Adaptive Dual-Input Analog RF Predistorter for Wideband 5G Communication Systems
Ashish Kumar, Meenakshi Rawat
Abstract
Advanced communication technologies like 5G focuses on the wideband signals and high data rate. The quality of wideband signal transmission deteriorates due to the nonlinear characteristics of the power amplifiers (PA). The digital predistortion (DPD) method reduces the distortion and spectrum regrowth, but the sampling speed of the converters restricts its operation to support 5 to 7 times the signal bandwidth. The analog predistortion (APD) method is not limited by the bandwidth of the distorted signal, but its linearization performance is inferior to the DPD. This paper presents an adaptive dual-input APD that establishes the benefit of digital control over the variable parameters to linearize the wideband signals. For the LTE signal with a bandwidth of 20 MHz and RF frequency of 3.5 GHz, the proposed method achieves an ACPR improvement of 24.01 dB. For another LTE-A signal with 100 MHz bandwidth, the proposed linearizer achieves an ACPR improvement of 9.2 dB and 15.7 dB over PA with and without conventional APD. Though the predistorter (PD) is designed for 3.5 GHz, it is reported that due to the wideband operation of APD, digital adaptation allows satisfactory performance for carrier frequency from 2 to 4 GHz.