A directional radiation source positioning method combining time difference method and time reversal technology

Abstract

The present invention relates to the field of electromagnetic radiation source positioning, and in particular to a directional radiation source positioning method combining a time difference method and a time inversion technology, comprising: S1, selecting a random observation point r in a plurality of regions; m (x m ,y m ) receives the electromagnetic radiation time domain full-wave signal and records the instantaneous electric field signal E(r m ,t); S2, for random observation point r m (x m ,y m )The received signal E(r m ,t) Extract the time t corresponding to the peak point m , use the TDOA method to pre-position, obtain the predetermined site #imgabs0#S3, take the predetermined site #imgabs1# as the center, and use the EMTR technology to locate the radiation source position near the predetermined site #imgabs2#. The present invention uses the TDOA technology for pre-positioning and the EMTR technology for precise positioning, effectively combining the advantages of the two, overcoming the adverse effects of directional radiation characteristics on TDOA, and making up for the shortcomings of the traditional EMTR technology that is time-consuming and has a large memory requirement.

Description

Technical Field

[0001] The invention relates to the field of electromagnetic radiation source positioning, and in particular to a directional radiation source positioning method combining a time difference method and a time inversion technology. Background Art

[0002] Intentional Electromagnetic Interference (IEMI) is receiving increasing attention in the field of electromagnetic compatibility. IEC61000-2-13 defines IEMI as electromagnetic energy intentionally generated by humans and introduced into electrical and electronic systems, which in turn causes adverse effects on the systems, ranging from signal interference and logic confusion to load short circuit and insulation breakdown. It can generally be divided into two categories: radiation and conducted interference. The former usually refers to high-power microwave radiation sources, which are composed of pulse generators and high-power radiating antennas. It has the characteristics of long action distance, wide spectrum components, and strong directivity, and therefore receives more widespread attention.

[0003] In order to avoid the threat posed by IEMI radiation sources, accurate positioning and then taking effective measures to prevent them are the first feasible measures. At present, the methods used for spatial positioning of radiation sources mainly include Direction of Arrival (DOA), Received Signal Strength Indication (RSSI), Time of Arrival (TOA), Time Difference of Arrival (TDOA), etc., which are positioned by extracting characteristic information such as the angle difference, energy difference, and time difference of the signal generated by the radiation source to reach the measuring point. Generally speaking, the above algorithms usually regard the radiation source as a non-directional point source during use, and do not consider the impact of radiation directionality. However, when applied to the positioning of IEMI radiation sources, it is considered that such radiation sources are usually formed by radiating antennas with strong directivity, and the antenna gain is related to the radiation direction and signal frequency.

[0004] Reference Figure 1 , usually the radiation signal contains multiple frequency components, and the attenuation in different directions and frequencies is not consistent, which then forms a strong directional radiation characteristic, making the waveform characteristics of the time domain response signal of the receiving antenna at different positions inconsistent, which makes it difficult for the above method to extract accurate waveform information and produce positioning errors. Therefore, for IEMI radiation sources with extremely strong directivity, an accurate positioning method is urgently needed. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a directional radiation source positioning method combining a time difference method and a time inversion technology.

[0006] The present invention is achieved through the following technical solutions:

[0007] A directional radiation source positioning method combining a time difference method and a time inversion technique comprises the following steps:

[0008] S1, select random observation points r in multiple regions m (x m ,y m ) receives the electromagnetic radiation time domain full-wave signal and records the instantaneous electric field signal E(r m ,t), where x m ,y m is the coordinate point of the random observation point, m is the sequence number of the random observation point, t∈[t s ,t s +T],t s is the measurement start time, T is the signal sampling record length;

[0009] S2, for random observation point r m (x m ,y m ) received instantaneous electric field signal E(r m ,t) Extract the peak point and the time t corresponding to the peak point m , use the TDOA method to pre-position and obtain the predetermined position is the coordinate point of the predetermined site;

[0010] S3, with a predetermined site Centered at a predetermined location The radiation source is located nearby using EMTR technology.

