Elite's New Mode Tuned Chamber
Posted on: February 10th, 2009
Testing in Elite’s large mode tuned chamber is now underway. This new capability is primarily designed for High Intensity Radiated Field (HIRF) testing of commercial aviation and military systems. It is specially suited to test large integrated systems and at frequencies that start as low as 100MHz. Our new chamber is another example of Elite’s commitment to invest in equipment and advanced technology to support the test needs of our customers.
Elite has been an early adopter of mode tuned and mode stirred testing. In 1993, Elite’s whole vehicle EMC chamber came on-line for the purpose of mode stirred radiated immunity testing of trucks, buses, agricultural machines, and construction equipment. Immunity testing in our whole vehicle chamber is performed per the hybrid mode stirring technique described in SAE J551-16.
In 1999, Elite added a reverberation chamber to perform General Motors GM9114 emissions and GM9120 immunity testing. Later with the acquisition of high power pulsed amplifiers, this same room became the primary site for Elite’s HIRF test services. HIRF testing of avionic systems in this room produces fields in excess of 3000V/m.
Since our initial development work with mode stirring over thirty years ago, reverberation chamber testing has achieved greater industry acceptance. In 1999, mode tuned testing was written into MIL-STD-461E and then again in 2004 for RTCA DO-160E. Today, reverberation chambers are being used for other purposes such as FCC emissions testing of high frequency transmitters and for RF emissions testing per the latest “F” revision of DO-160. Other reverb chamber uses include shielding effectiveness testing to evaluate attenuation properties of shielding materials and RF gaskets as well as RF leakage from connectors.
There are several unique characteristics inherent with
reverberation chamber testing, and chamber isotropy and 
homogeneity are two of the key reverb attributes.
Chamber isotropy is that characteristic in which the RF radiated energy propagated within the chamber interacts with the test item from all directions. The isotropic nature of the reverberation chamber means the radiating antenna needs to be positioned in only one orientation (toward the room corner or at the stirrer). This is in contrast to the ALSE radiated immunity test where the antenna is positioned in horizontal and vertical antenna polarity pointed at the product and sometimes at several positions along the test setup.
Field homogeneity refers to the statistically uniform field that is produced within the calibrated chamber test volume as the tuner completes it rotation. In an ALSE, the field is relatively uniform across the antenna beamwidth, but tails off rapidly once beyond the characteristic transmit pattern of the antenna. Reverberation chamber field strengths reach the same levels regardless of where in the calibrated test space they are measured thus ensuring high measurement repeatability and test result reproducibility. Many EMC professionals consider the isotropy and homogeneity of reverb chamber testing to be the key reasons for finding it a more robust RF immunity test when compared to an absorber lined shielded enclosure (ALSE) test.
Elite’s new reverb chamber is comprised of a large main shielded steel room and a smaller antechamber. Both rooms are configured with tuners and are calibrated for HIRF testing. The larger chamber can perform immunity testing starting at 100MHz and extending up to 18GHz. The maximum chamber field strengths for the large chamber are at the levels for DO-160E Categories F and Y. Immunity test levels produced in the antechamber chamber exceed Category “G” levels. The RF susceptibility levels that are likely to be attained for any given product depend upon the RF loading imparted by the device.
Testing in Elite’s mode tuned chamber is arranged first by contacting our sales and application engineers. Our staff will review your test requirements and recommend the most appropriate test chamber and test methodology. For additional information on our reverberation chamber testing, contact Elite at: 1-800-ELITE-11 (800-354-8311)
Testing in the existing mid
sized mode tuned chamber is
capable of Category “G”
levels starting at 400MHz.
Mode stirred testing in Elite’s
whole vehicle EMC chamber.
