Method, system, device and medium for Ku-band satellite chain downlink signal interference suppression

Abstract

The application discloses a Ku-band satellite chain downlink signal interference suppression method, system, device and medium, and relates to the technical field of wireless communication signal processing. First, an OFDM signal from a satellite chain system is received, the OFDM signal is segmented, and fast Fourier transform is performed on the segmented signal to convert the segmented signal into a frequency domain to obtain a frequency domain signal. Then, an FCME algorithm is used to preliminarily locate a narrow-band interference frequency of the frequency domain signal to obtain an interference range. Further, a frequency offset value is calculated by using an interference frequency determined by DTFT, and then, spectrum shifting is performed on the frequency domain signal according to the frequency offset value, and interference alignment is completed through the spectrum shifting, so that interference suppression of the Ku-band satellite chain downlink signal is realized while spectrum leakage is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication signal processing, in particular to a Ku-band Starlink downlink signal interference suppression method, system, device and medium. BACKGROUND

[0002] The Starlink system is a mature commercial low-orbit satellite communication system that can provide satellite Internet services worldwide. The Starlink system uses a 10.7 GHz to 12.75 GHz frequency range in the Ku band for downlink communication to transmit data on the satellite to the ground user terminal. However, a huge constellation like Starlink, which has a large scale and time-varying communication links, has a large number of interference sources and strong dynamic characteristics in the inter-constellation and intra-constellation interference problems.

[0003] Traditional interference detection methods can be divided into time domain methods and frequency domain methods. Among them, the frequency domain method mostly uses the Forward Continuous Mean Elimination (FCME) algorithm and its improved algorithm to detect narrowband interference, and then uses zeroing method, scaling method and other interference suppression methods to process the detected interference signals to reduce the impact of interference on communication signals. However, this detection method ignores the frequency spectrum leakage problem of the interference signal when the signal is truncated and subjected to Fast Fourier Transform (FFT) transformation. This leakage causes all subcarriers to be affected by interference.

[0004] In the satellite-ground communication scenario, the ground satellite terminal is limited by both power consumption and hardware performance. In this case, it is undoubtedly of practical significance to explore an interference suppression method that has low complexity and guarantees good performance.

[0005] In order to avoid the influence of spectrum leakage in the interference suppression process, the traditional continuous interference suppression algorithm is based on hard decision to estimate the subcarrier interference in turn, then linearly predicts the interference estimation results of the previous k subcarriers, and iteratively feeds back the interference estimation results to improve the interference estimation accuracy and reduce the interference spectrum leakage, so as to improve the system interference suppression performance, but the use of hard decision will lose a lot of useful information, resulting in that the interference suppression performance cannot be greatly improved. In addition, the interference suppression technology based on modulated lapped biorthogonal transform (MLBT, Modulated Lapped Biorthogonal Transform) has better bit error rate performance and stronger robustness to interference frequency offset compared with the traditional FFT, but the calculation complexity of MLBT is much higher than that of FFT. In addition, there is an orthogonal frequency division multiplexing (OFDM, Orthogonal Frequency Division Multiplexing) narrowband interference cancellation technology based on interference alignment, but how to detect the frequency of the interference signal is not analyzed.

[0006] There are still many challenges in the suppression method of narrowband interference, which are as follows:

[0007] 1. The traditional method of using a prediction error filter to detect interference in the time domain needs to be iterated several times to achieve good interference detection performance, which has long convergence time and high calculation complexity, and is not suitable for application in satellites which are limited in power consumption and hardware performance.

[0008] 2. When detecting interference in the signal, the frequency domain detection algorithm represented by FCME ignores the spectrum leakage problem caused by misaligned OFDM subcarrier frequencies. Taking narrowband interference as an example, when the interference power is large, many subcarriers near the corresponding interference frequency point are also strongly interfered due to spectrum leakage, resulting in poor interference suppression effect.

[0009] 3. Some existing methods to avoid spectrum leakage in the interference suppression process have poor performance or high calculation complexity, which are not suitable for application in satellite-terrestrial communication scenarios.

[0010] 4. There is a method of using interference alignment to avoid spectrum leakage, but this method needs to accurately estimate the frequency of narrowband interference, and using a longer FFT point number or using ZOOM-FFT (Zoom Fast Fourier Transform) to increase the spectral resolution faces the problem of high calculation complexity.

[0011] 5. Even if spectrum alignment is performed, a small amount of spectrum leakage will still occur due to the impact of alignment accuracy. Most existing methods only set the aligned interference frequency to zero, but ignore the fact that several surrounding subcarriers may still be affected by spectrum leakage. Summary of the Invention

[0012] Based on the problems raised in the background technology above, the purpose of this invention is to provide a method, system, device and medium for suppressing Ku-band Starlink downlink signal interference, which solves the problem of spectral leakage that occurs when the OFDM subcarrier frequency is not aligned, which is ignored in the prior art.

