The Reciprocity Characteristic of Smart Antennas in CDMA System

Smart antennas (SA) has not been applied widely in 3G except TD-SCDMA. As to the application of SA in CDMA system, we argued that people hold certain incorrect view, especial the reciprocity characteristic. Generally, people consider that only using a set of SA, we can simultaneously realize multiple CDMA channels directional transmission on a single carrier frequency with the same uplink & downlink SNR gain, and the transmitting beamforming can be realized by amplitude-weight transmitting baseband signal just like the receiving beamforming. For these views about the SA direction-transmission principle in CDMA system, we did careful analysis. We proved that these opinions mentioned above are incorrect. In order to take good use of smart antennas (SA) in the CDMA system, we also proposed a feasible carrier weight method.