Distortion arising from polar to PWM/PPM conversion in an all digital upconverter for switching rf power amplifier

Analysis of distortion in pulse modulation converters for switching radio frequency power amplifiers

“…The problem was attributed to non-linearities in the modulation process. The authors verified this in [11].…”

“…The image and the third harmonic can be seen rising far above the noise floor. It can also be noted that the average noise floor is much lower compared to the similar spectrum plot in [11] where the Σ∆ filtering was performed on polar signals. Fig.…”

ΣΔ modulator for digital wireless architecture: A review

“…However it is harder to achieve GHz sample rates (Is) for the DSP and L� modulators without resorting to application-specific and phase $(t)) signals rather than the more normal l-Q representation. The polar L� structure was proposed in [12][13][14][15] where the aim was to reduce the switching activity and also to eliminate the need for analog components. Fig.…”

“…The polar �� based burst-mode architecture proposed in [15]. Bassoo et al in [14] investigated the polar �� structure which is shown in Fig. 8.…”

“…Besides that, the conversion process of l-Q complex baseband from Cartesian fonnat to 85 polar format is a nonlinear process which causes some of the quanti sat ion noise to fold back into the band of interest and hence it cannot be filtered out [17]. [14].…”