CN111812609B - Geological radar signal recovery method with multistage filtering nested amplitude gain - Google Patents

Abstract

The invention relates to a geological radar signal recovery method of multistage filtering nested amplitude gain, which comprises the following steps: firstly, performing primary editing and modification treatment on geological radar data to be treated, performing primary broadband filtering and amplitude recovery, and performing overall signal enhancement on signals; and then, carrying out targeted main frequency filtering and signal enhancement according to the main frequency of the geological radar antenna, so as to realize target signal and deep signal enhancement and extraction. The invention can realize the recovery of normal signals and the deep signal recovery of radar detection in areas with quicker signal attenuation (such as loess areas), can also realize the enhancement and extraction of special signals such as holes, root systems and the like, further greatly improves the refined detection depth of geological radar, can be widely applied to the data processing in the shallow refined detection fields such as urban underground space detection, root system detection, cavity detection, pipeline detection and the like, and is a signal recovery method with extremely high broad spectrum.

Description

Geological radar signal recovery method with multistage filtering nested amplitude gain

Technical Field

The invention relates to a radar signal restoration technology, in particular to a geological radar signal restoration method with multistage filtering nested amplitude gain.

Background

The geological radar technology is widely applied to the fields of urban underground space detection, pipeline detection, root system detection, bedrock detection, loess pore and other engineering investigation, and has the characteristics of portability, rapidness, high detection precision and high resolution, but the detection depth is always the biggest problem of the technology due to the fact that the signal attenuation is faster.

To solve the above problems, the industry mainly uses relatively low frequency band antennas to achieve the purpose of detecting more depth, but this is a method at the cost of resolution, and corresponding signals are easy to leak when small targets are detected; the deep signal needs to be restored without sacrificing resolution. Practice shows that if single signal recovery is carried out, the deep signal is mostly not greatly improved, if multiple gains are carried out, the interference signal is easily amplified to be at the same level with the main signal, and great difficulty is caused for eliminating the later interference signal and reserving the main signal. Thus, in the art, development of effective weak signal recovery techniques to achieve high depth exploration of the resolution of the warranty has been a leading-edge topic of geological radar detection. In addition, the extraction and identification of some special signals (such as dovetail signals) is well-tolerated by more efficient signal recovery techniques, and improper amplitude recovery often results in signal distortion or other signals being presented, thereby affecting the identification of the special target.

Disclosure of Invention

First, the technical problem to be solved

In view of the above-mentioned shortcomings and disadvantages of the prior art, the present invention provides a geological radar signal recovery method with multistage filtering nested amplitude gain, which solves the technical problem that weak radar signals and deep radar signals cannot be recovered correctly in geological radar exploration.

(II) technical scheme

In order to achieve the above purpose, the main technical scheme adopted by the invention comprises the following steps: the embodiment of the invention provides a geological radar signal recovery method with multistage filtering nested amplitude gain, which comprises the following steps:

s1, performing energy attenuation reverse gain processing on a section of geological radar data subjected to pre-processing to obtain data I of one-time overall signal recovery;

s2, carrying out one-dimensional cut-off filtering on the first data to obtain second data from which ultra-high frequency and ultra-low frequency signals are removed;

s3, selecting a gain processing technology corresponding to the target signal according to the attribute of the target data, performing gain processing on the second data, and obtaining the second data after gain processing;

s4, processing the second data after gain processing by adopting band-pass filtering with specified frequency to obtain geological radar data with deep signals and weak signals recovered, wherein the geological radar data comprises the target data.

Optionally, the frequency of the one-dimensional cut-off filter corresponding to the filter in the S2 is set to be 1/10-5 times of the main frequency of the geological radar antenna.

Optionally, in S3, if the target signal is a horizontal layered signal or an oblique signal, performing gain processing by using an energy attenuation inverse gain technique;

if the target signal is a dovetail-shaped signal, gain processing is performed by adopting a geometric divergence compensation gain technology.

Optionally, in S4, the main frequency of the radar antenna is taken as the center, the low-frequency shearing frequency F1 of the corresponding filter of the band-pass filter is set between 0.6-0.7 times the main frequency of the geological radar antenna used, the low-pass frequency F2 of the corresponding filter of the band-pass filter is set between 0.8-0.9 times the main frequency, the high-pass frequency F3 of the corresponding filter of the band-pass filter is set between 1.4-1.6 times the main frequency, and the high-frequency shearing frequency F4 of the corresponding filter of the band-pass filter is set between 2.0-2.2 times the main frequency, wherein F1< F2< F3< F4;

accordingly, bandpass filtering with a specified frequency includes: band pass filtering of the low frequency shear frequency F1, the low pass frequency F2, the high pass frequency F3 and the high frequency shear frequency F4.

