RIS with Continuous Amplitude and Phase Control: Functional Testing Method and Implementation

We present the methodology and supporting waveguide components for the rapid functional testing of a reconfigurable intelligent surface (RIS) prototype operating at 28 GHz. The tested RIS features a 16 by 16 element array with independent continuous (16-bit) control over the amplitude and phase of its complex reflection coefficients. Over-the-air (OTA) functional testing is conducted using a custom-designed dual-polarized open-ended waveguide (OEWG) probe with a square cross-section and an orthomode transducer (OMT), both fabricated using 3D printing technology.