Time-frequency fusion electromagnetic method transmitted waveform multi-frequency synthesis method and system

Abstract

The invention belongs to the technical field of earth exploration, and discloses a time-frequency fusion electromagnetic method transmitted waveform multi-frequency synthesis method and system, and the method comprises the steps: carrying out the Fourier expansion of a time-frequency fusion signal, obtaining a DC component represented by a switching angle, and all harmonic waves represented by the switching angle, one emission period of the time-frequency fusion signal contains two time domain observation windows; selecting target sub-harmonics from the harmonics to establish a target function; and calculating an optimal value of the target function by using a genetic algorithm, taking a switching angle corresponding to the optimal value as an optimal switching angle, and determining a transmitted waveform according to the optimal switching angle, the length of the time domain observation windows and the starting time interval of the two time domain observation windows. The problem that signals need to be transmitted multiple times when a group of frequency points are detected in the electromagnetic exploration process is solved. When a group of frequency points are detected, the generated emission waveform can emit a waveform comprising a plurality of frequency combinations in the group of frequency points, and multi-frequency combined emission can reduce the emission times.

Description

Technical Field

[0001] The present application belongs to the field of earth exploration technology, and specifically relates to a method and system for synthesizing multi-frequency waveforms transmitted by a time-frequency fusion electromagnetic method. Background Art

[0002] In the field of electromagnetic exploration, bipolar square waves are often used for time domain electromagnetic detection or pseudo-random sequences are used for frequency domain electromagnetic detection. The two are complementary in detection range. In the time domain electromagnetic detection method, at the moment when the pulse current is turned off, the receiving system receives the weakened secondary field signal in the near area, and the frequency domain electromagnetic method transmits pseudo-random pulses with adjustable frequency to observe the superposition field of the primary field and the secondary field in the far area. In the process of transmitting electromagnetic detection signals, the time-frequency fusion signal transmits a signal containing multiple frequencies and having a time domain observation window, which can fuse the two. At present, the output signal used by the time-frequency fusion detection method is only to add a time domain observation window to the frequency domain signal, so that the obtained signal can only contain the second harmonic and the fourth harmonic except the fundamental wave. In the detection process, it is necessary to transmit the signal multiple times to complete the detection of a set of frequency points, which makes the detection process cumbersome, the detection time is long, and the concentration of the harmonic energy to be used is low. Summary of the invention

[0003] The embodiments of the present application provide a method and system for synthesizing multi-frequency waveforms of electromagnetic transmission by time-frequency fusion, which solves the problem that multiple transmission signals are required to complete the detection of a group of frequency points during the electromagnetic exploration process.

[0004] This application is implemented in this way. A first aspect of an embodiment of the present application provides a method for synthesizing a multi-frequency waveform of an electromagnetic transmission method using time-frequency fusion, comprising: Performing Fourier expansion on the time-frequency fusion signal to obtain a DC component represented by a switching angle and each harmonic represented by a switching angle, wherein one transmission cycle of the time-frequency fusion signal contains two time domain observation windows; The target subharmonic is selected from each harmonic to establish the objective function, which is expressed as: , in, is the objective function, is the first target harmonic amplitude, is the second target harmonic amplitude, For the Target subharmonic amplitude, for The amplitude of the subharmonics, is the total harmonic number of low-order harmonics that need to be optimized, is the amplitude of the DC component, is the average value of the target subharmonic amplitude, is the variance of the target subharmonic amplitude, is the total energy of the low-order harmonics that need to be optimized, , , They are respectively the target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics except the target subharmonic in the low-order harmonics to be optimized, and the variance weighting coefficient of the target subharmonic amplitude; The optimal value of the objective function is calculated using a genetic algorithm. The switching angle corresponding to the optimal value is the optimal switching angle. The emission waveform is determined according to the optimal switching angle, the length of the time domain observation window and the start time interval of two time domain observation windows.

[0005] In one embodiment, the time-frequency fusion signal includes a first time domain observation window and a second time domain observation window within one transmission cycle, and a plurality of first switching angles with equal distribution lengths are set after the first time domain observation window and before the second time domain observation window, and a plurality of second switching angles with equal distribution lengths are set after the second time domain observation window.

