Radio frequency current non-contact detection method based on space double magnetic field components

Abstract

The invention discloses a radio frequency current non-contact detection method based on space double magnetic field components. The method comprises the following steps: measuring magnetic field distribution on the surface of a to-be-detected device by using a space double magnetic field component probe; expanding the magnetic field plane under the condition of judging that the boundary of the measurement plane cuts off the magnetic field distribution; establishing a relationship between current and magnetic field distribution in a frequency domain space, solving Green functions under a static current hypothesis and a radio frequency current hypothesis, establishing a Tikhonov regularization cost function, and respectively obtaining current solutions under the static current hypothesis and the radio frequency current hypothesis by minimizing the cost function; taking the part exceeding the mean value in the current solution under the static current hypothesis as a static current distribution area, taking the static current distribution area as a mask to act on the current solution under the radio frequency current hypothesis, and filtering current artifacts; and extracting the current distribution in the magnetic field plane before expansion as the final current distribution of the radio frequency current. According to the invention, non-contact accurate imaging of radio frequency current can be realized in a wide frequency band.

Description

Technical Field

[0001] This invention belongs to the field of electronic device fault detection technology, specifically relating to a non-contact detection method for radio frequency current based on spatial dual magnetic field components. Background Technology

[0002] With the rapid development of the integrated circuit industry, the structure of electronic devices is becoming increasingly complex. This often leads to uncertainty about the location and cause of faults when they occur in circuits. Traditional detection methods typically utilize the physical field radiated by the device, using prior information to analyze the fault and determine its type and location. This relies on researchers' thorough understanding of the fault type, hindering the further promotion of fault detection technology. However, detecting the current distribution in a circuit can quickly and intuitively pinpoint the fault location, simplifying the testing process. Therefore, achieving non-contact current detection is crucial for electromagnetic compatibility analysis and fault detection of circuits.

[0003] Currently, researchers have developed numerous technologies for non-contact current detection. Among them, time-domain reconstruction can detect current signal waveforms at a single point, but it cannot yet achieve regional current detection. Fourier space reconstruction is a method for regional current imaging. It transforms complex convolution calculations in real space into simple multiplication and addition operations in Fourier space by applying Piersa's law to Fourier transform, thus accelerating the process. However, this method requires empirical selection of reconstruction parameters, and the current imaging results are easily affected by electromagnetic noise, test height, and other factors. Furthermore, when reconstructing radio frequency current using this method, the current is typically treated as static current, which can lead to errors. Summary of the Invention

[0004] The purpose of this invention is to provide a non-contact detection method for radio frequency current based on spatial dual magnetic field components, which can achieve accurate non-contact imaging of radio frequency current over a wide frequency band.

[0005] To achieve the above objectives, one aspect of the present invention provides a non-contact radio frequency current detection method based on two spatial magnetic field components, comprising: Step S1: Measure the magnetic field distribution on the surface of the device under test using a spatial dual magnetic field component probe to obtain two orthogonal magnetic field components; Step S2: Determine whether the boundary of the measurement plane interrupts the magnetic field distribution. If the boundary of the measurement plane interrupts the magnetic field distribution, expand the magnetic field plane to make the current at the boundary continuous. Step S3: Based on Maxwell's equations and the method of images, establish the relationship between the current and magnetic field distribution in the frequency domain, solve the Green's function under the static current assumption and the Green's function under the radio frequency current assumption, establish the Tikhonov regularization cost function containing the Green's function, and obtain the current solutions under the static current assumption and the radio frequency current assumption by minimizing the cost function. Step S4: Using the masking method, the portion of the current solution under the static current assumption that exceeds its mean value is taken as the static current distribution region. The static current distribution region is used as a mask to act on the current solution under the radio frequency current assumption to filter out current artifacts and obtain the current distribution of the radio frequency current. Step S5: Extract the current distribution in the magnetic field plane before expansion as the final current distribution of the radio frequency current.

