CN109100809B - Weak magnetic signal noise suppression and signal extraction device and method under geomagnetic background - Google Patents
Weak magnetic signal noise suppression and signal extraction device and method under geomagnetic background Download PDFInfo
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- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
- G01V3/081—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices the magnetic field is produced by the objects or geological structures
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- 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
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- 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
- G01V3/40—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for measuring magnetic field characteristics of the earth
Abstract
A device and a method for suppressing noise of weak magnetic signals and extracting signals under a geomagnetic background field comprise a magnetic detector, a data acquisition card for detecting the weak magnetic signals, a spectrum analyzer and a data acquisition card for acquiring signals of the magnetic detector and transmitting the signals to the spectrum analyzer; and the spectrum analyzer is used for carrying out spectrum analysis and corresponding signal filtering processing on the acquired signals. According to the invention, the frequency of the magnetic difference signal is increased by increasing the relative movement speed between the detected target and the detection sensor, so that the magnetic difference signal is in a higher frequency band, and the geomagnetic signal is near the frequency of 0Hz, therefore, the frequency of the target signal is increased, the weak magnetic signal and the geomagnetic background field are separated on a frequency spectrum, and then the geomagnetic noise is filtered by adopting a high-pass filter, so that the purposes of noise suppression and signal extraction are achieved.
Description
Technical Field
The invention relates to the technical field of weak magnetic detection, in particular to a method for suppressing weak magnetic signal noise and extracting a signal under a geomagnetic background field.
Background
The weak magnetic detection technology is based on the physical phenomenon that an object with ferromagnetism disturbs geomagnetic field distribution to generate geomagnetic field distribution abnormity, extracts characteristic quantities of magnetic abnormity signals by measuring the distribution of the magnetic abnormity signals, and finally obtains target related information by certain data processing. Compared with detection means such as light and sound, the weak magnetic detection is a passive detection technology, has the advantages of good concealment and no influence of weather environment, and is widely applied to civil use such as aviation prospecting, navigation and positioning, and military fields such as target search and battlefield monitoring.
When weak magnetic signals are detected, the magnetic signals of a target object are in a nanometer order, the intensity of geomagnetic field signals reaches tens of micro-meters order, and the difference between the intensity of the geomagnetic field signals and the intensity of the geomagnetic field signals is about 3 orders of magnitude, so that geomagnetic noise suppression and signal extraction are very difficult.
In the existing weak magnetic detection technology, the detection sensitivity of detector hardware is mainly improved at home and abroad, such as a triaxial magnetometer, a fluxgate sensor, a magnetoresistive detector, an optical pump magnetometer, a superconducting quantum interferometer and the like. Wherein the three-axis magnetometer is based on Faraday electromagnetic induction principle, and the detection range can reach 10-3—102T, belongs to early weak magnetic detection equipment, and the sensitivity is lower. The fluxgate sensor has the characteristics of low noise, high frequency response, good temperature performance and the like, and the measurement range can reach 10-10—10-3T, sensitivity covers sub-nT orders of magnitude of weak signals. The magneto-resistance detector is based on the principle that resistance changes under the action of a magnetic field, the sensitivity can reach pT magnitude theoretically, and the method has the advantages of high resolution, high response speed, small volume, low power consumption and the like, and can be integrated. The optical pump magnetometer achieves the detection purpose by utilizing the instability of gas in a magnetic field, the detection sensitivity can reach fT magnitude, and the sensitivity of a G-858 cesium optical pump magnetometer of a geometer company reaches 0.01 pT. The superconducting quantum interference magnetometer (SQUID) is based on the Josephson effect theory and is made of superconducting materials, and the sensitivity reaches 10-15T (ft), the magnetic detector with the highest sensitivity at present. Although the sensitivity of the hardware aspect of the current detection equipment is higher and higher, the intensity of the geomagnetic background field reaches tens of micro-magnitude, and how to extract magnetic signals of nano-magnitude, pico-magnitude and even femto-magnitude from the large background field is the biggest difficulty.
