Frequency hopping signal tracking interference method and device based on time-frequency diagram binaryzation

Abstract

The invention discloses a frequency hopping signal tracking interference method and device based on time-frequency diagram binaryzation, and the method comprises the steps: collecting a data stream of a target signal in real time, carrying out the data preprocessing of the data stream according to the working frequency band of the target signal, and obtaining narrowband IQ complex data; performing time-frequency analysis on the narrowband IQ complex data to obtain a corresponding time-frequency graph, and performing binarization processing on the time-frequency graph to obtain a binarized time-frequency matrix; and for each frequency point of the time-frequency matrix, detecting a frequency hopping signal by using a double sliding window, if the frequency hopping signal is detected, estimating a corresponding frequency hopping parameter, and then generating an interference signal according to the frequency hopping parameter and outputting the interference signal. According to the invention, tracking interference of the frequency hopping signal can be realized with fewer resources.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, in particular to a method based on time-frequency Figure 2 A method and device for tracking interference of a valued frequency hopping signal. Background Art

[0002] In the field of wireless communications, frequency-hopping communication (FH) is the most widely used method for anti-interference communications. It is widely used in shortwave and ultra-shortwave radios, data link technology, Bluetooth, satellite communications, and other fields. It features strong anti-interference capabilities, a low probability of interception, and flexible networking. In recent years, domestic and international researchers have conducted in-depth research on FH interference. They typically employ partial-band or broadband blocking interference to suppress FH systems, reducing their communication range and speed. Broadband power suppression requires higher transmit power, significantly increasing the complexity and cost of the jamming equipment. Furthermore, full-band interference can block one's own communication links.

[0003] In order to solve the problem of frequency hopping broadband interference, a frequency hopping tracking interference is proposed, as shown in the attached Figure 1 As shown. Based on the rapid detection and measurement of the characteristic parameters of the frequency hopping signal, the frequency hopping signal tracking interference guides the generation of the interference signal and achieves the overlap of the frequency hopping signal and the interference signal in the time domain, frequency domain and other dimensions. The frequency hopping signal generally changes the center frequency according to a fixed period. After a period of detection time, the frequency hopping signal is detected. The interference signal is guided to be generated based on the measured parameters such as the center frequency and bandwidth. After power amplification, the output is achieved to achieve the overlap of the interference signal and the frequency hopping signal in the time domain and frequency domain at the receiver input. After continuously transmitting the interference signal for a period of time according to the dwell time of the frequency hopping signal, the interference signal is stopped and the frequency hopping signal is detected again.

[0004] The most common frequency hopping signal tracking interference implementation structure is as follows Figure 2 As shown, the signal receiving and preprocessing module is used to convert the broadband RF signal into an analog intermediate frequency signal with a fixed frequency; the real-time frequency hopping carrier detection module is used to quickly detect the frequency hopping carrier signal in a short time, and generate the interference carrier signal and interference control timing in real time; the real-time interference generation module is used to generate various types of interference suppression signals according to the input carrier frequency; the signal generation and up-conversion module is used to convert the interference suppressed intermediate frequency signal to a certain frequency and output it; the power amplifier module is used to amplify the RF signal and output it through the antenna.

[0005] The core of this implementation structure lies in the detection of frequency hopping signals and real-time detection of characteristic parameters. However, the frequency hopping signal carrier detection method proposed in this method has the following problems in real-time detection and parameter measurement of frequency hopping signals in complex electromagnetic environments: (1) In scenarios where both frequency-hopping signals and fixed-frequency signals exist, the proposed method is difficult to distinguish between fixed-frequency signals and frequency-hopping signals, making it difficult to accurately detect frequency-hopping signals and track and interfere with them. The tracking and interference effect of frequency-hopping signals is poor. (2) Real-time detection and characteristic parameter estimation of frequency hopping signals take up a lot of computing resources, resulting in high costs and difficulty in engineering applications on miniaturized equipment; (3) The noise, burst signal, linear frequency modulation signal, etc. that may exist in a complex environment are not processed, which affects the effectiveness of frequency hopping signal detection and tracking interference. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: In view of the above problems of the prior art, a time-frequency Figure 2 The invention provides a method and device for tracking interference of a frequency hopping signal with a numerical value, which can realize tracking interference of a frequency hopping signal with less resources.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: A time-frequency based Figure 2 The method for tracking interference of a frequency hopping signal with a valued value includes the following steps: Collecting a data stream of a target signal in real time, performing data preprocessing on the data stream according to an operating frequency band of the target signal, and obtaining narrowband IQ complex data; Performing time-frequency analysis on the narrowband IQ complex data to obtain a corresponding time-frequency graph, and performing binarization processing on the time-frequency graph to obtain a binarized time-frequency matrix; A double sliding window is used to detect the frequency hopping signal for each frequency point of the time-frequency matrix. If a frequency hopping signal is detected, the corresponding frequency hopping parameters are estimated, and then an interference signal is generated and output according to the frequency hopping parameters.

[0008] Furthermore, when performing time-frequency analysis on the narrowband IQ complex data, specifically performing short-time Fourier transform on the narrowband IQ complex data to obtain corresponding time-frequency data, the value of the time-frequency data is used as the energy value of the corresponding frequency point on the time-frequency diagram.

