A 1-V 13-mW Single-Path Frequency-Translating ΔΣ Modulator With 55-dB SNDR and 4-MHz Bandwidth at 225 MHz

This paper presents a frequency-translating bandpass Delta Sigma modulator that uses single-path mixing within the Delta Sigma feedback loop to downconvert a 4-MHz signal band from IF1 = 225 MHz at the input to IF2 = 25 MHz at the output. The proposed Delta Sigma modulator is designed with a sixth-order continuous-time loop filter and a 3-bit quantizer. The quantizer operates at a sampling frequency of 100 MHz, which is lower than IF1 and, therefore, reduces both the power consumption and the sensitivity to timing errors relative to a conventional bandpass Delta Sigma modulator. Furthermore, the loop filter implements noise shaping primarily at IF2, which reduces the sensitivity to coefficient variations. The prototype chip was fabricated in 65-nm CMOS with an active area of 0.55 mm(2). It achieves an SNDR of 55 dB over a 4-MHz signal bandwidth, and consumes 13 mW from a 1-V power supply.