I. Introduction
As is widely known, power amplifiers (PAs) are the major source of nonlinear distortion and are also the most power consuming devices in numerous industrial electronic applications [1]–[11], e.g., in magnetic bearing [1]–[3], digital video broadcasting [4], radio frequency (RF) transceivers [5]–[8], and dual-band/wideband wireless communications [9], [10]. Specifically, in wireless communications, to enhance the spectral efficiency in modern high-speed wireless communication systems, different nonconstant envelope modulation schemes, such as wideband code division multiple access (WCDMA) [11] in third generation (3G) mobile networks and orthogonal frequency division multiple access in 3rd Generation Partnership Project (3GPP) long-term evolution (LTE), are normally employed. However, these signals usually have a high peak-to-average power ratio (PAPR) and are quite vulnerable to nonlinear distortion in the RF PAs. This requires a large level of power backoff to maintain a high linearity of the transmitted signals, ultimately degrading the power efficiency of the PA.