Time domain orthogonal frequency coding waveform design and interference suppression method, device and medium

Abstract

The present invention discloses a time-domain orthogonal frequency coding waveform design and interference suppression method, device and medium, and relates to the field of radar signal processing technology. The method of the present invention comprises: constructing a time-domain correlation function of interference and target based on a radar echo signal model, and then solving it to obtain an optimized intra-pulse frequency coding sequence; based on the intra-pulse frequency coding waveform, for the echo signal, different time-frequency signals are intercepted through a time-frequency domain window to obtain a new time-frequency domain matrix, and the time-frequency domain matrix is ​​inversely transformed to realize target recognition and interference suppression based on time-domain correlation. The present invention aims at the common technical problem in the field of radar anti-interference, which is anti-intermittent sampling forwarding interference. First, a frequency coding waveform is designed, and optimized through a genetic algorithm to reduce the time-domain correlation between the target and the intermittent sampling interference; then, based on the echo signal obtained from the waveform, a time-frequency domain window function is used to realize target recognition and suppression of intermittent sampling forwarding interference.

Description

Technical Field

[0001] The present invention relates to the field of radar signal processing technology, and in particular to a time-domain orthogonal frequency coding waveform design and interference suppression method, device and medium. Background Art

[0002] With the continuous development of electronic countermeasure technology, the electromagnetic countermeasure environment faced by modern radar systems is becoming increasingly complex and changeable. Based on the application of new digital RF memory, jammers can generate a variety of new interference patterns, which seriously affect the detection performance of radar. Intermittent sampling and forwarding interference is a new type of active interference, which can quickly sample radar signals in a single pulse and generate interference signals that are strongly correlated with the target. When the radar performs pulse compression processing on the target echo mixed with strongly correlated interference, it will also produce pulse compression processing gain for the interference, thereby achieving the purpose of deceiving radar detection and suppressing target signals.

[0003] Therefore, it is an urgent problem to be solved in the art to provide a waveform design and interference suppression method that reduces the correlation between target signals and interference signals, improves time domain orthogonality, and extracts undisturbed segments in echoes to achieve interference suppression. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a time-domain orthogonal frequency coding waveform design and interference suppression method, device and medium.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A first aspect of the present invention provides a time domain orthogonal frequency coded waveform design and interference suppression method, comprising the following steps:

[0007] Based on the radar echo signal model, the time domain correlation function of the interference and the target is constructed, and the constructed time domain correlation function is solved to obtain the optimized intra-pulse frequency coding waveform;

[0008] The intra-pulse frequency coded waveform is transmitted as a radar transmitting waveform, and a corresponding echo signal is obtained; for the echo signal, different time-frequency signals are intercepted through a time-frequency domain window to obtain a new time-frequency domain matrix, and the time-frequency domain matrix is ​​inversely transformed to achieve target recognition and interference suppression based on time domain correlation.

[0009] Furthermore, the radar echo signal model includes:

[0010] Assume that there is a target and a forwarding jammer in the radar's observation scene. The jammer's interference type is intermittent sampling direct forwarding interference. The signal received by the radar includes the target echo signal, the interference signal and noise. Based on the scene prior information, a radar echo signal model is constructed.

[0011] If there are targets and interference signals in the radar detection scene, the echo signal received by the radar can be expressed as:

[0012]

[0013] The target signal in the echo is ; represents noise; the interference signal in the echo is ;

[0014] When there is only one target in the radar detection environment, the interference type is intermittent sampling direct forwarding interference, and the jammer duty cycle is 50%; For example, the interference and target echo signals received by the radar That is, the radar echo signal model is expressed as:

[0015]

[0016] In the formula, represents the scattering coefficient of the target; The first pulse echo The target signal of the sub-pulse is expressed as , For the The first pulse echo The interference signal of the echo sub-pulse; is a rectangular pulse function, represents the sub-pulse width, is the frequency modulation slope of the sub-pulse, is the carrier frequency, Indicates the target delay of the echo; the frequency hopping interval is after digital down-conversion. The center frequency of the sub-pulse is expressed as in, It is a pulse coding method. is the frequency modulation bandwidth of a sub-pulse, and N is the total number of sub-pulses in a transmitted pulse.

