Two-Dimensional Wide Dynamic Range Displacement Sensor using Dielectric Resonator Coupled Microwave Circuit

Abstract: In this paper, the authors propose a two-dimensional, wide dynamic range, linear displacement sensor using microwave methods. The microwave sensor circuit employs a cylindrical dielectric resonator proximity coupled to a pair of orthogonal microstrip lines formed on a microwave substrate. The DR rests on the substrate and is free to be displaced between the strips on the 2D plane of the substrate. The strips excite the particular resonant mode of the DR, the intensity of which varies with the DRs proximity to the strips. The DRs position can thus be read out in terms of the 2 port S parameters of the circuit, at a fixed frequency determined by the resonant mode of DR. Such fixed frequency sensors are robust in operation and cost effective in realization, an important aspect of this sensor. Initial one-dimensional positioning simulations of the sensor through three fixed representative paths on the substrate reveal that the S parameters vary monotonically with the displacement. Prototype measurements reveal a dynamic range of 23 mm for horizontal or vertical displacement, and 30 mm for diagonal displacement at the resonant frequency of 3.67 GHz. Next, 2D positioning test is conducted and a technique for one to one mapping from the S parameters to the 2D position is demonstrated. To conclude, the proposed sensors performance is compared with that of existing 2D sensors.