| PA is one of the most important modules of communication system, with the development of the wireless communication technology, the power amplifier's performances are increasingly demanded. In modern wireless communication system, because of wireless bandwidth, in order to effectively improve the efficiency of spectrum, a variety of new techniques require transporting data as much as possible, using QAM, QPSK, DPSK modulation, etc. As these methods often require large dynamic input signal range, so the linearity of power amplifier is highly required . Most of the modern modulation techniques are jin use of a non-constant envelope modulation, which has a large difference between peak and average. In order to meet the linearity requirements, it often uses a certain degree of power back-off approach to achieve the increase of the linearity, however, with the power back-off, amplifier efficiency, such as the power-added efficiency will be greatly reduced. At the same time, the power amplifier is a high-power device in the actual application, in order to extend the using time of battery-powered communication system and improve the reliability of the device, the efficiency of the amplifier is also highly demanded, higher power amplifier efficiency not only can save electricity, save power and other facilities of the investment, but also can simplify the production process, reduce the cooling requirements of machine to increase the stability of the equipment, and get a better network performance. In this paper, we use the Doherty amplifier technology, which is one of few amplification framework that can ensure high-efficiency in a large-signal dynamic range ,and also in the foreseeable future, Doherty amplifier technology is the only way to provide sufficient bandwidth for high-efficiency amplifier architecture.In this paper, we comparatively analyze a variety of high-efficiency amplifier technology as well as characteristic indicators of the power amplifier based on referencing a large number of data of power amplifiers. In view of current development in some cases, we study the Doherty amplifier theory in-depth. We select FREESCALE Semiconductor LDMOS tube MRF7P20040H as Doherty tube, through the ADS simulation as the theoretical basis and analysis of the characteristics of the main and auxiliary power amplifiers on the system to complete the output for the 7W's Doherty power amplifier's design in TD-SCDMA.Now high-power amplifier used in base station is usually used with digital pre-distortion (DPD), the combination of Doherty amplifier and DPD will be the future trend of development of high-power amplifier. Therefore, we introduce the basic principles and the basic structure of the DPD in the paper and briefly describe the problems between them when they are combined with each other. Finally, we debug and test the Doherty amplifier design, and introduce the questions in debugging and testing process, and finally give the test results. Through debugging and testing on Doherty power amplifier, we can get much valuable experience in for future for Doherty's research. |
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