[0017] Furthermore, the time domain correlation function of the interference and the target is constructed by a radar echo signal model, including:

[0018] No. The time domain correlation function of the target and interference of the interfered sub-pulse is:

[0019]

[0020] in, represents the prior information of interference, For the echo The target signal of sub-pulses is encoded as follows: , Indicates the echo The interference signal mixed in the sub-pulse, represents the delay of the interference signal in the nth sub-pulse;

[0021] When the total number of sub-pulses in a transmitted pulse is , under the condition that the frequency coding sequence satisfies the requirement that there are no repeated elements in the sequence, the sequence has The elements of the encoding sequence belong to the set , the objective function of the time domain correlation function of the interference and the target when solving is expressed as:

[0022] .

[0023] Furthermore, a genetic algorithm can be used to solve the constructed time domain correlation function and optimize the intra-pulse frequency coded waveform sequence, that is, the constructed time domain correlation function is used as a calculation method for the fitness in the genetic algorithm solution process, and the convergence condition of the solution can be set as the objective function during the solution ( ) value converges or reaches the specified maximum number of iterations.

[0024] Further, the intra-pulse frequency coded waveform is transmitted as a radar transmission waveform, and a corresponding echo signal is obtained; for the echo signal, different time-frequency signals are intercepted through a time-frequency domain window to obtain a new time-frequency domain matrix, and the time-frequency domain matrix is ​​inversely transformed, including:

[0025] For The echo signal is digitally down-converted to obtain a baseband echo signal; based on the interference prior information, the echo signal segment affected by interference is extracted from the echo signal;

[0026] The extracted signal is segmented with a sub-pulse width as a segment length. The total width of the interference sub-pulse extracted by the radar is , the sub-pulse width is , then a total of slice fragments, represents rounding down; where the interfered sub-pulse The time domain signal function of each segment is expressed as:

[0027]

[0028] In the formula, Indicates the target echo signal fragments, For noise, To interfere; Indicates The target time domain envelope in the clips, For the The first The interference time domain envelope; Delay for the target, Indicates The carrier frequency of each fragment, Indicates Fragment The interfering carrier frequency;

[0029] The total is The interference signal data matrix composed of all slice fragments is expressed as:

[0030]

[0031] Perform short-time Fourier transform on each interference segment and process the interference and target echo signals in the frequency domain. The time-frequency matrix of each segment is expressed as:

[0032]

[0033] in, is the center of the window function, Refers to short-time Fourier transform, is the window function of the sliding window in the time-frequency domain, t is the time integral, and e is the natural base;

[0034] Use the time-frequency window function to perform sliding window interception on the time-frequency matrix of each signal segment to obtain a new time-frequency domain matrix ;

[0035]

[0036]

[0037] Among them, the time-frequency domain sliding window length is , the sliding window step length is , Represents the Hadamard product. Indicates A window function, ~ Behavior , , ; The total number of window functions in the entire interfered sub-pulse signal is , ;

[0038] Perform inverse short-time Fourier transform on the intercepted result to obtain the time domain signal :

[0039] ;

[0040] in, Refers to Inverse Short-Time Fourier Transform.

[0041] Furthermore, the target recognition and interference suppression based on time domain correlation includes:

[0042] Calculate the correlation between the new time domain signal and the pulse pressure reference signal: recalculate Time domain correlation with the reference signal used for pulse compression in radar, The window function intercepts the total A new time-frequency matrix, vector After the corresponding time-frequency domain sliding window is intercepted The correlation value of the interference and target mixed signal and the pulse compression reference signal represented by the time-frequency matrix; the time domain signal corresponding to each time-frequency matrix With pulse pressure reference signal The correlation function is given by:

[0043]

[0044] Maximum value in a vector The corresponding time-frequency data matrix That is, the time-frequency matrix of the target signal, the time domain signal after inverse short-time Fourier transform The target signal in the sub-pulse is retained and extracted The corresponding signal part is suppressed except The rest of the corresponding signal;

[0045] The sub-pulse segments after interference suppression and the sub-pulse segments without interference are superimposed to obtain the target echo signal without intermittent forwarding interference.

[0046] According to a second aspect of the present invention, there is provided an electronic device comprising a memory and a processor, wherein the memory stores computer instructions executable on the processor, and the processor executes the steps of the method according to the first aspect when executing the computer instructions.

[0047] According to a third aspect of the present invention, there is provided a computer storage medium having computer instructions stored thereon, which, when executed, execute the steps of the method according to the first aspect.

