S波段Doherty高效率功率放大器的研究

【作者】 周海涛；

【导师】 羊恺；

【作者基本信息】 电子科技大学 ， 电路与系统， 2010， 硕士

【摘要】 现代无线通信系统多采用的宽带码分多址(WCDMA)、CDMA-2000、正交频分复用(OFDM)等调制技术多为高速率和大范围变化且带有较高峰均比(PAR)的调制信号。这就对现代移动通信中的基站高功率放大器提出了高效率的要求,特别是在功率回退位置的高效率。但是,通常的功率放大器随着功率回退的加深,效率会迅速恶化。?为了解决这个问题,本文采用了Doherty功率放大器技术。另外,为了在功率回退更深的范围内提高功率放大器的效率,本文采用基于射频阻抗匹配实现的非对称Doherty功率放大器。在理论上,本文介绍了Doherty功率放大器的三种工作状态以及对应的效率计算,同时分析了Doherty功率放大器能够在功率回退点达到高效率的原因,并且较为详细的介绍了非对称放大器设计中采用全功率匹配技术和传输对消线阻抗设计。在实现上,本文对系统指标进行了简单分析,给出了选管依据,以输出功率分别为30W和50W的N沟道LDMOS管实现非对称结构,随后从单管放大器设计入手,对等分和非对称Doherty功率放大器进行仿真设计,其中特别针对全功率匹配和输出匹配设计给出较为详细的设计过程,最后制作了两个单管放大器和Doherty功率放大器系统的实物。本文给出了功率放大器的测试方案。最后的测试结果基本达到设计指标。其中,Doherty功率放大器在输出为40.5dBm时(功率回退8.5dB),达到效率大于30%。更多还原

【Abstract】 Modern communication systems adopt different modulation technique such as WCDMA, CDMA-2000 and OFDM, so signals in the communication system are mostly high-rate and high dynamic range with the high peak-to-average ratio (PAR). To satisfy those requirements, base station power amplifier should be equipped with high efficiency, especially high efficiency at the point of back-off power. Unfortunately, ascribing to the deeper back-off power, the efficiency of common power amplifier would drop off quickly.To solve this problem, this dissertation adopts Doherty power amplifier technology. In addition, to enhance the efficiency at the deeper back-off power, uneven Doherty power amplifier basing on RF impedance-match technology is employed. On the theory, this dissertation introduces three different work conditions and its corresponding efficiency of Doherty, and then analyzes the reason that Doherty power amplifier can get high efficiency at the back-off point, and detailedly introduce all power-match technology and the method of calculating impedance. On the implementation, the index of system is analyzed in this dissertation, and the basis for choice on the chips is provided, and uneven Doherty is designed by two different LDMOS chips with 30W and 50W output power respectively. Then, from the design of single-chip amplifier, this dissertation introduce the progress of even and uneven Doherty power amplifier, especially the simulation of all power-matched technology and method of computing matched impedance. Finally, make two different single-chip amplifier and Doherty power amplifier system.This dissertation provides the plan of testing power amplifier. The result of test basically matches the design index, including power added efficiency (PAE) of Doherty power amplifier is beyond 30% at the point of 8.5dB back-off power.更多还原