WO2021218524A1 - 一种高阶伪随机电磁勘探信号生成方法及系统 - Google Patents

一种高阶伪随机电磁勘探信号生成方法及系统 Download PDF

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WO2021218524A1
WO2021218524A1 PCT/CN2021/083727 CN2021083727W WO2021218524A1 WO 2021218524 A1 WO2021218524 A1 WO 2021218524A1 CN 2021083727 W CN2021083727 W CN 2021083727W WO 2021218524 A1 WO2021218524 A1 WO 2021218524A1
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signal
basic unit
signals
phase
order
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PCT/CN2021/083727
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English (en)
French (fr)
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何继善
杨洋
李帝铨
瓮晶波
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山东大学
香港中文大学（深圳）
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Priority to US17/601,972 priority Critical patent/US11983511B2/en
Publication of WO2021218524A1 publication Critical patent/WO2021218524A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F7/00—Methods or arrangements for processing data by operating upon the order or content of the data handled
    • G06F7/58—Random or pseudo-random number generators
    • G06F7/582—Pseudo-random number generators
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/12—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with electromagnetic waves
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F7/00—Methods or arrangements for processing data by operating upon the order or content of the data handled
    • G06F7/60—Methods or arrangements for performing computations using a digital non-denominational number representation, i.e. number representation without radix; Computing devices using combinations of denominational and non-denominational quantity representations, e.g. using difunction pulse trains, STEELE computers, phase computers
    • G06F7/68—Methods or arrangements for performing computations using a digital non-denominational number representation, i.e. number representation without radix; Computing devices using combinations of denominational and non-denominational quantity representations, e.g. using difunction pulse trains, STEELE computers, phase computers using pulse rate multipliers or dividers pulse rate multipliers or dividers per se

Definitions

  • the invention relates to the field of geophysical prospecting, in particular to a method and system for generating high-order pseudo-random electromagnetic prospecting signals.
  • the present invention provides a high-order pseudo-random electromagnetic prospecting signal generation method and system, which can construct 2n sequence pseudo-random signals of different orders in a limited frequency range, which is compared with traditional 2n sequence pseudo-random signals.
  • the signal has a higher resolution.
  • one or more embodiments of the present invention provide the following technical solutions:
  • a method for generating high-order pseudo-random electromagnetic prospecting signals includes the following steps:
  • the basic unit signal is a step signal obtained by superimposing a plurality of square wave signals with the same phase, and the frequency ratio between adjacent square wave signals Is 2;
  • the two or more basic unit signals are superimposed to obtain a superimposed step signal, and the amplitude is corrected to be consistent with the amplitude of the square wave signal to obtain a high-order 2n sequence pseudo-random signal.
  • One or more embodiments provide a terminal device, including a processor and a computer-readable storage medium, where the processor is used to implement each instruction; the computer-readable storage medium is used to store a plurality of instructions, characterized in that the instructions are suitable for The high-order pseudo-random electromagnetic prospecting signal generation method is loaded and executed by the processor.
  • One or more embodiments provide a computer-readable storage medium in which a plurality of instructions are stored, characterized in that the instructions are adapted to be loaded by a processor of a terminal device and execute the high-order pseudo-random electromagnetic survey Signal generation method.
  • One or more embodiments provide an electrical survey signal transmitter, which adopts the high-order pseudo-random electromagnetic survey signal generation method to generate high-order 2n sequence pseudo-random signals.
  • One or more embodiments provide an electrical prospecting signal transmitter, which uses the high-order pseudo-random electromagnetic prospecting signal generation method to generate high-order 2n sequence pseudo-random signals.
  • the number of dominant frequencies can be increased in a limited frequency range according to the exploration requirements, and 2n sequence step signals of different orders can be constructed in the limited frequency range to increase the density between the dominant frequencies and help improve the The resolution during electromagnetic surveying.
  • High-order pseudo-random signals can be transmitted and received at the same time at dozens of frequencies, and compared with traditional single-frequency or multi-frequency transmission signals, massive data collection can be achieved, which greatly increases the spectral density and enhances the resolution of longitudinal exploration; Under the condition of the same total working time, each frequency can collect data for a longer time, which can better suppress the influence of background noise and improve the anti-interference ability; at the same time, only a set of combined waveforms needs to be transmitted during data collection , Instead of changing the transmitted waveform, multiple receivers can be used for continuous rolling measurement, which fundamentally changes the observation method of conventional artificial source electromagnetic exploration methods, so as to achieve efficient field data acquisition, especially suitable for large-area three-dimensional exploration. Greatly reduce exploration costs. At present, it has been successfully applied to actual exploration work in the field.
  • Fig. 1 is a flowchart of a method for generating high-order pseudo-random electromagnetic prospecting signals in an embodiment of the present invention
  • Figure 2 is a 1Hz periodic sine signal and a 1Hz periodic square wave signal (phase ) Schematic diagram of the corresponding relationship;
  • FIG. 3 is a schematic diagram of step signals after 7 frequencies are superimposed in an embodiment of the present invention.
  • Figure 4 is a step signal (a) and its frequency spectrum diagram (b) after 7 frequencies are superimposed in an embodiment of the present invention
  • Figure 5 is a schematic diagram of a step signal (a) and its frequency spectrum (b) after 6 frequencies are superimposed in an embodiment of the present invention
  • Fig. 6 shows a superimposed signal containing 13 frequency waves and a correspondingly generated pseudo-random signal in an embodiment of the present invention.
  • FIG. 7 is a schematic diagram of time-domain waveform (a) and frequency spectrum (b) of a pseudo-random signal containing 13 frequency waves in an embodiment of the present invention
  • Fig. 9 is the time-domain waveform (a) and spectral characteristics (b) corresponding to the 3Hz-6 frequency-2 ⁇ /5 phase structure unit in the embodiment of the present invention.
