Multi-sequence combined wave construction method, system and transmitter

Abstract

The invention relates to a multi-sequence combined wave construction method and system and a transmitter, and belongs to the technical field of geophysical exploration industries, and the method comprises the steps: determining c frequency sequences according to a depth range to be detected and a required longitudinal resolution, the frequency sequences being equal-ratio frequency sequences with a common ratio of 2, and c being a positive integer greater than or equal to 2; the lowest frequency in the first frequency sequence is marked as a fundamental frequency fbase, and the lowest frequency and the fundamental frequency of the other frequency sequences meet the following relation: # imgabs0 # obtains a multi-sequence combined wave with consistent frequency density in a full frequency band based on the frequency sequence. According to the invention, the number of the frequency sequences is determined according to the depth range to be detected and the required longitudinal resolution, and the longitudinal resolution of deep exploration is improved by controlling the relationship between the lowest frequency of the other frequency sequences and the fundamental frequency in the first frequency sequence.

Description

Technical Field

[0001] The present invention relates to the technical field of geophysical exploration industry, and in particular to a multi-sequence combination wave construction method, system and transmitter. Background Art

[0002] Although the traditional high-order pseudo-random construction scheme can arbitrarily combine sequences, the frequency of each sequence is fixed. In exploration environments with industrial electricity such as towns, industrial areas, or near high-voltage lines, the interference of power frequency and its multiples will cause exploration data distortion, making it difficult to obtain high-quality exploration data, thus affecting exploration accuracy. At the same time, the multi-sequence combination waves constructed by traditional schemes have a longer wavelength as the frequency decreases, making the resolution of deep exploration data obtained by using low-frequency waves to explore deep areas low, which is difficult to meet exploration needs. Summary of the invention

[0003] In order to solve the above technical defects, the present invention provides a multi-sequence combination wave construction method, system and transmitter to improve the resolution of acquiring deep exploration data and improve the anti-interference ability.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] In a first aspect, an embodiment of the present invention provides a method for constructing a multi-sequence combination wave, which comprises the following steps:

[0006] Determine c frequency sequences according to the depth range to be detected and the required vertical resolution, wherein the frequency sequence is a geometric frequency sequence with a common ratio of 2, and c is a positive integer greater than or equal to 2;

[0007] And, the lowest frequency in the first frequency sequence is recorded as the fundamental frequency f base , the lowest frequency of the remaining frequency sequences and the fundamental frequency satisfy the following relationship:

[0008]

[0009] Among them, f t is the lowest frequency of the remaining frequency sequence, f base is the base frequency in the first frequency sequence, m is the frequency sequence number, n is a positive integer, and c is the total number of frequency sequences;

[0010] Based on the c frequency sequences, a multi-sequence combination wave with consistent frequency density in the entire frequency band is obtained.

[0011] In some embodiments, obtaining a multi-sequence combination wave with consistent frequency density in the entire frequency band based on the c frequency sequences includes:

[0012] Based on the frequency sequence, a corresponding time series matrix is ​​generated for each frequency sequence using a square wave generating function;

[0013] All time series matrices are superimposed and summed, and the amplitude of the sum is corrected: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, so as to obtain a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0.

[0014] In some embodiments, all time series matrices are superimposed and summed, and the result of the sum is amended to an amplitude: an amplitude greater than 0 is amended to A, and an amplitude less than 0 is amended to -A, thereby obtaining a multi-sequence combination wave with consistent frequency density in the entire frequency band, wherein A≠0 includes:

[0015] Performing phase adjustment on at least one of all the time series matrices, finding the phase with the smallest mean square relative error of the amplitude corresponding to each main frequency in the multi-series combination wave with consistent frequency density in the full frequency band obtained after superposition, as the optimal phase of the corresponding time series matrix;

[0016] According to the optimal phase, all time series matrices are superimposed and summed, and the amplitude of the sum is corrected: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, thereby obtaining a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0.

[0017] In some embodiments, the method further includes: replacing the frequency values ​​in each frequency sequence that belong to a preset range with corresponding values ​​in the preset frequency sequence obtained by calculating the aforementioned frequencies.

[0018] In some embodiments, the sampling rate corresponding to each of the time series matrices is at least twice its highest main frequency and is evenly divisible by 4 times the fundamental frequency.

[0019] In a second aspect, an embodiment of the present invention provides a multi-sequence combination wave construction system, comprising:

[0020] A frequency sequence confirmation module is used to determine c frequency sequences according to the depth range to be detected and the required vertical resolution, wherein the frequency sequence is a geometric frequency sequence with a common ratio of 2, and c is a positive integer greater than or equal to 2;

[0021] And, the lowest frequency in the first frequency sequence is recorded as the fundamental frequency f base , the lowest frequency of the remaining frequency sequences and the fundamental frequency satisfy the following relationship:

[0022]

[0023] Among them, f t is the lowest frequency of the remaining frequency sequence, f baseis the base frequency in the first frequency sequence, m is the frequency sequence number, n is a positive integer, and c is the total number of frequency sequences;

[0024] The multi-sequence combination wave construction module obtains a multi-sequence combination wave with consistent frequency density in the entire frequency band based on the c frequency sequences.

[0025] In some embodiments, the multi-sequence combination wave construction module includes:

[0026] A time series matrix generation component, based on the frequency sequence, generates a corresponding time series matrix for each frequency sequence using a square wave generation function;

[0027] The multi-sequence combination wave construction component is used to superimpose and sum all time series matrices, and perform amplitude correction on the sum result: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, so as to obtain a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0.

[0028] In some embodiments, it also includes:

[0029] The frequency replacement module is used to replace the frequency values ​​in each frequency sequence that belong to the preset range with the corresponding values ​​in the preset frequency sequence obtained according to the above-mentioned frequency calculation.

[0030] In some embodiments, the sampling rate corresponding to each of the time series matrices is at least twice its highest main frequency and is evenly divisible by 4 times the fundamental frequency.

[0031] In a third aspect, an embodiment of the present invention provides a multi-sequence combination wave transmitter, which uses the multi-sequence combination wave construction method of the first aspect to construct a multi-sequence combination wave.

