A radiation source modeling method for electronic devices in a shielding case

Abstract

The present invention discloses a method for modeling the radiation source of an electronic device in a shielding cover, which belongs to the field of constructing an equivalent model of an electromagnetic radiation source. The modeling method equates a real radiation source (electronic device / component, etc.) with an unknown structure to a virtual electromagnetic dipole array, and uses the dipole to simulate the electromagnetic coupling of the real radiation source in the shielding cover to its surrounding elements. First, the position and initial radiation intensity (dipole moment) of the dipole are calculated using the radiation electromagnetic field of the real source when there is no shielding cover, and then the radiation intensity of the dipole is adjusted using the leakage field of the real source when there is a shielding cover. Finally, the position and final radiation intensity of the dipole and the shielding cover are brought into a full-wave electromagnetic simulation model to calculate the coupling voltage / power of the dipole and the surrounding elements. The coupling voltage / power is the coupling voltage / power of the real source to the surrounding elements when the shielding cover is present. The modeling method of the present invention solves the problem that the traditional dipole method cannot accurately predict the electromagnetic coupling in the shielding cover.

Description

Technical Field

[0001] The present invention relates to the field of constructing equivalent models of electromagnetic radiation sources, and in particular to a radiation source modeling method for electronic devices in a shielding case. Background Art

[0002] Autonomous driving, high-performance computing, 5G communications, and artificial intelligence are enabling both known and unknown high-speed electronic devices to permeate the military, production, and everyday life. The operating frequencies of related circuits are constantly increasing, and their high-order harmonics have reached hundreds of GHz. This has led to component sizes comparable to electromagnetic wavelengths, making them unexpected "antennas." Electromagnetic radiation interference from high-speed circuits has become increasingly prevalent and serious. Faced with increasingly complex electronic products, traditional full-wave simulation methods are unable to accurately and quickly analyze electromagnetic interference issues. This is because full-wave simulation algorithms are extremely inefficient when dealing with complex multi-scale (board-level, device-level, and chip-level) problems. Near-field scanning technology offers significant advantages in addressing these challenges, enabling the diagnosis and location of electromagnetic interference issues even when device structural details are unknown. In particular, using near-field scanning electromagnetic fields, simplified equivalent models of real, complex radiation sources (such as a simple dipole array) can be constructed, enabling rapid quantitative analysis of electromagnetic interference issues in complex systems.

[0003] To reduce harmful electromagnetic radiation, radiation sources are often placed inside a shielding enclosure. Traditional equivalent dipole calculations are performed by scanning the electromagnetic field of the actual radiation source without the shielding enclosure. However, when placed inside the shielding enclosure, electromagnetic reflections within the enclosure can cause significant discrepancies between the electromagnetic field inside the enclosure and the actual radiation source. Summary of the Invention

[0004] In order to overcome the problem of large errors in the existing radiation source modeling of electronic devices inside the shielding cover, the present invention provides a two-step radiation source modeling method. The key point is to adjust the dipole moment of the virtual dipole by testing the leakage field of the radiation source outside the shielding cover, thereby improving the accuracy of the radiation source modeling inside the shielding cover.

[0005] The technical contents of the present invention are as follows:

[0006] A radiation source modeling method for an electronic device within a shielding case, comprising:

[0007] The radiation source of the electronic device in the shielding case is equivalent to a virtual electromagnetic dipole array, and an equivalent model is constructed based on the dipole radiation field;

[0008] The position and initial dipole moment of the dipole are calculated using the electromagnetic field of the real radiation source without a shielding cover.

[0009] The position and number of dipoles are fixed, and the leakage field of the real radiation source when the shield is in place is used to adjust the initial dipole moment of the dipole model inside the shield to obtain the final dipole moment of the dipole;

[0010] The dipole positions, final dipole moments, and shielding can are brought into the full-wave electromagnetic simulation model to calculate the coupling voltage or power between the dipole array and the components inside and outside the shielding can. The coupling voltage / power is the coupling voltage or power of the real radiation source to the surrounding components when the shielding can is present.

[0011] The present invention uses a virtual dipole to replace a real radiation source (a circuit device with an unknown structure), and calculates the position and dipole moment (radiation intensity of the dipole) of the virtual dipole in two steps.