[0006] In one embodiment, the magnitude of the first switching angle is limited to: , The magnitude relationship of the first switching angle satisfies ,in, is the length of the time domain observation window, The time interval between the start and end of two time domain observation windows, Indicates Switch angle, represents the total number of the first switching angles, ; The size of the second switching angle is limited to: , The magnitude relationship of the second switching angle satisfies , the second switching angle , Indicates the total number of switching angles.

[0007] In one embodiment, the use of a genetic algorithm to calculate the optimal value of the objective function includes: randomly generating a binary code, and corresponding the first four bits of the binary code to the start time intervals of two time domain observation windows, and then every six bits of the binary code to a switching angle, and the switching angles include a first switching angle and a second switching angle; The fitness of the objective function is calculated after converting the binary code into the starting time interval and the switching angle of two time domain observation windows; After selecting and calculating according to the fitness, crossover and mutation operations are performed to complete the calculation of an iterative cycle; The calculation of multiple cycles is repeated to obtain the converged binary code, and the binary code is converted into the switching angle and the start time interval of two time domain observation windows.

[0008] In one embodiment, after one iteration cycle of calculation is completed, the target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics in the low-order harmonics to be optimized, and the variance weighting coefficient of the target subharmonic amplitude are adjusted according to the current optimal binary code.

[0009] In one embodiment, the adjustment method is: , , , in, , … All of them come from the amplitude of the corresponding target subharmonic calculated in the current iteration cycle, is the length of the time domain observation window. During the adjustment process, if If Change the value of to 0.1.

[0010] In one embodiment, converting the binary code into the switching angle and the start time interval of two time domain observation windows includes: , , in, For the Switch angle, The value of is 1~ , for The lower limit of the value range, for The upper limit of the value range, ~ is the binary value corresponding to the start time of the second time domain observation window in a transmission cycle, ~ For the The binary value of the number of bits corresponding to the switching angle, is the starting time interval of two time domain observation windows.

[0011] A second aspect of the embodiment of the present application provides a time-frequency fusion electromagnetic method transmission waveform multi-frequency synthesis system, comprising: A harmonic extraction unit, used for Fourier expansion of the time-frequency fusion signal to obtain a DC component represented by a switching angle and each harmonic represented by a switching angle, wherein one transmission cycle of the time-frequency fusion signal contains two time domain observation windows; The harmonic selection unit is used to select the target subharmonic from each harmonic to establish an objective function, and the objective function is expressed as: , in, is the objective function, is the first target harmonic amplitude, is the second target harmonic amplitude, For the Target subharmonic amplitude, for The amplitude of the subharmonics, is the total harmonic number of low-order harmonics that need to be optimized, is the amplitude of the DC component, is the average value of the target subharmonic amplitude, is the variance of the target subharmonic amplitude, is the total energy of the low-order harmonics that need to be optimized, , , They are respectively the target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics in the low-order harmonics to be optimized except the target subharmonic, and the variance weighting coefficient of the target subharmonic amplitude; The harmonic optimization unit calculates the optimal value of the objective function using a genetic algorithm. The switching angle corresponding to the optimal value is the optimal switching angle. The emission waveform is determined according to the optimal switching angle, the length of the time domain observation window and the start time interval of the two time domain observation windows.

[0012] A third aspect of an embodiment of the present application provides a time-frequency fusion electromagnetic method transmission waveform multi-frequency synthesis system, including: a processor; when the processor calls a computer program or instruction in a memory, the method of the first aspect mentioned above is executed.

[0013] A fourth aspect of an embodiment of the present application is a computer-readable storage medium, wherein the computer-readable storage medium is used to store a computer program. When the computer program is executed, the method of the first aspect described above is executed.

[0014] Compared with the prior art, the embodiments of the present application have at least the following technical effects: The generated transmission waveform can emit a waveform containing multiple frequency combinations in a group of frequency points when detecting a group of frequency points. The multi-frequency joint transmission can reduce the number of transmissions and solve the problem of cumbersome electromagnetic exploration process. In addition, the energy of harmonics is higher, and the transmitted signal can be received with a higher amplitude, which can avoid the situation where the underground apparent resistivity cannot be calculated due to excessive noise in the subsequent signal processing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of a flow chart of a method for synthesizing a multi-frequency electromagnetic transmission waveform using a time-frequency fusion method provided in an embodiment of the present application; Figure 2 A structural block diagram of a time-frequency fusion electromagnetic transmission waveform multi-frequency synthesis system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0017] In the field of electromagnetic exploration, the output signal used by the time-frequency fusion detection method is only a way to add a time domain observation window to the frequency domain signal. The signal obtained in this way can only contain the second harmonic and the fourth harmonic except the fundamental wave. In the detection process, it is necessary to transmit the signal multiple times to complete the detection of a set of frequency points, which makes the detection process cumbersome, the detection time is long, and the concentration of the harmonic energy to be used is low.