[0013] This invention is achieved through the following technical solution:

[0014] The first aspect of this invention provides a method for suppressing Ku-band Starlink downlink signal interference, comprising the following steps:

[0015] Receive OFDM signals based on starlink frame structure, segment the OFDM signals to obtain segmented signals;

[0016] Perform a Fast Fourier Transform on the segmented signal to obtain the frequency domain signal;

[0017] The FCME algorithm is used to locate the narrowband interference frequency of the frequency domain signal and obtain the interference range.

[0018] The DTFT algorithm is used to locate the narrowband interference frequency of the frequency domain signal within the interference range, thereby obtaining the interference frequency.

[0019] Calculate the frequency offset value based on the interference frequency, and perform spectrum shifting on the frequency domain signal based on the frequency offset value to obtain a spectrum-shifted signal.

[0020] The spectrum-shifted signal is subjected to inverse Fourier transform and inverse spectrum shift in sequence to obtain a narrowband interference suppression signal.

[0021] In the above technical solution, firstly, OFDM (Orthogonal Frequency Division Multiplexing) signals from the Starlink system are received. The OFDM signals are transmitted in the form of Starlink frame structure (i.e., Starlink frame structure). The OFDM signals are segmented, and the segmented signals are subjected to Fast Fourier Transform to convert the segmented signals to the frequency domain, thus obtaining frequency domain signals. At this time, the frequency domain signals are the segmented signals in the frequency domain.

[0022] Then, the FCME algorithm is used to preliminarily locate the narrowband interference frequency of the frequency domain signal to obtain an interference range. However, only using the FCME algorithm to locate the interference of the signal, due to the limited accuracy of the interference frequency estimation, spectrum leakage occurs when the FFT is transformed, resulting in poor interference suppression effect. Therefore, the FCME algorithm is used to preliminarily locate the narrowband interference frequency of the frequency domain signal to determine the range of the interference frequency, and then the DTFT (Discrete-Time Fourier Transform) algorithm is used to perform spectrum refinement in the interference range, thereby further locating the narrowband interference frequency, so as to obtain a more accurate interference frequency.

[0023] Further, the interference frequency determined by the DTFT is used to calculate a frequency offset value, and then the frequency domain signal (i.e., the segmented signal in the frequency domain) is spectrum shifted according to the frequency offset value, and the interference is aligned through the spectrum shifting, thereby realizing the interference suppression of the Ku band satellite downlink signal.

[0024] Finally, the spectrum shifted signal is sequentially inverse Fourier transformed and spectrum inversely shifted, at this time, the suppression of the narrowband interference is completed.

[0025] In an optional embodiment, the OFDM signal is segmented, including the following steps:

[0026] The symbol length of the OFDM signal is determined, and the OFDM signal is segmented according to the symbol length;

[0027] The cyclic prefix in the segmented OFDM signal is deleted to obtain a segmented signal.

[0028] In an optional embodiment, the FCME algorithm is used to locate the narrowband interference frequency of the frequency domain signal, including the following steps:

[0029] Step A, the frequency domain signal is arranged in ascending order according to the spectral line amplitude of the frequency domain signal, and the minimum spectral line amplitude is extracted from the frequency domain signal arranged in ascending order;

[0030] Step B, the frequency points corresponding to the minimum spectral line amplitude in the frequency domain signal are taken as a first non-interference frequency point set, and the remaining frequency points in the frequency domain signal are taken as a first interference frequency point set;

[0031] Step C, the first non-interference frequency point set is calculated to obtain a decision threshold;

[0032] ​​Step D, removing all decision elements in the first interfered frequency point set to generate a second interfered frequency point set, and combining all decision elements with the first non-interfered frequency point set to generate a second non-interfered frequency point set;

[0033] Step E, if the second interfered frequency point set and the second non-interfered frequency point set remain stable, extracting a frequency point with a maximum amplitude from the second interfered frequency point set, and generating an interference range based on the frequency point with the maximum amplitude; otherwise, repeating steps C to D.

[0034] In an optional embodiment, a narrowband interference frequency positioning algorithm is used to locate the interference frequency in the interference range, including the following steps:

[0035] Setting a frequency resolution;

[0036] Calculating a spectrum refinement multiple according to the frequency resolution and the interference range;

[0037] Refining the spectrum of the frequency domain signal using the spectrum refinement multiple, and determining the interference frequency according to the result of the spectrum refinement; wherein the process of spectrum refinement is as follows:

[0038] ;

[0039] In the above formula, represents a frequency domain signal, represents a time domain discrete signal, represents a discrete sampling point, represents the length of an OFDM symbol without a cyclic prefix, i.e., the number of subcarriers, represents an imaginary unit, represents an analog frequency, represents a spectrum refinement multiple, represents a frequency resolution, represents the minimum value of an interference range, represents an index variable of a discrete frequency scan, represents a sampling rate.

[0040] In an optional embodiment, the spectrum refinement multiple is calculated according to the frequency resolution and the interference range, including:

[0041] ;

[0042] In the above formula, represents a spectrum refinement multiple, represents the larger value of an interference range.

