Turbo Linearizer for High Power Amplifier

Often, to increase the efficiency of high-power amplifiers (HPAs), these amplifiers are driven into a nonlinear region. The nonlinearities in HPAs warp the signal constellation, increasing out-of-band radiation and causing both EVM and BER degradation. Digital predistortion (DPD) is one of the most promising linearization techniques that could lead to more efficient and cost-effective HPAs. The DPD approach works in many practical cases; however, as the bandwidth of the transmitted signal increases, the memory effect in HPAs arises. The performance of DPD algorithms that do not take the memory effect into account severely deteriorate as the bandwidth of the input signal increases. On the other hand, the DPD algorithms that do take the memory effect into account require computational complexity significantly higher than the complexity of DPD for memoryless HPA. In this paper, we propose an exact solution (turbo linearizer) that minimizes the in-band distortion caused by HPA nonlinearity with memory. In contrast to the conventional techniques, the proposed approach places the linearizer on the receiver side. The simulation results show that under certain conditions, the proposed ´turbo scheme´ placed on the receiver side provides better BER performance for a given complexity than conventional DPD placed in a transmitter, especially at higher signal-to-noise ratios.