Aliasing-free variable gain Delta Sigma Modulator for use in an analog frontend

We present an aliasing-free variable gain Delta Sigma Modulator (DSM). The variable gain of the 2-1-1 MASH architecture DSM is carried out by using additional sampling capacitors. This feedforward gain adjustment offers better S2-1-1 MASH architecture DSMNR performance than feedback gain adjustments discussed in the literature, since the internal states of the modulator loop are driven at full signal swing. To eliminate the need for an analog anti-aliasing filter, a decimation filter with a sharp cutoff is employed in the reconstruction of the analog signal. The design is carried out in a 0.6 μm CMOS technology. Measurement & implementation results for the above concepts compare favorably with similar designs in recent literature.