[0018] In response to the above problems, the embodiment of the present application provides a multi-frequency synthesis method for transmitting waveforms of the electromagnetic method using time-frequency fusion, designs a time-frequency fusion signal containing two time domain observation windows; obtains multiple harmonics through Fourier expansion; selects the target subharmonics required according to the needs of detection, establishes an objective function, and solves the objective function through iteration; increases the amplitude of the required harmonics and reduces the remaining low-frequency harmonics; finally, the optimal solution obtained by iteration is used to determine the transmitting waveform according to the optimal switching angle corresponding to the optimal solution, the length of the time domain observation window, and the starting time interval of the two time domain observation windows. A multi-frequency synthesis method for transmitting waveforms of the electromagnetic method using time-frequency fusion can synthesize a combination waveform of any harmonics, which can improve the detection efficiency and reduce the time required for detection during field electromagnetic exploration.

[0019] See also Figure 1 The flowchart of a method for synthesizing a multi-frequency electromagnetic transmission waveform using a time-frequency fusion method is shown. A method for synthesizing a multi-frequency electromagnetic transmission waveform using a time-frequency fusion method according to an embodiment of the present application includes: S1, Fourier expansion of the time-frequency fusion signal to obtain a DC component represented by a switching angle and each harmonic represented by a switching angle, wherein one transmission cycle of the time-frequency fusion signal contains two time domain observation windows; The time-frequency fusion signal has a fixed duty cycle, contains N switching angles in one transmission cycle, and has two time domain observation windows in one transmission cycle. The time domain observation window refers to the limited time region in which the voltage of the transmission signal is 0. The purpose of setting the time domain observation window is to receive the secondary field signal returned from the earth in the near area. The primary field strength emitted by the transmitting source is too high and will drown the secondary field signal. Therefore, the primary field power emitted by the transmitting source needs to be turned off to facilitate the reception of the secondary field signal returned from the earth.

[0020] The switching angle refers to the angle corresponding to the specific time of on and off in each transmission cycle. These angles determine the pulse width and distribution of the transmission waveform.

[0021] By performing Fourier expansion on the time-frequency fusion signal, the time-frequency fusion signal contains two time domain observation windows in one transmission cycle. The periodic time-frequency fusion signal can be decomposed into a DC component and a series of sine and cosine components through Fourier expansion. These series of sinusoidal wave components are harmonics in the embodiments of the present application. These harmonics and DC components have a certain relationship with the switching angle. Through Fourier expansion, the DC component represented by the switching angle and the harmonics represented by the switching angle are obtained.

[0022] It can be understood that Fourier expansion refers to Fourier transforming the time-frequency fusion signal and converting a time domain signal to the frequency domain for representation. After Fourier expansion, the contained harmonics include high-frequency harmonics and low-frequency harmonics according to the frequency. In geological exploration, high-frequency harmonics cannot play a role. Fourier expansion can separate the low-frequency harmonics and high-frequency harmonics that can be used.

[0023] In some embodiments, the time-frequency fusion signal is expressed as: , It can be understood that one transmission cycle includes two time domain observation windows, which are represented here by the first time domain observation window and the second time domain observation window, where: Indicates the change of time, is the power supply voltage amplitude, represents the voltage varying with time, is the length of the time domain observation window, is the starting time interval of the two time domain observation windows. It can be understood that the starting time interval of the two time domain observation windows is from 0 to , The corresponding moment is also the start time of the second time domain observation window within a launch cycle. is the switching angle, i.e. the voltage waveform of the transmitter at time When the switching angle is , the voltage value jumps, and the voltage changes from positive to negative, or from negative to positive. The number of switching angles before the second time domain observation window is .for In order to distinguish the switch angles of the two distribution areas, the switch angle before the second time domain observation window is used as the first switch angle, and the multiple switch angles set after the second time domain observation window are used as the second switch angle.

