High-speed continuous-time band pass ?? modulator for class-S systems
A fully integrated continuous-time bandpass delta-sigma modulator (BPDSM) fabricated in a 0.25?m SiGe BiCMOS is presented. It consists of a two-stage second-order resonator, high-speed comparator, multi-feedback current digital-to-analog converter, and an output buffer. The input frequency can be tuned from 3.55 to 3.9GHz at a 9.5GHz fixed sampling clock frequency. This modulator dissipates 109mA from a 3.3V power supply. The peak signal-to-noise ratio (SNR) of the sine-wave input is 37.3dB in a 20MHz channel bandwidth, and the error vector magnitude (EVM) of a 64QAM long-term evolution (LTE) downlink signal is 5.94% with a 10.5dB peak-to-average-power ratio (PAPR).
continuous-time class-s bpdsm resonator long-term evolution