Influence of fluctuations of the weight coefficients on the characteristics of adaptive antenna arrays

Abstract

We analyze theoretically the influence of the weight-coefficient fluctuations on the characteristics of adaptive antenna arrays (AAAs) with gradient adjustment algorithms under the assumption that the useful and noise signals have different correlation times. We obtain expressions for the correlation function and the spectral power density of the AAA output signal, find the average radiation pattern (RP), and derive an expression for the correlation matrix of the weight-coefficient fluctuations. It is shown that the weight-coefficient fluctuations bring about distortions of the useful signal and decrease its output power compared with the case of no fluctuations. In the frequency spectrum, this “overcompensation” phenomenon results in the depression of the output signal spectrum of the antenna array in the frequency band where high-power noise exists. As an example, we calculate the spectral power density of the output signal for an AAA with single linear constraints and plot the fluctuation RP and the variance of the weight-coefficient fluctuations versus the noise arrival angle.