[0012] The first step is to scan the real radiation electromagnetic field of the real radiation source when there is no shielding cover or the shielding cover is opened, and use the real radiation electromagnetic field as the equivalent radiation electromagnetic field in the equivalent model to reversely deduce the position and preliminary dipole moment of the virtual electromagnetic dipole corresponding to the real radiation source.

[0013] Specifically, optimization algorithms such as differential evolution are used to adjust the positions and dipole moments of the dipoles in the equivalent model of the electromagnetic dipole array, thereby obtaining the position and preliminary dipole moment of the virtual electromagnetic dipole corresponding to the real radiation source. This dipole moment is obtained in free space without a shielding cover, and its radiation field is the same as that of the real radiation source in free space without a shielding cover. However, when the dipole is placed inside a shielding cover, its radiation field differs significantly from the field of the real radiation source. This is because the dipole model is "transparent," meaning it can only radiate electromagnetic fields but not reflect them. Electromagnetic waves reflected multiple times within the shielding cover will "pass through" the dipole, but these waves will be reflected by the real radiation source.

[0014] The second step is to establish a simulation model of a virtual shielding cover + dipole array based on the position and initial dipole moment of the dipole, wherein the virtual shielding cover has the same shape and size as the real shielding cover; scan the real external leakage field of the real radiation source when the shielding cover is present, use the real external leakage field as the simulated external leakage field of the simulation model of the virtual shielding cover + dipole array, and reversely infer the final dipole moment of the virtual dipole.

[0015] Specifically, observations have shown a strong correlation between the leakage field of a real radiation source through the holes in the shielding cover and the radiation field inside the shielding cover. While a probe cannot penetrate deep into the shielding cover to test the radiation field of a real radiation source, the leakage field outside the shielding cover can be measured by scanning with the probe. Furthermore, by establishing a simulation model of a shielding cover + dipole, an optimization algorithm is used to adjust the position and preliminary dipole moment obtained in the first step, ensuring that the simulated leakage field of the dipole matches the non-leaking field of the real source outside the shielding cover. This ensures a good match between the dipole field and the real source field inside the shielding cover. In other words, after adding the shielding cover, the dipole's dipole moment is further adjusted to simulate the dipole's reflection of electromagnetic waves within the shielding cover, resulting in the final dipole moment. In this step, the position and number of the dipoles remain the same as in the first step. It should be noted that in the second step, when measuring the leakage field of the real source and the simulated shield + dipole model, only the shields of the two models must be similar. However, the shields can differ from the actual shield in shape and size. For example, only the top cover of the original shield can be retained, while the four walls (for a flat shield) can be removed, or holes can be opened in different locations of the original shield to facilitate leakage field measurement. As long as the original shield body is retained, it can be sufficient. This makes the method more versatile. That is, when adjusting the dipole moment, the original shield of similar shape and size can be replaced with a similar shield.

[0016] After obtaining the final dipole moment of the dipole, the position and dipole moment information of the dipole are brought into the full-wave electromagnetic simulation to calculate the coupling voltage / power between the dipole and the surrounding elements. This coupling voltage / power is the coupling voltage / power of the real radiation source to its surrounding elements.

[0017] Because shielding enclosures typically contain apertures, this invention measures the external leakage field of a real radiation source when the shielding enclosure is present, thereby adjusting the dipole moment. This ultimately improves the accuracy of using the dipole to predict the radiation field and coupling voltage of the real radiation source within the shielding enclosure. Due to the simple structure of the dipole and the analytical formula for the radiation field, using the dipole instead of the real radiation source greatly improves computational efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a diagram of the actual placement of the radiation source and the interfered object when the shielding cover is opened.

[0019] Figure 2 It is the coupling power value of the radiation source coupled to the interfered object when the shielding cover is closed.

[0020] Figure 3 It is a leakage field experiment configuration for testing real radiation sources when the shielding cover is closed.

[0021] Figure 4 It is a simulation model of the shielding cover, its radiation source and the disturbed object.

[0022] Figure 5 When there is a shielding cover, the total electric field distribution diagrams generated by the patch antenna (actual radiation source) (c), the dipole before (a) and after (b) dipole moment correction inside the shielding cover are shown. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the accompanying drawings and a measured example.

