无线通讯用Doherty功率放大器的研究

发布时间：2018-04-08 11:45

本文选题：无线通信　切入点：Doherty功率放大器　出处：《杭州电子科技大学》2017年硕士论文

【摘要】：自从上世纪80年代移动手机的出现以来,无线通信技术经历了前所未有的飞速发展。直到今天,它已经主导了人们的生活和交流方式。随着无线通信行业的高速发展,人们对大容量信息传输的需求也在逐渐增加,因而,对无线通信技术的要求也越来越严苛。功率放大器作为无线通信系统中最耗能的组件,其效率对整个通信网的能耗都至关重要。同时,受节能环保生活方式的影响,我们更应致力于提高其效率。由于人们对高信息容量传输的需求日益增加,各种复杂的调制方案得到了广泛应用。因此,当今的无线通信中的信号通常具有很高的峰值-平均功率比(峰均比)。传统的功率放大器,在处理这些信号的时候很难保证在回退区和饱和区同时达到高效。因此以Doherty功率放大器为代表的功率放大器成为了当今基站功放的主流结构。该结构通常由两路偏置点不同的子功率放大器组成,即峰值功率放大器(主功放)和载波功率放大器(副功放)。其工作原理是随着输入信号的增加,两者依次导通,在主功放达到饱和的时候,副功放才开始工作。这样就可以保证整体电路在回退点和饱和点都能够高效的放大信号。本文将主要对Doherty这种结构进行研究。虽然传统的Doherty功率放大器具有突出的效率优势,但是存在工作带宽较窄的缺陷。这主要是因为其负载调制网络是由两条四分之一波长线组成的,其阻抗随工作频率的变化而变化,这一特点大大限制了整体电路的带宽。本文中将会提出一种新型的负载调制网络,对传统的结构进行优化,极大的改善阻抗随频率的漂移效应,从而保持阻抗稳定的同时提升Doherty功放的整体效率。另外,随着人们对大容量信息的需求越来越大,无线通信系统中的调制信号也越来越复杂,峰均比前所未有的高。所以我们希望Doherty功率放大器能够在更大的功率范围内都保持高效。相比于传统两路Doherty,新加一路峰值功率放大器的三路Doherty,可以完成这个目标。三路Doherty的负载调制网络同样存在上面提到的阻抗漂移问题。因此,同样需要对其负载调制网络进行优化以拓宽其带宽。本论文在传统的负载调制网络中新增一条并联的四分之一波长短路线,这种新型的负载调制网络可有效限制阻抗随频率的漂移,并设计了一个三路Doherty功率放大器来验证其有效性,通过对实物电路的加工测试,最终得到,在2-2.6GHz的工作带宽内,8dB回退点的漏极效率在40%以上,饱和点的效率在53%以上,在2.6GHz处可达76%,工作带宽内的饱和输出功率都在43.6dBm以上,在2.2GHz处可达45.4dBm。
[Abstract]:Since the emergence of mobile phones in the 1980s, wireless communication technology has experienced unprecedented rapid development.To this day, it has dominated the way people live and communicate.With the rapid development of wireless communication industry, the demand for mass information transmission is gradually increasing, so the requirements of wireless communication technology are becoming more and more stringent.Power amplifier is the most energy-consuming component in wireless communication system. Its efficiency is very important to the energy consumption of the whole communication network.At the same time, under the influence of energy conservation and environmental protection lifestyle, we should focus on improving its efficiency.Due to the increasing demand for high information capacity transmission, a variety of complex modulation schemes have been widely used.Therefore, in today's wireless communications, signals usually have a high peak-to-average power ratio (PAPR).It is difficult for traditional power amplifiers to process these signals with high efficiency in both the fallback and saturation regions.Therefore, the power amplifier, represented by Doherty power amplifier, has become the mainstream structure of base station power amplifier.This structure usually consists of two sub-power amplifiers with different bias points, namely, peak power amplifier (main power amplifier) and carrier power amplifier (secondary power amplifier).Its working principle is that with the increase of input signal, both of them are switched on in turn. When the main power amplifier reaches saturation, the secondary power amplifier begins to work.This ensures that the whole circuit can amplify the signal efficiently at both the back-off point and the saturation point.This paper will mainly study the structure of Doherty.Although the traditional Doherty power amplifier has the outstanding efficiency advantage, it has the limitation of narrow working bandwidth.This is mainly due to the fact that the load modulation network is composed of two 1/4 wave long lines, and its impedance varies with the operating frequency, which greatly limits the bandwidth of the whole circuit.In this paper, a new type of load modulation network is proposed, which optimizes the traditional structure and greatly improves the drift effect of impedance with frequency, thus maintaining the stability of impedance and improving the overall efficiency of Doherty power amplifier.In addition, with the increasing demand for large capacity information, modulation signals in wireless communication systems are becoming more and more complex, the peak to average ratio is higher than ever before.So we want the Doherty power amplifier to remain efficient in a larger power range.Compared with the traditional two-channel Doherty, a new three-way Doherty with a peak power amplifier can achieve this goal.The impedance drift problem mentioned above also exists in the three-channel Doherty load modulation network.Therefore, it is also necessary to optimize the load modulation network to broaden its bandwidth.In this paper, a parallel 1/4 wavelength short path is added to the traditional load modulation network. This novel load modulation network can effectively limit the drift of impedance with frequency.At 2.6GHz, the saturation output power is above 43.6dBm and 45.4 dBm. at 2.2GHz.
【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】：2017
【分类号】：TN722.75

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