A space-time coding scheme utilizing phase shifting antennas at RF frequencies

We introduce a new technique for performing space-time coding by using a phase shifting antenna feed network to manipulate the transmitted signal at RF frequencies. The advantage of this scheme is that it allows space-time coding to be implemented with only one transmit chain and amplifier. A code-division multiple-access (CDMA) system that can use this method of space-time coding is described. The antenna feed network is presented along with a modified version of the Alamouti code that is suitable for this application. Imperfections in the antenna phase shifting are quantified using an error vector magnitude (EVM) measure. System level CDMA simulations are also used to evaluate the overall performance of this "RF space-time coding" technique. The results indicate a performance improvement equivalent to conventional space-time codes.