Methods and apparatus for detecting electromagnetic compatibility radiated emissions of whole vehicles

Abstract

This invention provides a method and apparatus for detecting electromagnetic compatibility radiated emissions from a vehicle, relating to the field of automotive electronics technology. The invention constructs a dynamic ground loop impedance excitation platform in an anechoic chamber, controls the on / off state of metal ground units through a digital ground plane array, generates various test conditions, and simultaneously acquires the vehicle's time-domain radiated field signal and ground loop common-mode current signal. Time-frequency analysis is performed on the signals to identify out-of-standard frequencies, calculates the rate of change of radiated field strength and ground loop impedance relative to the baseline conditions, and quantifies it as a fault sensitivity factor. Based on this, a high-dimensional fault feature fingerprint matrix is ​​constructed. This vector is matched with a pre-set fault mode database to diagnose the main fault source types. By analyzing the spatial dimensions sensitive to ground loop disturbances in the feature fingerprint, and combining this with the vehicle's electrical topology model, the installation location of the fault source is calculated. Finally, a structured report containing diagnostic results, location information, and rectification suggestions is automatically generated.

Description

Technical Field

[0001] This invention relates to the field of automotive electronics technology, specifically to a method and apparatus for detecting electromagnetic compatibility radiated emissions from a vehicle. Background Technology

[0002] EMC (Electromagnetic Compatibility) radiated emission testing is a crucial step in the development and certification of automotive electronic and electrical systems. Its purpose is to ensure that the vehicle does not generate excessive electromagnetic radiation in complex electromagnetic environments, thus avoiding interference with other electronic devices or violations of mandatory regulations and standards. The number of onboard electronic components has surged, with wide operating frequency ranges and varying power levels, leading to increasingly complex radiated noise sources and diverse coupling paths. Traditional radiated emission testing is typically conducted in an anechoic chamber, using antenna scanning to acquire radiated field strength data within the specified frequency band and comparing it to limit lines to determine compliance. However, when test results exceed limits, existing methods struggle to quickly and accurately pinpoint the specific internal noise source and its weak points. Engineers often rely on experience for time-consuming troubleshooting and debugging, severely impacting the vehicle development cycle and the efficiency of problem rectification.

[0003] Currently, the diagnosis of excessive radiated emissions mainly relies on two approaches. One approach involves offline component-level testing based on whole-vehicle testing, where suspected components are measured separately in a test environment. This method disconnects the actual grounding, wiring, and coupling conditions between the component and the vehicle, often resulting in distorted diagnostic results. The other approach attempts to infer the noise source by alternating the switching on and off of power supplies to different components during whole-vehicle testing and observing changes in the radiation spectrum. While this method considers the whole-vehicle environment, it is essentially a passive, trial-and-error troubleshooting method. The switching operations it relies on only change the power supply state of the noise source and do not systematically alter the transmission path of electromagnetic noise, especially ignoring the ground loop impedance, a key factor affecting common-mode radiation. Therefore, its ability to identify complex coupled noise is limited, and it cannot reveal the mechanism by which noise leaks through grounding paths.

[0004] The fundamental deficiency of existing technologies lies in their failure to actively and controllably excite and measure the key transmission channel of electromagnetic emission from the vehicle, namely the ground loop system. Existing methods either deviate from the actual grounding environment of the vehicle or can only observe the radiation results under a fixed grounding state, failing to obtain the response law of radiation characteristics to changes in the ground loop structure. Due to the lack of active manipulation and analysis of the key variable of the spatial distribution of ground loop impedance, existing technologies cannot construct a characteristic fingerprint that can uniquely characterize a specific noise source and its leakage path. This fundamentally restricts their ability to perform accurate fault diagnosis and physical location. Consequently, when faced with radiation exceeding the standard, existing technologies often can only conclude whether the standard is exceeded, but cannot answer the two most critical questions in engineering rectification: what is the cause and where is the leakage?

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for detecting electromagnetic compatibility radiated emissions from a vehicle, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for detecting electromagnetic compatibility radiated emissions from a vehicle, comprising the following steps:

[0009] Step 1: Fix the vehicle under test on the insulating support fixture in the electromagnetic compatibility anechoic chamber, and set up a digital ground plane array at the reference ground plane under the vehicle chassis. The array is composed of metal ground units.

[0010] Step 2: Based on the test control host, control the on / off state of the metal ground unit to construct a fully grounded reference condition between the vehicle chassis and the reference ground, as well as a variety of test conditions with different ground loop impedance distributions, and each condition corresponds to a set of ground unit on / off combinations.

[0011] Step 3: After the test conditions stabilize, the time-domain radiation field signal of the whole vehicle and the common-mode current signal of the ground loop flowing into the array are captured and analyzed simultaneously. The frequency points where the radiated emission exceeds the standard are identified. The rate of change of the radiation field strength and the ground loop impedance relative to the reference condition are calculated at each frequency point. Based on the numerical relationship between the two, the fault sensitivity factor at each frequency point under the test condition is quantified. All the fault sensitivity factors are arranged in an orderly manner to construct a fault feature fingerprint matrix.

[0012] Step 4: Match the fault feature fingerprint matrix with various typical noise source fault mode templates, select the fault mode template with the highest matching degree, and the corresponding noise source type is diagnosed as the main fault source causing the vehicle's radiation emissions to exceed the standard. Generate a structured diagnostic report based on the diagnostic results.

[0013] Furthermore, the vehicle under test is fixed on an insulating support fixture in an electromagnetic compatibility anechoic chamber. Specifically, a special support fixture made of insulating material is used to lift the vehicle tires off the metal reference ground plane of the anechoic chamber and maintain a defined physical isolation space between the vehicle chassis and the metal reference ground plane of the anechoic chamber without any direct electrical contact, thereby simulating the insulation state of the vehicle in actual driving.

[0014] A digital ground plane array is set up at the reference ground plane under the vehicle chassis. Specifically, in a preset area of ​​the reference ground plane in the anechoic chamber, a digital ground plane array consisting of several independent metal patches is installed. Each metal patch serves as a metal ground unit. Each metal ground unit is controlled by a high-speed radio frequency switch controlled by the test control host to control the electrical connection between the metal ground unit and the system reference ground network. The high-speed radio frequency switch is controlled by the test control host to switch the corresponding metal ground unit between an electrically connected state and a high-impedance disconnected state.

[0015] Furthermore, a fully grounded reference condition is constructed between the vehicle chassis and the reference ground, as well as various test conditions with different ground loop impedance distributions, specifically referring to:

[0016] All metal ground units in the digital ground plane array are turned on to construct a fully grounded reference condition between the vehicle chassis and the reference ground. The test control host sequentially controls one or more high-speed radio frequency switches of the digital ground plane array to turn off according to preset modes, so that it presents a series of different ground unit on / off combinations. The preset modes include turning off individual metal ground units according to the vehicle chassis area division sequence, turning off multiple non-adjacent metal ground units in combination, and performing ground unit on / off combinations covering specific impedance distribution scenarios, thereby constructing a series of test conditions.

