Compact 3-D Active Frequency Selective Surface with Wideband Tunability for IoT Backscatter Communication

The rapidly increasing demand for compact, low-power electromagnetic components in Internet of Things (IoT) terminals has exposed the limitations of conventional active frequency selective surfaces (AFSSs), such as large physical dimensions, high power consumption, and mechanical complexity. To overcome these challenges, this communication proposes an innovative compact 3-D AFSS design featuring helically arranged metallic strips on prismatic units. This configuration generates an upward-spiraling surface current path, substantially enhancing electromagnetic coupling and inductance while achieving miniaturization. The proposed structure represents a significant advancement in electronically tunable 3-D AFSS, offering both extreme compactness and exceptionally wide continuous tunability. The fabricated prototype demonstrates an ultracompact unit size of only 3.5\times 7$ mm, a remarkable 95% fractional tuning range (920 MHz-2.58 GHz), and ultralow-power consumption of maximum 14.4~\mu $ W under 0-30-V bias. These features make the proposed AFSS a highly promising solution for low-power, highly integrated, and miniaturized wireless communication nodes in future IoT backscatter systems.