A Delta-Sigma Modulator with a Widely Programmable Center Frequency and 82-dB Peak SNDR

Abstract

A 4-bit fourth-order delta-sigma modulator with a widely programmable center frequency is presented. Novel methods for quantizing and implementing the digitally programmable modulator coefficients enable performance comparable to state-of-the-art discrete-time fixed-frequency modulators at any center frequency from dc to 0.31f s in steps of 0.0052f s . The 0.18-μm 1.8-V CMOS prototype consumes 115 mW at a sampling frequency of 40 MHz. The peak SNDR and SNR over a 310-kHz bandwidth are 82 dB and 86 dB respectively.

Reconfigurable bandpass sigma–delta modulator with programmable NTF for low-IF multi-mode receivers

“…Unlike more traditional tunable BPSDM, where the focus typically is on achieving a tunable center notch frequency of the modulator [1,5], the structure proposed here works by changing the order of the NTF whereby the signal bandwidth and SNR can be optimized for different wireless systems. In Sect.…”

“…However, by avoiding issues of low frequency 1/f noise and I/Q mismatch the low-IF receiver represents a potentially more suited candidate for implementation of flexible platforms for wireless systems [1]. Especially so when the low-IF structure is combined with a bandpass ADC.…”

“…To overcome the limitations of running only at low oversampling ratios, and to still meet SNR requirements, multi-bit DACs are generally employed. In doing so dynamic element matching (DEM) techniques [1,3] or other calibration methods [4] are commonly needed to reduce the effect of DAC related nonlinearity problems caused by device mismatch.…”

A Power-Efficient Tunable Narrow-Band Digital Front End for Bandpass Sigma–Delta ADCs in Digital FM Receivers

“…1(c). Yamamoto et al [2] proposed a widely tunable receiver by introducing a discrete-time (DT) sigma-delta modulator (ΣΔM) with a variable center frequency f c in the IF, as shown in Fig. 1(b).…”

“…The analog mixers necessary in both implementations though suffer from in-phase/quadrature-phase (I/Q) mismatch, dc offsets, channel selection, and local oscillator leakage [1]. Furthermore, the complete AFE is limited by its dynamic range, flicker noise, and phase mismatch [2], [3]. The AFE shown in Fig.…”