A Nonlinear Feedback Linearized Power Amplifier for Wireless Communication Systems

In modern wireless communication systems, the inherent nonlinearities of power amplifiers (PAs) result in severe distortion and spectral regrowth. To deal with this problem, we propose a nonlinear feedback linearized power amplifier (NFLPA) to compensate for the PA's nonlinearity with an extra radio frequency (RF) feedback chain. By accurately capturing the nonlinear distortion in advance, the distorted signal is subsequently attenuated and coupled with the original input signal to effectively linearize the PA output. Furthermore, the linearization performance of the proposed NFLPA is often restricted by the non-ideal electronic components, which introduce extra loop delay mismatch existing in the feedback chain. To conduct a quantitative analysis of the linearization performance with the presence of loop delay mismatch, the orthogonal frequency division multiplexing (OFDM) modulation scheme is utilized to analyze the residual nonlinear power of the NFLPA output, the expression of which is derived in terms of loop delay mismatch, transmitted signal power, and signal bandwidth. Simulations reveal that the deployment of the NFLPA significantly enhances the linearization performance. Moreover, the degradation effect of loop delay mismatch is simultaneously evaluated based on the adjacent channel leakage ratio (ACLR) performance via simulations.