[0011] Preferably, in S1, the random observation point r m (x m ,y m ) is greater than or equal to three.

[0012] Preferably, in S2, the predetermined site By taking any three random observation points r m (x m ,y m ) are combined to obtain the calculation formula:

[0013]

[0014] Where c is the speed of light; m1, m2 and m3 are the serial numbers of random observation points respectively.

[0015] Preferably, in S3, the following steps are included:

[0016] S31, at the predetermined site Select the estimated radiation source position r n (x n ,y n ), where n is the number of the guessed radiation source, n = 1, 2, 3, ..., N, N is a constant; and a random observation point r is obtained m (x m ,y m ) and the estimated radiation source position r n (x n ,y n ) m ,r n );

[0017] S32, at random observation point r m (x m ,y m ) is the time-reversed signal E TR (r m ,Tt) is transmitted back to the estimated radiation source position r n (x n ,y n ), and calculate each random observation point r m (x m ,y m ) is sent back to the estimated radiation source position r n (x n ,y n ) of the superimposed signal E sum (r n ,t);

[0018] S33, using the superimposed signal E sum (r n ,t) Calculate the position r of each guessed radiation source n (x n ,y n ) is the energy P of the superimposed signal t (r n );

[0019] S34, for each guessed radiation source position r n (x n ,y n ) is compared with the energy of the superimposed signal at , and the point with the maximum energy is taken as the radiation source position, that is,

[0020] Preferably, in S31, the estimated radiation source position r n (x n ,y n ) is selected by: taking a predetermined site As the center, select the target area S, divide the target area S into grids with an interval of d, and the endpoints of the grids are the guessed radiation source positions r n (x n ,y n ).

[0021] Preferably, in S32, the time inversion signal E TR (r m ,Tt) is calculated by random observation point r m (x m ,y m )The received signal E(r m ,t) is obtained by time inversion within the acquisition time T.

[0022] Preferably, in S32, the time inversion signal E TR (r m ,Tt) keeps the signal amplitude unchanged during the return process.

[0023] Preferably, in S32, the r n (x n ,y n ) at the superimposed signal E sum (r n ,t) is calculated as:

[0024]

[0025] In the formula, d(r m ,r n ) represents the observation point r m (x m ,y m ) and the estimated radiation source position r n (x n ,y n ), c represents the speed of light; M represents the number of guessed radiation sources, M=N.

[0026] Preferably, in S33, the estimated radiation source position r n (x n ,y n ) is the energy P of the superimposed signal t (r n ) is calculated as:

[0027]

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention effectively combines the advantages of the two by using TDOA technology for pre-positioning and EMTR technology for precise positioning, which not only overcomes the adverse effects of directional radiation characteristics on TDOA, but also makes up for the shortcomings of traditional EMTR technology that is time-consuming and has a large memory requirement.

[0030] By extracting the time information corresponding to the peak value and using the TDOA method for pre-positioning, we can obtain rough information about the target source position, narrow the range of the radiation source position, facilitate precise positioning in the next step, and improve calculation efficiency.

[0031] In the final positioning, the time and space adaptive focusing principle of time inversion technology is utilized. Different from the traditional method of judging and analyzing the details of the radiation signal, the full-wave signal characteristics are effectively utilized by injecting it in a holistic manner for inversion calculation, avoiding problems such as misjudgment of signal arrival time and difficulty in extracting signal features.

[0032] The present invention can effectively utilize the directional radiation characteristics brought by the radiation source, and avoid the accuracy error problem caused by extracting information such as time difference, energy difference, etc. between signals received at multiple measuring points.

[0033] Furthermore, no less than 3 observation points are provided for receiving the electromagnetic radiation time-domain full-wave signal generated by the radiation source.

[0034] Furthermore, the time-reversed signal E TR (r m ,Tt) in the process of returning, the signal amplitude is kept unchanged in order to reduce the positioning error and energy attenuation caused by the distance.