  • Fig. 10 shows the time-domain waveform (a) and spectral characteristics (b) of the corresponding pseudo-random signal at 1Hz-7 frequency-0 phase and 3Hz-6 frequency-2 ⁇ /5 phase in the embodiment of the present invention
  • FIG. 11 is a curve of relative mean square error of the main frequency spectrum under different phases of the second structural unit in the embodiment of the present invention.
  • Figure 12 shows the time-domain waveform (a) and spectral characteristics (b) of the pseudo-random signal L2-F21-1Hz-1536Hz generated by the 1Hz-11 frequency-0 phase and 3Hz-10 frequency-67 ⁇ /180 phase construction unit in the embodiment of the present invention );
  • FIG. 13 is a curve of the relative mean square error variation curve of the frequency spectrum amplitude of the main frequency when the phase of the third-order signal construction unit in the embodiment of the present invention changes;
  • Fig. 14 is the waveform (a) and frequency spectrum (b) of the third-order 2n sequence signal (L3-F29-1Hz-1536Hz) in the embodiment of the present invention.
  • Fig. 15 is a fourth-order signal phase change curve in the embodiment of the present invention.
  • Figure 16 shows the waveform (a) and frequency spectrum (b) of the 4th order 2n sequence signal (L3-F29-1Hz-1536Hz) in the embodiment of the present invention
  • FIG. 17 is a curve of relative mean square error of the main frequency spectrum of the 5th order signal with the phase change in the embodiment of the present invention.
  • Figure 18 shows the waveform (a) and frequency spectrum (b) of the 5th order 2n sequence signal (L5-F45-1Hz-1536Hz) in the embodiment of the present invention
  • FIG. 19 is a curve of relative mean square error of the main frequency spectrum of the second-order signal with the phase change in the embodiment of the present invention.
  • Fig. 20 shows the time-domain waveform (a) and frequency spectrum (b) of the corresponding pseudo-random signal at 1Hz-7 frequency- ⁇ /9 phase and 3Hz-6 frequency- ⁇ /9 phase in the embodiment of the present invention
  • Figure 21 is a time-domain waveform (a) and frequency spectrum (b) of a second-order signal (L2-F27-0.25Hz-3072Hz) suitable for shallow exploration in an embodiment of the present invention
  • Fig. 22 is a time-domain waveform (a) and frequency spectrum (b) of a third-order signal (L3-F39-0.25 Hz-3072 Hz) suitable for shallow exploration in an embodiment of the present invention.
  • the embodiment will take a computer simulation signal as an example.
  • the sampling frequency used is much higher than the highest frequency of the pseudo-random signal.
  • the calculation error caused by the discretization of the signal after the computer is introduced can be ignored.
  • This embodiment discloses a method for generating high-order pseudo-random electromagnetic prospecting signals. As shown in FIG. 1, the method includes:
  • Step 1 Construct two or more basic unit signals according to exploration requirements, where the basic unit signals are step signals obtained by superimposing a plurality of periodic square wave signals of the same phase, and the plurality of square wave signals are adjacent to each other.
  • the frequency ratio is 2.
  • the method for generating the periodic square wave is:
  • the value greater than 0 is set to A
  • the value less than 0 is set to -A
  • the position equal to 0 is set to A and -A according to the index parity.
  • all positions of 0 in the index identification signal are set equal to A and -A according to the parity item.
  • -A a series of periodic square wave signals with the same phase are obtained, where A ⁇ 0, and the phase value can be adjusted according to requirements. In this embodiment, the phase is 0.
  • the main frequency range of the periodic square wave is related to the exploration depth, and the minimum and maximum frequencies of the main frequency can be selected according to the depth requirements to be detected (such as deep, shallow or other specific detection depths) and assisted by empirical formulas. Specifically, the depth range to be probed required by the user is obtained; the highest frequency and the lowest frequency are determined according to the depth range to be probed. Then combine the frequency of the acquired demand and increase the multiple to obtain the corresponding frequency of the target periodic square wave.
  • the value greater than 0 is set to 100
  • the value of less than 0 is set to -100
  • the position equal to 0 is set to 100 and -100 according to the position index parity.
  • the signal as shown in Figure 2, can generate all frequencies with a frequency amplitude of 100 and a phase of 0 in this way.
  • R(t) is a periodic square wave signal.
  • the lowest frequency of the periodic square wave is referred to as the fundamental frequency for convenience of presentation, and the fundamental frequency of the signal generated in FIG. 3 is 1 Hz.
  • the superimposed signal here needs to be a 2n sequence frequency, that is, the adjacent square wave frequencies need to be continuously increased by a multiple of 2.
  • other frequencies with 1Hz as the base frequency can be generated, such as 2Hz, 4Hz, 8Hz...64Hz phase
  • the periodic square wave signal at 0, and by superimposing the 0-phase periodic square wave of 1Hz, 2Hz, 4Hz, 8Hz, 16Hz, 32Hz, 64Hz, a step signal with multiple frequencies can be obtained, the superimposed waveform and corresponding frequency spectrum As shown in Figure 4.
  • this step signal is used as the first basic unit signal ,
  • the lowest frequency is 3Hz
  • the number of frequencies in the basic unit is 6, and the structure signal and spectrogram are shown in Figure 5.
  • the 6-cycle square wave frequencies are 3Hz, 6Hz, 12Hz, 24Hz, 48Hz, 96Hz, and the phase is also 0
  • the superimposed ladder signal is used as the second basic unit signal, called 3Hz-6 frequency-0 phase 2n sequence basic unit.
  • the lowest frequency of the basic unit can be changed, and the number of frequencies is not necessarily an odd number, but can be an even number.
  • the lowest frequency of the first basic unit is called the fundamental frequency
  • the lowest frequency of the second basic unit is 3 times the fundamental frequency
  • the lowest frequency of the third basic unit is 5 times the fundamental frequency.
