Types of Anechoic Chamber

What is an Anechoic Chamber?

An Anechoic chamber is a specialized room designed to absorb sound or electromagnetic waves, offering a facility free from outside echoes and reverberations. The term “anechoic” is derived from the word “without echoes. DMC ” Anechoic chambers are used in testing and measurement processes for specific devices, including microphones, speakers, antennas, and electronic equipment, to observe their behaviors when placed in a controlled, quiet environment.

Types of Anechoic Chambers

There are two types of anechoic chambers that are used for testing electromagnetic interference (EMI) and electromagnetic compatibility (EMC) are basically: RF Semi anechoic Chambers and Fully Anechoic Chambers.

RF Semi Anechoic Chamber (SAC)

What is an RF Semi Anechoic Chamber?

The RF Semi Anechoic chamber is designed to absorb electromagnetic waves on the walls, ceiling, and sometimes the floor, but not entirely on the floor. Not entirely because the floor often has reflective properties because it is made of conductive material like metal to simulate the ground in a real-world setting. This setup greatly helps in testing how the performance of devices will be when placed on the ground, like in the case of cars or large machinery.

DMC offers Semi Anechoic EMC Chamber at 3 meter, 5 meter and 10 meters of test distance for Full-Compliant EMC Emission and Immunity testing in commercial, automotive, military and education sectors and offers better performance for NSA, SVSWR and FU.

Key Features of RF Semi Anechoic Chambers:

Emission

1. Reflective Floor:

This very important feature reflects any electromagnetic waves in the chamber to simulate a real environment.

2. Absorptive Walls and Ceiling:

The walls and the ceiling absorb electromagnetic waves to enhance no reflection.

3. Controlled Environment:

The chamber provides a controlled setting to measure how devices behave in the presence of electromagnetic waves.

Performance & Compliance

Immunity

Full Compliance Emission per ANSI C63.4 and CISPR-16
Normalised site attenuation deviation (NSA) is better than ±3.5 dB between from 30MHz to 1 GHz sVSWR deviation is better than ±5.5 dB from 1 GHz to 18 GHz.
Full Immunity per IEC/EN 61000-4-3
Field Uniformity deviation is better than 6 dB at 75% of 16 measuring points from 26 MHz/ 80 MHz to 18 GHz

Uses of RF Semi Anechoic Chambers:

Testing large equipment normally operating on or near the ground.
Measuring the electromagnetic emissions from vehicles, appliances, and other heavy machinery.
Conduct EMC tests to check if devices comply with industry standards.

Fully Anechoic Chamber

What is a Fully Anechoic Chamber?

A fully anechoic chamber absorbs electromagnetic waves on all surfaces: floor, walls, and ceiling. Sole exception in the case of a fully anechoic chamber: even the floor is covered with absorptive material. This makes it possible to create a room that will be absolutely free from reflections, and where it will be possible to make very precise measurements of inter-device interaction with electromagnetic waves.

DMC-FAC-3M is a Fully Anechoic Chamber known as FAC Chamber with 3 meter measurement distance. This chamber is similar to a semi-anechoic chamber, except absorbers are placed on the ground plane as well to simulate a free-space environment. It is made up of DMC-PAN series self-standing shielding, ferrite tiles,and Polypropylene based hybrid absorbers on all walls, ceilings and floors.

DMC-FAC-3M can be used for fixed height pre-compliant radiated emissions as per CISPR-16-1-4 and compliant radiated immunity measurements as per IEC 61000-4-3

Features of Fully Anechoic Chambers:

1. Fully Absorptive Surfaces:

All surfaces, from the floor, absorb the electromagnetic waves.

2. No Reflections:

No waves get reflected back from any surface, which leads to proper and very accurate measurements.

3. Isolated Environment:

The chamber is isolated from the external EMFs so that a purely testing environment is available.

Performance & Compliance

Full Compliance Emission per ANSI C63.4 and CISPR-16
Normalized site attenuation deviation (NSA) is better than ±3.5 dB between from 30MHz to 1 GHz sVSWR deviation is better than ±5.5 dB from 1 GHz to 18 GHz.
Full Compliant Immunity per IEC/EN 61000-4-3
Field Uniformity deviation is better than 6 dB at 75% of 16 measuring points from 26 MHz/ 80 MHz to 18 GHz

Applications of Fully Anechoic Chambers:

Testing small electronic devices, antennas, and sensors, where accuracy is demanded to be at its peak.
Measurements that need an absolute reflection-free environment.
The following are the sensitive EMI and EMC tests that are done for devices, all of which have to meet strict regulatory standards.

Key Differences Between RF Semi Anechoic and Fully Anechoic Chambers

1. Floor Reflectivity:

RF Semi-anechoic Chamber: The floor in this chamber is reflective to simulate ground conditions as they occur in the real world.

Fully Anechoic Chamber: The floor is fully absorptive to avoid all types of reflections.

2. Test Environment:

RF Semi Anechoic Chamber: It is used to test large devices or equipment that normally operate near the ground.

Fully Anechoic Chamber: It is typically used in applications where any reflection will bias the measurement result.

3. Application:

RF Semi Anechoic Chamber: For Automotive, Aerospace, and large industrial Equipment Testing.

Fully Anechoic Chamber: Used for in-depth testing of smaller electronic parts, antennas, and other delicate equipment.

Conclusion

Anechoic chambers are essential for testing how devices interact with sound or electromagnetic waves in predefined environments. The difference between an RF semi-anechoic chamber and a fully anechoic chamber depends on the specific testing needs. RF semi-anechoic chambers are best for scenarios that require simulating ground conditions, while fully anechoic chambers are ideal for situations where complete absorption and accuracy are necessary. Understanding these differences helps ensure that devices meet the required standards and perform reliably in real-world conditions.