[0009] Furthermore, when the time-frequency graph is binarized, the following steps are specifically included: Convert the energy value of the frequency point in the time-frequency graph into the corresponding grayscale value; Traverse the threshold interval, calculate the inter-class variance of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold, and select the threshold with the maximum inter-class variance as the optimal threshold; The frequency points in the time-frequency diagram are used as elements in the matrix to obtain the time-frequency matrix I ( n , k ) ,in n represents the time index of the elements in the matrix,k Represents the frequency index of the elements in the matrix, traversing the time-frequency matrix I ( n , k ), the frequency points whose grayscale values ​​are less than the optimal threshold are assigned a value of 0, and the frequency points whose grayscale values ​​are greater than the optimal threshold are assigned a value of 1 in the time-frequency diagram.

[0010] Furthermore, the calculation formula for the between-class variance of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold is as follows:

[0011] in, and are the proportions of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold in all the frequency points of the time-frequency graph, is the mean gray value of all frequency points in the time-frequency graph, and are the mean grayscale values ​​of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold, respectively. The calculation formula is as follows:

[0012]

[0013] Among them, p(i) is the proportion of the frequency point with gray value i in all the frequency points of the time-frequency graph, L is the threshold.

[0014] Furthermore, before using the double sliding window to detect the frequency hopping signal for each frequency point of the time-frequency matrix, an optional step is also included. The optional step specifically inserts an optional time-frequency matrix morphological processing step according to the hopping rate of the frequency hopping signal to improve the accuracy of frequency hopping signal detection. The time-frequency matrix morphological processing step specifically includes: Construct a rectangular element smaller than the specified size as a structural element and perform a closing operation on the time-frequency matrix to bridge the cracks and fill the holes. The formula for closing the time-frequency matrix is ​​as follows:

[0015] In the above formula, I(n,k) represents the time-frequency matrix; represents the closing operation, represents the dilation operation, represents the erosion operation, and b represents the structural element; Construct a horizontal linear structure element and perform an opening operation on the time-frequency matrix to eliminate the interference of frequency sweep and burst signals. The size of the linear structure element is larger than the horizontal size of the rectangular element and smaller than the horizontal size of each cluster of frequency hopping signals in the time-frequency matrix. The formula for the opening operation of the time-frequency matrix is ​​as follows:

[0016] In the above formula, I(n,k) represents the time-frequency matrix; represents the opening operation, represents the dilation operation, represents the erosion operation, and b represents the structural element.

[0017] Furthermore, when using double sliding windows to detect frequency hopping signals for each frequency point of the time-frequency matrix, specifically for each frequency point k of the time-frequency matrix I(n,k), the energy and W of the L time-frequency points after the frequency point k are calculated. k,1 , and the energy and W of the L time-frequency points in the window before frequency point k k,2 , and then calculate the energy and W of the front window L time-frequency points k,2 and the energy and W of the rear window L time-frequency points k,1 Energy difference If the energy difference If the value is greater than the frequency hopping detection threshold, the frequency hopping signal is detected at the frequency point k.

[0018] Furthermore, the energy and W of the L time-frequency points after the frequency point k are calculated. k,1 , and the energy and W of the L time-frequency points in the window before frequency point k k,2 When , the calculation formula is as follows:

[0019]

[0020] in, Represents the element at the i-th time point and the k-th frequency point in the time-frequency matrix.

[0021] Furthermore, when estimating the corresponding frequency hopping parameters, it specifically includes: taking the frequency point k where the frequency hopping signal is detected as the center, checking the value of each frequency point in the time-frequency matrix I(n,k) along the frequency dimension upward until a row with a maximum frequency k1 that is continuously "1" is found, and at the same time, checking the value of each frequency point in the time-frequency matrix I(n,k) along the frequency dimension downward until a row with a minimum frequency k2 that is continuously "1" is found, calculating the average value of the maximum frequency k1 and the minimum frequency k2 to obtain the center frequency of the frequency hopping signal, and calculating the difference between the maximum frequency k1 and the minimum frequency k2 to obtain the bandwidth of the frequency hopping signal.

[0022] Furthermore, when generating and outputting an interference signal according to the frequency hopping parameters, the process specifically includes: Interference baseband data is generated based on the bandwidth and interference type of the frequency hopping signal. The DDS frequency synthesizer is controlled according to the center frequency of the frequency hopping signal to generate two orthogonal carrier signals. The interference baseband data and the two carrier signals are digitally up-converted and then digital-to-analog converted to generate a radio frequency interference signal in the specified frequency band. Count the continuous frequency points of the frequency hopping signal detected along the time dimension to obtain the dwell time of the frequency hopping signal. Subtract the specified delay from the dwell time of the frequency hopping signal to obtain the duration of the interference signal. The transmission time of the radio frequency interference signal is controlled according to the duration of the interference signal.

