A New Estimation Algorithm for CFO and I/Q Imbalance in Wideband Direct-Conversion Receivers

Abstract

Carrier frequency offset (CFO) and inphase/quadrature-phase (I/Q) imbalance are two major impairments of the wideband direct-conversion receivers. They can cause significant performance degradation in multi-carrier modulation (MCM) systems. In this paper, we propose a new two-step algorithm for estimating the parameters of both impairments based on generalized periodic pilot (GPP). Simulation results show that the proposed method has a good performance. Furthermore, the complexity of our algorithm is lower than the existing methods. Index Terms-carrier frequency offset (CFO), frequencydependent I/Q imbalance, direct-conversion receiverswhere ⊗ denotes linear convolution, h(n) is the channel impulse response, and q ch (n) is the channel noise which is assumed to be white. When the system is suffered from CFO and frequency-dependent I/Q imbalance, the received baseband discrete-time signal is no longer given by r(n) in (2). Fig. 1 shows the general structure of direct-conversion receivers. Define y(n) = y I (n) + jy Q (n). Then the received 978-1-4244-9268-8/11/$26.00 ©2011 IEEE This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE Globecom 2011 proceedings.