Enhanced CDMA cellular system using interpolated circular arrays

A spatial interpolation algorithm for the upsampling, beyond spatial aliasing, of uniform circular arrays (UCAs) is presented. Its usage at the base station of a cellular code division multiple access (CDMA) system is considered. The motivation is to improve the user-capacity and array resolution and reduce the fading and coupling effects with a minimal hardware and processing cost. To do so, the real array elements are placed farther apart than λ/2, where λ is the free space wavelength. This increase in aperture enhances the resolution, minimizes coupling, and provides a form of spatial diversity to combat fading. To increase the user-capacity and at the same time eliminate any spatial ambiguities, the UCA is interpolated to within the spatial Nyquist rate. This is done by placing a virtual antenna element on the imaginary circumference half way between every two real adjacent antenna elements