Method for evaluating and correcting time delay synchronization of elements of three-dimensional ground penetrating radar array antenna

Abstract

The application discloses a kind of three-dimensional ground penetrating radar array antenna array element time delay synchronism evaluation and correction method, comprising the following steps: step 1, full reflection scene simulation in air medium:step 2, data acquisition: three-dimensional ground penetrating radar is opened, saves the data of all array elements of array antenna not less than 30 seconds;Step 3, data reorganization and interception;Step 4, array element time delay synchronism evaluation:step 5, each array element time delay synchronization correction coefficient calculation.The method disclosed in the application preliminarily establishes three-dimensional ground penetrating radar array antenna performance evaluation system, is the complement of general ground penetrating radar performance evaluation, makes up the existing evaluation method cannot accurately evaluate three-dimensional ground penetrating radar array antenna each array element synchronization degree, array element time delay difference size and whether it will affect the quality and display effect of subsequent various three-dimensional stereoscopic view.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ground penetrating radar, and particularly relates to a method for evaluating and correcting the time delay synchronization of array elements of a three-dimensional ground penetrating radar array antenna. BACKGROUND

[0002] Compared with the traditional two-dimensional ground penetrating radar, the three-dimensional ground penetrating radar can collect high-density, seamless spliced massive radar data, without causing the loss of underground information. Through the collected three-dimensional data, the spatial distribution characteristics of electromagnetic waves can be obtained, the three-dimensional data body formed can be horizontally sliced at any depth, vertically sliced at any position, and tilted profile displayed at any angle and direction, so as to realize the spatial characterization of underground targets. The three-dimensional ground penetrating radar has become the mainstream product in the industry due to its high efficiency and intuitiveness. The three-dimensional ground penetrating radar array antenna can often be combined for transmission and reception, that is, the signal transmitted by any array element can be received by other array elements. In operation, the electromagnetic wave is transmitted to the underground by a plurality of transmitting array elements controlled by a high-speed coaxial switch in a certain time sequence, and the echo signal is collected by the receiving array elements at the same time. The receiving characteristics of each array element are affected by the antenna manufacturing process, crosstalk between different array elements, various RF front ends and A / D devices themselves, and the fluctuation of the receiving characteristics is further introduced by the digital quadrature demodulation after A / D sampling. These factors cause the distortion of the transmission characteristics of the antenna array elements and the inconsistency of the time delay synchronization characteristics between the array elements, causing the time zero points of the three-dimensional data body to be inconsistent, and causing the strip-shaped or patch-shaped interference or artifacts to appear in the slice and profile images, which reduces the imaging quality of various targets and affects the accuracy of interpretation and evaluation.

[0003] Therefore, it is necessary to establish a three-dimensional ground penetrating radar performance evaluation system, in which the time delay synchronization of the array elements of the array antenna is an important evaluation index. The better the time delay synchronization of the array elements of the three-dimensional ground penetrating radar array antenna, the higher the quality of the profile images and three-dimensional stereoscopic views generated in each direction. Only when the time delay synchronization of the array elements of the three-dimensional ground penetrating radar array antenna is controlled or corrected to a certain range, can the subsequent target detection and recognition be guaranteed.

[0004] The patent "A ground penetrating radar antenna phase jitter evaluation method (CN113219423B)" discloses collecting a certain length of ground penetrating radar data, finding the sampling point number corresponding to the direct coupling wave or reflected wave, and performing operation on the extreme value and the average value of the sampling point number to obtain the ground penetrating radar antenna phase jitter. The disadvantage is that it starts from the phase stability and is only applicable to the evaluation of two-dimensional ground penetrating radar single antenna or the separate evaluation of multiple channels of three-dimensional ground penetrating radar array antenna. It cannot evaluate whether the signals between the array elements of the three-dimensional ground penetrating radar array antenna are synchronized and whether the time delays are consistent, and it cannot provide a quantitative correction coefficient. SUMMARY

[0005] The technical problem to be solved by this invention is to provide a method for evaluating and correcting the time delay synchronization of three-dimensional ground-penetrating radar array antenna elements.

