Effects of implementation impairments in the performance of a W-CDMA smart antenna

The benefits of using smart antennas in a wireless mobile system have been thoroughly studied in recent years, showing an improvement in the antenna gain, a reduction of interfering power and, as a consequence, an increase in the system capacity. The real implementation of a smart antenna for the UMTS system is presented in this paper, focusing on the digital processing module. Implementation impairments produce undesirable effects, such as frequency mismatch and coupling between RF channels. In order to overcome these effects some solutions have been proposed and implemented, and the results are reported in this paper. Since traditional measurement methods are no longer suitable for the characterization of a smart antenna a method to measure the performance of the system is also introduced. The results show the feasibility of the system, which outperforms the features of a conventional sectored antenna. An improvement of 6 dB in gain and 12.5 dB in carrier to interference ratio (CIR) was obtained with this prototype.