Characterization of spectral regrowth in microwave amplifiers based on the nonlinear transformation of a complex Gaussian process

Abstract

A statistical technique is presented for the characterization of spectral regrowth at the output of a nonlinear amplifier driven by a digitally modulated carrier in a digital radio system. The technique yields an analytical expression for the autocorrelation function of the output signal as a function of the statistics of the quadrature input signal transformed by a behavioral model of the amplifier. The amplifier model, a baseband equivalent representation, is derived from a complex radio-frequency envelope model, which itself is developed from readily available measured or simulated amplitude modulation-amplitude modulation and amplitude modulation-phase modulation data. The technique is used in evaluating the spectral regrowth for a CDMA signal.Index Terms-Amplifier, CDMA, digital radio, nonlinear system.

Characterization of SNDR degradation in nonlinear wireless transmitters

“…Bussgang's Theorem [2,4] provides the theoretical support for this, since by correlating the output and input signals, we can estimate the effective signal component of the output, and thus by subtraction we can also obtain the uncorrelated part, which is in fact the output nonlinear distortion noise.…”

“…From (5) we can also see that the first term is the linear response, the second and third terms are the correlated part of the output signal (referring the input), 2 and the forth term is the nonlinear distortion correlation, usually called in [3,4] spectral regrowth, which unfortunately also has some correlated components with the linear part of the output. This is in fact one of the major problems of nonlinear systems, that is, how to identify the different signal component at the output.…”

“…However these approaches were obtained for memoryless nonlinear components, where the feedforward path could correctly approximate the underlying linear gain of the system, 4 as was presented in [3,8,9].…”

“…The main problem related to this aspect is that most of the authors that have addressed the problem of cochannel nonlinear distortion, have address it for memoryless nonlinear behavior [3][4][5], mainly due to the fact that the systems evaluated where low bandwidth, and analysis and modeling of memory effects were not well understood at the time.…”

Estimation of Intermodulation Rejection Value as a Function of Frequency in Power Amplifier Using AM-AM and AM-PM Diagrams Based on Power Series Analysis

“…The phase variations have an important effect on the spectral regrowth [7]. However, similar previous models only used AM-AM diagram to characterize power amplifier's transfer functions [3,[8][9][10][11] while such an effect is considered in [7,[12][13][14][15]. Although, in this case, transfer function's coefficients have become complex and this increases the difficulty of the calculations, but neglecting the AM-PM distortion causes many problems in predicting output spectrum [16][17][18].…”