| With the development of wireless communication system updates more and more quickly, as well as in green low-power wireless communication initiative, the RF power amplifier in the energy dissipation system has become a bit of engineers who are most concerned about. At present, the research on high efficiency RF power amplifier is in full swing. At the same time, the update of wireless communication technology is accompanied by various wireless communication standards. This standard includes the change of signal modulation mode and the same communication system working in a variety of frequency bands, which puts forward strict requirements for the linearity of the power amplifier and the support of multi band operation. Now, RF power amplifier design is around the "high efficiency","multi-band", "high linearity" direction.In view of the current demand for the performance of RF power amplifier, the traditional AB or push-pull power amplifier are not up to the requirements in efficiency and linearity. Especially in China's TD-LTE standard with independent property rights,the signal using Orthogonal Frequency Division Multiplexing (OFDM) modulation mode. Because OFDM multi-carrier modulation technique make the signal to produce a high Peak-to-Average Power Ratio(PAPR),the power amplifier must work in a certain amount of power back down, making the work efficiency to reduce. In view of these needs, Doherty amplifier has high efficiency over a wide power range, which is the base station power amplifier design commonly used in the structure.In order to realize the high efficiency of the power amplifier, the dissertation first completed simulation design and practicality test for Doherty power amplifie.Compared with the Class AB power amplifier in the power back off 6dB(44.7dBm).It's efficiency is maintained at 41%, increased 15 percentage points, which achieved high efficiency work, and other design indexes of the power amplifier satisfied the design requirements.Due to the high PAPR of the signal in the TD-LTE system, the power back off need to be reach about 8dB. Therefore, the dissertation improves the traditional Doherty power amplifier for the Asymmetric Doherty power amplifier. Compared with the traditional Doherty power amplifier in the power back off 8dB (42dBm). It's efficiency is maintained at 38%,increased 6 percentage points, and enhanced the efficiency for high power back off.Finally, this dissertation studied the dual-band expansion of power amplifiers.Based on the analysis of the dual-band operation of the T-type microstrip line and the bilateral microstrip line, which is applied to the input and output matching network for the power amplifier.The paper achieved the power amplifier at the frequency of 0.9 GHz and 2.4 GHz on the multi band work.This dissertation introduced the design thought method of Doherty RF power amplifier, and completed the practicality test, which provides valuable experience for the follow-up research and explicit the improvement direction. |
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