Scattered-Field Testing of Reconfigurable Intelligent Surfaces in a Bistatic Measurement System for Far-to-Far and Far-to-Near Scenarios

Reconfigurable intelligent surface (RIS) aided wireless communication systems have emerged as a key technology in B5G/6G networks. In these scenarios, the signals from the base transceiver station, usually located far from the RIS, impinges on the RIS as a local plane wave, and are then redirected by the RIS in various directions, shaping the field strength distributions over both near- and far-field regions. Therefore, establishing a reliable testing environment is essential to improve and verify the RIS. This paper presents a novel configuration that combines a compact antenna test range (CATR) with a planar near field scanner (PNFS) to form a bistatic measurement system to evaluate the scattering characteristics of the RIS. The analyses of the field distributions in both far-to-far and far-to-near scenarios obtained from the bistatic measurement system, along with near-field holographic imaging, may provide valuable measured data for predicting communication link budgets and optimizing RIS performance.