An All-Digital Reconfigurable RF Transmitter for Walkie-Talkie Applications based on 1-bit/3-bit Sigma-Delta Modulation

A 65-nm fully digital reconfigurable RF transmitter consisting of a digital front-end (DFE) and a current-mode Class-D (CMCD) power amplifier (PA) is presented. The transmitter can be tuned to the frequency band for Walkie-Talkie from 400MHz to 520MHz. Including a 1-bit/3-bit reconfigurable ΣΔ modulator, the blocks in DFE are synthesized, placed and routed with EDA tools. A CMCD PA with a transformer-based tunable on-chip matching network is integrated. Operating under a 1V supply, it delivers a peak efficiency of 35% at a peak output power of 19-dBm. The TX achieves 11-dBm output power and 60dBc ACPR with 5mW DFE power consumption when a 25-kHz π/4-DQPSK signal is transmitted at 460-MHz.