[0024] The time intervals between the start times of the two time domain observation windows in the embodiments of the present application refer to the interval between the start time of the first time domain observation window and the start time of the second time domain observation window in the same transmission cycle.

[0025] In one embodiment, both the first switching angle and the second switching angle are restricted.

[0026] The size of the first switching angle is limited to: , The magnitude relationship of the first switching angle satisfies ,in, is the length of the time domain observation window, Indicates Switch angle, represents the total number of the first switching angles, ; The size of the second switching angle is limited to: , The magnitude relationship of the second switching angle satisfies , the second switching angle , Indicates the total number of switching angles.

[0027] In one embodiment, the DC component represented by the switching angle and the harmonics represented by the switching angle obtained by Fourier expansion are: , , , , in, is the DC component, The number of harmonics currently being calculated, that is, the total harmonic number including high-frequency harmonics and low-frequency harmonics. for The sinusoidal components of the subharmonics, for The cosine component of the subharmonic, for The amplitude of the subharmonic. The amplitude of the harmonic is obtained by the sine component of the harmonic and the cosine component of the harmonic.

[0028] It can be understood that the amplitude of each harmonic is related to the switching angle, the length of the time domain observation window and the start time interval of two time domain observation windows.

[0029] S2 selects the target subharmonic from each harmonic to establish the objective function, which is expressed as: , in, is the first target harmonic amplitude, is the second target harmonic amplitude, For the Target subharmonic amplitude, for The amplitude of the subharmonics, is the total harmonic number of low-order harmonics that need to be optimized. The value is selected according to the amplitude of each harmonic. For high-frequency harmonics, the amplitude of the harmonic is very small. Select a value, remove some harmonics, and the remaining harmonics are used as low-frequency harmonics. is the amplitude of the DC component, is the average value of the target subharmonic amplitude, is the variance of the target subharmonic amplitude, is the total energy of the low-order harmonics that need to be optimized, , , They are respectively the target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics except the target subharmonic in the low-order harmonics to be optimized, and the variance weighting coefficient of the target subharmonic amplitude; Through step S1, multiple harmonics are obtained after Fourier expansion. For different detection requirements, it may be necessary to select from multiple harmonics. Harmonics, selected The amplitude of a harmonic may be relatively high or relatively small among multiple harmonics. When conducting electromagnetic detection, the energy of the harmonic required in the transmitted waveform is high and The amplitudes of the harmonics need to be as equal as possible to ensure The energy of the harmonics is consistent.

[0030] The selected harmonic is used as the target subharmonic, and the target subharmonic is used to establish the target function.

[0031] The objective function includes three items, the first of which represents the target subharmonic energy, and sets a target subharmonic energy weighting coefficient. The second item is the total energy of the remaining harmonics other than the target subharmonics in the low-order harmonics that need to be optimized, and sets a weighting coefficient for the total energy of the remaining harmonics other than the target subharmonics in the low-order harmonics that need to be optimized. The last item is the variance of the target subharmonic amplitude, and also sets a variance weighting coefficient for the target subharmonic amplitude.

[0032] The low-order harmonics that need to be optimized are the low-order harmonics remaining after removing the high-frequency harmonics in the multiple harmonics in step S1. These low-frequency harmonics need to be optimized in the objective function. The optimization process is to increase the amplitude of the target harmonic and reduce the amplitude of the remaining harmonics, that is, to reduce the total energy of the remaining harmonics except the target harmonic in the low-order harmonics that need to be optimized, thereby increasing the energy proportion of the target harmonic.

[0033] S3 uses a genetic algorithm to calculate the optimal value of the objective function. The switching angle corresponding to the optimal value is the optimal switching angle. The emission waveform is determined according to the optimal switching angle, the length of the time domain observation window and the start time interval of the two time domain observation windows.

[0034] The process of optimizing the objective function is to continuously optimize the switching angle and the start time interval of the two time domain observation windows to make the target harmonics of equal amplitude and increase the energy proportion of the target harmonics, and weaken the amplitude and energy of other harmonics.

[0035] In the embodiment of the present application, a genetic algorithm is used to calculate the optimal value of the objective function. After the genetic algorithm is iterated, the switching angle corresponding to the optimal value is used as the optimal switching angle. At this time, the target subharmonics are basically at equal amplitudes, and the energy proportion of the target subharmonics is the highest. The transmission waveform can be determined based on the optimal switching angle, the length of the time domain observation window, and the starting time interval of the two time domain observation windows. Using the determined transmission waveform for signal transmission can achieve one-time transmission and complete the detection of multiple frequency points. Improve the efficiency of detection.

