Software IQ sample estimation for multi-antenna systems

Multi-antenna systems provide the option to enhance the data rates and to improve the overall system performance as long as high transmitter signal accuracy for all signal branches can be guaranteed. At the same time the analog front-end should provide low power consumption and a low cost solution. Hence a direct-conversion transmitter analog front-end architecture for an OFDM multi-antenna system will be proposed including the drawback of possible imperfect analog IQ signals. The expected analog imperfections will be compensated via software-based algorithms. The compensation techniques require IQ sample estimates from the transmitter envelope signal at the antenna input port. This paper provides a mathematical description of the software-based IQ estimation and provides simulation results in conjunction with a filter pre-equalization and quadrature compensation.