An apparatus and method for non-intrusive harness radio frequency coupling current suppression

Abstract

The present disclosure relates to an apparatus and method for non-intrusive harness RF coupling current suppression. The apparatus of the present disclosure includes a matching resistor connected across the harness for reducing the spike in the coupling current on the harness shield due to reflections. The apparatus also includes a TVS device connected in parallel with the matching resistor for suppressing transient voltages, thereby ensuring that the matching resistor affects the lightning open circuit voltage within the lightning frequency band.

Description

Technical Field

[0001] This disclosure relates to the field of aviation electromagnetic environment, and specifically to an apparatus and method for suppressing radio frequency coupling current in non-invasive wire harnesses. Background Technology

[0002] High-intensity electromagnetic radiation (HIRF) is a source of interference for aircraft, coupling into onboard equipment via wiring harnesses in the radio frequency band. The current coupling band of HIRF is between 10kHz and 400MHz. The wavelengths corresponding to this band are close to the electrical dimensions of the aircraft, as well as the electrical dimensions of the cabin and openings, making resonance prone to cause excessive coupling current. Currently, for wideband coupling current exceeding limits, metal shielding sleeves are typically installed on the wiring harness for full-band protection; or for narrowband exceeding limits in specific frequency bands, filter circuits are installed on the corresponding equipment sockets to eliminate coupling current spikes. However, installing metal shielding sleeves on the wiring harness significantly increases weight; installing filter circuits on the equipment sockets usually affects the signals of other pins, requiring redesign and debugging of the circuit board, resulting in high R&D costs.

[0003] Therefore, there is an urgent need for a method and apparatus to further improve the existing wideband coupling current over-limit suppression scheme. Summary of the Invention

[0004] This summary is provided to introduce, in a simplified form, some concepts that will be further described in the following detailed description section. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0005] To address the problems in the prior art, this disclosure provides an apparatus and method for suppressing radio frequency coupling current in non-intrusive wire harnesses. The apparatus includes a matching resistor connected across the wire harness to reduce spikes in the coupling current caused by reflections from the wire harness shielding. The apparatus also includes a TVS device connected in parallel with the matching resistor to suppress transient voltages, thereby ensuring that the matching resistor affects the open-circuit voltage of lightning in the lightning frequency band.

[0006] Specifically, in a first aspect of the invention, a device for non-invasive wire harness radio frequency coupling current suppression is disclosed, the device being connected between a wire harness shielding layer and an aircraft fuselage structure, the device comprising: Matching resistors, connected across the wire harness, are used to reduce the spikes in the coupling current caused by reflections in the wire harness shielding layer; and A transient voltage suppression (TVS) device is connected in parallel with the matching resistor to suppress transient voltages.

[0007] In one alternative embodiment, the device further includes a printed circuit board (PCB) arranged on a square interface for mounting the matching resistor and the TVS device.

[0008] In one alternative embodiment, the device further includes: A connector adapter end, which connects to a wire harness connector; and Tail accessory adapter, which connects to the tail accessory of the wiring harness. The PCB is mounted between the connector adapter end and the tail accessory adapter end, and the wire harness connector is used to connect the wire harness to the aircraft airframe structure.

[0009] In an alternative embodiment, the device further includes a split block for securing the PCB and is connected and secured to the connector adapter end and the tail accessory adapter end via a binding cord through a through-hole.

[0010] In one alternative implementation, the half block is non-metallic, while the surfaces of the connector adapter end and the tail accessory adapter end are metallic and electrically connected to the PCB.

[0011] In one alternative implementation, the matching resistor is selected to have an associated characteristic impedance, which is obtained by establishing a geometric model of the harness shielding layer and the aircraft airframe structure and by experimental measurement or equivalent calculation based on the geometric model.

[0012] In one alternative implementation, the test measurement includes using a time-domain reflectometer to measure the characteristic impedance of the equivalent transmission line in the time domain via a balun transformation from a balanced to an unbalanced line, wherein all cable shielding layers of the internal cables of the harness are shorted to use the harness shielding layer as a whole with the aircraft airframe structure as the equivalent transmission line.

[0013] In one alternative implementation, the equivalent calculation includes calculating the characteristic impedance using a transmission line calculation model with a similar structure, wherein: This similar structure includes wire harnesses laid on a near-plane surface and wire harnesses laid in a groove, and The transmission line calculation model includes a stripline calculation model corresponding to the wiring harness being laid on a near-plane and a slot line calculation model corresponding to the wiring harness being laid in a slot.