[0043] In an alternative embodiment, the spectrum shifting of the frequency domain signal according to the frequency offset value comprises:

[0044] ;

[0045] In the above formula, represents the difference between the estimated interference frequency and the normalized value of the closest subcarrier frequency, represents the size of the shifted frequency, represents the segmented signal of the received signal ; represents the signal after spectrum shifting processing.

[0046] In an alternative embodiment, after obtaining the spectrum shifted signal, further comprising:

[0047] performing residual spectrum leakage detection on the spectrum shifted signal to obtain a residual spectrum leakage set;

[0048] calculating the power of the non-interference frequency points in the first non-interference frequency point set; wherein the first non-interference frequency point set is determined by the FCME algorithm;

[0049] scaling and suppressing the residual spectrum leakage set using the power.

[0050] The second aspect of the present application provides a Ku-band satellite constellation downlink signal interference suppression system, comprising:

[0051] a segmentation module for receiving an OFDM signal based on a satellite constellation frame structure, segmenting the OFDM signal to obtain a segmented signal;

[0052] a signal transformation module for performing fast Fourier transform on the segmented signal to obtain a frequency domain signal;

[0053] a preliminary positioning module for performing narrowband interference frequency positioning on the frequency domain signal using the FCME algorithm to obtain an interference range;

[0054] a fine positioning module for performing narrowband interference frequency positioning on the frequency domain signal within the interference range using the DTFT algorithm to obtain an interference frequency;

[0055] a signal shifting module for calculating a frequency offset value according to the interference frequency, and performing spectrum shifting of the frequency domain signal according to the frequency offset value to obtain a spectrum shifted signal;

[0056] ​​A signal inverse transform module is configured to sequentially perform inverse Fourier transform and spectrum inverse shifting on the spectrum shifted signal to obtain a narrowband interference suppression signal.

[0057] The third aspect of the present application provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the Ku band satellite downlink signal interference suppression method when executing the computer program.

[0058] The fourth aspect of the present application provides a computer readable storage medium, which stores a computer program, wherein the computer program is executable on a processor to implement the Ku band satellite downlink signal interference suppression method.

[0059] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0060] 1. The present application further determines the interference frequency by calculating the spectrum refinement multiple and performing spectrum refinement based on the spectrum refinement multiple;

[0061] 2. The present application calculates the frequency offset value using the interference frequency determined by DTFT, and then performs spectrum shifting on the frequency domain signal according to the frequency offset value, thereby completing the interference alignment and realizing the interference suppression of the Ku band satellite downlink signal without spectrum leakage;

[0062] 3. To prevent the problem of spectrum leakage in the FFT process caused by incomplete interference alignment due to limited interference frequency estimation accuracy, the present application performs FCME interference detection again near the corresponding subcarrier after interference alignment, and uses scaling method to suppress the interference. Unlike the traditional method of setting the target subcarrier of interference alignment to zero, the present application improves the robustness of interference suppression and enhances the interference suppression effect. BRIEF DESCRIPTION OF DRAWINGS

[0063] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as limiting the scope. For those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0064] Figure 1 The frame diagram of the FCME-DTFT algorithm provided for the first embodiment of the present application;

[0065] Figure 2 The flow diagram of the Ku band satellite downlink signal interference suppression method provided for the first embodiment of the present application;

[0066] Figure 3 A schematic diagram of the relationship between the energy concentration rate and the subcarrier size deviating from an integer multiple provided for the embodiment 1 of the present application is shown in the figure.

[0067] Figure 4 A comparison diagram of the spectrum refinement complexity provided for the embodiment 1 of the present application is shown in the figure.

[0068] Figure 5 A structural schematic diagram of an electronic device provided for the embodiment 3 of the present application is shown in the figure. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical scheme and advantages of the present application clearer, further detailed description will be given below in combination with embodiments and drawings, and the schematic embodiments of the present application and the description thereof are only used for explaining the present application, and do not limit the present application.

[0070] Embodiment 1

[0071] The embodiment 1 of the present application provides a Ku-band satellite chain downlink signal interference suppression method, which comprises the following steps:

[0072] An OFDM signal based on a satellite chain frame structure is received, and the OFDM signal is segmented to obtain a segmented signal;

[0073] Fast Fourier transform is performed on the segmented signal to obtain a frequency domain signal;

[0074] An FCME algorithm is used to locate a narrowband interference frequency of the frequency domain signal to obtain an interference range;

[0075] A DTFT algorithm is used to locate a narrowband interference frequency of the frequency domain signal in the interference range to obtain an interference frequency;

[0076] A frequency offset value is calculated according to the interference frequency, and a spectrum shift is performed on the frequency domain signal according to the frequency offset value to obtain a spectrum shifted signal;

[0077] Inverse Fourier transform and spectrum inverse shift are sequentially performed on the spectrum shifted signal to obtain a narrowband interference suppression signal.

