the present invention adopts a minimum mean square error adaptive blind equalization structure.

[0089] This invention proposes a method for equalizing broadband (bandwidth greater than 100 MHz) satellite channels. By incorporating a specific digital logic circuit and implementing a specific operating procedure into a demodulation receiver, this method achieves equalization of the communication channel and improves receiver sensitivity. Before the receiver operates, it calculates the nonlinear distortion generated by a specific signal passing through the channel and the optimal solution for eliminating this distortion. During operation, the receiver first places the pre-calculated solution into a dedicated digital logic circuit to achieve nonlinear distortion equalization of the input signal. A specific digital logic circuit then performs real-time linear equalization. This cascade of the two improves the sensitivity of the demodulation receiver. The invention designs a specific digital modulation signal waveform that allows the receiving end to recover the originating sequence without demodulation. The difference between the originating sequence and the originating sequence passing through the channel is compared to calculate the optimal solution for eliminating distortion. The demodulation receiver utilizes a Volterra series digital logic circuit to achieve nonlinear equalization of the received signal before demodulation. The signal is then conventionally demodulated. After demodulation, the signal is linearly equalized using a linear equalization digital logic circuit employing a minimum mean square error algorithm. This invention combines specific functional methods with workflows, enabling collaborative operation across two dimensions. This method proposes a nonlinear equalization method for broadband channels. This method, employing a time-domain parallel architecture, addresses the complexities, poor stability, and ineffectiveness of nonlinear equalization methods. The invention is applicable to broadband signal transmission, remote sensing, and high-speed wireless signal processing.

[0090] The present invention relates to the field of satellite-to-ground broadband (bandwidth greater than 100 MHz) communications. A broadband signal receiving and demodulating device uses the method to eliminate the influence of a channel on a high-order modulated signal and improve receiving sensitivity.

[0091] Compared with the prior art, the present invention has the following beneficial effects.

[0092] The solutions to channel problems are distributed across the transmitter and receiver demodulator, and the transmitter signal is specifically designed to reduce the difficulty of achieving equalization at the receiver demodulator alone. The demodulator equalization method is divided into two parts, reducing implementation complexity and improving stability. The pre-equalization adopts two working modes. The self-calibration mode allows for human supervision and intervention, with good performance. In this working mode, the channel parameters are no longer affected by noise and have high stability. The pre-equalization uses the Volterra nonlinear adaptive equalization algorithm to achieve a compromise between performance and complexity. The post-equalization is an equalization method for conventional 100-megabit broadband receiving signals, taking into account stability, implementation difficulty, and performance.

[0093] The method of the invention is applicable to a large-scale logic gate array and is used for a receiving demodulator of a satellite-ground broadband communication system.

[0094] It is particularly suitable for satellite-to-ground broadband communication systems using high-order modulation, and is used in receiving demodulators with symbol rates exceeding 100 Mbps.

[0095] Example 2

[0096] like Figures 1 to 7 As shown, as a further optimization of Example 1, based on Example 1, this embodiment also includes the following technical features:

[0097] See Figure 1 . Compared with conventional receiving demodulator ( Figure 2 Compared to conventional receiver demodulators, the receiver demodulator incorporating this nonlinear satellite channel equalization method adds two additional components: a pre-equalization circuit and a post-equalization circuit. The pre-equalization circuit, located after the analog-to-digital conversion circuit, performs nonlinear equalization on the sampled digital signal to improve signal quality. The post-equalization circuit, located after the demodulation circuit, offsets any remaining channel interference and ultimately outputs an equalized demodulated signal.

[0098] The receiver demodulator incorporating this nonlinear satellite channel equalization method has two operating modes: a self-calibration mode with human intervention and an unattended mode. In the self-calibration mode, the transmitter sends a known signal, causing all coefficients of the pre-equalizer and post-equalizer to converge based on the channel characteristics. The goal is to minimize the mean square error (MSE) between the received and transmitted signals. The self-calibration mode is complete when the MSE of the demodulated signal fluctuates within a small range. In this operating mode, the pre-equalization coefficients are fixed, and the input signal is adaptively equalized by adjusting the post-equalization circuit. The equalized result is the demodulator output.