[0014] In a second aspect of this disclosure, a method for suppressing radio frequency coupling current in a wire harness is disclosed, the method comprising: Establish a geometric model of the wire harness shielding layer and the aircraft airframe structure; Based on this geometric model, the characteristic impedance of the equivalent transmission line can be obtained through experimental measurement or equivalent calculation. Based on this characteristic impedance, a matching resistor with an associated resistance value is selected; and The matching resistor is connected in parallel with the TVS device, and both are connected between the wiring harness shield and the aircraft airframe structure.

[0015] In one alternative implementation, establishing the geometric model further includes shorting all cable shields of the internal cables of the harness to use the harness shields as a whole with the aircraft airframe structure as the equivalent transmission line.

[0016] In one alternative implementation, the test measurement includes using a time-domain reflectometer to measure the characteristic impedance of the equivalent transmission line in the time domain via a balun transformation from a balanced to an unbalanced line.

[0017] In one alternative implementation, the equivalent calculation includes calculating the characteristic impedance using a transmission line calculation model with a similar structure, wherein: This similar structure includes wire harnesses laid on a near-plane surface and wire harnesses laid in a groove, and The transmission line calculation model includes a stripline calculation model corresponding to the wiring harness being laid on a near-plane and a slot line calculation model corresponding to the wiring harness being laid in a slot.

[0018] In one alternative implementation, the matching resistor is connected across the harness and is used to reduce the spikes in the coupling current caused by reflection in the harness shielding layer, and the TVS device is used to suppress transient voltages.

[0019] In an alternative embodiment, the connection between the harness shielding layer and the aircraft body structure further includes: connecting the matching resistor and the TVS device between the harness connector and the harness tail accessory and mounting them on the harness.

[0020] Other aspects, features, and embodiments of the invention will become apparent to those skilled in the art after reading the following description of specific exemplary embodiments of the invention in conjunction with the accompanying drawings. Although features of the invention may be discussed below with reference to certain embodiments and drawings, all embodiments of the invention may include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed having certain advantageous features, one or more of such features may also be used according to the various embodiments of the invention discussed herein. Similarly, although exemplary embodiments may be discussed below as embodiments of devices, apparatuses, or methods, it should be understood that such exemplary embodiments may be implemented in various devices, apparatuses, and methods. Attached Figure Description

[0021] To gain a more detailed understanding of the features described above in this disclosure, reference can be made to a more specific description of the above-briefly summarized aspects, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only certain typical aspects of this disclosure and should not be considered as limiting its scope, as other equivalent aspects are permissible in this description.

[0022] Figure 1 This is a schematic diagram of an apparatus for non-invasive wire harness radio frequency coupling current suppression according to an embodiment of the present disclosure.

[0023] Figure 2 This is a schematic diagram of the equivalent transmission line for suppressing HIRF interference current coupling according to an embodiment of the present disclosure.

[0024] Figure 3 This is a schematic diagram of the PCB mounting position according to an embodiment of the present disclosure.

[0025] Figure 4 This is a schematic diagram of a connector adapter end according to an embodiment of the present disclosure.

[0026] Figure 5 This is a schematic diagram of a tail accessory adapter according to an embodiment of the present disclosure.

[0027] Figure 6 This is a schematic diagram of a half block according to an embodiment of the present disclosure.

[0028] Figure 7 This is an assembly diagram of an apparatus for non-invasive wire harness radio frequency coupling current suppression according to an embodiment of the present disclosure.

[0029] Figure 8 This is a schematic diagram of experimental measurement of the characteristic impedance of an equivalent transmission line according to an embodiment of the present disclosure.

[0030] Figure 9 This is a schematic diagram of a microstrip line computation model according to an embodiment of the present disclosure.

[0031] Figure 10 This is a schematic diagram of a slot line calculation model according to an embodiment of the present disclosure.

[0032] Figure 11 This is a schematic diagram comparing impedance matching grounding and direct grounding according to an embodiment of the present disclosure.

[0033] Figure 12 This is a flowchart of a method for suppressing radio frequency coupling current in a wire harness according to an embodiment of the present disclosure. Detailed Implementation

[0034] The various embodiments will now be described in more detail with reference to the accompanying drawings, which form part of this invention and illustrate specific exemplary embodiments. However, the embodiments may be implemented in many different forms and should not be construed as limiting the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of these embodiments to those skilled in the art. The embodiments may be implemented as methods, apparatus, or devices. Therefore, these embodiments may be implemented in hardware, entirely in software, or in a combination of software and hardware aspects. Therefore, the following detailed description is not intended to be limiting.

