应用于多模多频的宽带高效率功率放大器设计

发布时间：2018-09-11 09:03

【摘要】：随着第三代(3G)移动通信技术的普及应用和第四代(4G)移动通信趋于成熟的发展,现代移动通信系统呈现出多种通信制式并存、多个通信频段并列的局面。多模式、多频段系统操作不可避免地成为了未来无线移动通信系统的发展趋势。各种通信制式均朝着高信号峰均比(Peak-to-Average Power Ratios,以下简称PAPR)、多载波、大信号容量的方向发展。在现如今倡导绿色、节能、环保的时代背景下,如何把不同工作模式的调制系统在同一工作平台上并存实现越来越引起人们的关注,这些都对无线通信系统中发挥着重要作用的宽带功率放大器提出了更高的要求。作为无线通信系统发射机末端的核心模块,功率放大器的性能直接影响了整个通信系统的信号传输质量。因此,在保持高信号峰均比和高效率工作的同时,进一步扩大功率放大器的工作带宽具有非常重要的现实意义。本文的主要工作集中在宽带高效率功率放大器的研究和设计上。论文首先介绍了功率放大器的基础理论知识,包括功率放大器的分类、性能参数指标,以及功放设计中核心的负载线理论及负载牵引技术;接着介绍了几种常用的宽带功放实现技术和效率提升技术,着重对功率放大器饱和输出及功率回退两种不同情况下的效率提升技术进行对比研究,为后文宽带高效率功放的实现提供理论依据;然后对Doherty功率放大器的基本原理以及其核心的有源负载牵引理论进行了研究,对Doherty功放不同工作状态下负载阻抗的动态变化过程和效率特性进行分析,并简单介绍了几种新型的Doherty功放结构。基于前述功放基础理论以及一些拓展带宽、提升效率的技术方法,本文采用一种简单实用的宽带直流偏置结构,并利用源/负载牵引仿真确定电路在整个工作频段内的最优阻抗趋势并绘制出阻抗趋势图,然后选取简单的匹配结构,利用Smith圆图轨迹法设计出匹配网络,实现了宽带高效率功率放大器的设计,方法简便,电路结构简单。接着以宽带高效率单级功放为基础,选取合适的Doherty功放结构,并提出一种新型的低输出阻抗匹配方法,结合宽带匹配网络和宽带阻抗变换网络实现了宽带反向Doherty功放的设计,方法简单。按照上述设计方法,首先针对低功率级宽带高效率功率放大器的应用完成设计。第一步仿真并实现了10W宽带高效率功率放大器,测试结果显示,在工作频段1.8-2.7GHz内,电路的饱和输出功率在42-42.5dBm之间,饱和状态下功率附加效率在56%-67.8%之间,输出功率方面的性能优势明显。第二步基于上述电路,设计并实现了工作在1.8-2.7GHz的20W宽带反向Doherty功放,测试结果显示,在连续波信号下饱和输出功率达到43.2-45.1dBm,在功率回退6.7-8.6dB(Pout=36.5dBm)时,电路的漏极效率在41.5-45.3%之间。用WCDMA信号驱动该功率放大器,当Pout=36.5dBm时,电路的漏极效率在45.3-48.6%之间,在信号频偏5MHz的情况下,ACPR(Adjacent Channel Power Ratio,相邻信道功率比)的值均小于-27.4dBc,在2.1GHz处甚至达到了-40.3dBc。据作者所知,该电路的工作带宽在现有的文章报道中是最宽的。其次,针对高功率级宽带高效率功率放大器的应用完成设计。第一步完成了100W宽带高效率功放的仿真设计及实物测试,测试结果显示,在工作频段1.8-2.7GHz内,除了2.7GHz的输出功率较差外(Psat=47.5dBm),其他频段内电路的饱和输出功率在49.3-50.5dBm之间,整个频段饱和输出下的功率附加效率在55.3%-65.7%之间。第二步基于上述电路,设计并实现了工作在1.8-2.7GHz的200W宽带反向Doherty功放,测试结果显示,在整个工作频段内,电路的P-3输出功率在47.5-52.93dBm之间,各频点功率回退至Pout=46dBm时,电路的漏极效率在34.2%-45.9%之间。本文对于宽带高效率功率放大器以及宽带Doherty功率放大器的设计方法作了较为全面的分析总结,基于GaN HEMT功率管设计了工作在1.8-2.7GHz的10W宽带高效率功率放大器、20W宽带Doherty功率放大器和100W宽带高效率功率放大器、200W宽带Doherty功率放大器,为现代移动通信提供了现实的借鉴意义。
[Abstract]:With the popularization and application of the third generation (3G) mobile communication technology and the mature development of the fourth generation (4G) mobile communication, the modern mobile communication system presents the situation of coexistence of multiple communication modes and parallelism of multiple communication bands. Nowadays, under the background of advocating green, energy-saving and environmental protection, people pay more and more attention to how to realize the coexistence of modulation systems with different working modes on the same working platform. As the core module of the transmitter terminal of the wireless communication system, the performance of the power amplifier directly affects the signal transmission quality of the whole communication system. The main work of this paper focuses on the research and design of broadband and high efficiency power amplifiers. Firstly, the basic theoretical knowledge of power amplifiers is introduced, including the classification of power amplifiers, performance parameters, and the core of power amplifier design. Load line theory and load traction technology; then introduces several commonly used broadband power amplifier implementation technology and efficiency enhancement technology, focusing on the power amplifier saturated output and power back two different cases of efficiency enhancement technology comparative study, for the future realization of broadband high-efficiency power amplifier provides a