Radio direction finding & smart antennas

Abstract

In this thesis, Radio Direction Finding (DF) and Smart Antennas are studied. DF refers to the science of determining the location of radio transmission sources. A DF system uses the characteristics of the radio signal such as amplitude and phase at each antenna element to estimate the direction of arrival (DOA). In practice, three basic methods are preferred in DF systems; Watson Watt, Interferometer and High Resolution methods. This work focuses on the implementation of a novel DF system based on the interferometer method. However, an ambiguity problem occurs in estimating DOA when antenna aperture becomes larger than the half of the incident signal's wavelength. The dominant work in the rst part of the thesis is resolving this ambiguity in interferometric DF systems. It is veri ed that the FFT based DF system performance is improved with the increasing antenna aperture and that the working frequency bandwidth of the system is also increased by using a single antenna array. The second part of the thesis focuses on Smart Antennas that can dynamically adjust the beam-pointing direction of the antenna array by applying phase delays to the antenna elements. There is a tremendous need and increase in use of smart antennas with the growth of mobile networks. Three basic beamforming approaches are used in smart antennas: xed, switched and adaptive. We propose a novel multi-model beamforming model that integrates the switched and adaptive beamforming systems that combines the advantages of a switched and an adaptive beamforming systems. It gives faster response than an adaptive only system and provides perfect tracking to all possible combinations of desired signal and unwanted signals compared to a switched beamforming only system.