[0048] The technical solution provided by the present invention brings at least the following beneficial effects:

[0049] In an exemplary embodiment of the present invention, in order to address the common technical problem of anti-intermittent sampling forwarding interference in the field of radar anti-interference, a frequency coded waveform is first designed and optimized through a genetic algorithm to obtain an optimized intra-pulse frequency coded transmission waveform with lower time domain correlation, so as to reduce the time domain correlation between the target and the intermittent sampling interference; then, based on the echo signal obtained from the waveform, a time-frequency domain window function is used to realize target recognition and suppression of intermittent sampling forwarding interference, and by calculating the correlation between the time domain signal and the reference signal, the signal is screened and intermittent sampling forwarding interference suppression is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0051] Figure 1 A flow chart of a time-domain orthogonal frequency coded waveform design and interference suppression method provided in an exemplary embodiment of the present invention;

[0052] Figure 2 A schematic diagram of the time-frequency of a radar baseband echo signal using an intra-pulse frequency coded waveform provided in an exemplary embodiment of the present invention;

[0053] Figure 3 It is a time-frequency diagram of an echo signal before optimizing the intra-pulse frequency coding waveform in a simulation experiment provided in an exemplary embodiment of the present invention;

[0054] Figure 4 It is a time-frequency diagram of an echo signal after optimizing the intra-pulse frequency coding waveform in a simulation experiment provided in an exemplary embodiment of the present invention;

[0055] Figure 5 It is a schematic diagram of a convergence curve of the number of iterations of a genetic algorithm and the correlation between interference and target in an echo waveform in a simulation experiment provided in an exemplary embodiment of the present invention;

[0056] Figure 6 A time-frequency diagram after suppressing intermittent sampling forwarding interference in a simulation experiment provided in an exemplary embodiment of the present invention;

[0057] Figure 7 A comparison diagram of pulse compression results before and after optimization of the intra-pulse frequency coding waveform in a simulation experiment provided in an exemplary embodiment of the present invention;

[0058] Figure 8 A schematic structural diagram of an electronic device provided in an exemplary embodiment of the present invention;

[0059] Fig. 9 A schematic diagram of the structure of a computer storage medium provided in an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] In the description of the present invention, it should be noted that the directions or positional relationships indicated by "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are directions or positional relationships based on the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0062] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0063] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0064] See also Figure 1 , Figure 1 A time-domain orthogonal frequency coding waveform design and interference suppression method provided in an exemplary embodiment is a pulse frequency coding waveform design and interference suppression method based on time-domain orthogonality, which comprises the following steps:

[0065] Based on the radar echo signal model, a time domain correlation function of interference and target is constructed, and the constructed time domain correlation function is solved to obtain an optimized intra-pulse frequency coded waveform; preferably, in this example, a genetic algorithm is used to solve the constructed time domain correlation function.

[0066] The intra-pulse frequency coded waveform is transmitted as a radar transmitting waveform, and a corresponding echo signal is obtained; for the echo signal, different time-frequency signals are intercepted through a time-frequency domain window to obtain a new time-frequency domain matrix, and the time-frequency domain matrix is ​​inversely transformed to achieve target recognition and interference suppression based on time domain correlation.

[0067] Specifically, in this exemplary embodiment, in order to address the common technical problem of anti-intermittent sampling forwarding interference in the field of radar anti-interference, a frequency coded waveform is first designed and optimized through a genetic algorithm to obtain an optimized intra-pulse frequency coded transmission waveform with lower time domain correlation, so as to reduce the time domain correlation between the target and the intermittent sampling interference; then, based on the echo signal obtained from the waveform, the time-frequency domain window function is used to realize target recognition and suppression of intermittent sampling forwarding interference, and by calculating the correlation between the time domain signal and the reference signal, the signal is screened and intermittent sampling forwarding interference suppression is realized.

[0068] It should be noted that the optimized waveform in the previous step improves the separability of intermittent sampling forwarding interference and the target. In the next step, based on the optimized waveform, the time-frequency window function is constructed using the time-frequency analysis tool, and the time domain correlation is further combined to achieve target recognition and intermittent sampling forwarding interference suppression. If the previous step is used alone, interference countermeasures cannot be achieved; if the latter step is used alone, the interference countermeasure effect is poor. The combination of the two is more conducive to intermittent sampling forwarding interference countermeasures, and a better suppression effect can be obtained.

