| RF power amplifier is an important component of the wireless transmitter, power amplifier of multi-carrier radio transmission systems requires high linearity in addition to high gain and sufficient bandwidth, so research on the technology of power amplifier linearization has become a hot spot in and abroad recently.This paper first describes the causes and main form of expression of non-linear power amplifier, reviews several common linearization techniques. A discussion around the feed-forward techniques for feed-forward amplifier gain and efficiency of the system is then analyzed in detail. According to the actual needs of multi-carrier radio transmitter, main power amplifier and protection circuits of feed-forward system have been designed and realized. The coaxial transmission line transformers integrated with high frequency compensation technique achieve an efficient impedance matching, and gain test results show that performance meets the project targets. Protection circuit could detect the current, temperature and standing wave to ensure the safety and improve the stability of the circuit. Detail analysis and simulations for the auxiliary amplifier, power splitter and directional coupler, variable attenuator and phase shifter have been made. Finally, specific indicators of each module and the overall implementation of the feed-forward amplifier system have been determined, ADS simulation and optimization was also applied to make the performance meet actual needs of broadband multi-carrier linear power amplifier. The two-tone harmonic simulation results indicate that third-order intermodulation suppression of feed-forward system output is up to -75dBc.In addition, this paper has derived the convert model used in S-parameters measurement according to the complex characteristic impedance of generalized transmission line theory. On the basis of this convert model, a S-parameter conversion software has been developed. This software makes up for the shortages of vector network analyzer (VNA) when measuring S-parameters of matching network by converting S-parameters under the fixed condition into characteristic impedance S-parameter under arbitrary conditions, with high practical value. |
PDF Full Text Request