On the Measurement of the Absorption Cross Section and Material Reflectivity in a Reverberation Chamber

Abstract

—In this paper, all losses in a reverberation chamber (RC) are\ud represented by equivalent absorption cross sections (ACSs), both those due\ud to the power dissipated and those due to the power lost through leakage.\ud This representation enables us to define an absorption cross section of\ud the RC, so that we can easily measure and compare the losses of different\ud natures in an RC directly in terms of ACS. Additionally, this representation\ud of the losses leads to equal measurements of the attendant ACS in relation\ud to two different methods to represent the electromagnetic radiation in an\ud RC suggested by Corona and Hill. As a specific applicative example, an\ud effective method to measure the reflectivity of materials based only on ACS\ud measurements is shown. Finally, its validity will be presented, applying the\ud same principle of the reflectivity measurement to a nested reverberation\ud chamber system

Absorbing Cross Section in Reverberation Chamber: Experimental and Numerical Results

“…Indirect estimation of ACS passes through insertion loss measurements [33] (with and without the material sample) by the well-known definition…”

Performance of the Reflectivity Measurement in a Reverberation Chamber

“…The reflectivity (R) is achieved by the combination of three measurements of IL [15], then three ACS measurements are obtained: the ACS of the empty chamber and the ACSs of the absorbing surface with sample and with no sample under test [21,22]. We specify that normally a measurement of ACS requires the corrections for radiation and total efficiency, whereas the measurement of reflectivity does not require such corrections, as it is achieved by uniform ratios [22].…”

“…The mathematical model of the measurement method, which is shown here using simplified symbols with respect to those used in [15], can be written as follows [15,22]:…”

“…Various applications have already been available [1], and others are being studied. In particular, applications for radiate power measurements are shown in [3]; applications for shielding effectiveness measurements are shown in [4][5][6][7][8][9][10][11][12][13]; applications for absorption measurements are shown in [14][15][16][17][18][19]; applications for radiation efficiency measurements of antennas are shown in [20][21][22]; studies for the testing of wireless devices by emulations of a Rician radio environment are shown in [23][24][25][26]. The reflectivity measurement of materials is certainly an innovative application of an RC.…”

“…The absorbing surface method for the reflectivity measurements in an RC was developed in [15], and some initial results on the metallic mesh grid and fabric and nonwoven fabric are shown in [27,28]. This method uses a high-quality microwave absorber to create an equivalent free space between a plane sample of the material under test and the surface of the absorber, so that the reflected energy by the sample is separated from the one transmitted through it; the ratio between the former and the incident one, which represents the reflectivity coefficient of the sample under test, can be estimated by a simple measurement procedure [15]. However, no analysis of the performance of the measurement method in terms of measurement uncertainty and relevant noise level (NL) has been systematically done so far.…”