[0036] In one embodiment, the optimal value of the objective function is calculated using a genetic algorithm, including: randomly generating a binary code, and corresponding the first four bits of the binary code to the start time intervals of two time domain observation windows, and then every six bits of the binary code correspond to a switching angle, and the switching angles include a first switching angle and a second switching angle; The fitness of the objective function is calculated after converting the binary code into the starting time interval and the switching angle of two time domain observation windows; After selecting and calculating according to the fitness, crossover and mutation operations are performed to complete the calculation of an iterative cycle; The calculation of multiple cycles is repeated to obtain the converged binary code, and the binary code is converted into the switching angle and the start time interval of two time domain observation windows.

[0037] The core idea of ​​genetic algorithm is to optimize the objective function by simulating natural selection and genetic mechanism. It mainly includes: encoding, initializing population, fitness evaluation, selection, crossover, mutation and iteration. Among them, encoding is to express the solution of the optimization problem in a form suitable for genetic operation. Coding is in various forms, such as binary coding, real number coding, permutation coding, tree coding, etc. Initializing population is to generate an initial population, and each individual is a possible solution. The population size is usually selected according to the scale and complexity of the problem. Fitness evaluation is to calculate the fitness of each individual, and the fitness function is usually directly related to the objective function. The higher the fitness, the greater the probability of the individual being selected. Selection is to select individuals for reproduction according to fitness, exchange some genes of two individuals, and generate new individuals; mutation is to randomly change some genes of individuals to increase the diversity of the population; iteration is to repeat the fitness evaluation, selection, crossover and mutation steps until the termination condition is met.

[0038] The embodiment of the present application uses a genetic algorithm to optimize the transmission waveform. By combining the established objective function, the switch angle and the start time interval of the two time domain observation windows are binary-coded. After the binary code is converted into the start time interval of the two time domain observation windows and the switch angle, the fitness of the objective function is calculated. The fitness is , is the calculated minimum value of the objective function. is the objective function.

[0039] In one embodiment, the formula used to convert the binary code into the starting time interval and the switching angle of the two time domain observation windows is: , , in, For the Switch angle, The value of is 1~ , for The lower limit of the value range, for The upper limit of the value range, ~ is the binary value corresponding to the start time of the second time domain observation window in a transmission cycle, ~ For the The binary value of the number of bits corresponding to each switching angle.

[0040] According to the calculated starting time interval and switching angle of the two time domain observation windows and the expression of the objective function, the fitness of the objective function can be obtained.

[0041] Objective Function Calculate the fitness in a genetic algorithm: , is the calculated minimum value of the objective function.

[0042] Through the selection operation, the probability of each individual being selected is related to the fitness. The greater the fitness, the greater the probability of being selected. The probability size is: , For the The probability of an individual being selected is For the The fitness of an individual, For the The fitness of each individual; The selection process is: Generate a random number ,judge and Size relationship, For the The probability of an individual being selected is Indicates the serial number of the individual that is currently being judged whether to be selected during the selection process. Starting from 1, if Less than , then select the current individual as the next generation population individual, if Greater than , it indicates that the current individual has not been selected, and the next individual is judged whether it meets the conditions until the next generation of individuals is selected. Repeat this process until all the next generation of individuals are selected. is the number of individuals in the population. After selection, the next generation of population is formed. The individuals here refer to binary codes.

[0043] After each iteration, the current optimal binary code is obtained, and then the binary code is converted into the switching angle and the start time interval of the two time domain observation windows. The target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics in the low-order harmonics to be optimized, and the variance weighting coefficient of the target subharmonic amplitude are adjusted.

[0044] The adjustment process is: , , , in, , … All of them come from the amplitude of the corresponding target subharmonic calculated in the current iteration cycle, is the length of the time domain observation window. During the adjustment process, if If Change the value of to 0.1.

[0045] The adjusted weighted coefficient is used in the next iteration to improve the optimization efficiency.

