A 12-Bit 2 GS/s Dual-Rate Hybrid DAC With Pulse-Error Pre-Distortion and In-Band Noise Cancellation Achieving > 74 dBc SFDR and <−80 dBc IM3 up to 1 GHz in 65 nm CMOS

Abstract

This paper presents a 12-bit 2 GS/s dual-rate hybrid DAC using bandwidth- and linearity-enhancement techniques. The proposed pulsed-error pre-distortion scheme enhances DAC linearity at both low and high signal frequencies by leveraging the fine time-and-voltage resolution from the oversampling path of the hybrid DAC structure. To further widen the DAC bandwidth, a noise-cancellation scheme is proposed to suppress the quantization noise of the delta-sigma modulator within DC to the 1 GHz band without increasing modulator complexity. The analytical derivations and numerical simulations of the proposed techniques are provided to demonstrate the technique's effectiveness, as well as its practical design constraints. A proof-of-concept silicon prototype is implemented in 65 nm standard CMOS that achieves SFDR of 74-98 dBc over the DC-1GHz Nyquist band. In a two-tone measurement, the IM3 product is measured from 101 dBc to 80 dBc across the Nyquist band. The SFDR improvement after enabling the proposed pulsed pre-distortion scheme measures from 67.5 to 74.4dBc, while the in-band noise floor demonstrates 6 dB suppression at the Nyquist band edge after enabling the noise-cancellation scheme.