A 10-MHz Signal Bandwidth Cartesian Loop Transmitter Capable of Off-Chip PA Linearization

This paper presents a wide signal bandwidth Cartesian loop transmitter (CLT) IC for off-chip PA linearization. The CLT can linearize a 10 MHz bandwidth signal by using a feedforward technique to avoid instability caused by a time delay of an RF path. The transmitter is fabricated in 0.13 m CMOS technology. ACLR is improved from 30.2 dB to 38.4 dB and EVM is improved from 5.9% to 1.6% by using the feedback loop when 10 MHz OFDM signal is applied. The fabricated IC also realizes automatic phase and amplitude calibration by using on-chip amplitude and phase difference detector and external controller and result storage. The controller and result storage are realized by the FPGA. The calibration can be finished in 14 sec.