The Design And Implementation Of A High Efficient Power Based On Analog Predistortion

With the rapid development of science and technology, the nervous phenomenon of wireless bandwidth is growing seriously. It has prompted the subsystem of modern wireless communication system base station toward to the direction of high bandwidth, high efficiency and rapid rate. In the subsystem of wireless communication system, the RF power amplifier which is the transmitter terminal converts dc power to RF signal. So it is the largest energy consumption device in the whole system.The power amplifier largely determines the base station power consumption、output power and transmitter linearity.The main purpose of this thesis is to improve the efficiency and linearity of power amplifier and Doherty technology and linearization techniques are studied and analyzed respectively. The classical two-stage Doherty structure is used to improve the efficiency of power amplifier and the predistortion technology is used to improve the power amplifier linearity in this paper.The MRF6V3090N chip which is produced by Freescale Company is used to design the Doherty power amplifier. The main task includes:(1) The Doherty power amplifier theory is studied and the Doherty power amplifier design features have been analyzed, specifically, the impedance transformation and offset-line theories have been analyzed.(2) According to the theory of active load pull theory, a Doherty power amplifier with400MHz center frequency,30MHz bandwidth and the efficiency is above40%at6dB back-off has been designed.The analog predistorter has been designed by SC1894chip which produced by Scintera company and the external circuit is built by according to chip manual. A part of the output signal coupled by coupler is feedback to SC1894and it can achieve the best performance of analog predistorter. And the coupler is made by parallel microstrip lines.