[0078] It should be noted that at present, when the Ku band satellite chain downlink signal is interfered, the problem of spectrum leakage caused by fast Fourier transform when the OFDM signal is aligned with the subcarrier frequency is ignored, and due to the spectrum leakage, many subcarriers near the corresponding interference frequency point are also strongly interfered, so that many subcarriers outside the interference frequency point are also interfered, and after the interference suppression operation, a large amount of useful information is destroyed, finally the communication performance is reduced, so that the effect of signal interference suppression is not good. Therefore, aiming at the problem of spectrum leakage, a Ku band satellite chain downlink signal interference suppression method is proposed, as shown in Figure 1 As shown in the figure, first, OFDM signals (OFDM, Orthogonal Frequency Division Multiplexing) from the satellite system are received, wherein the OFDM signals are transmitted in the form of the frame structure of the satellite system, that is, the satellite frame structure; the segmented signals after segmentation are subjected to fast Fourier transform to convert the segmented signals into frequency domain to obtain frequency domain signals, at this time, the frequency domain signals are segmented signals in the frequency domain.

[0079] Then, the FCME algorithm is used to preliminarily locate the narrowband interference frequency of the frequency domain signal to obtain the interference range; however, only using the FCME algorithm to locate the interference of the signal will lead to poor interference suppression effect due to spectrum leakage. Therefore, after the FCME algorithm is used to preliminarily locate the narrowband interference frequency of the frequency domain signal to determine the range of the interference frequency, the DTFT (Discrete-Time Fourier Transform) algorithm is used to perform spectrum refinement within the interference range, and further narrowband interference frequency positioning is realized, so that more accurate interference frequency is obtained.

[0080] Further, the frequency offset value is calculated by using the interference frequency determined by the DTFT, and then the frequency domain signal (i.e. the segmented signal in the frequency domain) is subjected to spectrum shift according to the frequency offset value, and the interference alignment is completed through the spectrum shift, so that the interference suppression of the Ku band satellite chain downlink signal is realized without spectrum leakage.

[0081] Finally, the spectrum shift signal is subjected to inverse Fourier transform and spectrum inverse shift in sequence, at this time, one time of narrowband interference suppression is completed.

[0082] Further, the spectrum shift and inverse Fourier transform and spectrum inverse shift are repeated until all the narrowband interference determined by the FCME-DTFT algorithm is subjected to one time of suppression operation, and the OFDM signal after the narrowband interference suppression is output.

[0083] In an alternative embodiment, the OFDM signal is segmented, including the following steps:

[0084] The symbol length of the OFDM signal is determined, and the OFDM signal is segmented according to the symbol length;

[0085] The cyclic prefix in the segmented OFDM signal is removed to obtain a segmented signal.

[0086] It should be noted that the OFDM (Orthogonal Frequency Division Multiplexing) symbol length is determined by the number of subcarriers and the subcarrier spacing; the smaller the subcarrier spacing, the longer the symbol length. In this embodiment, the symbol length of each OFDM signal based on the Starlink frame structure is 1056, which includes a 32-point cyclic prefix, so the segmentation length is set to 1056 according to the symbol length, and the OFDM signal is segmented by the segmentation length, and the cyclic prefix is removed after segmentation, thereby obtaining the time domain expression of the segmented signal of the first OFDM symbol .

[0087] ;

[0088] ;

[0089] In the above formula, represents the OFDM signal, represents the interference signal, represents the noise, represents the received signal, represents the number of OFDM subcarriers, represents the cyclic prefix length, represents the discrete sampling point.

[0090] As Figure 2 shown, after the OFDM signal is divided, the segmented signal obtained is a time domain signal, therefore, the segmented signal is subjected to 1024-point FFT (Fast Fourier Transform) transformation to obtain a frequency domain signal .

[0091] Further, considering that noise may affect the size of the spectral line value, in order to prevent subsequent missed detection, in this embodiment, the frequency domain signal is subjected to sliding filtering to obtain a sliding filtered frequency domain signal .

[0092] In an alternative embodiment, the FCME algorithm is used to locate the narrowband interference frequency of the frequency domain signal, including the following steps:

[0093] Step A, arranging the frequency domain signal in ascending order according to the spectral line amplitudes of the frequency domain signal, extracting the minimum spectral line amplitudes from the frequency domain signal arranged in ascending order;

[0094] Step B, taking the frequency points corresponding to the minimum spectral line amplitudes in the frequency domain signal as a first set of non-interfered frequency points, and taking the remaining frequency points in the frequency domain signal as a first set of interfered frequency points;

[0095] Step C, calculating the first set of non-interfered frequency points to obtain a decision threshold;

[0096] Step D, taking the frequency points smaller than the decision threshold in the first set of interfered frequency points as decision elements, removing all decision elements in the first set of interfered frequency points to generate a second set of interfered frequency points, and merging all decision elements with the first set of non-interfered frequency points to generate a second set of non-interfered frequency points;

[0097] Step E, if the second set of interfered frequency points and the second set of non-interfered frequency points remain stable, extracting the frequency point with the maximum amplitude from the second set of interfered frequency points, and generating an interference range based on the frequency point with the maximum amplitude; otherwise, repeating steps C to D.