[0032] The invention provides a method, system and transmitter for constructing a multi-sequence combination wave. Compared with the prior art, the invention has the following technical effects:

[0033] 1. According to the exploration requirements, increase the number of main frequencies within a limited frequency band to increase the density between the main frequencies, which helps to improve the resolution during electromagnetic exploration.

[0034] 2. Determine the highest and lowest frequencies according to the depth range to be detected, determine the number c of frequency sequences according to the required vertical resolution, and control the relationship between the lowest frequency of the remaining frequency sequences and the fundamental frequency in the first frequency sequence. This can not only improve the required vertical resolution of exploration, but also increase the frequency density of the low-frequency band, that is, obtain a multi-sequence combination wave with consistent frequency density in the entire frequency band, so that the resolution of the acquired deep exploration data is higher, thereby meeting the exploration needs. The relationship between the lowest frequency of the remaining frequency sequences and the fundamental frequency in the first frequency sequence is as follows:

[0035]

[0036] Among them, f t is the lowest frequency of the remaining frequency sequence, f base is the base frequency in the first frequency sequence, m is the frequency sequence number, n is a positive integer, and c is the total number of frequency sequences. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of waveform and spectrum of a pseudo-random wave of order 39 and main frequency 0.25 Hz to 3072 Hz in an embodiment of the present invention;

[0038] Figure 2 A flow chart of a method for constructing a multi-sequence combination wave according to an embodiment of the present invention;

[0039] Figure 3 is a method flow chart of step S14;

[0040] Figure 4 A schematic diagram of the waveform and spectrum of a multi-sequence combination wave according to an embodiment of the present invention;

[0041] Figure 5 A flow chart of another method for constructing multi-sequence combination waves according to an embodiment of the present invention;

[0042] Figure 6 A schematic diagram of the structure of a multi-sequence combination wave construction system according to an embodiment of the present invention;

[0043] Figure 7 It is a structural schematic diagram of the multi-sequence combination wave construction module 34 of an embodiment of the present invention;

[0044] Figure 8 This is a schematic diagram of the structure of another multi-sequence combination wave construction system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, other solutions obtained by ordinary technicians in this field without creative work should belong to the protection scope of the present invention.

[0046] In order to facilitate those skilled in the art to understand the embodiments of the present invention, the technical terms involved in the present invention are explained below.

[0047] Example 1

[0048] Generally, the determination of pseudo-random frequency sequence is to construct two or more basic unit signals according to the exploration requirements, where the lowest frequency of the main frequency in the first basic unit signal is recorded as the base frequency, and the lowest frequency of the remaining basic units is l×2 times the base frequency. p times, where l is an odd number not equal to 1, and p is a natural number.

[0049] For time-frequency transformation, the minimum data analysis length L min =Fs×t min , minimum data analysis time t min =1 / f base , where Fs is the sampling rate, f base is the base frequency, and the frequency resolution is △f=Fs / L min =f base , so to extract each frequency, l must be an odd number not equal to 1, and p is a natural number.

[0050] For commonly used pseudo-random sequences, l takes values ​​of 1, 3, 5, and 7, then the pseudo-random frequency sequence F1 = 1×f base ×2 p , F2=3×f base ×2 p , F3=5×f base ×2 p , F4=7×f base ×2 p , where p is a natural number. Combine the above pseudo-random frequency sequences and arrange them from low to high in frequency. The frequencies of the first few items are f base ×2 0 、f base ×2 1 , 3×f base ×2 0 、f base ×2 2 , 5×f base ×2 0 , 3×f base ×2 1 , 7×f base ×2 0 、f base ×2 3 , it can be seen that no matter what combination is used, the second lowest frequency is twice the lowest frequency, and 1×f base ×2 p For the main sequence, the numbers of frequencies with a frequency interval of 2 times the main sequence frequency are 0, 1, 3, 3, ..., that is, the frequency density of the low-frequency segment is lower.

[0051] like Figure 1As shown, L3 represents the third order, that is, a high-order pseudo-random wave formed by the combination of three sequences, F39 means that the pseudo-random wave contains 39 main frequencies, and 0.25Hz~3072Hz means that the main frequency range of the pseudo-random wave is 0.25Hz~3072Hz, where, Figure 1 (a) shows the change of pseudo-random wave over time, the horizontal axis represents time, the vertical axis represents unit amplitude, and the value is 1 or -1; Figure 1 (b) shows the frequency spectrum curve of the pseudo-random wave. The frequency circled by the box is the frequency designed during construction. From the frequency range of 0.25-0.75 Hz marked by the curly brackets in the figure, it can be seen that the density of the low-frequency range of 0.25-0.75 Hz is relatively low, significantly lower than other frequency ranges.

[0052] The low-frequency band determines the accuracy of deep exploration data. In order to obtain high-resolution deep exploration data, the general method is to increase the frequency points in the low-frequency band, but there will be the following problems:

[0053] 1. As in the 39-frequency wave mentioned above, the frequencies are encrypted between 0.25 and 0.5 Hz, such as 0.3125, 0.375, 0.4375, but these frequencies are not l×2 of the base frequency 0.25 Hz. p times, making subsequent construction steps impossible;

[0054] 2. According to the minimum data analysis length L min When the data is transformed into a time-frequency domain and the frequency domain result is obtained, the encrypted frequency data cannot be extracted because its frequency resolution is 0.25 of the base frequency. In this case, the analysis time can only be increased to 4 times L min At this time, the frequency resolution is one-fourth of the base frequency, that is, 0.0625. Only then can the encrypted frequency be completely extracted. At this time, there will be a mismatch between the base frequency and the actual analysis time, which often leads to errors in data processing.

[0055] From the above analysis, it can be seen that the existing methods cannot improve the resolution of deep exploration data. In order to solve this problem, this embodiment provides the following Figure 2 A multi-sequence combination wave construction method is shown, comprising steps S12 to S14.

[0056] S12. Determine c frequency sequences according to the depth range to be detected and the required vertical resolution, wherein the frequency sequence is a geometric frequency sequence with a common ratio of 2, and c is a positive integer greater than or equal to 2.

