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With the rapid development of intelligent connected vehicles and autonomous driving technology, the Global Navigation Satellite System (GNSS), as the core component of location services, has become a key device for intelligent driving. Its positioning accuracy and reliability are directly related to vehicle safety. GNSS is irreplaceable in safety functions such as Accident Emergency Call Systems (AECS) and serves as an important foundation for ensuring vehicle safety operation.
The vehicle electromagnetic environment exhibits significant particularity, mainly reflected in the complex coexistence of multi-device协同 work, high-voltage system operation, and high-frequency signal transmission. The vehicle interior contains strong interference sources such as engine ignition systems (which can generate transient currents up to 100A) and vehicle communication devices (5G band field strength can reach 20V/m), while GNSS itself needs to stably transmit high-frequency signals (such as 1.575GHz GPS signals).
Key Data:
Due to the much higher sensitivity of GPS receiver systems to RF energy compared to general consumer radio products, they are susceptible to interference from tiny radio signals of other electronic devices. GNSS devices without rigorous Electromagnetic Compatibility (EMC) testing may face risks such as positioning drift and signal loss. It is worth noting that simple unintentional radiator tests (such as FCC, CE, PTCRB tests) are insufficient to ensure GNSS performance. Devices may pass such tests but experience actual positioning performance degradation due to electromagnetic interference.
In practical applications, the decisive role of EMC testing in the reliability of automotive GNSS products has been verified. For example, a certain vehicle navigation device failed immunity tests in complex electromagnetic environments due to insufficient shielding effectiveness of the RF module, manifesting as frequent positioning signal loss and significant navigation accuracy degradation, directly affecting user experience and driving safety. This case demonstrates that relying solely on conventional radio tests cannot fully verify the stability of GNSS in actual vehicle environments. Targeted EMC testing is necessary to ensure its reliable operation under extreme electromagnetic conditions.
Domestically, a system centered on specialized standards with supporting standards has been formed for electromagnetic compatibility testing of automotive GNSS products. National standards and group standards协同 cover electromagnetic environment adaptability, electrical safety, and multi-scenario reliability requirements.
As the first domestic specialized EMC standard for automotive GNSS, developed by the National Automotive Standardization Technical Committee with participation from Rosenberger and other units in drafting, it was released on November 28, 2024, and planned for implementation in June 2025. This standard fills an industry gap, clearly specifying electromagnetic compatibility test requirements, including radio disturbance characteristics, conducted and coupled electrical disturbance immunity, electromagnetic radiation immunity, and electrostatic discharge immunity. Among these, the electromagnetic radiation immunity test intensity in the 20MHz~2000MHz frequency band reaches 30V/m (covering over 90% of the frequency band), aligning with international standards.
Focusing on performance verification in complex electromagnetic environments, it specifies general requirements, technical requirements, and inspection methods for test electromagnetic environments, applicable to the entire process including system design, manufacturing, and acceptance. Its core involves using Jamming-to-Signal Ratio (JSR) testing (1~3GHz frequency band) to simulate interference scenarios such as multipath effects and ionospheric delays, and clearly defines indicators such as positioning accuracy (static ≤0.05m) and dynamic velocity measurement accuracy (≤0.01m/s), ensuring positioning reliability of terminals under complex electromagnetic interference.
| Standard Type | Standard Number | Test Item | Technical Parameter | Applicable Scenario |
|---|---|---|---|---|
| Specialized Standard | GB/T 45086.1-2024 | Electromagnetic Radiation Immunity Test (20MHz~2000MHz) | 30V/m (Covering over 90% frequency band) | EMC Testing for Vehicle Satellite Navigation Systems |
| Bulk Current Injection (BCI) Method | 60mA | |||
| Electromagnetic Radiation Immunity Test (Other Frequency Bands) | ≥10V/m | |||
| Test Specification | T/ZKJXX 00004-2023 | Static Positioning Accuracy | ≤0.05m | Performance Verification in Complex Electromagnetic Environment |
| Dynamic Velocity Measurement Accuracy | ≤0.01m/s | |||
| Supporting Standard | GB/T 28046.2-2019 | Power Supply Voltage Transient Variations | Functional Status at least Level B | Electrical Load Testing |
The ECE R10 regulation issued by the United Nations Economic Commission for Europe (UNECE) is the core basis for market access in the European Union and over 50 member countries worldwide, covering vehicles of categories L, M, N, etc., and their Electronic Sub-Assemblies (ESA). It requires that equipment neither generate electromagnetic radiation that interferes with other electronic devices nor need to possess the ability to resist external electromagnetic interference, involving radiation/conducted immunity, emission control, and special requirements for charging coupling systems.