  • the lowest frequency of the four basic units is 7 times the fundamental frequency
  • the lowest frequency of the n-th basic unit is 2n+1 times the fundamental frequency.
  • the number of main frequencies in the first basic unit is a 1
  • the number of main frequencies in the second basic unit a 2 the number of main frequencies in the third basic unit a 3
  • Num f when constructing a high-order 2n sequence pseudo-random signal, Num f must be an odd number, and it is not required whether the number in each basic unit is an odd number. At the same time, under normal circumstances, the number of a 1 should be greater than the dominant frequency of other basic units to constrain the highest frequency in the high-order 2n sequence pseudo-random signal.
  • the number of frequencies in the basic unit can be changed.
  • the basic unit 1Hz-11 frequency-0 phase and the basic unit 3Hz-10 frequency-67 ⁇ /180 phase can be superimposed to construct a second-order 2n sequence pseudo-random signal, as shown in Figure 11.
  • the coding method of the complex 2n sequence pseudo-random signal is L2-F21--1Hz-1536Hz, where L is the abbreviation of Level, which means the order, and F is the abbreviation of Frequency, which means that the signal contains the main frequency Number, 1Hz represents the lowest frequency dominant frequency in the signal, 1536Hz represents the highest frequency dominant frequency in the signal.
  • Different orders represent the degree of density between the main frequencies, 2nd order is denser than 1st order, 3rd order is denser than 2nd order, and so on.
  • this embodiment increases the number of main frequencies within a limited frequency range, and constructs 2n sequence step signals of different orders in the limited frequency range to increase the density between the main frequencies and help improve the electromagnetic exploration. Resolution.
  • Step 2 The two or more basic unit signals are superimposed to obtain a superimposed step signal, and the amplitude is corrected to be consistent with the amplitude of the square wave signal to obtain a high-order 2n sequence pseudo-random signal.
  • the above two basic units are superimposed to obtain a new set of superimposed step signal, and the position amplitude of the superimposed step signal whose amplitude is greater than A is set to A, and the position amplitude of the position whose amplitude is less than -A is set to- A, to obtain a 2n sequence of pseudo-random signals.
  • the red is the superimposed step signal
  • the blue is the pseudo-random signal.
  • the pseudo-random signal waveform and frequency spectrum are shown in Figure 7.
  • the pseudo-random signal obtained by directly adding the two basic units has a large difference in main frequency spectrum energy and is not suitable for electromagnetic prospecting in the frequency domain. Therefore, the superposition method is also optimized.
  • Step 3 Perform phase adjustment on at least one of the two or more basic unit signals, and find the phase that minimizes the mean square error of the spectral amplitudes corresponding to the main frequencies in the superimposed high-order 2n sequence pseudo-random signal, as the corresponding The optimal phase of the basic unit signal; according to the optimal phase, the two or more basic unit signals are superimposed, and the amplitude is corrected to be consistent with the amplitude of the square wave signal to obtain a high-order 2n sequence pseudo-random signal.
  • This embodiment judges the uniformity between the amplitudes by calculating the mean square error of the corresponding frequency spectrum amplitude, and selects the phase with the smallest mean square error data as the optimal phase, so that each main frequency (dominant frequency) corresponds to the frequency spectrum
  • the amplitude is uniform, that is, the main frequency energy distribution is more uniform.
  • the basic unit signal for phase adjustment first split the half-period phase radian ⁇ into N parts (after greater than half the half-period phase radian ⁇ , the signal is reversed, but the overall shape of the signal is the same, so you only need to consider Half cycle phase is enough), that is, the basic unit of phase change is ⁇ /N; each time you adjust one phase change basic unit, record the mean square deviation of the corresponding frequency spectrum value of each main frequency in the superimposed high-order 2n sequence pseudo-random signal; The variation curve of the variance size with the phase, and find the phase with the smallest mean square error as the best phase of the basic unit signal.
  • the phase radians ⁇ of the half cycle is split into ⁇ /180, and the phase changes ⁇ /180 each time, increasing in turn, that is, changing the value of ⁇ in the formula each time .
  • the possible values are 0, ⁇ /180, 2 ⁇ /180, 3 ⁇ /180...179 ⁇ /180.
  • the operation is greater than 100
  • the position is set to a value of 100 and the position less than -100 is set to a value of -100, calculate and record the relative mean square error of the corresponding spectrum values of the 13 main frequencies at this time; change the phase of the second structural unit to ⁇ /180, and change It is 3Hz-6 frequency- ⁇ /180, calculate and record the relative mean square error value of the corresponding spectrum value of 13 main frequencies at this time, and so on to obtain 2 ⁇ /180, 3 ⁇ /180...179 ⁇ /180, corresponding to false under 180 different phases
  • the relative mean square error curve of the random signal is compared to obtain the minimum relative mean square error corresponding to the phase of the second basic unit.
  • the corresponding phase of the unit is 2 ⁇ /5, which is used as the optimal construction method for the pseudo-random signal at these 13 frequencies, that is, the first basic unit has 0 phase, which is 1Hz-7 frequency-0 phase, and the second basic unit has phase 0.
  • the optimal construction method of L2-F13-1Hz-96Hz pseudo-random signal is obtained, as shown in Figure 10.
  • the corresponding phase ⁇ of the first basic unit can be changed.
  • the phases of the two basic units change at the same time.
  • the corresponding phases of the two basic units at the minimum point are ⁇ /9 and 2 ⁇ /9 respectively.
  • the time-domain waveform and frequency spectrum of the corresponding 2n-sequence pseudo-random signal are shown in Figure 20.
  • the minimum value of the relative mean square error of the main frequency spectrum amplitude is obtained, that is, the spectrum components are optimally allocated to 2n sequence pseudo-random signals.
  • the pseudo-random signal number is L3-F29—1Hz-1536Hz, which is a 2n-sequence pseudo-random signal with 3rd-order 29-frequency, lowest primary frequency 1Hz, and highest primary frequency 1536Hz.
