A novel unbalanced phase calibration technique for the LINC transmitter

In this paper, a novel unbalanced phase calibration technique for a linear amplifier with nonlinear components (LINC) transmitter is presented. By using the proposed unbalanced phase calibration technique, both phase and amplitude mismatches of the LINC system can be calibrated with only phase controls. Moreover, the mismatches can be easily detected with simple phase-only test vectors. This work was verified by system simulations using a 7 MHz bandwidth 64QAM WiMAX signal. With 15° phase and 4dB amplitude mismatch, the proposed unbalanced phase calibration improved the linearity from - 18.88dB to -34.92dB in EVM and from -30.6dBc to -42.4dBc in ACPR at 10MHz offset even though those with conventional phase calibration technique were -20.3dB and - 33.8dBc, respectively. This novel unbalanced phase calibration technique also satisfies the EVM requirement for a 7MHz Bandwidth 64QAM WiMAX system (-31dB), up to 5.2dB amplitude mismatch.