[0057] At present, the maximum detection depth of wide-area electromagnetic method is about 7km. Since the inversion algorithm of the electromagnetic method adopts a peeling method from the surface to the inside, shallow information is also very important. Therefore, when detecting, the highest frequency is generally defined as the highest frequency that the instrument can transmit and receive, which is generally 9600Hz. Of course, the determination of the highest and lowest frequencies of electromagnetic waves is ultimately determined by actual detection needs.

[0058] Preferably, the depth range to be detected is first determined, and then the two end values ​​of the depth range to be detected are substituted into the electromagnetic exploration depth H formula to obtain the highest frequency and the lowest frequency of the electromagnetic wave. The electromagnetic exploration depth H formula is:

[0059]

[0060] Where H is the detection depth, ρ is the background resistivity of the exploration area, and f is the exploration electromagnetic wave frequency.

[0061] The background resistivity ρ can be learned by collecting previous geophysical, geological or logging data in the exploration area. The maximum and minimum frequencies of the required electromagnetic waves are calculated according to the depth range to be detected through the above formula. In order to ensure the exploration depth, the minimum frequency in actual operation should be several frequency points lower than the theoretically calculated minimum frequency. Preferably, half of the theoretical value of the minimum frequency is selected.

[0062] In actual exploration, the vertical resolution can be determined according to the scale of the exploration target. Preferably, the vertical resolution is determined according to the diameter-to-depth ratio of the target to be detected, where the diameter-to-depth ratio is the ratio of the vertical thickness of the target to be detected to the burial depth. Preferably, since the vertical resolution limit of electromagnetic exploration is about 10%, the calculated vertical resolution less than 10% is calculated as 10%.

[0063] Determine c frequency sequences according to the highest frequency, the lowest frequency and the longitudinal resolution, wherein the frequency sequence is a geometric frequency sequence with a common ratio of 2, and c is a positive integer greater than or equal to 2.

[0064] And, the lowest frequency in the first frequency sequence is recorded as the fundamental frequency f base , the lowest frequency of the remaining frequency sequences and the fundamental frequency satisfy the following relationship:

[0065]

[0066] Among them, f t is the lowest frequency of the remaining frequency sequence, f base is the base frequency in the first frequency sequence, m is the frequency sequence number, i.e., it represents the mth frequency sequence, n is a positive integer, and c is the total number of frequency sequences.

[0067] Therefore, each frequency sequence is expressed as follows:

[0068]

[0069] Where m is the frequency sequence number and is a positive integer. m is the mth frequency sequence, a is the frequency sequence coefficient greater than or equal to 1, n is a positive integer, f base is the fundamental frequency in the first frequency sequence, c is the total number of frequency sequences, and p is a natural number.

[0070] The fundamental frequency of the multi-sequence combination wave generated by the above frequency sequence combination is:

[0071]

[0072] Among them, fx is the fundamental frequency of the multi-sequence combination wave, n is a positive integer, and c is the total number of frequency sequences.

[0073] For example, when the vertical resolution required for exploration is relatively low, two frequency sequences are determined to generate a multi-sequence combination wave. In this case, c = 2, n = 1, and f t =3 / 2×f base , we can further know that the first frequency sequence can be expressed as F1 = a × f base ×2 p , the second frequency sequence can be expressed as F2 = 3 / 2 × a × f base ×2 p , where p is a natural number. The fundamental frequency of the multi-sequence combination wave generated by the combination of the above two frequency sequences is: fx = 1 / 2 × f base ;

[0074] When the vertical resolution required for exploration is relatively high, such as about 10% or even lower than 10%, four frequency sequences are determined to generate multi-sequence combination waves. In this case, c = 4, n = 2, and f t =(m+3) / 4×f base , that is, the lowest frequency of the second frequency sequence is 5 / 4×f base , the lowest frequency of the third frequency sequence is 6 / 4×f base , the lowest frequency of the fourth frequency sequence is 7 / 4×f base , we can further know that the first frequency sequence can be expressed as F1 = a × f base ×2 p , the second frequency sequence can be expressed as F2 = 5 / 4 × a × f base ×2 p , the third frequency sequence can be expressed as F3 = 6 / 4 × a × f base ×2 p , the fourth frequency sequence can be expressed as F4 = 7 / 4 × a × f base ×2p , where p is a natural number. The fundamental frequency of the multi-sequence combination wave generated by the combination of the above four frequency sequences is: fx = 1 / 4 × f base ;

[0075] When the vertical resolution required for exploration is between the above two, it is necessary to determine three frequency sequences for combining and generating multi-sequence combination waves. Since when c = 3 or 4, n = 2, 2 n-1 +1≤c≤2 n Therefore, we first determine 4 frequency sequences, and then select 3 frequency sequences from them to combine and generate multi-sequence combination waves, that is, c = 4, n = 2, f t =(m+3) / 4×f base , that is, the lowest frequency of the second frequency sequence is 5 / 4×f base , the lowest frequency of the third frequency sequence is 6 / 4×f base , the lowest frequency of the fourth frequency sequence is 7 / 4×f base , we can further know that the first frequency sequence can be expressed as F1 = a × f base ×2 p , the second frequency sequence can be expressed as F2 = 5 / 4 × a × f base ×2 p , the third frequency sequence can be expressed as F3 = 6 / 4 × a × f base ×2 p , the fourth frequency sequence can be expressed as F4 = 7 / 4 × a × f base ×2 p , where p is a natural number. Then, from the above four frequency sequences, select any three frequency sequences to combine and generate a multi-sequence combination wave, and its base frequency is also: fx = 1 / 4 × f base ;

[0076] According to the required vertical resolution of exploration, it is necessary to determine c frequency sequences for combining to generate multi-sequence combination waves, and c satisfies n=3, 2 n-1 +1≤c≤2 n When the conditions are met, first determine 2 n frequency sequences, n = 3, that is, first determine 8 frequency sequences, if c is less than 8, then select c frequency sequences from the 8 frequency sequences to combine and generate multi-sequence combination waves, and their fundamental frequencies are all: fx = 1 / 8 × f base .

