 particular, this procedure is simpler when measuring many active terminals. It should be noted that this simpli- fied method only works if the chamber is loaded SO much that the reference antenna and AUT do not represent any significant contribution to the mode bandwidth If of the chamber. If this is not the case, the results of the measurements may be wrong because the chamber transfer function will not have a linear dependence on erad of the reference antenna and the AUT. This may in particular happen if the reference antenna or the AUT is made of materials that absorb radiation and thereby increase the mode bandwidth even when the antenna ports are open or short-circuited. If we remove the free space mismatch efficiencies from Equation (12.5), we get an average chamber transfer function that varies more slowly with frequency. This can then be frequency stirred for better accuracy without losing resolution due to variations in the mismatch efficiency. The free space input reflection coefficients of the two antennas can be obtained by complex averaging of the S11 and S22, as given by Equation (12.2), and the mismatch-corrected chamber transfer function is defined by G chamber (12.8) where N is the number of stirrer positions and IS21 is given by Equation (12.5). 12.2.3 Accuracy and Number of Independent Samples In order to perform accurate measurements in the reverberation chamber, we need the chamber transfer function (12.5) to be proportional to the radiation efficiency independently of which antenna or terminal we measure. This is possible only if the mode stirring creates enough independent samples. The S21 samples are, for sufficient independent samples, complex normally distributed. Then the relative accuracy by which we can estimate G chamber has a standard deviation of [21] (12.9) where Nind is the number of independent samples. This means that we need Nind = 100 for an accuracy of +10% (i.e., + 0.5 dB). The number of independent samples is determined primarily by the mode density in the chamber (i.e., 