A Differentially Quantized Bandpass Error Feedback Modulator for ADCs in Digital Radio

Abstract

Bandpass sigma delta modulators are highly desirable in precision analog-to-digital conversion applications for narrow-band intermediate frequency signals. This paper describes the design, analysis and implementation of a novel differentially quantized bandpass analog-to-digital conversion technique for digital radio application. A new class of noise-shaping data converter, i.e., the differential quantizer-based error feedback modulator, is introduced, which replaces the integrator/resonator with a differential quantizer to achieve noise-shaping characteristics. Thus, integrator-associated non-idealities, loop stability issues and optimization of the integrator scaling coefficients are no more a concern. Furthermore, a comparison to the conventional bandpass sigma delta analog-to-digital conversion is also been presented here. Behavioral-level simulation results demonstrate the mathematical equivalence of the differential quantizer-based bandpass error feedback modulator technique with bandpass sigma delta modulator technique and confirm its novelty, theoretical stability and scalability to higher order. The circuit-level feasibility, hardware efficiency and power efficiency of the proposed architecture are verified in a 45 nm CMOS process with a 1 V supply. Simulation results show a power consumption of 0.62 and 0.95 mW for the proposed and the conventional architectures, respectively.