Blind frequency-dependent in-phase/quadrature imbalance compensation with constant norm algorithm and cascaded structure

Abstract

Increasing carrier frequency and broadening bandwidth speeds up wireless communication, but at the price of a frequency-dependent imbalance between the in-phase/quadrature (IQ) signals in the quadrature modulator/demodulator. We propose a blind compensation system for correcting frequency-dependent IQ imbalance in orthogonal frequency division multiplexing (OFDM) systems. As the convergence characteristic of conventional blind adaptive algorithms limits their compensation performance, we introduce a constant-norm algorithm (CNA) and cascaded structure. Simulation results show that the proposed scheme improves bit error rate performance in a frequency-dependent IQ imbalance environment.