[0006] According to the above-described aspect of the present invention, the non-contact detection method for radio frequency current based on spatial dual magnetic field components can achieve accurate non-contact imaging of radio frequency current over a wide frequency band. Attached Figure Description

[0007] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 This is a schematic diagram of the composition of a space dual magnetic field component detection system according to an embodiment of the present invention; Figure 2 This is a flowchart of a magnetic field inversion current algorithm according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a serpentine microstrip line sample for verification according to an embodiment of the present invention; Figure 4 This is a comparison diagram of the magnetic field distribution obtained by simulation software at 1GHz in one embodiment of the present invention and the magnetic field distribution detected by the present invention; Figure 5 This is a comparison diagram of the current distribution reconstructed by the conventional method and the method of the present invention at 1GHz, according to an embodiment of the present invention. Detailed Implementation

[0008] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0009] An embodiment of the present invention provides a non-contact detection method for radio frequency current based on spatial dual magnetic field components. The method of the present invention includes two parts: dual magnetic field component detection (corresponding to step S1) and current reconstruction based on dual magnetic field components (corresponding to steps S2 to S5).

[0010] To avoid current errors introduced by current reconstruction using a single magnetic field component and displacement errors caused by single-horizontal magnetic field component detection, this invention uses a spatial dual magnetic field component probe, which can realize dual magnetic field components H in the x and y directions within the GHz band. x H y Simultaneous detection. Therefore, this invention constructs such... Figure 1 The illustrated space dual magnetic field component detection system (near-field scanning system) includes a space dual magnetic field component probe, a three-axis displacement stage for controlling the probe's position, a network analyzer for receiving the probe's output signals, and a control computer for controlling the movement of the displacement stage's robotic arm. This invention achieves detection of the space dual magnetic field components H using the space dual magnetic field component probe. x H y Simultaneous detection. The sensing part of the probe consists of two mutually perpendicular metal loops. When a magnetic field component passes through the loops, an induced voltage is generated in the corresponding loop. The induced voltage can be expressed as follows: (1) In formula (1) This refers to the voltage signal generated by the probe due to the magnetic field component passing through the metal loop. This represents the total inductance of the loop. This indicates the total load of the loop. It refers to the angular frequency of the magnetic field. S This refers to the area of ​​the probe loop. It refers to magnetic permeability. H This refers to the magnetic field strength at the loop.

[0011] A network analyzer can be used to obtain the voltage values ​​output from the two loops of the dual magnetic field component probe. b 2. b 3. This voltage value corresponds to the magnetic field distribution at the center of the probe loop. Magnetic field probe calibration technology can convert the voltage output from the probe loop into the corresponding magnetic field value. , : (2) in, , Two magnetic field components , The corresponding calibration coefficient.

[0012] By fixing the probe to the robotic arm of the displacement stage, a region of the magnetic field above the device under test can be scanned. During the magnetic field scanning process, the sample is first stably fixed on the displacement stage and powered normally to enable operation. Then, the size of the scanning area and the scanning step size are set via a computer control program. After starting the scanning program, the computer controls the robotic arm of the displacement stage to move the probe point-by-point, scanning the magnetic field distribution on the surface of the device under test, and transmitting the voltage signal output by the probe to the network analyzer. Finally, magnetic field probe calibration technology converts the voltage signal into a near-field magnetic field distribution.

[0013] The magnetic field distribution H was obtained through a space dual magnetic field component detection system. x H y Subsequently, this invention reconstructs the radio frequency current in the device under test using a magnetic field inversion current algorithm. The flowchart of the dual-space magnetic field inversion current algorithm of this invention is as follows: Figure 2 As shown. To achieve accurate reconstruction of the radio frequency (RF) current, this invention establishes the relationship between the RF magnetic field and the RF current using Maxwell's equations. To reduce the errors caused by the empirical selection of filtering parameters in traditional methods, this invention applies a Tikhonov regularization cost function in both magnetic field directions to constrain the current distribution, and uses a generalized cross-validation method to select the optimal regularization parameter in the regularization cost function. Furthermore, this invention employs the extended window method and the mask method to further filter out current artifacts. The steps of the dual-space magnetic field inversion current algorithm of this invention are as follows.