[0069] Therefore, it can be seen that this exemplary embodiment uses an intra-pulse frequency coded waveform, which has a stronger anti-interference ability than the traditional linear frequency modulation pulse waveform; the present invention is based on the optimized intra-pulse frequency coded waveform, with less signal loss after pulse compression and less residual interference, and is an effective intermittent sampling forwarding interference processing method; finally, a time-frequency domain sliding window algorithm is used to extract the undisturbed segments in the echo to achieve interference suppression.

[0070] It should be noted that the intra-pulse frequency coded waveform refers to the radar's transmitting waveform. The optimized intra-pulse frequency coded waveform in this exemplary embodiment is used as the radar transmitting waveform, and in the interference scenario described later, an echo signal of the optimized waveform is obtained; the echo signal contains the target, interference and noise, and the waveform of the target signal is the intra-pulse frequency coded waveform, which has a time delay difference compared to the transmitted intra-pulse frequency coded waveform.

[0071] The following content will elaborate on the specific implementation methods of the above steps:

[0072] The previous step may specifically include the following three steps:

[0073] (1) Assume that there is a target and a forwarding jammer in the radar observation scene. The jammer’s interference type is intermittent sampling direct forwarding interference. Then the signal received by the radar includes the target echo signal, the interference signal and noise. Based on the scene prior information, a radar echo signal model is constructed.

[0074] (2) Based on the radar echo signal model, the time domain correlation function of the interference and the target is obtained;

[0075] (3) Solving the objective function through genetic algorithm, obtaining the optimized frequency coding sequence, and then obtaining the optimized intra-pulse frequency coding waveform.

[0076] More preferably, in an exemplary embodiment, the radar echo signal model includes:

[0077] Assume that there is a target and a forwarding jammer in the radar's observation scene. The jammer's interference type is intermittent sampling direct forwarding interference. The signal received by the radar includes the target echo signal, the interference signal and noise. Based on the scene prior information, a radar echo signal model is constructed.

[0078] If there are targets and interference signals in the radar detection scene, the echo signal received by the radar can be expressed as:

[0079]

[0080] The target signal in the echo is ; represents noise; the interference signal in the echo is ;

[0081] When there is only a single intermittent sampling direct forwarding interference in the detection scenario, the sub-pulse width of the frequency-coded waveform is set to be consistent with the interference sampling duration based on the interference prior information. At this time, the jammer intercepts the current sub-pulse and samples it, and then forwards the interference signal generated based on the current sub-pulse. Due to the frequency jump between adjacent sub-pulses in the radar transmission signal, although the interference and the target overlap in the time domain in the echo of the next sub-pulse, there is a frequency difference in the frequency domain. By processing the echo signal in the frequency domain, the interference and the target are separated and the interference is suppressed.

[0082] A time-frequency diagram of a radar baseband echo signal using an intra-pulse frequency coded waveform is shown in Figure 2 As shown in the figure, it can be seen that the use of this waveform can increase the separability of the target and the interference, which is beneficial for the radar to suppress the interference of the echo signal.

[0083] Depend on Figure 2It can be seen that due to the difference in the transmission and reception of intermittent sampling direct forwarding interference, the center frequency of the interference signal generated by the jammer for the previous sub-pulse sampling is different from the center frequency of the target signal obtained by the current sub-pulse. Therefore, the distinction between interference and target can be increased by optimizing the coding sequence to facilitate subsequent interference identification and suppression.

[0084] When there is only one target in the radar detection environment, the interference type is intermittent sampling direct forwarding interference, and the jammer duty cycle is 50%; For example, the interference and target echo signals received by the radar That is, the radar echo signal model is expressed as:

[0085]

[0086] In the formula, represents the scattering coefficient of the target; The first pulse echo The target signal of the sub-pulse is expressed as , For the The first pulse echo The interference signal of the echo sub-pulse; represents the sub-pulse width, is the frequency modulation slope of the sub-pulse, is the carrier frequency, Indicates the target delay of the echo; the frequency hopping interval is after digital down-conversion. The center frequency of the sub-pulse is expressed as .

