Microwave Encoders with Synchronous Reading and Direction Detection for Motion Control Applications

A novel encoder/reader system for motion control applications operating at microwave frequencies is proposed. The encoder is based on two linear chains of metallic patches etched on dielectric (movable) substrate, whereas the reader (sensitive part) is a transmission line section loaded with three resonant elements (CSRRs). The CSRRs are able to detect the patches, when they are in close proximity, by simply injecting three harmonic signals (tuned to the resonator frequencies). This encoder/reader system exhibits the following features: (i) it provides the absolute position (not incremental); (ii) it exhibits synchronous reading, necessary to correctly infer the ID code if the velocity is not constant; (iii) it provides the instantaneous encoder velocity; and (iv) it discriminates the motion direction. In order to demonstrate the potential of the approach, a prototype encoder/reader system is designed, fabricated, and validated.