Method of determining true error vector magnitude in a wireless LAN

摘要

Systematic transmit IQ phase and amplitude imbalances in the transmit chain of a wireless local area network (WLAN) cause a corresponding systematic shift in the roots of a constellation diagram. Additional random phase noise in the transmit chain will cause a further Gaussian distribution of points in the constellation diagram about the systematically shifted roots. This random distribution represents a true error vector magnitude (EVM). By transmitting a known training sequence through the transmit chain, which it is known will be shifted to all of the systematically shifted roots in the constellation diagram, the Gaussian spread around those shifted roots can be analysed to determine the true EVM.