IEEE 299: Standard for Measuring Shielding Effectiveness

IEEE 299: The standard for measuring shielding effectiveness

In the field of electromagnetic shielding, ensuring adequate protection against interference is essential for the proper functioning of electronic devices.

For this reason, the IEEE 299 standard provides detailed guidelines on methods for measuring the shielding effectiveness of shielded environments, defining standardized procedures for evaluating electromagnetic wave attenuation.

What is the IEEE 299 Standard?

The IEEE 299 standard, titled Standard Method for Measuring the Effectiveness of Electromagnetic Shielding Enclosures, establishes procedures for determining the attenuation level of electromagnetic shielding across a wide range of frequencies. This standard is used to test the performance of shielded rooms, MRI suites, EMC test environments, and other applications.

What frequencies does it cover?

The standard defines tests to measure shielding effectiveness over a frequency range from 9 kHz to 18 GHz, with possible extensions from 5 Hz up to 100 GHz. The tests are divided into three main frequency ranges:

Low frequency (magnetic): 9 kHz – 16 kHz, 140 kHz – 160 kHz, 14 MHz – 16 MHz
Resonance range: 20 MHz – 100 MHz (biconical), 100 MHz – 300 MHz (dipole)
High frequency (plane wave): 0.3 GHz – 18 GHz (horn antenna)

Why is shielding effectiveness measurement important?

The shielding effectiveness of an environment is a crucial parameter for preventing electromagnetic interference (EMI) that could compromise the operation of equipment.

Medical sector (MRI): ineffective shielding of MRI rooms can cause artifacts in diagnostic images due to interference from external radio frequencies.
EMC test laboratories: a well-shielded environment is essential for ensuring accurate and repeatable measurements without external disturbances.
Aerospace and military industry: shielded enclosures are fundamental for protecting sensitive communications and electronic equipment from EMI.

How is shielding effectiveness measured?

To conduct a test in compliance with the IEEE 299 standard, the following key steps must be followed:

Definition of test conditions: before starting, the frequency ranges for measurement are established (typically from 9 kHz to 18 GHz, with extensions up to 100 GHz in some cases). The measurement points are defined, such as walls, doors, windows, joints, or other critical shielding points. Transmitting and receiving antennas are positioned according to IEEE 299 specifications.
Signal generation: an RF signal generator is used to emit an electromagnetic wave at a specific frequency and power level. The signal is transmitted inside or outside the shielded enclosure to evaluate attenuation.
Signal measurement: an RF receiver or spectrum analyzer measures the signal level after passing through the shielding. The difference between the initial and received signal determines the attenuation value in dB.
Results analysis: effective shielding must achieve attenuation levels of at least 100 dB for frequencies up to 10 MHz, 80 dB between 10 MHz and 1 GHz, and 60 dB above 1 GHz.

To ensure accurate measurements in compliance with international standards, various professional instruments are used, including:

RF signal generators (es. Rohde & Schwarz e Keysight)
RF power amplifiers
Test receivers and spectrum analyzers
Calibrated antennas (biconical, log-periodic, and horn)
Portable measuring instruments, such as the SEMS B, for fast and reliable field tests

The role of SEMS B in shielding tests

The SEMS B is an advanced instrument designed for measuring shielding effectiveness in compliance with the IEEE 299 standard. Unlike traditional systems, the SEMS B offers:

✔ Rapid and automated measurements, reducing human error.

✔ Portability and ease of use, with no need for connection cables between TX and RX.

✔ High precision, with a dynamic range up to 120 dB and an accuracy of ±1 dB.

✔ Compatibility with frequencies from 10 kHz to 300 MHz, covering a wide range of applications.

Thanks to these features, the SEMS B represents the ideal solution for laboratories, industries, and hospitals requiring reliable testing that complies with international regulations.