Delta Sigma digital-RF transmitter with reduced LO leakage using segmented butterfly shufflers

Abstract

Presented is a digital-RF transmitter using multi-bit Delta Sigma modulators with noise-shaped segmentation and butterfly shufflers for shaping mismatches between digital-to-RF converter (DRFC) cells. The segmented butterfly shufflers prevent mismatch errors of DRFCs from aggravating the linearity and the LO leakage of the transmitter. A prototype based on a digitally-intensive top-down design is fabricated in 90 nm CMOS process. Measurement results for wideband-code division multiple access demonstrate an adjacent channel leakage ratio (ACLR) (5 MHz/10 MHz) of -49.6 dBc/-53.9 dBc and an Error Vector Magnitude of 1.89% with a main channel output power of -0.1 dBm centred at 1.95 GHz.