[0098] It should be noted that the purpose of this step is to find the approximate frequency position of narrowband interference using the FCME algorithm. In this embodiment, the frequency domain signal is first arranged in ascending order according to the spectral line amplitudes, where the spectral line amplitude of the frequency domain signal refers to the amplitude of each frequency component in the frequency domain representation of the signal, which reflects the energy distribution of the signal at different frequencies. In this embodiment, it is considered that the frequency points corresponding to small spectral line amplitudes are not interfered, and the frequency points corresponding to large spectral line amplitudes are interfered, so the frequency points corresponding to the minimum spectral line amplitudes are taken as the first set of non-interfered frequency points , and the remaining frequency points are taken as the first set of interfered frequency points .

[0099] Since the interference detection of the FCME algorithm is realized by continuous iteration, in the first iteration process, the first set of non-interfered frequency points is calculated to obtain a decision threshold .

[0100] Specifically, the calculation process of the decision threshold is as follows:

[0101] ;

[0102] ;

[0103] In the above formula, Indicates the probability of a false alarm. Represents the threshold factor. Represents the first set of undisturbed frequency points The number of elements in It is the amplitude sequence obtained after applying a moving average filter to the spectral line amplitudes. In OFDM, the first Subcarriers.

[0104] It should be noted that, for frequency domain interference, missed detections are more detrimental to the performance of OFDM system links than false alarms. Therefore, in this embodiment, moving average filtering is used to prevent missed detections.

[0105] After obtaining the decision threshold, based on the decision threshold The elements in the first set of interfered frequency points are judged. If the spectral amplitude of an element in the first set of interfered frequency points is less than a threshold, it is considered that it is not interfered with and is set as a judgment element. All judgment elements are removed from the first set of interfered frequency points (i.e., the frequency points judged as not being interfered with are removed), and the remaining frequency points constitute the second set of interfered frequency points. At the same time, all judgment elements are merged with the first set of uninterrupted frequency points to generate the second set of uninterrupted frequency points.

[0106] Specifically, the second set of uninterrupted frequency points and the second set of interfered frequency points The following was generated:

[0107] ;

[0108] ;

[0109] If the second set of uninterrupted frequency points and the second set of interfered frequency points If the second set of interfered frequencies no longer contains any undisturbed frequencies, it is considered to be stable. Then, the frequency with the maximum spectral amplitude is found in the second set of interfered frequencies. The frequency corresponding to each maximum value is regarded as a rough estimate of the narrowband interference frequency, thereby determining the interference range.

[0110] If the second set of uninterrupted frequency points and the second set of interfered frequency points If stability is not maintained (i.e., the second set of interfered frequencies contains undisturbed frequencies), then steps C to D are repeated. A decision threshold is calculated for the second set of undisturbed frequencies. Then, based on the decision threshold, a decision is made on the elements in the second set of interfered frequencies. The decided elements are removed from the second set of interfered frequencies, and the decided elements are merged with the second set of undisturbed frequencies. This process continues... After the nth iteration, the th Uninterrupted frequency set and the Set of Interference Frequency Points If the elements in the array are relatively fixed and no longer change, then it is assumed that all interference has been identified, and the output is the first... Set of Interference Frequency Points This is used to determine the range of interference.

[0111] Furthermore, the interference range is determined as follows: a stable set of interfered frequency points is found using the FCME algorithm, and then the frequency points with the maximum spectral amplitude are found from the set of interfered frequency points. The frequency point corresponding to each maximum value is regarded as a rough estimate of the narrowband interference frequency. Based on the rough estimate frequency, the two peak positions with the largest interference spectral amplitude are selected on both sides, and the interval formed between the two peak positions is set as the interference range.

[0112] ;

[0113] The set of interference frequency points was found in the above formula. The frequency corresponding to the strongest spectral line in the mid-spectral range However, due to spectral leakage, the signal's energy diffuses from its true frequency components to adjacent frequency components. In this embodiment, the estimated frequency... In reality, it's just the subcarrier frequency closest to the actual interference frequency. To investigate the range of the actual frequency, comparisons are needed. left side and the right side The two subcarriers correspond to the magnitudes of their spectral amplitudes. The actual interference frequency must be taken at... Between the side with the larger amplitude in the mid-frequency domain on the left and right, let the true frequency range be [ , If the right side is greater than the left side, then , ,on the contrary, , .

[0114] In one optional embodiment, the DTFT algorithm is used to locate the narrowband interference frequency of the frequency domain signal within the interference range, including the following steps:

[0115] set a frequency resolution;

[0116] calculate a spectrum refinement factor according to the frequency resolution and the interference range;

[0117] perform spectrum refinement on the frequency domain signal using the spectrum refinement factor, and determine an interference frequency according to a result of the spectrum refinement; wherein the spectrum refinement is performed according to the following equation:

[0118]

[0119] In the above equation, denotes the frequency domain signal, denotes the time domain discrete signal, denotes a discrete sampling point, denotes the OFDM symbol length without cyclic prefix, i.e., the number of subcarriers, denotes the imaginary unit, denotes the analog frequency, and its value is equal to , denotes the spectrum refinement factor, denotes the frequency resolution, denotes the minimum value of the interference range, denotes an index variable of the discrete frequency scanning, denotes the sampling rate.