  • the three basic units are respectively 1Hz-11 frequency-0 phase, 3Hz-10 frequency- ⁇ /2 phase and 5Hz-8 frequency-9 ⁇ /20 phase, the three basic units obtain the second order 2n of the optimal distribution of the main frequency energy of this frequency band under the corresponding phase conditions Sequence pseudo-random signal, as shown in the spectrogram of Figure 14b.
  • the construction method proposed by the present invention can construct a higher-order signal in a fixed frequency interval, as shown in Fig. 15 and Fig. 16 for the 4th-order 2n sequence pseudo-random signal L4-F37-1Hz-1536Hz, as shown in Fig. 14 and Fig. 15 Shows the 5th order 2n sequence pseudo-random signal L5-F45-1Hz-1536Hz.
  • the frequency range of the high-order 2n sequence pseudo-random signal generated in the present invention can be changed according to the needs of exploration.
  • the lowest frequency of the frequency range is not lower than 0.015625 Hz, and the highest frequency is not higher than 8192 Hz.
  • L2-F27-0.25Hz-3072Hz where the main frequency is 0.25Hz, the phase of the structural unit is 10 degrees, and the main frequency is 0.75Hz, the phase of the structural unit 120 degrees; and, L3-F39-0.25Hz-3072Hz, where the main frequency is 0.25Hz, the structural unit phase is 0 degrees, the main frequency is 0.75Hz, the structural unit phase is 90 degrees, and the main frequency is 1.25Hz, the structural unit phase is 90 Spend.
  • the purpose of this embodiment is to provide a high-order pseudo-random electromagnetic survey signal generation system, including:
  • the basic unit signal construction module constructs two or more basic unit signals according to the exploration requirements, wherein the basic unit signal is a step signal obtained by superimposing a plurality of square wave signals of the same phase, and the plurality of square wave signals are The frequency ratio between neighbors is 2;
  • the high-order pseudo-random signal generation module superimposes the two or more basic unit signals to obtain a superimposed step signal, and corrects the amplitude to be consistent with the square wave signal amplitude to obtain a high-order 2n sequence pseudo-random signal.
  • the purpose of this embodiment is to provide a computer-readable storage medium in which a plurality of instructions are stored, and the instructions are suitable for being loaded and executed by a processor of a terminal device:
  • the basic unit signal is a step signal obtained by superimposing a plurality of square wave signals with the same phase, and the frequency ratio between adjacent square wave signals Is 2;
  • the two or more basic unit signals are superimposed to obtain a superimposed step signal, and the amplitude is modified to make it consistent with the amplitude of the square wave signal to obtain a high-order 2n sequence pseudo-random signal.
