Non Linear Modulation of UHF Tag

Abstract

This paper presents a new modulation and detection scheme for UHF RFID tags. This detection method is not based on the load switching modulation classically used by the tag to communicate with the reader. The principle relies on the generation of a modulated signal by the reader combined with the non-linearity present in any RFID chip (or other non-linear devices). Under specific conditions, we show that the backscattered signal by the tag due to the non-linearity can produce new frequency components located around the carrier frequency used by the reader. These new components can be easily separated from the leakage and the response of the environment in the frequency domain. Moreover this detection can be done at a power which is significantly lower than the sensitivity of the chip. Thus, the associated detection range can be higher than the classical read range of the tag. In measurements, this detection range can be higher than 20 m for a fully passive tag and represents an enhancement of 30% compared to the classical read range.