[0077] From the above, it can be seen that the staff can determine c frequency sequences according to the vertical resolution required for exploration, where c is a positive integer greater than or equal to 2. The determination of other frequency sequence combinations is not much different from the above description and will not be repeated here.

[0078] S14. Based on the c frequency sequences, a multi-sequence combination wave with consistent frequency density in the entire frequency band is obtained.

[0079] like Figure 3 As shown, the specific implementation of step S14 includes the following sub-steps:

[0080] S142. Based on the frequency sequence, generate a corresponding time series matrix for each frequency sequence using a square wave generation function.

[0081] Substitute each frequency sequence obtained above into the following square wave generation function to generate the corresponding square wave matrix, which is also called time series matrix.

[0082]

[0083] Among them, Y is the time series matrix, sq is the square wave generating function, F is the frequency sequence, t i is the i-th sampling time, For phase.

[0084] According to the Nyquist sampling theorem, the sampling rate corresponding to each time series matrix is ​​at least twice the highest main frequency. Considering the response characteristics of the analog circuit filter, the sampling rate should preferably be 2.4 times or more of the highest main frequency, and the sampling rate should be divisible by 4 times the base frequency.

[0085] S144. All time series matrices are superimposed and summed, and the amplitude of the sum is corrected: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, thereby obtaining a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0.

[0086] All the above time series matrices are superimposed and summed, and the amplitude of the sum is corrected: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, so as to obtain a multi-sequence combination wave with consistent density in the entire frequency band, where A≠0.

[0087] Preferably, a phase adjustment is performed on at least one of all the time series matrices to find the phase with the smallest mean square relative error of the amplitude corresponding to each main frequency in the multi-series combination wave with consistent frequency density in the full frequency band obtained after superposition, as the optimal phase of the corresponding time series matrix;

[0088] The multi-sequence combination wave is subjected to a fast Fourier transform to obtain the spectrum of the multi-sequence combination wave, and the amplitude of each main frequency is extracted, and then the mean square relative error of the amplitude is calculated. Preferably, the phase is adjusted by one degree each time.

[0089] Then, according to the optimal phase, all time series matrices are superimposed and summed, and the amplitude of the sum is corrected: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, so as to obtain a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0, making the amplitude of each frequency more average, thereby improving the overall anti-interference ability of the multi-sequence combination wave.

[0090] Preferably, the result of the sum is subjected to amplitude correction: the amplitude greater than 1 is corrected to 1, and the amplitude less than -1 is corrected to -1, thereby obtaining a multi-sequence combination wave with consistent density in the entire frequency band.

[0091] Finally, the amplitude -1 or -A is corrected to 0, and A is corrected to 1, so that the multi-sequence combination wave consists of only 0 and 1.

[0092] For example, when the frequency sequence coefficient a = 1, and four frequency sequences are determined according to the required vertical resolution for exploration to generate a multi-sequence combination wave, that is, c = 4, n = 2, f t =(m+3) / 4×f base , that is, the lowest frequency of the second frequency sequence is 5 / 4×f base , the lowest frequency of the third frequency sequence is 6 / 4×f base , the lowest frequency of the fourth frequency sequence is 7 / 4×f base , we can further know that the first frequency sequence can be expressed as F1 = 1 × f base ×2 p , the second frequency sequence can be expressed as F2 = 5 / 4 × f base ×2 p , the third frequency sequence can be expressed as F3 = 6 / 4 × f base ×2 p , the fourth frequency sequence can be expressed as F4 = 7 / 4 × f base ×2 p , where p is a natural number.

[0093] After the combination, the low frequency band frequency from low to high is 1×f base ×2 0 , 5 / 4×f base ×2 0 , 6 / 4×f base ×2 0 , 7 / 4×f base ×2 0 , 1×f base ×2 1 , 5 / 4×f base ×2 1 , 6 / 4×f base ×2 1 , 7 / 4×f base ×21 ..., for 1×f base ×2 p For the main sequence, the number of frequencies between the frequency differences of 2 times the main sequence is 3, and the frequency density from low frequency to high frequency is consistent, such as Figure 4 ,in Figure 4 (a) is a schematic diagram of the waveform of the multi-sequence combination wave. Figure 4 (b) is a schematic diagram of the spectrum of multi-sequence combination waves.

[0094] From the above analysis, it can be seen that the frequency density of the multi-sequence combination wave generated by combining c frequency sequences in this embodiment is c. Figure 1 and Figure 4 By comparison, it can be seen that the frequency density of the multi-sequence combination wave generated by this embodiment in the frequency range below 1 Hz is significantly greater than the density of the traditional pseudo-random wave.

[0095] This embodiment determines the highest and lowest frequencies according to the depth range to be detected, determines the number c of frequency sequences according to the required vertical resolution, and controls the relationship between the lowest frequency of the remaining frequency sequences and the fundamental frequency in the first frequency sequence. This not only improves the required vertical resolution of exploration, but also increases the frequency density of the low-frequency band, that is, obtains a multi-sequence combination wave with consistent frequency density in the entire frequency band, so that the resolution of the acquired deep exploration data is higher, thereby meeting the exploration needs.

[0096] Example 2

[0097] like Figure 5 As shown, based on the above embodiment, the multi-sequence combination wave construction method of this embodiment also includes the following steps:

[0098] S13: Replace the frequency values ​​in each frequency sequence that belong to the preset range with corresponding values ​​in the preset frequency sequence obtained according to the above-mentioned frequency calculation.

[0099] According to exploration experience and the spectral characteristics of the power frequency and its harmonics, the preset range is defined as 50n±w Hz, that is, the frequency values ​​in each frequency sequence that belong to the range of 50n±w Hz are replaced by the corresponding values ​​in the preset frequency sequence calculated according to the aforementioned frequency, wherein n is a positive integer, and w is a number less than 10, preferably w=4, at which time more frequencies can be selected, so that the multi-sequence combination wave generated by the combination has both high density and strong anti-interference ability.

[0100] Preferably, the preset frequency sequence is selected from frequency sequences satisfying the following formula, that is, at least one is selected therefrom.

