基于宽带包络跟踪技术的Doherty射频功率放大器研究与实现

发布时间：2018-06-14 19:42

本文选题：高效率 + 包络跟踪　；参考：《北京邮电大学》2015年硕士论文

【摘要】：现代无线通信系统多采用非恒包络调制技术以提高数据传输速率,例如OFDM调制,这使得信号的峰均比较高。传统功放在放大高峰均比信号时,平均效率较低。Doherty技术和包络跟踪技术可以有效地提高功放的平均效率,是目前国内外研究的热门功放效率提升技术。将这两种技术结合,可以使得功放更高效地放大高峰均比信号。本文主要研究了应用于大功率Doherty射频功放的包络跟踪技术,设计和实现了一款包络跟踪Doherty功率放大器。本文主要工作包括以下几个方面： 1.高效、宽带包络放大器的设计是包络跟踪技术的重点和难点。当今LTE信号的包络信号带宽可达20MHz,要高效地放大带宽如此高的包络信号对于包络放大器的设计是一大挑战,传统的线性放大器和开关变换器无法兼顾效率和带宽这两个指标。本文设计的包络放大器采用了基于线性部分和开关部分并联的混合型结构,以满足带宽和效率的要求,并通过对线性部分输出级电路进行改进,进一步提升了包络放大器的效率。测试结果表明,本文设计的包络放大器最大输出电压28V,带宽20MHz,单音信号测试峰值效率76.9%。 2.本文采用了对Doherty功放主功放的漏极电压进行包络跟踪的跟踪方法,拓宽了传统两路对称Doherty功放的功率回退范围,提升了Doherty功放放大高峰均比信号时的平均效率。本文对包络跟踪后Doherty功放的效率进行了理论推导,并使用ADS仿真软件对包络跟踪Doherty功放进行了仿真。仿真结果显示应用包络跟踪技术后,Doherty功放在输出功率回退8dB处,效率提升10%。 3.最后本文在仿真的基础上完成了包络跟踪Doherty功放的硬件实现,并进行了单音信号和带宽信号测试。该Doherty功放峰值输出功率43dBm,回退6dB处效率43.7%。使用单音信号测试结果显示,应用包络跟踪技术后,Doherty功放在输出功率回退8dB处,效率提升5%。使用带宽20MHz、PAPR10.18dB的LTE信号测试结果显示,应用包络跟踪技术后,Doherty功放在平均输出功率34.2dBm处,效率提升6.53%。
[Abstract]:In modern wireless communication systems, non-constant envelope modulation technology is used to improve the data transmission rate, such as OFDM modulation, which makes the peak of the signal higher. When the traditional amplifier amplifies the peak to average signal, the average efficiency is low. Doherty technology and envelope tracking technology can effectively improve the average efficiency of the amplifier. It is a hot technology to improve the efficiency of power amplifier at home and abroad. By combining these two techniques, the amplifier can amplify the peak-to-average signal more efficiently. In this paper, the envelope tracking technology for high power Doherty RF power amplifier is studied, and an envelope tracking Doherty power amplifier is designed and implemented. The main work of this paper includes the following aspects: 1. The design of high efficiency and wide band envelop amplifier is the focus and difficulty of envelope tracking technology. Nowadays, the envelope signal bandwidth of LTE signal can reach 20MHz. To amplify the envelope signal with such high bandwidth efficiently is a great challenge to the design of the envelope amplifier. The traditional linear amplifier and switching converter can not take both efficiency and bandwidth into account. The envelope amplifier designed in this paper adopts a hybrid structure based on linear part and switch part in parallel to meet the requirements of bandwidth and efficiency, and improves the output stage circuit of linear part. The efficiency of the envelop amplifier is further improved. The test results show that the designed envelope amplifier has a maximum output voltage of 28V, a bandwidth of 20MHz and a peak efficiency of 76.92. In this paper, the envelope tracking method of the drain voltage of the Doherty power amplifier is adopted, which widens the power back range of the traditional two-channel symmetrical Doherty power amplifier and improves the average efficiency of the amplification peak to average ratio signal of the Doherty amplifier. In this paper, the efficiency of Doherty power amplifier after envelope tracking is deduced theoretically, and the envelope tracking Doherty power amplifier is simulated by ads simulation software. The simulation results show that with the application of envelope tracking technology, the Doherty power amplifier is applied to the output power back 8 dB, and the efficiency is increased by 10. 3%. Finally, the hardware implementation of envelope tracking Doherty power amplifier is completed on the basis of simulation, and the single tone signal and bandwidth signal are tested. The peak output power of the Doherty power amplifier is 43dBm, and the efficiency is 43.7 at 6dB. The results of single-tone signal test show that the envelope tracking technique can be used to amplify the output power at 8 dB, and the efficiency can be improved by 5 dB. The test results of LTE signal with a bandwidth of 20 MHz PAPR 10.18 dB show that the average output power is 34.2dBm and the efficiency is increased 6.53 when the envelope tracking technique is applied.
【学位授予单位】：北京邮电大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN722.75

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