Its revision dynamics reflect technical adaptability. The Rev.7 draft adds testing for the 76GHz~81GHz millimeter-wave radar frequency band and raises the upper frequency limit for radiated immunity to 6GHz, further strengthening requirements for the anti-interference capability of GNSS equipment in complex electromagnetic environments.
Through multi-dimensional testing methods, it constructs an immunity assessment system adapted to the complex vehicle electromagnetic environment. This series specifies diversified testing means for different interference paths and frequency band characteristics.
| Test Method | Covered Frequency Band | Test Principle | Test Accuracy | Cost Investment | Applicable Scenario |
|---|---|---|---|---|---|
| TEM Cell Method | 0.01MHz~200MHz | Transverse Electromagnetic Wave Transmission | Relatively High | Medium | Component, Cable Radiation |
| BCI Method | 100kHz~400MHz | Current Injection Coupling | Relatively High | Low | Equipment Immunity |
| Reverberation Chamber Method | LUF~18GHz | Multi-reflection Environment Statistics | Statistical Average (Relatively Low) | Relatively High | Overall Equipment Radiation, Immunity |
| Anechoic Chamber Method | 80MHz~18GHz | Direct Radiation/Reception | High (Affected by Environment) | High (Requires Anechoic Chamber) | Precise Radiation Emission Testing |
As the core standard for electromagnetic emission control of vehicle electronic components, its 2021 5th Edition (Class 3) imposes stringent requirements on radiated emissions. The quasi-peak limit in the 30MHz~1GHz frequency band is as low as 34dBμV/m, and it covers conducted and radiated emission testing from 150kHz to 5925MHz. This limit requirement is significantly higher than other categories, forcing enterprises to reduce the electromagnetic radiation level of GNSS modules through means such as optimizing PCB layout, increasing electromagnetic shielding, and selecting low-noise components.
The core purpose of Electromagnetic Interference (EMI) testing is to control the electromagnetic radiation of the automotive GNSS product itself to avoid interference with other sensitive electronic devices in the vehicle. Specifically, it is necessary to limit the device's external electromagnetic radiation through radiated emission testing (30MHz~6GHz), and control the electromagnetic interference transmitted through power lines or signal lines through conducted emission testing (150kHz~30MHz), thereby preventing interference with the normal operation of systems such as vehicle radar, communication modules (e.g., 5G T-Box, with risk of communication frequency band overlap), and sensors.
The key difficulty in this test lies in the high-frequency signal characteristics of GNSS products. For example, the 1.575GHz high-frequency signal of GPS is prone to cause radiated emission exceedance through the antenna. In a typical case, a device's radiation intensity at the 450MHz frequency band reached 48dBμV/m, exceeding the standard limit of 40dBμV/m; conducted emission may also exceed limits at specific frequency bands, such as a device's conducted emission value at 2MHz frequency reaching 58dBμV, exceeding the limit of 50dBμV. To address these issues, optimization design is required, including measures such as using shielding covers with shielding effectiveness ≥65dB, optimizing filter circuits, adjusting PWM frequency and signal line layout, etc., to reduce radiation and conducted interference levels to within standard ranges.
Electromagnetic Susceptibility (EMS) testing is a key link in ensuring the reliable operation of automotive GNSS products in complex electromagnetic environments. Its core goal is to verify the functional stability and positioning accuracy of the equipment when subjected to external electromagnetic interference. Specifically, it is necessary to ensure that GNSS, under typical interference scenarios such as high-voltage lines, communication base stations, and vehicle motors, has a static positioning error not exceeding 2 meters and a dynamic positioning error not exceeding 5 meters, while meeting the stringent requirements of international standards for electromagnetic environment adaptability.
Test Methods:
Insufficient immunity capability will directly lead to serious failure risks. Electromagnetic radiation interference may cause positioning drift. For example, in tunnel multipath environments, if the device's immunity to the 30V/m field strength in the 20MHz~2000MHz frequency band is insufficient, causing the Carrier-to-Noise Density Ratio (C/N0) to drop by more than 1dB, it will result in positioning accuracy degradation. Electrostatic discharge may cause device unresponsiveness or restart. A case showed that a touch screen controller experienced functional interruption due to insufficient ESD protection level (original ±8kV), and only passed the test after replacing it with a ±15kV protection chip. RF interference may also cause communication module abnormalities, such as WiFi module disconnection under a 10V/m field strength, which needs to be resolved through band-pass filters (suppression ratio >30dB) and antenna isolation optimization (improved by 15dB).
GNSS-specific performance testing is a key link to ensure the reliable operation of automotive GNSS products in complex electromagnetic environments. From the perspective of testing necessity, GNSS signals are inherently weak (-130dBm@antenna port). The RF power received by ground antennas is typically between -125 dBm and -150 dBm, making them extremely susceptible to electromagnetic interference leading to sensitivity degradation, thereby affecting positioning accuracy and availability.
