A Reconfigurable Over-the-Air Chamber for Testing Multi-Antenna Wireless Devices

The reconfigurable over-the-air (OTA) chamber (ROTAC) is a reverberation chamber with antennas positioned along the chamber walls. By controlling the signals driving a small number of these antennas and tunable impedances terminating the ports of the remaining antennas, the ROTAC offers dynamical control of the field incident on a mobile device during OTA testing. This article uses finite-difference time-domain electromagnetic simulations and measurements from a ROTAC prototype in combination with a network model to characterize the fields incident on the device as a function of the excitations and terminations. A gradient search optimization is formulated to determine the excitations and terminations required to approximate specified field characteristics in the chamber test zone, including multipath direction of arrival, signal correlation, and fading statistics. The article further explores the relationship between the field spatial sampling within the test zone and the ability to synthesize a field with the specified characteristics.