[0014] Step 1 (corresponding to step S2): Set the extended plane according to the boundary conditions The extended magnetic field plane is primarily used to address the current artifact problem caused by incomplete magnetic field information due to truncation at the boundary of the measurement plane. First, a judgment condition is set: whether the magnetic field is truncated at the boundary based on the presence of a magnetic field value at the boundary of the input magnetic field data (if the magnetic field value at the boundary is not 0, the magnetic field distribution is considered truncated). If the magnetic field distribution is considered truncated at the boundary of the measurement plane, the extended magnetic field plane method is used to make the magnetic field distribution at the boundary symmetrical. Specifically, the extended magnetic field distribution H is obtained by flipping the rows and columns. x H y The original magnetic field matrix H is expanded into a 3×3 magnetic field component matrix. , : (3) This is obtained by flipping column H. Obtained by flipping row H Obtained by flipping H rows and columns. The purpose of reversing the magnetic field is to make the current on the H boundary continuous.

[0015] Step 2 (corresponding to step S3): Establish the regularization cost function formula. Similar to the Fourier space reconstruction method, the relationship between current and magnetic field distribution in the frequency domain can be established based on Maxwell's equations and its image method: (4) The current distribution region is defined as a two-dimensional space and is assumed to consist of only two orthogonal components. , constitute, , , , They represent respectively to , , , The result after Fourier transform. Green's theorem can be expressed as: (5) This indicates that it includes the Green's function corresponding to the magnetic field and current. The result obtained after Fourier transform.

[0016] When the current is static current The value is consistent with the Fourier space reconstruction method.

[0017] (6) When the current is radio frequency current for: (7) Where u and v represent the results of Fourier transform of the real space coordinates x and y, respectively, and z represents the height of the probe, i.e., the magnetic field detection plane. is the vacuum permeability, k represents the wave number of the field in the corresponding propagation medium (the intrinsic wave number of the medium), and d represents the thickness of the test piece.

[0018] Establish the Tikhonov regularization cost function: (8) In formula (16), the Tikhonov cost function includes two terms: the first term is used to limit the difference between the actual current and the inverted current, and the second term is a regularization term to make the solution smoother. , This is the regularization parameter. By selecting an appropriate regularization parameter, ill-posedness in the computation process can be controlled. For regularization matrix, , The x and y direction current density distributions to be solved (the regularized solution). This is a convolution operator. The estimated solution that best approximates the true solution is obtained by minimizing the regularization cost function.

[0019] By solving for the minimum value of the two expressions in (16) respectively, we can obtain , Solution: (9) in, , The final reconstructed spatial domain current density distribution in the x and y directions, This is a two-dimensional inverse Fourier transform (converting the frequency domain result back to the spatial domain). , Measured magnetic field components , The two-dimensional Fourier transform.

[0020] for conjugate ( It is the Fourier transform of K. (This is the frequency domain, where K is the real number space) It is the Green's function in the frequency domain. , These are the regularization parameters for the two regularization cost functions. This invention uses generalized cross-validation (GCV) to automatically select the optimal regularization parameters.

[0021] Step 3 (corresponding to step S4): Use a masking method to remove current artifact distribution. After obtaining the current distribution using the input magnetic field distribution according to the static current assumption and the radio frequency (RF) current assumption respectively, if the current is static, the output of the static current assumption is directly used as the current solution output by the algorithm. If the current is RF, a masking method is used to treat the portion of the static current solution that exceeds its mean as the region of static current distribution, and this region is used as a mask to apply to the RF current solution, suppressing the spatial noise introduced by the mirror current term in the RF current assumption and filtering out current artifacts.

[0022] Step 4 (corresponding to step S5): Extract the current distribution in the original magnetic field plane as the final current distribution. Since the purpose of expanding the magnetic field plane in the first step is to resolve the current artifacts caused by the magnetic field cutoff at the boundary, the current distribution outside the original magnetic field plane obtained by expanding the magnetic field plane has no physical meaning. Therefore, it is necessary to extract the current within the original magnetic field plane as the final current solution.

