On the Power Dissipated by an Antenna in Transmit Mode or in Receive Mode in a Reverberation Chamber

One of the main characteristics of a reverberation chamber is its quality factor since it determines the field enhancement and the decay time of the impulse response. If a receiving antenna is placed in the room, it absorbs part of the energy which leads to a decrease of the intrinsic quality factor of the room. Such a well-known phenomenon is quantified by the quality factor of the receiving antenna, and a simple analytical formula is available in the literature. If the antenna placed in the chamber is a transmitting antenna, it also receives the waves reflected by the chamber walls and it is often supposed that its quality factor is still given by the same formula. However, it has been already outlined that the quality factor of an antenna used either in a transmitting mode or in a receiving mode is not identical, but differ by a factor of two. The objective of this contribution is to propose an analytical approach, based on the statistical properties of scattering matrices, to justify this result. Furthermore, experiments have been carried out both in the frequency domain and in the time domain to clearly point out the increase of the power dissipated in a transmit-mode antenna. Polarization effects are also studied.