[0099] 1. Self-calibration mode:

[0100] The transmitter has a known sequence: the signal carrier frequency is one-fourth of the AD sampling rate of the receiver demodulator, the symbol rate is one-eighth of the AD sampling rate, and the modulation method is fixed to 16QAM. For example, if the AD sampling rate is 4.8GHz, the center frequency of the transmitted signal is 1.2GHz and the symbol rate is 600MHz. The transmitter and demodulator receiver can use different reference sources, but the relative frequency deviation between the two should be guaranteed to be |f T -f R | / f R Should not exceed 5.208e -7 This condition can be relaxed to within about 80,000 sampling points, and the frequency difference between the two does not exceed 5.208e -7 .

[0101] See Figure 3 , perform the following nonlinear combination on M consecutive sampling points (M is an odd number, which is the length of the nonlinear equalizer):

[0102]

[0103]

[0104] There are M input signals x idx+i There are L third-order nonlinear combinations of .

[0105]

[0106] Multiply by the L-length transverse filter coefficients to obtain the nonlinear combination result:

[0107]

[0108] The initial value of the transverse filter coefficient sequence is as follows:

[0109]

[0110] Take 2N consecutive (N is the length of the post-linear equalizer, 2N means equalizing the real part and the imaginary part respectively) nonlinear combination result data z idx , divided into two groups according to odd and even

[0111]

[0112] Initialize the coefficients with

[0113]

[0114] z idx Perform linear filtering.

[0115]

[0116] That is the received 16QAM modulated signal.

[0117] Compare the error between the received signal and the original signal

[0118]

[0119] The two-stage (nonlinear transversal filter and linear transversal filter) filter coefficients are updated. The nonlinear transversal filter coefficient update method is as follows:

[0120]

[0121] Indicates the nth updated equalizer coefficient, μ uline Indicates the update step of the nonlinear equalizer. Too large a step will cause the equalizer to have poor convergence or even fail to converge. idx1+j ,y idx2+j Represents data of L consecutive nonlinear combinations starting from idx1+j(idx2+j).

[0122] Linear transversal filter coefficient update method:

[0123]

[0124] Same as above, c n Indicates the nth updated equalizer coefficient, μ line Indicates the linear equalizer update step. Too large a step will cause the equalizer to converge poorly or even fail to converge.

[0125] After approximately 8,000 symbols of iterative operation, the two sets of transversal filter coefficients will fluctuate around a specific value. At this point, it is possible to manually determine whether the pre-nonlinear equalization coefficients have stabilized. The judgment is based on two criteria: if the residual error fluctuation is small and the distance between the points in the QAM constellation is constant, then the self-calibration mode is considered complete and the nonlinear transversal filter coefficients c are recorded. uline The receiver switches to working mode and receives the actual signal.

[0126] 2. The working mode is implemented as follows:

[0127] See Figure 4 , combine the input sampling signals for M consecutive sampling points according to the combination method and order during self-calibration:

[0128] G1, combines the input sampling signals for M consecutive sampling points according to the combination method and order during self-calibration:

[0129]

[0130] in, Represents M actual input signals Rx idx The third-order nonlinear combination vector, Rx idx-i 、Rx idx-j 、Rx idx-t Represents multiple actual input signals involved in nonlinear operations;

[0131] G2, The nonlinear equalization coefficient sequence obtained in the self-calibration stage Dot product to obtain the nonlinear equalization result:

[0132]

[0133] Among them, Rz idx is the result after nonlinear equalization.

[0134] The linear equalizer, its working process is briefly described as follows:

[0135] 1) Perform timing synchronization and carrier synchronization on the signal after nonlinear processing, and restore the complex baseband signal rxSig idx .

[0136] 2) Take N consecutive complex baseband signals and the transversal filter coefficients Point multiplication to get the filtering result rxSym idx .

[0137]

[0138] 3) Perform maximum likelihood estimation on the filtering results and obtain Extract the difference between the likelihood estimate and the filtered result

[0139]

[0140] 4) Use err idx Update the transverse filter coefficients. The update algorithm varies depending on the equalization algorithm. See LMS equalization or CMA equalization.