[0035] The steps in each flowchart can be performed by hardware (e.g., processor, engine, memory, circuitry), software (e.g., operating system, application, driver, machine / processor executable instructions), or a combination thereof. As will be understood by those skilled in the art, the methods involved in each embodiment may include more or fewer steps than shown.

[0036] Aircraft wiring harnesses are typically laid along structural panels and, to prevent wear, are usually kept at a certain distance from the panels. The cable shielding and the wiring harness shielding are short-circuited at both ends of the harness before being grounded via connector tail clamps or directly connected to a grounding stake. The technical solution disclosed in this invention eliminates the need for external metal shielding sleeves and short-circuits all cable shielding layers within the wiring harness, thus treating the entire wiring harness shielding layer and the aircraft fuselage structure as an equivalent transmission line. Matching resistors are connected at both ends of the wiring harness for impedance matching, reducing the spikes in coupling current caused by reflections in the wiring harness shielding layer, thereby reducing current coupling exceeding limits. Simultaneously, to ensure that the matching resistors do not affect the open-circuit voltage of lightning in the lightning frequency band, TVS devices (such as TVS diodes) are connected in parallel with the matching resistors, ultimately improving HIRF current coupling protection capabilities without compromising lightning protection.

[0037] The various aspects of the present invention will now be described in detail.

[0038] Figure 1 This is a schematic diagram of an apparatus 100 for non-invasive wire harness radio frequency coupling current suppression according to an embodiment of the present disclosure.

[0039] like Figure 1 As shown, the device 100 for non-intrusive wire harness RF coupling current suppression may include a matching resistor 102 and a TVS device 104. Figure 1 As further illustrated, this is achieved by connecting to the wire harness connector (i.e. Figure 1 (connectors in the middle) and harness tail accessories (i.e. Figure 1 Between the tail attachments (in the aircraft) and the wiring harness shielding layer, device 100 can be connected between the aircraft fuselage structure and the wiring harness shielding layer. The following will combine... Figure 2The device 100 is described in more detail. The shape of the device 100 can be manufactured according to the size of the TVS device and the matching resistor. By mounting it between the harness tail accessory and the harness connector, the stress relief of the tail accessory and the cable shield lead termination function can be maintained. Both the housing surface of the harness connector and the housing surface of the harness tail accessory should be highly conductive.

[0040] Figure 2 This is a schematic diagram of an equivalent transmission line for suppressing HIRF interference current coupling according to an embodiment of the present disclosure. In this embodiment, the matching resistor 102 can be connected across the wire harness and is used to reduce the spikes in the coupling current caused by reflection in the wire harness shielding layer, and the TVS device 104 is connected in parallel with the matching resistor and is used to suppress transient voltages. Using the TVS device 104 (such as a TVS diode) ensures that the matching impedance grounding method does not affect the implementation of lightning indirect effect protection and electrostatic discharge protection.

[0041] like Figure 2 As shown, by short-circuiting all the cable shielding layers inside the wiring harness, the wiring harness shielding layer can be considered as a whole, together with the aircraft fuselage structure, as an equivalent transmission line. This allows for the establishment of a geometric model of the wiring harness shielding layer and the aircraft fuselage structure, thereby eliminating the need for the external metal shielding sleeve and significantly reducing weight. Furthermore... Figure 2 As shown, matching resistors (or impedance matching circuits) can be connected to both ends of the transmission line to reduce the spikes in the coupling current caused by reflection in the wire harness shielding layer, thereby reducing the current coupling exceedance.

[0042] like Figure 2 As further shown, a TVS device (such as a TVS diode, or TVS tube) can be added and connected in parallel with the matching resistor. Both can be connected as device 100 between the harness connector and the harness tail accessory (such as...). Figure 1 As shown in the diagram, this allows the matching resistor to be connected between the wire harness shielding layer and the aircraft fuselage structure. This ensures that the matching resistor does not affect the lightning open-circuit voltage within the lightning frequency band, ultimately improving HIRF current coupling protection capabilities without compromising lightning protection. Figure 2 The method shown can be considered as an impedance-matched grounding approach, replacing the commonly used direct short-circuit grounding. Furthermore, the matching resistor connects to the harness shielding layer, without altering the signal or corresponding pins, and without requiring modifications to the device's circuit design. This method can reduce induced current spikes across the entire frequency band below 400MHz, rather than just improving a specific frequency (or wavelength).

