Microwave Ultra-linear Power Amplifier Research

With the development of wireless communication, especially CDMA format, ultra-linear microwave power amplifier has been paid more and more attention and been a necessary component in wireless systems. The nonlinear influence on multiple carriers signal, such as AM/AM and AM/PM conversion, has been analyzed in this paper. Some common linearization techniques, such as feedback, feed-forward and pre-distortion, have also been introduced and compared, which shows that feed-forward is the preferred linearization approach for application in this paper.It is the main work of this paper to research and develop 3.5GHz power amplifier utilizing feed-forward technology for CRS in 3.5GHz fixed wireless access system. Vector modulators have been used in this paper to vary the phase and amplitude of signals in the in-band spurious cancellation loop of feed-forward power amplifiers (FFPA). In the two-tone test, 3.5GHz FFPA developed in this paper shows more than 35dB improvement in the third-order inter-modulation (IM3), offers approximately -60dBc IM3 output, achieves the expected goal, and meets the communication requirement.