This thesis presents a detailed system-level analysis of an all-digital transmitter hardware based on the Direct-Digital RF-Modulator (DDRM). The purpose of the presented analysis is to evaluate whether this particular transmitter architecture is suitable to be used in LTE / LTE-A mobile phones.
The DDRM architecture is based on the Radio Frequency Digital-to-Analog Converter (RF-DAC), whose system-level characteristics are investigated in this work through mathematical analysis and MATLAB simulations. In particular, a new analytical model for the timing error in the distributed upconversion is developed and verified. Moreover, this thesis reviews the LTE and LTE-A standards, and describes how a baseband environment for signal generation/demodulation can be implemented in MATLAB. The presented system enables much more flexibility with respect to current commercial softwares like Agilent Signal Studio.
Simulation results show that the most challenging specification to meet is the out-of-band noise floor, because of the stringent linearity and timing requirements posed on the RF-DAC. This suggests that new means of reducing the out-of-band noise in all-digital transmitters should be researched, in order not to make their design more complicated than for their analog counterpart
