Improvement on extracting the static nonlinear behaviours of transmitters with precise delay estimation by increasing sampling frequency

Conference: GeMiC 2014 - German Microwave Conference
03/10/2014 - 03/12/2014 at Aachen, Germany

Proceedings: ITG-Fb. 246: GeMiC 2014

Pages: 4Language: englishTyp: PDF

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Guan, Junqing; Nghiem, Xuan Anh; Negra, Renato (Mixed-Signal CMOS Circuits, UMIC Research Centre, RWTH Aachen University, Aachen, Germany)

This paper discusses and compares the delay compensated characterisation at different sampling frequencies for power amplifiers (PAs). The differences in the accuracy of the extracted AM/AM and AM/PM nonlinear behaviours are investigated. A memoryless DPD based upon the characterised nonlinearity is employed to linearise a highly efficient PA. Measurement results show that a large residual delay due to low time resolution can cause significant dispersions in the AM/AM and AM/PM curves, which can be misinterpreted as memory effects and also degrade the accuracy of the extracted static nonlinear behaviours. The method for improving the nonlinear prediction of a PA by increasing the sampling frequency to reduce the residual misalignment is presented and performed on a highly efficient GaN PA with maximum output power of 41 dBm with drain efficiency of 68% at 2.05 GHz. The measurement results show that the EVM can be improved by 4.9 percentage points together with 25 dB improvement on ACLR and 0.6 dB increase on output power by increasing the sampling frequency by 8 times. With the highest possible sampling frequency of 100 MHz, an EVM of 0.7%, an ACLR1 of -48 dBc and ACLR2 of -58 dBc can be achieved with an average output power of 33.2 dBm and drain efficiency of 50.4% for LTE 5 MHz signals with an PAPR of 7.7 dB.