Reverb Testing Services

Testing in a Reverberation Chamber

What is a Reverberation Testing Chamber?      Reverberation Chamber Testing

A reverberation chamber, sometimes known as a mode tuned/mode stirred chamber, is a shielded enclosure or resonant cavity for RF testing. This chamber is statistically isotropic, random polarity, having RF uniformity within specified limits. Typically a reverberation chamber has a paddle (or tuner) which stirs the field, randomizing the boundary conditions.  

There are two types of Reverberation Testing methods. “Mode tuned” refers to when the paddle is stepped to a position and then RF is applied for a dwell time sufficient to exercise the equipment. At NTS, the tuner can be driven by a computer-controlled stepper motor that also drives RF generation and monitoring equipment.

The second type, “Mode stirred”, is when the paddle is continually turned with RF energy applied for a full paddle revolution. Paddle speed is varied to meet the specific requirements of the device under test.

In both methods, a single, full turn of the paddle applies RF energy to all sides of the device in one pass. This greatly simplifies the process compared to direct illumination testing.

What are the benefits to Reverberation Testing?

The benefits to reverberation testing are numerous. RF is applied to all exposed sides of the device under test (DUT) during a full 360° turn of the paddle, instead of a single side. For direct illumination testing, many standards require that all apertures of the DUT be illuminated.  On complex items this can be difficult – even impossible.  Window effects testing, required when applying direct illumination, is not required during reverb testing because the field intensities are constantly changing.    Test repeatability is much easier to obtain in a reverb chamber with proper processes, and running the test is much less complex than a single aspect angle test.  Antenna distance, aim (focus), 3 dB beam width, location of the field probe, EUT layout, and location of the EUT in the working volume are all less of a factor in the repeatability of test.

When is a Reverberation Chamber used?

Reverb chambers are useful for radiated susceptibility, radiated emissions (total radiated power), shielding effectiveness, and many other troubleshooting scenarios for equipment utilized in the Aerospace, Defense and Automotive sectors. The reverb test method is called out as the preferred method in SAE ARP 5583 which states that reverb method testing is the recommended and preferred method to show compliance for large and/or complex Level A (flight critical) systems.

The FAA, AEROCAE, RTCA, and major airframe manufacturers (i.e., Boeing, Airbus, etc..) are "preferring" reverb over anechoic chamber due to the time and cost savings, as well as the robustness of the reverb test method over the direct illumination technique.

You should know if reverberation testing is right for your program.  Reverb chambers are random in polarity, which makes it challenging in determining directivity of RF energy.  Testing multiple field levels on a system, such as outside the pressure vessel level and inside the pressure vessel level, can be difficult; all equipment in the chamber is exposed to the same field.  There are limitations on pulse width due to a high Q (efficient) chamber having large amount of stored energy.  If you have small, simple equipment, single aspect angle tests may be faster and sufficient for test coverage.  There are ways to compensate for each, and an NTS engineer can help with suggestions or assist you with a test plan.

Both direct illumination and reverberation test methods are acceptable paths to certification.  They both have benefits and drawbacks that champion each as a test method.  Fortunately, NTS has the ability to test in both methods and the engineering expertise to support your path to certification.

 

Reverberation Testing at NTS

NTS has seven Reverberation Testing chambers in five of our laboratories – in California, Arizona, Illinois, Texas, and Massachusetts. These state-of-the-art chambers and amplifiers achieve greater than DO-160 Category L levels.

NTS Rockford

NTS Rockford was our first facility to add reverberation chamber testing capabilities. Currently this laboratory has two reverberation chambers, coupled with state-of-the-art amplifiers. Their newest chamber achieves greater than DO-160 Category L levels from 100 MHz to 18 GHz. Test frequencies as high as 40 GHz are possible.

This 12’ × 20’ × 10’ chamber has a test volume of over 438 cubic feet or 12.42 cubic meters and a 4’ × 7’ door. The chamber and its adjacent 10’ × 10’ ground plane are configured for convenience and efficiency. Customer support equipment is staged on the ground plane, and the chamber’s computer-controlled horizontal stir assembly is mounted unobtrusively high on the rear wall. Both the chamber and ground plane are equipped with filtered AC and DC power: 28 VDC, 480 VAC and 120/208 VAC at 60 Hz, and 115 VAC at 400 Hz. Nonstandard power is also available upon request.

