Passive Direction Finding based on Time Difference of Arrival and Amplitude-Phase Combined Technique

In the first part of this thesis, the implementation of a wideband compact direction finding receiver based on combination of amplitude and phase methods is discussed. Six antennas which have been arranged in a hexagonal array perform as an interferometer and as an amplitude comparison system. The interferometer spacing will be such that ambiguities exist and selection of correct ambiguous angle of arrival will be based on amplitude comparison. A novel selection strategy will be discussed. This selection strategy improves the RMS error of the system. In the second part of this thesis, a novel technique to implement time difference of arrival that takes advantage of Field programmable gate arrays advanced clock management capabilities is presented. The clock management system currently present in almost every field programmable gate arrays allows fine phase shifting of the clock. This feature helps to increase the time difference of arrival resolution. The accuracy of time difference of arrival system is directly proportional to the accuracy with which time difference is measured which is a function of system clock frequency. In this experiment time with high precision is measured by using a low resolution clock employing four phase shifted clock concept within the field programmable gate arrays rather than the traditional measurement concept of using single high resolution clock. Time difference of arrival technique is well suited for emitter direction finding in various applications such as unmanned aerial vehicles, 60-GHz OFDM Communication Systems and Mobile Communications