Sensitivity of single-bit continuous-time Delta Sigma analogue-to-digital converters to out-of-band blockers
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The sensitivity of single-bit continuous-time (CT) analogue-to-digital converters to out-of-band (OOB) blockers received in companion with desired signals is investigated. In essence, the residual interferer signal appearing at the output of the CT loop filter can flip the single-bit quantiser decision near the zero crossings of the loop filter output signal. An intuitive analysis of this effect on the performance of single-bit modulators in the presence of OOB interferers is provided. System level simulations for a single-bit fifth-order CT modulator at an oversampling ratio of 40 have been carried out. A reduction in the achievable signal-to-noise-plus-distortion ratio, that can be as large as 10dB when applying a 0 dBFS OOB blocker tone along with a weak -75dBFS desired tone, has been observed. The simulation results show good agreement with the adopted theoretical discussion. 2010 The Institution of Engineering and Technology.
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