ECE 123 Assignment 2 Spring 2010 This problem set is due Tuesday April 13 at 2:00 PM. Broadcast Antenna Array: The goal of this project is to design a vertical array antenna for broadcast. It is located in Eastern Colorado where the land is flat. The desired pattern is isotropic in azimuth but narrow in elevation. It has a –3dB beamwidth of 50 ± 10 centered on θ = 900 . There must be no sidelobes or grating lobes with gain higher than that of the first side-lobe (approx –13.5dB with respect to the main beam). The elements are vertical magnetic dipoles (horizontal loops) with power pattern ∝ sin 2 θ . The optimal (cheapest) design will have as few elements as possible. The design problem is to determine the number of elements N and their spacing d (in wavelengths). The actual wavelength does not matter, but for the sake of concreteness you can assume that it is an FM antenna and the wavelength is 3 m.
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