Linear Time-Variant Chipless RFID Sensor

In this paper, we present the first chipless sensor which does not satisfy the definition of a linear time-invariant system. This rotational sensor is able to break the time-invariance classically associated with chipless technology by modulating the reflected power in the time domain. As a result, this sensor is able to backscatter power at a frequency different to the one used by the reader and function of the rotational speed. A new identification scheme based on the power of the modulated backscattered tag signal is also introduced and allows to identify different tags. Coding capacity has been evaluated at 11 bits with a probability of correct detection of 98%. Linear time-variant systems allow also to simplify the reader architecture, read multiple tags and increase the read range for both sensing and identification. We show that the proposed chipless sensor could be read at a distance higher than 10 m. This result outperforms classical read range of chipless tag by a factor of 30.