Mythili, P; Jose, B R; Mathew, J; Pradhan, D K(IEEE, September 26, 2007)
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Abstract:
This paper presents a cascaded 2-2-2
reconfigurable sigma-delta modulator that can handle
GSM, WCDMA and WLAN standards. The modulator
makes use of a low-distortion swing suppression topology
which is highly suitable for wide band applications. In
GSM mode, only the first stage (2nd order Σ-Δ ADC) is
turned on to achieve 88dB dynamic range with oversampling
ratio of 160 for a bandwidth of 200KHz; in
WCDMA mode a 2-2 cascaded structure (4th order) is
turned on with 1-bit in the first stage and 2-bit in the
second stage to achieve 74 dB dynamic range with oversampling
ratio of 16 for a bandwidth of 2MHz and a 2-2-2
cascaded MASH architecture with a 4-bit in the last stage
to achieve a dynamic range of 58dB for a bandwidth of
20MHz. The novelty lies in the fact that unused blocks of
second and third stages can be switched off taking into
considerations like power consumption. The modulator is
designed in TSMC 0.18um CMOS technology and operates
at 1.8 supply voltage.