Optionally, before S1, the method further comprises:

s0, performing pre-processing for removing background interference signals on geological radar data to be processed.

Optionally, S0 includes:

and sequentially processing the geological radar data to be processed by adopting a maximum phase correction mode, a first arrival cutting technology, a DC signal removing mode and a background filtering mode to obtain geological radar data after pre-processing.

Optionally, the geological radar data to be processed includes: data collected by the Mala, sir4000, EKKOPlus or EKKOPlus-utral type radar and the like are mainly used for deep and weak signal recovery of the data.

Optionally, in S2, the one-dimensional cut-off filtering mode is a baswoth cut-off filtering mode;

the energy decay in S1 has an index in the reverse gain in the range of 1.0-1.5.

Optionally, when the target signal is a root system target signal, performing gain processing in S3 on the geological radar data after the pre-processing, performing one-dimensional cut-off filtering in S2, performing energy attenuation inverse gain processing in S1, and performing band-pass filtering processing of the specified frequency in S4.

Optionally, the method further comprises:

and correcting the geological radar data with the deep signals and the weak signals recovered.

(III) beneficial effects

The beneficial effects of the invention are as follows: in the invention, a twice filtering and amplitude gain combination method is applied to recover weak signals and deep signals in geological radar data. The method comprises the steps of performing primary broadband filtering and amplitude recovery after performing earlier editing and modification treatment on geological radar data, and performing overall signal enhancement on signals; and then, carrying out targeted main frequency filtering and signal enhancement according to the main frequency of the geological radar antenna, so as to realize target signal and deep signal enhancement and extraction. Therefore, the method can realize the recovery of normal signals and the deep signal recovery of radar detection in areas with quicker signal attenuation (such as loess areas), can also realize the enhancement and extraction of special signals such as holes, root systems and the like, further greatly improves the refined detection depth of geological radar, and can be widely applied to the data processing in shallow refined detection fields such as urban underground space detection, root system detection, cavity detection, pipeline detection and the like.

The method belongs to a geological radar signal recovery method with extremely high broad spectrum, is applied to the aspects of broad spectrum amplitude recovery, special amplitude recovery, frequency change, amplitude recovery and the like, and can realize the recovery and identification of geological radar weak signals and deep signals. The method of the invention has been applied to a large number of fields in E Er, guanzhong, and has been successful.

Drawings

FIGS. 1A and 1B are flow charts of a method for recovering a geological radar signal with multistage filtering nested amplitude gains according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating a process of processing data according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of an energy-decay anti-compensation amplitude gain (first order gain) provided by an embodiment of the present invention;

FIG. 4 is a schematic diagram of one-dimensional Butterworth filtering (first filtering) according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an energy-decay anti-compensation amplitude gain (second order gain) according to an embodiment of the present invention;

FIG. 6 is a diagram illustrating the geometric diffusion compensation gain amplitude recovery (second gain) of root system signals according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a bandpass signal filtering and channel equalization process (second filtering and modification compensation) according to an embodiment of the invention;

fig. 8 is a schematic diagram of weak signal recovery example loess hole signal recovery according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of deep signal recovery from deep cleavage of a formation according to an embodiment of the present invention.

Detailed Description

The invention will be better explained by the following detailed description of the embodiments with reference to the drawings.

In order that the above-described aspects may be better understood, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Example 1

Fig. 1A shows a flowchart of a geological radar signal recovery method with multistage filtering nested amplitude gain according to an embodiment of the present invention, where the method of the embodiment includes the following steps:

s1, processing energy attenuation reverse gain on a section of geological radar data after pre-processing to obtain data I of one-time overall signal recovery.

In this embodiment, the radar profile (geological radar data to be processed) is first subjected to conventional preprocessing, which mainly includes maximum phase correction, first arrival removal, direct current signal removal, background filtering, and the preprocessing is used to remove the conventional instrument and background interference signal, so as to prepare for later amplitude recovery.

S2, carrying out one-dimensional cut-off filtering on the first data to obtain second data from which the ultra-high frequency and ultra-low frequency signals are removed.

For example, with one-dimensional cut-off filtering, the bandwidth is widened, and the filter is set to have a bandwidth generally between 1/10 and 5 times the frequency of the radar antenna used, so as to remove ultra-high frequency and ultra-low frequency signals and highlight signals near the main frequency. That is, the frequency of the one-dimensional cut-off filter frequency corresponding filter is set to be between 1/10 and 5 times of the main frequency of the geological radar antenna.

