DIGITAL-TO-ANALOG (D A) CONVERTERS WITH NONUNIFORMLY SAMPLED SIGNALS/

In this paper, we investigate the problem of the D/A converter with no nuniformly sampled input data, The input digital data were obtained by sampling the intended analog waveform at nonuniform time intervals, a nd we look into the question: ''Given that the timing offset of each d ata sample is known, would it be beneficial, in terms of the output si gnal-to-noise ratio, to use this offset to adjust the playback timing of the D/A converter?'' We examine two different timing strategies, Th e first approach simply plays out the signal at a uniform rate, while the second one uses the known timing offset to adjust the D/A converte r playback timing accordingly, The closed-form expressions of the spec trum of the D/A converter output signals are derived, From these expre ssions, we find that the spectrum structure, for the case where the ti ming offsets are compensated, is the infinite sum of the weighted shif t to the baseband spectrum, For the uniform playout approach, the spec trum structure is much more complicated where each shifted spectrum is modified by a different weighting function of the frequency, Although the spectrum structure may be conceptually simpler for the case where the timing offsets are compensated, it is by no means clear that eith er method is better than the other in terms of the output waveform qua lity. We then apply the results to analyze the direct digital synthesi s output since waves, The signal-to-noise ratio, SNR, for both cases i s derived in simple closed form, It is found that for the case where t he timing offsets are compensated, the SNR can be greatly enhanced by appropriate selection of operation parameters.