Development of position sensor using phase-based continuous-wave radar

This thesis investigates the potential of a newly developed non-contact displacement sensor using microwaves. Sensors that use microwaves typically are used for detecting, tracking and imaging at long range. It is widely accepted that pulse radar is most suitable for these applications. A few radar systems are employed using continuous-wave radar, but are generally used at shorter range. The existing techniques are not capable of measuring on the micro scale or at high speed. A new technique, developed in this research, using phase-based continuous-wave radar promises such capabilities.; This thesis presents derivation and explanation of the basic operation of a new and improved sensor that measures ultra-fine displacement. The calibration methods for a basic system are provided. In addition, an adaptive calibration concept is introduced to allow the sensor to operate off-the-shelf. The calibrated radar sensor is tested for its accuracy and repeatability against a reference sensor. The variance of the output displacement is found to vary in a deterministic fashion over the range. An extensive study of this variation is presented.; A multi-channel system is proposed in order to improve repeatability of the measurement by means of data fusion. A Kalman filter is used to estimate output displacements with respect to multi-channel signal inputs and approximate variances. Such a data fusion procedure is implemented and tested to verify its robustness on both simulation and experimental signals. The repeatability of the multi-channel sensor is measured and compared with the repeatability of the basic system. As expected, using data fusion results in a smaller variance of the resulting displacements. In addition, the variation of variance with respect to the displacement is found to decrease.; The concept of multipath is introduced to explain repeatability error observed in experiments. The multipath effect in the radar signal is modeled and quantified. An experiment is conducted to determine multipath factors on the configurations of measurement. Finally, various applications are tested with the developed radar sensor: vibration measurement, commutator profile measurement. The test results demonstrate the potential of the sensor on these applications, and provide a direction for future work in this area.