Exploitation of body interaction effects for the enhancement of a body-borne radio geolocation system.

摘要

Direction finding (DF) and geolocation techniques have been in use for over 60 years in applications as diverse as radio navigation and personal safety beacons. In terrestrial applications, direction finding and geolocation systems have traditionally required at least three sensors to generate an unambiguous solution. However, the recent proliferation of RF devices in search-and-rescue and military applications has generated the demand for body-borne RF geolocation capabilities that use the fewest number of sensors possible.;In this thesis, a two-element antenna system is evaluated for application to broad-band (100-750 MHz) body-borne radio geolocation. In the past, multiple sensors or unique signal characteristics have been required to obtain unambiguous direction finding solutions. A background on terrestrial direction finding and geolocation techniques is exploited to present the theory and challenges behind body-borne integration, including the fundamental limitations of a two-sensor direction finding system.;The presence of a passive scatter, the human body, is thoroughly investigated. The perturbations of this scatterer on the DF system are characterized. Validations of simulated data are conducted using measured data collected with human phantoms. The impact of the human body on the phase and amplitude of the direction finding system response is characterized as a function of frequency and angle of arrival. A new calibration technique is proposed to enhance the accuracy and remove the ambiguities of direction finding solutions by exploiting the effects of the human body interaction.;A multi-variable sensitivity study is used to evaluate the stability of the phase and amplitude of the detected signal in the body-borne environment. Using these data, practical thresholds are established for differentiating between system variability and viable signal detections. These thresholds are used to realize phase-based and amplitude-based direction finding schemes. Two performance metrics are defined, and used to characterize the performance of these direction finding systems.;Based on these results, a new direction finding technique is presented, which combines the independent direction finding solutions from the phase-based and amplitude-based DF schemes. By exploiting the similarities and differences in these individual techniques, the developed algorithm is shown to improve the accuracy of the calibrated direction finding solution of the body-borne system.;Although the primary focus of this thesis is on direction finding techniques (solving only for the angle of arrival), extension to radio geolocation techniques (solving for both angle of arrival and range) are also researched. It is shown that highly accurate angle and range detections are feasible by exploiting the interaction effects and movement of the human body, even with a two antenna DF system.