Angular Displacement Sensor Based on Planar Circular Split Ring Resonator

This paper introduces a planar circular split ring resonator (CSRR) coupled to microstrip transmission line (TL) for the rotation angle sensor. For each rotation angle, the CSRR acts as a stop-band filter and absorbs the signal flow through the TL. The CSRR sensor introduces a resonance at 4.13 GHz with a -10 dB bandwidth of 370 MHz. High attenuation of 40 dB is achieved with reflection of 0.17 dB. A parametric study on the effect of each of CSRR design parameters on the performance of the sensor is introduced. Mathematical modelling of the variations of resonant frequency with different design parameters are derived and verified. The performance of the proposed sensor for rotation angle detection is investigated. A five-elements equivalent circuit model is prepared to represent the inductive and capacitive coupling of the CSRR and TL. The particle swarm optimization (PSO) is employed to find the optimal values of the equivalent circuit elements at different rotation angles.