S波段高效低失真功率放大技术研究

发布时间：2019-02-19 11:35

【摘要】：由于目前无线通信领域飞速发展,使得频谱资源越来越拥挤,而放大器作为通信系统中最重要的组成部分,拥挤的频谱将会对信号的传输产生严重的干扰,因此需要线性化处理,但具有高线性度的放大器,其效率一般来说比较低。为了同时解决线性度以及效率这一对矛盾体,本文从以下几个方面对其进行了讨论与分析。首先,对放大器的线性化措施以及提高效率的方法的进行了简单介绍,并对它们的优缺点进行了讨论,同时也简述了目前高效低失真技术的研究现状。随后对放大器的工作模式进行了介绍,并分析了放大器的非线性特性,主要包括非线性失真以及非线性指标等,以及放大器的记忆效应对放大器的产生的影响。最后进行了方案论证,确定本课题采用带外终端法并结合动态偏置来实现放大器的高效低失真。本文分析了三阶互调产生的原因,并得到了三阶互调幅值的表达式,讨论了各参量对于三阶互调的影响,得到当电路以及偏置满足一定条件时,放大器的三阶互调会在较高输入功率时产生一个极小点,称之为IMD sweet spot,即互调失真最优点。由于是在较高功率输入时得到的,因此其效率比较高,并且这个最小点的值一般很小,所以其线性度也比较高。综合上述特点,设置一定的线性度条件,在某一给定输入功率下,对其偏置进行调节,就能实现高效低失真的功率放大。本文利用BFP620硅锗型放大器来对方案进行验证,中心频率为2.4GHz。为了获得IMD sweet spot,对电路结构进行了处理,在放大器输入输出端加载基带频率短路枝节,并在放大器源端以及负载端分别加载二次谐波短路枝节,以及同时加载二次谐波短路枝节,通过调节偏置以及输入功率,可以得到满足三阶互调要求的最大效率以及对应的集电极偏压和输入功率。最后总结了各种情况对于放大器效率和线性度的改善程度。结果表明,当设定放大器的三阶互调为?45dBc时,其最大效率可以达到40%左右。实验结果还表明,在满足三阶互调要求时,若要获得更高效率,则在中心频率的回波损耗就要更小。
[Abstract]:Because of the rapid development of the wireless communication field, the spectrum resources are becoming more and more crowded. As the most important part of the communication system, the congested spectrum will cause serious interference to the signal transmission. Therefore, linearization is needed, but the amplifier with high linearity is generally inefficient. In order to solve the contradiction of linearity and efficiency simultaneously, this paper discusses and analyzes it from the following aspects. Firstly, the linearization measures and the methods to improve the efficiency of the amplifier are briefly introduced, and their advantages and disadvantages are discussed. At the same time, the current research status of the high efficiency and low distortion technology is also briefly described. Then the working mode of the amplifier is introduced, and the nonlinear characteristics of the amplifier are analyzed, including nonlinear distortion and nonlinear index, and the influence of the memory effect of the amplifier on the amplifier. Finally, the scheme is demonstrated, and the method of out-of-band terminal and dynamic bias are used to realize the high efficiency and low distortion of the amplifier. In this paper, the reason of the third order Intermodulation is analyzed, and the expression of the third order Intermodulation value is obtained. The influence of each parameter on the third order Intermodulation is discussed. The third order Intermodulation of the amplifier can produce a minimum point when the input power is higher, which is called IMD sweet spot, which is the best advantage of Intermodulation distortion. Because it is obtained at higher power input, its efficiency is relatively high, and the value of this minimum point is usually very small, so its linearity is also relatively high. Based on the above characteristics, a certain linearity condition is set, and the bias can be adjusted under a given input power, and the power amplification with high efficiency and low distortion can be realized. In this paper, BFP620 Si-germanium amplifier is used to verify the scheme, and the center frequency is 2.4 GHz. In order to obtain the IMD sweet spot, circuit structure, the baseband frequency short circuit segment is loaded at the input and output end of the amplifier, and the second harmonic short circuit section is loaded at the source and load side of the amplifier, respectively. By adjusting the bias and input power, the maximum efficiency and the corresponding collector bias and input power can be obtained. Finally, the improvement of amplifier efficiency and linearity is summarized. The results show that the maximum efficiency of the amplifier is about 40% when the third order intermodulation of the amplifier is set to? 45dBc. The experimental results also show that in order to achieve higher efficiency, the echo loss at the center frequency should be smaller when the third-order intermodulation requirement is satisfied.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN722

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