A Direct Frequency-Interleaving Continuous-Time Bandpass Delta-Sigma ADC

Continuous-Time (CT) Bandpass Delta-Sigma Modulators (DSMs) offer essential advantages for arrayed RF and mm-wave systems, including digital I/Q mixing, innate anti-alias filtering, an easy-to-drive input, and compact chip area. However, existing CT DSMs lack the bandwidth for emerging applications, including 5G and radar. This work presents a practical, direct frequency-interleaving architecture that efficiently scales CT bandpass DSM bandwidth to break the CT DSM bandwidth bottleneck. Multiple CT bandpass DSMs with different center frequencies utilize single-op-amp resonators enhanced with zero-insertion resistors. Simple 3-tap mirrored digital FIR filters efficiently filter the out-of-band quantization noise from each DSM. In addition, Q-enhancement capacitors and neutralization substantially increase the DSM sampling rate. A 28nm CMOS prototype frequency interleaves a pair of CT bandpass DSMs for a total bandwidth of 300MHz, and 37dB SNDR at 1.5GHz. It consumes 38mW.