Digital Post-Cancellation of Nonlinear Interference for Millimeter Wave and Terahertz Systems

Abstract

<p>Wideband <u>millimeter</u> wave and <u>terahertz</u> systems face severe <u>nonlinearity</u> and other practical impairments such as transmitter and receiver I/Q imbalances (<u>IQIs</u>), carrier frequency offset, and phase noise. Based on a simplified yet effective received signal model, this paper proposes a low-complexity digital post-cancellation (<u>DPC</u>) framework for transmitter <u>IQI</u> and overall system <u>nonlinearity</u> mitigation. The <u>nonlinearity</u> parameters with reduced <u>nonlinearity</u> order are firstly estimated with low-complexity using a novel transmission protocol incorporating both frame rotation and preamble power scaling. Through widely linear system equalization and interference cancellation, the signal distortion caused by frequency-dependent <u>IQI</u> and <u>nonlinearity</u> are then mitigated with significant performance improvement. The mean-squared-error measurement of the <u>EMP</u>-modelled signals also provides a practical means for the <u>nonlinear</u> system identification and characterization. Both simulation and experiment results obtained from a <u>millimeter</u> wave system with 2.5 GHz bandwidth and 73.5 GHz carrier frequency are presented to verify the theoretical analyses and demonstrate the effectiveness of the <u>DPC</u> technology.</p>