Suppression of Quantization Lobes in 1-Bit Reconfigurable Intelligent Surfaces

In this letter, we investigate a new way of quantization lobe suppression in 1-bit reconfigurable intelligent surfaces (RISs). Typically, 1-bit RISs are 2-D arrays of passive array elements, where the phase of the reflection from any element can be in one of two states. However, the use of only two reflection phases results in the appearance of the so called quantization lobes in the scattering pattern. A method for the suppression of quantization lobes is described and its performance is studied in detail by numerical simulation and experimental investigation using a 1-bit 5-GHz Wi-Fi band modular RIS. The method is based on dividing a RIS into several equal parts (tiles) and shifting half of them by a small distance of about 1/8 of the wavelength in the normal direction. The results show that by making these minor changes to the aperture shape it is possible to suppress quantization lobes by several decibels without reducing the directivity of the main lobe.