[0023] The present invention also proposes a time-frequency Figure 2 The value-based frequency hopping signal tracking jammer includes: Data acquisition module, used to collect data stream of target signal in real time; A preprocessing module, configured to perform data preprocessing on the data stream according to an operating frequency band of a target signal to obtain narrowband IQ complex data; A time-frequency data acquisition module is used to perform time-frequency analysis on narrowband IQ complex data to obtain corresponding time-frequency graphs; A binarization processing module, used to perform binarization processing on the time-frequency graph to obtain a binarized time-frequency matrix; A frequency hopping detection module is used to detect the frequency hopping signal using a double sliding window for each frequency point in the time-frequency matrix; A frequency hopping parameter calculation module is used to estimate the corresponding frequency hopping parameters when a frequency hopping signal is detected; The interference signal generation module is used to generate an interference signal according to the frequency hopping parameters and output it.

[0024] Compared with the prior art, the advantages of the present invention are: The present invention performs binarization processing on the time-frequency graph of the target signal, converts the time-frequency graph into a binarized time-frequency matrix, and performs real-time detection and measurement of the frequency hopping signal based on the time-frequency matrix, which can speed up the processing speed of frequency hopping detection and significantly reduce the occupied processor resources. Compared with broadband blocking interference, frequency hopping tracking interference is a narrowband interference signal emitted according to the frequency hopping frequency point, and the required interference signal output power is greatly reduced. Since it is a real-time suppression interference for the frequency hopping frequency point, it has no effect on other communication equipment, greatly reducing the flexibility and scope of application of the equipment. Under the same interference power conditions, the frequency hopping signal tracking interference equipment implemented by the present invention can effectively improve the interference distance for frequency hopping radio stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the principle of frequency hopping signal tracking interference.

[0026] Figure 2Schematic diagram of the general frequency hopping signal tracking interference implementation structure.

[0027] Figure 3 Schematic diagram of the framework of the frequency hopping signal tracking interference method according to an embodiment of the present invention.

[0028] Figure 4 Schematic diagram of the grayscale image obtained by converting the time-frequency image.

[0029] Figure 5 Schematic diagram of the binary image corresponding to the time-frequency matrix.

[0030] Figure 6 Schematic diagram of the interference signal generation process.

[0031] Figure 7 Schematic diagram of the duration of the interference signal.

[0032] Figure 8 The figure is a schematic structural diagram of a frequency hopping signal tracking and jamming device according to an embodiment of the present invention.

[0033] Figure 9 Schematic diagram of the working process of the frequency hopping signal tracking and jamming device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0035] Before introducing the specific embodiments of the present invention, relevant concepts or terms are first explained.

[0036] DDS: Direct Digital Synthesis is a digital technology used to generate precise frequency signals. It controls the frequency, phase and amplitude of the signal by digital methods and is widely used in communications, radar, instrumentation and other fields. The core of DDS is a phase accumulator. It generates signals at a fixed clock frequency. f clk is used as the reference, and a phase increment Δ is accumulated each time ϕ The phase increment determines the frequency of the output signal. The accumulated phase value is converted to a corresponding amplitude value using a lookup table (usually a sine or cosine function). The resulting digital amplitude value is converted to an analog signal using a digital-to-analog converter (DAC), ultimately outputting the desired frequency signal.

[0037] STFT: Short-Time Fourier Transform, is a time-frequency analysis method used to analyze the characteristics of a signal at different times and frequencies. It segments the signal in the time domain and performs Fourier transform on each segment to obtain the time-frequency representation of the signal. x ( t ) is divided into multiple short time segments, each segment is multiplied by a window function w ( t ), then perform a Fourier transform on each short time segment to obtain the frequency spectrum of that segment. Finally, the frequency spectra of each segment are combined to form a time-frequency representation of the signal. This is a three-dimensional matrix, where two dimensions represent time and frequency, respectively, and the third dimension represents the complex amplitude of the signal at the corresponding time and frequency. The modulus of the complex number is usually used as the value of the time-frequency data.

[0038] Example 1 In order to solve the technical problems existing in the existing technology of frequency hopping signal tracking interference, this embodiment proposes a method based on time-frequency Figure 2 A frequency hopping signal tracking interference method with low resource consumption, high real-time performance and adaptability to complex electromagnetic environments. Figure 3 As shown, the method of this embodiment includes the following steps: The frequency hopping signal detection and reception phase includes the following steps: S101) collecting a data stream of a target signal in real time, performing data preprocessing on the data stream according to an operating frequency band of the target signal, and obtaining narrowband IQ complex data; S102) performing time-frequency analysis on the narrowband IQ complex data to obtain a corresponding time-frequency graph, and performing binarization processing on the time-frequency graph to obtain a binarized time-frequency matrix; S103) detecting a frequency hopping signal using a double sliding window for each frequency point in the time-frequency matrix, and estimating corresponding frequency hopping parameters if a frequency hopping signal is detected; The interference phase includes the following steps: S104) generating an interference signal according to the frequency hopping parameters and outputting the interference signal; S105) Jump to step S101 to realize the automatic cycle of the interference phase and the frequency hopping signal detection phase.

