Robust IQ imbalance estimation and compensation via specific preamble for 60 GHz systems

The direct-conversion transceiver is an attractive architecture for 60 GHz wireless systems to meet the low-cost and low-power-consumption requirements, but it suffers from the IQ imbalance problem seriously. This paper adopts secondorder moment estimation to extract frequency-independent IQ imbalance parameters, and performs IQ compensation based on the estimation results. In order to achieve robust estimation, we employ a specific preamble sequence, where adjacent symbols have a fixed phase difference of π/2. The proposed estimation excels in the following aspects: (1) it completely eliminates the impact of inter-symbol interference (ISI) and carrier phase offset (CPO); (2) it is not degraded by carrier frequency offset (CFO), since the impact of which only lies in the negligible phase offset during only a symbol duration; (3) it has low computational complexity and can be implemented on hardware platform expediently. Simulation results indicate that the estimation algorithm has competitive performance over a large range of IQ imbalance, and with IQ compensation the bit-error-rate (BER) performance can be improved to that of the ideal case.