[0035] Furthermore, the maximum energy point of the superimposed signal after return is used as the corresponding radiation source position in order to synchronously analyze the radiation signals in different directions and reduce the differences in time domain waveforms, thereby reducing the influence of the directionality of the radiation source on the energy maximum point, which helps to reduce positioning errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the radiation pattern of the directional radiating antenna at each frequency;

[0037] Figure 2 It is a calculation flow chart of a directional radiation source positioning method combining the time difference method and the time inversion technology of the present invention;

[0038] Figure 3 is a schematic diagram of the locations of random observation points;

[0039] Figure 4 It is a radiation model;

[0040] Figure 5 Schematic diagram of the predetermined site;

[0041] Figure 6 Schematic diagram of time reversal operation;

[0042] Figure 7 It is the time domain waveform diagram in the radiation field;

[0043] Figure 8 is the spectrum diagram in the radiation field;

[0044] Fig. 9 Configure the diagram for the experiment;

[0045] Fig.10 is the waveform diagram of the received electric field;

[0046] Fig.11 is the normalized energy diagram. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0048] A directional radiation source positioning method combining the time difference method and time inversion technology, referring to Figure 2 , including the following steps:

[0049] S1, refer to Figure 3 , select random observation points r in multiple regions m (x m ,y m ) receives the electromagnetic radiation time domain full-wave signal and records the instantaneous electric field signal E(r m ,t), where x m ,y m is the coordinate point of the random observation point, m is the sequence number of the random observation point, t∈[t s ,t s +T],t s is the measurement start time, T is the signal sampling record length; random observation point r m (x m ,y m ) is greater than or equal to three.

[0050] Reference Figure 4 Since the radiation expression in the time domain requires convolution operation, the derivation process becomes complicated, so the method is derived in the frequency domain. The signal received by the mth measurement point is E(r m ,t), the corresponding frequency domain expression E(r m ,ω) is:

[0051]

[0052] Where: ——unit vector of the main polarization direction of the electric field; I(ω)——amplitude of the excitation signal, where ω represents the angular frequency; ψ(ω)——phase of the excitation signal; F(θ m ,φ m ,ω)——directivity factor; d(r s ,r m )——the distance between the radiation source and the mth measuring point; ——time delay, where k is the wave number in free space.

[0053] Directional radiation characteristics affect the amplitude and phase of the radiated field signal. For the amplitude, its directional gain is related to the frequency of the excitation signal and the angle between the radiation direction and the main axis of the radiating antenna. Figure 1 , when a wide-band pulse is used as the excitation, the electric field signal generated by the antenna radiation is Fourier transformed, and the gain of each frequency point will change with the change of the radiation direction, and usually the gain of each frequency point on the main axis is the largest. When the difference of the signal in the frequency domain is reflected in the time domain, the characteristics of the time domain waveform in different radiation directions will show differences including the rising edge and amplitude, which increases the difficulty of locating the radiation source. On the other hand, the directionality will also affect the phase of the field signal. However, considering that in free space, the detection array is usually located in the far field area far away from the radiation source, the size of the radiation source itself can be ignored, that is, it is regarded as a point source, and the equiphase surface generated by its radiation can be approximately regarded as a sphere. Therefore, the influence of the change in radiation direction on the phase can be ignored, and only the influence of the directional radiation characteristics on the amplitude is considered, that is, F(θ m ,φ m ,ω) contains only the real part.

[0054] S2, for random observation point r m (x m ,y m )The received signal E(r m ,t) Extract the time t corresponding to the peak point m , use the TDOA method to pre-position and obtain the predetermined position in, is the coordinate point of the predetermined location.

[0055] Predetermined site By taking any three random observation points r m (x m ,y m ) are combined to obtain the calculation formula:

[0056]

[0057] Where c is the speed of light.

[0058] S3, refer to Figure 5 , with a predetermined site Centered at a predetermined location Use EMTR technology to locate the radiation source nearby.

