A New Method for I/Q Impairment Evaluation in OFDM Transmitters

The paper focuses the attention on orthogonal frequency division multiplexing (OFDM) digital transmitter testing and troubleshooting, with particular regard to I/Q impairment detection and estimation. Due to the modulation technique peculiar to OFDM, methods based on the I/Q diagram analysis, designed for traditional I/Q transmitters, cannot profitably be applied. A new measurement method for non-intrusive OFDM transmitter testing and troubleshooting is proposed. The method is based on an analytical model that properly accounts for the way I/Q impairments affect the output signal, with special regard to mirror sub-carrier interference, and implements an original procedure to estimate impairment amounts. Besides presenting the analytical model along with fundamental steps of the method, the paper gives details of the extended experimental activity carried out on actual signals in order to assess its performance