Testing Necessity
Relevant standards such as CSN ETSI EN 301 489-19 v2.2.1 clearly require satellite communication systems (including GNSS) to provide reliable data transmission, covering various configurations including vehicle-mounted, while CISPR 25:2021 more specifically stipulates the need to protect satellite navigation receivers such as GPS from interference by components in the same vehicle, highlighting the necessity of specialized testing.
| Test Item | Requirement | Unit |
|---|---|---|
| Acquisition Sensitivity | ≤-138 | dBm |
| Tracking Sensitivity | ≤-150 | dBm |
| Positioning Accuracy (Horizontal, Open Area) | <2 | m |
| Multipath Suppression Performance | Error≤5 | m |
| Cold Start Time | <90 | s |
As the core environment for radiated immunity testing, it constructs a reflection-free electromagnetic space through absorbing materials, ensuring test field strength deviation ≤±3dB, guaranteeing the accuracy of radiated immunity test results. For example, a 1m method anechoic chamber can cover the field uniformity requirements for the 150kHz~18GHz frequency range.
Couples interference signals through current probes or injection clamps, simulating vehicle wiring harness conducted interference paths. It can achieve current injection from 0~200mA in the 100kHz~400MHz frequency range, covering component wiring harness conducted immunity testing needs.
Used to simulate multi-constellation signals such as GPS/BDS/GLONASS/Galileo, supports ionospheric and tropospheric delays and user trajectory simulation, providing a controllable signal source for GNSS receiver sensitivity testing.
Small and medium-sized enterprises can prioritize configuring BCI systems and basic immunity equipment (such as signal generators, RF power amplifiers, CDNs, etc.). Such equipment can cover 80% of component conducted immunity testing needs, significantly reducing initial investment. For radiated emission testing, due to the high construction cost of anechoic chambers (including shielded rooms, absorbing materials, test antennas, etc.), it can be outsourced to third-party laboratories, utilizing their CISPR25 standard anechoic chambers to complete testing, balancing testing capability and cost investment.
As the main testing environment, the anechoic chamber needs to have the ability to shield external electromagnetic interference (such as base station signals, high-voltage line radiation) and absorb internal excess signals. Its typical structure includes an anechoic chamber, control room, and amplifier room, covering the 150kHz-18GHz frequency range, meeting EMI RF radiation interference and EMS RF radiation immunity measurement requirements.
Environmental Parameters:
Power end interference isolation relies on the Artificial Mains Network (LISN). Its 50Ω/5μH impedance characteristic is adapted to 12V/24V vehicle power systems, ensuring that conducted emission testing only reflects the electromagnetic characteristics of the GNSS device itself rather than external power grid interference.
Among monitoring equipment, current monitoring probes are used for real-time monitoring of injected current in BCI testing, field strength probes ensure field strength compliance in immunity testing, and current injection probe calibration fixtures ensure injection accuracy.
EMC testing, as a key link in the entire process from design to mass production of automotive GNSS products, its core value is reflected in the dual dimensions of necessity and competitive differentiation. From the perspective of necessity, EMC testing is a "mandatory option" for product compliance, technical reliability, and safety baseline. First, it is a mandatory requirement for regulatory access, requiring compliance with international and domestic standards such as ECE R10, ISO 11452, CISPR 25, and GB/T 45086.1-2024, directly determining whether the product can enter the target market.
Core Value
EMC testing is not only a means to ensure basic product quality but also the core competitiveness for enterprises to build technical advantages and enhance market discourse power. Systematic EMC testing and rectification solutions can significantly improve product robustness in complex electromagnetic environments, forming a differentiated advantage.
From the perspective of competitive differentiation, excellent EMC performance has become a core selling point for automotive GNSS products to stand out in a homogenized market. Against the backdrop of rapid development of intelligent connected vehicles, EMC performance has become an important indicator to measure product technical strength, and its quality directly affects market competitiveness and brand reputation.
Enterprises should establish a dynamic standard tracking mechanism, ensuring sensitivity to regulatory changes by subscribing to updates from international and domestic standards such as ISO, GB, ECE (e.g., ECE R10 Revision 6 amendments, Rev.7's 6GHz immunity requirements). To meet different market demands, it is necessary to simultaneously adapt to multi-regional standards, for example, following GB/T 19392-2013 and GB/T 45086.1-2024 for the domestic market, complying with ECE R10 for the EU market, and meeting FCC Part 15 for the North American market, achieving global market access.
Small and medium-sized enterprises can conduct internal BCI (Bulk Current Injection) preliminary tests (1~400MHz frequency band) and outsource complex tests such as radiated emission to professional laboratories, utilizing their specialized testing capabilities and rectification solutions, reducing testing costs by up to 50%. At the same time, improve efficiency through automated testing technology, achieving automatic testing and report generation, reducing manual intervention and repeated testing.