[0024] According to the electromagnetic equivalence principle, if two sources of different properties can generate the same electromagnetic field within the region being studied, then the two sources are said to be equivalent within that region. Based on this, a real radiation source can be equated with a virtual electromagnetic dipole. The radiation field of an electric dipole located at the origin of the coordinate system and along the z direction is:

[0025]

[0026] Similarly, the radiation field of a magnetic dipole located at the origin along the z direction is:

[0027]

[0028] In formulas (1) and (2), IΔl and I m Δl is the dipole moment of the electric and magnetic dipoles, E r 、E θ 、E φ They are respectively when the distance from the observation point to the origin in the spherical coordinate system is r, the zenith angle of the observation point is θ, and the azimuth angle is The electric field components in the r, θ, and φ directions generated by the dipole at r 、H θ 、H φ They are respectively when the distance from the observation point to the origin in the spherical coordinate system is r, the zenith angle of the observation point is θ, and the azimuth angle is The dipoles generated r, θ, The magnetic field component in the direction, k and η are the wave number and wave impedance of free space respectively, μ is the magnetic permeability of free space, is the imaginary unit, r, θ, are the distance from the observation point to the origin, the zenith angle, and the azimuth angle of the observation point in the spherical coordinate system.

[0029] Scan the electromagnetic field radiated by a real radiation source without a shield. According to the equivalence principle, these radiation fields are considered to be radiated by virtual dipoles. The number of dipoles is given, but their positions and dipole moments are unknown. Using equations (1) and (2), the following linear equations can be obtained:

[0030] AM=EH (3)

[0031] Where A represents the conversion matrix between the field and the source, and its value is calculated by formulas (1)-(2). M represents the dipole moment column vector of the dipole (which can be an electric dipole, a magnetic dipole, or a combination of the two). EH represents the electromagnetic field column vector obtained by scanning (which can be an electric field, a magnetic field, or a combination of the two). EH contains phase information (for example, the scanned field is measured by a network analyzer). When EH does not contain phase information (for example, the scanned field is measured by a spectrum analyzer), the linear equation group (3) becomes a nonlinear equation group (4):

[0032] |AM|=|EH| (4)

[0033] Among them, || represents the amplitude operation.

[0034] In the present invention, a virtual dipole is used to replace a real radiation source, and the position and dipole moment (radiation intensity of the dipole) information of the virtual dipole are calculated in two steps.

[0035] The first step is to scan the electromagnetic field of the real radiation source when the shield is opened, and use the optimization algorithm to infer the position and preliminary dipole moment of the virtual electromagnetic dipole corresponding to the real radiation source (changing A and M) so that the equations (3) or (4) are equal.

[0036] Figure 1 A shield cover is shown with copper foil on the bottom to prevent leakage. A chip with unknown structure is placed in the middle as the radiation source. A small monopole antenna is placed on the left as the interfered object. First, use the near-field probe to scan the area without the shield cover (such as Figure 1 The radiation field of the radiation source is measured when the shield is open (shown in the figure). The radiation source is excited by a 20dBm signal source and the scanning surface is 2mm away from the radiation source. In this embodiment, the radiation field E is measured. z 、H x 、H y Amplitude, the radiation source is excited by a 20dBm signal source.

[0037] Then, the differential evolution algorithm (DE) is used to solve the equation group (4) to obtain the position and preliminary dipole moment of the dipole. In this embodiment, several electric dipoles in the z direction, magnetic dipoles in the x direction, and magnetic dipoles in the y direction are selected as equivalent sources of the unknown chip.

[0038] The obtained dipole, shield, and victim are subjected to full-wave electromagnetic simulation to calculate the coupling power of the dipole to the victim. This embodiment calculates the coupling power at two frequencies of 9 GHz and 14.9 GHz, and the values ​​are as follows: Figure 2 Indicated by the middle dot. Figure 2The reference value in the figure refers to the coupling power received by the victim measured by connecting the victim with a spectrum analyzer when the shielding cover is present and the radiation source is stimulated by a 20dBm signal source. Figure 2 It can be seen that the coupling power error of the dipole prediction is large before the dipole moment correction.

[0039] In the second step, the external leakage field of the real radiation source is scanned after the shield is closed, and the final dipole moment of the virtual dipole is inferred through the optimization algorithm.

