A contactless position sensing system using Doppler radar

Abstract

The aim of the project was to implement a one-dimensional, short-range, contactless position-sensing system using Doppler radar. Although the Doppler radar returns the velocity of the target, it should be possible to infer the position by integrating the velocity data. The project was based around the MA87728-M01 Varactor Tuned X-Band Transceiver, normally used in traffic lights and speed traps. The module was first characterized in terms of its DC and microwave characteristics, and then set up to obtain Doppler signals from a swinging pendulum bob. The returned signals were digitized and processed digitally usmg PC tools such as Microsoft Excel and Matlab. The processing consisted of filtering to remove noise, followed by extraction of the velocity data. Two techniques were used for this, a simple peak finding method and the Fast Fourier Transform, and the results compared. It was also demonstrated that integration of the velocity signal gives acceptable positional information. The use of Frequency Modulation to directly determine the position of a stationary target was also investigated. However, it was found that with the radar module available this technique could only be used at longer ranges than were intended for this project.