[0101]

[0102] Where m is the frequency sequence number and is a positive integer.m is the mth frequency sequence, a is the frequency sequence coefficient greater than or equal to 1, n is a positive integer, f base is the fundamental frequency in the first frequency sequence, c is the total number of frequency sequences, and p is a natural number.

[0103] And we found that all frequencies of some frequency sequences do not fall within the range of 50n±w Hz, so these frequency sequences are preferably selected as preset frequency sequences. For example, among the commonly used frequency sequences, 4096 and 2048 Hz in frequency sequence F1 fall within the influence range of 50n±w Hz; 96 and 48 Hz in frequency sequence F3 fall within the influence range of 50n±w Hz; 896 and 448 Hz in frequency sequence F4 fall within the influence range of 50n±w Hz; and all frequencies of frequency sequence F2 completely avoid the influence range of 50n±w Hz. Therefore, preferably, frequency sequence F2 is selected as the preset frequency sequence.

[0104] To perform frequency replacement, first find the frequency value in each frequency sequence that falls within the preset range, denoted as f g .

[0105] Perform the following operations on each frequency F in turn:

[0106] If rem(F / 50)>25, then f=50-rem(F / 50), otherwise f=rem(F / 50)

[0107] If f≤w, then f g =F, and then calculate P in the frequency sequence formula by the following formula

[0108]

[0109] Then substitute the above-obtained P into the preset frequency sequence F i The formula is calculated to be the same as f g Similar f i , then f g Replace with f i .

[0110]

[0111] In the above formula, F is a frequency value selected from each frequency sequence each time, rem is the remainder operation, f is a temporary variable, w is w in the above preset range, and f gis the frequency value that falls into the influence range of 50n±w Hz, p is the p in the frequency sequence formula, that is, a natural number, ceil is the rounding operation, c is the c in the frequency sequence formula, that is, the total number of frequency sequences, n is the n in the frequency sequence, which is a positive integer, a is the frequency sequence coefficient a greater than or equal to 1 in the frequency sequence, and f base is the base frequency, i is the frequency sequence number, f i is a temporary variable, which is one of the preset frequency sequences and f g Similar frequencies.

[0112] Through the above calculation, each frequency in each frequency sequence is first judged whether it belongs to the frequency value of the preset range. If it does, it is replaced by the corresponding value in the preset frequency sequence calculated according to the frequency. That is to say, through the above method, all frequency values ​​that are easily interfered with and will cause poor exploration data quality within the preset range are replaced with frequency values ​​with strong anti-interference and enhanced exploration data quality, so that the final multi-sequence combination wave has the advantages of high frequency density in the low frequency band and strong anti-interference, thereby avoiding the influence of the preset range frequency, improving the overall exploration data quality, and meeting higher exploration needs.

[0113] For example, when conducting exploration in thick coverage areas, the effective exploration signal is weak. Combined with the empirical formula of the frequency division coefficient and the waveform, since the frequency resolution of the four frequency sequences will be higher, but the signal strength will be weaker, resulting in weaker anti-interference ability, we generally use three frequency sequences for exploration, so that the obtained multi-sequence combination wave can take into account both strong anti-interference ability and high frequency resolution. Therefore, frequency sequence F2 is preferentially selected as the preset frequency sequence, and frequency sequences F1, F3 and F4 are selected to combine and generate multi-sequence combination waves.

[0114] Example 3

[0115] Figure 6 The schematic diagram of the structure of the multi-sequence combination wave construction system according to the embodiment of the present invention is shown. Figure 6 It can be seen that the multi-sequence combination wave construction system includes: a frequency sequence confirmation module 32 and a multi-sequence combination wave construction module 34;

[0116] The frequency sequence confirmation module 32 is used to determine c frequency sequences according to the depth range to be detected and the required longitudinal resolution, wherein the frequency sequence is a geometric frequency sequence with a common ratio of 2, and c is a positive integer greater than or equal to 2;

[0117] At present, the maximum detection depth of wide-area electromagnetic method is about 7km. Since the inversion algorithm of the electromagnetic method adopts a peeling method from the surface to the inside, shallow information is also very important. Therefore, when detecting, the highest frequency is generally defined as the highest frequency that the instrument can transmit and receive, which is generally 9600Hz. Of course, the determination of the highest and lowest frequencies of electromagnetic waves is ultimately determined by actual detection needs.

[0118] Preferably, the depth range to be detected is first determined, and then the two end values ​​of the depth range to be detected are substituted into the electromagnetic exploration depth H formula to obtain the highest frequency and the lowest frequency of the electromagnetic wave. The electromagnetic exploration depth H formula is:

[0119]

[0120] Where H is the detection depth, ρ is the background resistivity of the exploration area, and f is the exploration electromagnetic wave frequency.

[0121] The background resistivity ρ can be learned by collecting previous geophysical, geological or logging data in the exploration area. The maximum and minimum frequencies of the required electromagnetic waves are calculated according to the depth range to be detected through the above formula. In order to ensure the exploration depth, the minimum frequency in actual operation should be several frequency points lower than the theoretically calculated minimum frequency. Preferably, half of the theoretical value of the minimum frequency is selected.

[0122] In actual exploration, the vertical resolution can be determined according to the scale of the exploration target. Preferably, the vertical resolution is determined according to the diameter-to-depth ratio of the target to be detected, where the diameter-to-depth ratio is the ratio of the vertical thickness of the target to be detected to the burial depth. Preferably, since the vertical resolution limit of electromagnetic exploration is about 10%, the calculated vertical resolution less than 10% is calculated as 10%.

[0123] Determine c frequency sequences according to the highest frequency, the lowest frequency and the longitudinal resolution, wherein the frequency sequence is a geometric frequency sequence with a common ratio of 2, and c is a positive integer greater than or equal to 2.

[0124] And, the lowest frequency in the first frequency sequence is recorded as the fundamental frequency f base , the lowest frequency of the remaining frequency sequences and the fundamental frequency satisfy the following relationship:

[0125]

[0126] Among them, f t is the lowest frequency of the remaining frequency sequence, f base is the base frequency in the first frequency sequence, m is the frequency sequence number, i.e., it represents the mth frequency sequence, n is a positive integer, and c is the total number of frequency sequences.

