Addressing IQ mismatch in Spatial Interference Suppression systems

Second order statistic based Spatial Interference Suppression has been shown effective in suppressing strong interference from jammers or concurrent transmissions. However, hardware impairments in the RF front end can be a major impediment to the design of such systems since the interference can be several orders of magnitude stronger than the signal. IQ mismatch is found to limit the interference suppression ability due to the creation of additional interference eigen modes from the image band of the interference source. We show how the concept of expanding the received signal sub-space can be used to mitigate this effect, and present an architecture for interference suppression in the presence of IQ mismatch. Simulation results indicate 12 dB more interference suppression when using the proposed architecture to compensate for IQ mismatch in indoor environments.