loading page

Q Imbalance and Nonlinearity Mitigation at Wideband Wireless Receivers
  • +2
  • Xiaojing Huang ,
  • Hao Zhang ,
  • Anh Tuyen Le ,
  • Andrew Zhang ,
  • Jay Guo
Xiaojing Huang
University of Technology Sydney

Corresponding Author:[email protected]

Author Profile
Hao Zhang
Author Profile
Anh Tuyen Le
Author Profile
Andrew Zhang
Author Profile

Abstract

Digital predistortion (DPD) has been widely used in microwave transmitters to remove the signal distortion and spectral re-growth caused by nonlinear high power amplifiers and I/Q imbalanced up-converters. However, a DPD can hardly be implemented at a wideband transmitter operating at millimeter wave or terahertz frequency. In this paper, a low-complexity digital post-cancellation (DPC) framework is proposed for I/Q imbalance (IQI) and nonlinearity mitigation at a wideband receiver. The DPC is based on a novel expanded memory polynomial model which captures the IQI and nonlinearity over a complete signal chain including both transmitter and receiver. The nonlinearity parameters with reduced nonlinearity order can be efficiently estimated 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 IQI and nonlinearity can be mitigated with significant performance improvement. Considering the presence of carrier frequency offset at a practical receiver, blind receiver IQI estimation and compensation methods are also proposed in conjunction with the DPC. Both simulation and experiment results obtained from a millimeter 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 DPC technology.