An Evaluation on the Signal-to-Interference Ratio Performance of a Circular Array in CDMA Systems

This paper deals with the interference rejection capability of circular antenna arrays used for smart antenna systems, at base station of a CDMA communications system. In general, this figure of merit depends strongly on the array configuration and is a function of the direction of arrival of the desired signal, the number of antenna elements, and their spacing. The main goal and contribution of this letter is to extend a previous result on the interference rejection capability for uniform linear arrays, to the uniform circular arrays case. A detailed presentation of the behavior of the interference rejection capability of uniform circular arrays is provided, the effect of varying the number of its elements and inter-element spacing on the SIR (signal-to-interference ratio) performance is considered. Analytical results, for the total average of spatial interference suppression coefficient for circular arrays, as a function of inter-element spacing, are provided. These results are compared with a previous result for the linear array case.