[0127] Therefore, each frequency sequence is expressed as follows:

[0128]

[0129] Where m is the frequency sequence number and is a positive integer. m is the mth frequency sequence, a is the frequency sequence coefficient greater than or equal to 1, n is a positive integer, f base is the fundamental frequency in the first frequency sequence, c is the total number of frequency sequences, and p is a natural number.

[0130] The fundamental frequency of the multi-sequence combination wave generated by the above frequency sequence combination is:

[0131]

[0132] Among them, fx is the fundamental frequency of the multi-sequence combination wave, n is a positive integer, and c is the total number of frequency sequences.

[0133] For example, when the vertical resolution required for exploration is relatively low, two frequency sequences are determined to generate a multi-sequence combination wave. In this case, c = 2, n = 1, and f t =3 / 2×f base , we can further know that the first frequency sequence can be expressed as F1 = a × f base ×2 p , the second frequency sequence can be expressed as F2 = 3 / 2 × a × f base ×2 p , where p is a natural number. The fundamental frequency of the multi-sequence combination wave generated by the combination of the above two frequency sequences is: fx = 1 / 2 × f base ;

[0134] When the vertical resolution required for exploration is relatively high, such as about 10% or even lower than 10%, four frequency sequences are determined to generate multi-sequence combination waves. In this case, c = 4, n = 2, and f t =(m+3) / 4×f base , that is, the lowest frequency of the second frequency sequence is 5 / 4×f base , the lowest frequency of the third frequency sequence is 6 / 4×f base , the lowest frequency of the fourth frequency sequence is 7 / 4×f base , we can further know that the first frequency sequence can be expressed as F1 = a × f base ×2 p , the second frequency sequence can be expressed as F2 = 5 / 4 × a × f base ×2 p , the third frequency sequence can be expressed as F3 = 6 / 4 × a × f base ×2 p , the fourth frequency sequence can be expressed as F4 = 7 / 4 × a × f base ×2p , where p is a natural number. The fundamental frequency of the multi-sequence combination wave generated by the combination of the above four frequency sequences is: fx = 1 / 4 × f base ;

[0135] When the vertical resolution required for exploration is between the above two, it is necessary to determine three frequency sequences for combining and generating multi-sequence combination waves. Since when c = 3 or 4, n = 2, 2 n-1 +1≤c≤2 n Therefore, we first determine 4 frequency sequences, and then select 3 frequency sequences from them to combine and generate multi-sequence combination waves, that is, c = 4, n = 2, f t =(m+3) / 4×f base , that is, the lowest frequency of the second frequency sequence is 5 / 4×f base , the lowest frequency of the third frequency sequence is 6 / 4×f base , the lowest frequency of the fourth frequency sequence is 7 / 4×f base , we can further know that the first frequency sequence can be expressed as F1 = a × f base ×2 p , the second frequency sequence can be expressed as F2 = 5 / 4 × a × f base ×2 p , the third frequency sequence can be expressed as F3 = 6 / 4 × a × f base ×2 p , the fourth frequency sequence can be expressed as F4 = 7 / 4 × a × f base ×2 p , where p is a natural number. Then, from the above four frequency sequences, select any three frequency sequences to combine and generate a multi-sequence combination wave, and its base frequency is also: fx = 1 / 4 × f base ;

[0136] According to the required vertical resolution of exploration, it is necessary to determine c frequency sequences for combining to generate multi-sequence combination waves, and c satisfies n=3, 2 n-1 +1≤c≤2 n When the conditions are met, first determine 2 n frequency sequences, n = 3, that is, first determine 8 frequency sequences, if c is less than 8, then select c frequency sequences from the 8 frequency sequences to combine and generate multi-sequence combination waves, and their fundamental frequencies are all: fx = 1 / 8 × f base .

[0137] From the above, it can be seen that the staff can determine c frequency sequences according to the vertical resolution required for exploration, where c is a positive integer greater than or equal to 2. The determination of other frequency sequence combinations is not much different from the above description and will not be repeated here.

[0138] The multi-sequence combination wave construction module 34 obtains a multi-sequence combination wave with consistent frequency density in the entire frequency band based on the c frequency sequences.

[0139] like Figure 7 As shown, the multi-sequence combination wave construction module 34 includes: a time series matrix generation component 342 and a multi-sequence combination wave construction component 344.

[0140] The time series matrix generating component 342 generates a corresponding time series matrix for each frequency sequence using a square wave generating function based on the frequency sequence.

[0141] Substitute each frequency sequence obtained above into the following square wave generation function to generate the corresponding square wave matrix, which is also called time series matrix.

[0142]

[0143] Among them, Y is the time series matrix, sq is the square wave generating function, F is the frequency sequence, t i is the i-th sampling time, For phase.

[0144] According to the Nyquist sampling theorem, the sampling rate corresponding to each time series matrix is ​​at least twice the highest main frequency. Considering the response characteristics of the analog circuit filter, the sampling rate should preferably be 2.4 times or more of the highest main frequency, and the sampling rate should be divisible by 4 times the base frequency.

[0145] The multi-sequence combination wave construction component 344 is used to superimpose and sum all time series matrices, and perform amplitude correction on the sum result: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, so as to obtain a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0.

[0146] All the above time series matrices are superimposed and summed, and the amplitude of the sum is corrected: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, so as to obtain a multi-sequence combination wave with consistent density in the entire frequency band, where A≠0.

[0147] Preferably, a phase adjustment is performed on at least one of all the time series matrices to find the phase with the smallest mean square relative error of the amplitude corresponding to each main frequency in the multi-series combination wave with consistent frequency density in the full frequency band obtained after superposition, as the optimal phase of the corresponding time series matrix;

[0148] The multi-sequence combination wave is subjected to a fast Fourier transform to obtain the spectrum of the multi-sequence combination wave, and the amplitude of each main frequency is extracted, and then the mean square relative error of the amplitude is calculated. Preferably, the phase is adjusted by one degree each time.

