Polarimetric Microwave Sensor for Angular Speed Measurement

This paper presents a design methodology and prototyping of an angular speed sensor based on microwave polarimetry. The detection mechanism relies on the transmission response of a dual-polarized circular aperture irradiating an array of regularly spaced copper traces. The generated response is a regular pulse train defined by the location of a copper trace with reference to the center of the circular aperture. For speed measurement, the response was acquired within a 10s duration with the circular aperture response effectively sampled at 100 Hz. The acquired response was analyzed in the frequency domain using Fast Fourier Transform (FFT) and the rotor speed was obtained from the frequency spectrum of the acquired pulse train. The detection system can detect speeds as low as 0.4 RPM with an upper limit of 5000 RPM limited by the maximum sampling rate of the acquisition system. With the adoption of the FFT technique for speed estimation, the proposed angular speed measurement system can instantaneously detect angular speed with a maximum absolute estimation error of 0.0625 RPM within the 10 s acquisition time. The rotor occupies an area of 84.64 cm².