[0017] After each test condition stabilizes, the time-domain radiation field signal of the entire vehicle and the common-mode current signal flowing into the array are captured synchronously. Specifically, this includes: synchronously acquiring the time-domain radiation field voltage signal of the entire vehicle through at least four broadband electric field probes arranged around the entire vehicle; and simultaneously acquiring the common-mode current signal flowing into the digital ground plane array through a high-frequency current probe coupled to the main grounding cable of the entire vehicle. The signal acquisition actions of the broadband electric field probe and the high-frequency current probe are synchronously triggered by the same time base signal source.

[0018] Furthermore, for each test condition, the frequency points where the radiated emission exceeds the standard under that test condition are identified. Specifically, this means: performing a fast Fourier transform on the time-domain radiated field signal of the whole vehicle captured under that test condition, converting it to the frequency domain, obtaining the corresponding frequency-domain radiated spectrum, comparing the frequency-domain radiated spectrum with the preset electromagnetic compatibility standard limit line, and filtering out all frequency points in the frequency-domain radiated spectrum whose spectral amplitude exceeds the electromagnetic compatibility standard limit line. These frequency points are recorded as the frequency points exceeding the standard under that test condition.

[0019] For each out-of-standard frequency point identified under this test condition, the spectral amplitude at the out-of-standard frequency point is obtained by performing spectral analysis on the time-domain radiation field signal, and converted into the radiation field strength amplitude under this test condition according to the calibration coefficient; the spectral analysis is performed on the synchronously captured ground loop common-mode current signal to extract the current spectral amplitude at the same out-of-standard frequency point; the obtained radiation field strength amplitude at this frequency point is used as a parameter characterizing the equivalent voltage of the ground loop port, and based on Ohm's law, the radiation field strength amplitude is divided by the current spectral amplitude to calculate the ground loop impedance amplitude at the out-of-standard frequency point under this test condition;

[0020] The amplitude of the radiated field strength and the amplitude of the ground loop impedance measured at this out-of-standard frequency point under the reference operating condition are used as the reference radiated field strength and the reference ground loop impedance, respectively. The relative rate of change of the radiated field strength amplitude relative to the reference radiated field strength is calculated as the relative rate of change of the radiated field strength at this out-of-standard frequency point under the test operating condition, and the relative rate of change of the ground loop impedance amplitude relative to the reference ground loop impedance is calculated as the relative rate of change of the ground loop impedance at this out-of-standard frequency point under the test operating condition.

[0021] Furthermore, the calculation logic of the fault sensitivity factor is as follows: for any test condition, the absolute value of the ratio between the relative change rate of radiation field strength and the relative change rate of loop impedance at any frequency point exceeding the standard is calculated, and used as the fault sensitivity factor at this frequency point exceeding the standard under this test condition.

[0022] The elements in the same row of the fault feature fingerprint matrix are the fault sensitivity factors of each frequency point exceeding the standard under the same test condition. The element in the i-th row and j-th column of the fault feature fingerprint matrix is ​​the fault sensitivity factor calculated at the j-th frequency point exceeding the standard under the i-th test condition. i is the index of the test condition and j is the index of the frequency point exceeding the standard under the test condition.

[0023] Furthermore, the constructed fault feature fingerprint matrix is ​​matched with various typical noise source fault mode templates. Specifically, this means: calculating the similarity metric between the fault feature fingerprint matrix and various typical noise source fault mode templates; comparing all similarity metric values ​​and selecting the fault mode template corresponding to the highest metric value; and determining the noise source type represented by the template as the main fault source causing the vehicle's radiated emissions to exceed the standard.

[0024] Furthermore, the generated structured diagnostic report specifically includes: based on the determination results of the main fault source, the report generates a diagnostic conclusion containing information on the category of the main fault source, and highlights the area where the inferred main fault source is located on the 3D model of the whole vehicle, and provides a list of rectification measures. This list is directly related to the diagnosed main fault source type, and the specific measures include grounding optimization, filter addition and shielding enhancement for the area where the fault source is located.

[0025] The present invention also provides a detection device for electromagnetic compatibility radiated emissions of a vehicle, the device being used to perform the above-described detection method for electromagnetic compatibility radiated emissions of a vehicle, comprising:

[0026] The unit setting module is used to fix the vehicle under test on the insulating support fixture in the electromagnetic compatibility anechoic chamber and set a digital ground plane array at the reference ground plane under the vehicle chassis. The array is composed of metal ground units.

[0027] The working condition judgment module is used to control the on / off state of the metal ground unit based on the test control host to construct a fully grounded reference working condition between the vehicle chassis and the reference ground, as well as a variety of test working conditions with different ground loop impedance distributions, and each working condition corresponds to a set of ground unit on / off combinations.

[0028] The matrix construction module is used to synchronously capture and analyze the time-domain radiation field signal of the whole vehicle and the common-mode current signal of the ground loop flowing into the array after the test conditions stabilize. It identifies the out-of-standard frequency points where the radiated emission exceeds the standard, calculates the rate of change of the radiation field strength and the ground loop impedance relative to the reference condition at each out-of-standard frequency point, quantifies the fault sensitivity factor at each out-of-standard frequency point under the test condition based on the numerical relationship between the two, and arranges all the fault sensitivity factors in an orderly manner to construct a fault feature fingerprint matrix.

[0029] The fault diagnosis module is used to match the fault feature fingerprint matrix with various typical noise source fault mode templates, select the fault mode template with the highest matching degree, and the corresponding noise source type is diagnosed as the main fault source causing the vehicle's radiation emissions to exceed the standard. A structured diagnostic report is generated based on the diagnostic results.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention fundamentally changes the limitation of traditional radiated emission testing, which can only passively determine whether emissions exceed limits, by constructing a test platform that can actively control the distribution of the vehicle's ground loop impedance and establishing a set of excitation response analysis and feature matching diagnostic processes that work in tandem with it. Its core benefit lies in its ability to accurately identify and spatially locate internal noise sources that cause excessive radiation, thereby greatly improving the efficiency of problem rectification. The realization of this effect relies first on the dynamic ground loop impedance excitation method proposed in this invention. By controlling the digital ground plane array to generate a series of standardized test conditions ranging from good global grounding to local grounding deficiency, the radiation response of the common-mode noise current inside the vehicle under different leakage paths is systematically excited. This active flaw detection test provides rich data dimensions that cannot be obtained by traditional single fixed grounding state tests, revealing the implicit correlation between radiation characteristics and grounding structure.

[0032] This invention synchronously acquires radiation field and loop current signals, and innovatively quantifies their rate of change into a fault sensitivity factor, constructing a high-dimensional feature fingerprint that can characterize the unique leakage mechanism of noise sources. This data processing method enables electromagnetic faults with different physical roots, such as insufficient filtering or poor shielding, to be effectively distinguished in the feature space because they have different response modes to ground loop disturbances, laying a reliable foundation for the realization of automated fault classification.

