| The RF power amplifier is one of the most important modules in the transmitter for a wireless communication system.The performance of the power amplifier is related to the stability of the communication system.The development of the communication system has raised a higher demand for efficiency,linearization,and miniaturization of RF power amplifiers.RF power amplifier is the most power consuming component in the transmitter.The current research is focused on how to meet the requirement of the power amplifier for high efficiency and high output power back-off for large peak-to-average ratio signal.At the same time,high-rate signal transmission requires broadband modulation signal,moreover bandwidth becomes more and more valuable.The same modulated signal may work in different frequency bands.So on this basis,operators need to build base stations for each frequency band which corresponds to neither the development concept of green and energy-saving wireless communication nor economical efficiency.Therefore,high efficiency multi-band multiplexed RF power amplifier is also a hot research content.As wireless communication technology develops,the requirement of high speed data transmission is becoming a growing concerned.The consumption of transmission bandwidth continues to increase in order to achieve high-speed data transmission,which requires an efficient modulation technique.For example,orthogonal frequency division multiplexing(OFDM)used in the LTE system not only brings efficient spectrum utilization but also a high peak-to-average ratio signal.RF power amplifier has to work at power back-off area where conventional power amplifier cannot meet the high efficiency requirement.Conventional power amplifiers cannot meet high efficiency requirements.Doherty power amplifier as a simple structure can be implemented easily.Because of active load modulation principle Doherty has a theoretical efficiency of 78.5% in the saturation and back-off area at the same time.Based on the above advantages,Doherty has been widely used in communications.Systematically introduces the working principle of carrier and peak power amplifier of Doherty power amplifier and the advantages of asymmetric Doherty.A broadband high power back-off Doherty power amplifier working on 1800-2500 MHz is designed.Under continuous wave excitation,experimental results show the drain efficiency of 50.2%-66.4% at 9dB output back-off power levels.Its saturation output power is between 44.9-45.8dBm.Furthermore a 10MHz-LTE modulated signal is also applied to the fabricated asymmetric Doherty power amplifier After digital predistortion the ACPR is 12 dB lower than before.The ACPR of the DPA achieves lower than-45 dbc.A wideband,high efficiency,high back-off asymmetric Doherty power amplifier is completed which meets the basic needs of communication.A measured 2.6/3.45 GHz high-efficiency power amplifier is realized with the combination of the harmonic control network and the fundamental matching network Under continuous wave excitation,experimental results show the drain efficiencies of 75.2%/67.3% in the center frequency band.The bandwidth for the center frequency is 140 MHz and 120 MHz with the drain efficiency over 60%.The ACPR of the power amplifier achieves lower than-45 dBc with DPD technology.A 2.6/3.45 GHz high-efficiency power amplifier based on harmonic control has been completed. |
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