SPARTACUS: Self-Powered Augmented RFID Tag for Autonomous Computing and Ubiquitous Sensing In recent years, besides the advances made in canonical UHF radio-frequency identification (RFID) technology, intense research efforts are being made to design new passive augmented tags that enableRFID-based sensing. These efforts stimulate continued research aimed at providing tags with additional functionalities, besides identification and sensing. In this work, an innovative device, representing a new class of fully passive augmented UHF RFID tags, is presented. It is named SPARTACUS, an acronym for self-powered augmented RFID tag for autonomous computing and ubiquitous sensing. The device, based on an accurate electromagnetic design that exploits polarization diversity of two antennas, which perform both energy harvesting and communication, enables a full two-way proactive interaction with any standard RFID Class-1 Generation-2 reader. It conjugates identification, sensing, local computing, and actuation control, besides being compact, energy-efficient, and easy to use. This paper presents detailed designs of both RF interfaces and digital section, besides discussing system validation and performance evaluation, followed by demonstrating the significance of SPARTACUS in paving the way to new classes of applications in the Internet of Things.