长波长阵列天线与前端电子设备的散射参数测量
Scattering Parameter Measurements of the Long Wavelength Array Antenna and Front End Electronics
AI总结：
本研究利用两端口矢量网络分析仪首次完成长波长阵列天线及前端电子设备的全套散射参数直接测量，推导了阻抗失配因子，测量了跨天线耦合，并验证了相关校正对消除仪器效应的作用。
摘要：
我们介绍了近期利用两端口矢量网络分析仪（VNA），对长波长阵列（Long Wavelength Array，LWA）所用天线及配套前端电子设备（front end electronics，FEEs）的全套散射参数开展的测量工作。天线的完整散射参数测量不仅能得到各极化的反射系数S11和S22，还能得到极化间的耦合系数S12和S21。这些参数此前仅通过仿真建模，此前尚未获得直接测量结果。我们利用测量结果推导了随频率变化的阻抗失配因子（impedance mismatch factor，IMF），该因子代表因天线阻抗与FEE阻抗失配而未被反射、成功通过天线-FEE界面的功率占比。我们还展示了双天线实验的结果：每根天线分别连接至VNA的独立端口，从而能够测量所有四种极化组合下的跨天线耦合。最后，我们将新测得的IMF和FEE前向增益校正应用于LWA数据，以研究其消除仪器效应的效果。
英文摘要：
We present recent 2-port vector network analyzer (VNA) measurements of the complete set of scattering parameters for the antenna used within the Long Wavelength Array (LWA) and the associated front end electronics (FEEs). Full scattering parameter measurements of the antenna yield not only the reflection coefficient for each polarization, S11 and S22, but also the coupling between polarizations, S12 and S21. These had been previously modeled using simulations, but direct measurements had not been obtained until now. The measurements are used to derive a frequency dependent impedance mismatch factor (IMF) which represents the fraction of power that is passed through the antenna-FEE interface and not reflected due to a mismatch between the impedance of the antenna and the impedance of the FEE. We also present results from a two antenna experiment where each antenna is hooked up to a separate port on the VNA. This allows for cross-antenna coupling to be measured for all four possible polarization combinations. Finally, we apply the newly measured IMF and FEE forward gain corrections to LWA data to investigate how well they remove instrumental effects.
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