  • the purpose of this embodiment is to provide a terminal device, including a processor and a computer-readable storage medium, the processor is used to implement each instruction; the computer-readable storage medium is used to store a plurality of instructions, the instructions are suitable for being loaded by the processor And execute:
  • the basic unit signal is a step signal obtained by superimposing a plurality of square wave signals with the same phase, and the frequency ratio between adjacent square wave signals Is 2;
  • the two or more basic unit signals are superimposed to obtain a superimposed step signal, and the amplitude is corrected to be consistent with the amplitude of the square wave signal to obtain a high-order 2n sequence pseudo-random signal.
  • the purpose of this embodiment is to provide an electrical survey signal transmitter, which adopts the signal generation method described in the embodiment to obtain a high-order 2n sequence pseudo-random signal that meets the survey requirements.

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Abstract

一种高阶伪随机电磁勘探信号生成方法及系统，方法包括：根据勘探需求构造两个或两个以上基本单元信号，其中，基本单元信号是多个同相位周期方波信号叠加得到的阶梯信号，多个方波信号相邻之间频率之比为2；将两个或两个以上基本单元信号叠加，得到叠加阶梯信号，并修正幅值使其与方波信号幅值一致，得到高阶2n序列伪随机信号。高阶伪随机电磁勘探信号生成方法及系统能够在有限频率区间内构造不同阶数的2n序列阶梯信号，改善在电磁勘探时的分辨率。

Description

一种高阶伪随机电磁勘探信号生成方法及系统 技术领域
本发明涉及地球物理勘探领域，尤其涉及一种高阶伪随机电磁勘探信号生成方法及系统。
背景技术
这里的陈述仅提供与本发明相关的背景技术，而不必然地构成现有技术。
目前，有很多种电磁勘探类方法，大多采用不同伪随机编码方式进行信号编码，尤其是在频率域勘探领域。但是过去很多伪随机信号的有效频率频带范围往往很窄，在勘探过程中需要不断改变勘探信号的频率成分，以获得不同频率区间的勘探信息，再依次发送，大大浪费时间，且提高了勘探成本。
发明内容
为克服上述现有技术的不足，本发明提供一种高阶伪随机电磁勘探信号生成方法及系统，能够在有限频率区间内构造不同阶数的2n序列伪随机信号，相比传统2n序列伪随机信号具有更高的分辨率。
为实现上述目的，本发明的一个或多个实施例提供了如下技术方案：
一种高阶伪随机电磁勘探信号生成方法，包括以下步骤：
根据勘探需求构造两个或两个以上基本单元信号，其中，所述基本单元信号是多个同相位周期方波信号叠加得到的阶梯信号，所述多个方波信号相邻之间频率之比为2；
将所述两个或两个以上基本单元信号叠加，得到叠加阶梯信号，并修正幅值使其与方波信号幅值一致，得到高阶2n序列伪随机信号。
一个或多个实施例提供了一种终端设备，包括处理器和计算机可读存储介质，处理器用于实现各指令；计算机可读存储介质用于存储多条指令，其特征在于，所述指令适于由处理器加载并执行所述的高阶伪随机电磁勘探信号生成方法。
一个或多个实施例提供了一种计算机可读存储介质，其中存储有多条指令，其特征在于，所述指令适于由终端设备的处理器加载并执行所述的高阶伪随机电磁勘探信号生成方法。
一个或多个实施例提供了一种电法勘探信号发送机，采用所述的高阶伪随机 电磁勘探信号生成方法生成高阶2n序列伪随机信号。
一个或多个实施例提供了一种电法勘探信号发送机，采用所述的高阶伪随机电磁勘探信号生成方法生成高阶2n序列伪随机信号。
以上一个或多个技术方案存在以下有益效果：
采用以上技术方案，能够根据勘探需求，在有限频段范围内增加主频个数，在有限频率区间内构造不同阶数的2n序列阶梯信号，以提高主频之间的密度，有助于改善在电磁勘探时的分辨率。
高阶伪随机信号可以实现几十个频率同时发送、同时接收，且相比于传统的单频或者多频发射信号，可实现海量数据采集，大幅提高了频谱密度，提升了纵向勘探分辨率；在总工作时长相同的条件下，每一频率可采集更长时间的数据，能够更好地压制背景噪声影响，提高了抗干扰能力；与此同时，在数据采集时只需要发射一组组合波形，而不需要改变发射波形，可以采用多台接收机连续滚动测量方式，从根本上改变了常规人工源电磁勘探方法的观测方式，从而实现野外数据高效采集，尤其适用于大面积的三维勘探，大大降低了勘探成本。目前，已经成功应用于野外实际勘探工作。
附图说明
构成本发明的一部分的说明书附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。
图1为本发明实施例中高阶伪随机电磁勘探信号生成方法流程图；
图2为本发明实施例中1Hz周期正弦信号与1Hz周期方波信号(相位
Figure PCTCN2021083727-appb-000001
)对应关系示意图；
图3为本发明实施例中7个频率叠加后台阶信号示意图；
图4为本发明实施例中7个频率叠加后台阶信号(a)及其频谱示意图(b)；
图5为本发明实施例中6个频率叠加后台阶信号(a)及其频谱示意图(b)；