[0033] This invention intelligently matches measured feature fingerprints with a pre-set fault mode database and combines this with analysis of the spatial location of ground units corresponding to sensitive test conditions. This invention can automatically output a structured diagnostic report containing specific fault types, suspected locations, and targeted rectification suggestions. This process frees engineers from manual trial and error that relies on experience, transforming vehicle electromagnetic compatibility testing from a compliance verification activity into an efficient diagnostic and design guidance tool, significantly shortening product development cycles and reducing later rectification costs. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall method flow of the present invention;

[0035] Figure 2 This is a curve showing the absolute change in radiation field strength versus the fault sensitivity factor in this invention.

[0036] Figure 3 This is a scatter plot showing the absolute change in the fault sensitivity factor - ground loop impedance of this invention.

[0037] Figure 4 This is a flowchart of the overall device structure of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0039] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0040] Example:

[0041] Please see Figures 1-3 The present invention provides a technical solution:

[0042] A method for detecting electromagnetic compatibility radiated emissions from a vehicle, comprising the following steps:

[0043] Step 1: Fix the vehicle under test on the insulating support fixture in the electromagnetic compatibility anechoic chamber, and set up a digital ground plane array at the reference ground plane under the vehicle chassis. The array is composed of metal ground units.

[0044] The vehicle under test is fixed on an insulating support fixture in an electromagnetic compatibility anechoic chamber. Specifically, a special support fixture made of insulating material is used to lift the vehicle tires off the metal reference ground plane of the anechoic chamber and maintain a defined physical isolation space between the vehicle chassis and the metal reference ground plane of the anechoic chamber without any direct electrical contact, thereby simulating the insulation state of the vehicle in actual driving.

[0045] In a specific implementation, the vehicle under test is fixed to an insulating support fixture in an electromagnetic compatibility anechoic chamber. The fundamental purpose is to construct a stable and repeatable reference physical environment for subsequent testing. When the vehicle is driving on actual roads, its chassis is insulated from the ground through rubber tires, and there is no stable low-impedance electrical connection between the vehicle body and the ground. The vehicle body's ground potential and common-mode current loop are mainly affected by distributed parameters. In order to accurately reproduce and study this state in the laboratory anechoic chamber, the vehicle must be electrically isolated from the laboratory's inherent metal grounding plane. Therefore, a special support fixture made of high-insulation-strength materials, such as polytetrafluoroethylene or ceramic matrix composites with extremely high volume resistivity, is required.

[0046] During operation, the four tires of the vehicle are placed smoothly into the customized support groove on the top of the tooling using a lifting device to ensure that the vehicle is level and stable. At this time, a height-defined air gap isolation space is formed between the vehicle chassis and the metal reference ground plane of the darkroom. This gap distance is set to a fixed value, such as 300 mm or 500 mm, according to the test standard or the vehicle's minimum ground clearance. This operation effectively simulates the insulation state of the real vehicle and eliminates any direct, uncontrolled DC or low-frequency electrical path between the chassis and the laboratory ground, making the controlled grounding introduced subsequently through the digital ground plane array the only dominant human factor affecting the radiation characteristics of the vehicle.

[0047] Setting up a digital ground plane array at the reference ground plane under the vehicle chassis specifically means: installing a digital ground plane array consisting of several independent metal patches in a preset area of ​​the reference ground plane in the anechoic chamber. Each metal patch serves as a metal ground unit, and each metal ground unit is controlled by a high-speed radio frequency switch controlled by the test control host to control the electrical connection between the metal ground unit and the system reference ground network. The high-speed radio frequency switch is controlled by the test control host to switch the corresponding metal ground unit between an electrically connected state and a high-impedance disconnected state.

[0048] The reason for setting up a digital ground plane array at the reference ground plane under the vehicle chassis is that traditional whole vehicle radiated emission testing only establishes a fixed, global low-impedance ground between the vehicle under test and the anechoic chamber ground plane. This static grounding mode cannot effectively diagnose electromagnetic compatibility faults caused by poor local grounding or uneven distribution of ground loop impedance. The core innovation of the digital ground plane array proposed in this invention is to transform a originally continuous and physically fixed metal reference ground plane into a dynamic network composed of many independent and controllable metal ground units in a specific area. In specific implementation, a customized module is embedded in a rectangular area on the anechoic chamber metal ground plane corresponding to the projection of the vehicle chassis. The substrate of the module is an insulating material, and dozens or even hundreds of independent metal patches are arranged in a grid pattern on its upper surface. Each such metal patch is defined as a metal ground unit.

[0049] The electrical state of each metal ground unit is not fixed, but dynamically controlled by a high-speed radio frequency switch. The high-speed radio frequency switch mentioned here refers to a semiconductor or electromechanical component that can respond to external electrical signal commands and realize the closure and opening of the radio frequency path within nanosecond to microsecond time. For example, a solid-state switch based on PIN diode or a high-performance miniature radio frequency relay. One end of each switch is soldered to the corresponding metal patch, and the other end is connected to the unified grounding busbar inside the module. This busbar is finally reliably connected to the main grounding system of the anechoic chamber. The control cables of all switches converge and are connected to the test control host located outside the anechoic chamber.

[0050] Within the target frequency band (e.g., 30MHz to 1GHz) for vehicle electromagnetic compatibility radiated emission testing, the insertion loss of the high-speed RF switch in the on state should be better than 1dB to ensure that the metal ground unit presents an approximately ideal short-circuit state with the reference ground network when it is on; the port isolation in the off state should be better than 60dB to ensure that the metal ground unit presents a sufficiently high RF impedance with the reference ground network when it is off, so as to realistically simulate the fault state of grounding failure; the switching time of the switch should be on the order of microseconds or faster to ensure that it can quickly enter the electromagnetic steady state when switching between different test conditions.

[0051] Step 2: Based on the test control host, control the on / off state of the metal ground unit to construct a fully grounded reference condition between the vehicle chassis and the reference ground, as well as a variety of test conditions with different ground loop impedance distributions, and each condition corresponds to a set of ground unit on / off combinations.

[0052] In a specific implementation, the core step of realizing proactive fault diagnosis is to construct a series of test conditions by controlling the on / off state of the metal ground unit based on the test control host. This step aims to systematically stimulate and observe the response of the vehicle's electromagnetic system under different grounding conditions by programmatically changing the electrical connection topology between the vehicle chassis and the ground, thereby extracting fault characteristics.

[0053] A fully grounded reference condition is constructed between the vehicle chassis and the reference ground, along with various test conditions exhibiting different ground loop impedance distributions. Specifically, this refers to:

[0054] All metal ground units in the digital ground plane array are turned on to construct a fully grounded reference condition between the vehicle chassis and the reference ground. The test control host sequentially controls one or more high-speed radio frequency switches of the digital ground plane array to turn off according to preset modes, so that it presents a series of different ground unit on / off combinations. The preset modes include turning off individual metal ground units according to the vehicle chassis area division sequence, turning off multiple non-adjacent metal ground units in combination, and performing ground unit on / off combinations covering specific impedance distribution scenarios, thereby constructing a series of test conditions.

