Abstract
In recent mobile communication systems, impairments in analog circuits cannot be disregarded due to achieving high performance. Errors in analog circuits consist of a distortion of a power amplifier(PA), gain and phase imbalance in a quadrature modulator (QMOD) and a quadrature demodulator (QDEMOD), dc offset, frequency offset, and so on. Because of high accuracy of compensation, many techniques of error compensation by using a digital signal processing have been studied recently. Digital predistorter (DPD), which can eliminate odd-order distortion caused by PA nonlinearity, is one of the compensation techniques, but in the case that direct conversion architecture is used in a loop-back path, errors in QMOD and QDEMOD affect the performance of DPD. In this paper, we propose a novel technique for error separation for QMOD and QDEMOD error estimation by adding a phase shifter to the conventional DPD architecture
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