图6为本发明实施例中包含13频波叠加信号及对应生成的伪随机信号。
图7为本发明实施例中包含13频波伪随机信号时域波形(a)及频谱示意图(b)；
图8为本发明实施例中第二个构造单元选取不同相位情况下的主频频谱相对均方误差曲线；
图9为本发明实施例中3Hz-6频-2π/5相位构造单元对应时域波形(a)及频谱特征(b)；
图10为本发明实施例中1Hz-7频-0相位、3Hz-6频-2π/5相位时对应伪随机信号时域波形(a)及频谱特征(b)；
图11为本发明实施例中第二个构造单元不同相位情况下的主频频谱相对均方误差曲线；
图12为本发明实施例中1Hz-11频-0相位与3Hz-10频-67π/180相位构造单元生成伪随机信号L2-F21—1Hz-1536Hz的时域波形(a)及频谱特征(b)；
图13为本发明实施例中3阶信号构造单元不同相位变化时主频频谱幅值相对均方误差变化曲线；
图14为本发明实施例中3阶2n序列信号(L3-F29—1Hz-1536Hz)波形(a)及频谱(b)；
图15为本发明实施例中4阶信号相位变化曲线；
图16为本发明实施例中4阶2n序列信号(L3-F29—1Hz-1536Hz)波形(a)及频谱(b)；
图17为本发明实施例中5阶信号随相位变化主频频谱相对均方误差变化曲线；
图18为本发明实施例中5阶2n序列信号(L5-F45—1Hz-1536Hz)波形(a)及频谱(b)；
图19为本发明实施例中2阶信号随相位变化主频频谱相对均方误差变化曲线；
图20为本发明实施例中1Hz-7频-π/9相位、3Hz-6频-π/9相位时对应伪随机信号时域波形(a)及频谱(b)；
图21为本发明实施例中适用于浅层勘探的2阶信号(L2-F27-0.25Hz-3072Hz)时域波形(a)及频谱(b)；
图22为本发明实施例中适用于浅层勘探的3阶信号(L3-F39-0.25Hz-3072Hz)时域波形(a)及频谱(b)。
以上附图涉及的频谱图中，仅折线的拐点存在频谱值，为更清楚的展示频谱幅值的大小和变化趋势，本发明实施例中均采用折线图表示。
具体实施方式
应该指出，以下详细说明都是例示性的，旨在对本发明提供进一步的说明。除非另有指明，本发明使用的所有技术和科学术语具有与本发明所属技术领域的普通技术人员通常理解的相同含义。
需要注意的是，这里所使用的术语仅是为了描述具体实施方式，而非意图限制根据本发明的示例性实施方式。如在这里所使用的，除非上下文另外明确指出，否则单数形式也意图包括复数形式，此外，还应当理解的是，当在本说明书中使用术语“包含”和/或“包括”时，其指明存在特征、步骤、操作、器件、组件和/或它们的组合。
在不冲突的情况下，本发明中的实施例及实施例中的特征可以相互组合。
为了演示，实施例中将以计算机仿真信号为例进行说用，所采用采样频率远高于伪随机信号中最高主频频率，计算机引入后对信号离散化所引起计算误差可以忽略。
实施例一
本实施例公开了一种高阶伪随机电磁勘探信号生成方法，如图1所示，所述方法包括：
步骤1：根据勘探需求构造两个或两个以上基本单元信号，其中，所述基本单元信号是多个同相位周期方波信号叠加得到的阶梯信号，所述多个方波信号相邻之间频率之比为2。
其中，所述周期方波的生成方法为：
生成与目标周期方波频率一致的正弦信号，并将这些正弦信号中，大于0的值置为A，小于0的值置为-A，等于0的位置按照索引奇偶分别置A和-A，具体地，索引识别信号中0的所有位置，按照奇偶项设置等于A和-A，如第1、3、5…个0位置数值置为A，第2、4、6…个0位置数值置为-A，得到一系列相位相同的周期方波信号，其中，A≠0，相位值可根据需求调整，本实施例中相位为0。
其中，周期方波的主频频率范围与勘探深度相关，主频频率的最低与最高频率可以根据待探测的深度需求(例如深层、浅层或其他具体探测深度)，根据经验公式辅助选择。具体地，获取用户需求的待探测深度范围；根据待探测深度范 围确定最高频率和最低频率。然后结合获取的需求的频率增加倍数，得到目标周期方波相应的频率。
以1Hz为例说明，首先生成一个幅值为100、相位为0的1Hz正弦信号：S(t)＝A sin(2πft+φ)，其中,S(t)为正弦信号，A为幅值，φ为相位，f为信号频率，幅值为100时，A＝100相位为0时φ＝0，频率为1Hz时，f＝1。
对这些正弦信号中大于0的值置100，小于0的值置-100，等于0的位置按照位置索引奇偶分别置100和-100，在这样的方式下，则可以生成1Hz的0相位方波信号，如图2所示，依此方式则可以生成所有频率幅值为100、相位为0的频率。
设R(t)为周期方波信号，当正弦信号在t位置S(t)为正值时，将信号数值置为A，即对应时间位置t位置R(t)＝A；当正弦信号在t位置S(t)为负值时，将信号数值置为-A，即对应时间位置t位置R(t)＝-A，本实施例中将正弦信号的相位都设为0，取A＝100，对这些正弦信号中大于0的值置100，小于0的值置-100，等于0的位置按照位置索引奇偶分别置100和-100。
本实施例中，为表述方便称周期方波最低频率为基频，图3生成信号的基频为1Hz。注意，在此叠加信号需为2n序列频率，即相邻方波频率之间需以连续2的倍数增加，依据此方法能够生成以1Hz为基频的其他频率如2Hz、4Hz、8Hz…64Hz相位为0时的周期方波信号，而通过叠加1Hz、2Hz、4Hz、8Hz、16Hz、32Hz、64Hz的0相位周期方波后，则可以获得含有多个频率的台阶信号，叠加后波形及对应频谱如图4所示。在频率域叠加后信号，1Hz、2Hz、4Hz、8Hz、16Hz、32Hz、64Hz对应频谱值是相同的，为100。这是因为每个方波只存在奇次谐波，不存在偶次谐波，所以1Hz的奇次谐波成分没有影响2Hz及其谐波频谱成分，同理2Hz及其奇次谐波成分并未对4Hz及其奇次谐波成分造成影响，同理依次类推，所以所有主频及其对应谐波的幅值是相同的，具有非常好的特征，此台阶信号作为第一个基本单元信号，该基本单元含有7个频率，最低频率为1Hz，相位φ＝0，则称之为1Hz-7频-0相位2n序列基本单元。
设最低频率为3Hz,基本单元中的频率数为6，其构造信号及频谱图为图5所示，6个周期方波频率为3Hz、6Hz、12Hz、24Hz、48Hz、96Hz，相位同样为0，该叠加后的阶梯信号作为第二个基本单元信号，称为3Hz-6频-0相位2n序列基 本单元。
基本单元的最低频率可以改变，频率数不一定为奇数，可以为偶数。本实施例中，第一个基本单元的最低频率称之为基频，第二个基本单元的最低频率为基频的3倍，第三个基本单元的最低频率为基频的5倍，第四个基本单元的最低频率为基频的7倍，第n个基本单元的最低频率为基频的2n+1倍。
