Analysis of TX-harmonics suppression in RF-DAC-based transmitters

In this paper we provide a mathematical description of up-conversion and digital-to-analog conversion in a radio-frequency digital-to-analog-converter (RF-DAC) and analyze harmonics appearing in the up-converted signal. We show a relation between the shape of the local oscillator (LO) signal and the amount of suppression of harmonics. Moreover, we propose a novel approach for increasing the sampling frequency in an RF-DAC without increasing the operational frequency and utilizing already existing analog components of the differential RF-DAC structure. Therewith, the even-order harmonics are additionally suppressed and the quantization noise around the carrier frequency is improved by 3 dB.