[0149] Then, according to the optimal phase, all time series matrices are superimposed and summed, and the amplitude of the sum is corrected: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, so as to obtain a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0, making the amplitude of each frequency more average, thereby improving the overall anti-interference ability of the multi-sequence combination wave.

[0150] Preferably, the result of the sum is subjected to amplitude correction: the amplitude greater than 1 is corrected to 1, and the amplitude less than -1 is corrected to -1, thereby obtaining a multi-sequence combination wave with consistent density in the entire frequency band.

[0151] Finally, the amplitude -1 or -A is corrected to 0, and A is corrected to 1, so that the multi-sequence combination wave consists of only 0 and 1.

[0152] For example, when the frequency sequence coefficient a = 1, and four frequency sequences are determined according to the required vertical resolution for exploration to generate a multi-sequence combination wave, that is, c = 4, n = 2, f t =(m+3) / 4×f base , that is, the lowest frequency of the second frequency sequence is 5 / 4×f base , the lowest frequency of the third frequency sequence is 6 / 4×f base , the lowest frequency of the fourth frequency sequence is 7 / 4×f base , we can further know that the first frequency sequence can be expressed as F1 = 1 × f base ×2 p , the second frequency sequence can be expressed as F2 = 5 / 4 × f base ×2 p , the third frequency sequence can be expressed as F3 = 6 / 4 × f base ×2 p , the fourth frequency sequence can be expressed as F4 = 7 / 4 × f base ×2 p , where p is a natural number.

[0153] After the combination, the low frequency band frequency from low to high is 1×f base ×2 0 , 5 / 4×f base ×2 0 , 6 / 4×f base ×2 0 , 7 / 4×f base ×2 0 , 1×f base ×2 1 , 5 / 4×f base ×2 1 , 6 / 4×f base ×2 1 , 7 / 4×fbase ×2 1 ..., for 1×f base ×2 p For the main sequence, the number of frequencies between the frequency differences of 2 times the main sequence is 3, and the frequency density from low frequency to high frequency is consistent, such as Figure 4 ,in Figure 4 (a) is a schematic diagram of the waveform of the multi-sequence combination wave. Figure 4 (b) is a schematic diagram of the spectrum of multi-sequence combination waves.

[0154] From the above analysis, it can be seen that the frequency density of the multi-sequence combination wave generated by combining c frequency sequences in this embodiment is c. Figure 1 and Figure 4 By comparison, it can be seen that the frequency density of the multi-sequence combination wave generated by this embodiment in the frequency range below 1 Hz is significantly greater than the density of the traditional pseudo-random wave.

[0155] This embodiment determines the highest and lowest frequencies according to the depth range to be detected, determines the number c of frequency sequences according to the required vertical resolution, and controls the relationship between the lowest frequency of the remaining frequency sequences and the fundamental frequency in the first frequency sequence. This not only improves the required vertical resolution of exploration, but also increases the frequency density of the low-frequency band, that is, obtains a multi-sequence combination wave with consistent frequency density in the entire frequency band, so that the resolution of the acquired deep exploration data is higher, thereby meeting the exploration needs.

[0156] Example 4

[0157] like Figure 8 As shown, based on the above embodiment, the multi-sequence combination wave construction system of this embodiment further includes:

[0158] The frequency replacement module 33 is used to replace the frequency values ​​in each frequency sequence that belong to the preset range with the corresponding values ​​in the preset frequency sequence obtained according to the above-mentioned frequency calculation.

[0159] According to exploration experience and the spectral characteristics of the power frequency and its harmonics, the preset range is defined as 50n±w Hz, that is, the frequency values ​​in each frequency sequence that belong to the range of 50n±w Hz are replaced by the corresponding values ​​in the preset frequency sequence calculated according to the aforementioned frequency, wherein n is a positive integer, and w is a number less than 10, preferably w=4, at which time more frequencies can be selected, so that the multi-sequence combination wave generated by the combination has both high density and strong anti-interference ability.

[0160] Preferably, the preset frequency sequence is selected from frequency sequences satisfying the following formula, that is, at least one is selected therefrom.

[0161]

[0162] Where m is the frequency sequence number and is a positive integer. m is the mth frequency sequence, a is the frequency sequence coefficient greater than or equal to 1, n is a positive integer, f base is the fundamental frequency in the first frequency sequence, c is the total number of frequency sequences, and p is a natural number.

[0163] And we found that all frequencies of some frequency sequences do not fall within the range of 50n±w Hz, so these frequency sequences are preferably selected as preset frequency sequences. For example, among the commonly used frequency sequences, 4096 and 2048 Hz in frequency sequence F1 fall within the influence range of 50n±w Hz; 96 and 48 Hz in frequency sequence F3 fall within the influence range of 50n±w Hz; 896 and 448 Hz in frequency sequence F4 fall within the influence range of 50n±w Hz; and all frequencies of frequency sequence F2 completely avoid the influence range of 50n±w Hz. Therefore, preferably, frequency sequence F2 is selected as the preset frequency sequence.

[0164] To perform frequency replacement, first find the frequency value in each frequency sequence that falls within the preset range, denoted as f g .

[0165] Perform the following operations on each frequency F in turn:

[0166] If rem(F / 50)>25, then f=50-rem(F / 50), otherwise f=rem(F / 50)

[0167] If f≤w, then f g =F, and then calculate P in the frequency sequence formula by the following formula

[0168]

[0169] Then substitute the above-obtained P into the preset frequency sequence F i The formula is calculated to be the same as f g Similar f i , then f g Replace with f i .

[0170]

[0171] In the above formula, F is a frequency value selected from each frequency sequence each time, rem is the remainder operation, f is a temporary variable, w is w in the above preset range, and f gis the frequency value that falls into the influence range of 50n±w Hz, p is the p in the frequency sequence formula, that is, a natural number, ceil is the rounding operation, c is the c in the frequency sequence formula, that is, the total number of frequency sequences, n is the n in the frequency sequence, which is a positive integer, a is the frequency sequence coefficient a greater than or equal to 1 in the frequency sequence, and f base is the base frequency, i is the frequency sequence number, f i is a temporary variable, which is one of the preset frequency sequences and f g Similar frequencies.