[0046] In order to further analyze and explain the use of genetic algorithms to calculate the optimal value of the objective function in the embodiments of the present application, reference is made to the following application embodiments, including: Initialize the population and set the population size. The population is a collection of individuals. The population size is the number of individuals in a population, the binary code length, that is, the length of the individual, the crossover probability, the mutation probability, and the weight coefficient of the objective function initialization; The target harmonics are selected as the first harmonic, the second harmonic, the third harmonic and the fourth harmonic, that is, , , , , are the amplitudes of the first harmonic, second harmonic, third harmonic and fourth harmonic respectively. , , , the population size of the genetic algorithm binary coding is , the length of the binary code is 100, the first four bits of the binary code correspond to the start time interval of the two time domain observation windows, and then every six bits of the binary code correspond to a switch angle. The genetic algorithm exits the loop when it executes 4000 times. Each individual contains Binary encoding of bits.

[0047] Take the crossover probability =0.1, mutation probability =0.05, the weight coefficients of the objective function initialization include the target harmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics in the low-order harmonics to be optimized, and the variance weighting coefficient of the target harmonic amplitude, which are =1, =1, =10.

[0048] Assign the initial value to the binary code, and the number of binary code groups depends on the set population size; Randomly generate binary codes and convert the binary codes into the start time intervals of two time domain observation windows With switch angle ~ , producing satisfaction The initial value of and calculate the fitness of the objective function; The starting time interval of two time domain observation windows With switch angle ~ The corresponding conversion formula is , , in, is the switching angle of the current conversion, The value of is 1~ , for The lower limit of the value range, for The upper limit of the value range, ~ The binary value corresponding to the start time of the second time domain window, ~ For the The binary value of the number of bits corresponding to each switching angle.

[0049] Genetic algorithm fitness calculation, and selection, crossover, and mutation operations.

[0050] The fitness is calculated based on the starting time interval and the switching angle of the two time domain observation windows obtained by binary code conversion.

[0051] The selection operation is performed, and the probability of each individual, that is, the binary code, being selected is related to its fitness. The greater the fitness, the greater the probability of being selected.

[0052] After the selection process, the next generation of population is formed.

[0053] Perform a crossover operation, select two groups of adjacent individuals in the population, and generate a random number between 0 and 1. If the random number is less than the crossover probability, perform a crossover operation, that is, randomly select a binary code and exchange all subsequent binary codes.

[0054] Perform a mutation operation to generate a random number between 0 and 1 for each individual in the population. If the random number is less than the mutation probability, perform a mutation operation, which is to randomly select a binary code and invert it.

[0055] After each genetic algorithm iteration cycle, the weight coefficient of the objective function is dynamically adjusted according to the current optimal individual situation.

[0056] Repeat fitness calculation, selection, crossover, mutation and dynamic adjustment of weight coefficient until the number of cycles meets the set value.

[0057] After the cycle is over, the binary code of the genetic algorithm converges, and the binary code is converted into a switching angle. For example, in one embodiment, , , , , , , , , , , , , , , , , , , The calculated value of the objective function is 2.4654.

[0058] If the values ​​of two adjacent switch angles are equal, there will be two instantaneous jumps, but in reality there will be no jump, which means they cancel each other out.

[0059] The final time-frequency fusion waveform is calculated. The amplitudes of the first harmonic, second harmonic, third harmonic and fourth harmonic of the target harmonic are respectively: , , , The target subharmonic accounts for 80.7% of the total energy of the time-frequency fusion signal, and the energy utilization rate is high. By changing to other harmonic amplitudes and being able to calculate with any combination of harmonic frequencies, faster detection can be achieved, the time required for the detection process can be reduced, and the detection efficiency can be improved.

[0060] The embodiment of the present application also provides a time-frequency fusion electromagnetic method transmission waveform multi-frequency synthesis system, and the time-frequency fusion electromagnetic method transmission waveform multi-frequency synthesis system and the time-frequency fusion electromagnetic method transmission waveform multi-frequency synthesis method can be compared and referenced with each other.