This chamber’s extremely large usable test volume (over 438 cubic feet) allows for testing multiple-LRU systems. It has field densities capable of achieving peak fields up to 15,000 V/m. Like other NTS Rockford EMI chambers, this reverberation chamber is drive stand-adaptable and can be mated to a motor drive for rotating equipment. An efficient chamber layout coupled with test methodology ensures lean test execution.

NTS Fullerton

NTS Fullerton is currently equipped with a copper lined reverberation chamber coupled with state-of-the-art amplifiers. This chamber achieves greater than DO-160 Category L levels from 100 MHz to 18 GHz. Test frequencies as high as 40 GHz are possible.

This reverberation chamber has interior shield dimensions of 21.4’ x 16.5’x 11.8’ (6.5m x 5.m x 3.5m) and an automated 10’ × 10’ sliding door. The chamber is also equipped with a large customer support equipment staging area along its outer wall with both feed through panels and sub terrain cable raceways for ease of test setup. The chamber’s computer-controlled Vertical stir assembly is mounted unobtrusively in the rear corner of the chamber allowing for a usable uniform field volume of approximately 15 x 8 x 8.

Both the chamber and ground plane are equipped with filtered AC and DC power: 28 VDC, 480 VAC and 115/208 VAC at 60 Hz, and 115/208 VAC at 400 Hz. Nonstandard power is also available upon request.

NTS Boxborough

NTS Boxborough is currently equipped with a copper lined reverberation chamber coupled with state-of-the-art amplifiers. This chamber achieves greater than DO-160 Category L levels from 100 MHz to 18 GHz. Test frequencies as high as 40 GHz are possible.

This reverberation chamber has interior shield dimensions of 21.4’ x 16.5’x 11.8’ (6.5m x 5.m x 3.5m) and an automated 10’ × 10’ sliding door. The chamber is also equipped with a large customer support equipment staging area along its outer wall with large feed through panels for ease of test setup. The chamber’s computer-controlled Vertical stir assembly is mounted unobtrusively in the rear corner of the chamber allowing for a usable uniform field volume of approximately 15 x 8 x 8.

Both the chamber and ground plane are equipped with filtered AC and DC power: 28 VDC, 480 VAC and 120/208 VAC at 60 Hz, and 115 VAC at 400 Hz. Nonstandard power is also available upon request.

NTS Plano

NTS Plano is currently equipped with a copper lined reverberation chamber coupled with state-of-the-art amplifiers. This chamber achieves greater than DO-160 Category L levels from 100 MHz to 18 GHz. Test frequencies as high as 40 GHz are possible.

This reverberation chamber has interior shield dimensions of 21.4’ x 16.5’x 11.8’ (6.5m x 5.m x 3.5m) and an automated 10’ × 10’ sliding door. The chamber is also equipped with a large customer support equipment staging area along its outer wall with both feed through panels and sub terrain cable raceways for ease of test setup. The chamber’s computer-controlled Vertical stir assembly is mounted unobtrusively in the rear corner of the chamber allowing for a usable uniform field volume of approximately 15 x 8 x 8.

Both the chamber and ground plane are equipped with filtered AC and DC power: 28 VDC, 480 VAC and 120/208 VAC at 60 Hz, and 115 VAC at 400 Hz. Nonstandard power is also available upon request.

NTS Tempe

NTS Tempe is currently equipped with a custom copper lined reverberation chamber. This chamber achieves greater than DO-160 levels from 200 MHz to 18 GHz. Test frequencies as high as 40 GHz are possible.

This reverberation chamber has interior shield dimensions of 15.8’ x 11.8’ x 10’ (4.83m x 3.61.m x 3.05m). The chamber is also equipped with a large customer support equipment staging area along its outer wall with both feed through panels. The chamber’s computer-controlled Vertical stir assembly is mounted unobtrusively in the rear corner of the chamber allowing for a usable uniform field volume of approximately 14 x 8 x 8.

Both the chamber and ground plane are equipped with filtered AC and DC power:  Nonstandard power is also available upon request.

Download the NTS Guide to Reverberation Testing for more details.