Effect of losses on the maximum-to-mean value in a mode-stirred reverberation chamber

Performances of reverberation chambers exhibit a non-trivial dependence on distributed losses. It is shown through numerical simulations that the average maximum-to-mean chamber field/power do not decrease with increasing losses as expected. Rather, it reaches an optimal value at moderate losses. Interestingly, the chamber field uniformity is also optimized at the same amount of losses. This behavior is accompanied by a progressive reduction of the quality factor and of the number of independent stirrer positions, indicating that losses augment the unstirred components as partial field coherence develops. A statistical model, the random coupling model, based on wave-chaos is used to shed light on the role of modal fluctuations and losses in the achievement of an optimal stress. It is found that the optimal condition is reached when losses extend the cavity bandwidth up to the average mode-to-mode spacing. Then, further increasing losses results in a suboptimal condition, for which the open-cavity behavior takes over, i.e., the ratio decreases.