【作者】 杨凡；

【导师】 曾孝平；

【作者基本信息】 重庆大学 ， 信号与信息系统， 2010， 硕士

【摘要】 射频功率放大器作为发射机的核心部件,其性能制约了整个通信系统的性能,特别是近年来,无线通信系统向着大容量、多载波、多电平、和高峰均比的方向发展,在此背景下,线性调制技术被广泛的应用,由于这些线性调制技术具有非恒定包络的特点,当调制信号通过射频功率放大器后将产生交调失真,导致已调矢量信号的幅度和相位出现偏差,同时导致频谱扩展,邻道信号受干扰,误码率恶化等。因此,线性射频功率放大器成为研究的热点。论文围绕L波段线性功率放大器的设计展开,首先分析了功率放大器的基本原理和线性化技术,然后设计了在1.90GHz—2.0GHz频段上基于RF预失真方案的3级功率放大器,并进行了理论分析和性能仿真,仿真测试结果表明该功率放大器具有很好的线性度和较高的输出功率。其中,主要研究内容和有创新的工作表现在以下几个方面:①通过对功率放大器的理论分析,针对设计需求中功率放大器输出高增益大功率的要求,确定了功率放大器3级级联的设计方案。②针对功率放大器大信号S参数无法获得的难点,根据各级功率放大器在电路中的作用和工作状态不同,分别用小信号S参数法设计了前置级和驱动级功率放大器,用负载牵引法设计了末级功率放大器。级联后的功率放大器的输出功率34.143dBm、增益大于30dB,带内增益平坦度小于1dB,均高于设计要求。③为了提高功率放大器的线性度,通过对比各种线性化电路的设计,确定了基于立方律的RF预失真的线性化方案。本文对立方律预失真器进行了改进,采用180°正交电桥替代T型电阻网络并引入平衡电阻网络来修正反向并联二极管对的不对称特性,从而改善了预失真器的性能。另外还设计了3dBWilkinson功率分配/合成器、衰减器和模拟移相器等组件,仿真测试表明,在功率放大器输出35dBm的功率时,加入预失真线性化电路后三阶交调失真(IMD3)小于-60dBc,较预失真前改善了27dBc。该方案有效的改善了功率放大器的线性度。更多还原

【Abstract】 RF power amplifiers are the hard-core of the transmitter. The performance of the power amplifiers has already restricted the capability of the whole communication system. Especially in recent years, wireless telecommunication system is developing towards adding channel capability, multi-carrier, linear modulation, multi-level, widening the frequency and high PAR. Under the background, linear modulation techniques are widely used. Because linear modulated techniques have the characteristic of varying envelop, modulated signals with varying envelop will generate intermodulation distortion. The distortion results in errors in the magnitude and the phase of the modulated vector signal, enlarging the spectrum, disturbing the adjacent-channel, worsening the error-code-rate and so on. Thereby, linear RF power amplifier has been a hot spot of research.The dissertation discusses the design of L-band linear power amplifier. First of all, it analyses the principle of power amplifier and linearization techniques. Secondly, the RF predistortion linear three stages power amplifier that work in the 1.90GHz—2.0GHz band is designed. The amplifier is simulated to test its performance. The simulation results demonstrate that the amplifier has a good linearity and high output power.The main contents and innovation of the dissertation are as follow:①Through analyzing the theory of power amplifier, the design scheme of three stages amplifiers cascade is confirmed, in order to meet high output power and great gain of the power amplifier.②Because of unavailable large signal S parameters and different operating state& performance among the amplifiers, pre-stage and driver stage amplifiers are designed by the method of small signal S parameters, while last stage amplifier by load-pull design method. The cascade amplifier has 34.143dBm output power, greater than 30dB gain, and less than 1dB gain flatness. All of these performances are superior to design index.③In order to improve the linearity of the amplifier, the plan based on the cubic law predistortion is confirmed by comparing lots of linearization techniques. And the innovative improve of the cubic law predistorter include: 1) Using the 1800 quadrature coupler instead of T-type resistance network. 2) Inserting balance resistance network to correct the asymmetry of the antiparallel diode pair. It great improves the predistorter performances. At the same time, 3dB Wilkinson power dividers/combiners, attenuator and analog phase shifter are also designed. The result shows that, when the output power of the amplifier is 35dBm, the IMD3 can be less than -60dBc by the effect of the predistortion system. The predistortion system can improve IM3 27dBc. It improves the power amplifier linearity effectively.更多还原