ADM is constructed from Analysis of feature data which is the high-frequency part or the fast variations gives the Feature Difference Measure (FDM) The ADM and FDM are combined to give the Global Difference Measure (GDM) The FSV score for ADM, FDM and GDM is divided in to a 6 point scale as: Less than 0.1 Excellent 0.1-0.2 Very good 0.2-0.4 Good 0.4-0.8 Fair 0.8-1.6 Poor Greater than 1.6 Very poor The shielding theory From the shielding theory of materials with apertures, we can obtain the shielding effectiveness (SE) using the equation: Where Shielding effectiveness of an aperture is a function of its size, shape and number of apertures.
The worst case shielding effectiveness of the slot antenna provides a simple model for calculating the worst case shielding effectiveness of an aperture. The value of constant (K) is (20) for a slot or (40) for a round hole. Shielding effectiveness of a single aperture with the largest dimension of the opening length (L) is given by: Where For more than one aperture, the shielding effectiveness must be subtracted by 20log10 of the total number of apertures within a half wavelength. Therefore the equation for shielding effectiveness becomes: Where Shielding effectiveness (SE) measurements in a mode stirred reverberation chamber A radiated shielding effectiveness testing was performed in a modified reverberation chamber.
The chamber is generally metallic with highly reflective walls which together with a mode stirring paddle to produce statistically uniform internal electromagnetic fields. The mode stirred reverberation chamber is a room with a transmitting antenna and the receiving antenna is placed in another room. The test sample is mounted on the shielding wall to separate the two antennas. To evaluate the performance of the mode stirring system, you can test the shielding effectiveness with and without the stirrer running. Discussion and analysis of results To obtain proper test results, we used the test samples including different lids and the following data was obtained.
In each results we shall develop charts and use data from them to calculate for mean, variance and grade. 1. Testing With round holes which were open(without lid) Table 1: Summary of the results ADM 0.78278 Fair FDM 0.7404 Fair GDM 1.1803 Poor Fig 1.1: graph of ADM Fig 1.2: graph of FDM Fig 1.3: graph of, GDM Fig 1.4: histogram of GDMc Mean=0.26 Table 1.2 ADM FDM GDM Grade 3.2 3.0 4.7 spread 3.2 3.0 4.7 The GDM is a summary and from the results it shows that the resonant portion of the antennae stirring is occurring poorly.
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