Hybrid Time/Phase Domain Electromagnetic Encoders Based on Electric LC (ELC) Resonators

This paper presents electromagnetic encoders based on electric-LC (ELC) resonators. Such resonators are etched in a dielectric substrate forming a chain, and encoding is achieved by considering different transverse positions of the ELC resonators in the chain. Encoder reading is achieved by measuring the phase of the reflection coefficient of a matched line, the stator, which results by displacing the resonators' chain over the stator at short (vertical) distance. The different transverse positions of the ELC resonators provide different phases, and thus encoding is achieved through phase modulation by ELC (transverse) position. As many states per axial position of the chain as ELC transverse positions result. With this approach, it is possible to enhance the number of bits per encoder (axial) position, as compared to binary approaches (based on absence or presence of inclusion in the chain, corresponding to one bit), or other approaches based on frequency encoding, achieved through the size of the inclusions. A relevant advantage of the proposed approach is that a single-frequency (harmonic) signal suffices for encoder reading. A prototype example, consisting of an electromagnetic encoder with 3.58 bits per axial position, operating at f(0) = 2.2 GHz, is reported to validate the approach.