The effects of power amplifier nonlinearities and CFR on 64QAM HSDPA Waveforms

This paper describes the effects of nonlinear amplification and crest factor reduction (CFR) on a 3GPP WCDMA 64QAM HSDPA signal, specifically Test Model 6 (TM6). The nonlinearity is obtained by over-driving a class-A biased power amplifier (PA). The relative code domain error (RCDE) and the ACLR are measured for several input power levels to determine the sensitivity of each relative to the WCDMA standard. It is shown that if the linearity of the PA is sufficient to pass the ACLR specification, it will easily pass the RCDE specification. The excess margin in RCDE allows for the application of CFR, which can reduce the peak-to-average power ratio (PAPR) of the TM6 signal to 5.7 dB and still pass the RCDE specification.