RF tag front-end design for uncompromised communication and harvesting

Abstract

Typically, low-cost and low-power backscatter radio communicators utilize a switching mechanism for alternating the antenna load between two values. In this way, they achieve modulation by reflection of the RF waves induced at the communicator's antenna. For tags that employ a rectifier for wireless energy harvesting, a single transistor may switch between the matched harvester and a reflective load (an open or short). However, optimized backscatter communication occurs when switching between two reflective loads, ideally an open and a short. This prohibits the use of a harvester that requires a good matching (i.e. no reflections) and produces a tradeoff of either compromising communication performance or not employing a harvester. Although this may not pose a problem for commodity RFID tags that operate in short ranges and do not require high computational ability, it is a strong limitation for applications like wireless sensor networks that employ backscatter radio as a low-cost and low-power communication scheme. In this work, an RF front-end is designed, analyzed, and implemented, that overcomes the limitation of compromising communication performance when employing a harvester.