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The previously described hybrid smart-antenna system solves the transmitter receiver alignment problem of 60-GHz wireless systems when high gain antennas are used. Utilizing multiple highly directional array elements and coherently combining the outputs of a few elements adaptively, the hybrid smart antenna achieves the desired performance and results in significant hardware cost and computational complexity savings. For optimal alignment, however, the output power of the hybrid smart antenna should stay constant over the scanning range. This minimizes the so-called scalloping effects and necessitates a careful selection of the array elements being used in beamforming. In this letter, a genetic-algorithm solution to optimally adjust the beam pattern overlaps the array elements to minimize the output-power fluctuations in a given scan range. It is shown that while the hybrid algorithm may perform satisfactorily with less than one-third of the total number of the array elements (e.g., two or three elements in an array of ten antennas), there is an optimal number of elements for a given array that provides minimal power fluctuation in a specified scan range. A tradeoff between the acceptable level of power fluctuation and the total received power is identified.
Antennas and Wireless Propagation Letters, IEEE (Volume:7 )
Date of Publication: 2008