[0043] In an alternative embodiment, the device 100 may further include a printed circuit board (PCB) which may be arranged on a square interface and used to mount the matching resistor 102 and the TVS device 104.

[0044] Figure 3 This is a schematic diagram of the PCB mounting position according to an embodiment of the present disclosure. The PCB can be arranged on the central square interface, with the left side of the interface ( Figure 5 ) and right side ( Figure 4 The components of ) will be described below.

[0045] In an alternative embodiment, the device 100 may further include: a connector adapter end that can be connected to a wire harness connector; and a tail accessory adapter end that can be connected to a wire harness tail accessory. The PCB may be mounted between the connector adapter end and the tail accessory adapter end, and the wire harness connector is used to connect the wire harness to the aircraft fuselage structure.

[0046] Figure 4 This is a schematic diagram of a connector adapter end according to an embodiment of the present disclosure. Connectors are typically externally threaded, so an internal thread is used as the connector adapter end.

[0047] Figure 5 This is a schematic diagram of a tail accessory adapter end according to an embodiment of the present disclosure. Tail accessories are typically internally threaded, therefore an external thread is used as the tail accessory adapter end.

[0048] In an alternative embodiment, the device may further include a half block that can be used to secure the PCB and can be connected and secured to the connector adapter end and the tail accessory adapter end through a through hole via a binding rope.

[0049] Figure 6 This is a schematic diagram of a splitter block according to an embodiment of the present disclosure. In an alternative embodiment, the splitter block may be non-metallic, and the surfaces of the connector adapter end and the tail accessory adapter end may both be metal and electrically connected to the PCB.

[0050] Figure 7 This is an assembly diagram of a device for non-invasive wire harness RF coupling current suppression according to an embodiment of the present disclosure. A half-block (PCB size and half-block adapter) for fixing a PCB (on which a matching resistor and TVD device are mounted) can be assembled with a connector adapter end and a tail accessory adapter end to form a configuration as shown below. Figure 7 The component assembly diagram is shown. In an optional embodiment, for example, the matching resistor can be a commercially available RF resistor that meets the operating frequency band of 400MHz and above and whose resistance value can fluctuate by 30%, and the TVS device selection must meet the lightning indirect effect level requirements of the aircraft cabin where device 100 is located.

[0051] As will be understood by those skilled in the art, this assembly method is merely exemplary and not limiting, and the above-described methods of mounting matching resistors and TVS devices on the PCB, fixing the PCB, and the styles of connector adapters and tail accessory adapters are merely exemplary and not limiting. In other embodiments of this disclosure, any other suitable methods may be used to design the various components and assembly methods of the device 100.

[0052] In one alternative implementation, the matching resistor 102 may be selected to have an associated characteristic impedance (having a resistance value that is the same as or close to the characteristic impedance, as those skilled in the art will understand, close can be defined as the difference between the resistance value and the characteristic impedance being within a threshold, which can be any suitable threshold and is not limited to any particular threshold), which can be obtained by establishing a geometric model of the harness shielding layer and the aircraft body structure and by experimental measurement or equivalent calculation based on the geometric model.

[0053] Figure 8 This is a schematic diagram of experimentally measuring the equivalent transmission line characteristic impedance according to one embodiment of the present disclosure. In an alternative implementation, such as Figure 8 As shown, experimental measurements may include using a time-domain reflectometer (such as a vector network analyzer or oscilloscope with time-domain reflectometry) to measure the characteristic impedance of the equivalent transmission line in the time domain via a balun transformation from balanced to unbalanced lines. All cable shielding layers of the internal cables of the harness are shorted to integrate the harness shielding layer as a whole with the aircraft airframe structure as the equivalent transmission line. Figure 8 As shown, after the balun is converted to a balanced cable port, one end connects to the exposed metal of the structure, and the other end connects to the cable shielding layer where the cable harness ends are shorted together. As those skilled in the art will understand, the above-described test and measurement methods are merely exemplary and not limiting.

[0054] In one optional implementation, the equivalent calculation may include calculating the characteristic impedance using a transmission line calculation model with a similar structure. This similar structure may include at least a wire harness laid on a near-plane and a wire harness laid in a slot. Furthermore, the transmission line calculation model may include at least a stripline calculation model corresponding to the wire harness laid on a near-plane and a slotline calculation model corresponding to the wire harness laid in a slot. Specifically: Figure 9 This is a schematic diagram of a microstrip line computation model according to an embodiment of the present disclosure.