[0120] In an alternative embodiment, calculating the spectrum refinement factor according to the frequency resolution and the interference range comprises:

[0121]

[0122] In the above equation, denotes the spectrum refinement factor, denotes the larger value of the interference range.

[0123] It should be noted that the spectrum refinement factor and the computational complexity are positively correlated when the DTFT algorithm is used to perform spectrum refinement, and therefore, it is essential to find a suitable spectrum refinement factor size to achieve a balance between performance and computational complexity.

[0124] For a narrowband interference, its expression after being discretized and windowed is:

[0125]

[0126] In the above equation, denotes the narrowband interference, denotes the difference between the normalized value of the interference frequency and the closest subcarrier frequency, and its value is [-0.5, 0.5], ​​​​denotes the narrowband interference signal amplitude, denotes the interference frequency, denotes the discrete sampling point, denotes the sampling period, denotes the initial phase of the interference signal, denotes the interference, denotes the number of subcarriers of the satellite link.

[0127] The spectral analysis of it can get the corresponding spectrum :

[0128] ;

[0129] wherein, the spectral line amplitude of

[0130] ;

[0131] Take the discrete frequency , then the continuous spectrum becomes

[0132] ;

[0133] When , the interference only affects one subcarrier, and has no effect on the data on other subcarriers. The interference can be removed by directly setting it to zero. When , the interference leaks, and the leaked energy needs to be considered. At this time, the maximum leakage energy is at the subcarrier , and the energy concentration rate is denoted by , the total energy of the interference is , and the total energy of the interference is denoted as:

[0134] ;

[0135] ;

[0136] Take the number of subcarriers of the satellite link , the energy concentration rate and the deviation from the integer multiple of the subcarrier size are plotted as shown in Figure 3 . The energy concentration rate is directly related to the deviation from the integer multiple of the subcarrier size . When , at this time, . This means that the leaked energy is less than 1%. In order to achieve the frequency estimation accuracy of , the spectral refinement multiple needs to be more than 10.

[0137] Therefore, in this embodiment, a frequency resolution is determined, where the frequency resolution is the minimum interval that can distinguish two different frequency signals. The spectral refinement factor is determined jointly by the frequency resolution and the interference range.

[0138] This embodiment uses the number of complex multiplications as a reference to compare the spectral refinement complexity of the FFT-DTFT algorithm used in this embodiment with that of existing technologies such as Chirp-Z Transform (CZT, linear frequency modulated Z-transform) and Zoom-FFT. The comparison results are as follows: Figure 4 As shown, the complexity of Zoom-FFT is higher than that of DTFT at any refinement factor. Comparing the complexity of CZT and DTFT spectrum refinement algorithms reveals that DTFT has lower complexity when the refinement factor is less than 25. The analysis above showed that when the refinement factor reaches 10, the estimated frequency accuracy ensures that the energy leakage after FFT transformation following interference alignment is less than 1%. In power- and performance-constrained scenarios like satellites, DTFT is chosen to refine the spectrum by a factor of 10 to accurately estimate the specific value of the interference frequency.

[0139] In one optional embodiment, spectral shifting of the frequency domain signal based on the frequency offset value includes: ;

[0140] ;

[0141] In the above formula, This represents the difference between the estimated interference frequency and the normalized value of its nearest subcarrier frequency. Indicates the frequency of relocation. Indicates the received signal After segmentation, the first segment signal, Indicates to The signal after spectrum shifting.

[0142] It should be noted that by calculating the interference frequency, the frequency offset value of the interference frequency relative to the subcarrier is obtained. This frequency offset value is used to perform spectrum shifting on the frequency domain signal in the segmented state, so as to shift the narrowband interference signal to the frequency point where the subcarrier is located to eliminate spectrum leakage.

[0143] In one alternative embodiment, after obtaining the spectrum-shifted signal, the process further includes:

[0144] Residual spectral leakage is detected in the spectrum-shifted signal to obtain a residual spectral leakage set;

[0145] Calculate the first The power of the undisturbed frequency points in the set of undisturbed frequency points; wherein, the first The set of unaffected frequency points was determined using the FCME algorithm;

[0146] The residual spectral leakage set is scaled and suppressed using the power.

[0147] like Figures 1-2 As shown, when performing FFT on the spectrum-shifted signal after spectrum shifting, due to the limited accuracy of interference frequency estimation, there may still be some spectrum leakage near the target-aligned subcarrier. Therefore, the FCME algorithm is used to detect whether there is spectrum leakage in the two subcarriers near the target-aligned subcarrier, and the frequency points with spectrum leakage are put into the residual spectrum leakage set.

[0148] Among them, the Power of uninterrupted frequencies in the set of uninterrupted frequencies The calculation is as follows:

[0149] ;

[0150] In the above formula, Indicates to The frequency domain signal obtained after performing spectral analysis This indicates the number of OFDM subcarriers.

