Digital-to-Analog Converters Using Frequency Interleaving: Mathematical Framework and Experimental Verification

The concept of frequency interleaving (FI) for digital-to-analog converters (DACs) has recently experienced renewed interest, in order to overcome the DACs' bandwidth limitations. In this concept, the output signals of multiple DACs are interleaved in the frequency domain in order to generate a combined output signal that exceeds both the sampling rate and the bandwidth of a single DAC. In this paper, a mathematical framework for FI-DACs with a large number of DACs is presented and the inherent interdependencies between sampling rate, the number of samples, LO frequencies, symbol rate and analog frequency responses are highlighted. A mathematical expression for the distribution of data samples among the DACs is presented, taking into account bandwidth limitations of the analog components as well as guard bands to mitigate cross talk. In order to balance the FI-DAC's parameters a mathematical optimization approach is introduced and illustrated with examples. Both simulation and experimental results validate the FI-DAC concept, and an outlook on implementation issues completes this paper.