theoretical basis; and then Doherty. The basic principle of power amplifier and its core active load traction theory are studied. The dynamic change process and efficiency characteristics of load impedance under different working conditions of Doherty power amplifier are analyzed. Several new structures of Doherty power amplifier are briefly introduced. In this paper, a simple and practical wide-band DC bias structure is adopted, and the optimal impedance trend of the circuit in the whole working frequency band is determined by the source/load traction simulation, and the impedance trend diagram is drawn. Then the simple matching structure is selected, and the matching network is designed by the Smith circle diagram trajectory method. The wide-band high performance is achieved. The design of efficiency power amplifier is simple and the circuit structure is simple. Then based on broadband high efficiency single-stage power amplifier, a suitable structure of Doherty power amplifier is selected, and a new method of low output impedance matching is proposed. The first step is to simulate and implement a 10W broadband high-efficiency power amplifier. The test results show that the saturated output power of the circuit is between 42-42.5dBm in the operating frequency range of 1.8-2.7GHz, and the additional power efficiency is between 42-42.5dBm in the saturated state. The second step is to design and implement a 20W broadband reverse Doherty power amplifier operating from 1.8 GHz to 2.7 GHz. The test results show that the saturated output power reaches 43.2-45.1 dBm under CW signal and the drain efficiency of the circuit is between 6.7 and 8.6 dB (Pout = 36.5 dBm) when the power falls back. 41.5-45.3%. Using WCDMA signal to drive the power amplifier, the drain efficiency of the circuit is between 45.3 and 48.6% when Pout = 36.5 dBm, and the value of ACPR (Adjacent Channel Power Ratio) is less than - 27.4 dBc when the signal frequency offset is 5 MHz, even up to - 40.3 dBc at 2.1 GHz. The bandwidth is the widest in the existing papers. Secondly, the design is completed for the application of high-power broadband high-efficiency power amplifier. In the first step, the 100W broadband high-efficiency power amplifier is designed and tested. The test results show that the output power of the amplifier is poor except for 2.7GHz (Psat = 47.5dBm) in the operating frequency range of 1.8-2.7GHz. The second step is to design and implement a 200 W broadband reverse Doherty power amplifier operating at 1.8-2.7 GHz. The test results show that the P-3 output power is between 49.3-50.5 dBm and 55.3-65.7% in the whole frequency band. Between 47.5 and 52.93 dBm, the drain efficiency of the circuit is between 34.2% and 45.9% when the power of each frequency point falls back to Pout=46 dBm. The design methods of broadband high-efficiency power amplifier and broadband Doherty power amplifier are analyzed and summarized in this paper. A 10W broadband high-efficiency power amplifier is designed based on GaN HEMT power transistor operating at 1.8-2.7 GHz. Power amplifier, 20W broadband Doherty power amplifier, 100W broadband high efficiency power amplifier and 200W broadband Doherty power amplifier provide practical reference for modern mobile communication.
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN722.75

【二级参考文献】