[0151] Then, for the residual spectral leakage set Scaling suppression is applied, and the amplitude of each interfered frequency point is reduced after scaling suppression. for:

[0152] ;

[0153] This completes the suppression of interference from the remaining spectral leakage.

[0154] The suppressed frequency domain data is transformed into the time domain using the inverse fast fourier transform (IFFT), and then the time domain signal is processed... The spectrum is reversed, which completes the suppression of narrowband interference.

[0155] Example 2

[0156] Embodiment 2 of the present invention provides a Ku-band Starlink downlink signal interference suppression system, comprising:

[0157] The segmentation module is used to receive OFDM signals based on the starlink frame structure, segment the OFDM signals, and obtain segmented signals.

[0158] The signal transformation module is configured to perform fast Fourier transform on the segmented signal to obtain a frequency domain signal.

[0159] The initial positioning module is configured to perform narrowband interference frequency positioning on the frequency domain signal by using the FCME algorithm to obtain an interference range.

[0160] The fine positioning module is configured to perform narrowband interference frequency positioning on the frequency domain signal in the interference range by using the DTFT algorithm to obtain an interference frequency.

[0161] The signal shift module is configured to calculate a frequency offset value according to the interference frequency, and perform frequency spectrum shift on the frequency domain signal according to the frequency offset value to obtain a frequency spectrum shifted signal.

[0162] The signal inverse transformation module is configured to perform inverse Fourier transform and frequency spectrum inverse shift on the frequency spectrum shifted signal in sequence to obtain a narrowband interference suppression signal.

[0163] Embodiment 3

[0164] Figure 5 A structural schematic diagram of an electronic device provided for Embodiment 3 is shown in FIG. 3. Figure 5 As shown in FIG. 3, the electronic device includes a processor 21, a memory 22, an input device 23, and an output device 24; the number of processors 21 in the computer device can be one or more, and one processor 21 is taken as an example in the embodiment. Figure 5 The processor 21, the memory 22, the input device 23, and the output device 24 in the electronic device can be connected through a bus or other means, and the connection through the bus is taken as an example in the embodiment. Figure 5

[0165] The memory 22 is a kind of computer readable storage medium, which can be used to store software programs, computer executable programs, and modules. The processor 21 performs various functions of the electronic device and data processing by running the software programs, instructions, and modules stored in the memory 22, that is, the Ku band Starlink downlink signal interference suppression method of Embodiment 1 is implemented.

[0166] The memory 22 can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system and at least one application required by a function; the data storage area can store data created according to the use of the terminal, etc. In addition, the memory 22 can include a high-speed random access memory, and can also include a non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some examples, the memory 22 can further include a memory remotely arranged with respect to the processor 21, which can be connected to the electronic device through a network. Examples of the above-mentioned network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.​

[0167] The input device 23 can be used to receive the id and password input by the user, etc. The output device 24 is used to output the network configuration page.

[0168] Embodiment 4

[0169] The embodiment 4 of the present application also provides a computer readable storage medium, and the computer executable instructions are used to implement the Ku band star chain downlink signal interference suppression method provided by the embodiment 1 when executed by the computer processor.

[0170] The storage medium provided by the embodiment of the present application contains computer executable instructions, which are not limited to the method operations provided by the embodiment 1, and can also perform the related operations in the Ku band star chain downlink signal interference suppression method provided by any embodiment of the present application.

[0171] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method of Ku-band satellite downlink signal interference suppression, characterized by, The method comprises the following steps: receiving an OFDM signal based on a star chain frame structure, segmenting the OFDM signal to obtain a segmented signal; performing fast Fourier transform on the segmented signal to obtain a frequency domain signal; performing narrowband interference frequency positioning on the frequency domain signal by using an FCME algorithm to obtain an interference range; performing narrowband interference frequency positioning on the frequency domain signal in the interference range by using a DTFT algorithm to obtain an interference frequency; wherein performing narrowband interference frequency positioning on the frequency domain signal in the interference range by using the DTFT algorithm comprises the following steps: setting a frequency resolution; calculating a spectrum refinement multiple according to the frequency resolution and the interference range; The frequency domain signal is spectrum-refined by using the spectrum refinement multiple, and an interference frequency is determined according to a spectrum refinement result; wherein the spectrum refinement process is as follows: ; wherein, represents a frequency domain signal, represents a time domain discrete signal, represents a discrete sampling point, represents an OFDM symbol length without a cyclic prefix, i.e. a subcarrier number, represents an imaginary unit, represents an analog frequency, represents a spectrum refinement multiple, represents a frequency resolution, represents a minimum value of an interference range, represents an index variable of a discrete frequency scan, represents a sampling rate; calculating a spectral refinement factor based on the frequency resolution and the interference range, comprising: ; wherein denotes the spectral refinement factor, denotes the maximum value of the interference range; calculating a frequency offset value according to the interference frequency, performing spectrum shifting on the frequency domain signal according to the frequency offset value to obtain a spectrum shifted signal; performing inverse Fourier transform and spectrum inverse shifting on the spectrum shifted signal in sequence to obtain a narrowband interference suppression signal.

