大功率条件下传输线无源互调技术研究

发布时间：2018-09-07 11:16

【摘要】：无源互调(Passive Inter Modulation)简称PIM,是由两个或多个频率在无源器件(或线性器件)中混合而产生的新的频率分量,广泛存在于大功率、多信道微波通信系统中。无源互调的产生与无源器件在大功率条件下激发的非线性息息相关,它的出现会在空中或系统内部产生一组无用并且影响系统正常工作的频谱。本文基于某大功率行波管放大器非线性频谱测试系统中的大功率采样装置,研究该采样装置中带状线的无源互调,有利于分析行波管放大器非线性测试结果。首先,描述了课题研究背景,介绍了国内外无源互调研究的发展状况,讨论了无源互调特性,分析了无源互调产生的内在机理,并且描述了工程中切实有效的减小无源互调的措施。其次,分析了经典的传输线非线性NTL(Nonlinear Transmission Line)模型,建立了传输线非线性电阻物理模型,对带状线中金属导体自热效应导致的非线性进行了理论分析、公式推导和数据仿真。讨论了无源互调测试方法,结合本文研究对象和实验条件,针对带状线弱无源互调效应,给出了对比测试的方法。该方法通过带状线采样器件、衰减器、耦合器三种信号采集方式,分别对放大器不同输出功率的谐波和三阶交调分量进行测试;改变放大器输出后级中低通滤波器和带状线采样器件的连接顺序,在不同功率条件下对二次谐波进行测试,横向对比测试结果,分析带状线的非线性效应。然后,仿真设计并制作了2~18GHz频段内至少一个波长周期的大功率带状线采样器件,包括同轴探针移动台、宽带带状线及带状线到APC-7过渡结构。对带状线反射系数实测结果相比于仿真的数据偏大,利用矢网的时域功能进行了误差定位和分析,为下一步改进提供了依据。最后,依据预先设计的测试方案,组装测试系统,完成不同功率条件下的谐波和三阶交调分量测试。测试结果表明,带状线在最大33dBm功率条件下,表现出弱非线性特性,符合理论分析结果。
[Abstract]:Passive Intermodulation (Passive Inter Modulation) is a new frequency component produced by mixing two or more frequencies in passive devices (or linear devices). It is widely used in high-power, multi-channel microwave communication systems. The generation of passive intermodulation is closely related to the nonlinearity excited by passive devices under high power conditions. Its appearance will produce a set of useless spectrum in the air or inside the system and affect the normal operation of the system. In this paper, based on the high power sampling device in a high power TWT amplifier nonlinear spectrum testing system, the passive intermodulation of strip lines in this sampling device is studied, which is helpful to analyze the nonlinear test results of TWT amplifier. Firstly, the research background is described, the development of passive Intermodulation at home and abroad is introduced, the characteristics of passive Intermodulation are discussed, and the inherent mechanism of passive Intermodulation is analyzed. The practical and effective measures to reduce passive intermodulation in engineering are also described. Secondly, the classical nonlinear NTL (Nonlinear Transmission Line) model of transmission line is analyzed, and the physical model of nonlinear resistance of transmission line is established. The theoretical analysis, formula derivation and data simulation of the nonlinearity caused by the self-heating effect of metal conductor in the strip line are carried out. The passive Intermodulation testing method is discussed. Combining with the research object and experimental conditions, a comparative test method is given for the weak passive Intermodulation effect of the strip line. In this method, the harmonic and third-order modulation components of different output power of amplifier are measured by three signal acquisition methods: strip line sampler, attenuator and coupler. By changing the connection sequence of the low pass filter and the band line sampling device, the second harmonic is measured under different power conditions. The results of transverse comparison are compared and the nonlinear effect of the strip line is analyzed. Then, a high-power band wire sampler with at least one wavelength period in the 2~18GHz band is designed and fabricated, including the coaxial probe moving station, the wideband band line and the transition structure from the band line to the APC-7. The measured results of the reflection coefficient of the strip line are larger than those of the simulation data. The error location and analysis are carried out by using the time-domain function of the vector network, which provides the basis for further improvement. Finally, according to the pre-designed test scheme, the test system is assembled and the harmonic and third-order intermodulation components are tested under different power conditions. The test results show that the strip lines show weak nonlinear characteristics under the condition of maximum 33dBm power, which is in accordance with the theoretical analysis results.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN811
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本文编号：2228101