[0040] Figure 3 The figure shows the leakage field of a real radiation source through two holes after adding the shield cover (the shield cover has two holes). The leakage field is 1mm away from the shield cover. The probe and radiation source are connected to the spectrum analyzer and signal source respectively. The calibration factor of the probe is used and the cable loss is taken into account. Finally, the spectrum analyzer reading is converted into the leakage field E. z Component amplitude.

[0041] Perform full-wave simulation on the dipole and shield obtained in the first step to calculate the leakage field E of the dipole. z The component amplitude is calculated and the dipole moment of the dipole in the full-wave simulation is adjusted by the optimization algorithm so that the leakage field E z The component amplitude is the same as the above real source leakage field E z The component amplitudes match and the final dipole moment is obtained. The final dipole moment, the shielding cover and the disturbed body are subjected to full-wave electromagnetic simulation to calculate the coupling power of the dipole to the disturbed body. This embodiment calculates the coupling power of the two frequency points of 9GHz and 14.9GHz, and its value is as follows Figure 2 As shown by "x". Figure 2 It can be seen that after the dipole moment correction, the coupling power predicted by the dipole is closer to the reference value, and the error is reduced from 15 dB to 5 dB, which verifies the effectiveness of the method proposed in this invention.

[0042] Next, a simulation example is used to illustrate that the method for correcting the dipole moment of the present invention can improve the degree of consistency between the field of the dipole and the real source inside the shielding cover. Figure 4 In the simulation model established for this embodiment, a rectangular shielding cover with a thickness of 1 mm was placed on the PCB, with a gap of 0.2 mm between the four walls of the shielding cover and the PCB surface. The radiation source inside the shielding cover was a patch antenna. Figure 5 (a) and (b) are the total electric field distribution diagrams generated by the dipole in the shielding case before and after the dipole moment correction, respectively. Figure 5(c) shows the total electric field distribution generated by the patch antenna within the shield. As can be seen from the figure, after the dipole moment is corrected, the bright spots in the electric field generated by the dipole and the patch antenna are more consistent. This illustrates why the proposed method can improve the accuracy of coupling power calculation within the shield.

[0043] The above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples, and many variations are possible. All variations that can be directly derived or imagined by a person skilled in the art from the disclosure of the present invention should be considered to be within the scope of protection of the present invention.

Claims

1. A radiation source modeling method for electronic devices in a shielding case, characterized in that: include: The radiation source of the electronic device in the shielding case is equivalent to a virtual electromagnetic dipole array, and an equivalent model is constructed based on the dipole radiation field; The position and initial dipole moment of the dipole are calculated using the electromagnetic field of the real radiation source without a shielding cover. The method comprises fixing the position and number of the dipoles, using the leakage field of the real radiation source when the shielding cover is in place, adjusting the initial dipole moment of the dipole model in the shielding cover, and obtaining the final dipole moment of the dipole, including: establishing a simulation model of a virtual shielding cover + a dipole array according to the position and initial dipole moment of the dipoles, wherein the virtual shielding cover has the same shape and size as the real shielding cover; scanning the real external leakage field of the real radiation source when the shielding cover is in place, using the real external leakage field as the simulated external leakage field of the simulation model of the virtual shielding cover + the dipole array, and inversely deducing the final dipole moment of the virtual dipole; The dipole positions, final dipole moments, and shielding can are brought into the full-wave electromagnetic simulation model to calculate the coupling voltage or power between the dipole array and the components inside and outside the shielding can. The coupling voltage / power is the coupling voltage or power of the real radiation source to the surrounding components when the shielding can is present.

2. The radiation source modeling method of an electronic device in a shielding case according to claim 1, characterized in that: The method of calculating the position and initial dipole moment of the dipole by utilizing the radiation electromagnetic field of the real radiation source when there is no shielding cover includes: The real radiation electromagnetic field of the real radiation source when there is no shielding cover or the shielding cover is opened is scanned, and the real radiation electromagnetic field is used as the equivalent radiation electromagnetic field in the equivalent model to reversely deduce the position and initial dipole moment of the virtual electromagnetic dipole corresponding to the real radiation source.

3. The radiation source modeling method of an electronic device in a shielding case according to claim 1 or 2, characterized in that: The position, initial dipole moment and final dipole moment of the dipole are calculated using the differential evolution method.

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