[0059] S31, at the predetermined site Select the estimated radiation source position r n (x n ,y n ), with a predetermined site As the center, select the target area S, divide the target area S into grids with an interval of d, and the endpoints of the grids are the guessed radiation source positions r n (x n ,y n ), where n is the number of the guessed radiation source, n = 1, 2, 3, ..., N, and a random observation point r is obtained. m (x m ,y m ) and the estimated radiation source position r n (x n ,y n ) m ,r n ).

[0060] S32, refer to Figure 6 , at a random observation point r m (x m ,y m ) is the time-reversed signal E TR (r m ,Tt) is transmitted back to the estimated radiation source position r with the signal amplitude unchanged n (x n ,y n ), time-reversed signal E TR (r m ,Tt) is calculated by random observation point r m (x m ,y m )The received signal E(r m ,t) is obtained by time inversion within the acquisition time T.

[0061] Time reversal is a time-reversal operation on the measured signal, which corresponds to a phase conjugate transformation in the frequency domain. Since the directivity factor only includes the real part, it is not affected by the time reversal. Therefore, the frequency domain expression E corresponding to the time reversal signal is * (r m ,ω) can be expressed as:

[0062]

[0063] Calculate each random observation point r m (x m ,y m ) is sent back to the estimated radiation source position r n (x n ,y n ) of the superimposed signal E sum (r n ,t), superimposed signal E sum (r n ,t) is calculated as:

[0064]

[0065] In the formula, d(r m ,r n ) represents the observation point r m (x m ,y m ) and the estimated radiation source position r n (x n ,y n ), c represents the speed of light; M represents the number of guessed radiation sources, M=N.

[0066] Superposition signal E sum (r n ,t) is expressed in frequency domain as E sum (r n ,ω):

[0067]

[0068] S33, using the superimposed signal E sum (r n ,t) Calculate the position r of each guessed radiation source n (x n ,y n ) is the energy P of the superimposed signal t (r n ), the energy of the superimposed signal P t (r n ) is calculated as:

[0069]

[0070] The energy P of the superimposed signal t (r n ) is calculated in the frequency domain as follows:

[0071]

[0072] It can be seen from the formula that P ω (r n ) and and The two items are related. Among them, only the second item is related to the guessed source point. When (n is an integer), P ω (r n ) reaches its maximum value. Considering that the radiation signal is usually a broadband signal, and P ω (r n ) and the wave number k are related to the frequency range, if and only if n = 0, that is, at this time (d is a constant value), P can be obtained ω (r n ) appears. At the position corresponding to this value, all the return signals are superimposed in phase, so the energy reaches the maximum value.

[0073] According to Parsval's theorem, the total energy of a signal can be calculated by integrating the energy per unit time over the entire time, or by integrating the energy per unit frequency over the entire frequency range. Therefore, the energy can be directly solved by superimposing the signal in the time domain without the need for Fourier transform, which effectively reduces the difficulty of calculation.

[0074] S34, for each guessed radiation source position r n (x n ,y n ) is compared with the energy of the superimposed signal at , and the point with the maximum energy is taken as the radiation source position, that is,

[0075] Example

[0076] (1) Experimental configuration: The experimental environment is set in an electromagnetic compatibility darkroom with a length of 11m, a width of 5.9m and a height of 6.3m. The radiation system includes an ultra-wideband pulse source and an IRA radiation antenna. The IRA radiation antenna is a typical IEMI directional radiation antenna with a radiation frequency band of 10MHz-2GHz. It can generate a radiation electric field with a potential of about 3kV and a 3dB upper limit frequency of 1GHz under far-field conditions. Figure 7 and Figure 8 They are the time domain waveform and spectrum of the radiation field at a distance of 4m from the radiation system.

[0077] The measurement system consists of a TEM horn receiving antenna, a transmission cable, an attenuator and an oscilloscope. It can monitor the electric field waveform in the irradiated space in real time, measure the electric field peak value exceeding 100kV / m, and the bandwidth can reach several GHz, meeting the test requirements for the above-mentioned radiation signals.

