A Programmable Complex Impedance IC for Scalable and Reconfigurable Meta-Atoms

This article presents the design of a fully-custom integrated circuit (IC) suitable for adjusting the complex impedance of individual meta-atoms to enable programmability of metasurface systems. Implemented in a 0.18 μm mixed-signal CMOS process, the circuit utilizes four integrated complex impedance elements, each one with 2 ¹⁶ available states. The impedance elements are optimized between 2–6 GHz, thus covering the entire S-band as well as half of the C-band. An asynchronous digital control circuit based on Quasi Delay Insensitive (QDI) circuits has been employed, offering basic communication capabilities and software programmability, but most importantly, the clockless operation allows for extreme scalability, ultra-low static power consumption and low electromagnetic (EM) radiated emissions. An array of meta-atoms utilizing the ICs can form metasurfaces with arbitrary sizes and shapes, on both rigid and flexible substrates, adjusting their surface impedance without interfering with incoming EM waves. Measurement results of the 2.2 mm × 2.2 mm IC demonstrate that it achieves a reconfiguration frequency of 1 MHz for all loading elements, whilst consuming 324 μW static power consumption.