A 0.1–6.0-GHz Dual-Path SDR Transmitter Supporting Intraband Carrier Aggregation in 65-nm CMOS

A 4.8-mm² 0.1-6.0-GHz dual-path software-defined radio transmitter supporting intraband carrier aggregation (CA) in 65-nm CMOS is presented. A simple approach is proposed to support intraband CA signals with only one I-Q baseband path. By utilizing the power-scalable and feedforward compensation techniques, the power of the wideband analog baseband is minimized. The transmitter consists of a high gain-range main path and a low-power subpath to cooperatively cover different standards over 0.1-6.0 GHz with more flexibility. The reconfigurable power amplifier (PA) driver achieves wideband frequency coverage with efficiency-enhanced on-chip transformers and improved switched-capacitor arrays. This transmitter achieves <;-50-dBc image rejection ratio and <;-40-dBc local oscillating signal leakage after the calibration. System verifications have demonstrated -31/- 51-dBc ACLR1/ACLR2 (adjacent channel leakage ratio) at 3-dBm output power for 2.3-GHz LTE20 in the main path and 1.7% error vector magnitude (EVM) at 1.5-dBm output for 1.8-GHz WCDMA in the subpath. Both paths enable SAW-less FDD operations with -153 or -156 dBc/Hz carrier-to-noise ratio at 200-MHz frequency offset. Finally, the dual CA signals with 55-MHz frequency spacing are verified, showing the EVM of 1.2% and 0.8%, respectively, and exhibiting the intraband CA capability.