[0055] Because the wiring harness is suspended above the aircraft structure, it has a relative permittivity ε. r =1, and the strip width W = thickness, t = D, where D is the wire harness diameter, and h refers to the dielectric substrate thickness. The characteristic impedance Z0 can be calculated using the following formula: (Formula 1) Figure 10 This is a schematic diagram of a slot line calculation model according to an embodiment of the present disclosure.

[0056] Similarly, D is the wire harness diameter, b refers to the slot width, H refers to the distance from the slot wall to the center of the wire harness, and the characteristic impedance Z0 can be calculated using the following formula:

[0057] In other embodiments of the present invention, Maxwell's equations or specialized software can also be used to derive the characteristic impedance. As those skilled in the art will understand, the methods described above for deriving the characteristic impedance using Equations 1 and 2 are merely exemplary and not limiting; any other suitable method can be used to calculate the characteristic impedance of the matching resistor.

[0058] Figure 11 This is a schematic diagram comparing impedance matching grounding and direct grounding according to an embodiment of the present disclosure.

[0059] Taking a cable harness laid on a near-plane surface as an example, assuming the harness diameter is 5mm, the distance from the ground is 10cm, and the harness length is 15m. According to the stripline model, the characteristic impedance Z0 formed by the cable harness and the structural ground is approximately 318Ω. The incident wave is a horizontally polarized plane wave of 1V / m, and the direction of illumination is perpendicular to the plane formed by the projection of the cable harness and the ground. Using a commonly used resistance value of 330Ω, the simulation results are as follows... Figure 11 As shown, it can be seen that compared with the traditional wire harness shielding layer being directly grounded at both ends, the device 100 using impedance matching grounding effectively suppresses current spikes, suppressing coupling current spikes by more than 10 times, that is, more than 20dB, which has a good effect.

[0060] Figure 12 This is a flowchart of a method 1200 for suppressing radio frequency coupling current in a wire harness according to an embodiment of the present disclosure.

[0061] like Figure 12 As shown, method 1200 begins at step 1202, establishing a geometric model of the wire harness shielding layer and the aircraft airframe structure. In an alternative embodiment, establishing the geometric model may further include: shorting all cable shielding layers of the internal cables of the wire harness to use the entire wire harness shielding layer and the aircraft airframe structure as the equivalent transmission line.

[0062] Next, method 1200 continues to step 1204, obtaining the characteristic impedance of the equivalent transmission line by experimental measurement or equivalent calculation based on the geometric model. In one optional embodiment, the experimental measurement may include using a time-domain reflectometer to measure the characteristic impedance of the equivalent transmission line in the time domain by a balun transformation from a balanced line to an unbalanced line. In another optional embodiment, the equivalent calculation may include using a transmission line calculation model with a similar structure to calculate the characteristic impedance, wherein the similar structure may include a wire bundle laid in a near-plane and a wire bundle laid in a slot, and the transmission line calculation model may include a stripline calculation model corresponding to the wire bundle laid in a near-plane and a slotline calculation model corresponding to the wire bundle laid in a slot.

[0063] Then, method 1200 continues to step 1206, selecting a matching resistor with an associated resistance value based on the characteristic impedance. In an alternative implementation, the matching resistor may be connected across the harness and used to reduce spikes in the coupling current caused by reflections in the harness shielding layer, and the TVS device may be used to suppress transient voltages.

[0064] Finally, method 1200 continues to step 1208, whereby the matching resistor and the TVS device are connected in parallel and both are connected between the harness shielding layer and the aircraft fuselage structure. In an alternative embodiment, the connection between the harness shielding layer and the aircraft fuselage structure further includes: connecting the matching resistor and the TVS device between the harness connector and the harness tail accessory and mounting them on the harness.

[0065] After step 1208, method 1200 ends.

[0066] In summary, this disclosure proposes a non-invasive wire harness radio frequency coupling current suppression device and method, which can suppress the induced current coupled to the wire harness by the high-intensity electromagnetic radiation field according to the electromagnetic environment of the aircraft. The device only acts on the wire harness shielding layer and will not affect the internal pins of the connector or the circuit board wiring of the airborne equipment.