[0087] More preferably, in an exemplary embodiment, the time domain correlation function of the interference and the target is constructed by a radar echo signal model, including:

[0088] No. The time domain correlation function of the target and interference of the interfered sub-pulse is:

[0089]

[0090] in, represents the prior information of interference, For the echo The target signal of sub-pulses is encoded as follows: , Indicates the echo The interference signal mixed in the sub-pulse, is the delay of the interference signal in the nth sub-pulse;

[0091] Based on the time domain correlation function of the target and the interference, the frequency coding sequence in the pulse is redesigned to obtain a feasible solution with high time domain orthogonality between the interference and the target, thereby reducing the correlation between the target and the interference. , under the condition that the frequency coding sequence satisfies the requirement that there are no repeated elements in the sequence, the sequence has The elements of the encoding sequence belong to the set , the objective function of the time domain correlation function of the interference and the target when solving can be expressed as:

[0092] .

[0093] This exemplary embodiment utilizes the characteristic that only some sub-pulses in the intra-pulse frequency coded radar echo may be subject to forwarding interference, and designs a waveform with higher time domain orthogonality between the interference and the target, making it easier to separate the target signal and suppress the interference.

[0094] More preferably, in an exemplary embodiment, the time domain correlation function of the interference and the target is solved by using a genetic algorithm to obtain an optimized intra-pulse frequency coding waveform:

[0095] Since the arrangement of the coding sequence is limited, the solution of this optimization problem is limited, and different solutions are independent of each other, which can be regarded as a combinatorial optimization problem. The number of solutions in this problem is related to the number of sub-pulses. The more sub-pulses there are, the more feasible solutions there are. In order to solve this optimization problem, a genetic algorithm is used to solve it.

[0096] Genetic algorithm is a commonly used heuristic optimization algorithm of global random search. It imitates the natural selection and inheritance process of Darwin's theory of evolution. Starting from the initial population, it produces a group of individuals with higher population fitness through random selection, crossover and mutation operations, and obtains high-quality solutions or optimal solutions to the problem through continuous iteration.

[0097] Based on genetic algorithm, the intra-pulse frequency coded waveform sequence is optimized to improve the time domain orthogonality of the waveform and obtain the optimized intra-pulse frequency coded waveform.

[0098] The specific operation of the algorithm is as follows:

[0099] (1) Create an initial population

[0100] The initial population is a set of valid candidate solutions, and each individual in the population is a feasible solution to the problem.

[0101] (2) Calculate population fitness

[0102] The fitness function is calculated for each individual in the population. After the initial population performs this operation, selection, crossover, and mutation operations are performed, and then the population fitness is recalculated for each individual in the new population.

[0103] (3) Selection

[0104] The random sampling method of roulette wheel selection is adopted. The probability of an individual entering the next generation ( ) is equal to the ratio of its population fitness to the sum of the fitness of all individuals in the population, and the formula is expressed as:

[0105]

[0106] In the formula, Indicates The fitness of the population of each individual (calculated based on the function value of the time domain correlation function), is the total number of individuals in the population.

[0107] (4) Cross

[0108] The crossover operation refers to exchanging some elements of two individuals in the population to form a new individual. Two individuals are randomly selected from the population for single-point crossover, that is, exchanging the value of one element of the two individuals.

[0109] (5) Variation

[0110] The operation of changing an element of an individual in a population to form a new individual is called mutation.

[0111] (6) Algorithm termination

[0112] After performing a selection, crossover, and mutation operation, determine whether the termination condition is met (for example, the number of cycles reaches the preset maximum value). If so, exit the loop and select the individual with the highest fitness in the population. Otherwise, continue to execute operations (2) to (5).

[0113] The latter step may specifically include three steps:

[0114] (1) For The echo signal is digitally down-converted to obtain the baseband echo signal. Based on the interference prior information and the characteristic that the interference signal amplitude is much higher than the target signal amplitude, the interfered echo signal segment is extracted from the radar echo.

[0115] (2) Taking a sub-pulse width as a segment length, the extracted signal is segmented, and the time-frequency matrix of the corresponding segment is obtained by short-time Fourier transform. The time-frequency matrix of each signal segment is truncated by sliding window using the time-frequency window function, and the truncated result is subjected to inverse short-time Fourier transform;

[0116] (3) Calculate the correlation between the new time domain signal and the pulse pressure reference signal, select the part with the highest correlation as the target signal, suppress the rest, and then superimpose the uninterrupted segment signal to obtain the echo signal after interference suppression.