[0172] Through the above calculation, each frequency in each frequency sequence is first judged whether it belongs to the frequency value of the preset range. If it does, it is replaced by the corresponding value in the preset frequency sequence calculated according to the frequency. That is to say, through the above method, all frequency values ​​that are easily interfered with and will cause poor exploration data quality within the preset range are replaced with frequency values ​​with strong anti-interference and enhanced exploration data quality, so that the final multi-sequence combination wave has the advantages of high frequency density in the low frequency band and strong anti-interference, thereby avoiding the influence of the preset range frequency, improving the overall exploration data quality, and meeting higher exploration needs.

[0173] For example, when conducting exploration in thick coverage areas, the effective exploration signal is weak. Combined with the empirical formula of the frequency division coefficient and the waveform, since the frequency resolution of the four frequency sequences will be higher, but the signal strength will be weaker, resulting in weaker anti-interference ability, we generally use three frequency sequences for exploration, so that the obtained multi-sequence combination wave can take into account both strong anti-interference ability and high frequency resolution. Therefore, frequency sequence F2 is preferentially selected as the preset frequency sequence, and frequency sequences F1, F3 and F4 are selected to combine and generate multi-sequence combination waves.

[0174] Example 5

[0175] This embodiment provides a multi-sequence combination wave transmitter, and adopts a multi-sequence combination wave construction method of the embodiment to obtain a multi-sequence combination wave with consistent frequency density in the full frequency band that meets exploration requirements.

[0176] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for constructing a multi-sequence combination wave, characterized in that: The steps include: Determine c frequency sequences according to the depth range to be detected and the required vertical resolution, wherein the frequency sequence is a geometric frequency sequence with a common ratio of 2, and c is a positive integer greater than or equal to 2; And, the lowest frequency in the first frequency sequence is recorded as the fundamental frequency f base , the lowest frequency of the remaining frequency sequences and the fundamental frequency satisfy the following relationship: 2 n-1 +1≤c≤2 n ,1<m≤2 n Among them, f t is the lowest frequency of the remaining frequency sequence, f base is the base frequency in the first frequency sequence, m is the frequency sequence number, n is a positive integer, and c is the total number of frequency sequences; Based on the c frequency sequences, a multi-sequence combination wave with consistent frequency density in the entire frequency band is obtained.

2. The multi-sequence combination wave construction method according to claim 1, characterized in that: The method of obtaining a multi-sequence combination wave with consistent frequency density in the entire frequency band based on the c frequency sequences includes: Based on the frequency sequence, a corresponding time series matrix is ​​generated for each frequency sequence using a square wave generating function; All time series matrices are superimposed and summed, and the amplitude of the sum is corrected: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, so as to obtain a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0.

3. The multi-sequence combination wave construction method according to claim 2, characterized in that: All time series matrices are superimposed and summed, and the result of the sum is amended to an amplitude: the amplitude greater than 0 is amended to A, and the amplitude less than 0 is amended to -A, thereby obtaining a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0 includes: Performing phase adjustment on at least one of all the time series matrices, finding the phase with the smallest mean square relative error of the amplitude corresponding to each main frequency in the multi-series combination wave with consistent frequency density in the full frequency band obtained after superposition, as the optimal phase of the corresponding time series matrix; According to the optimal phase, all time series matrices are superimposed and summed, and the amplitude of the sum is corrected: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, thereby obtaining a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0.

4. The method for constructing a multi-sequence combination wave according to any one of claims 1 to 3, characterized in that: Also includes: The frequency values ​​in each frequency sequence that belong to the preset range are replaced by corresponding values ​​in the preset frequency sequence obtained according to the above frequency calculation.

5. The multi-sequence combination wave construction method according to claim 2 or 3, characterized in that: The sampling rate corresponding to each of the time series matrices is at least twice its highest main frequency and is divisible by 4 times the fundamental frequency.

6. A multi-sequence combination wave construction system, characterized in that: include: A frequency sequence confirmation module is used to determine c frequency sequences according to the depth range to be detected and the required vertical resolution, wherein the frequency sequence is a geometric frequency sequence with a common ratio of 2, and c is a positive integer greater than or equal to 2; And, the lowest frequency in the first frequency sequence is recorded as the fundamental frequency f base , the lowest frequency of the remaining frequency sequences and the fundamental frequency satisfy the following relationship: 2 n-1 +1≤c≤2 n ,1<m≤2 n Among them, f t is the lowest frequency of the remaining frequency sequence, f base is the base frequency in the first frequency sequence, m is the frequency sequence number, n is a positive integer, and c is the total number of frequency sequences; The multi-sequence combination wave construction module obtains a multi-sequence combination wave with consistent frequency density in the entire frequency band based on the c frequency sequences.

7. The multi-sequence combination wave construction system according to claim 6, characterized in that: The multi-sequence combination wave construction module comprises: A time series matrix generation component, based on the frequency sequence, generates a corresponding time series matrix for each frequency sequence using a square wave generation function; The multi-sequence combination wave construction component is used to superimpose and sum all time series matrices, and perform amplitude correction on the sum result: the amplitude greater than 0 is corrected to A, and the amplitude less than 0 is corrected to -A, so as to obtain a multi-sequence combination wave with consistent frequency density in the entire frequency band, where A≠0.

8. The multi-sequence combination wave construction system according to claim 6 or 7, characterized in that: Also includes: The frequency replacement module is used to replace the frequency values ​​in each frequency sequence that belong to the preset range with the corresponding values ​​in the preset frequency sequence obtained according to the above-mentioned frequency calculation.

9. The multi-sequence combination wave construction system according to claim 7, characterized in that: The sampling rate corresponding to each of the time series matrices is at least twice its highest main frequency and is divisible by 4 times the fundamental frequency.

10. A multi-sequence combination wave transmitter, characterized in that: A multi-sequence combination wave constructed by the multi-sequence combination wave construction method described in any one of claims 1-5.

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