[0078] (2) Signal reception, see Fig. 9In the experiment, the focus of the radiating antenna is located at (0, 0), and the main axis of the antenna is set to deviate from the x-axis by 3°. The receiving array consists of three TEM electric field antennas D1, D2 and D3, which are located at (3.6, 1.5), (4.6, 0) and (3.6, -1.5) respectively. Since the polarization direction of the electric field generated by the radiating system is perpendicular to the ground under far-field conditions, the polarization direction of the receiving antenna is set to be consistent with the direction of the electric field.

[0079] Fig.10 The radiated electric field waveform measured by the receiving array. It can be seen that due to the influence of the radiating antenna directivity and the distance between the measuring point and the radiation source, there are differences in the amplitude and front edge of the received waveform, which is also the reason why traditional TOA and other methods have positioning errors.

[0080] (3) Pre-positioning, obtaining the peak time of each measurement signal, the peak time of the received signals of D1, D2 and D3 are 1.25ns, 3.8ns and 1ns respectively. Based on the measurement signal and the position of the measurement point, the coordinates of the predetermined position are solved by the TDOA method as (-2, -0.15).

[0081] (4) Accurate positioning, taking the predetermined site (-2, -0.15) as the center, select the area x∈(-5,1), y∈(-3,3) as the target area. Considering the limitation of computer memory, take d=0.02m as the interval for grid division, and all the points in it are used as the guessed radiation source position for calculation. Fig.11 , an accurate positioning model was established using MATLAB. Based on the normalized inversion of the EMTR method for finding the maximum energy position, the maximum energy point is located at (-0.28, 0.1), and its positioning error is 0.3m. As can be seen from Figure 9, the distance between the radiation system and the measurement point is less than 5m. Compared with the size of the antenna itself, its radiation does not fully meet the far-field conditions. Therefore, the error is within an acceptable range.

Claims

1. A directional radiation source positioning method combining the time difference method and the time inversion technology, characterized in that: The following steps are involved: S1, for IEMI radiation sources with strong directivity, select random observation points in multiple areas Receive electromagnetic radiation time domain full-wave signals and record the instantaneous electric field signals generated by the radiation source ,in, x m , y m is the coordinate point of the random observation point, m is the sequence number of the random observation point, , is the measurement start time, is the signal sampling record length; S2, for random observation points The instantaneous electric field signal received Extract the peak point and the time corresponding to the peak point , use the TDOA method to pre-position and obtain the predetermined position ,in, , is the coordinate point of the predetermined site; S3, with a predetermined site Centered at a predetermined location The EMTR technology is used nearby to determine the location of the radiation source, specifically: S31, at the predetermined site Select the estimated radiation source location ,in, n To guess the serial number of the radiation source, , N is a constant; and obtain random observation points and guessing the location of the radiation source Distance ; The estimated radiation source location The selection steps are: Center, select the target area S ,Will Target area S Divided into intervals of The endpoints of the grid are the guessed radiation source locations. ; S32, at random observation points Time Reversed Signal Return to the estimated radiation source location , and calculate each random observation point Return to the estimated radiation source location The superimposed signal ; The time-reversed signal By random observation points The signal received Perform time inversion within the acquisition time T to obtain; the time inversion signal Keep the signal amplitude unchanged during the return process; The estimated radiation source position The superimposed signal The calculation formula is: ； In the formula, Indicates observation point The estimated radiation source location The distance represents the speed of light; M Indicates the number of guessed radiation sources, M = N ; S33, using superimposed signal Calculate the positions of each guessed radiation source The energy of the superimposed signal ; The estimated radiation source position The energy of the superimposed signal The calculation formula is: ； S34, for each guessed radiation source position The energy of the superimposed signal at is compared, and the point with the maximum energy is taken as the radiation source position, that is, .

2. The directional radiation source positioning method combining the time difference method and the time reversal technology according to claim 1 is characterized in that: In S1, the random observation point The number is greater than or equal to three.

3. The directional radiation source positioning method combining the time difference method and the time reversal technology according to claim 2 is characterized in that: In S2, the predetermined site By taking any three random observation points The calculation formula is: Where c is the speed of light; m 1. m 2 and m 3 are the serial numbers of the random observation points.

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