[0023] To verify the effectiveness of the method in this invention, a serpentine microstrip line sample was designed. The magnetic field distribution at a specified height above the surface of the microstrip line sample was obtained sequentially using simulation software and a space dual-magnetic-field component detection system under the same settings (operating frequency, operating power, scanning area, scanning step size, and magnetic field plane height). The magnetic field was then input into an algorithm to reconstruct the current distribution within the microstrip line. The sample surface current density obtained by the simulation software under the same settings was used as a reference current density and compared with the current density reconstructed from the magnetic field of the simulation software and the space dual-magnetic-field component detection system to verify the effectiveness and accuracy of the design method of this invention.

[0024] Figure 3 This is a serpentine microstrip line sample used for verification, where W1=60mm, L2=12mm, and L3=3mm. P1 is connected to a network analyzer, and P2 is connected to a 50-ohm load. The dashed line represents the scanning area.

[0025] During the test, the network analyzer was set to a scanning frequency band of 100kHz-1.5GHz, BW=10kHz, and 1500 scanning points. 1GHz was chosen to demonstrate the effect of the method in this embodiment of the invention. The magnetic field image obtained by the simulation software at 1GHz is shown below. Figure 4 As shown in (a) and (b), the magnetic field images obtained by the magnetic field detection system of the present invention are as follows. Figure 4 As shown in (c) and (d), it can be observed that the magnetic field image detected by the magnetic field detection system is very close to the magnetic field image simulated by the simulation software. This indicates that the dual-space magnetic field detection system can detect magnetic field components. H x , H y Accurate measurement. To verify the accuracy of the reconstructed current using the method of this invention, the differences between the current distribution reconstructed by the Fourier space reconstruction method and the method of this invention based on the simulated magnetic field and the magnetic field detected by the magnetic field detection system, respectively, and the current distribution on the surface of the microstrip line sample simulated by the simulation software, were compared. The reconstructed current distributions of each method are shown below. Figure 5 As shown. Among them, Figure 5 (a) and (b) are the current distributions reconstructed by the Fourier space reconstruction method and the method of the present invention based on the simulated magnetic field, respectively. Figure 5 (c) represents the surface current distribution of the microstrip line sample obtained from simulation software. Figure 5 (d) and (e) represent the current distribution reconstructed from the magnetic field detected by the magnetic field detection system using the Fourier space reconstruction method and the algorithm of this invention, respectively. It can be observed that the algorithm of this invention achieves better results than the Fourier space reconstruction method in both simulation and magnetic field detection systems.

[0026] To more intuitively demonstrate the effect of the algorithm's reconstruction, MSD is used to represent the numerical difference between the reconstructed current and the reference current. MSD is a number greater than 0; the larger the MSD, the greater the difference between the reconstructed current and the reference current.

[0027] MSD is defined as follows: (10) In formula (18) This represents the current density distribution simulated by the simulation software. The algorithm reconstructs the current distribution. The calculation results are shown in Table 1. It can be seen that the algorithm of this invention achieves better results in both simulation and magnetic field detection systems.

[0028] Table 1. Reconstruction current results (MSD) of microstrip line samples

[0029] In summary, the non-contact radio frequency current detection method based on spatial dual magnetic field components of the present invention has the following beneficial effects: This invention reconstructs the radio frequency (RF) current in a device using a dual-component magnetic field probe, enabling non-contact imaging of the RF current. Firstly, compared to traditional magnetic field reconstruction current imaging methods, the advantages of this invention lie primarily in two aspects: the magnetic field acquisition method and the magnetic field reconstruction current calculation method. Regarding the magnetic field acquisition method, the dual-component magnetic field probe used in this invention not only avoids mathematical errors caused by vertical magnetic field detection but also avoids displacement errors introduced by rotating the probe during single-plane magnetic field measurement, saving detection time. From an algorithmic perspective, the algorithm of this invention can reconstruct a more accurate current distribution. Secondly, the algorithm of this invention introduces the Tikhonov regularization method and the GCV method during the reconstruction process to solve for the current, avoiding errors caused by empirical selection of filter parameters. Finally, this invention utilizes spatial dual magnetic field components to achieve non-contact imaging of the RF current. Compared to traditional methods, this invention not only avoids the selection of empirical parameters but also achieves more accurate RF current imaging.