2. The Ku-band direct broadcast satellite downlink signal interference mitigation method of claim 1, wherein, segmenting the OFDM signal comprises the following steps: determining the symbol length of the OFDM signal, and segmenting the OFDM signal according to the symbol length; deleting the cyclic prefix in the segmented OFDM signal to obtain a segmented signal.

3. The Ku-band direct broadcast satellite downlink signal interference mitigation method of claim 1, wherein, performing narrowband interference frequency positioning on the frequency domain signal by using an FCME algorithm comprises the following steps: Step A, arranging the frequency domain signal in ascending order according to the spectral line amplitudes of the frequency domain signal, extracting the minimum spectral line amplitude from the frequency domain signal arranged in ascending order one minimum spectral line amplitude; Step B, taking the frequency point corresponding to the minimum spectral line amplitude in the frequency domain signal as a first set of non-interfered frequency points and the remaining frequency points in the frequency domain signal as a first set of interfered frequency points. Step B, taking the frequency point corresponding to the minimum spectral line amplitude in the frequency domain signal as a first set of non-interfered frequency points and the remaining frequency points in the frequency domain signal as a first set of interfered frequency points. Step C, calculating the first undisturbed frequency point set to obtain a decision threshold; Step D, regarding the frequency points smaller than the decision threshold in the first disturbed frequency point set as decision elements, removing all decision elements in the first disturbed frequency point set to generate a second disturbed frequency point set, and combining all decision elements with the first undisturbed frequency point set to generate a second undisturbed frequency point set; Step E, if the second disturbed frequency point set and the second undisturbed frequency point set remain stable, extracting the frequency point with the maximum amplitude from the second disturbed frequency point set, and generating an interference range based on the frequency point with the maximum amplitude; otherwise, Steps C to D are repeatedly executed.

4. The Ku-band direct broadcast satellite downlink signal interference mitigation method of claim 1, wherein, The frequency domain signal is frequency-shifted according to the frequency offset value, comprising: ; ; wherein, represents the difference between the estimated interference frequency and the normalized value of the closest subcarrier frequency, represents the size of the frequency shift, represents the segmented signal of the received signal , represents the segmented signal of the received signal , represents the signal after frequency shifting processing.

5. The Ku-band direct broadcast satellite downlink signal interference mitigation method of claim 1, wherein, After obtaining the spectrum shifted signal, the following steps are further included: performing residual spectrum leakage detection on the spectrum shifted signal to obtain a residual spectrum leakage set; calculating the power of the undisturbed frequency point in the mth undisturbed frequency point set; wherein the mth undisturbed frequency point set is determined by the FCME algorithm; scaling and suppressing the residual spectrum leakage set by using the power.

6. A Ku-band satellite downlink signal interference suppression system, characterized by It comprises: a segmentation module configured to receive an OFDM signal based on a star chain frame structure, segment the OFDM signal to obtain a segmented signal; a signal transformation module configured to perform fast Fourier transform on the segmented signal to obtain a frequency domain signal; a preliminary positioning module configured to perform narrowband interference frequency positioning on the frequency domain signal by using an FCME algorithm to obtain an interference range; a fine positioning module configured to perform narrowband interference frequency positioning on the frequency domain signal in the interference range by using a DTFT algorithm to obtain an interference frequency; wherein performing narrowband interference frequency positioning on the frequency domain signal in the interference range by using the DTFT algorithm comprises the following steps: setting a frequency resolution; calculating a spectrum refinement factor according to the frequency resolution and the interference range; The frequency domain signal is spectrum-refined by using the spectrum refinement multiple, and an interference frequency is determined according to a spectrum refinement result; wherein the spectrum refinement process is as follows: ; wherein, represents a frequency domain signal, represents a time domain discrete signal, represents a discrete sampling point, represents an OFDM symbol length without a cyclic prefix, i.e. a subcarrier number, represents an imaginary unit, represents an analog frequency, represents a spectrum refinement multiple, represents a frequency resolution, represents a minimum value of an interference range, represents an index variable of a frequency scanning, represents a sampling rate; calculating a spectral refinement factor based on the frequency resolution and the interference range, comprising: ; wherein denotes the spectral refinement factor, denotes the maximum value of the interference range; a signal shift module, configured to calculate a frequency shift value according to the interference frequency, and to perform spectrum shift on the frequency domain signal according to the frequency shift value to obtain a spectrum shift signal; a signal inverse transform module, configured to perform inverse Fourier transform and spectrum inverse shift on the spectrum shift signal in sequence to obtain a narrowband interference suppression signal.

7. An electronic device, comprising: The computer program is executed by the processor to implement the Ku-band satellite chain downlink signal interference suppression method according to any one of claims 1 to 5.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the Ku-band satellite chain downlink signal interference suppression method according to any one of claims 1 to 5.

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