| Nowadays3G system and4G system are working simultaneously almost all over the world and it will probably come true that4G system and5G system will be also utilized in the near future, which makes the mobile operators operate several different systems at the same time. As we all know each system needs at least one power amplifier (PA), and it will definitely increase power consumption as well as the volume of the base station if some PAs are working together at the same time. In addition, due to the decrease of the spectrum resource, some linear modulation schemes(such as OFDM、M-QAM, etc.) with high spectrum utilization efficiency are widely used. And the signal under these modulation schemes has large amplitude fluctuation and high PAR, which pose stringent demands to the linearity of power amplifiers. Therefore, the research on high-efficiency and concurrent dual-band RF power amplifiers has become a hot topic.The major contribution includes:(1) Do some researches on the basic theory of the RF power amplifier and analyze the operating principle of the dual-band symmetrical Doherty power amplifier by using the load-pull theory.(2) Study and calculate some dual-band components, including T-network、π-network and a three-section dual-band transformer for frequency-dependent complex load impedance. Besides that, propose a new structure for dual-band offset-lines with the most simplified structure and present a new method to debug the dual-band power amplifier.(3) Design and implement a dual-band Doherty power amplifier which works under0.90GHz and2.14GHz simultaneously and whose peak power output are43.7dBm、43.9dBm with the drain efficiencies of 51.2%、43.5%at6.5dB output power back-off, respectively. |
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