The realization of a programmable metasurface, enabled by a custom application-specific integrated circuit (ASIC), is presented in this paper. The ASIC is used to provide an adaptive complex impedance load to each of the metasurface unit cells. Various technology nodes are analyzed for the implementation of tunable complex impedance loading elements before one is selected for the final implementation, in which four complex loads are placed within each integrated circuit, and each load is controlled by two digital-toanalog converters. Furthermore, the ASICs populate the back of the metasurface to form a mesh network to enable programmability. The paper includes practical limitations that affect the realization, as well as an example adaptive metasurface absorber that builds upon the practical tuning range of the ASIC. Perfect absorption for both transverse electric and transverse magnetic polarization is demonstrated. INDEX TERMS Metasurfaces, ASIC, programmable RF load, perfect absorption, reconfigurable.

Metamaterials and metasurfaces have given possibilities for manipulating electromagnetic (EM) waves that in the past would have seemed impossible. The majority of metasurface designs are suitable for a particular frequency and angle of incidence. One long-sought objective is the design of programmable metasurfaces to dynamically manipulate a variety of incoming EM frequencies and angles. In order to do this, a large-scale mesh of networked chips are required below the metasurface, which apart from adapting electrical impedance properties, also communicate with each other, thus relaying information about meta-atom settings, as well as forwarding possible distributed measurements taken. This paper describes why an asynchronous mixed-signal ASIC is advantageous for the control of scalable, EM absorbing, metasurfaces.