[0039] Through the above steps, the tracking and interference of the frequency hopping signal are realized. At the same time, since the frequency hopping signal is detected at each frequency point of the binary time-frequency matrix obtained by binarizing the time-frequency diagram, real-time detection and measurement of the frequency hopping signal are realized, which has high real-time performance and greatly reduces resource occupation.

[0040] The following is a detailed description of each step.

[0041] Step S101 of this embodiment specifically includes the following steps: Step S01. ADC data acquisition: Real-time data acquisition of the target signal is performed through the ADC to obtain a continuous data stream of the digitized target signal.

[0042] Step S02. Data preprocessing: Preprocess each data stream acquired by ADC data acquisition according to the operating frequency band of the target signal, mainly including digital down-conversion, decimation filtering and other processing to obtain preprocessed narrowband IQ complex data.

[0043] Step S102 of this embodiment specifically includes the following steps: Step S03. Time-frequency data processing: performing time-frequency analysis on the narrowband IQ complex data obtained by preprocessing to obtain the time-frequency data of each signal segment.

[0044] Frequency-hopping signals are typically non-stationary signals, and time-frequency analysis is currently the most effective means of processing them. Using this method, the distribution of frequency-hopping signals can be intuitively represented, enabling parameter estimation and other processing. The short-time Fourier transform (STFT) is a typical linear time-frequency transform. Therefore, in this embodiment, the time-frequency analysis of narrowband IQ complex data specifically includes: First, perform a short-time Fourier transform on the narrowband IQ complex data to obtain the corresponding time-frequency data. For ease of calculation, the discretization of STFT is as follows:

[0045] Where s(t) represents the signal to be processed and h(t) represents the window function.

[0046] For the signal and Composite signal (a and b are constants), which can be expressed as

[0047] Then, the value of the time-frequency data is used as the energy value of the corresponding frequency point on the time-frequency graph. The time-frequency data is a three-dimensional matrix that reflects the energy distribution of the signal at different times and frequencies. In this embodiment, the complex modulus of the STFT result is used as the value of the time-frequency data to assign the energy value of the corresponding frequency point on the time-frequency graph, and a time-frequency distribution graph of the signal can be obtained. The time-frequency graph usually uses time as the horizontal axis and frequency as the vertical axis, and uses the color or grayscale corresponding to the energy value to represent the energy size of the signal at the corresponding time and frequency. In this way, the time-frequency graph can intuitively display the distribution of the signal on the time-frequency plane.

[0048] After obtaining the time-frequency graph, the time-frequency graph is binarized, which includes: Step S04: Grayscale image conversion: transform each segment of data to obtain the grayscale data of each segment of data, that is, convert the energy value of the frequency point in the time-frequency graph into the corresponding grayscale value.

[0049] Image grayscale conversion is the process of converting a time-frequency image into a grayscale image. The corresponding grayscale value ranges from 0 to 255, allowing for the display of most of the target information required for time-frequency analysis of frequency-hopping signals using less data. Converting the signal's time-frequency distribution image to a grayscale image reduces memory usage, lowers computational complexity, and accelerates algorithm processing.

[0050] In order to facilitate the grayscale conversion of the time-frequency graph, in this embodiment, the energy values ​​of the frequency points in the time-frequency graph are converted to logarithmic representation through a logarithmic table and correspond to grayscale values ​​0 to 255. Finally, the different grayscale values ​​of the frequency points in the time-frequency graph obtained by STFT correspond to the energy values ​​of the time-frequency points, and the result is Figure 4 Grayscale image shown.

[0051] Step S05. Time-frequency Figure 2 The valuing process includes the following steps: Step S051: traverse the threshold interval, calculate the inter-class variance of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold, and select the threshold when the inter-class variance is the largest as the optimal threshold.

[0052] Grayscale Figure 2 The key step of binarization is to calculate the threshold value of binarization. First, calculate the grayscale mean of the image and select the threshold L∈[0,255]. Then the proportion of the frequency points with grayscale values ​​less than or equal to L in the grayscale image is , the mean gray value is ; The proportion of frequency points with grayscale values ​​greater than L is , the mean gray value is , the calculation formula is as follows:

[0053]

[0054] Among them, p(i) is the proportion of the frequency point with gray value i in all the frequency points of the time-frequency graph, L is the threshold.

[0055] Furthermore, the calculation formula for the between-class variance of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold is as follows:

[0056] in, and are the proportions of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold in all the frequency points of the time-frequency graph, is the mean gray value of all frequency points in the time-frequency graph, and are the mean grayscale values ​​of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold, respectively.

[0057] Take L∈[0,255], when When the maximum value is taken, the separation effect is the best, and the L value at this time is the optimal threshold.

[0058] Step S052: Use the frequency points in the time-frequency diagram as elements in the matrix to obtain the time-frequency matrix I ( n , k ) ,in n represents the time index of the elements in the matrix, k Represents the frequency index of the elements in the matrix, traversing the time-frequency matrix I ( n , k ), assign the frequency points with grayscale values ​​less than the optimal threshold value to 0, and assign the frequency points with grayscale values ​​greater than the optimal threshold value to 1 in the time-frequency graph to obtain the binary time-frequency matrix I ( n , k ). The formula is as follows:

[0059] Through the above steps, the grayscale image is binarized to obtain a binary time-frequency matrix I (n, k), which can effectively reduce the resource occupation of subsequent frequency hopping detection. The binary image corresponding to the binary time-frequency matrix I (n, k) is as follows: Figure 5 shown.