[0061] See also Figure 2 The embodiment of the present application provides a time-frequency fusion electromagnetic method transmission waveform multi-frequency synthesis system, comprising: A harmonic extraction unit, used for Fourier expansion of the time-frequency fusion signal to obtain a DC component represented by a switching angle and each harmonic represented by a switching angle, wherein one transmission cycle of the time-frequency fusion signal contains two time domain observation windows; The harmonic selection unit is used to select the target subharmonic from each harmonic to establish an objective function, and the objective function is expressed as: , in, is the first target harmonic amplitude, is the second target harmonic amplitude, For the Target subharmonic amplitude, for The amplitude of the subharmonics, is the total harmonic number of low-order harmonics that need to be optimized, is the amplitude of the DC component, is the average value of the target subharmonic amplitude, is the variance of the target subharmonic amplitude, is the total energy of the low-order harmonics that need to be optimized, , , They are respectively the target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics except the target subharmonic in the low-order harmonics to be optimized, and the variance weighting coefficient of the target subharmonic amplitude; The harmonic optimization unit calculates the optimal value of the objective function using a genetic algorithm. The switching angle corresponding to the optimal value is the optimal switching angle. The emission waveform is determined according to the optimal switching angle, the length of the time domain observation window and the start time interval of the two time domain observation windows.

[0062] In one embodiment, the time-frequency fusion signal containing two time domain observation windows processed by the harmonic extraction unit includes a first time domain observation window and a second time domain observation window in one transmission cycle, and a plurality of first switching angles with equal distribution lengths are set after the first time domain observation window and before the second time domain observation window, and a plurality of second switching angles with equal distribution lengths are set after the second time domain observation window.

[0063] In one embodiment, the harmonic optimization unit calculates the optimal value of the objective function using a genetic algorithm, including: randomly generating a binary code, and corresponding the first four bits of the binary code to the start time intervals of two time domain observation windows, and then every six bits of the binary code correspond to a switching angle, and the switching angles include a first switching angle and a second switching angle; The fitness of the objective function is calculated after converting the binary code into the starting time interval and the switching angle of two time domain observation windows; After selecting and calculating according to the fitness, crossover and mutation operations are performed to complete the calculation of an iterative cycle; The calculation of multiple cycles is repeated to obtain the converged binary code, and the binary code is converted into the switching angle and the start time interval of two time domain observation windows.

[0064] In one embodiment, the harmonic optimization unit is also used to adjust the target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics in the low-order harmonics to be optimized, and the variance weighting coefficient of the target subharmonic amplitude according to the current optimal binary code after the calculation of one iteration cycle is completed.

[0065] The embodiment of the present application also provides an electronic device, including a processor; when the processor calls a computer program or instruction in a memory, a method for multi-frequency synthesis of a time-frequency fusion electromagnetic emission waveform is executed. The processor communicates with the communication interface and the memory through a communication bus. The processor can call the logic instructions in the memory to execute the following method: Fourier expansion of the time-frequency fusion signal to obtain a DC component represented by a switching angle and each harmonic represented by a switching angle, wherein one emission cycle of the time-frequency fusion signal contains two time domain observation windows; a target subharmonic is selected from each harmonic to establish an objective function, and a genetic algorithm is used to calculate the optimal value of the objective function, wherein the switching angle corresponding to the optimal value is the optimal switching angle, and the emission waveform is determined according to the optimal switching angle, the length of the time domain observation window, and the starting time interval of the two time domain observation windows.

[0066] On the other hand, an embodiment of the present application also provides a computer-readable storage medium for storing a computer program. When the computer program is executed, the method in the above embodiment is executed.

[0067] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for synthesizing multi-frequency waveforms of electromagnetic emission by time-frequency fusion, characterized in that: include: Performing Fourier expansion on the time-frequency fusion signal to obtain a DC component represented by a switching angle and each harmonic represented by a switching angle, wherein one transmission cycle of the time-frequency fusion signal contains two time domain observation windows; The target subharmonic is selected from each harmonic to establish the objective function, which is expressed as: ， in, is the objective function, is the first target harmonic amplitude, is the second target harmonic amplitude, For the Target subharmonic amplitude, for The amplitude of the subharmonics, is the total harmonic number of low-order harmonics that need to be optimized, is the amplitude of the DC component, is the average value of the target subharmonic amplitude, is the variance of the target subharmonic amplitude, is the total energy of the low-order harmonics that need to be optimized, , , They are respectively the target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics except the target subharmonic in the low-order harmonics to be optimized, and the variance weighting coefficient of the target subharmonic amplitude; The optimal value of the objective function is calculated using a genetic algorithm. The switching angle corresponding to the optimal value is the optimal switching angle. The emission waveform is determined according to the optimal switching angle, the length of the time domain observation window and the start time interval of two time domain observation windows.

