Measurements taken with a Vector Network Analyzer (VNA) are often corrupted by the presence of 2-port networks such as cables or amplifiers between the VNA and device-under-test (DUT). These 2-port devices are an essential part of the signal path, but distort the desired measurements. These distortions are commonly removed by de-embedding the 2-port networks between the VNA and DUT. Herein we consider the case of a grain bin electromagnetic imaging system where the DUT (the grain bin) is connected to the VNA by a set of amplifiers, a switching matrix, and locally installed cables. Further, for cost savings, the VNA only measures the S21S_{21} and S11S_{11} scattering parameters. Applying traditional de-embedding techniques to such a system would require a full S-matrix measurement, as well as knowing full 2-port parameters of all system components between the VNA and DUT. As these grain imaging systems have cables cut to length on site and are located in remote locations, it is not possible to obtain full 2-port measurements of the networks between the VNA and the DUT. Herein, we present an algorithm for using de-embedding techniques on such a system that allows us to approximate the various network parameters needed, and show that these approximations allow us to de-embed the grain bin measurements. Experimental results from one bin show that de-embedding reduces the average S21S_{21} errors in magnitude to less than 0.5 dB, with average phase errors of less than 0.15 radians. The average magnitude errors are similar to the measurement error between two different VNAs. A second experiment on a grain bin where the authors did not have physical access, shows that de-embedding the signal improves the computational model of the signals (a key indicator for future imaging success).

中文翻译：

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粮仓电磁成像系统的有限信息信号去嵌入


使用矢量网络分析仪 (VNA) 进行的测量常常会因 VNA 和被测设备 (DUT) 之间存在的 2 端口网络（例如电缆或放大器）而受到破坏。这些 2 端口设备是信号路径的重要组成部分，但会扭曲所需的测量结果。这些失真通常可以通过去嵌入 VNA 和 DUT 之间的 2 端口网络来消除。在此，我们考虑粮仓电磁成像系统的情况，其中 DUT（粮仓）通过一组放大器、开关矩阵和本地安装的电缆连接到 VNA。此外，为了节省成本，VNA 仅测量 S21S_{21} 和 S11S_{11} 散射参数。将传统的去嵌入技术应用于此类系统需要完整的 S 矩阵测量，以及了解 VNA 和 DUT 之间所有系统组件的完整 2 端口参数。由于这些谷物成像系统的电缆在现场被切割成一定长度并且位于远程位置，因此不可能获得 VNA 和 DUT 之间网络的完整 2 端口测量。在此，我们提出了一种在此类系统上使用去嵌入技术的算法，该算法允许我们近似所需的各种网络参数，并表明这些近似允许我们去嵌入谷物仓测量值。一个箱的实验结果表明，去嵌入将平均 S21S_{21} 幅度误差降低到小于 0.5 dB，平均相位误差小于 0.15 弧度。平均幅度误差类似于两个不同 VNA 之间的测量误差。 在作者无法物理访问的粮仓上进行的第二个实验表明，去嵌入信号改善了信号的计算模型（未来成像成功的关键指标）。