本实施例中，要求对不同基本单元中主频数目进行求和后为奇数，不应为偶数，数学上，能够证明对奇数个周期方波(信号中数值只存在100与-100)相互叠加时，其幅值不可能为0，只可能是100或者-100的整数倍，所以经过叠加后，只需将大于100位置置为数值100，小于-100位置置为数值-100。假设第一个基本单元中主频数目为a 1、第二个基本单元中主频数目a 2、第三个基本单元中主频个数a 3，Num f为所有基本单元主频数目的和,Num f＝a 1+a 2+a 3。不难发现，当构造n阶2n序列伪随机信号时，Num f＝a 1+a 2+a 3+…+a n,其中a n为第n个基本单元中的主频数目。本发明中，在构造高阶2n序列伪随机信号时，Num f须为奇数，且对每个基本单元中的数目是否为奇数并不要求。同时，一般情况下，a 1数目应大于其他基本单元的主频数，以此来约束高阶2n序列伪随机信号中最高频率。
以上构造要求简化了后续叠加信号的处理难度，能够高效的得到勘探所需高阶2n序列伪随机信号。
本实施例中，基本单元中频率数目是可以改变的，可以将基本单元1Hz-11频-0相位和基本单元3Hz-10频-67π/180相位叠加构造2阶2n序列伪随机信号，图11和图12所示，其中复杂2n序列伪随机信号的编码方式为L2-F21--1Hz-1536Hz，其中L为Level的缩写，意为阶数，F为Frequency的缩写，意为信号包含主频个数，1Hz表示信号中最低频率主频，1536Hz表示信号中的最高频率主频。不同阶数代表主频之间的疏密程度，2阶比1阶密，3阶要比2阶密，以此类推。
本实施例根据勘探需求，在有限频段范围内增加主频个数，在有限频率区间内构造不同阶数的2n序列阶梯信号，以提高主频之间的密度，有助于改善在电磁勘探时的分辨率。
步骤2：将所述两个或两个以上基本单元信号叠加，得到叠加阶梯信号，并修正幅值使其与方波信号幅值一致，得到高阶2n序列伪随机信号。
具体地，将以上两组基本单元叠加后获得一组新的叠加阶梯信号，并对叠加阶梯信号中幅值大于A的位置幅值置为A，幅值小于-A的位置幅值置为-A，获得2n序列伪随机信号。如图6所示，红色为叠加阶梯信号，蓝色为伪随机信号。该伪随机信号波形及频谱如图7所示。在时间域，其信号中只存在100与-100数值，而在频率域含有13个主频频率，即两个基本单元中7个主频与6个主频的相加数,且由于基本单元中每个方波只有100和-100,数学上可以证明，13个100或-100叠加后一定不等于0，一定是大于等于100，或者小于等于-100的数值，因此通过将叠加后的数值进行大于100置100和小于-100置-100后，其信号中只会存在100和-100，不会存在等于0的位置。
但是，直接相加两个基本单元所得到的伪随机信号，主频频谱能量差异较大，并不适合应用于频率域电磁勘探，因此，还对叠加方式进行寻优。
步骤3：对于所述两个或多个基本单元信号中的至少一个进行相位调整，寻找使得叠加后高阶2n序列伪随机信号中各主频对应频谱幅值的均方差最小的相位，作为相应基本单元信号的最优相位；根据最优相位将所述两个或两个以上基本单元信号叠加，并修正幅值使其与方波信号幅值一致，得到高阶2n序列伪随机信号。
本实施例通过计算主频对应频谱幅值的均方差大小来判断其幅值之间的均匀性，选择使均方差数据最小的相位作为最优相位，以使各主要频率(主频)对应频谱幅值均匀，即主频能量分布更加均匀。具体地，通过不断改变信号构造基本单元的相位，即正弦信号生成公式中φ，进而生成对应相位的周期方波叠加后的阶梯信号，利用这种组合方式生成高阶2n序列伪随机信号，以使各主要频率(主频)对应频谱幅值均匀，即主频能量分布更加均匀。
具体地，对于进行相位调整的基本单元信号，首先将半个周期的相位弧度π拆分成N份(大于半个周期相位弧度π后，信号反向，但是信号整体形态一致，所以只需要考虑半个周期相位即可)，即相位改变基本单元为π/N；每次调整一个相位改变基本单元，记录叠加后高阶2n序列伪随机信号中各主频对应频谱值的均方差；绘制均方差大小随相位的变化曲线，寻找使得均方差最小的相位作为 该基本单元信号的最佳相位。
在本例中，假设将伪随机信号生成过程中将半个周期的相位弧度π，即拆分成π/180，每次相位改变π/180，依次增加，即每次改变公式中φ的值，其可能的值依次为0、π/180、2π/180、3π/180…179π/180。第一次构造高阶2n序列伪随机信号时，1Hz-7频-0相位基本单元不变，3Hz-6频-0相位作为第二个基本单元，两个基本单元进行叠加后，进行大于100位置置为数值100和小于-100位置置为数值-100后，计算并记录此时13个主频对应频谱值的相对均方误差值；改变第二个构造单位的相位至π/180，变为3Hz-6频-π/180，计算并记录此时13个主频对应频谱值的相对均方误差值，以此类推获得2π/180、3π/180…179π/180,180个不同相位下对应伪随机信号的相对均方误差曲线，通过比较获得相对均方误差最小值对应第二个基本单元的相位，如图8所示，相对均方误差最小点位于横坐标数值73，即第二个基本单元对应相位为2π/5，以此作为此13个频率下伪随机信号的最优构造方式，即第一个基本单元0相位，即为1Hz-7频-0相位，第二个基本单元相位2π/5时，即3Hz-6频-2π/5相位基本单元，如图9所示，获得L2-F13—1Hz-96Hz伪随机信号的最优构造方式，如图10所示。
第一基本单元对应相位φ允许改变。如针对1Hz-7频基本单元和3Hz-6频基本单元进行叠加合成2n序列信号时，两个基本单元相位同时改变，当N＝36时对应相对均方误差变化曲线如图19所示，其最小值点两个基本单元对应相位分别为π/9与2π/9，此时对应2阶2n序列伪随机信号时域波形和频谱如图20所示。
若要通过三个基本单元构造3阶2n序列伪随机信号时，在构造此高阶2n序列伪随机信号时，将半个周期的相位弧度π拆分成60个基本单元(即N＝60)，固定第一个构造单位相位为0，则另外两个构造基本单元的相位变化组合共有3600种，计算并记录每一种组合情况下的伪随机信号组合方式，比较获得主频频谱幅值最小相对均方误差位置，并获取在此位置对应不同基本单元的相位信息，如图13和图14所示。
通过不断改变构造基本单元的相位获取主频频谱幅值相对均方误差最小值点，即频谱成分最优分配2n序列伪随机信号。
如图14所示，其伪随机信号编号为L3-F29—1Hz-1536Hz，即为3阶29频、 最低主频1Hz，最高主频1536Hz的2n序列伪随机信号，其三个基本单元分别为1Hz-11频-0相位、3Hz-10频-π/2相位及5Hz-8频-9π/20相位，三个基本单元在对应相位条件下获得此频段主频能量最优分配的2阶2n序列伪随机信号，如图14b频谱图所示。