[0055] First, a fully grounded reference condition needs to be constructed as a comparison benchmark. This reference condition is defined as the state in which the entire vehicle chassis achieves a global, low-impedance electrical connection with the anechoic chamber reference ground through the digital ground plane array. The specific technical operation is as follows: the test control host sends a closing command to all high-speed radio frequency switches in the digital ground plane array simultaneously. When all switches are closed, each metal ground unit in the array forms a reliable electrical connection with the system reference ground network through its corresponding switch path. At this time, looking down from the perspective of the entire vehicle chassis, there is a complete and continuous low-impedance metal ground plane below it. This simulates the extreme case where all potential grounding points of the vehicle are in an ideal connection state. The radiation and current data measured under this reference condition will serve as the reference origin for measuring changes in all subsequent analysis and calculations.

[0056] After the baseline operating condition is established and the test is completed, the next step is to construct a series of test operating conditions aimed at revealing faults. Test operating condition is a core concept defined in this solution. It specifically refers to a certain non-globally grounded metal ground unit on / off combination state formed by controlling the digital ground plane array. Each unique state corresponds to a spatial distribution pattern of ground loop impedance, thus constituting an independent test condition. The test control host has pre-stored an engineering-designed test sequence, which specifies in detail the generation order of multiple test operating conditions and their corresponding specific switch on / off instruction sets.

[0057] When executing the test sequence, the control host will call and execute each operating condition command in sequence. Taking a command as an example, its content is actually a binary control word corresponding to all high-speed RF switches in the array. "1" means that the command is closed and "0" means that the command is open. The host sends this control word to the array through the digital interface card. Each high-speed RF switch completes the state switching synchronously within a very short time (usually in the microsecond range) after receiving the command. When all the switches have completed their actions and the system reaches a new steady state, a new grounding network different from the reference operating condition is formed under the vehicle chassis. This is how a new test operating condition is established.

[0058] The design of the preset modes in the test sequence has a clear diagnostic orientation. The single metal ground unit disconnection mode, which is performed according to the division of the vehicle chassis area, means that the area covered by the digital ground plane array is divided into areas such as front left, front right, rear left, rear right, or corresponding specific components such as battery pack, motor, and electronic control unit, based on the physical structure of the vehicle chassis above it. The control host sequentially commands to disconnect only one metal ground unit belonging to a specific area, while keeping all other units connected. This mode aims to examine in isolation the impact on the radiation characteristics of the whole vehicle when a single grounding point fails in a local location of the vehicle chassis, and can be used to initially locate the area most sensitive to grounding.

[0059] The combined disconnection mode of multiple non-adjacent metal ground units refers to the command to simultaneously disconnect two or more metal ground units that are not directly adjacent in physical space. This mode is designed to simulate complex fault scenarios in which a vehicle experiences grounding failures at multiple distant locations simultaneously, such as simultaneous corrosion of the front and rear suspension grounding points. This condition can induce more complex common-mode current loops and test the system's response characteristics to distributed grounding faults.

[0060] Performing ground cell switching combinations covering specific impedance distribution scenarios is a higher-order diagnostic mode. Its goal is no longer simple switching, but to construct impedance distribution scenarios with specific engineering significance under the vehicle chassis through carefully designed combinations of multiple switches. For example, by disconnecting an entire row of metal ground cells on one side while keeping the other side connected, a scenario with severe asymmetry in the left and right grounding of the whole vehicle can be simulated. By alternately switching on and off in a checkerboard pattern, a scenario with high-frequency impedance periodic changes in the grounding network can be simulated. These pre-set complex scenarios are designed to specifically expose specific types of electromagnetic compatibility design defects.

[0061] Step 3: After the test conditions stabilize, the time-domain radiation field signal of the whole vehicle and the common-mode current signal of the ground loop flowing into the array are captured and analyzed simultaneously. The frequency points where the radiated emission exceeds the standard are identified. The rate of change of the radiation field strength and the ground loop impedance relative to the reference condition are calculated at each frequency point. Based on the numerical relationship between the two, the fault sensitivity factor at each frequency point under the test condition is quantified. All the fault sensitivity factors are arranged in an orderly manner to construct a fault feature fingerprint matrix.

[0062] In a specific implementation, the core task of step three is to simultaneously acquire the electromagnetic radiation and ground loop response of the whole vehicle under each test condition constructed by the digital ground plane array, and to convert these response data into quantitative features that can characterize the sensitivity of the system to ground loop disturbances, ultimately forming a digital fingerprint that can be used for pattern recognition.

[0063] After each test condition stabilizes, the time-domain radiation field signal of the entire vehicle and the common-mode current signal flowing into the array are captured synchronously. Specifically, this includes: synchronously acquiring the time-domain radiation field voltage signal of the entire vehicle through at least four broadband electric field probes arranged around the entire vehicle; and simultaneously acquiring the common-mode current signal flowing into the digital ground plane array through a high-frequency current probe coupled to the main grounding cable of the entire vehicle. The signal acquisition actions of the broadband electric field probe and the high-frequency current probe are synchronously triggered by the same time base signal source.

[0064] Specifically, after the electrical state of each test condition is stabilized, two types of signals need to be captured simultaneously. The first type of signal is the time-domain radiated field signal of the whole vehicle. This signal is acquired by installing at least four broadband electric field probes at specific locations around the vehicle's perimeter in an electromagnetic compatibility anechoic chamber. A broadband electric field probe is a sensor that can sense changes in electric field within a specific frequency range and convert them into a proportional voltage signal. These probes are arranged in accordance with standard test specifications in the four main directions of the vehicle (front, rear, left, and right) at a specified distance from the vehicle body to ensure that the electromagnetic field radiated outward by the whole vehicle can be fully captured. The voltage signal output by the probe is the time-domain radiated field voltage signal.

[0065] The second type of signal is the common-mode current signal flowing into the digital ground plane array. Common-mode current refers to the current component flowing through the vehicle's main grounding cable and returning to the ground. It is a key indicator for evaluating the effectiveness of the grounding system and radiated leakage. This signal is acquired by coupling a high-frequency current probe to the vehicle's main grounding cable. The high-frequency current probe adopts a clamp-on structure, the core of which is a magnetic ring. When the cable passes through the magnetic ring, the magnetic field generated by the current in the cable will induce a voltage signal proportional to it in the detection coil of the magnetic ring, thereby realizing non-contact measurement of the current. To ensure the timing consistency of subsequent analysis, the signal acquisition actions of the broadband electric field probe and the high-frequency current probe must be strictly synchronized. This is achieved by using the same high-precision time base signal source to provide a unified sampling clock trigger signal for all data acquisition devices, thereby ensuring that the time-domain waveforms acquired by all channels are completely aligned on the time axis.

[0066] The test control host integrates or connects to a highly stable clock generator as the common time base for the entire data acquisition system. This clock generator simultaneously outputs two synchronization signals: one as a sampling clock, which is directly fed to the clock input ports of all data acquisition devices connected to the broadband electric field probes and high-frequency current probes, forcing all channels to perform analog-to-digital conversion at exactly the same time and rate; the other as a trigger enable signal, which is issued by the control host after each test condition has stabilized. This signal is simultaneously sent to each acquisition device, commanding all channels to begin a synchronous acquisition. This architecture ensures that the time-domain waveforms obtained from different physical locations and different types of sensors have a strict point-to-point correspondence on the time axis, which is a necessary condition for the subsequent accurate calculation of the ground loop impedance amplitude.

