Oversampled Digital-to-Analog Converter for noise reduction in polar transmitters

Polar transmitters suffer from the problem of having high out-of-band noise. To solve this problem, most of the proposed solutions rely on increasing the sampling rate of the phase branch. In this paper, we present a novel method based on processing the digital radius signal in order to reduce the out-of-band noise. The proposed method modifies the output of the Digital-to-Analog Converter (DAC) in order to overcome the distortions introduced in the phase branch of the polar transmitter. By moving one part of the phase information to the radius path, the implementation of the phase branch can be simplified significantly while the out-of-band noise is reduced and the harmonics are attenuated.