[0060] Step S103 of this embodiment specifically includes the following steps: Step S06. Frequency hopping signal detection: Based on the binary time-frequency matrix I(n,k), perform real-time frequency hopping signal detection on the input target signal data. This includes the following steps: Step S061. Morphological processing of the time-frequency matrix: The time-frequency matrix morphological processing is an optional step. Specifically, according to the hopping rate of the frequency hopping signal, the optional time-frequency matrix morphological processing step is inserted at the beginning of step S103 to improve the accuracy of frequency hopping signal detection.

[0061] After binarization, the time-frequency matrix I(n,k) still contains sweep signals, burst signals, and unclear noise points, which appear as isolated points or lines connected to frequency-hopping signals on the image. Morphological filtering can be used to further remove interference and extract useful signals.

[0062] The main operations of morphological filtering include erosion, dilation, opening and closing operations, which eliminate isolated points in the image and fill holes by setting structural elements. The opening operation is an erosion operation followed by a dilation operation, which can be defined as:

[0063] Where I(n,k) represents the time-frequency matrix of the image to be processed; represents the opening operation, represents the dilation operation, represents the erosion operation, and b represents the structural element.

[0064] The closing operation is the expansion operation followed by the erosion operation, which is defined as

[0065] Where, Represents a closing operation.

[0066] The structural element plays an important role in the calculation process. The image to be retained must be larger than the structural element, and the image to be eliminated must be smaller than the structural element. The structural element is designed based on the signal bandwidth and duration of the frequency hopping signal. The morphological processing flow is as follows: Construct a rectangular element smaller than the specified size as a structural element and perform a closing operation on the time-frequency matrix to bridge the gaps and fill the holes; A horizontal linear structuring element is constructed and an opening operation is performed on the time-frequency matrix to eliminate the interference of frequency sweeping and burst signals. The size of the linear structuring element can be appropriately enlarged and should be larger than the horizontal size of the rectangular element and smaller than the horizontal size of each cluster of frequency hopping signals in the time-frequency matrix I(n,k). This can effectively retain the frequency hopping signal and remove isolated noise points and frequency sweeping interference.

[0067] Step S062: Use a double sliding window to detect the frequency hopping signal for each frequency point of the time-frequency matrix: Based on the time-frequency matrix I(n,k) after morphological processing, double sliding window detection is performed on each frequency domain component of the time-frequency matrix. This is a burst signal detection algorithm in the frequency domain. It has the characteristics of small computational complexity and high speed, and can achieve rapid detection of burst signals with relatively small resource overhead.

[0068] The dual sliding window detection algorithm uses two adjacent windows W1 and W2 of equal length, which slide point by point. For each frequency point k in the time-frequency matrix I(n,k), sliding windows W1 and W2 are defined, each with a length of L. When using dual sliding windows to detect frequency-hopping signals for each frequency point in the time-frequency matrix, the following steps are specifically performed: For each frequency point k in the time-frequency matrix I(n,k), calculate the energy and W of the L time-frequency points after the frequency point k. k,1, and the energy and W of the L time-frequency points in the window before frequency point k k,2 , the calculation formula is as follows:

[0069]

[0070] in, Represents the element at the i-th time point and the k-th frequency point in the time-frequency matrix; Then calculate the energy and W of the front window L time-frequency points k,2 and the energy and W of the rear window L time-frequency points k,1 Energy difference , which can be expressed as

[0071] If the energy difference If the value is greater than the frequency hopping detection threshold, the frequency hopping signal is detected at the frequency point k. The peak value reflects the time when the frequency hopping signal is disconnected. The judgment is determined by the threshold of frequency hopping burst detection. Generally, Threshold = L-1 can be set.

[0072] It should be noted that, in order to realize the burst detection of full-band signals, in this embodiment, N channels of parallel real-time monitoring are performed on each frequency point k, where N is the time-frequency matrix I ( n , k ). Since I(n,k) is a binary matrix, double sliding window energy detection in the frequency domain can significantly reduce the resource overhead.

[0073] Step S07. Frequency hopping parameter estimation: After detecting the frequency hopping signal, quickly measure the center frequency and signal bandwidth of the frequency hopping signal. Specifically including: Taking the frequency point k where the frequency hopping signal is detected as the center, check the value of each frequency point in the time-frequency matrix I(n,k) along the frequency dimension upward until a row with continuous "1" of the maximum frequency k1 is found. At the same time, check the value of each frequency point in the time-frequency matrix I(n,k) along the frequency dimension downward until a row with continuous "1" of the minimum frequency k2 is found. Calculate the average value of the maximum frequency k1 and the minimum frequency k2 to obtain the center frequency of the frequency hopping signal, and calculate the difference between the maximum frequency k1 and the minimum frequency k2 to obtain the bandwidth of the frequency hopping signal.

