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We examine the Doppler features from wind turbine scattering through a series of model measurements. Both backscattered and forward-scattered data are collected in the laboratory at Ku-band from various wind turbine models undergoing rotation. The tested models include a 1:160 scale model turbine, a three-arm wire model, and a small wind turbine from Bergey Windpower with 2' blades. The findings from...
In this paper, we present the design for a two-element, closely-spaced, small Yagi structure to achieve high gain. The element design is based on a small folded spiral. All of the antenna dimensions are optimized by using a genetic algorithm (GA) and the Numerical Electromagnetics Code (NEC). The antenna is designed for 900MHz and the prototype of the monopole version of the antenna is constructed...
The Yagi antenna is a standard antenna to achieve high gain in a very simple structure. The antenna is composed of a driver and parasitic elements including a reflector and one or more directors. Designs of the Yagi typically have element-to-element spacing on the order of 0.15lambda to 0.4lambda. For some applications, however, it is desirable to reduce this spacing to achieve a physically more compact...
In this paper, we present the design of a compact Yagi antenna with very close spacing between the elements. The major problem with a Yagi with closely spaced elements is that the radiation resistance is very small, leading to poor efficiency and poor matching. We apply the folding concept to step up the radiation resistance of the antenna to 50 Omega at resonance for element spacing as close as 0...
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