[0067] For each test condition, identify the frequency points where radiated emissions exceed the standard under that test condition. Specifically, this means: performing a fast Fourier transform on the time-domain radiated field signal of the whole vehicle captured under that test condition, converting it to the frequency domain, obtaining the corresponding frequency-domain radiated spectrum, comparing the frequency-domain radiated spectrum with the preset electromagnetic compatibility standard limit line, and filtering out all frequency points in the frequency-domain radiated spectrum whose spectral amplitude exceeds the electromagnetic compatibility standard limit line. These frequency points are recorded as the frequency points exceeding the standard under that test condition.

[0068] After signal acquisition, for the current test conditions, it is necessary to identify the frequency points where radiated emissions exceed the regulatory limits, i.e., the out-of-standard frequency points. Specifically, the acquired vehicle time-domain radiated field signal is subjected to a Fast Fourier Transform (FFT) to convert it from the time domain to the frequency domain, resulting in a curve characterizing the distribution of radiated energy with frequency, i.e., the frequency domain radiation spectrum. This spectrum curve is then compared with the preset radiated emission limit lines that comply with the corresponding national or international electromagnetic compatibility standards. The limit line is a curve that defines the maximum allowable radiated field strength at different frequency points. Through an automatic comparison algorithm, all discrete frequency points in the spectrum curve whose amplitude values ​​exceed the upper limit line of the corresponding frequency point are selected. These frequency points are recorded as the set of out-of-standard frequency points specific to this test condition.

[0069] For each out-of-standard frequency point identified under this test condition, the spectral amplitude at the out-of-standard frequency point is obtained by performing spectral analysis on the time-domain radiation field signal, and converted into the radiation field strength amplitude under this test condition according to the calibration coefficient; the spectral analysis is performed on the synchronously captured ground loop common-mode current signal to extract the current spectral amplitude at the same out-of-standard frequency point; the obtained radiation field strength amplitude at this frequency point is used as a parameter characterizing the equivalent voltage of the ground loop port, and based on Ohm's law, the radiation field strength amplitude is divided by the current spectral amplitude to calculate the ground loop impedance amplitude at the out-of-standard frequency point under this test condition;

[0070] It should be noted that for each identified frequency exceeding the standard, two key parameters need to be calculated: the amplitude of the radiation field strength under the current operating conditions and the amplitude of the ground loop impedance. The calculation process of the radiation field strength amplitude is as follows: First, directly read the spectral amplitude corresponding to the frequency exceeding the standard from the frequency domain radiation spectrum obtained by the fast Fourier transform. This value is in voltage units. Then, multiply this voltage amplitude by the field strength conversion coefficient of the broadband electric field probe at that specific frequency, which is obtained in advance through calibration, so as to obtain the actual radiation field strength amplitude in volts per meter or decibels microvolts per meter.

[0071] The calculation of the ground loop impedance amplitude is derived based on basic circuit theory. At a specific frequency, the port formed by the vehicle chassis and the digital ground plane array is regarded as an equivalent network. The radiation field strength amplitude calculated at the out-of-standard frequency point is regarded as a characterizing parameter of the equivalent common-mode voltage amplitude at this port. At the same time, the same spectrum analysis is performed on the synchronously acquired time-domain ground loop common-mode current signal to extract the current spectrum amplitude at the same out-of-standard frequency point. Finally, according to Ohm's law, impedance is equal to the ratio of voltage to current. The calculated radiation field strength amplitude is divided by the extracted current spectrum amplitude to obtain the ground loop impedance amplitude at the out-of-standard frequency point under the test condition. This is an engineering method of inferring the internal impedance of the system through external measurement.

[0072] The amplitude of the radiated field strength and the amplitude of the ground loop impedance measured at this out-of-standard frequency point under the reference operating condition are used as the reference radiated field strength and the reference ground loop impedance, respectively. The relative rate of change of the radiated field strength amplitude relative to the reference radiated field strength is calculated as the relative rate of change of the radiated field strength at this out-of-standard frequency point under the test operating condition, and the relative rate of change of the ground loop impedance amplitude relative to the reference ground loop impedance is calculated as the relative rate of change of the ground loop impedance at this out-of-standard frequency point under the test operating condition.

[0073] Specifically, to quantify the impact of grounding disturbances under the current test conditions, the concept of rate of change needs to be introduced. Here, two reference values ​​that were pre-measured and stored at the same out-of-range frequency point under the full grounding reference condition are called: the reference radiation field strength and the reference ground loop impedance. The relative rate of change of the radiation field strength amplitude at this frequency point under the current test condition with respect to the reference radiation field strength is calculated. This rate of change reflects the degree of change in the radiation field caused by the grounding change. Similarly, the relative rate of change of the current ground loop impedance amplitude with respect to the reference ground loop impedance is calculated. This rate of change directly reflects the degree of change in the grounding state itself.

[0074] The calculation logic of the fault sensitivity factor is as follows: For any test condition, the absolute value of the ratio of the relative change rate of the radiation field intensity and the relative change rate of the loop impedance at any frequency point exceeding the standard is calculated, and it is used as the fault sensitivity factor of this frequency point exceeding the standard under this test condition.

[0075] The elements in the same row of the fault feature fingerprint matrix are the fault sensitivity factors of each frequency point exceeding the standard under the same test condition. The element in the i-th row and j-th column of the fault feature fingerprint matrix is ​​the fault sensitivity factor calculated at the j-th frequency point exceeding the standard under the i-th test condition. i is the index of the test condition and j is the index of the frequency point exceeding the standard under the test condition.

[0076] The fault sensitivity factor is a core quantitative indicator defined in this scheme. It is used to characterize the sensitivity of radiation characteristics at a specific frequency to changes in a specific grounding mode. The calculation logic is as follows: For the current test condition and the current frequency exceeding the standard, take the relative change rate of radiation field strength and the relative change rate of ground loop impedance calculated earlier, and calculate the absolute value of the ratio between the two. This absolute value is defined as the fault sensitivity factor of the test condition at the frequency exceeding the standard. Its physical meaning is that if a small change in ground loop impedance causes a drastic change in radiation field strength, the ratio will be large, indicating that the system is very sensitive at this test condition and frequency, and there will be design weaknesses or potential faults related to this grounding mode.

[0077] The specific formula for the fault sensitivity factor is:

[0078]

[0079] in, For the first Under the first test condition, at the first The fault sensitivity factor is calculated at each frequency point exceeding the standard. To be under the fully grounded reference condition, at the first The radiation field strength amplitude measured at each frequency exceeding the standard point establishes a radiation horizontal baseline without additional grounding disturbance. To ensure that, under the fully grounded reference condition, at the first The ground loop impedance amplitude calculated at each out-of-standard frequency point represents the intrinsic impedance baseline of the vehicle grounding system at that frequency point. In the first Under the same test condition, at the same test point The amplitude of the radiation field measured at each frequency exceeding the standard. In the first Under the same test condition, at the same test point The ground loop impedance amplitude calculated at each out-of-standard frequency point reflects the effect of a specific ground loop disturbance (the first...) After the first test condition, in the... Response results at each frequency point exceeding the standard;

[0080] The absolute change in radiation field strength Both represent the absolute change in ground loop impedance and quantify the absolute change in physical quantities caused by the change in test conditions. and These are the relative rates of change of radiation field strength and ground loop impedance, respectively. The absolute changes are normalized to their respective reference values, eliminating the influence of the magnitude of the reference values ​​themselves between different frequency points, so that the sensitivity between different frequency points can be compared fairly.

