a) Design a 21-element broadside array with a spacing d = lambda/2. The required
ID: 3884254 • Letter: A
Question
a) Design a 21-element broadside array with a spacing d = lambda/2. The required array factor pattern should closely approximate the sectoral pattern given by SF = {1 50 degree lessthanorequalto theta lessthanorequalto 130 degree 0 elsewhere Determine the excitation coefficients using the Fourier method and compare the resulting pattern with the desired pattern (plot of the normalized patterns) b) Calculate the progressive phase shift of excitation to scan the main beam to the direction 60 degree. c) Use the results from part (a) and part (b) to plot the resulting radiation pattern in dB.Explanation / Answer
Today's cellular communication systems are primarily designed to provide cost effective wide-area coverage for users with moderate bandwidth demands (voice and low data rate). The very high data rates envisioned for next generation wireless systems in reasonably large areas do not appear to be feasible with conventional cellular architecture. The reasons being the proposed spectrum higher than the 2GHz band and more vulnerable radio propagation in higher bands in non-line-of-sight conditions. Another restriction is the lack of bandwidth needed to provide Mbps transmission over the cellular networks. The brute force solution to these concerns is to increase the density of base stations and the operators need to build a dense “forest” of base stations to provide wireless broadband over the coverage area. But the increase in base station numbers will result in considerably higher deployment and operation costs, and would be feasible if the number of subscribers is also increased. Also costs for additional infrastructure, and hence cost for additional services to be delivered over the cellular networks cannot be radically higher in comparison to the existing systems such as Wireless LAN at an airport or hotel, or simply a wired high speed connection at office or at home. It is obvious from the above discussion that some fundamental enhancement or upgrading is required for the ambitious data throughput and coverage requirements of future systems, and
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