[0006] The present invention adopts the following technical solution:

[0007] An improvement of the method for evaluating and correcting the time delay synchronization of three-dimensional ground-penetrating radar array antenna elements includes the following steps:

[0008] Step 1, Simulation of total internal reflection scenario in air medium:

[0009] Lay copper foil flat on the ground, place cubic foam in the center of the copper foil, and place the three-dimensional ground penetrating radar array antenna horizontally on top of the cubic foam with the antenna's radiating surface facing down and the center point of the antenna aligned with the center point of the copper foil.

[0010] Step 2, Data Collection:

[0011] Turn on the 3D ground-penetrating radar and save data for at least 30 seconds for all array elements of the antenna array.

[0012] Step 3, Data Reassembly and Extraction:

[0013] The data is arranged in the order of the array antenna elements, and the data for the first 10 seconds and the last 10 seconds of each element are removed, retaining only the intermediate data, thus obtaining the effective dataset for each element: {S1, S2, ..., S...} i S N}, where S i S represents the effective dataset of the i-th array element, where N is the total number of array antenna elements. The effective dataset of a single array element contains the received echo signals at several times: S i ={s i1 s i2 , ..., s ij , ..., s im}, where s ij This represents the received echo signal of the i-th array element at time j;

[0014] Step 4, Evaluation of array element time delay synchronization:

[0015] The effective dataset S of the i-th element is processed sequentially. i The received echo signal s at a single moment ij Analysis yields the time delay corresponding to the ground copper foil reflection wavelet at each moment for this array element: {tt i1 , tt i2 , ..., tt ij , ..., tt im}, where tt ijMeanTTi,j represents the time delay of the i-th array element in the j-th time receiving the echo signal reflected by the ground copper foil, and the mean value of the time delay of the ground copper foil reflection wavelet of the array element is obtained after averaging: MeanTTi i i1 i2 ij im

[0016] The mean values of the time delays of the ground copper foil reflection wavelets of all array elements are obtained respectively: [MeanTT1, MeanTT2, …, MeanTT i N max min mean

[0017] The time delay synchronization of the three-dimensional ground penetrating radar array antenna is represented as:

[0018]

[0019] Step 5, calculation of the time delay synchronization correction coefficient of each array element:

[0020] The correction coefficient corresponding to the i-th array element of the three-dimensional ground penetrating radar array antenna is: CoefTim i mean i After reverse compensation, the time delay synchronization correction is performed.

[0021] Further, in step 1, the top cross section of the cubic foam is larger than the bottom surface of the array antenna.

[0022] Further, in step 1, the height of the cubic foam is 2λ, and λ is the wavelength corresponding to the center frequency of the array antenna in the air medium.

[0023] Further, in step 1, the laying range of the copper foil exceeds the edge of the bottom surface of the cubic foam by 4λ in the length and width directions.

[0024] Further, in step 2, the corresponding array antenna default parameters are selected, preheated for ten minutes, and it is checked and confirmed that all array elements are in working condition, time trigger mode, and can normally receive and transmit signals.

[0025] The beneficial effects of the present application are:

[0026] ​​​​​​​​​​​​The method disclosed by the application preliminarily establishes a three-dimensional ground penetrating radar array antenna performance evaluation system, and is a supplement to general ground penetrating radar performance evaluation. The method makes up for the fact that the existing evaluation method cannot accurately evaluate the synchronization degree of each array element of the three-dimensional ground penetrating radar array antenna, the time delay difference between the array elements, and whether the time delay difference will affect the quality and display effect of subsequent three-dimensional views. Meanwhile, the method provides a previously-uninvolved correction coefficient calculation method, which can be used for reverse compensation.