[0081] Ratio operation The calculation is the ratio of the normalized change in radiation response to the normalized disturbance of grounding impedance. This ratio essentially defines a sensitivity coefficient. If its value is large, it means that a small deterioration in the grounding condition (small denominator) will lead to a sharp increase in radiation (large numerator). This indicates that the radiation characteristics of the frequency point exceeding the standard are extremely sensitive to this type of grounding disturbance (test condition). This often points to a design defect or potential fault closely related to the grounding path.

[0082] Take absolute value Ensure fault sensitivity factor Always a non-negative scalar, in actual physical systems, whether an increase in impedance leads to increased radiation (positive correlation) or a certain resonance leads to an increase in impedance but a decrease in radiation (negative correlation), the strength of the correlation is worth paying attention to. Taking the absolute value aims to capture the strength of this correlation, rather than getting bogged down in the positive or negative direction of the change.

[0083] Specific data for some test conditions and fault sensitivity factors are shown in Table 1.

[0084] Table 1. Statistical data on fault sensitivity factors

[0085]

[0086] Analysis of the data revealed a certain correlation between different characteristic parameters. For example, the data showed a clear trend of co-current change between the change in ground loop impedance and the change in radiated field strength. As the test progressed, when the ground loop impedance increased positively relative to the reference value, the radiated field strength also increased; conversely, when the impedance decreased negatively, the radiated field strength decreased accordingly. This indicates that changes in the grounding status of the vehicle chassis directly affect its radiated emission level. An increase in grounding impedance provides a more significant leakage path for common-mode noise current, thereby leading to an increase in radiated field strength.

[0087] When analyzing the relationship between the test condition sequence and the fault sensitivity factor, it was found that the fault sensitivity factor generally showed a gradual upward trend as the test condition number increased. For example, the fault sensitivity factor value was relatively low in the initial test condition, but generally increased in subsequent test conditions. This reflects that under the specific grounding disturbance mode applied later, the vehicle's radiated emission characteristics are more sensitive to changes in ground loop impedance, which means that these conditions will more effectively stimulate potential fault coupling paths. This trend provides a clear clue for identifying the key grounding mode that contributes the most to radiation exceedance.

[0088] Ultimately, the fault sensitivity factors calculated for all test conditions at all out-of-standard frequency points need to be organized into a structured dataset, namely the fault feature fingerprint matrix. This matrix is ​​a two-dimensional mathematical structure, where each row corresponds to a test condition and each column corresponds to an out-of-standard frequency point sorted according to a unified rule. The element in the i-th row and j-th column of the matrix is ​​the fault sensitivity factor calculated for the i-th test condition at the j-th out-of-standard frequency point. In this way, each test condition is mapped to a row vector, which comprehensively describes the sensitivity response spectrum of the entire vehicle at each out-of-standard frequency point under the grounding disturbance mode. The entire fault feature fingerprint matrix encodes the complete high-dimensional response mode of the vehicle's electromagnetic system to a series of systematic grounding disturbances, providing a unique digital fingerprint for subsequent intelligent diagnosis.

[0089] Step 4: Match the fault feature fingerprint matrix with various typical noise source fault mode templates, select the fault mode template with the highest matching degree, and the corresponding noise source type is diagnosed as the main fault source causing the vehicle's radiation emissions to exceed the standard. Generate a structured diagnostic report based on the diagnostic results.

[0090] In a specific implementation, the core task of step four is to achieve intelligent diagnosis and result output. This step compares and analyzes the fault feature fingerprint matrix obtained in the previous steps, which characterizes the vehicle's response to systematic grounding disturbances, with a pre-established knowledge base, thereby automatically identifying the root cause of the fault most likely to cause radiation exceeding the standard and generating a clear report to guide engineering rectification.

[0091] The constructed fault feature fingerprint matrix is ​​matched with feature templates of various typical noise source fault modes. Specifically, this means: calculating the similarity metric between the fault feature fingerprint matrix and the fault mode templates of various typical noise source fault modes; by comparing all similarity metrics, selecting the fault mode template corresponding to the highest metric value; and determining the type of noise source represented by the template as the main fault source causing the vehicle's radiated emissions to exceed the standard.

[0092] The first step is pattern matching, which aims to identify the fault type that best matches the current measured data from numerous possibilities. The various typical noise source fault mode templates described here are a pre-built database, where each record represents a known and common vehicle electrical noise source fault mode. These modes are derived from prior knowledge, historical fault case libraries, or specific tests on known faulty components. For example, a typical mode could be the failure of the DC bus filter capacitor in the drive motor controller, or poor grounding of the in-vehicle infotainment system's main unit casing. Each fault mode uses the exact same test sequence and data processing flow as the actual measurement process, pre-constructing a standard fault feature fingerprint matrix. This standard matrix is ​​the fault mode template. Each row of the fault mode template matrix also represents a test condition, and each column represents an out-of-standard frequency point. The element values ​​reflect the theoretical sensitivity of each out-of-standard frequency point under each grounding test condition under the known fault state.

[0093] The core of the matching process is to calculate the similarity metric between the measured fault feature fingerprint matrix and each fault mode template matrix in the database. The similarity metric is a quantitative scalar value used to objectively measure the degree of closeness or similarity between the response modes represented by the two matrices as a whole. In a specific embodiment of the present invention, the calculation of this value adopts a matrix similarity evaluation algorithm.

[0094] First, the two-dimensional fault feature fingerprint matrix and template matrix are converted into one-dimensional feature vectors respectively. The conversion rule must be consistent with the row and column order when constructing the matrix to ensure consistency. Then, the cosine similarity between the two feature vectors is calculated. The method for calculating the cosine similarity is as follows: first, calculate the dot product of the two vectors, then calculate the Euclidean norm (i.e., the magnitude) of the two vectors respectively, and finally divide the dot product by the product of the two magnitudes. The result is a value between 0 and 1. The closer the value is to 1, the more consistent the directions of the two vectors are, that is, the more similar the measured response mode is to the mode of the fault template. By calculating the cosine similarity between the measured matrix and all template matrices in the database, a series of similarity measures can be obtained.

[0095] By comparing all the calculated similarity metrics, the one with the highest similarity value is selected. The fault mode template corresponding to the highest value is determined to be the mode that best matches the current vehicle state. Then, the known noise source type represented by the template is determined to be the main fault source causing the current tested vehicle's radiated emissions to exceed the standard. For example, if the template with the highest matching degree corresponds to a poor solder joint at the grounding point of the left front wheel speed sensor shielding harness, then the diagnosis conclusion is that it is the main fault source.