本发明所提出构造方法，在固定频率区间内，可以构造更高阶信号，如图15和图16中所示4阶2n序列伪随机信号L4-F37—1Hz-1536Hz，图14和图15所示5阶2n序列伪随机信号L5-F45—1Hz-1536Hz。
本发明中生成高阶2n序列伪随机信号频率区间，是能够根据勘探需要改变的，一般情况下频率区间的最低频率不低于0.015625Hz，最高频率不高于8192Hz。
采用本实施例的方法，能够构造适用于浅层高精度勘探的信号：L2-F27-0.25Hz-3072Hz，其中，主频为0.25Hz构造单元相位为10度，主频为0.75Hz构造单元相位为120度；以及，L3-F39-0.25Hz-3072Hz，其中，主频为0.25Hz构造单元相位为0度，主频为0.75Hz构造单元相位为90度，主频1.25Hz构造单元相位为90度。
实施例二
本实施例的目的是提供一种高阶伪随机电磁勘探信号生成系统，包括：
基本单元信号构造模块，根据勘探需求构造两个或两个以上基本单元信号，其中，所述基本单元信号是多个同相位周期方波信号叠加得到的阶梯信号，所述多个方波信号相邻之间频率之比为2；
高阶伪随机信号生成模块，将所述两个或两个以上基本单元信号叠加，得到叠加阶梯信号，并修正幅值使其与方波信号幅值一致，得到高阶2n序列伪随机信号。
实施例三
本实施例的目的是提供一种计算机可读存储介质，其中存储有多条指令，所述指令适于由终端设备的处理器加载并执行：
根据勘探需求构造两个或两个以上基本单元信号，其中，所述基本单元信号是多个同相位周期方波信号叠加得到的阶梯信号，所述多个方波信号相邻之间频率之比为2；
将所述两个或两个以上基本单元信号叠加，得到叠加阶梯信号，并修正幅值 使其与方波信号幅值一致，得到高阶2n序列伪随机信号。
实施例四
本实施例的目的是提供一种终端设备，包括处理器和计算机可读存储介质，处理器用于实现各指令；计算机可读存储介质用于存储多条指令，所述指令适于由处理器加载并执行：
根据勘探需求构造两个或两个以上基本单元信号，其中，所述基本单元信号是多个同相位周期方波信号叠加得到的阶梯信号，所述多个方波信号相邻之间频率之比为2；
将所述两个或两个以上基本单元信号叠加，得到叠加阶梯信号，并修正幅值使其与方波信号幅值一致，得到高阶2n序列伪随机信号。
实施例五
本实施例的目的是提供一种电法勘探信号发送机，采用实施例一种所述信号生成方法，得到符合勘探需求的高阶2n序列伪随机信号。
以上所述仅为本发明的优选实施例而已，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。
以上所述仅为本发明的优选实施例而已，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种高阶伪随机电磁勘探信号生成方法，其特征在于，包括以下步骤：
    根据勘探需求构造两个或两个以上基本单元信号，其中，所述基本单元信号是多个同相位周期方波信号叠加得到的阶梯信号，所述多个方波信号相邻之间频率之比为2；
    将所述两个或两个以上基本单元信号叠加，得到叠加阶梯信号，并修正幅值使其与方波信号幅值一致，得到高阶2n序列伪随机信号。
  2. 如权利要求1所述的一种高阶伪随机电磁勘探信号生成方法，其特征在于，所述两个或两个以上基本单元信号满足以下要求：
    第一个基本单元信号中主频的最低频率记为基频，第n个基本单元的最低频率为基频的2n+1倍，n为大于1的自然数；
    所有基本单元信号的主频数目之和为奇数。
  3. 如权利要求1所述的一种高阶伪随机电磁勘探信号生成方法，其特征在于，周期方波的生成方法为：
    首先生成与目标周期方波频率一致的正弦信号，将这些正弦信号中，大于0的值置为A，小于0的值置为-A，得到一系列相位相同的周期方波信号，其中，A≠0；
    对于周期方波中值为0的信号，按位置赋值A或-A，得到不含0值的周期方波。
  4. 如权利要求1所述的一种高阶伪随机电磁勘探信号生成方法，其特征在于，所述方法还包括：
    对于所述两个或多个基本单元信号中的至少一个进行相位调整，寻找使得叠加后高阶2n序列伪随机信号中各主频对应频谱幅值的均方差最小的相位，作为相应基本单元信号的最优相位；
    根据最优相位将所述两个或两个以上基本单元信号叠加，并修正幅值使其与方波信号幅值一致，得到最终的高阶2n序列伪随机信号。
  5. 如权利要求4所述的一种高阶伪随机电磁勘探信号生成方法，其特征在于，最优相位寻找方法为：
    对于进行相位调整的基本单元信号，首先将半个周期的相位弧度π拆分成N份，得到相位改变基本单元π/N；
    每次调整一个相位改变基本单元，记录叠加后高阶2n序列伪随机信号中各主频对应频谱值的均方差；
    绘制均方差大小随相位的变化曲线，寻找使得均方差最小的相位作为该基本单元信号的最佳相位。
  6. 如权利要求5所述的一种高阶伪随机电磁勘探信号生成方法，其特征在于，根据所述方法构造得到的适用于浅层勘探的信号如下：
    二阶2n序列伪随机信号，其中，两个基本单元信号的主频和相位分别为：0.25Hz和10度，0.75Hz和120度；以及，
    三阶2n序列伪随机信号，其中，三个基本单元信号的主频和相位分别为：0.25Hz和0度，0.75Hz和90度，1.25Hz和90度。
  7. 一种高阶伪随机电磁勘探信号生成系统，其特征在于，包括：
    基本单元信号构造模块，根据勘探需求构造两个或两个以上基本单元信号，其中，所述基本单元信号是多个同相位周期方波信号叠加得到的阶梯信号，所述多个方波信号相邻之间频率之比为2；
    高阶伪随机信号生成模块，将所述两个或两个以上基本单元信号叠加，得到叠加阶梯信号，并修正幅值使其与方波信号幅值一致，得到高阶2n序列伪随机信号。
  8. 一种终端设备，包括处理器和计算机可读存储介质，处理器用于实现各指令；计算机可读存储介质用于存储多条指令，其特征在于，所述指令适于由处理器加载并执行权利要求1-6中任一项所述的高阶伪随机电磁勘探信号生成方法。
  9. 一种计算机可读存储介质，其中存储有多条指令，其特征在于，所述指令适于由终端设备的处理器加载并执行权利要求1-6中任一项所述的高阶伪随机电磁勘探信号生成方法。
  10. 一种电法勘探信号发送机，其特征在于，采用如权利要求1-6任一项所述的高阶伪随机电磁勘探信号生成方法生成高阶2n序列伪随机信号。
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