adaptive antenna array
effect of interfering suppression
This article is devoted to the analysis of adaptive antenna systems (AAS) where the process of signals weighting is implemented in the high frequency domain and based on amplitude and phase control. This eliminates the signal power loss caused by dividing the input signals to their quadrature components in tradition control loops dealing with real and imaginary parts of received signals. Controlled amplitueds and phases form a dynamic (changeable over time) coordinate system in the space of system states and the relative control method should be conformed to it.
Two types of AAS are commonly used: 1) a main antenna whose received signal is not being weighted and a smalll number N of adjusted antenna elements for canceling the received interfering signals: 2) Appelbaum classical schema in which the received signals of all antenna elements are weighted. A goal function for the first type may be just the intensity of the resulted interfering signals at the output of AAS but for the second one an additional condition should be taken. Specifically, it is profitable to use current weights deviation from desired ones as a mentioned condition. Gradient-based algorithms for minimizing the goal function are applied in three ways: adjusting amplitudes, phases or both of them. The computation results for a number of randomly generated situation show notable suppressing the interfering signals due to amplitued or phase controlling, not to mention both ones Amplitude adjusting of the receiving signals proved to be better than phase adjusting. For example, if antenna array consists of 21 elements and six similar interfering sources are located at random directions the average of the adaptation process effect is 25...30 dB in case of amplitude adjusting and 15–20 dB in case of phase adjusting.