[0096] Furthermore, the generated structured diagnostic report specifically includes: based on the determination results of the main fault source, the report generates a diagnostic conclusion containing information on the category of the main fault source, and highlights the area where the inferred main fault source is located on the 3D model of the whole vehicle, and provides a list of rectification measures, which is directly related to the diagnosed main fault source type. Specific measures include grounding optimization, filter addition and shielding enhancement for the area where the fault source is located.

[0097] After classifying the main fault sources, the physical location of the fault sources is further inferred. This process is not a direct measurement, but rather inference based on the spatial sensitivity information contained in the fault feature fingerprint matrix. The measured fault feature fingerprint matrix is ​​analyzed to identify fault sensitivity factors with significantly high values. According to the definition of the matrix, each such factor is uniquely associated with a specific test condition and a specific out-of-range frequency. By tracing back to the instruction that generated the test condition, it can be determined which specific combination of metal ground unit on / off states caused this high-sensitivity response. Generally, high-sensitivity factors are concentrated in test condition rows that contain specific metal ground unit disconnections.

[0098] Then, the metal ground units that are disconnected and are involved in these key test conditions are extracted. According to the physical design drawings of the digital ground plane array, the precise geographical coordinates of these metal ground units under the vehicle chassis are known. By mapping these coordinate points onto the three-dimensional digital model of the whole vehicle, one or more key areas can be delineated on the chassis. The changes in the grounding status under these areas have the greatest impact on the radiation characteristics of the whole vehicle. Finally, the electrical topology and wiring harness layout database associated with the three-dimensional model of the whole vehicle is queried to find which electrical components, wiring harness segments or grounding points are located or directly pass through the above key areas, are within the intersection range, and whose functional characteristics are consistent with the main fault source type diagnosed in the previous step. These components or lines are then presumed by the system as the most likely actual fault point or noise leakage path. For example, if the main fault source is diagnosed as poor shielding of the left front wheel speed sensor wiring harness and the spatial positioning points to the area inside the left front wheel arch, then the wheel speed sensor wiring harness connector in this area is highlighted.

[0099] Based on the above diagnostic results, a structured diagnostic report is generated. This report is not a simple statement of conclusions, but an engineering guidance document containing multi-level information. First, the report clearly gives the diagnostic conclusions and clearly indicates the type of the main fault source, such as: main fault source: common mode inductor saturation at the power input of the battery management system main control board.

[0100] Secondly, the report combines the reverse analysis of the location of sensitive metal ground units based on the fault sensitivity factor in step three, and associates the abstract fault type with the specific physical location of the vehicle. On the three-dimensional digital model of the whole vehicle, the area where the inferred main fault source is most likely to exist is highlighted. For example, the installation location of the battery management system in the engine compartment is covered with a red flashing area, thereby providing intuitive spatial positioning information.

[0101] The final report generates a list of actionable corrective actions directly linked to the diagnosed primary fault types. This list draws upon a pre-stored knowledge base of corrective actions for different fault modes. For example, for diagnosing saturation of the common-mode inductor at the power input, the corrective action list would specifically include: checking and confirming the integrity of the grounding of the DC harness shielding supplying the battery management system at both ends; measuring and replacing the saturated common-mode inductor with a higher rated current model; and adding a high-frequency filter capacitor in parallel at the power input. Each measure specifically targets the area or related circuitry where the fault originates, achieving a complete closed-loop output from problem diagnosis to solution recommendations.

[0102] Please see Figure 4 The present invention also provides a detection device for electromagnetic compatibility radiated emissions of a vehicle, the device being used to perform the above-described detection method for electromagnetic compatibility radiated emissions of a vehicle, comprising:

[0103] The unit setting module is used to fix the vehicle under test on the insulating support fixture in the electromagnetic compatibility anechoic chamber and set a digital ground plane array at the reference ground plane under the vehicle chassis. The array is composed of metal ground units.

[0104] The working condition judgment module is used to control the on / off state of the metal ground unit based on the test control host to construct a fully grounded reference working condition between the vehicle chassis and the reference ground, as well as a variety of test working conditions with different ground loop impedance distributions, and each working condition corresponds to a set of ground unit on / off combinations.

[0105] The matrix construction module is used to synchronously capture and analyze the time-domain radiation field signal of the whole vehicle and the common-mode current signal of the ground loop flowing into the array after the test conditions stabilize. It identifies the out-of-standard frequency points where the radiated emission exceeds the standard, calculates the rate of change of the radiation field strength and the ground loop impedance relative to the reference condition at each out-of-standard frequency point, quantifies the fault sensitivity factor at each out-of-standard frequency point under the test condition based on the numerical relationship between the two, and arranges all the fault sensitivity factors in an orderly manner to construct a fault feature fingerprint matrix.

[0106] The fault diagnosis module is used to match the fault feature fingerprint matrix with various typical noise source fault mode templates, select the fault mode template with the highest matching degree, and the corresponding noise source type is diagnosed as the main fault source causing the vehicle's radiation emissions to exceed the standard. A structured diagnostic report is generated based on the diagnostic results.

[0107] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0108] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0109] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0110] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method of detecting electromagnetic compatibility radiated emissions of a complete vehicle, characterized in that, The specific steps include: Step 1: Fix the vehicle under test on the insulating support fixture in the electromagnetic compatibility anechoic chamber, and set up a digital ground plane array at the reference ground plane under the vehicle chassis. The array is composed of metal ground units. Step 2: Based on the test control host, control the on / off state of the metal ground unit to construct a fully grounded reference condition between the vehicle chassis and the reference ground, as well as a variety of test conditions with different ground loop impedance distributions, and each condition corresponds to a set of ground unit on / off combinations. Step 3: After the test conditions stabilize, the time-domain radiation field signal of the whole vehicle and the common-mode current signal of the ground loop flowing into the array are captured and analyzed simultaneously. The frequency points where the radiated emission exceeds the standard are identified. The rate of change of the radiation field strength and the ground loop impedance relative to the reference condition are calculated at each frequency point. Based on the numerical relationship between the two, the fault sensitivity factor at each frequency point under the test condition is quantified. All the fault sensitivity factors are arranged in an orderly manner to construct a fault feature fingerprint matrix. Step 4: Match the fault feature fingerprint matrix with various typical noise source fault mode templates, select the fault mode template with the highest matching degree, and the corresponding noise source type is diagnosed as the main fault source causing the vehicle's radiation emissions to exceed the standard. Generate a structured diagnostic report based on the diagnostic results.

2. The method of claim 1, wherein: The vehicle under test is fixed on an insulating support fixture in an electromagnetic compatibility anechoic chamber. Specifically, a special support fixture made of insulating material is used to lift the vehicle tires off the metal reference ground plane of the anechoic chamber and maintain a defined physical isolation space between the vehicle chassis and the metal reference ground plane of the anechoic chamber without any direct electrical contact, thereby simulating the insulation state of the vehicle in actual driving. A digital ground plane array is set up at the reference ground plane under the vehicle chassis. Specifically, in a preset area of ​​the reference ground plane in the anechoic chamber, a digital ground plane array consisting of several independent metal patches is installed. Each metal patch serves as a metal ground unit. Each metal ground unit is controlled by a high-speed radio frequency switch controlled by the test control host to control the electrical connection between the metal ground unit and the system reference ground network. The high-speed radio frequency switch is controlled by the test control host to switch the corresponding metal ground unit between an electrically connected state and a high-impedance disconnected state.