[0067] The embodiments of the present invention have been described above with reference to block diagrams and / or operational descriptions of methods and apparatus according to embodiments of the present invention. The functions / actions indicated in the blocks may appear in a different order than shown in any flowchart. For example, depending on the functions / actions involved, two blocks shown consecutively may actually be executed substantially simultaneously, or these blocks may sometimes be executed in reverse order.

[0068] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A device for suppressing radio frequency coupling current in a non-invasive wire harness, the device being connected between a wire harness shielding layer and an aircraft fuselage structure, the device comprising: A matching resistor is connected to both ends of the wire harness and is used to reduce the spikes in the coupling current caused by reflection in the wire harness shielding layer. as well as A transient voltage suppression TVS device is provided, wherein the TVS device is connected in parallel with the matching resistor and is used to suppress transient voltage.

2. The apparatus as claimed in claim 1, characterized in that, The device also includes a printed circuit board (PCB) arranged on a square interface for mounting the matching resistor and the TVS device.

3. The apparatus as described in claim 2, characterized in that, The device further includes: A connector adapter end, which is connected to a wire harness connector; and Tail accessory adapter, which is connected to the tail accessory of the wire harness. The PCB is mounted between the connector adapter end and the tail accessory adapter end, and the wire harness connector is used to connect the wire harness to the aircraft airframe structure.

4. The apparatus as described in claim 3, characterized in that, The device also includes a split block for securing the PCB and is connected and secured to the connector adapter end and the tail accessory adapter end via a binding rope through a through hole.

5. The apparatus as described in claim 4, characterized in that, The half block is non-metallic, while the surfaces of the connector adapter end and the tail accessory adapter end are both metallic and electrically connected to the PCB.

6. The apparatus as claimed in claim 1, characterized in that, The matching resistor is selected to have an associated characteristic impedance, which is obtained by establishing a geometric model of the harness shielding layer and the aircraft airframe structure and by experimental measurement or equivalent calculation based on the geometric model.

7. The apparatus of claim 6, wherein the test measurement comprises using a time-domain reflectometer to measure the characteristic impedance of the equivalent transmission line in the time domain by a balun transformation from a balanced line to an unbalanced line, wherein all cable shields of the internal cables of the harness are shorted to integrate the harness shields as a whole with the aircraft airframe structure as the equivalent transmission line.

8. The apparatus as claimed in claim 6, characterized in that, The equivalent calculation includes using a transmission line calculation model with a similar structure to calculate the characteristic impedance, wherein: The similar structures include the wire harness being laid on a near-plane and the wire harness being laid in a groove, and The transmission line calculation model includes a stripline calculation model corresponding to the wiring harness being laid on a near-plane and a slot line calculation model corresponding to the wiring harness being laid in a slot.

9. A method for suppressing radio frequency coupling current in a wire harness, the method comprising: Establish a geometric model of the wire harness shielding layer and the aircraft airframe structure; Based on the geometric model, the characteristic impedance of the equivalent transmission line is obtained through experimental measurement or equivalent calculation. Select a matching resistor with an associated resistance value based on the characteristic impedance; as well as The matching resistor is connected in parallel with the TVS device, and both are connected between the wire harness shielding layer and the aircraft airframe structure.

10. The method as described in claim 9, characterized in that, Establishing the geometric model also includes: shorting all the cable shielding layers of the internal cables of the harness to use the harness shielding layer as a whole with the aircraft body structure as the equivalent transmission line.

11. The method as described in claim 9, characterized in that, The experimental measurements include using a time-domain reflectometer to measure the characteristic impedance of the equivalent transmission line in the time domain via a balun transformation from a balanced to an unbalanced line.

12. The method as described in claim 9, characterized in that, The equivalent calculation includes using a transmission line calculation model with a similar structure to calculate the characteristic impedance, wherein: The similar structures include the wire harness being laid on a near-plane and the wire harness being laid in a groove, and The transmission line calculation model includes a stripline calculation model corresponding to the wiring harness being laid on a near-plane and a slot line calculation model corresponding to the wiring harness being laid in a slot.

13. The method as described in claim 9, characterized in that, The matching resistor is connected to both ends of the harness and is used to reduce the spikes in the coupling current caused by reflection in the harness shielding layer, and the TVS device is used to suppress transient voltage.

14. The method as described in claim 9, characterized in that, The connection between the wire harness shielding layer and the aircraft body structure further includes: connecting the matching resistor and the TVS device between the wire harness connector and the wire harness tail accessory and mounting them on the wire harness.

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