A Modified Hybrid RF Predistorter Linearizer for Ultra Wideband 5G Systems

Abstract

The wide-bandwidth signal transmission is one of the requirements in upcoming 5G communication systems in its quest for high data rates. In this paper, a wideband hybrid RF/digital predistortion (HRF-DPD) linearization technique is reported to compensate for the nonlinearity of ultra-wideband power amplifier (PA) for 5G systems driven by carrier aggregated and wideband modulated signals. The proposed methodology is suitable for 5G PA design, since its power overhead and system bandwidth does not increase with an increase in signal bandwidth. Taking advantage of recent available digital signal processing solutions, the proposed method reduces hardware requirements of the conventional analog predistorter by alleviating the need of vector multiplier, branch line coupler, and delay lines. Such linear operations are controlled digitally, which provides flexibility in terms of digitally compensation of delay, gain and phase control of the signal. For establishing a proof of concept, HRF-DPD is implemented with ZX60V-82+ class AB PA and tested using a 100- and 50-MHz long term evolution-carrier aggregated (LTE-CA) signal at 2 GHz. Experimental results show that the wideband PA along with the proposed predistorter delivers an adjacent channel leakage ratio (ACLR) of −54 dBc with a cancellation of 30.6 dB for 100-MHz LTE-CA signal. With the proposed method PA, nonlinear distortion outside the 100-MHz band can be linearized leading to filter less architecture which provides 45-dBc ACLR performance.