3. The method for detecting electromagnetic compatibility radiated emissions of a vehicle according to claim 2, characterized in that: A fully grounded reference condition is constructed between the vehicle chassis and the reference ground, along with various test conditions exhibiting different ground loop impedance distributions. Specifically, this refers to: All metal ground units in the digital ground plane array are turned on to construct a fully grounded reference condition between the vehicle chassis and the reference ground. The test control host sequentially controls one or more high-speed radio frequency switches of the digital ground plane array to turn off according to preset modes, so that it presents a series of different ground unit on / off combinations. The preset modes include turning off individual metal ground units according to the vehicle chassis area division sequence, turning off multiple non-adjacent metal ground units in combination, and performing ground unit on / off combinations covering specific impedance distribution scenarios, thereby constructing a series of test conditions. After each test condition stabilizes, the time-domain radiation field signal of the entire vehicle and the common-mode current signal flowing into the array are captured synchronously. Specifically, this includes: synchronously acquiring the time-domain radiation field voltage signal of the entire vehicle through at least four broadband electric field probes arranged around the entire vehicle; and simultaneously acquiring the common-mode current signal flowing into the digital ground plane array through a high-frequency current probe coupled to the main grounding cable of the entire vehicle. The signal acquisition actions of the broadband electric field probe and the high-frequency current probe are synchronously triggered by the same time base signal source.

4. The method for detecting electromagnetic compatibility radiated emissions of a vehicle according to claim 3, characterized in that: For each test condition, identify the frequency points where radiated emissions exceed the standard under that test condition. Specifically, this means: performing a fast Fourier transform on the time-domain radiated field signal of the whole vehicle captured under that test condition, converting it to the frequency domain, obtaining the corresponding frequency-domain radiated spectrum, comparing the frequency-domain radiated spectrum with the preset electromagnetic compatibility standard limit line, and filtering out all frequency points in the frequency-domain radiated spectrum whose spectral amplitude exceeds the electromagnetic compatibility standard limit line. These frequency points are recorded as the frequency points exceeding the standard under that test condition. For each out-of-standard frequency point identified under this test condition, the spectral amplitude at the out-of-standard frequency point is obtained by performing spectral analysis on the time-domain radiation field signal, and then converted into the radiation field strength amplitude under this test condition according to the calibration coefficient. Spectral analysis was performed on the synchronously captured ground loop common-mode current signal to extract the current spectrum amplitude at the same out-of-standard frequency point; the obtained radiation field strength amplitude at this frequency point was used as a parameter characterizing the equivalent voltage of the ground loop port; based on Ohm's law, the radiation field strength amplitude was divided by the current spectrum amplitude to calculate the ground loop impedance amplitude at the out-of-standard frequency point under this test condition. The amplitude of the radiation field strength and the amplitude of the ground loop impedance measured at this frequency point exceeding the standard under the reference operating condition are used as the reference radiation field strength and the reference ground loop impedance, respectively. Calculate the relative rate of change of the radiation field strength amplitude relative to the reference radiation field strength, as the relative rate of change of the radiation field strength at this out-of-standard frequency point under the test conditions, and calculate the relative rate of change of the ground loop impedance amplitude relative to the reference ground loop impedance, as the relative rate of change of the ground loop impedance at this out-of-standard frequency point under the test conditions.

5. The method for detecting electromagnetic compatibility radiated emissions of a vehicle according to claim 4, characterized in that: The calculation logic of the fault sensitivity factor is as follows: For any test condition, the absolute value of the ratio of the relative change rate of the radiation field intensity and the relative change rate of the loop impedance at any frequency point exceeding the standard is calculated, and it is used as the fault sensitivity factor of this frequency point exceeding the standard under this test condition. The elements in the same row of the fault feature fingerprint matrix are the fault sensitivity factors of each frequency point exceeding the standard under the same test condition. The element in the i-th row and j-th column of the fault feature fingerprint matrix is ​​the fault sensitivity factor calculated at the j-th frequency point exceeding the standard under the i-th test condition. i is the index of the test condition and j is the index of the frequency point exceeding the standard under the test condition.

6. The method for detecting electromagnetic compatibility radiated emissions of a vehicle according to claim 5, characterized in that: The constructed fault feature fingerprint matrix is ​​matched with various typical noise source fault mode templates. Specifically, this means: calculating the similarity metric between the fault feature fingerprint matrix and various typical noise source fault mode templates, and selecting the fault mode template corresponding to the highest similarity metric by comparing all similarity metric values. The type of noise source represented by this template is identified as the main fault source causing the vehicle's radiated emissions to exceed the standard.

7. The method for detecting electromagnetic compatibility radiated emissions of a vehicle according to claim 6, characterized in that: The generated structured diagnostic report specifically includes: based on the determination of the main fault source, the report generates a diagnostic conclusion containing information on the category of the main fault source, highlights the area where the inferred main fault source is located on the 3D model of the whole vehicle, and provides a list of rectification measures. This list is directly related to the diagnosed main fault source type, and the specific measures include grounding optimization, filter addition and shielding enhancement for the area where the fault source is located.

8. A detection device for electromagnetic compatibility radiated emissions of a vehicle, characterized in that: The device is used to perform a method for detecting electromagnetic compatibility radiated emissions from a vehicle as described in any one of claims 1-7, comprising: The unit setting module is used to fix the vehicle under test on the insulating support fixture in the electromagnetic compatibility anechoic chamber and set a digital ground plane array at the reference ground plane under the vehicle chassis. The array is composed of metal ground units. The working condition judgment module is used to control the on / off state of the metal ground unit based on the test control host to construct a fully grounded reference working condition between the vehicle chassis and the reference ground, as well as a variety of test working conditions with different ground loop impedance distributions, and each working condition corresponds to a set of ground unit on / off combinations. The matrix construction module is used to synchronously capture and analyze the time-domain radiation field signal of the whole vehicle and the common-mode current signal of the ground loop flowing into the array after the test conditions stabilize. It identifies the out-of-standard frequency points where the radiated emission exceeds the standard, calculates the rate of change of the radiation field strength and the ground loop impedance relative to the reference condition at each out-of-standard frequency point, quantifies the fault sensitivity factor at each out-of-standard frequency point under the test condition based on the numerical relationship between the two, and arranges all the fault sensitivity factors in an orderly manner to construct a fault feature fingerprint matrix. The fault diagnosis module is used to match the fault feature fingerprint matrix with various typical noise source fault mode templates, select the fault mode template with the highest matching degree, and the corresponding noise source type is diagnosed as the main fault source causing the vehicle's radiation emissions to exceed the standard. A structured diagnostic report is generated based on the diagnostic results.

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