2. According to the method of claim 1, the method is characterized in that: The time-frequency fusion signal includes a first time domain observation window and a second time domain observation window in one transmission cycle, a plurality of first switching angles with equal distribution lengths are set after the first time domain observation window and before the second time domain observation window, and a plurality of second switching angles with equal distribution lengths are set after the second time domain observation window.

3. The method for synthesizing multi-frequency electromagnetic emission waveforms by time-frequency fusion according to claim 2 is characterized in that: The size of the first switching angle is limited to: , The magnitude relationship of the first switching angle satisfies ,in, is the length of the time domain observation window, is the starting time interval of two time domain observation windows, Indicates Switch angle, represents the total number of the first switching angles, ; The size of the second switching angle is limited to: ， The magnitude relationship of the second switching angle satisfies , the second switching angle , Indicates the total number of switching angles.

4. The method for synthesizing multi-frequency electromagnetic emission waveforms by time-frequency fusion according to claim 2 is characterized in that: The method of calculating the optimal value of the objective function by using a genetic algorithm includes: randomly generating a binary code, and corresponding the first four bits of the binary code to the start time intervals of two time domain observation windows, and then corresponding each six bits of the binary code to a switching angle, wherein the switching angles include a first switching angle and a second switching angle; The fitness of the objective function is calculated after converting the binary code into the starting time interval and the switching angle of two time domain observation windows; After selecting and calculating according to the fitness, crossover and mutation operations are performed to complete the calculation of an iterative cycle; The calculation of multiple cycles is repeated to obtain the converged binary code, and the binary code is converted into the switching angle and the start time interval of two time domain observation windows.

5. The method for synthesizing multi-frequency electromagnetic emission waveforms by time-frequency fusion according to claim 4 is characterized in that: After one iteration cycle of calculation is completed, the target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics in the low-order harmonics to be optimized, and the variance weighting coefficient of the target subharmonic amplitude are adjusted according to the current optimal binary code.

6. The method for synthesizing multi-frequency electromagnetic emission waveforms by time-frequency fusion according to claim 5, characterized in that: The adjustment method is: ， ， ， in, , … All of them come from the amplitude of the corresponding target subharmonic calculated in the current iteration cycle, is the length of the time domain observation window. During the adjustment process, if If Change the value of to 0.

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7. The method for synthesizing multi-frequency electromagnetic emission waveforms by time-frequency fusion according to claim 4, characterized in that: Convert the binary code into the switching angle and the start time interval of two time domain observation windows, including: ， ， in, For the Switch angle, The value of is 1~ , for The lower limit of the value range, for The upper limit of the value range, ~ is the binary value corresponding to the start time of the second time domain observation window in a transmission cycle, ~ For the The binary value of the number of bits corresponding to the switching angle, is the starting time interval of two time domain observation windows.

8. A time-frequency fusion electromagnetic method transmission waveform multi-frequency synthesis system, characterized in that: include: A harmonic extraction unit, used for Fourier expansion of the time-frequency fusion signal to obtain a DC component represented by a switching angle and each harmonic represented by a switching angle, wherein one transmission cycle of the time-frequency fusion signal contains two time domain observation windows; The harmonic selection unit is used to select the target subharmonic from each harmonic to establish an objective function, and the objective function is expressed as: ， in, is the objective function, is the first target harmonic amplitude, is the second target harmonic amplitude, For the Target subharmonic amplitude, for The amplitude of the subharmonics, is the total harmonic number of low-order harmonics that need to be optimized, is the amplitude of the DC component, is the average value of the target subharmonic amplitude, is the variance of the target subharmonic amplitude, is the total energy of the low-order harmonics that need to be optimized, , , They are respectively the target subharmonic energy weighting coefficient, the total energy weighting coefficient of the remaining harmonics except the target subharmonic in the low-order harmonics to be optimized, and the variance weighting coefficient of the target subharmonic amplitude; The harmonic optimization unit calculates the optimal value of the objective function using a genetic algorithm. The switching angle corresponding to the optimal value is the optimal switching angle. The emission waveform is determined according to the optimal switching angle, the length of the time domain observation window and the start time interval of the two time domain observation windows.

9. An electronic device, characterized in that: include: processor; When the processor calls the computer program or instruction in the memory, the method according to any one of claims 1 to 7 is executed.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store a computer program. When the computer program is executed, the method according to any one of claims 1 to 7 is executed.

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