Strategies for Synchronously Reading Microwave Encoders and Application to Sensors for Motion Control

It is shown in this paper that microwave encoders can be an alternative to optical encoders for sensing linear or angular displacements and velocities. The proposed encoders are made of chains of metallic inclusions on a dielectric substrate. By displacing the encoder over the reader, a microwave element able to determine the presence of inclusions through near field, the relative velocity between the encoder and the reader, as well as the absolute position of the encoder, can be determined. For such purpose, at least one encoder chain must be equipped with a convenient ID code, which must be synchronously read at the instants of time dictated by a clock signal (generated by the same encoded chain, or by means of a different chain). Two prototype examples are reported in order to illustrate the potential of the approach.