Transmission-Type 2-Bit Programmable Metasurface for Single-Sensor and Single-Frequency Microwave Imaging

TLDR

Programmable digital metamaterials offer powerful opportunities for real‑time electromagnetic device design. This work introduces the first transmission‑type 2‑bit programmable coding metasurface enabling single‑sensor, single‑frequency microwave imaging. By employing a two‑layer binary coding unit whose row and column voltages simultaneously switch diodes, the metasurface generates random transmission patterns that replace independent spatial modulators, reducing system complexity and cost while avoiding object dispersion under a single frequency. Experimental measurements at microwave frequencies confirm that the proposed metasurface achieves effective single‑sensor, single‑frequency imaging.

Abstract

Abstract The programmable and digital metamaterials or metasurfaces presented recently have huge potentials in designing real-time-controlled electromagnetic devices. Here, we propose the first transmission-type 2-bit programmable coding metasurface for single-sensor and single- frequency imaging in the microwave frequency. Compared with the existing single-sensor imagers composed of active spatial modulators with their units controlled independently, we introduce randomly programmable metasurface to transform the masks of modulators, in which their rows and columns are controlled simultaneously so that the complexity and cost of the imaging system can be reduced drastically. Different from the single-sensor approach using the frequency agility, the proposed imaging system makes use of variable modulators under single frequency, which can avoid the object dispersion. In order to realize the transmission-type 2-bit programmable metasurface, we propose a two-layer binary coding unit, which is convenient for changing the voltages in rows and columns to switch the diodes in the top and bottom layers, respectively. In our imaging measurements, we generate the random codes by computer to achieve different transmission patterns, which can support enough multiple modes to solve the inverse-scattering problem in the single-sensor imaging. Simple experimental results are presented in the microwave frequency, validating our new single-sensor and single-frequency imaging system.