Phase-Modulation All-Dielectric and “Green” Electromagnetic Encoders for Motion Sensing and Near-Field Chipless-RFID

Abstract

In this paper, a new electromagnetic encoder system for motion sensing and near-field chipless-RFID applications is presented. The system consists of an encoder, based on chains of transversally oriented linear apertures in a dielectric substrate, and a reader with an open-ended quarter-wavelength resonator that is sensitive to the presence of the apertures. The reader can detect variations in the phase of the reflection coefficient due to the motion of the encoder. To validate the encoder system, two encoders are implemented in a low-loss rigid substrate, and four are fabricated in flexible substrates, such as paper and plastic (polyethylene terephthalate -PET). One of the rigid encoders is incremental (with a periodic chain of apertures) and the other one is quasi-absolute (with two aperture sizes), useful for both motion sensing and near-field chipless-RFID. For the encoders implemented in flexible substrates (quasi-absolute in all cases), the apertures are replaced with linear chains of small holes, with a period of ${p}{=}2$ .3 mm. The resulting density of bits per unit length is DPL ${=}4.35$ bit/cm. Such encoders provide a means to implement cost-effective and eco-friendly (“green”) systems.