【摘要】：無源互調(diào)(Passive Inter Modulation)簡稱PIM,是由兩個或多個頻率在無源器件(或線性器件)中混合而產(chǎn)生的新的頻率分量,廣泛存在于大功率、多信道微波通信系統(tǒng)中。無源互調(diào)的產(chǎn)生與無源器件在大功率條件下激發(fā)的非線性息息相關,它的出現(xiàn)會在空中或系統(tǒng)內(nèi)部產(chǎn)生一組無用并且影響系統(tǒng)正常工作的頻譜。本文基于某大功率行波管放大器非線性頻譜測試系統(tǒng)中的大功率采樣裝置,研究該采樣裝置中帶狀線的無源互調(diào),有利于分析行波管放大器非線性測試結果。首先,描述了課題研究背景,介紹了國內(nèi)外無源互調(diào)研究的發(fā)展狀況,討論了無源互調(diào)特性,分析了無源互調(diào)產(chǎn)生的內(nèi)在機理,并且描述了工程中切實有效的減小無源互調(diào)的措施。其次,分析了經(jīng)典的傳輸線非線性NTL(Nonlinear Transmission Line)模型,建立了傳輸線非線性電阻物理模型,對帶狀線中金屬導體自熱效應導致的非線性進行了理論分析、公式推導和數(shù)據(jù)仿真。討論了無源互調(diào)測試方法,結合本文研究對象和實驗條件,針對帶狀線弱無源互調(diào)效應,給出了對比測試的方法。該方法通過帶狀線采樣器件、衰減器、耦合器三種信號采集方式,分別對放大器不同輸出功率的諧波和三階交調(diào)分量進行測試;改變放大器輸出后級中低通濾波器和帶狀線采樣器件的連接順序,在不同功率條件下對二次諧波進行測試,橫向對比測試結果,分析帶狀線的非線性效應。然后,仿真設計并制作了2~18GHz頻段內(nèi)至少一個波長周期的大功率帶狀線采樣器件,包括同軸探針移動臺、寬帶帶狀線及帶狀線到APC-7過渡結構。對帶狀線反射系數(shù)實測結果相比于仿真的數(shù)據(jù)偏大,利用矢網(wǎng)的時域功能進行了誤差定位和分析,為下一步改進提供了依據(jù)。最后,依據(jù)預先設計的測試方案,組裝測試系統(tǒng),完成不同功率條件下的諧波和三階交調(diào)分量測試。測試結果表明,帶狀線在最大33dBm功率條件下,表現(xiàn)出弱非線性特性,符合理論分析結果。
[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.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN811
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本文編號：2228101