Projection-OTA, Over-the-Air Testing by Reconfigurable Reflecting Structures

The bottleneck in OTA testing electrically large equipment is the large number of sources required for sufficient angular density. That is, if the sources are active. In that case, high-bandwidth, high-frequency equipment with excellent stability, processing power, and configurability is needed per antenna element. The costs of scaling up the current MIMO OTA configuration to higher frequencies and/or large equipment is prohibitive. In case passive radiators are used, the maximum control speed is determined by the maximum expected Doppler frequency. Such performance is order of magnitudes cheaper, even for large numbers of elements. In this contribution, we will present a new OTA concept that uses passively radiating reconfigurable structures and is inherently bi-directional. The concept that we call Projection-OTA, accommodates test objects in FR1 that are electrically large to very large and shows good prospects for emulating beam dynamics for testing 5G NR in FR2. Whether such passive structures will be made up by reflect arrays, meta-surfaces, or even intelligent surfaces is to be determined. We will discuss the prospects and limitations of this concept.