S3, selecting a gain processing technology corresponding to the target signal according to the attribute of the target data, performing gain processing on the second data, and obtaining the second data after gain processing.

For example, the target signal may be enhanced by selecting an appropriate gain. For horizontal lamellar or oblique signals, an energy attenuation reverse gain technology is adopted for gain; dovetail-shaped signals (such as root systems, holes and pipelines) adopt geometric divergence compensation gain technology.

S4, processing the second data after gain processing by adopting band-pass filtering with specified frequency to obtain geological radar data with deep signals and weak signals recovered, wherein the geological radar data comprises the target data.

For example, the band-pass filtering compressed signal band can be selected again, the main frequency of the antenna is taken as the center, the shearing frequency (F1, F4) of the filter is set to be 0.6-2.2 times of the main frequency, the bandwidth (F2, F3) is set to be 0.8-1.5, and then the band-pass filtering is carried out, so that the recovery of the deep signal and the weak signal can be realized. Specifically, the main frequency of the radar antenna is taken as the center, the low-frequency shearing frequency F1 of the corresponding filter of the band-pass filter is set between the main frequencies of the geological radar antenna used by 0.6-0.7 times, the low-pass frequency F2 of the corresponding filter of the band-pass filter is set between 0.8-0.9 times the main frequency, the high-pass frequency F3 of the corresponding filter of the band-pass filter is set between 1.4-1.6 times the main frequency, and the high-frequency shearing frequency F4 of the corresponding filter of the band-pass filter is set between 2.0-2.2 times the main frequency, wherein F1 is smaller than F2 is smaller than F3; that is, band-pass filtering with a specified frequency includes: band pass filtering of the low frequency shear frequency F1, the low pass frequency F2, the high pass frequency F3 and the high frequency shear frequency F4.

It should be noted that, in step S4, the main frequency ranges (F2, F3) may be properly enlarged and reduced, mainly determined according to the depth of the target horizon, and if the depth is larger, a part of low frequency models are properly reserved, and the values of F1, F2 are smaller than the normal range; if the target layer is shallow, the high-frequency signals are properly reserved, and the values of F3 and F4 are larger than those of the normal conditions.

The method of the embodiment can realize the recovery of normal signals and the deep signal recovery of radar detection in areas with quicker signal attenuation (such as loess areas), can also realize the enhancement and extraction of special signals such as holes, root systems and the like, further greatly improves the fine detection depth of geological radar, and can be widely applied to the data processing in the shallow fine detection fields such as urban underground space detection, root system detection, cavity detection, pipeline detection and the like

Example two

Fig. 1A is a specific flowchart of a geological radar signal recovery method with multistage filtering nested amplitude gain according to the present invention, as shown in fig. 1A, and the geological radar signal recovery method with multistage filtering nested amplitude gain includes: 6 steps: pre-processing, first energy enhancement, butterworth filtering, second energy enhancement, bandpass filtering, channel equalization, etc.

A geological radar signal recovery method with multi-stage filtering nested amplitude gains according to an embodiment of the present invention will be described in detail with reference to fig. 1B to 9.

The first step: preprocessing of geological radar profile data

The preprocessing of the radar profile mainly comprises the steps of maximum phase correction, first arrival cutting, background filtering and the like. Because the geological radar signal is always transmitted into the ground by air, the dielectric constants of the two signals are greatly different, and a reflection signal with larger amplitude is formed at the junction of the ground and the air, as shown in fig. 1A. According to the characteristic, the first arrival wave can be cut off according to the maximum phase or the starting point of the radar signal, so that the radar signal is classified into a state with the ground surface being 0, and the determination of the later depth is facilitated.

However, in actual operation, due to the difference of geological conditions, signals of the radar at the junction of the ground and the air are often not on the same horizontal line, but drift occurs. To eliminate these drifts, the maximum phase of the signal in this region needs to be adjusted to a uniform level with the strong amplitude signal at the ground-air interface as a reference surface, facilitating the removal of the first arrival wave, which requires maximum phase correction. After the first-arrival excision, 2D background filtering is carried out, mainly transverse air waves are excised, and meanwhile, the signal amplitude in the section is leveled, so that the purposes of suppressing strong amplitude and enhancing weak amplitude are achieved.

Through the processing, the amplitude is more uniform, and preparation is made for the recovery of the later weak signal and the deep signal.

