Improving the Performances of a Reverberation Chamber: a Real Case

In a previous measurement campaign it was found that the reverberation chamber (RC) of CISAM EMC Department evidenced anomalous values of the quality factor (Q) - too low to be "right" for a fully aluminum chamber - and moreover, after some use it became absolutely evident that it was too easy to improve - lowering it, of course - the value of the lowest usable frequency (LUF) of this chamber. After some investigations on the chamber materials/components and on the assembly procedures, the authors developed the idea that this strange behavior had to be attributed to the tuners - being the original ones made with somehow absorbing material - and therefore they decided to replace them with new, all metal tuners. In this paper, the results of a calibration campaign on the reverberation chamber after tuner replacement are presented, as well as the results of an emission test on a standard reference source before and after the replacement. The calibration has been done in the frequency range 80 MHz divide 3 GHz, and the emission tests have been performed in the range 100 MHz to 1 GHz, which is exactly the frequency range of the reference radiator used to generate a standard spectrum. The comparison between the results obtained, under the same conditions, with the old and with the new tuners is presented, and the goodness of the assumptions demonstrated: with the new tuners the performances of the chamber have been considerably improved.