[0027] The method disclosed by the application provides a basis for three-dimensional ground penetrating radar manufacturers to measure performance indicators, provides guidance for three-dimensional ground penetrating radar users to select and purchase equipment, and provides a reference for three-dimensional ground penetrating radar application parties to develop secondarily. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a horizontal cross-section view when the array element time delay synchronization of the three-dimensional ground penetrating radar array antenna is poor;

[0029] Figure 2 is a horizontal cross-section view when the array element time delay synchronization of the three-dimensional ground penetrating radar array antenna is poor;

[0030] Figure 3 is a flowchart of the method of the application;

[0031] Figure 4 is a schematic diagram of a total reflection simulation scene in an air medium;

[0032] Figure 5 is a ten-array element data set of the three-dimensional ground penetrating radar array antenna;

[0033] Figure 6 is a received echo signal diagram of a single time of a certain array element. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the application more clear and understandable, the application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application.

[0035] Figure 1 is a horizontal cross-section view when the array element time delay synchronization of the three-dimensional ground penetrating radar array antenna is poor; Figure 2 is a horizontal cross-section view when the array element time delay synchronization of the three-dimensional ground penetrating radar array antenna is poor.

[0036] Example 1 discloses an evaluation and correction method for array element time delay synchronization of a three-dimensional ground penetrating radar array antenna. In a static condition, the reflection waves of a same target of each array element of the three-dimensional ground penetrating radar array antenna are collected in a same time, the time delays of the reflection waves of each array element are counted respectively, the synchronization is calculated, and the synchronization correction coefficients of each array element of the array antenna are obtained.

[0037] As Figure 3 shown, the specific steps are as follows:

[0038] Step 1, total reflection field simulation in air medium:

[0039] As Figure 4 shown, the three-dimensional ground penetrating radar 400M array antenna is placed horizontally on a cross-section larger than the array antenna bottom surface of the cubic foam, the foam height is 150cm, and the array antenna with a center frequency of 400M corresponds to a wavelength of 75cm in air medium. The array antenna radiates downward, and the ground is flat and pasted with copper foil. In the length and width directions, the pasting range of the copper foil exceeds the edge of the antenna bottom surface by 300cm. The center point of the array antenna is aligned with the center point of the pasted copper foil;

[0040] Step 2, data acquisition:

[0041] Turn on the three-dimensional ground penetrating radar, select the corresponding array antenna default parameters, preheat for ten minutes, check that the 10 array elements are in working condition, time trigger mode, and can normally transmit and receive signals. At the same time, save the data of the 10 array elements for not less than 30 seconds;

[0042] Step 3, data reorganization and extraction:

[0043] Arrange the data in the order of the array antenna array elements, and respectively exclude the data of the beginning 10 seconds and the end 10 seconds of each array element, and only keep the data of the middle 10 seconds, so as to obtain the 10-array element effective data set as Figure 5 shown. As Figure 6 shown, the effective data set of a single array element contains several time receiving echo signals;

[0044] Step 4, array element time delay synchronization evaluation:

[0045] The effective data set of each array element is sequentially counted. For the effective data set of each array element, the receiving echo signal of a single time is analyzed in sequence. The time delay of the ground copper foil reflection wavelet of each time of the array element is obtained, and the average value of the time delay of the ground copper foil reflection wavelet of the array element is obtained. Thus, the time delay average values of the ground copper foil reflection wavelets of the 10 array elements [2.84ns, 3ns, 3.02ns, 2.84ns, 2.88ns, 2.84ns, 3.02ns, 3.02ns, 2.9ns, 2.88ns] are obtained, the maximum value of the time delay average values of the ground copper foil reflection wavelets of the 10 array elements is 3.02ns, the minimum value is 2.84ns, and the average value is 2.924ns. The array element time delay synchronization of the three-dimensional ground penetrating radar is about 0.534dB;

[0046] Step 5, calculation of time delay synchronization correction coefficient of each array element:

[0047] The synchronization correction coefficients corresponding to the 10 array elements of the three-dimensional ground penetrating radar array antenna 10 are [0.084 ns, -0.076 ns, -0.096 ns, 0.084 ns, 0.044 ns, 0.084 ns, -0.096 ns, -0.096 ns, 0.024 ns, 0.044 ns], and reverse compensation can be performed to correct the time delay synchronization.

