Signal conditioning for polar all-digital OFDM wireless transmitters

A novel scheme for conditioning OFDM modulated signals is proposed to facilitate the implementation of mixerless all-digital transmitter using polar RF Digital to Analog Converters (RFDACs). The signal conditioning is applied to the OFDM signal to avoid phase discontinuities, thus mitigating the effects of bandwidth expansion in polar decomposition. The absence of mixers and filters offers wide RF bandwidth and takes the design a step closer to reconfigurable transmitter. To validate this concept, the signal conditioning is applied to an LTE signal and sent to a phase modulator circuit. The performance of the phase modulator in terms of signal quality is assessed using Normalized Mean Square Error (NMSE) metric. It is concluded that the signal conditioning results in a signal that may not comply with the existing standards, but is spectrally efficient and thus enables the use of polar architectures for wideband signals.