[0117] More preferably, in an exemplary embodiment, the intra-pulse frequency coded waveform is transmitted as a radar transmission waveform, and a corresponding echo signal is obtained; for the echo signal, different time-frequency signals are intercepted through a time-frequency domain window to obtain a new time-frequency domain matrix, and the time-frequency domain matrix is ​​inversely transformed, including:

[0118] For The echo signal is digitally down-converted to obtain a baseband echo signal; based on the interference prior information and the characteristic that the interference signal amplitude is much higher than the target signal amplitude, the interfered echo signal segment is extracted from the echo signal;

[0119] The extracted signal is segmented with a sub-pulse width as a segment length. The total width of the interference sub-pulse extracted by the radar is , the sub-pulse width is , then a total of slice fragments, represents rounding down; where the interfered sub-pulse The time domain signal function of each segment is expressed as:

[0120]

[0121] In the formula, Indicates the target echo signal fragments, For noise, To interfere; Indicates The target time domain envelope in the clip, For the The first The interference time domain envelope; Delay for the target, Indicates The carrier frequency of each fragment, Indicates Fragment The interfering carrier frequency;

[0122] The total is The interference signal data matrix composed of all slice fragments is expressed as:

[0123]

[0124] Perform short-time Fourier transform on each interference segment and process the interference and target echo signals in the frequency domain. The time-frequency matrix of each segment is expressed as:

[0125]

[0126] in, is the center of the window function, Refers to short-time Fourier transform, is the window function of the sliding window in the time-frequency domain;

[0127] Use the time-frequency window function to perform sliding window interception on the time-frequency matrix of each signal segment to obtain a new time-frequency domain matrix ;

[0128]

[0129]

[0130] Among them, the time-frequency domain sliding window length is , the sliding window step length is , Represents the Hadamard product. Indicates A window function, ~ Behavior , , ; The total number of window functions in the entire interfered sub-pulse signal is , ;

[0131] Perform inverse short-time Fourier transform on the intercepted result to obtain the time domain signal :

[0132] .

[0133] like Figure 2 As shown in the figure, a time-frequency diagram of a baseband echo signal of a pulse frequency coded waveform of the present invention is shown, wherein the solid line segment is the target signal and the dotted line segment is the interference signal; there are a total of Sub-pulses, represents the pulse width of a sub-pulse, Indicates the pulse intensity of a transmitted pulse, is the frequency modulation bandwidth of a sub-pulse, express The total bandwidth of the sub-pulse frequency modulation. Indicates The target center frequency of the sub-pulse, the jammer After sampling the emission sub-pulse, The interference center frequency of the sub-pulse forwarding is .

[0134] More preferably, in an exemplary embodiment, the target recognition and interference suppression based on time domain correlation includes:

[0135] Calculate the correlation between the new time domain signal and the pulse pressure reference signal: recalculate Time domain correlation with the reference signal used for pulse compression in radar, The window function intercepts the total A new time-frequency matrix, vector After the corresponding time-frequency domain sliding window is intercepted The correlation value of the interference and target mixed signal and the pulse compression reference signal represented by the time-frequency matrix; the time domain signal corresponding to each time-frequency matrix With pulse pressure reference signal The correlation function is given by:

[0136]

[0137] Maximum value in a vector The corresponding time-frequency data matrix That is, the time-frequency matrix of the target signal, the time domain signal after inverse short-time Fourier transform That is, the target signal in the sub-pulse is retained and extracted, and the rest is suppressed;

[0138] The sub-pulse segments after interference suppression and the sub-pulse segments without interference are superimposed to obtain the target echo signal without intermittent forwarding interference.

[0139] The effect of the present invention can be further illustrated by the following simulation:

[0140] (1) Simulation scenarios and parameters

[0141] For the simulation under the interference environment of single intermittent sampling direct forwarding interference, it is assumed that there is a target and a jammer in the scene, the interference type is intermittent sampling direct forwarding interference, and the radar working waveform is an intra-pulse frequency coded waveform. It can be seen from the algorithm of interference suppression by sliding window in the time-frequency domain that the algorithm needs to set the sub-pulse width of the intra-pulse frequency coded waveform to be the same as the interference sampling duration of the jammer. The radar waveform parameters and intermittent sampling forwarding interference parameters used in the simulation experiment are shown in the following table.

