A 2.5-GHz 4.2-dB NF direct ΔΣ receiver with a frequency-translating integrator

Abstract

This paper presents a 2.5-GHz RF-to-digital converter implemented in a 40-nm CMOS technology. The architecture embeds a direct-conversion receiver RF front-end in a 1.5-bit continuous-time ΔΣ modulator loop. This allows simultaneous channel filtering and noise shaping that begins already in the RF stages. The implemented design pays particular attention to the frequency-translating interface at the LNA output, where a programmable impedance enables a tradeoff between receiver sensitivity and maximum SNDR. The receiver consumes 90 mW from 1.1 V, and achieves a state-of-the-art noise figure (NF) of 4.2 dB and 50-dB peak SNDR for a 15-MHz RF bandwidth.