I/Q Compensation of Broadband Direct-Conversion Transmitters

Abstract

The aim of this paper is to propose a compensation strategy that is able to easily identify the model of the In-phase/Quadrature (I/Q) impairments of Radio-Frequency (RF) direct-conversion devices and to efficiently compensate these unwanted effects. In fact, direct-conversion transmitters that integrate analog and digital components introduce a wideband frequency-dependent I/Q mismatch that strongly reduces the upconverter performances. The wider the signal bandwidth or the higher its spectral efficiency, the more severe the I/Q artifacts on the upconverted signal become. The proposed compensation strategy can mitigate these unwanted effects, eliminating I/Q impairments with a very simple hardware architecture. The compensation model adopted here for a generic upconverter device does not assume any hypotheses about signal modulation and system architecture and can be easily adapted to accommodate specific hardware systems or different wireless standards. To show the capabilities of the proposed compensation scheme, an experimental setup has been arranged to emulate system configurations found in direct-conversion RF Integrated Circuits (RFIC) for 3.5/4G applications.