And a second step of: the first energy boost. On the basis of the first step, the energy attenuation inverse gain technology is adopted to recover the overall amplitude of the section once, so that the weak amplitude of the section is amplified once, and the important point is to enhance the amplitude of the medium depth. The energy attenuation reverse gain adopts an exponential form algorithm, and the gain coefficient is between 1.0 and 3.0. As shown in fig. 4, the overall signal is significantly enhanced by energy attenuation with inverse gain.

And a third step of: and (5) Bus Wash filtering. The section is filtered on the basis of the first amplitude gain, but the frequency band is very wide, and the main purpose is to consider that integer harmonic waves and fractional harmonic waves are generated in the process of the electromagnetic wave signal propagating underground, the parts of the signals which are close to the main frequency are useful, and the ultra-low frequency and ultra-high frequency signals are harmful signals generally, so that the signals are eliminated. The use of the butterworth cut-off filter is mainly to eliminate the ultra-high frequency and ultra-low frequency signals. In order to achieve the above purpose, a one-dimensional cut-off filter is adopted, 1/10 times of dominant frequency and 5 times of dominant frequency are adopted as cut-off frequency boundaries of the filter, and then Butterworth filtering is carried out, so that the aim can be achieved.

Fourth step: the second energy boost. And on the basis of the third step, starting to carry out key recovery on the target signal. The target signal refers to the radar wave signal which presents different characteristics according to the characteristics of stratum, such as water level and stratified geological structure, and generally presents a transverse or oblique continuous bright line, which is called a linear signal; such as tree root systems, loess holes, underground pipes, etc., radar wave signals generally exhibit characteristics approximating an arc of a dovetail shape, and are internationally known as dovetail-like signals. These two-shaped signals mainly constitute radar profile signals. According to the requirement of a research target, if the target signal is a linear signal, an energy attenuation reverse gain technology is adopted, and the recovery of the linear signal can be realized by a gain factor of 1.0-15; if the target signal is a dovetail signal, a geometric diffusion compensation signal gain technique is selected. As shown in fig. 5, the linear signal is well recovered after the energy attenuation reverse gain technology is adopted; fig. 6 illustrates that the geometrical diffusion gain has a better dovetail signal recovery effect when the geometrical diffusion is used for recovering the root system signal of salix matsudana.

Fifth step: and (5) band-pass filtering. After the target signal is recovered, the main frequency filtering can be performed, the main frequency signal is highlighted, the interference signal is suppressed, and the band-pass filtering is adopted in the technical process. Firstly, setting a band filter to take an antenna main frequency as a center, setting the shearing frequency (F1, F4) of the filter to be 0.6-2.2 times of the main frequency, and setting the bandwidth (F2, F3) to be 0.8-1.5; and then the band-pass filtering is carried out to highlight the main frequency signal. As shown in fig. 7, after the band-pass filtering, the deep hidden signal can be clearly seen, and the purpose of deep signal recovery is achieved. It should be noted that, the band-pass filter needs to be correspondingly adjusted according to the target depth, if the detected target is shallower, the signals of the high frequency band can be properly reserved, and the values of F3 and F4 can be properly amplified; if the detection depth is deeper, the signals of the low frequency band are needed to be reserved, and the values of F3 and F4 can be properly reduced.

Sixth step: after the processing in the step 5, the recovery of weak signals and deep signals of any geological radar signals can be basically realized, but the signals are likely to be uneven in transverse distribution, and the channel equalization amplitude average is needed, so that the continuity of the same phase axis is increased.

The recovery of weak signals and deep signals of geological radar signals can be realized by completing the steps 1-6, and experiments show that the set of technical processes can be simultaneously applied to deep and weak signal analysis of Mala, sir4000, EKKOplus, EKKOplus-utral and other types of radars; meanwhile, the process has the characteristics of high reliability, easiness in implementation, corresponding modules in common earthquake and radar software, simplicity in operation and the like. 2-7 are all from a Mala radar system, FIG. 8 is a weak signal recovery example of recovering underground holes in loess areas by applying the technical process, an antenna is an EKKOPlus100Mhz antenna, a detection target is to find an underground loess hole with a depth of more than ten meters, and clear hole signals (a cluster of arc-shaped homophase shafts) can be obtained after the process treatment; fig. 9 is a diagram of the application of this set of techniques to deep signal recovery. The EKKOPlus-U.S. 25Mhz antenna is used for data acquisition, the detection target is the shallow stratum cleavage characteristic of 150 meters, the clearer stratum attitude information of 180 meters can be obtained after signal recovery, and the depth of the geological radar on the other side is greatly improved.