Claims

1. A method for evaluating and correcting the time delay synchronization of three-dimensional ground-penetrating radar array antenna elements, characterized in that, Includes the following steps: Step 1, Simulation of total internal reflection scenario in air medium: Lay copper foil flat on the ground, place cubic foam in the center of the copper foil, and place the three-dimensional ground penetrating radar array antenna horizontally on top of the cubic foam with the antenna's radiating surface facing down and the center point of the antenna aligned with the center point of the copper foil. Step 2, Data Collection: Turn on the 3D ground-penetrating radar and save data for at least 30 seconds for all array elements of the antenna array. Step 3, Data Reassembly and Extraction: The data is arranged in the order of the array antenna elements, and the data for the first 10 seconds and the last 10 seconds of each element are removed, retaining only the intermediate data, thus obtaining the effective dataset for each element: {S1, S2, ..., S...} i S N }, where S i S represents the effective dataset of the i-th array element, where N is the total number of array antenna elements. The effective dataset of a single array element contains the received echo signals at several times: S i ={s i1 s i2 , ..., s ij , ..., s im }, where s ij This represents the received echo signal of the i-th array element at time j; Step 4, Evaluation of array element time delay synchronization: The effective dataset S of the i-th element is processed sequentially. i The received echo signal s at a single moment ij Analysis yields the time delay corresponding to the ground copper foil reflection wavelet at each moment for this array element: {tt i1 , tt i2 , ..., tt ij , ..., tt im }, where tt ij MeanTT represents the average time delay of the ground copper foil reflection in the echo signal received by the i-th array element at time j. i =mean(tt) i1 , tt i2 , ..., tt ij , ..., tt im ); Then, the mean time delay of the reflected wavelets from the ground copper foil of all array elements is obtained: [MeanTT1, MeanTT2, ..., MeanTT] i MeanTT N The maximum value among the mean time delays of the wavelet reflected by the ground copper foil of all array elements is MeanTT. max The minimum value is MeanTT min The average value is MeanTT mean ; The time delay synchronization of each element of a three-dimensional ground-penetrating radar array antenna is expressed as follows: Step 5, Calculation of time delay synchronization correction coefficients for each array element: The correction coefficient corresponding to the i-th element of the three-dimensional ground-penetrating radar array antenna is: CoefTim i =MeanTT mean -MeanTT i After reverse compensation, time delay synchronization correction was performed.

2. The method for evaluating and correcting the time delay synchronization of three-dimensional ground-penetrating radar array antenna elements according to claim 1, characterized in that: In step 1, the top cross-section of the cubic foam is larger than the bottom surface of the array antenna.

3. The method for evaluating and correcting the time delay synchronization of three-dimensional ground-penetrating radar array antenna elements according to claim 1, characterized in that: In step 1, the height of the cubic foam is 2λ, where λ is the wavelength of the array antenna center frequency corresponding to the air medium.

4. The method for evaluating and correcting the time delay synchronization of three-dimensional ground-penetrating radar array antenna elements according to claim 3, characterized in that: In step 1, the copper foil is laid beyond the bottom edge 4λ of the cubic foam in both length and width directions.

5. The method for evaluating and correcting the time delay synchronization of three-dimensional ground-penetrating radar array antenna elements according to claim 1, characterized in that: In step 2, select the default parameters for the corresponding array antenna, warm up for ten minutes, and check to confirm that all array elements are in working condition, in time-triggered mode, and can transmit and receive signals normally.

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