The international method for extracting weak magnetic signals aiming at inhibiting geomagnetic background fields mainly comprises the following steps: (1) the background magnetic field compensation can be realized through multi-channel magnetic detection, the suppression of a geomagnetic background field is carried out on signals, however, the engineering quantity is large, the introduction of a multi-channel detection method causes the increase of electric signal noise, and the cost is high due to multi-channel and probe equipment. (2) The method can carry out rear-end filtering processing on stored data after signals are collected, but real-time detection monitoring cannot be realized, detection results lack timeliness, and the frequency of magnetic signals of detected target objects is close to that of geomagnetic signals, so that the rear-end signal filtering processing method is poor in effect, and the suppression difficulty of background magnetic fields is increased. (3) The method filters the low-frequency signal of the geomagnetic field in circuit design, and realizes real-time processing of the detection information. However, the geomagnetic noise signal is not effectively separated from the target magnetic signal, the filter circuit has a limitation in its own filter characteristic, and a good suppression effect is not obtained. (4) The method is based on basic signal characteristics of magnetic signals, and three standard orthogonal bases are used for effectively extracting the magnetic signals with characteristics in geomagnetic background noise. The invention provides a method for improving the relative movement speed between a magnetic target and weak magnetic detection so as to increase the frequency of a magnetic signal, separate the magnetic signal from low-frequency geomagnetic noise, and have the characteristics of real time and easy analysis.
Disclosure of Invention
The invention overcomes the defects of the prior art, provides a device and a method for suppressing the noise of the weak magnetic signal and extracting the signal under the geomagnetic background field, and adopts a method for improving the relative movement speed between the magnetic target and the weak magnetic detection based on the combination of the weak magnetic detection technology and the filtering technology so as to increase the frequency of the magnetic signal of the target.
In the detection process, because the geomagnetic signal is near the frequency of 0-0.15Hz, the frequency of the target signal is increased, so that the weak magnetic signal and the geomagnetic background field are separated from the frequency spectrum of the target signal at a position (above 0.15 Hz) with relatively high frequency, and then the geomagnetic noise is filtered by adopting a high-pass filter, thereby achieving the purposes of noise suppression and signal extraction.
The basic principle of the invention is mainly based on the following points:
1. magnetic signal detection principle: ferromagnetic object can produce the disturbance to surrounding magnetic field, when a detected object passes through the probe, can produce a certain amount of magnetic field disturbance to the magnetic field around the probe, and the probe can sense the change intensity in magnetic field this moment, produces the signal of telecommunication and passes back the back-end circuit as the detection result and shows.
2. Signal filtering principle: signal filtering is an operation of filtering out specific band frequencies in a signal, and is an important measure for suppressing and preventing interference. Is a probability theory and method for estimating a random process related to a certain random process according to the result of observing the random process. A technique for extracting a desired signal from a received signal containing interference.
3. The relative movement speed between the detected object and the detection probe is increased, the magnetic disturbance change speed is accelerated, the target signal frequency spectrum is moved towards the high-frequency direction, the frequency spectrum of the noise and the target signal is separated by improving the target signal frequency spectrum, and the required signal is extracted through a filtering technology, so that the noise is suppressed.
The technical solution of the invention is as follows:
a device for suppressing and extracting weak magnetic signal noise under a geomagnetic background field is characterized in that: the device comprises a magnetic detector, a magnetic sensor and a signal processing unit, wherein the magnetic detector is used for detecting weak magnetic signals;
the data acquisition card is used for acquiring signals of the magnetic detector and transmitting the signals to the spectrum analyzer; and
and the spectrum analyzer is used for performing spectrum analysis and corresponding signal filtering processing on the acquired signals.
The magnetic detector and the object to be detected move relatively.
The object to be measured has a speed V along the X-axis direction1Movement of said magnetic detector in the direction of the-X axis at a speed V2Moving, the relative speed between the object to be measured and the magnetic detector is V ═ V1+V2。
The X-axis direction is a horizontal direction or a vertical direction.
The data acquisition card obtains the weak magnetic signals at equal time intervals, the spectrum analyzer performs Fourier transformation on the acquired data to obtain spectrum data, and the data is filtered to obtain the weak magnetic signals of the object to be detected.
