Digital Quadrature Mixing of Lowpass Sigma-Delta\ud Modulators for Switch-mode Power Amplifiers

摘要

In this paper a phase compensation technique for the\uddigital upconversion of a quadrature signal for amplification\udwith switch mode power amplifiers is proposed. When a digital\udsignal generator is used to generate the complex envelope signal\udcare must be taken to compensate for the phase skew between the\udtwo paths. If phase compensation is not implemented an image\udcaused by up converting the complex envelope of the modulation\udsignal is created. By compensating for phase skew between the I\udand Q signal paths it is possible to remove this image signal and\udenable the transmission of multi carrier signals. As a direct result\udof this technique there is a reduction in the filtering effort at the\udoutput of the power amplifier to meet spectral mask\udrequirements.