I. Introduction
The reconfigurable over-the-air chamber (ROTAC) is a reverberation chamber whose walls are lined with antennas [1], some of which are excited and the remainder of which are terminated with individually tunable impedances. This design allows the chamber to synthesize the field incident on the device under test (DUT), with prior work confirming that the ROTAC has notable flexibility in the field profiles that can be created. However, this prior work has mostly focused on fixed chamber geometries, and therefore has not considered adequately the relationship between the fidelity of the synthesized field and the number and placement of the ROTAC antennas. This paper connects the antennas to the chamber fields using a rigorous modal analysis and then uses optimization with three different cost functions to design the optimal antenna configuration. The results show that a simple circle packing antenna arrangement provides good performance, and that optimizing to minimize the error between the synthesized and desired field can lead to supergain excitation conditions.