[0030] This invention achieves radio frequency current imaging based on a dual magnetic field component probe, which can accurately image the surface current of microwave devices such as microstrip lines, antennas, and filters. It avoids the spatial position error introduced by adjusting the probe direction when using a single magnetic field component, thus saving test time.

[0031] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A non-contact radio frequency current detection method based on spatial dual magnetic field components, characterized in that, include: Step S1: Measure the magnetic field distribution on the surface of the device under test using a spatial dual magnetic field component probe to obtain two orthogonal magnetic field components; Step S2: Determine whether the boundary of the measurement plane interrupts the magnetic field distribution. If the boundary of the measurement plane interrupts the magnetic field distribution, expand the magnetic field plane to make the current at the boundary continuous. Step S3: Based on Maxwell's equations and the method of images, establish the relationship between the current and magnetic field distribution in the frequency domain, solve the Green's function under the static current assumption and the Green's function under the radio frequency current assumption, establish the Tikhonov regularization cost function containing the Green's function, and obtain the current solutions under the static current assumption and the radio frequency current assumption by minimizing the cost function. Step S4: Using the masking method, the portion of the current solution under the static current assumption that exceeds its mean value is taken as the static current distribution region. The static current distribution region is used as a mask to act on the current solution under the radio frequency current assumption to filter out current artifacts and obtain the current distribution of the radio frequency current. Step S5: Extract the current distribution in the magnetic field plane before expansion as the final current distribution of the radio frequency current.

2. The method as described in claim 1, characterized in that, In step S1, the device under test is fixed on the displacement stage, and the spatial dual magnetic field component probe is fixed on the robotic arm. The robotic arm drives the probe to scan the magnetic field distribution on the surface of the device under test point by point, and transmits the induced voltage signal output by the probe to the network analyzer to convert the voltage signal into magnetic field components.

3. The method as described in claim 2, characterized in that, The sensing element of the probe consists of two mutually perpendicular metal loops. When a magnetic field component passes through the loops, an induced voltage is generated in the corresponding loop. The voltage values ​​output by the two loops of the probe are obtained through a network analyzer. b 2. b 3. Convert the voltage output from the probe loop into the corresponding magnetic field component through probe calibration. , : in, , Magnetic field component , The corresponding calibration coefficient.

4. The method according to any one of claims 1-3, characterized in that, In step S2, the magnetic field distribution matrix after the magnetic field plane is expanded. , for: This is achieved by flipping the columns of the original magnetic field distribution matrix. The original magnetic field distribution matrix was obtained by performing a row flip. The original magnetic field distribution matrix was obtained by flipping its rows and columns. .

5. The method as described in claim 4, characterized in that, In step S3, the relationship between the current and magnetic field distribution in the frequency domain is as follows: in, , These are two orthogonal components of the current distribution. , The current distribution after the magnetic field plane is extended. , , , They represent respectively to , , , The result after Fourier transform, Green's theorem is expressed as: in, Representing the Green's function The result after Fourier transform.

6. The method as described in claim 5, characterized in that, Under the assumption of static current, The value is: Under the assumption of radio frequency current, The value is: Where u and v represent the results of Fourier transform of the real space coordinates x and y, respectively, and z represents the height of the magnetic field detection plane. is the vacuum permeability, k represents the intrinsic wavenumber of the medium, and d represents the thickness of the device under test.

7. The method as described in claim 6, characterized in that, The Tikhonov regularization cost function is: in, , These are the regularization parameters for the two regularization cost functions. For regularization matrix, , The x and y current distributions to be solved are shown. It is a convolution operator.

8. The method as described in claim 7, characterized in that, The optimal regularization parameter is selected using a generalized cross-validation method.

9. The method as described in claim 8, characterized in that, The current distribution is as follows: in, , The final reconstructed current distribution in the x and y directions, This represents the two-dimensional inverse Fourier transform. , Magnetic field component , Two-dimensional Fourier transform, for . conjugate.

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