A conceptual evaluation of frequency diverse arrays and novel utilization of LFMCW

Thesis Type: Doctorate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey

Approval Date: 2011


Supervisor: ŞİMŞEK DEMİR


Phased array based systems have extending applications in electronic warfare, radio astronomy, civilian applications with technological advancements. The main virtue offered by these systems is the creation of agile beams with utilization of phase shifting or delay elements. In fact, the desire for flexible steering comes with a cost. Frequency Diverse Array (FDA) concept is another approach to beam steering problem. In this context, the subsequent antenna elements are fed with stepped discrete frequencies causing continuous scanning of space in time. So a range-angle dependent scanning is made possible. Also the diversity of waveforms between the antennas is another area of research especially in Moving Target Indicator (MTI) applications. Although several implementation schemes were proposed, the costs and the non-ideal behavior of building blocks make the schemes hard to implement. During this study, a new implementation scheme is proposed where a Linear Frequency Modulated Continuous Wave (LFMCW, Linear FMCW) source is used for feeding a special beam forming network, where the subsequent outputs of the beam forming network have uniform delays. The dynamic behavior of the source and the uniform (or non-uniform) delay provided by the beam forming network create the required frequency steps between antenna elements as described in conventional FDA. So, the implementation of FDA concept requires just the design of the source, beam forming network and the antenna array. Throughout the study, mathematical analysis of both conventional FDA and the LFMCW based FDA is made and various implementations are realized. Justification of the mathematical derivations is made by the results of the measurements with the implemented structures. Besides, analysis and simulation of the array in a radar environment with various scenarios are performed. The drawbacks and the proposals for overcoming these drawbacks are also reported during the analysis, which will be useful for future studies on the subject.