[0074] The time-frequency analysis of the signal establishes the relationship between the binary time-frequency matrix I(n,k) and the signal parameters. When the frequency hopping signal is detected at frequency point k, the frequency point k is taken as the center and the continuous "1" pixel points are searched upward and downward along the frequency dimension. The maximum and minimum rows are recorded as k1 and k2 respectively, and the average value is taken as the center frequency k of the frequency hopping signal, that is,

[0075] The bandwidth m of the frequency hopping signal is the difference between the maximum and minimum rows, that is,

[0076] For example, the frequency index k =10 to k =15 is "1" continuously, that is, I ( n ,10)= I ( n ,11)= I ( n ,12)= I ( n ,13)= I ( n ,14)= I ( n ,15)=1, and k =9 and k =16, I ( n ,9)= I ( n ,16)=0. Then the maximum row of pixels with consecutive "1" values ​​is k 1 is 15, the smallest row k 2 is 10. Therefore, the center frequency of the frequency hopping signal k It can be calculated as: (15+10) / 2=12.5. The frequency hopping signal bandwidth m is: 15-10=5.

[0077] Assume that after the time-frequency analysis in step S102, the signal is graphically represented as a time-frequency spectrum with a size of L × H, where the length corresponds to the duration T of the signal and the width represents the highest frequency F of the spectrum. s / 2, then the frequency f of the detected signal c , signal bandwidth B w The relationship between it and the time-frequency matrix I(n,k) is:

[0078]

[0079] Step S104 of this embodiment specifically includes the following steps: Step S08. Interference signal guidance and generation: like Figure 6 As shown, first, according to the bandwidth B of the frequency hopping signal w The baseband data is converted to the sampling rate of the DAC output through sampling rate interpolation and anti-aliasing low-pass filtering.

[0080] Then, the DDS frequency synthesizer is controlled according to the center frequency of the frequency hopping signal to generate two orthogonal carrier signals. 、 , the interference baseband data and the two carrier signals are digitally up-converted and then sent to the DAC for digital-to-analog conversion to generate the RF interference signal of the specified frequency band, thereby passing the center frequency f of the frequency hopping signal. c and bandwidth B w , control the generation of interference signal and realize the overlap of interference signal and frequency hopping signal in the frequency domain.

[0081] Step S09. Interference signal output: Detect the continuous frequency points of the frequency hopping signal along the time dimension and obtain the residence time of the frequency hopping signal. Subtract the specified delay from the residence time of the frequency hopping signal to obtain the duration of the interference signal. The duration of the interference signal is as follows: Figure 7 As shown, the expression is as follows:

[0082] Among them, T h is the dwell time of the frequency hopping signal, specifically the time difference between the start frequency point and the end frequency point in the continuous frequency points of the frequency hopping signal. p is the detection delay of the frequency hopping signal, specifically the time taken to execute step S101 to step S103, T sw It is the switching time required to switch from the frequency hopping signal detection phase to the interference phase; After the duration of the interference signal is obtained, the transmission time of the radio frequency interference signal is controlled according to the duration of the interference signal to achieve the time domain overlap of the frequency hopping tracking interference.

[0083] Example 2 This embodiment proposes a time-frequency Figure 2 The valued frequency hopping signal tracking jammer, such as Figure 8 Shown, including: The RF transceiver antenna module acts as a receiving antenna to receive electromagnetic signals from the electromagnetic space and convert them into electrical signals for output; and acts as a transmitting antenna to radiate the input interference electrical signals through the electromagnetic space; A transceiver switching module is connected to the RF transceiver antenna module, the RF signal receiving module, and the RF signal power amplification module, and is used to switch the connection relationship between the RF transceiver antenna module and the RF signal receiving module and the RF signal power amplification module between reconnaissance mode and interference mode; A radio frequency signal receiving module, connected to the transceiver switching module, is used to down-convert the broadband radio frequency signal received by the receiving antenna to a fixed intermediate frequency signal, filter out out-of-band signals, and adjust the signal amplitude to a reasonable range; The signal acquisition and processing board is connected to the RF signal receiving module and is used for data acquisition, signal preprocessing, frequency hopping signal detection and parameter measurement, interference signal generation, and other processing of the intermediate frequency signal. The functional modules of the signal acquisition and processing board include: A data acquisition module is connected to the radio frequency signal receiving module and is used to collect the data stream of the target signal in real time, specifically to collect data of the intermediate frequency signal, and collect a segment of data each time to obtain the current segment of data; A preprocessing module, connected to the data acquisition module, is used to perform data preprocessing such as sampling rate conversion on the data stream of the current segment according to the operating frequency band of the target signal and filtering out out-of-band interference to obtain narrowband IQ complex data; A time-frequency data acquisition module, connected to the preprocessing module, is used to perform time-frequency analysis on the preprocessed narrowband IQ complex data to obtain a time-frequency graph corresponding to the current segment data; A binarization processing module, connected to the time-frequency data acquisition module, for performing binarization processing on the time-frequency graph and converting the time-frequency data into a binarized time-frequency matrix; A frequency hopping detection module is connected to the binarization processing module and is used to detect the frequency hopping signal using a double sliding window for each frequency point of the time-frequency matrix to achieve real-time frequency hopping signal detection and quickly provide the frequency hopping signal detection result; A frequency hopping parameter calculation module is connected to the frequency hopping detection module and is used to estimate the frequency hopping parameters of the corresponding carrier frequency when a frequency hopping signal is detected, so as to realize rapid calculation and output of the frequency hopping parameters; An interference signal generation module is connected to the frequency hopping parameter calculation module and is used to generate a frequency hopping tracking interference signal according to guidance information such as the carrier frequency measured by the frequency hopping parameters, and convert it into a radio frequency signal for output; A radio frequency signal power amplification module, connected to the interference signal generation module, for amplifying the power of the frequency hopping tracking interference signal; The control terminal is connected to the signal acquisition and processing board and is used for human-computer interaction and parameter control of the frequency hopping tracking jamming device.

