ABSTRACT In this article, Frequency Modulated Thermal Wave Imaging (FMTWI) [1–6] is introduced for the first time for determining power distribution of electromagnetic waves on plane surfaces. The advantage with this technique is that we can extract multiple amplitude and phase images from a single run of experiment. The applied excitation signal in this technique is a frequency modulated chirp signal instead of a single frequency signal used in conventional lock-in infrared (IR) thermography [7–11]. The thermal images obtained using FMTWI can be used qualitatively, e.g., to detect field leakage near electromagnetic junctions and microstrip feed lines. As a practical demonstration of this technique, an example of 2 × 2 patch antenna array at 8 GHz is considered. First, amplitude images at various modulation frequencies are obtained. Next, signal to noise ratio (SNR) values at each frequency are calculated. It is seen that SNR is lower at higher frequencies. It is observed that at higher modulation frequencies, micro-strip lines feeding the individual patch antennas of the array, are not visible in amplitude images, while at lower frequencies they are clearly visible Mathematical modeling of the microwave absorption screen has also been carried out to show variations of incident, reflected, and transmitted powers as a function of screen surface impedance. It is also observed that the screen minimally perturbs the electromagnetic fields.

中文翻译：

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用于可视化平面上电磁波功率密度的调频热波成像

摘要 在本文中，调频热波成像 (FMTWI) [1-6] 首次被介绍用于确定平面上电磁波的功率分布。这种技术的优点是我们可以从一次实验中提取多个幅度和相位图像。该技术中应用的激励信号是调频啁啾信号，而不是传统锁定红外 (IR) 热成像中使用的单频信号 [7-11]。使用 FMTWI 获得的热图像可以定性地使用，例如，检测电磁结和微带馈线附近的场泄漏。作为该技术的实际演示，考虑了 8 GHz 下 2 × 2 贴片天线阵列的示例。首先，获得各种调制频率下的幅度图像。下一个，计算每个频率的信噪比 (SNR) 值。可以看出，SNR 在较高频率下较低。据观察，在较高调制频率下，馈送阵列的各个贴片天线的微带线在幅度图像中不可见，而在较低频率下，它们清晰可见 微波吸收屏的数学建模也已进行显示了作为屏幕表面阻抗函数的入射、反射和传输功率的变化。还观察到屏幕对电磁场的干扰最小。在振幅图像中不可见，而在较低频率下，它们清晰可见 微波吸收屏的数学建模也已进行，以显示作为屏幕表面阻抗函数的入射、反射和传输功率的变化。还观察到屏幕对电磁场的干扰最小。在振幅图像中不可见，而在较低频率下，它们清晰可见 微波吸收屏的数学建模也已进行，以显示作为屏幕表面阻抗函数的入射、反射和传输功率的变化。还观察到屏幕对电磁场的干扰最小。