On the Use of FIR Feedback in Bandpass Delta-Sigma Modulators

Description

This paper presents a new architecture for bandpass delta-sigma modulators (BP ΔΣ Ms) featuring finite impulse response (FIR) filters in the feedback path. The effectiveness of FIR feedback in lowpass delta-sigma modulators (LP ΔΣ Ms) has been well-established in improving loop-filter linearity and robustness to clock jitter. Building upon these findings, we explore the application of bandpass FIR filters in single-bit BP ΔΣ Ms. By contrast to conventional BP ΔΣ Ms, the proposed technique significantly reduces out-of-band quantization error contents in the feedback signal. This approach is applicable to both discrete-time and continuous-time implementations. Further, we show that performance does not improve by increasing the number of FIR taps beyond a certain point. However, we can enhance filtering performance by employing non-equal coefficients within the filter. To validate the efficacy of the presented approach, the paper includes electrical simulation of a 4th-order active-RC BP ΔΣM .

Abstract

MCIN/AEI/10.13039/501100011033 and European Union ERDF PID2019-103876RB-I00, PID2022-138078OB-I00

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