Novel band-pass ΔΣ modulators based on a modified adder-less feed-forward structure

Two Band-Pass (BP) Discrete Time (DT) ΔΣ modulators are proposed in this paper. In both cases, the drawback of high-speed power-hungry adder is tackled by proposing a modified unity signal transfer function (STF) adder-less feedforward structure. The first proposed BP DT ΔΣ modulator is a conventional adder-less multi-stage noise shaping (MASH) ΔΣ modulator, while the noise leakage problem, caused by the mismatches between analog loop filter and digital cancellation logic (DCL), is mitigated by proposing a second topology in which the DCL is omitted. All of these features make the proposed modulators suitable for low-voltage and low-power applications, while the second proposed topology features a higher robustness against noise leakage and mismatch. Time-domain behavioral simulations show a 0-dBFS overload input level for the proposed architectures while the DC-gain is relaxed for the second proposed architecture such that a 67-dB S NDR can be obtained with only a 30-dB amplifier DC-gain at a -20-dBFS input signal level.