Complete Link Budgets for Backscatter-Radio and RFID Systems

TLDR

Backscatter radio uses modulated signals reflected from passive RF tags, requiring separate power‑up and backscatter links, and because tags are severely power‑constrained, detailed knowledge of the backscatter channel is essential to optimize system performance. The article presents four link budgets that account for the major propagation mechanisms of the backscatter channel and discusses each in detail. The link budgets are illustrated with a practical UHF RFID portal example, and an intuitive analogy for antenna polarization of RF tag systems is provided. The study demonstrates the benefits of future 5.8 GHz multi‑antenna backscatter‑radio systems.

Abstract

Backscatter radio - wireless communication by modulating signals scattered from a transponder (RF tag) - is fundamentally different from conventional radio because it involves two distinct links: the power-up link for powering passive RF tags, and the backscatter link for describing backscatter communication. Because of severe power constraints on the RF tag, a thorough knowledge of the backscatter channel is necessary to maximize backscatter-radio and radio-frequency identification (RFID) system performance. This article presents four link budgets that account for the major propagation mechanisms of the backscatter channel, along with a detailed discussion of each. Use of the link budgets is demonstrated by a practical UHF RFID portal example. The benefits of future 5.8 GHz multi-antenna backscatter-radio systems are shown. An intuitive analogy for understanding the antenna polarization of RF tag systems is presented.