The magnetic detector, the data acquisition card and the spectrum analyzer are sequentially connected and placed on the mobile platform.
The method for suppressing the noise of the weak magnetic signal and extracting the signal by using the device for suppressing the noise of the weak magnetic signal and extracting the signal under the geomagnetic background field is characterized by comprising the following steps of:
step 1) the relative movement speed of an object to be detected and a magnetic detector is increased, and the object to be detected is subjected to magnetic detection through the magnetic detector to obtain a weak magnetic signal;
step 2) the data acquisition card transmits the acquired weak magnetic signals to a spectrum analyzer for spectrum analysis, and low-frequency-band signal quantity and high-frequency-band signal quantity interfered by geomagnetic noise are separated;
and 3) carrying out high-pass filtering on the high-frequency-band signal quantity to obtain a detection target signal.
The low-frequency-band semaphore is 0-0.15Hz, and the high-frequency-band semaphore is 2-5 Hz.
Compared with the prior art, the invention has the following technical effects:
(1) by improving the relative speed between the detected target and the magnetic detector, the magnetic disturbance change speed is accelerated, the frequency of the detected target signal is effectively improved, and the detected target signal and the low-frequency geomagnetic noise signal are effectively separated on a frequency spectrum. Filtering the separated signals to realize noise suppression of the geomagnetic background field;
(2) the method is easy to realize, can inhibit geomagnetic background field noise in real time, and increases the sensitivity and the real-time analysis capability of weak magnetic detection.
Drawings
Fig. 1 is a schematic structural diagram of a weak magnetic signal noise suppression and signal extraction apparatus in a geomagnetic background according to the present invention.
FIG. 2 is a diagram of time domain and frequency domain signals when a magnetic detector and a detection target are simulated to move relatively, wherein (a) is a time domain signal corresponding to a relative velocity of 20m/s between the magnetic detector and the detection target, and (b) is a frequency domain signal corresponding to a relative velocity of 20m/s between the magnetic detector and the detection target; (c) the time domain signal (d) corresponding to the relative motion speed of the magnetic detector and the detection object being 200m/s is the frequency domain signal corresponding to the relative motion speed of the magnetic detector and the detection object being 200m/s
In the figure: 1-magnetic detector, 2-detecting target object, 3-data acquisition card, 4-spectrum analyzer, 5-mobile platform, V1-detecting the direction of the speed of movement of the target object, V2Direction of magnetic probe speed of movement
Detailed Description
The present invention will be further described with reference to the following examples and drawings, but the scope of the present invention should not be limited thereto.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a device for suppressing noise of weak magnetic signals and extracting signals in a geomagnetic background according to the present invention, and it can be seen from the diagram that the method for suppressing noise of weak magnetic signals and extracting signals in a geomagnetic background according to the present invention includes a probe 1, a target object 2 to be detected, a data acquisition card 3, a spectrum analyzer 4, and a mobile platform 5. By improving the relative speed of the detection target and the detection probe in the movement direction, the noise suppression of the weak magnetic target signal under the geomagnetic background field is realized, and the target object signal is effectively extracted.
The method for suppressing the noise of the weak magnetic signal and extracting the signal under the geomagnetic background field comprises the following steps:
1) the detected target is a ferromagnetic object, and the vertical distance between the position of the detected target and the position of the magnetic detector during movement is 100M;
2) when the detection starts, the detection target moves at 10m/s along the X-axis direction, the detection probe moves at 10m/s along the-X-axis direction, the relative speed is 20m/s, and weak magnetic signal acquisition is carried out on the target object; then, the detection target moves at 10m/s along the X-axis direction, the detection probe moves at 190m/s along the-X-axis direction, the relative speed is 200m/s, and the weak magnetic signal acquisition is carried out on the target object again;
3) carrying out spectrum analysis on data signals returned by the probe, and separating geomagnetic noise interference signal quantity of 0-0.15Hz and detection target signal quantity of more than 0.15Hz in a relatively high frequency band;
4) and carrying out high-pass filtering on the analyzed signals by using a filtering technology, and separating the detection target signals of a high frequency band by using a high-pass filter with the frequency being more than 0.3Hz to obtain the detection target signals.