[0084] like Figure 9 As shown, during the frequency hopping signal tracking interference period, the working process of the device of this embodiment is as follows: After starting the frequency hopping tracking jamming task, first switch to the frequency hopping signal detection mode through the control terminal; The data acquisition module collects data on the signal of the specified interference frequency band to obtain a continuous current frequency band data; The preprocessing module performs preprocessing, digital down-conversion, and decimation filtering on the signal of the current frequency band; The pre-processed data is transformed into a time-frequency image by a time-frequency data acquisition module to obtain a time-frequency image, and the time-frequency image is converted into a grayscale image; The grayscale image is binarized through the binarization processing module, and the signal exceeding the threshold is converted to "1" and the signal below the threshold is converted to "0"; Through the frequency hopping detection module, morphological processing is first performed on the converted binary image to remove noise and interference signals; then, the frequency band covered by the frequency hopping signal is selected in the frequency domain, and dual-window energy detection of the frequency hopping signal is performed on each frequency point. The out-and-out of frequency hopping is detected based on the dual-window peak value. Each frequency point is binarized according to the spectrum energy intensity, so the parallel dual-window energy detection at this frequency point can significantly reduce the occupied resources. For the persistent fixed-frequency signal, the dual-window energy detection can remove the interference of the fixed-frequency signal on the frequency hopping signal detection; The frequency hopping parameter calculation module calculates the center frequency of the frequency hopping signal according to the detection result of the burst signal; By controlling the terminal to switch to interference mode, the RF link switches to the transmit channel, and the interference signal is radiated through the transceiver antennas. The interference signal generation module generates an interference signal according to the frequency hopping signal detection parameters, and determines the transmission duration of the interference signal according to the frequency hopping signal period; After the jamming signal transmission time slot is completed, the control terminal switches to the frequency hopping signal detection mode to re-receive and detect the frequency hopping signal. The RF transmission link switches to the RF receiving link, and the transceiver antenna receives the electromagnetic space radiation signal and enters the RF receiving link.

[0085] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for tracking interference of frequency hopping signals based on binarization of time-frequency graph, characterized in that: The following steps are involved: Collecting a data stream of a target signal in real time, performing data preprocessing on the data stream according to an operating frequency band of the target signal, and obtaining narrowband IQ complex data; Performing time-frequency analysis on the narrowband IQ complex data to obtain a corresponding time-frequency graph, and performing binarization processing on the time-frequency graph to obtain a binarized time-frequency matrix; A double sliding window is used to detect the frequency hopping signal for each frequency point of the time-frequency matrix. If a frequency hopping signal is detected, the corresponding frequency hopping parameters are estimated, and then an interference signal is generated and output according to the frequency hopping parameters.

2. The method for tracking interference of frequency hopping signals based on binarization of time-frequency graph according to claim 1, characterized in that: When performing time-frequency analysis on narrowband IQ complex data, specifically performing short-time Fourier transform on the narrowband IQ complex data to obtain corresponding time-frequency data, and using the value of the time-frequency data as the energy value of the corresponding frequency point on the time-frequency diagram.

3. The method for tracking interference of frequency hopping signals based on binarization of time-frequency graph according to claim 1, characterized in that: The binarization process of the time-frequency graph specifically includes: Convert the energy value of the frequency point in the time-frequency graph into the corresponding grayscale value; Traverse the threshold interval, calculate the inter-class variance of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold, and select the threshold with the maximum inter-class variance as the optimal threshold; The frequency points in the time-frequency diagram are used as elements in the matrix to obtain the time-frequency matrix I ( n , k ) ,in n represents the time index of the elements in the matrix, k Represents the frequency index of the elements in the matrix, traversing the time-frequency matrix I ( n , k ), the frequency points whose grayscale values ​​are less than the optimal threshold are assigned a value of 0, and the frequency points whose grayscale values ​​are greater than the optimal threshold are assigned a value of 1 in the time-frequency diagram.

4. The method for tracking interference of frequency hopping signals based on binarization of time-frequency graph according to claim 3, characterized in that: The calculation formula for the between-class variance of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold is as follows: in, and are the proportions of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold in all the frequency points of the time-frequency graph, is the mean gray value of all frequency points in the time-frequency graph, and are the mean grayscale values ​​of the frequency points whose grayscale values ​​are less than the threshold and the frequency points whose grayscale values ​​are greater than the threshold, respectively. The calculation formula is as follows: Among them, p(i) is the proportion of the frequency point with gray value i in all the frequency points of the time-frequency graph, L is the threshold.

