3-D-Printed High Data-Density Electromagnetic Encoders Based on Permittivity Contrast for Motion Control and Chipless-RFID

The 3-D-printed electromagnetic encoders based on permittivity contrast are presented and discussed in this article. The encoders, implemented using exclusively dielectric materials, are based on linear chains of dielectric inclusions. Two types of encoders are considered: 1) those where the inclusions are simple apertures made on a 3-D-printed dielectric plate (or substrate) and 2) those with inclusions made of high dielectric constant material 3-D-printed on a dielectric substrate (also 3-D-printed). In both cases, encoding is achieved by varying the dielectric constant of the substrate at predefined positions by means of the inclusions. For encoder reading, a microstrip line loaded with a slot resonator (etched in the ground plane) and a series gap is proposed. Such structure is very sensitive to short range dielectric constant variations, being able to detect the presence or absence of closely spaced inclusions when the encoder is displaced on top of the sensitive part of the reader, the slot resonator. For that purpose, the reader line is fed by a harmonic signal conveniently tuned, so that an amplitude-modulated (AM) signal containing the identification (ID) code is generated at the output port of the line. The proposed reader/encoder system is useful for motion control applications (linear displacement and velocity sensors) and for near-field chipless-radio frequency ID (RFID). Lower cost and major robustness against mechanical wearing are potential advantages of these encoders over other electromagnetic encoders based on a similar principle but based on metallic inclusions.