[0141] 5) rxSym idx is the demodulated output result after equalization.

[0142] Figure 5 、 Figure 6 Describe the performance of this method, Figure 5 The signal is passed through the Saleh channel model and then the linear and nonlinear equalization results are used. Figure 6 It is the equalization performance of the actual signal after passing through the actual channel. It can be seen that the equalization method described in the present invention can greatly improve the demodulation index.

[0143] As described above, the present invention can be preferably implemented.

[0144] All features disclosed in all embodiments in this specification, or steps in all methods or processes implicitly disclosed, except for mutually exclusive features and / or steps, can be combined and / or expanded or replaced in any manner.

[0145] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Based on the technical essence of the present invention and within the spirit and principles of the present invention, any simple modification, equivalent replacement and improvement of the above embodiment shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A nonlinear satellite channel equalization method, characterized in that: The following steps are involved: S1, AD sampling: use analog-to-digital conversion circuit to sample the transmitted signal and restore the analog signal to a digital signal; S2, pre-equalization: offset the nonlinear distortion of the sampled digital signal; S3, demodulation: demodulate the pre-equalized digital signal; S4, post-equalization: a polyphase transverse filtering structure is used to perform linear equalization on the linear part of the demodulated data; Pre-equalization includes two working modes, namely, the human-involved self-calibration mode and the unmanned working mode: in the self-calibration mode, the transmitter sends a known signal to make all the coefficients of the pre-equalization and post-equalization converge according to the channel characteristics. The goal is to minimize the mean square error between the received signal and the transmitter signal. When the mean square error of the demodulated signal fluctuates within the set range, the self-calibration mode is completed; in the working mode, the pre-equalization coefficient is fixed, and the input signal is adaptively equalized by adjusting the post-equalization, and the result after equalization is the demodulated output.

2. A nonlinear satellite channel equalization method according to claim 1, characterized in that: It is characterized in that In step S2, the pre-equalization uses a multi-phase transversal filtering structure to offset the nonlinear distortion of the received digital signal.

3. A nonlinear satellite channel equalization method according to claim 2, characterized in that: In step S2, in the self-calibration mode, the carrier frequency of the known signal at the transmitting end is an integer multiple of the sampling rate of the analog-to-digital conversion circuit, the symbol rate of the known signal at the transmitting end is an integer multiple of the sampling rate of the analog-to-digital conversion circuit, and the modulation system of the known signal at the transmitting end is high-order modulation.

4. A nonlinear satellite channel equalization method according to claim 3, characterized in that: It is characterized in that In step S2, the pre-equalizer compares the distance between the received signal and the known signal at the transmitting end to obtain a nonlinear equalization error, and uses the error to adjust the coefficient of the equalization filter.

5. A nonlinear satellite channel equalization method according to claim 4, characterized in that: Post-equalization includes the following steps: S41, perform timing synchronization and carrier synchronization on the signal after nonlinear processing to restore the complex baseband signal rxSig idx ; Among them, idx is the operation time in time sequence; S42, take N consecutive complex baseband signals and the transverse filter coefficients Point multiplication to get the filtering result rxSym idx : Wherein, k is the index of the nonlinear combination vector, N is the number of complex baseband signals, and j is the serial number of the complex baseband signal; S43, perform maximum likelihood estimation on the filtering result to obtain Extract the difference between the likelihood estimate and the filtered result: Among them, err idx is the error between the maximum likelihood estimate and the actual filtering result, is the maximum likelihood estimate of the filtering result; S44, use err idx For the transverse filter coefficient to update.

6. A nonlinear satellite channel equalization system, characterized in that: A nonlinear satellite channel equalization method for implementing claim 4 or 5, comprising the following modules connected in sequence: AD sampling module: used to sample the transmission signal using an analog-to-digital conversion circuit and restore the analog signal to a digital signal; Pre-equalization module: used to offset the nonlinear distortion of the sampled digital signal; Demodulation module: used to demodulate the pre-equalized digital signal; Post-equalization module: It is used to perform linear equalization processing on the linear part of the demodulated data using a multi-phase transverse filtering structure.

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