What are Anechoic Chambers used for?

From Radiated Emissions to Immunity: Testing in an Anechoic Environment

Radiated Emissions (EMI)

To measure radiated emissions, the Device Under Test (DUT) is placed on a turntable within the anechoic chamber. Antennas, positioned at a specific distance from the DUT, are used to detect electromagnetic radiation emitted by the device. The turntable rotates, and the antenna height is varied to capture emissions in all directions and polarizations. A spectrum analyzer or receiver measures the intensity of the emissions across a range of frequencies. The anechoic chamber's absorbing materials minimize reflections, ensuring that the measured emissions are primarily from the DUT. The measured emissions are then compared to regulatory limits to ensure compliance.

Radiated Immunity (RI)

For radiated immunity testing, the DUT is placed within the anechoic chamber. Antennas generate electromagnetic fields of varying frequencies and intensities, simulating real-world electromagnetic disturbances. The DUT is exposed to these fields, and its performance is monitored for any malfunctions or disruptions. The anechoic chamber prevents external electromagnetic interference from affecting the test and minimizes reflections of the generated fields. The test is performed to see if the device continues to operate as intended while being exposed to the radiation.

Magnetic Field Emissions

To measure magnetic field emissions, the DUT is placed within the anechoic chamber. Magnetic field probes (loop antennas) are used to measure the strength of the magnetic fields emitted by the DUT. Measurements are taken at various locations and orientations around the DUT. The shielding properties of the anechoic chamber are very important to reduce ambient magnetic fields, so that only the DUT's magnetic fields are being measured. The measured magnetic field emissions are then compared to regulatory limits.

Magnetic Field Immunity

For magnetic field immunity testing, the DUT is placed within the anechoic chamber. Helmholtz coils or other magnetic field generation equipment are used to create controlled magnetic fields around the DUT. The DUT's performance is monitored while it is exposed to these magnetic fields. The shielding properties of the anechoic chamber are very important to reduce ambient magnetic fields, so that only the generated magnetic fields are affecting the DUT.

Measurement of the result of ESD

Although the primary ESD test is the application of the discharge, the secondary result of the discharge is a rapid, broadband electromagnetic pulse. After an ESD event is applied to the DUT, this pulse can be measured. Antennas and receivers can be used to measure the broadband electromagnetic pulse that is created from the ESD event. The anechoic chamber allows for a controlled environment for these measurements. The shielding of the anechoic chamber will reduce outside interference, allowing for more accurate measurements.