In today’s rapidly advancing technological landscape, electronic devices and systems are becoming increasingly complex and interconnected. As a result, the electromagnetic compatibility (EMC) of these systems has become a critical concern. EMC ensures that electronic devices can function properly in their intended electromagnetic environment without causing or being affected by electromagnetic interference (EMI). One of the key aspects of achieving EMC is the effective shielding of electronic components, particularly cables and connectors, to prevent the ingress and egress of unwanted electromagnetic signals.

To evaluate the shielding effectiveness of various structures, a standardized and reliable measurement method is essential. This is where the triaxial method comes into play, offering a comprehensive and efficient approach to testing shielding performance. The triaxial method, also known as the three-coaxial method, is a widely recognized technique for measuring shielding attenuation, transfer impedance, and coupling attenuation. It is based on a series of international standards, including IEC 62153-4-X, which provide guidelines for conducting accurate and consistent tests.

Advantages of the Triaxial Method

The triaxial method boasts several advantages that make it a preferred choice for shielding effectiveness testing:

Enclosed Setup

The test setup is enclosed, which effectively isolates the test environment from external electromagnetic interference. This ensures that the measurements obtained are solely due to the shielding properties of the test specimen, rather than being influenced by external factors. The enclosed nature of the setup also prevents any electromagnetic radiation from escaping, making it a safe and environmentally friendly testing method.

Wide Dynamic Range

The triaxial method offers an impressive dynamic range, capable of measuring shielding effectiveness up to 125 dB. This wide range allows for the accurate assessment of both highly effective and less effective shielding structures, providing valuable insights into their performance under various conditions.

High Repeatability

The method is known for its high repeatability, ensuring that consistent results can be obtained across multiple tests. This repeatability is crucial for validating the performance of shielding materials and designs, as it allows for reliable comparisons and the identification of any variations or anomalies.

Simplicity and Efficiency

The testing apparatus used in the triaxial method is relatively simple, consisting of a triaxial test fixture, a network analyzer, and a computer with appropriate software. This simplicity not only makes the setup and operation of the test more manageable but also reduces the potential for errors and uncertainties in the measurement process. Additionally, the preparation of the test specimen is straightforward, allowing for quick and easy testing of various components.

Comprehensive Testing

One of the most significant benefits of the triaxial method is its ability to simultaneously measure multiple shielding parameters. In a single test, it can determine the transfer impedance (ZT), shielding attenuation (aS), and coupling attenuation (aC) of the test specimen. This comprehensive testing capability provides a holistic understanding of the shielding performance, enabling engineers to identify specific areas for improvement and optimize their designs accordingly.

Typical Test Environment

A typical test environment for the triaxial method includes the following components:

• Triaxial Test Fixture: This fixture is designed to securely install and hold the test specimen in place. It ensures proper alignment and positioning, facilitating accurate measurements.
• Network Analyzer: The network analyzer is used to extract the S-parameters from the test setup. These parameters are essential for characterizing the electromagnetic behavior of the test specimen.
• Computer with Software: The computer is equipped with specialized software that processes the S-parameters obtained from the network analyzer. The software evaluates and converts the data into meaningful shielding effectiveness metrics, such as shielding attenuation, transfer impedance, and coupling attenuation curves.

Testing Principle

The triaxial method employs a coupling test tube, which is a closed cylindrical structure. The left end of the test specimen is short-circuited to the tube, while the right end is connected to the test head and the network analyzer. When a signal leaks from the test specimen, it propagates in both directions. The portion that travels to the left encounters the short circuit and reflects back towards the right. The combined signal is then transmitted through the test head to the network analyzer. The control software extracts the S-parameters from the network analyzer and calculates the shielding effectiveness parameters.

Control and Evaluation Software

The control and evaluation software is an integral part of the triaxial method, serving as a comprehensive tool for managing all aspects of the testing process. Based on the IEC 62153 series of standards, the software is continuously updated to ensure compliance with the latest testing guidelines. It offers various functionalities, such as controlling the network analyzer, storing test parameters, printing test reports on installed printers, marking features, displaying test results in logarithmic or linear formats, and exporting measurement data to Excel for further analysis.

Test Examples

The triaxial method has been successfully applied to a wide range of test specimens, including:

• RF Cables: Assessing the shielding effectiveness of radio frequency cables is crucial for maintaining signal integrity and preventing interference in communication systems.
• New Energy Cables: With the growing adoption of renewable energy sources, the shielding performance of cables used in solar, wind, and other new energy applications must be thoroughly evaluated to ensure reliable power transmission.
• Ethernet Cables, USB Cables, and Differential Lines: These cables are extensively used in data communication and computer networking. Their shielding effectiveness directly impacts the speed, reliability, and security of data transmission.
• TV Cables and Modules: The shielding performance of television cables and associated modules is vital for delivering high-quality audio and video signals, free from interference and noise.

In conclusion, the triaxial method has revolutionized shielding effectiveness testing by providing a reliable, efficient, and comprehensive approach. Its numerous advantages, such as the enclosed setup, wide dynamic range, high repeatability, simplicity, and the ability to measure multiple shielding parameters simultaneously, make it an indispensable tool for engineers and researchers in the field of electromagnetic compatibility. As electronic systems continue to evolve and become more complex, the triaxial method will undoubtedly play a crucial role in ensuring their proper functioning and compatibility in the electromagnetic environment.

The Shield Effect Measurement kit provided by Vinstronics uses the triaxial measurement technology. With this triaxial shielding measurement, engineers can accurately measure the shielding performance of cables and connectors caused by coupling impedance and shielding attenuation. If you have any needs, please contact us.