CMOS THz-ID: A 1.6-mm² Package-Less Identification Tag Using Asymmetric Cryptography and 260-GHz Far-Field Backscatter Communication

Abstract

This article presents an ultra-small, high-security identification tag that is entirely built in a CMOS chip without external components. The usage of backscatter communications at 260 GHz enables full integration of a 2 × 2 patch antenna array. For chip compactness and minimum interference caused by direct wave reflection, the backscatter signal is frequency-shifted by 2 MHz and radiated with cross polarization from the same antenna array. Such a configuration also, for the first time for RF tags, enables beamsteering for enhanced link budget. For authentication and secure wireless data transmission, the tag also integrates a compact elliptic-curve-cryptography (ECC) dedicated processor, which is based on a narrow-strong private identification protocol. The presented tag has a peak power consumption of 21 μW and can be powered by a chip-wide array of photodiodes and a DC-DC converter. Using a low-cost 65-nm bulk CMOS technology, the terahertz (THz) ID chip has an area of only 1.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and demonstrates the measured downlink speed of 100 kb/s and the upload speed of 2 kb/s across 5-cm distance from the reader. The tag-reader authentication/communication protocol is fully demonstrated using external tag power and partially demonstrated using the tag-integrated photo-voltaic powering. The tag size is the smallest among all prior radio-frequency identifications (RFIDs) using far-field communications.