Effect of signal power variation and pattern constraints on an adaptive antenna array system

Abstract

Adaptive array antenna systems are currently the subject of intense .interest and investigation I development for radar and communications applications. The principal reason for the use of adaptive arrays is in their ability to "automatically steer nulls onto undesired sources of interference, thereby reducing output noise and enhancing the detection of desired signals. These systems consist of an array of antenna elements and an adaptive receiver processor which has feedback control over the element weights. The concept of the adaptive system works on the principle of minimizing the output power under the constrained response to specified directions. The present work studies the behaviour of the adaptive array system depending on the signal power of the desired signal and the interference sources, and also on the placement of directional c6nstraints ,in the system. A brief theoretical analysis and intensive computer simulation on this directional constrained system are presented. The results confirm that the algorith~ used is able. to iteratively adapt variable weights on the tap of the sensor array to minimize noise power at the array output subject to certain constraints on the mainlobe as well as on the sidelobes of the array response pattern. A number of interesting observations regardin~ the behaviour of this adaptiv~ antenna iystem in presence of the desired signal and interfering noise of varying power levels are also revealed. Detailed discussion is held for all types of simulations and inferences are drawn about the response of the array under different signal environment as well as pattern constraints.