The method of the embodiment carries out primary broadband filtering and amplitude recovery after carrying out earlier editing and modification treatment on geological radar data, and carries out overall signal enhancement on signals; and then, carrying out targeted main frequency filtering and signal enhancement according to the main frequency of the geological radar antenna, so as to realize target signal and deep signal enhancement and extraction. The method belongs to a geological radar signal recovery method with extremely high broad spectrum, is applied to the aspects of broad spectrum amplitude recovery, special amplitude recovery, frequency change, amplitude recovery and the like, and can realize the recovery and identification of geological radar weak signals and deep signals.

In addition, the method of the embodiment of the invention has been applied to a plurality of basins E Er and Guanzhong basins in a large number of application tests and has been successful.

It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions.

It should be noted that in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the terms first, second, third, etc. are for convenience of description only and do not denote any order. These terms may be understood as part of the component name.

Furthermore, it should be noted that in the description of the present specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with the embodiment or example being included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art upon learning the basic inventive concepts. Therefore, the appended claims should be construed to include preferred embodiments and all such variations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, the present invention should also include such modifications and variations provided that they come within the scope of the following claims and their equivalents.

Claims (4)

1. A geological radar signal recovery method of multistage filtering nested amplitude gain, characterized in that the geological radar signal recovery method is integrated in a radar software system, comprising:

s0, performing pre-processing for removing background interference signals on geological radar data to be processed; sequentially processing the geological radar data to be processed in sequence by adopting a maximum phase correction mode, a first arrival cutting technology, a DC signal removing mode and a background filtering mode to obtain geological radar data after pre-processing;

the geological radar data to be processed are data of weak signals of underground holes in loess areas detected by using an EKKOPlus100Mhz antenna;

s1, performing energy attenuation reverse gain processing on a section of geological radar data subjected to pre-processing to obtain data I of one-time overall signal recovery; the gain factor of the energy attenuation reverse gain is 3.0;

the first data of the primary integral signal recovery comprises: a signal with a section weak amplitude amplified once to enhance the amplitude of the medium depth;

s2, carrying out one-dimensional cut-off filtering on the first data to obtain second data from which ultra-high frequency and ultra-low frequency signals are removed; the frequency of the one-dimensional cut-off filtering frequency corresponding filter is set to be 1/10-5 times of the main frequency of the used geological radar antenna;

s3, selecting a gain processing technology corresponding to the target signal according to the attribute of the target data, performing gain processing on the second data, and obtaining the second data after gain processing;

if the target signal is a horizontal layered signal or an oblique signal, performing gain processing by adopting an energy attenuation reverse gain technology;

if the target signal is a dovetail-shaped signal, performing gain processing by adopting a geometric divergence compensation gain technology;

s4, processing the second data after gain processing by adopting band-pass filtering with specified frequency to obtain geological radar data with deep signals and weak signals recovered, wherein the geological radar data comprises the target data;

specifically, the main frequency of the radar antenna is taken as the center, the low-frequency shearing frequency (F1) of the corresponding filter of the band-pass filter is set between 0.6-0.7 times of the main frequency of the geological radar antenna used, the low-pass frequency (F2) of the corresponding filter of the band-pass filter is set between 0.8-0.9 times of the main frequency, the high-pass frequency (F3) of the corresponding filter of the band-pass filter is set between 1.4-1.6 times of the main frequency, and the high-frequency shearing frequency (F4) of the corresponding filter of the band-pass filter is set between 2.0-2.2 times of the main frequency, wherein F1< F2< F3< F4;

accordingly, bandpass filtering with a specified frequency includes: bandpass filtering of the low-frequency shear frequency (F1), the low-pass frequency (F2), the high-pass frequency (F3) and the high-frequency shear frequency (F4) is employed.

2. The method according to claim 1, wherein in S2, the one-dimensional cut-off filtering is a baswok cut-off filtering;

the energy decay in S1 has an index in the reverse gain in the range of 1.0-1.5.

3. The method according to claim 1, wherein when the target signal is a root target signal, the gain processing in S3 is performed on the geological radar data after the pre-processing, then the one-dimensional cut-off filtering in S2 is performed, then the energy attenuation inverse gain processing in S1 is performed, and then the band-pass filtering processing of the specified frequency in S4 is performed.

4. A method according to any one of claims 1 to 3, wherein the method further comprises:

and correcting the geological radar data with the deep signals and the weak signals recovered.