Comparing signal frequency spectrums before and after the relative movement speed of the detected object and the magnetic detector is increased by 10 times through simulation steps 2) and 3), and obtaining the method shown in figure 2, it can be seen that through the method for increasing the relative speed, the target signal can be separated from the geomagnetic signal on the frequency spectrum only when the relative speed is more than 200m/s
5) When the detection target is a ferromagnetic object, the detection probe moves at 0m/s along the X-axis direction, the detection probe moves at 200m/s along the-X-axis direction, the relative speed is 200m/s, and weak magnetic signal acquisition is carried out on the target object; and the detection target moves at 200m/s along the X-axis direction, the detection probe moves at 0m/s along the-X-axis direction, the relative speed is 200m/s, and weak magnetic signal acquisition is carried out on the target object. Thus, when the detection relative speed exceeds 200m/s, the frequency spectrum of the target signal can be improved, the target signal is separated from the 0-0.15Hz frequency band of the geomagnetic noise, and the target signal is extracted.
The invention has the advantages of noise suppression of weak magnetic signals under a geomagnetic background field, effective extraction of target signals, convenient system integration, and high speed and efficiency.
Claims (6)
1. A device for suppressing and extracting weak magnetic signal noise under a geomagnetic background field is characterized in that: comprises a magnetic detector (2) for detecting weak magnetic signals;
the data acquisition card (3) is used for acquiring signals of the magnetic detector (2) and transmitting the signals to the spectrum analyzer (4); and
the spectrum analyzer (4) is used for carrying out spectrum analysis and corresponding signal filtering processing on the acquired signals;
the magnetic detector (2) and the object (1) to be detected move relatively, and the object (1) to be detected moves along the X-axis direction at the speed V1Moving said magnetic detector (2) along-X direction at a speed V2When the object (1) moves, the relative speed V between the object (1) and the magnetic detector (2) is equal to V1+V2；
By increasing the relative speed between the detected target and the magnetic detector, the magnetic disturbance change speed is accelerated, the frequency of the detected target signal is effectively improved, and the detected target signal and the low-frequency geomagnetic noise signal are effectively separated on a frequency spectrum.
2. The apparatus for suppressing and extracting weak magnetic signal noise under geomagnetic background field according to claim 1, wherein: the X-axis direction is a horizontal direction or a vertical direction.
3. The apparatus for suppressing and extracting weak magnetic signal noise under geomagnetic background field according to claim 1, wherein: the data acquisition card (3) obtains weak magnetic signals at equal time intervals, the spectrum analyzer (4) performs Fourier change on the acquired data to obtain spectrum data, and the data is filtered to obtain the weak magnetic signals of the object to be detected.
4. The apparatus for suppressing and extracting weak magnetic signal noise under geomagnetic background field according to claim 1, wherein: the magnetic detector (2), the data acquisition card (3) and the spectrum analyzer (4) are sequentially connected and placed on the mobile platform.
5. The method for suppressing weak magnetic signal noise and extracting signal using the device for suppressing weak magnetic signal noise and extracting signal in geomagnetic background field as claimed in claim 1, wherein the method comprises the following steps:
step 1) the relative movement speed of an object to be detected (1) and a magnetic detector (2) is increased, and the object to be detected (1) is subjected to magnetic detection through the magnetic detector (2) to obtain a weak magnetic signal;
step 2), the data acquisition card (3) transmits the acquired weak magnetic signals to a spectrum analyzer (4) for spectrum analysis, and low-frequency-band signal quantity and high-frequency-band signal quantity of geomagnetic noise interference are separated;
and 3) carrying out high-pass filtering on the high-frequency-band signal quantity to obtain a detection target signal.
6. The method for suppressing noise and extracting weak magnetic signals according to claim 5, wherein the low-frequency signal amount is 0-0.15Hz, and the high-frequency signal amount is 2-5 Hz.
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