Analyzing the signal-to-noise ratio of direct sampling receivers

The increasing demand for multi-mode multi-band operation in mobile communications requires flexible radio frontends. Direct sampling receivers are very promising for this purpose. For this class of receivers, a proper parameterization of the analog-to-digital converter, in terms of input bandwidth, sampling frequency, and quantization resolution, is essential for its operation. This paper evaluates prospects and challenges of direct sampling receivers analytically. The impact of the sampling frequency and the quantization resolution on the signal-to-noise ratio of the received bandpass signal is approximated with a closed-form analytical expression. This is used to compare the performance of direct sampling receivers to the performance of traditional homodyne receiver concepts. Furthermore, an optimal choice and the trade-off between sampling rate and quantization resolution are discussed for direct sampling receivers that are intended for the reception of LTE signals.