[0142] Table 1 Shape parameters and intermittent sampling forwarding interference parameters

[0143]

[0144] (2) Simulation content

[0145] First, the intra-pulse frequency coding waveform needs to be optimized. Based on the interference prior information, the jammer sampling period is two sub-pulse widths of the radar transmission waveform, and the jammer working duty cycle is 50%. The echo time-frequency diagram before the intra-pulse frequency coding waveform optimization is shown in Figure 2. Figure 3 As shown, it is known from the interference prior information that the interference signal amplitude is greater than the target signal amplitude, and part of the target echo in the figure is affected by the interference; Figure 4 This is the optimized echo time-frequency diagram. Comparing the time-frequency diagram before waveform optimization with the time-frequency diagram after waveform optimization, it can be seen that the frequency domain distinction between the target and interference of the interfered segment in the optimized echo time-frequency diagram is significantly increased, and the echo of this waveform is easier to separate interference.

[0146] Figure 5 When the genetic algorithm is used to optimize the waveform, the convergence curve of the correlation between the number of algorithm iterations and the target interference shows that when the number of iterations reaches 20, the correlation drops from 54.982 to 12.583. It can be seen that the genetic algorithm greatly reduces the correlation between interference and target.

[0147] Figure 6 This is the echo time-frequency diagram after interference suppression according to the time-frequency domain sliding window interference suppression algorithm. Since the waveform is optimized, there is little interference residue after the interference suppression algorithm is processed. In the echo time-frequency diagram, the interfered sub-pulse is superimposed with the uninterrupted sub-pulse after the interference signal is removed, the target information loss is small, and the target is easier to identify.

[0148] Figure 7 The figure shows the comparison results of the echo signals before and after interference suppression after pulse compression processing using the optimized intra-pulse frequency coding waveform. After interference suppression, the target signal has a small loss in suppression amplitude, and the interference signal suppression effect is good.

[0149] See also Figure 8 , Figure 8 The electronic device provided in an exemplary embodiment of the present invention includes a memory and a processor, wherein the memory stores computer instructions that can be executed on the processor, and the processor executes the computer instructions as follows: Figure 1 The steps of the method.

[0150] See also Fig. 9 , Fig. 9 A computer storage medium provided in an exemplary embodiment of the present invention is shown, on which computer instructions are stored, and when the computer instructions are executed, the following are executed: Figure 1 The steps of the method.

[0151] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0152] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A time-domain orthogonal frequency coded waveform design and interference suppression method, characterized in that: The following steps are involved: Based on the radar echo signal model, the time domain correlation function of the interference and the target is constructed, and the constructed time domain correlation function is solved to obtain the optimized intra-pulse frequency coding waveform; Transmitting the intra-pulse frequency coded waveform as a radar transmission waveform and acquiring a corresponding echo signal; For the echo signal, different time-frequency signals are intercepted through a time-frequency domain window to obtain a new time-frequency domain matrix, and the new time-frequency domain matrix is ​​inversely transformed to realize target recognition and interference suppression based on time domain correlation; The radar echo signal model includes: Assume that there is a target and a forwarding jammer in the radar's observation scene. The jammer's interference type is intermittent sampling direct forwarding interference. The signal received by the radar includes the target echo signal, the interference signal and noise. Based on the scene prior information, a radar echo signal model is constructed. If there are targets and interference signals in the radar detection scene, the echo signal received by the radar can be expressed as: S(t)=S r (t)+N(t)+J(t); The target signal in the echo is S r (t); N(t) represents noise; the interference signal in the echo is J(t); The interference and target echo signal S received by the radar i (t) The radar echo signal model is expressed as: Where σ represents the scattering coefficient of the target; the target signal of the nth sub-pulse in the ith pulse echo is expressed as S n (t), J n (t) is the interference signal of the nth echo sub-pulse in the ith pulse echo; rect() is the rectangular pulse function, T w represents the sub-pulse width, is the frequency modulation slope of the sub-pulse, f0 is the carrier frequency, τ i represents the target delay of the echo; after the frequency hopping interval is digitally down-converted, the center frequency of the nth sub-pulse is expressed as Among them, c n For pulse coding, B w is the frequency modulation bandwidth of a sub-pulse, and N is the total number of sub-pulses in a transmitted pulse; The time domain correlation function of interference and target is constructed through the radar echo signal model, including: The target and interference time domain correlation function of the nth interfered sub-pulse is: Among them, γ represents the prior information of interference, S n (t,c n ) is the target signal of the nth sub-pulse in the echo, and the pulse coding method is c n , J n (t+τ n ,γ) represents the interference signal mixed in the nth sub-pulse of the echo, τ n represents the delay of the interference signal in the nth sub-pulse, and t represents time; The elements of the coding sequence belong to the set {1, 2, 3, ..., N}, and the objective function of the time domain correlation function of the interference and the target when solving is expressed as:

