The Research Of Linearization Technology On Power Amplifier At High Peak Average Power Ratio Signal

The nonlinear distortion of power amplifier(PA) tends to be worse under the high PAPR signals. In this paper, we focused on the solution of the linearization techniques of PA under high PAPR signals deeply, and the main works can be summarized as following four parts.First, this paper analyze the effects of high PAPR signals on the PA characeteristics, and determine the PA linearization scheme at high PAPR signals, which is crest factor reduction(CFR) cascade digital pre-distortion(DPD). Then, it put forward the detailed system architecture, technical route, singleband PA linearization scheme structure and multiband PA linearization scheme structure, determine the related testing solution and improving target at last.Second, as for the singleband and multiband high PAPR signal, this paper using the singleband frequency domain CFR technology and multiband CFR technology based on frequency domain to reduce the PAPR of signals respectively. At first, the signal is clipped in the time domain according to the set clipping factor to obtain the corresponding reduction of PAPR. Then it take corresponding inband and outband processing with error vector based on specific EVM threshold and spectrum mask, which can ensure the clipped signal doesn’t exceed threshold by given. Experiment results shows that the CFR technology can obtain different degrees of PAPR improvement in the limit of different clipping parameters.Third, in order to compensate the PAs nonlinear distortion, the iterative DPD method and the multi-stage DPD method are used to improve the modeling precision and compensation capability. The experimental results show that the iterative DPD method to test the class F amplifier ACPR improved the 16.93 dBc and multi-stage DPD method to test the class AB amplifier ACPR improved 18.29 dBc under the special parameter setting. Through the separation parameters of DPD is the pre-distortion coefficient of the identification process and look-up table generation algorithm under DSP, only in the FPGA realization of pre-distortion function, thereby reducing the predistorter hardware implementation of the required resources.At last, this paper using singleband PA and dualband PA respectively at high PAPR signal for validation of linearization scheme. For the singleband PA, using a bandwidth 20 MHz, PAR 10.38 dB of LTE signal for validation, maintaining average power operating mode, the ACPR improvement 17.17 dBc, maintaining peak power operating mode, the ACPR improvement 15.68 dBc and the PA output power increased 1.4dBm at the same time. For the dualband PA, using a PAPR 9.62 dB of dualband signal that each band was a different 5MHz bandwidth WCDMA signal for validation, maintaining average power operating mode, the ACPR improvement 14.47 dBc and 14.87 dBc, respectively, maintaining peak power operating mode, the ACPR improvement 13.39 dBc and 13.65 dBc, respectively, and at the same time, the PA output power increased 0.7dBm. Compared with traditional structure of DPD scheme has large improvement.