In most practical applications of the phased array antennas, the generated nulls toward the interfering signals should have enough depth and width to accommodate fluctuations in frequency and direction of the interferer. Due to these fluctuations, the nulls can be easily deviated from its desired angular locations in the traditional adaptive nulling arrays since the nulls are very sharp and sensitive. An innovative technique for wide nulling arrays has been recently presented. The wide nulls can be introduced by setting properly the excitation coefficients of the two edge elements of the antenna array. In this paper, the effect of frequency fluctuation on the nulling performance is investigated. By generating wide and deep nulls toward and around the interference directions, the proposed method provides robustness against frequency fluctuation. Simulation results in realistic situations with frequency fluctuation are presented to illustrate the performance of the proposed technique. Comparisons with the standard fully adaptive nulling array are shown.
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