Gradient ascent based optimization for a reconfigurable OTA chamber

A reconfigurable over-the-air chamber represents a reverberation chamber whose walls are lined with antennas that are terminated in reconfigurable impedances, allowing synthesis of a wide range of channel conditions for over-the-air testing of mobile wireless devices. While these chambers have potential for practical device testing, finding the right impedances to achieve the desired channel characteristics remains a challenging problem. This work explores the use of a simple gradient ascent optimization algorithm to determine the impedance states that achieve a specified spatial structure in the multipath, as characterized by the multipath power angular spectrum. The results highlight that the optimization is effective for synthesizing a desired power angular spectrum with a directive peak and a relatively low sidelobe level.