| Since being put forward in 1992, Software Defined Radio has a big development lasting for over 10 years, and its theory has gradually matured. Restricted by chip manufacture techniques, we can't do digital process to high frequency signals, so the embodiment of Software Defined Radio is Digital Intermediate Frequency. Digital Intermediate Frequency is widely applied in 3G wireless communication systems. 3G systems develop very fast, and there are four standards now, CDMA2000, TD-SCDMA, WCDMA, and WiMAX. The modulation modes of 3G systems are usually QPSK, 16QAM or 64QAM, with high peak-average power ratio, and it puts forward high linearity requirement to semiconductors just like power amplifier in systems, so the linearity techniques are widely applied in 3G systems. Digital Pre-Distortion is one of the linearity techniques of power amplifier in digital field.This text makes a summary of power amplifier linearity techniques, mainly introduces the theory of digital pre-distortion, and puts forward a solution of WiMAX digital intermediate frequency transceiver based on software defined radio which is with digital pre-distortion function, supporting 2×2 MIMO. Considering WiMAX signals have large base band and high frequency, digital-analog conversion, analog-digital conversion and digital pre-distortion chips with high performance on base band processing are chosen. All of chips chosen in this text are widely used in the market, and are produced by mainstream corporations, so they have very good coherence. Experiment data shows that PM7820 has very good digital pre-distortion performance and the solution of digital intermediate transceiver achieves the commercial standard. This text offers use for reference on 3G base station systems design. |
