| In recent years, with the rapid development of long range radio frequency identification (RFID) technology at 860 ~ 960MHz (UHF) band, UHF band reader is widely used in automated highway toll collection, parking management, and so on. UHF band reader has two key properties of long distance and good continuity about reading card. As the core component of reader RF system, the performance of power amplifier plays a decisive role to two performances of reader described above. As UHF band reader's own characteristics, it requires the power amplifier system with low gain flatness, high gain, good linearity properties. To satisfy the performance required for the reader, this paper presents the design of RF power amplifier,which has a center frequency of 915MHz, a bandwidth of 26MHz, the output power of 32dBm and gain up to 52dB.The whole power amplifier is comprised of three stages. Pre-stage amplifier adopts the highest linearity design method which plays a key role in increasing the linearity of power amplifier system; Driver stage amplifier contains two internal amplifiers and can realize up to 27dB gain, to lay a solid foundation for the entire amplifier system to achieve high gain of 52dB; Final stage power amplifier uses a balanced amplification structure, this design approach makes the whole amplifier system to achieve ultra-low gain flatness at work band.Firstly, three power amplifiers are strictly in accordance with the steps: device selection, determination of design requirements, simulation and optimization, practical test, to separately design three power amplifiers. Finally, the use of isolator joins three power amplifiers to constitute the entire power amplifier, and make simulation optimization and practical test to the entire power amplifier system , simulation and test results show that this PA fully realize the design goal and can be used in RFID system to improve the performance of the system. |
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