5. The method for tracking interference of frequency hopping signals based on binarization of time-frequency graph according to claim 1, characterized in that: Before using the double sliding window to detect the frequency hopping signal for each frequency point of the time-frequency matrix, an optional step is also included. The optional step specifically inserts an optional time-frequency matrix morphological processing step according to the hopping rate of the frequency hopping signal to improve the accuracy of frequency hopping signal detection. The time-frequency matrix morphological processing step specifically includes: Construct a rectangular element smaller than the specified size as a structural element and perform a closing operation on the time-frequency matrix to bridge the cracks and fill the holes. The formula for closing the time-frequency matrix is ​​as follows: In the above formula, I(n,k) represents the time-frequency matrix; represents the closing operation, represents the dilation operation, represents the erosion operation, and b represents the structural element; Construct a horizontal linear structure element and perform an opening operation on the time-frequency matrix to eliminate the interference of frequency sweep and burst signals. The size of the linear structure element is larger than the horizontal size of the rectangular element and smaller than the horizontal size of each cluster of frequency hopping signals in the time-frequency matrix. The formula for the opening operation of the time-frequency matrix is ​​as follows: In the above formula, I(n,k) represents the time-frequency matrix; represents the opening operation, represents the dilation operation, represents the erosion operation, and b represents the structural element.

6. The method for tracking interference of frequency hopping signals based on binarization of time-frequency graph according to claim 1, characterized in that: When using double sliding windows to detect frequency hopping signals for each frequency point of the time-frequency matrix, specifically for each frequency point k of the time-frequency matrix I(n,k), the energy and W of the L time-frequency points after the frequency point k are calculated. k,1 , and the energy and W of the L time-frequency points in the window before frequency point k k,2 , and then calculate the energy and W of the front window L time-frequency points k,2 and the energy and W of the rear window L time-frequency points k,1 Energy difference If the energy difference If the value is greater than the frequency hopping detection threshold, the frequency hopping signal is detected at the frequency point k.

7. The method for tracking interference of frequency hopping signals based on binarization of time-frequency graph according to claim 6, characterized in that: Calculate the energy and W of the L time-frequency points after the frequency point k k,1 , and the energy and W of the L time-frequency points in the window before frequency point k k,2 When , the calculation formula is as follows: in, Represents the element at the i-th time point and the k-th frequency point in the time-frequency matrix.

8. The method for tracking interference of frequency hopping signals based on binarization of time-frequency graph according to claim 6, characterized in that: Estimating the corresponding frequency hopping parameters specifically includes: taking the frequency point k where the frequency hopping signal is detected as the center, checking the value of each frequency point in the time-frequency matrix I(n,k) upward along the frequency dimension until a row with a maximum frequency k1 containing consecutive "1s" is found. At the same time, checking the value of each frequency point in the time-frequency matrix I(n,k) downward along the frequency dimension until a row with a minimum frequency k2 containing consecutive "1s" is found. Calculating the average of the maximum frequency k1 and the minimum frequency k2 to obtain the center frequency of the frequency hopping signal, and calculating the difference between the maximum frequency k1 and the minimum frequency k2 to obtain the bandwidth of the frequency hopping signal.

9. The method for tracking interference of frequency hopping signals based on binarization of time-frequency graph according to claim 8, characterized in that: When an interference signal is generated and output according to the frequency hopping parameters, it specifically includes: Interference baseband data is generated based on the bandwidth and interference type of the frequency hopping signal. The DDS frequency synthesizer is controlled according to the center frequency of the frequency hopping signal to generate two orthogonal carrier signals. The interference baseband data and the two carrier signals are digitally up-converted and then digital-to-analog converted to generate a radio frequency interference signal in the specified frequency band. Count the continuous frequency points of the frequency hopping signal detected along the time dimension to obtain the dwell time of the frequency hopping signal. Subtract the specified delay from the dwell time of the frequency hopping signal to obtain the duration of the interference signal. The transmission time of the radio frequency interference signal is controlled according to the duration of the interference signal.

10. A frequency hopping signal tracking interference device based on time-frequency graph binarization, characterized in that: include: Data acquisition module, used to collect data stream of target signal in real time; A preprocessing module, configured to perform data preprocessing on the data stream according to an operating frequency band of a target signal to obtain narrowband IQ complex data; A time-frequency data acquisition module is used to perform time-frequency analysis on narrowband IQ complex data to obtain corresponding time-frequency graphs; A binarization processing module, used to perform binarization processing on the time-frequency graph to obtain a binarized time-frequency matrix; A frequency hopping detection module is used to detect the frequency hopping signal using a double sliding window for each frequency point in the time-frequency matrix; A frequency hopping parameter calculation module is used to estimate the corresponding frequency hopping parameters when a frequency hopping signal is detected; The interference signal generation module is used to generate an interference signal according to the frequency hopping parameters and output it.

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