A Wideband Signal Linearization Method With Nonlinear Signal Injection Structure

The widely used super-heterodyne transmitter structure has high sensitivity, selectivity, and dynamic range. However, the super-heterodyne structure also has mirror image interference, which requires high-performance filters for channel selection and mirror image suppression. Power amplifiers (PAs) with high efficiency and linearity are also essential for transmitters. However, the non-linear characteristics of the PA will lead to the amplifier output signal bandwidth being broadened to 5 ∼ 10 times the baseband. With such a large bandwidth, the performance of super-heterodyne structures can be limited by devices such as filters and mixers. In this paper, a new architecture is proposed to address the problem of limited filter performance of the super-heterodyne transmitter in the conventional digital pre-distortion (DPD) architecture. Based on the traditional DPD architecture, an auxiliary transmitter channel is added to transmit the nonlinear part of the DPD signal. Simulation results show that the method can effectively optimize the ACLR of the signal, specifically, for the 16-QAM signal, the ACLR is improved from −45.4 dBc to ∼61.6 dBc. The proposed method can reduce the requirement and cost of RF devices such as filters and ensure the performance of the super-heterodyne differential transmitter.