2. The time-domain orthogonal frequency coded waveform design and interference suppression method according to claim 1, characterized in that: Transmitting the intra-pulse frequency coded waveform as a radar transmission waveform and acquiring a corresponding echo signal; For the echo signal, different time-frequency signals are intercepted through the time-frequency domain window to obtain a new time-frequency domain matrix, and the time-frequency domain matrix is ​​inversely transformed, including: Performing digital down-conversion on the nth echo signal to obtain a baseband echo signal; extracting the interfered echo signal segment from the echo signal according to the interference prior information; The extracted signal is segmented with a sub-pulse width as a segment length. The total width of the interference sub-pulse extracted by the radar is T J , the sub-pulse width is T w , then a total of slice fragments, represents rounding down; wherein the time domain signal function of the mth segment of the interfered sub-pulse is expressed as: In the formula, S r (t,m) represents the mth segment of the target echo signal, N(t) is the noise, and J(t,m) is the interference; represents the target time domain envelope in the mth segment, is the i-th interference time domain envelope in the m-th segment; τ is the target delay, f m represents the carrier frequency of the mth segment, f m,i represents the carrier frequency of the ith interference in the mth segment; The interference signal data matrix composed of all slice segments with a total number of M is expressed as: Perform short-time Fourier transform on each interference segment, process the interference and target echo signals in the frequency domain, and the time-frequency matrix of the mth segment is expressed as: Where δ is the center of the window function, STFT refers to short-time Fourier transform, and W is the window function of the sliding window in the time-frequency domain; The time-frequency window function is used to perform sliding window interception on the time-frequency matrix of each signal segment to obtain a new time-frequency domain matrix Q mi ′; Q mi ′=Q mi ⊙ζ i ; W i =[ε0 ε1 … ε0] T ; Among them, the time-frequency domain sliding window length is λ, the sliding window step size is Δ, ⊙ represents the Hadamard product, W i represents the i-th window function, whose 1+i·Δ~i·Δ+λ line is ε1, ε0=[0 0 … 0], ε1=[1 1 … 1]; the total number of window functions in the entire interfered sub-pulse signal is Perform inverse short-time Fourier transform on the intercepted result to obtain the time domain signal S mi ′(t): S mi ′(t)=ISTFT(Q mi ′); Here, ISTFT refers to Inverse Short Time Fourier Transform.

3. The time-domain orthogonal frequency coded waveform design and interference suppression method according to claim 2, characterized in that: The target recognition and interference suppression based on time domain correlation include: Calculate the correlation between the new time domain signal and the pulse pressure reference signal: Recalculate S mi ′(t) is the time domain correlation of the reference signal used by the radar for pulse compression. The N window functions intercept and generate N new time-frequency matrices. The vector η = [R m1 …R mN ] The correlation value of the interference and target mixed signal and the pulse pressure reference signal represented by the N time-frequency matrices after the time-frequency domain sliding window is intercepted; the time domain signal S corresponding to each time-frequency matrix mi ′(t) and pulse pressure reference signal The correlation value is: The maximum value R in the vector η mi The corresponding time-frequency data matrix Q mi ′ is the time-frequency matrix of the target signal, and the time domain signal S after inverse short-time Fourier transform mi ′(t) is the target signal in the sub-pulse, and S is retained and extracted. mi ′(t) corresponds to the signal part, suppressing the addition of S mi The rest of the signal except the one corresponding to ′(t); The sub-pulse segments after interference suppression and the sub-pulse segments without interference are superimposed to obtain the target echo signal with the intermittent forwarding interference eliminated.

4. The time-domain orthogonal frequency coded waveform design and interference suppression method according to claim 1, characterized in that: Genetic algorithm is used to solve the constructed time domain correlation function.

5. An electronic device comprising a memory and a processor, wherein the memory stores computer instructions that can be executed on the processor, wherein: When the processor executes the computer instructions, the steps of the method according to any one of claims 1 to 4 are performed.

6. A computer storage medium having computer instructions stored thereon, characterized in that: When the computer instructions are executed, the steps of the method according to any one of claims 1 to 4 are executed.

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